Li metal is considered an ideal anode material for application in the next-generation secondary batteries.However,the commercial application of Li metal batteries has not yet been achieved due to the safety concern ca...Li metal is considered an ideal anode material for application in the next-generation secondary batteries.However,the commercial application of Li metal batteries has not yet been achieved due to the safety concern caused by Li dendrites growth.Despite the fact that many recent experimental studies found that external pressure suppresses the Li dendrites growth,the mechanism of the external pressure effect on Li dendrites remains poorly understood on the atomic scale.Herein,the large-scale molecular dynamics simulations of Li dendrites growth under different external pressure were performed with a machine learning potential,which has the quantum-mechanical accuracy.The simulation results reveal that the external pressure promotes the process of Li self-healing.With the increase of external pressure,the hole defects and Li dendrites would gradually fuse and disappear.This work provides a new perspective for understanding the mechanism for the impact of external pressure on Li dendrites.展开更多
Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In t...Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.展开更多
Tandem solar cells represent an attractive technology to overcome the Shockley-Queisser limit of single-junction cells.Recently,wide-bandgap metal halide perovskites are paired with complementary bandgap photovoltaic ...Tandem solar cells represent an attractive technology to overcome the Shockley-Queisser limit of single-junction cells.Recently,wide-bandgap metal halide perovskites are paired with complementary bandgap photovoltaic technologies(such as silicon,CIGS,and low-bandgap perovskites) in tandem architectures,enabling a pathway to achieve industry goals of pushing power-conversion-efficiency(PCE) over 30% at low cost.In this review of perovskite tandems,we aim to present an overview of their recent progress on efficiency and stability enhancement.We start by comparing 2-terminal and 4-terminal tandems,from the perspective of technical and cost barriers.We then focus on 2-terminal tandems and summarize the collective efforts on improving their performance,fabrication processing,and operational stability.We also present the comprehensive progress in perovskite/Si, perovskite/CIGS,and perovskite/perovskite monolithic tandems,alo ng with advanced technology for subcell diagnosis.We highlight that an in-depth understanding of the mobile ion character of perovskites and applying consensus stability tests(such as the extended ISOS protocol for perovskite) under light,heating,and voltage bias are critically important for improving perovskite tandems toward 25-year outdoor operation lifetime.展开更多
基金supported by the National Natural Science Foundation of China(No.52272180,No.12174162,No.51962010)the Shenzhen Science and Technology Research Grant(No.20220810123501001)the IER Foundation 2021(IERF202104)。
文摘Li metal is considered an ideal anode material for application in the next-generation secondary batteries.However,the commercial application of Li metal batteries has not yet been achieved due to the safety concern caused by Li dendrites growth.Despite the fact that many recent experimental studies found that external pressure suppresses the Li dendrites growth,the mechanism of the external pressure effect on Li dendrites remains poorly understood on the atomic scale.Herein,the large-scale molecular dynamics simulations of Li dendrites growth under different external pressure were performed with a machine learning potential,which has the quantum-mechanical accuracy.The simulation results reveal that the external pressure promotes the process of Li self-healing.With the increase of external pressure,the hole defects and Li dendrites would gradually fuse and disappear.This work provides a new perspective for understanding the mechanism for the impact of external pressure on Li dendrites.
基金Project supported by Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB)(Grant No.21C-OP-202013)the National Natural Science Foundation of China(Grant No.12064027)+1 种基金the International Science and Technology Cooperation Program of China(Grant No.2015DFA61800)the Scientific Research Fund of Jiangxi Provincial Education Department,China(Grant No.GJJ180973).
文摘Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural materials.In this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye temperature.Quaternary carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–C.However,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds form.When the pressure reaches 20 GPa,the covalent bonds change to metallic bonds.The volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at most.Pressurization can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C ceramics.At 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ductility.However,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing pressure.In addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.
基金supported by the Fundamental Research Funds for the Central Universities(WK2060140026)the Fujian science&technology innovation laboratory for energy devices of China(21COP-202006)。
文摘Tandem solar cells represent an attractive technology to overcome the Shockley-Queisser limit of single-junction cells.Recently,wide-bandgap metal halide perovskites are paired with complementary bandgap photovoltaic technologies(such as silicon,CIGS,and low-bandgap perovskites) in tandem architectures,enabling a pathway to achieve industry goals of pushing power-conversion-efficiency(PCE) over 30% at low cost.In this review of perovskite tandems,we aim to present an overview of their recent progress on efficiency and stability enhancement.We start by comparing 2-terminal and 4-terminal tandems,from the perspective of technical and cost barriers.We then focus on 2-terminal tandems and summarize the collective efforts on improving their performance,fabrication processing,and operational stability.We also present the comprehensive progress in perovskite/Si, perovskite/CIGS,and perovskite/perovskite monolithic tandems,alo ng with advanced technology for subcell diagnosis.We highlight that an in-depth understanding of the mobile ion character of perovskites and applying consensus stability tests(such as the extended ISOS protocol for perovskite) under light,heating,and voltage bias are critically important for improving perovskite tandems toward 25-year outdoor operation lifetime.
基金financially supported by the starting fund of Peking University,Shenzhen Graduate School and Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB)。
基金financially supported by the Starting Fund of Peking University Shenzhen Graduate School and Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB)the National Natural Science Foundation of China(12174162)。
