Paper •
OPEN ACCESS
2025, 4(2)
DOI: 10.1088/2752-5724/adb50a
Abstract：
The CoCrMo alloys fabricated by the laser powder bed fusion (LPBF) exhibit significant anisotropy due to the characteristics of layer-by-layer manufacturing. This study investigated the microstructural evolution and mechanical properties of CoCrMo alloys in both as-printed and heat-treated states. The results demonstrated that the elongation was 19.1% in the tensile direction parallel to the building direction, compared to only 9.3% in the perpendicular direction, showing a difference of over 100%. After solution heat treatment at 1150 ℃ for 1 h followed by annealing heat treatment at 450 ℃ for 0.5 h, the ultimate tensile strength (UTS) and elongation nearly equalized, reaching 906.1 MPa, 20.2% and 879.2 MPa, 17.9%, respectively. Further characterization indicated that the anisotropy was mainly caused by grain morphology. Solution treatment-induced recrystallization refined coarse columnar grains into equiaxed grains that accommodated orientation-related stresses, which tentatively achieves microstructural and mechanical homogeneity. Subsequent low-temperature annealing broke the trade-off between the strength and ductility while further promoting the isotropy. At this stage, the mechanical properties were strengthened by the synergistic interaction of nanoscale annealing twins and martensitic laths. This study provided valuable insights for optimizing the isotropic behavior in LPBF-fabricated CoCrMo alloys.
The CoCrMo alloys fabricated by the laser powder bed fusion (LPBF) exhibit significant anisotropy due to the characteristics of layer-by-layer manufacturing. This study investigated the microstructural evolution and mechanical properties of CoCrMo alloys in both as-printed and heat-treated states. The results demonstrated that the elongation was 19.1% in the tensile direction parallel to the building direction, compared to only 9.3% in the perpendicular direction, showing a difference of over 100%. After solution heat treatment at 1150 ℃ for 1 h followed by annealing heat treatment at 450 ℃ for 0.5 h, the ultimate tensile strength (UTS) and elongation nearly equalized, reaching 906.1 MPa, 20.2% and 879.2 MPa, 17.9%, respectively. Further characterization indicated that the anisotropy was mainly caused by grain morphology. Solution treatment-induced recrystallization refined coarse columnar grains into equiaxed grains that accommodated orientation-related stresses, which tentatively achieves microstructural and mechanical homogeneity. Subsequent low-temperature annealing broke the trade-off between the strength and ductility while further promoting the isotropy. At this stage, the mechanical properties were strengthened by the synergistic interaction of nanoscale annealing twins and martensitic laths. This study provided valuable insights for optimizing the isotropic behavior in LPBF-fabricated CoCrMo alloys.
Paper •
OPEN ACCESS
2025, 4(2)
DOI: 10.1088/2752-5724/ad9e08
Abstract：
Spinel LiMn2O4 (LMO) is deemed to be a promising cathode material for commercial lithium-ion batteries (LIBs) in prospect of its cost-effectiveness, nontoxicity, fabulous rate capability, and high energy density. Nevertheless, the LMO is inevitably confronted with sluggish diffusion kinetics and drastic capacity degradation triggered by multiple issues, including Jahn–Teller distortion, Mn dissolution, and structural attenuation. Thereinto, a metal-organic framework (MOF) chemistry engineering for hierarchical micro-/nano-structural F, O-dual-doped carbon embedded oxygen vacancy enriched LiMn2O4 cathode (OV-LMO@FOC) is proposed for longevous LIBs. Bestowed by experimental and theoretical implementations, systematic investigations of OV-LMO@FOC endow that the meticulous integration of F, O-dual-doped carbon and oxygen vacancy in LMO-based cathode reconfigures the electronic structure, boosts electronic conductivity, expedites diffusion capability, facilitates energetically preferable Li+ adsorption, and suppresses Mn dissolution in the electrolyte, consequently achieving fabulous long-term cycling stability. As expected, the OV-LMO@FOC behaves with compelling electrochemical performance with prosperous reversible capacity (130.2 mAh g-1 at 0.2 C upon 200 cycles), exceptional rate capacity (93.7 mAh g-1 even at 20 C), and pronounced long-term cyclability (112.5 mAh g-1 after 1200 cycles with 77.6% capacity retention at 1 C). Even at the ultrahigh current density of 5 C, the OV-LMO@FOC bears a brilliant capacity of 96.9 mAh g-1 upon 1000 cycles with an extraordinary capacity retention of 90.7%, and maintains a discharge capacity of 70.9 mAh g-1 upon 4000 cycles. This work envisions the MOF-chemistry in surface modification and electronic modulation engineering of high-performance cathode materials towards industrialization in automotive market.
Spinel LiMn2O4 (LMO) is deemed to be a promising cathode material for commercial lithium-ion batteries (LIBs) in prospect of its cost-effectiveness, nontoxicity, fabulous rate capability, and high energy density. Nevertheless, the LMO is inevitably confronted with sluggish diffusion kinetics and drastic capacity degradation triggered by multiple issues, including Jahn–Teller distortion, Mn dissolution, and structural attenuation. Thereinto, a metal-organic framework (MOF) chemistry engineering for hierarchical micro-/nano-structural F, O-dual-doped carbon embedded oxygen vacancy enriched LiMn2O4 cathode (OV-LMO@FOC) is proposed for longevous LIBs. Bestowed by experimental and theoretical implementations, systematic investigations of OV-LMO@FOC endow that the meticulous integration of F, O-dual-doped carbon and oxygen vacancy in LMO-based cathode reconfigures the electronic structure, boosts electronic conductivity, expedites diffusion capability, facilitates energetically preferable Li+ adsorption, and suppresses Mn dissolution in the electrolyte, consequently achieving fabulous long-term cycling stability. As expected, the OV-LMO@FOC behaves with compelling electrochemical performance with prosperous reversible capacity (130.2 mAh g-1 at 0.2 C upon 200 cycles), exceptional rate capacity (93.7 mAh g-1 even at 20 C), and pronounced long-term cyclability (112.5 mAh g-1 after 1200 cycles with 77.6% capacity retention at 1 C). Even at the ultrahigh current density of 5 C, the OV-LMO@FOC bears a brilliant capacity of 96.9 mAh g-1 upon 1000 cycles with an extraordinary capacity retention of 90.7%, and maintains a discharge capacity of 70.9 mAh g-1 upon 4000 cycles. This work envisions the MOF-chemistry in surface modification and electronic modulation engineering of high-performance cathode materials towards industrialization in automotive market.
Paper •
OPEN ACCESS
2025, 4(2)
DOI: 10.1088/2752-5724/adcbc7
Abstract：
As environmentally friendly compounds, lead-free perovskites have gained widespread application in the fabrication of solar cells in recent years. Among these, rudorffites such as AgBiI4 are considered as promising candidates owing to their favorable band structure and exceptional stability. However, the formation of Ag vacancies during the synthetic process poses a significant challenge, severely hindering carrier transport properties. To address this issue, we propose an Ag management strategy utilizing aliphatic ammonium, which serves multiple purposes: it enhances the solubility of AgI in the precursor solution, mitigates phase separation caused by stoichiometric mismatches during AgBiI4 film formation, and effectively passivates Ag defects. The butylamine hydroiodide modified AgBiI4 solar cells achieved a champion power conversion efficiency of 1.97%, representing a 26% enhancement over the control device.
As environmentally friendly compounds, lead-free perovskites have gained widespread application in the fabrication of solar cells in recent years. Among these, rudorffites such as AgBiI4 are considered as promising candidates owing to their favorable band structure and exceptional stability. However, the formation of Ag vacancies during the synthetic process poses a significant challenge, severely hindering carrier transport properties. To address this issue, we propose an Ag management strategy utilizing aliphatic ammonium, which serves multiple purposes: it enhances the solubility of AgI in the precursor solution, mitigates phase separation caused by stoichiometric mismatches during AgBiI4 film formation, and effectively passivates Ag defects. The butylamine hydroiodide modified AgBiI4 solar cells achieved a champion power conversion efficiency of 1.97%, representing a 26% enhancement over the control device.
Letter •
OPEN ACCESS
2025, 4(1)
DOI: 10.1088/2752-5724/ad9bce
Abstract：
Intermediate temperature brittleness in alloys characterized as brittle fracture along grain boundaries (GBs) with less than 5% elongation to fracture (EF) at 600 ℃–900 ℃ diminishes work hardening, leads to sudden failure under load, and thus threatens the reliability during the service of alloys. Here, in a precipitation-strengthened CoNiCr alloy, through two grain boundary engineering (GBE) methods, fiber-like γ' or topologically close-packed phase is introduced at GBs, which effectively optimizes the grain structure and prevents GB cracking under tensile stresses. GBEs not only alter the deformation mode from dislocation pairs to stacking faults and/or deformation twins, but also transform the failure mode from GB cracking to GB void formation, because the crack propagation along GBs is constrained by GB bridging phases. Consequently, our GBE approach enhances tensile EF from ∼1% to ∼10% and concurrently increases the yield strength from ∼650 to ∼770–850 MPa at 800 ℃. A cavity growth model is then developed to illustrate the role of these bridging phases in GBs for ductility improvement. The fundamental philosophy utilized in the present work might be also applicable to other metallic materials.
Intermediate temperature brittleness in alloys characterized as brittle fracture along grain boundaries (GBs) with less than 5% elongation to fracture (EF) at 600 ℃–900 ℃ diminishes work hardening, leads to sudden failure under load, and thus threatens the reliability during the service of alloys. Here, in a precipitation-strengthened CoNiCr alloy, through two grain boundary engineering (GBE) methods, fiber-like γ' or topologically close-packed phase is introduced at GBs, which effectively optimizes the grain structure and prevents GB cracking under tensile stresses. GBEs not only alter the deformation mode from dislocation pairs to stacking faults and/or deformation twins, but also transform the failure mode from GB cracking to GB void formation, because the crack propagation along GBs is constrained by GB bridging phases. Consequently, our GBE approach enhances tensile EF from ∼1% to ∼10% and concurrently increases the yield strength from ∼650 to ∼770–850 MPa at 800 ℃. A cavity growth model is then developed to illustrate the role of these bridging phases in GBs for ductility improvement. The fundamental philosophy utilized in the present work might be also applicable to other metallic materials.
Topical Review •
OPEN ACCESS
2025, 4(1)
DOI: 10.1088/2752-5724/ad8cf2
Abstract：
The assembly of monolayer transition metal dichalcogenides (TMDs) in van der Waals heterostructures yields the formation of spatially separated interlayer excitons (IXs) with large binding energies, long lifetimes, permanent dipole moments and valley-contrasting physics, providing a compelling platform for investigating and engineering spatiotemporal IX propagation with highly tunable dynamics. Further twisting the stacked TMD monolayers can create long-term periodic moiré patterns with spatially modified band structures and varying moiré potentials, featuring tailored traps that can induce strong correlations with density–dependent phase transitions to modulate the exciton transport. The rich exciton landscapes in TMD heterostructures, combined with advancements in valleytronics and twistronics, hold great promise for exploring exciton-integrated circuits base on manipulation of exciton diffusion and transport. In this Review, we provide a comprehensive overview of recent progress in understanding IXs and moiré excitons, with a specific focus on emerging exciton diffusion and transport in TMD heterostructures. We put emphasis on spatial manipulation of exciton flux through various methods, encompassing exciton density, dielectric environment, electric field and structure engineering, for precise control. This ability to manipulate exciton diffusion opens up new possibilities for interconverting optical communication and signal processing, paving the way for exciting applications in high-performance optoelectronics, such as excitonic devices, valleytronic transistors and photodetectors. We finally conclude this review by outlining perspectives and challenges in harnessing IX currents for next-generation optoelectronic applications.
The assembly of monolayer transition metal dichalcogenides (TMDs) in van der Waals heterostructures yields the formation of spatially separated interlayer excitons (IXs) with large binding energies, long lifetimes, permanent dipole moments and valley-contrasting physics, providing a compelling platform for investigating and engineering spatiotemporal IX propagation with highly tunable dynamics. Further twisting the stacked TMD monolayers can create long-term periodic moiré patterns with spatially modified band structures and varying moiré potentials, featuring tailored traps that can induce strong correlations with density–dependent phase transitions to modulate the exciton transport. The rich exciton landscapes in TMD heterostructures, combined with advancements in valleytronics and twistronics, hold great promise for exploring exciton-integrated circuits base on manipulation of exciton diffusion and transport. In this Review, we provide a comprehensive overview of recent progress in understanding IXs and moiré excitons, with a specific focus on emerging exciton diffusion and transport in TMD heterostructures. We put emphasis on spatial manipulation of exciton flux through various methods, encompassing exciton density, dielectric environment, electric field and structure engineering, for precise control. This ability to manipulate exciton diffusion opens up new possibilities for interconverting optical communication and signal processing, paving the way for exciting applications in high-performance optoelectronics, such as excitonic devices, valleytronic transistors and photodetectors. We finally conclude this review by outlining perspectives and challenges in harnessing IX currents for next-generation optoelectronic applications.
Paper •
OPEN ACCESS
2025, 4(1)
DOI: 10.1088/2752-5724/ada0cc
Abstract：
Polymer-based composite solid electrolytes (PCSEs) are increasingly studied in all-solid-state lithium-metal batteries (ASSLMBs) due to the combined advantages of better flexibility of polymer and higher ion conductivity of ceramic electrolytes. However, most reported PCSEs are overly thick, increasing internal resistances. Besides, the poor stability at the Li metal–electrolyte interfaces often leads to severe lithium dendrite formation and reduced cycling stability. Here, we fabricate an ultrathin PCSE with a thickness of 12.4 µm, incorporating polyacrylonitrile (PAN) nanofibers as the structural matrix, and a filler with polyethylene oxide and Li6.5La3Zr1.5Ta0.5O12 (LLZTO). Due to the formation of the LiCN layer on the surface of the lithium metal and the Li-ion transport pathways induced by the dehydrocyanation reaction at the LLZTO/PAN interfaces, the PCSE exhibits a high critical current density of 1.8 mA cm-2 and a low energy barrier of 0.278 eV for Li-ion transfer, accommodating the fast Li-ion migration to avoid Li-dendrite growth. In addition, the stable nitrile groups and the dehydrocyanation reaction ensure the electrochemical stability of the PCSE with a high oxidation voltage of 5.5 V and an exceptional cycling stability (2100 h) in Li||PCSE||Li symmetric cells. Additionally, the Li||PCSE||LiFePO4 full cells demonstrate a high volumetric energy density of 338.3 Wh L-1 at 0.1 C and a robust stability over 100 cycles at 0.5 C. The study offers a new approach for fabricating ultrathin PCSEs and provides insights into the mechanisms of dendrite-free formation, guiding the development of high-performance PCSEs for ASSLMBs.
Polymer-based composite solid electrolytes (PCSEs) are increasingly studied in all-solid-state lithium-metal batteries (ASSLMBs) due to the combined advantages of better flexibility of polymer and higher ion conductivity of ceramic electrolytes. However, most reported PCSEs are overly thick, increasing internal resistances. Besides, the poor stability at the Li metal–electrolyte interfaces often leads to severe lithium dendrite formation and reduced cycling stability. Here, we fabricate an ultrathin PCSE with a thickness of 12.4 µm, incorporating polyacrylonitrile (PAN) nanofibers as the structural matrix, and a filler with polyethylene oxide and Li6.5La3Zr1.5Ta0.5O12 (LLZTO). Due to the formation of the LiCN layer on the surface of the lithium metal and the Li-ion transport pathways induced by the dehydrocyanation reaction at the LLZTO/PAN interfaces, the PCSE exhibits a high critical current density of 1.8 mA cm-2 and a low energy barrier of 0.278 eV for Li-ion transfer, accommodating the fast Li-ion migration to avoid Li-dendrite growth. In addition, the stable nitrile groups and the dehydrocyanation reaction ensure the electrochemical stability of the PCSE with a high oxidation voltage of 5.5 V and an exceptional cycling stability (2100 h) in Li||PCSE||Li symmetric cells. Additionally, the Li||PCSE||LiFePO4 full cells demonstrate a high volumetric energy density of 338.3 Wh L-1 at 0.1 C and a robust stability over 100 cycles at 0.5 C. The study offers a new approach for fabricating ultrathin PCSEs and provides insights into the mechanisms of dendrite-free formation, guiding the development of high-performance PCSEs for ASSLMBs.
Paper •
OPEN ACCESS
Additive manufacturing of multiscale NiFeMn multi-principal element alloys with tailored composition
2024, 3(4)
DOI: 10.1088/2752-5724/ad89e1
Abstract：
Nanostructured multi-principal element alloys (MPEAs) have been explored as next-generation engineering materials due to unique mechanical and functional properties which have significant advantages over traditional dilute alloys. However, the practical applications of nanostructured MPEAs are still limited due to the lack of scalable processing approaches to prepare a large quantity of nanostructured MPEAs, as well as lack of an efficient pathway for high-throughput discovery of better functional nanostructured MPEAs within their vast compositional space. Here we tackle these challenges by presenting an integrated approach by combining direct-ink-writing-based additive manufacturing, solid-state sintering, and chemical dealloying to manufacture hierarchically porous MPEAs. The hierarchical structure is comprised of macro- and micro-scale pores introduced via extrusion printing and polymer decomposition during sintering, as well as nanoscale pores formed via chemical dealloying. The macro- and micro-scale pores allow efficient dealloying of a large mass of material as the diffusion length that the corroding medium must penetrate remains at the scale of the ligaments formed after sintering (∼10 μm), despite the large volume of the 3D-printed samples. In addition, this integrated approach enables versatile control of the alloy composition via precisely tuning the ratio of elemental powders in the starting ink, thus offering a pathway for high-throughput discovery of novel functional MPEAs. As a case study, multiscale macro/micro/nanoporous NiFeMn MPEAs with three different compositions were investigated as catalysts to reduce the overpotential of oxygen evolution reaction (OER), where NiFeMn-based electrocatalysts display composition-dependent performance such that the overpotential measured at a current of 0.5 A g-1 for OER increases in the order of Ni58Fe29Mn13 Ni64Fe26Mn10 < Ni76Fe18Mn6. This introduced manufacturing process offers new opportunities for scalable fabrication and rapid screening of nanostructured multi-component complex alloys.
Paper •
OPEN ACCESS
2024, 3(4)
DOI: 10.1088/2752-5724/ad89e2
Abstract：
Laser powder bed fusion is a mainstream additive manufacturing technology widely used to manufacture complex parts in prominent sectors, including aerospace, biomedical, and automotive industries. However, during the printing process, the presence of an unstable vapor depression can lead to a type of defect called keyhole porosity, which is detrimental to the part quality. In this study, we developed an effective approach to locally detect the generation of keyhole pores during the printing process by leveraging machine learning and a suite of optical and acoustic sensors. Simultaneous synchrotron x-ray imaging allows the direct visualization of pore generation events inside the sample, offering high-fidelity ground truth. A neural network model adopting SqueezeNet architecture using single-sensor data was developed to evaluate the fidelity of each sensor for capturing keyhole pore generation events. Our comparative study shows that the near infrared images gave the highest prediction accuracy, followed by 100 kHz and 20 kHz microphones, and the photodiode sensitive to processing laser wavelength had the lowest accuracy. Using a single sensor, over 90% prediction accuracy can be achieved with a temporal resolution as short as 0.1 ms. A data fusion scheme was also developed with features extracted using SqueezeNet neural network architecture and classification using different machine learning algorithms. Our work demonstrates the correlation between the characteristic optical and acoustic emissions and the keyhole oscillation behavior, and thereby provides strong physics support for the machine learning approach.
Accepted Manuscript •
OPEN ACCESS
Accepted Manuscript, Available online 2025-04-24 17:35,
DOI: 10.1088/2752-5724/adcfb6
Abstract：
Metallic glasses that mainly make up of metallic elements are new family member of glassy materials. This new kind of glass combines the characters of liquids and solids, glasses and metals, making it fascinating to both scientists and industrialists. With the discovery of more and more systems, metallic glass is becoming one of the most active research field in metallic materials, and some concepts and technology derived from metallic glasses also facilitate the development of other materials from quasi-crystals to high entropy alloys. Metallic glasses have now been successfully used in aerospace, robotics, medicine and consumer electronics etc., and the real applications of metallic glasses are still growing. On the other hand, the diverse properties and the unique structural of the metallic glasses render them ideal models to study major open issues including structural model of disordered materials, glass transition, collective motion and energy landscape etc. However, the understanding the emerging properties and phenomena of metallic glasses still poses enormous challenges, which have stimulated a wealth of new experimental approaches, the synthesis of new systems with tailored properties, novel experimental techniques and theoretical and numerical methods. In this Roadmap, we try to provide a broad overview of recent and possible future activities in the metallic glass field, and present a roadmap to future development and applications of metallic glasses by gathering contributions with different backgrounds, illustrating the major challenges and discussing the latest technology and strategy to tackle these challenges with experts covering various developments and challenges in general concepts, synthesis and characterisation, and simulation and theoretical methods.
Accepted Manuscript •
OPEN ACCESS
Accepted Manuscript, Available online 2025-05-06 14:19,
DOI: 10.1088/2752-5724/add415
Abstract：
Developing nanoporous high-entropy metallic glass (HEMG) with a high specific surface area presents a promising approach to develop a cost-effective and efficient catalyst, which utilize the synergistic effect of its multi-component composition and the adjustable atomic environment of its disordered structure. However, the glassy structure invariably gets erased due to the inevitable crystallization during the nanoporous construction procedure through dealloying. Here, an innovative HEMG with an endogenetic nano-scale phase-separated structure is specially designed to maintain a fully glassy state throughout the nanoporous construction procedure. Consequently, an amorphous/crystalline heterostructure (ACH)—nanocrystal flakes embedded in amorphous ligaments—is intentionally constructed, which exhibits significant lattice distortion at amorphous/crystalline interfaces, resulting in high density of active sites. The ACH facilitates intermediate adsorption by promoting directional charge transfer between amorphous and crystalline phases and improves product desorption through downshifting the d-band center. This results in remarkable electrolysis performance, requiring only a 1.53 V potential to achieve a current density of 10 mA cm-2 for overall water-splitting in an alkaline electrolyte, surpassing that of commercial Pt/C || IrO2 catalysts of 1.62 V. This research pioneers strategies to refine the composition, atomic structure, and electron characteristics of HEMG, unlocking new functional applications.
Developing nanoporous high-entropy metallic glass (HEMG) with a high specific surface area presents a promising approach to develop a cost-effective and efficient catalyst, which utilize the synergistic effect of its multi-component composition and the adjustable atomic environment of its disordered structure. However, the glassy structure invariably gets erased due to the inevitable crystallization during the nanoporous construction procedure through dealloying. Here, an innovative HEMG with an endogenetic nano-scale phase-separated structure is specially designed to maintain a fully glassy state throughout the nanoporous construction procedure. Consequently, an amorphous/crystalline heterostructure (ACH)—nanocrystal flakes embedded in amorphous ligaments—is intentionally constructed, which exhibits significant lattice distortion at amorphous/crystalline interfaces, resulting in high density of active sites. The ACH facilitates intermediate adsorption by promoting directional charge transfer between amorphous and crystalline phases and improves product desorption through downshifting the d-band center. This results in remarkable electrolysis performance, requiring only a 1.53 V potential to achieve a current density of 10 mA cm-2 for overall water-splitting in an alkaline electrolyte, surpassing that of commercial Pt/C || IrO2 catalysts of 1.62 V. This research pioneers strategies to refine the composition, atomic structure, and electron characteristics of HEMG, unlocking new functional applications.
Accepted Manuscript •
OPEN ACCESS
Accepted Manuscript, Available online 2025-05-10 16:17,
DOI: 10.1088/2752-5724/add60e
Abstract：
The electrocatalytic urea oxidation reaction (UOR) is a promising strategy for addressing both environmental remediation and energy conversion challenges. Recently, heterojunction catalysts have gained significant attention due to their enhanced catalytic activity and stability. This review provides a comprehensive analysis of recent advancements in heterojunction catalysts for UOR. We begin by outlining the fundamental principles of UOR and key catalyst evaluation parameters. Next, we discuss the unique features of heterojunction catalysts, highlighting their structural and electronic advantages. The applications of various heterojunction architectures—including those based on transition metals, alloys, metal (hydro)oxides, chalcogenides, pnictides, and metal-organic frameworks (MOFs)—are then examined in detail. A particular focus is placed on structure–performance relationships and rational design strategies to optimize catalytic efficiency. This review offers valuable insights into the development of next-generation heterojunction catalysts for efficient and sustainable UOR applications.
Accepted Manuscript •
OPEN ACCESS
Accepted Manuscript, Available online 2025-05-16 08:54,
DOI: 10.1088/2752-5724/add7f3
Abstract：
During the downconversion process, a high-energy photon undergoes conversion into several low-energy photons, leading to enhanced luminous efficiency in both photoluminescent and electroluminescent devices. This phenomenon has been applied in various fields, including solar cells, plasma display panels, and green lighting technologies such as mercury-free fluorescent lamps. However, the concept of downconversion (quantum cutting) has not been fully explored in the context of mechanoluminescent materials. In this study, we successfully synthesized a heterojunction of CaF2/CaZnOS exhibiting efficient downconversion mechanoluminescence (ML) properties. By controlling the CaF2 to CaZnOS ratio and incorporating Tb3+ doping, we obtained a highly effective heterojunction structure that significantly enhanced ML. Moreover, we extended this material to several commonly utilized downconversion ion-doping combinations, achieving enhanced ML for Tb3+, Pr3+, and Yb3+ single ions. For the first time, we demonstrate the downconversion (quantum cutting) ML of Tb3+–Yb3+ and Pr3+–Yb3+ pairs within heterojunction microstructures. This study presents the design and synthesis of a novel heterojunction material capable of realizing downconversion ML, which holds promise for future applications in diverse fields.
During the downconversion process, a high-energy photon undergoes conversion into several low-energy photons, leading to enhanced luminous efficiency in both photoluminescent and electroluminescent devices. This phenomenon has been applied in various fields, including solar cells, plasma display panels, and green lighting technologies such as mercury-free fluorescent lamps. However, the concept of downconversion (quantum cutting) has not been fully explored in the context of mechanoluminescent materials. In this study, we successfully synthesized a heterojunction of CaF2/CaZnOS exhibiting efficient downconversion mechanoluminescence (ML) properties. By controlling the CaF2 to CaZnOS ratio and incorporating Tb3+ doping, we obtained a highly effective heterojunction structure that significantly enhanced ML. Moreover, we extended this material to several commonly utilized downconversion ion-doping combinations, achieving enhanced ML for Tb3+, Pr3+, and Yb3+ single ions. For the first time, we demonstrate the downconversion (quantum cutting) ML of Tb3+–Yb3+ and Pr3+–Yb3+ pairs within heterojunction microstructures. This study presents the design and synthesis of a novel heterojunction material capable of realizing downconversion ML, which holds promise for future applications in diverse fields.
Accepted Manuscript •
OPEN ACCESS
Accepted Manuscript, Available online 2025-05-20 17:59,
DOI: 10.1088/2752-5724/adda68
Abstract：
Multiple strategies and technological pathways exist in developing new advanced high strength steels (AHSSs). For plain carbon steels, carbon partitioning has been utilized to generate a mixture of ferrite/martensite and retained austenite, whereas higher carbon content will stabilize austenite phase. The austenite can be metastable, which can trigger phase transition under stress, so called phase-transformation-induced plasticity (TRIP). For highly alloyed steels with Ni, Al, Ti or other elements, precipitates of the body-centered cubic (BCC), hexagonal close-packed (HCP), L21, L12 types can form during aging/partitioning. L12 phase shows exceptional deformation capability because itself can sustain significant plastic deformation. Motivated by these two design strategies, this work started from a Fe-Ni alloy by added with appropriate amounts of Al, Ti, and C to obtain a series of Fe-Ni-Al-Ti-C steels by melting, cold rolling and a simple heat treatment (recrystallization and aging/partitioning) history. Microstructural observation and mechanical property testing reveal that the Fe-Ni-Al-Ti-C steels successfully achieves: (1) nanosized and densely populated L12 precipitates in both ferrite and austenite phases, (2) enhanced stability of austenitic phase with TRIP capability, (3) ultrafine-grained microstructure due to precipitate-retarded ferrite grain growth, and (4) extra dislocation storage of precipitate-cutting dislocation loops. The synergy of all these factors results into tensile strengths of 1.2-1.8 GPa and uniform ductility of 10-30%, which is comparable to twining-induced plasticity steels.
Multiple strategies and technological pathways exist in developing new advanced high strength steels (AHSSs). For plain carbon steels, carbon partitioning has been utilized to generate a mixture of ferrite/martensite and retained austenite, whereas higher carbon content will stabilize austenite phase. The austenite can be metastable, which can trigger phase transition under stress, so called phase-transformation-induced plasticity (TRIP). For highly alloyed steels with Ni, Al, Ti or other elements, precipitates of the body-centered cubic (BCC), hexagonal close-packed (HCP), L21, L12 types can form during aging/partitioning. L12 phase shows exceptional deformation capability because itself can sustain significant plastic deformation. Motivated by these two design strategies, this work started from a Fe-Ni alloy by added with appropriate amounts of Al, Ti, and C to obtain a series of Fe-Ni-Al-Ti-C steels by melting, cold rolling and a simple heat treatment (recrystallization and aging/partitioning) history. Microstructural observation and mechanical property testing reveal that the Fe-Ni-Al-Ti-C steels successfully achieves: (1) nanosized and densely populated L12 precipitates in both ferrite and austenite phases, (2) enhanced stability of austenitic phase with TRIP capability, (3) ultrafine-grained microstructure due to precipitate-retarded ferrite grain growth, and (4) extra dislocation storage of precipitate-cutting dislocation loops. The synergy of all these factors results into tensile strengths of 1.2-1.8 GPa and uniform ductility of 10-30%, which is comparable to twining-induced plasticity steels.
Paper •
OPEN ACCESS
2022, 1(3)
DOI: 10.1088/2752-5724/ac74af
Abstract：
Helium-3 (3He) is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy. It is thought that the lunar regolith contains large amounts of helium, but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions. Here, we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission. The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas. The reserves in bubbles do not require heating to high temperatures to be extracted. Mechanical methods at ambient temperatures can easily break the bubbles. Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.
Helium-3 (3He) is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy. It is thought that the lunar regolith contains large amounts of helium, but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions. Here, we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission. The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas. The reserves in bubbles do not require heating to high temperatures to be extracted. Mechanical methods at ambient temperatures can easily break the bubbles. Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.
Topical Review •
OPEN ACCESS
2023, 2(1)
DOI: 10.1088/2752-5724/acbb5a
Abstract：
Charge-transporting layers (CTLs) are important in determining the performance and stability of perovskite solar cells (PSCs). Recently, there has been considerable use of self-assembled monolayers (SAMs) as charge-selective contacts, especially for hole-selective SAMs in inverted PSCs as well as perovskite involving tandem solar cells. The SAM-based charge-selective contact shows many advantages over traditional thin-film organic/inorganic CTLs, including reduced cost, low optical and electric loss, conformal coating on a rough substrate, simple deposition on a large-area substrate and easy modulation of energy levels, molecular dipoles and surface properties. The incorporation of various hole-selective SAMs has resulted in high-efficiency single junction and tandem solar cells. This topical review summarizes both the advantages and challenges of SAM-based charge-selective contacts, and discusses the potential direction for future studies.
Charge-transporting layers (CTLs) are important in determining the performance and stability of perovskite solar cells (PSCs). Recently, there has been considerable use of self-assembled monolayers (SAMs) as charge-selective contacts, especially for hole-selective SAMs in inverted PSCs as well as perovskite involving tandem solar cells. The SAM-based charge-selective contact shows many advantages over traditional thin-film organic/inorganic CTLs, including reduced cost, low optical and electric loss, conformal coating on a rough substrate, simple deposition on a large-area substrate and easy modulation of energy levels, molecular dipoles and surface properties. The incorporation of various hole-selective SAMs has resulted in high-efficiency single junction and tandem solar cells. This topical review summarizes both the advantages and challenges of SAM-based charge-selective contacts, and discusses the potential direction for future studies.
Topical Review •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac427c
Abstract：
In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understanding solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense SSBs.
In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understanding solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense SSBs.
Perspective •
OPEN ACCESS
2023, 2(1)
DOI: 10.1088/2752-5724/aca703
Abstract：
Despite the potential advantages promised by solid-state batteries, the success of solid-state electrolytes has not yet been fully realised. This is due in part to the lower ionic conductivity of solid electrolytes. In many solid superionic conductors, grain boundaries are found to be ionically resistive and hence contribute to this lower ionic conductivity. Additionally, in spite of the hope that solid electrolytes would inhibit lithium filaments, in most scenarios their growth is still observed, and in some polycrystalline systems this is suggested to occur along grain boundaries. It is apparent that grain boundaries affect the performance of solid-state electrolytes, however a deeper understanding is lacking. In this perspective, the current theories relating to grain boundaries in solid-state electrolytes are explored, as well as addressing some of the challenges which arise when trying to investigate their role. Glasses are presented as a possible solution to reduce the effect of grain boundaries in electrolytes. Future research directions are suggested which will aid in both understanding the role of grain boundaries, and diminishing their contribution in cases where they are detrimental.
Despite the potential advantages promised by solid-state batteries, the success of solid-state electrolytes has not yet been fully realised. This is due in part to the lower ionic conductivity of solid electrolytes. In many solid superionic conductors, grain boundaries are found to be ionically resistive and hence contribute to this lower ionic conductivity. Additionally, in spite of the hope that solid electrolytes would inhibit lithium filaments, in most scenarios their growth is still observed, and in some polycrystalline systems this is suggested to occur along grain boundaries. It is apparent that grain boundaries affect the performance of solid-state electrolytes, however a deeper understanding is lacking. In this perspective, the current theories relating to grain boundaries in solid-state electrolytes are explored, as well as addressing some of the challenges which arise when trying to investigate their role. Glasses are presented as a possible solution to reduce the effect of grain boundaries in electrolytes. Future research directions are suggested which will aid in both understanding the role of grain boundaries, and diminishing their contribution in cases where they are detrimental.
Topical Review •
OPEN ACCESS
2022, 1(2)
DOI: 10.1088/2752-5724/ac681d
Abstract：
To fill the gap between accurate (and expensive) ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials, a new class of descriptions of atomic interactions has emerged and been widely applied; i.e. machine learning potentials (MLPs). One recently developed type of MLP is the deep potential (DP) method. In this review, we provide an introduction to DP methods in computational materials science. The theory underlying the DP method is presented along with a step-by-step introduction to their development and use. We also review materials applications of DPs in a wide range of materials systems. The DP Library provides a platform for the development of DPs and a database of extant DPs. We discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.
To fill the gap between accurate (and expensive) ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials, a new class of descriptions of atomic interactions has emerged and been widely applied; i.e. machine learning potentials (MLPs). One recently developed type of MLP is the deep potential (DP) method. In this review, we provide an introduction to DP methods in computational materials science. The theory underlying the DP method is presented along with a step-by-step introduction to their development and use. We also review materials applications of DPs in a wide range of materials systems. The DP Library provides a platform for the development of DPs and a database of extant DPs. We discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.
Paper •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac3897
Abstract：
Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes (SEs) of different crystallinity, namely glassy 1.5Li2S-0.5P2S5-LiI and argyrodite Li6PS5Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a SE with a low Young’s modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy SE employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.
Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes (SEs) of different crystallinity, namely glassy 1.5Li2S-0.5P2S5-LiI and argyrodite Li6PS5Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a SE with a low Young’s modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy SE employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.
Paper •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac3568
Abstract：
Perovskite quantum dots (PeQDs) are considered potential display materials due to their high color purity, high photoluminescence quantum yield (PLQY), low cost and easy film casting. In this work, a novel electroluminescence (EL) device consisting of the interface layer of long alkyl-based oleylammonium bromide (OAmBr), which passivates the surface defects of PeQDs and adjusts the carrier transport properties, was designed. The PLQY of the OAmBr/PeQD bilayer was significantly improved. A high-performance EL device with the structure of indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)/OAmBr/PeQDs/2,2,2-(1,3,5-benzinetriyl)-tris(1-phenyl-1H benzimidazole)/LiF/Al was constructed using a spin-coating method. A peak external quantum efficiency (EQE) of 16.5% at the emission wavelength of 646 nm was obtained. Furthermore, an efficient matrix EL device was fabricated using an inkjet printing method. A high-quality PeQD matrix film was obtained by introducing small amounts of polybutene into the PeQDs to improve the printing process. The EQE reached 9.6% for the matrix device with 120 pixels per inch and the same device structure as that of the spin-coating one.
Perovskite quantum dots (PeQDs) are considered potential display materials due to their high color purity, high photoluminescence quantum yield (PLQY), low cost and easy film casting. In this work, a novel electroluminescence (EL) device consisting of the interface layer of long alkyl-based oleylammonium bromide (OAmBr), which passivates the surface defects of PeQDs and adjusts the carrier transport properties, was designed. The PLQY of the OAmBr/PeQD bilayer was significantly improved. A high-performance EL device with the structure of indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)/OAmBr/PeQDs/2,2,2-(1,3,5-benzinetriyl)-tris(1-phenyl-1H benzimidazole)/LiF/Al was constructed using a spin-coating method. A peak external quantum efficiency (EQE) of 16.5% at the emission wavelength of 646 nm was obtained. Furthermore, an efficient matrix EL device was fabricated using an inkjet printing method. A high-quality PeQD matrix film was obtained by introducing small amounts of polybutene into the PeQDs to improve the printing process. The EQE reached 9.6% for the matrix device with 120 pixels per inch and the same device structure as that of the spin-coating one.
Topical Review •
OPEN ACCESS
2022, 1(2)
DOI: 10.1088/2752-5724/ac4263
Abstract：
Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique. In particular, aqueous zinc-ion capacitors (ZIC), possessing the merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities. Then, we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, we propose research challenges and development directions for ZIC. This review provides guidance for the design and construction of high-performance ZIC.
Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique. In particular, aqueous zinc-ion capacitors (ZIC), possessing the merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities. Then, we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, we propose research challenges and development directions for ZIC. This review provides guidance for the design and construction of high-performance ZIC.
Topical Review •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac49e3
Abstract：
Since being rediscovered as an emerging 2D material, black phosphorus (BP), with an extraordinary energy structure and unusually strong interlayer interactions, offers new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges for future BP-related research are considered.
Since being rediscovered as an emerging 2D material, black phosphorus (BP), with an extraordinary energy structure and unusually strong interlayer interactions, offers new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges for future BP-related research are considered.
Topical Review •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac4558
Abstract：
Metallic glasses (MGs) or amorphous alloys are an important engineering material that has a history of research of about 80-90 years. While different fast cooling methods were developed for multi-component MGs between 1960s and 1980s, 1990s witnessed a surge of research interest in the development of bulk metallic glasses (BGMs). Since then, one central theme of research in the metallic-glass community has been compositional design that aims to search for MGs with a better glass forming ability, a larger size and/or more interesting properties, which can hence meet the demands from more important applications. In this review article, we focus on the recent development of chemically complex MGs, such as high entropy MGs, with new tools that were not available or mature yet until recently, such as the state-of-the-art additive manufacturing technologies, high throughput materials design techniques and the methods for big data analyses (e.g. machine learning and artificial intelligence). We also discuss the recent use of MGs in a variety of novel and important applications, from personal healthcare, electric energy transfer to nuclear energy that plays a pivotal role in the battle against global warming.
Metallic glasses (MGs) or amorphous alloys are an important engineering material that has a history of research of about 80-90 years. While different fast cooling methods were developed for multi-component MGs between 1960s and 1980s, 1990s witnessed a surge of research interest in the development of bulk metallic glasses (BGMs). Since then, one central theme of research in the metallic-glass community has been compositional design that aims to search for MGs with a better glass forming ability, a larger size and/or more interesting properties, which can hence meet the demands from more important applications. In this review article, we focus on the recent development of chemically complex MGs, such as high entropy MGs, with new tools that were not available or mature yet until recently, such as the state-of-the-art additive manufacturing technologies, high throughput materials design techniques and the methods for big data analyses (e.g. machine learning and artificial intelligence). We also discuss the recent use of MGs in a variety of novel and important applications, from personal healthcare, electric energy transfer to nuclear energy that plays a pivotal role in the battle against global warming.
Topical Review •
OPEN ACCESS
2022, 1(2)
DOI: 10.1088/2752-5724/ac681d
Abstract：
To fill the gap between accurate (and expensive) ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials, a new class of descriptions of atomic interactions has emerged and been widely applied; i.e. machine learning potentials (MLPs). One recently developed type of MLP is the deep potential (DP) method. In this review, we provide an introduction to DP methods in computational materials science. The theory underlying the DP method is presented along with a step-by-step introduction to their development and use. We also review materials applications of DPs in a wide range of materials systems. The DP Library provides a platform for the development of DPs and a database of extant DPs. We discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.
To fill the gap between accurate (and expensive) ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials, a new class of descriptions of atomic interactions has emerged and been widely applied; i.e. machine learning potentials (MLPs). One recently developed type of MLP is the deep potential (DP) method. In this review, we provide an introduction to DP methods in computational materials science. The theory underlying the DP method is presented along with a step-by-step introduction to their development and use. We also review materials applications of DPs in a wide range of materials systems. The DP Library provides a platform for the development of DPs and a database of extant DPs. We discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.
Topical Review •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac49e3
Abstract：
Since being rediscovered as an emerging 2D material, black phosphorus (BP), with an extraordinary energy structure and unusually strong interlayer interactions, offers new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges for future BP-related research are considered.
Since being rediscovered as an emerging 2D material, black phosphorus (BP), with an extraordinary energy structure and unusually strong interlayer interactions, offers new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges for future BP-related research are considered.
Topical Review •
OPEN ACCESS
2023, 2(1)
DOI: 10.1088/2752-5724/acbb5a
Abstract：
Charge-transporting layers (CTLs) are important in determining the performance and stability of perovskite solar cells (PSCs). Recently, there has been considerable use of self-assembled monolayers (SAMs) as charge-selective contacts, especially for hole-selective SAMs in inverted PSCs as well as perovskite involving tandem solar cells. The SAM-based charge-selective contact shows many advantages over traditional thin-film organic/inorganic CTLs, including reduced cost, low optical and electric loss, conformal coating on a rough substrate, simple deposition on a large-area substrate and easy modulation of energy levels, molecular dipoles and surface properties. The incorporation of various hole-selective SAMs has resulted in high-efficiency single junction and tandem solar cells. This topical review summarizes both the advantages and challenges of SAM-based charge-selective contacts, and discusses the potential direction for future studies.
Charge-transporting layers (CTLs) are important in determining the performance and stability of perovskite solar cells (PSCs). Recently, there has been considerable use of self-assembled monolayers (SAMs) as charge-selective contacts, especially for hole-selective SAMs in inverted PSCs as well as perovskite involving tandem solar cells. The SAM-based charge-selective contact shows many advantages over traditional thin-film organic/inorganic CTLs, including reduced cost, low optical and electric loss, conformal coating on a rough substrate, simple deposition on a large-area substrate and easy modulation of energy levels, molecular dipoles and surface properties. The incorporation of various hole-selective SAMs has resulted in high-efficiency single junction and tandem solar cells. This topical review summarizes both the advantages and challenges of SAM-based charge-selective contacts, and discusses the potential direction for future studies.
Paper •
OPEN ACCESS
2022, 1(3)
DOI: 10.1088/2752-5724/ac8ab9
Abstract：
P2-type layered oxides with the general Na-deficient composition NaxTMO2 (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na+ transport pathways present in the structure lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V and metal dissolution at low potentials upon discharge results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na0.67(Mn0.55Ni0.21Co0.24)O2, Na0.67(Mn0.45Ni0.18Co0.24Ti0.1Mg0.03)O2 and Na0.67(Mn0.45Ni0.18Co0.18Ti0.1Mg0.03Al0.04Fe0.02)O2 with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.
P2-type layered oxides with the general Na-deficient composition NaxTMO2 (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na+ transport pathways present in the structure lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V and metal dissolution at low potentials upon discharge results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na0.67(Mn0.55Ni0.21Co0.24)O2, Na0.67(Mn0.45Ni0.18Co0.24Ti0.1Mg0.03)O2 and Na0.67(Mn0.45Ni0.18Co0.18Ti0.1Mg0.03Al0.04Fe0.02)O2 with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.
Topical Review •
OPEN ACCESS
2022, 1(2)
DOI: 10.1088/2752-5724/ac4263
Abstract：
Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique. In particular, aqueous zinc-ion capacitors (ZIC), possessing the merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities. Then, we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, we propose research challenges and development directions for ZIC. This review provides guidance for the design and construction of high-performance ZIC.
Ion-hybrid capacitors are expected to combine the high specific energy of battery-type materials and the superior specific power of capacitor-type materials and are considered as a promising energy storage technique. In particular, aqueous zinc-ion capacitors (ZIC), possessing the merits of high safety, cost-efficiency and eco-friendliness, have been widely explored with various electrode materials and electrolytes to obtain excellent electrochemical performance. In this review, we first summarize the research progress on enhancing the specific capacitance of capacitor-type materials and review the research on improving the cycling capability of battery-type materials under high current densities. Then, we look back on the effects of electrolyte engineering on the electrochemical performance of ZIC. Finally, we propose research challenges and development directions for ZIC. This review provides guidance for the design and construction of high-performance ZIC.
Paper •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac3897
Abstract：
Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes (SEs) of different crystallinity, namely glassy 1.5Li2S-0.5P2S5-LiI and argyrodite Li6PS5Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a SE with a low Young’s modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy SE employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.
Solid-state batteries (SSBs) are a promising next step in electrochemical energy storage but are plagued by a number of problems. In this study, we demonstrate the recurring issue of mechanical degradation because of volume changes in layered Ni-rich oxide cathode materials in thiophosphate-based SSBs. Specifically, we explore superionic solid electrolytes (SEs) of different crystallinity, namely glassy 1.5Li2S-0.5P2S5-LiI and argyrodite Li6PS5Cl, with emphasis on how they affect the cyclability of slurry-cast cathodes with NCM622 (60% Ni) or NCM851005 (85% Ni). The application of a combination of ex situ and in situ analytical techniques helped to reveal the benefits of using a SE with a low Young’s modulus. Through a synergistic interplay of (electro)chemical and (chemo)mechanical effects, the glassy SE employed in this work was able to achieve robust and stable interfaces, enabling intimate contact with the cathode material while at the same time mitigating volume changes. Our results emphasize the importance of considering chemical, electrochemical, and mechanical properties to realize long-term cycling performance in high-loading SSBs.
Topical Review •
OPEN ACCESS
2022, 1(1)
DOI: 10.1088/2752-5724/ac427c
Abstract：
In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understanding solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense SSBs.
In the crucial area of sustainable energy storage, solid-state batteries (SSBs) with nonflammable solid electrolytes stand out due to their potential benefits of enhanced safety, energy density, and cycle life. However, the complexity within the composite cathode determines that fabricating an ideal electrode needs to link chemistry (atomic scale), materials (microscopic/mesoscopic scale), and electrode system (macroscopic scale). Therefore, understanding solid-state composite cathodes covering multiple scales is of vital importance for the development of practical SSBs. In this review, the challenges and basic knowledge of composite cathodes from the atomic scale to the macroscopic scale in SSBs are outlined with a special focus on the interfacial structure, charge transport, and mechanical degradation. Based on these dilemmas, emerging strategies to design a high-performance composite cathode and advanced characterization techniques are summarized. Moreover, future perspectives toward composite cathodes are discussed, aiming to facilitate the develop energy-dense SSBs.
Topical Review •
OPEN ACCESS
2023, 2(1)
DOI: 10.1088/2752-5724/acac68
Abstract：
Traditional lithium-ion batteries with graphite anodes have gradually been limited by the glass ceiling of energy density. As a result, lithium metal batteries (LMBs), regarded as the ideal alternative, have attracted considerable attention. However, lithium is highly reactive and susceptible to most electrolytes, resulting in poor cycle performance. In addition, lithium grows Li dendrites during charging, adversely affecting the safety of LMBs. Therefore, LMBs are more sensitive to the chemical composition of electrolytes and their relative ratios (concentrations). Recently, concentrated electrolytes have been widely demonstrated to be friendly to lithium metal anodes (LMAs). This review focuses on the progress of concentrated electrolytes in LMBs, including the solvation structure varying with concentration, unique functions in stabilizing the LMA, and their interfacial chemistry with LMA.
Traditional lithium-ion batteries with graphite anodes have gradually been limited by the glass ceiling of energy density. As a result, lithium metal batteries (LMBs), regarded as the ideal alternative, have attracted considerable attention. However, lithium is highly reactive and susceptible to most electrolytes, resulting in poor cycle performance. In addition, lithium grows Li dendrites during charging, adversely affecting the safety of LMBs. Therefore, LMBs are more sensitive to the chemical composition of electrolytes and their relative ratios (concentrations). Recently, concentrated electrolytes have been widely demonstrated to be friendly to lithium metal anodes (LMAs). This review focuses on the progress of concentrated electrolytes in LMBs, including the solvation structure varying with concentration, unique functions in stabilizing the LMA, and their interfacial chemistry with LMA.
Topical Review •
OPEN ACCESS
2022, 1(4)
DOI: 10.1088/2752-5724/ac88e7
Abstract：
Nickel-yttria stabilized zirconia (Ni-YSZ) cermet is the most commonly used anode in solid oxide fuel cells (SOFCs). The current article provides an insight into parameters which affect cell performance and stability by reviewing and discussing the related publications in this field. Understanding the parameters which affect the microstructure of Ni-YSZ such as grain size (Leng et al 2003 J. Power Sources 117 26-34) and ratio of Ni to YSZ, volume fraction of porosity, pore size and its distribution, tortuosity factor, characteristic pathway diameter and density of triple phase boundaries is the key to designing a fuel cell which shows high electrochemical performance. Lack of stability has been the main barrier to commercialization of SOFC technology. Parameters influencing the degradation of Ni-YSZ supported SOFCs such as Ni migration inside the anode during prolonged operation are discussed. The longest Ni-supported SOFC tests reported so far are examined and the crucial role of chromium poisoning due to interconnects, stack design and operating conditions in degradation of SOFCs is highlighted. The importance of calcination and milling of YSZ to development of porous structures suitable for Ni infiltration is explained and several methods to improve the electrochemical performance and stability of Ni-YSZ anode supported SOFCs are suggested.
Nickel-yttria stabilized zirconia (Ni-YSZ) cermet is the most commonly used anode in solid oxide fuel cells (SOFCs). The current article provides an insight into parameters which affect cell performance and stability by reviewing and discussing the related publications in this field. Understanding the parameters which affect the microstructure of Ni-YSZ such as grain size (Leng et al 2003 J. Power Sources 117 26-34) and ratio of Ni to YSZ, volume fraction of porosity, pore size and its distribution, tortuosity factor, characteristic pathway diameter and density of triple phase boundaries is the key to designing a fuel cell which shows high electrochemical performance. Lack of stability has been the main barrier to commercialization of SOFC technology. Parameters influencing the degradation of Ni-YSZ supported SOFCs such as Ni migration inside the anode during prolonged operation are discussed. The longest Ni-supported SOFC tests reported so far are examined and the crucial role of chromium poisoning due to interconnects, stack design and operating conditions in degradation of SOFCs is highlighted. The importance of calcination and milling of YSZ to development of porous structures suitable for Ni infiltration is explained and several methods to improve the electrochemical performance and stability of Ni-YSZ anode supported SOFCs are suggested.
Perspective •
OPEN ACCESS
2023, 2(3)
DOI: 10.1088/2752-5724/accdf3
Abstract：
Despite the efforts devoted to the identification of new electrode materials with higher specific capacities and electrolyte additives to mitigate the well-known limitations of current lithium-ion batteries, this technology is believed to have almost reached its energy density limit. It suffers also of a severe safety concern ascribed to the use of flammable liquid-based electrolytes. In this regard, solid-state electrolytes (SSEs) enabling the use of lithium metal as anode in the so-called solid-state lithium metal batteries (SSLMBs) are considered as the most desirable solution to tackle the aforementioned limitations. This emerging technology has rapidly evolved in recent years thanks to the striking advances gained in the domain of electrolyte materials, where SSEs can be classified according to their core chemistry as organic, inorganic, and hybrid/composite electrolytes. This strategic review presents a critical analysis of the design strategies reported in the field of SSEs, summarizing their main advantages and disadvantages, and providing a future perspective toward the rapid development of SSLMB technology.
Despite the efforts devoted to the identification of new electrode materials with higher specific capacities and electrolyte additives to mitigate the well-known limitations of current lithium-ion batteries, this technology is believed to have almost reached its energy density limit. It suffers also of a severe safety concern ascribed to the use of flammable liquid-based electrolytes. In this regard, solid-state electrolytes (SSEs) enabling the use of lithium metal as anode in the so-called solid-state lithium metal batteries (SSLMBs) are considered as the most desirable solution to tackle the aforementioned limitations. This emerging technology has rapidly evolved in recent years thanks to the striking advances gained in the domain of electrolyte materials, where SSEs can be classified according to their core chemistry as organic, inorganic, and hybrid/composite electrolytes. This strategic review presents a critical analysis of the design strategies reported in the field of SSEs, summarizing their main advantages and disadvantages, and providing a future perspective toward the rapid development of SSLMB technology.
