Energy density can be substantially raised and even maximized if the bulk of an electrode material is fully utilized.Transition metal oxides based on conversion reaction mechanism are the imperative choice due to eith...Energy density can be substantially raised and even maximized if the bulk of an electrode material is fully utilized.Transition metal oxides based on conversion reaction mechanism are the imperative choice due to either constructing nanostructure or intercalation pseudocapacitance with their intrinsic limitations.However,the fully bulk utilization of transition metal oxides is hindered by the poor understanding of atomic-level conversion reaction mechanism,particularly it is largely missing at clarifying how the phase transformation(conversion reaction)determines the electrochemical performance such as power density and cyclic stability.Herein,α-Fe_(2)O_(3) is a case provided to claim how the diffusional and diffusionless transformation determine the electrochemical behaviors,as of its conversion reaction mechanism with fully bulk utilization in alkaline electrolyte.Specifically,the discharge productα-FeOOH diffusional from Fe(OH)2 is structurally identified as the atomic-level arch criminal for its cyclic stability deterioration,whereas the counterpartδ-FeOOH is theoretically diffusionless-like,unlocking the full potential of the pseudocapacitance with fully bulk utilization.Thus,such pseudocapacitance,in proof-of-concept and termed as conversion pseudocapacitance,is achieved via diffusionless-like transformation.This work not only provides an atomic-level perspective to reassess the potential electrochemical performance of the transition metal oxides electrode materials based on conversion reaction mechanism but also debuts a new paradigm for pseudocapacitance.展开更多
An analytical model was developed to describe Si？As alloy solidification in the whole range of measured interface velocity. It is demonstrated that at low interface velocity, the solidification occurs in the initial ...An analytical model was developed to describe Si？As alloy solidification in the whole range of measured interface velocity. It is demonstrated that at low interface velocity, the solidification occurs in the initial transient regime. The model leads to good comparison with the experimental data taking both local nonequilibrium effects at high interface velocity and steady state effects at low interface velocity into account. The local nonequilibrium diffusion effects shrink the initial transient period and lead to diffusionless solidification at high interface velocity.展开更多
Using the phase field crystal approach, the crystallization process within the liquid-solid coexistence region is inves- tigated for a square lattice on an atomic scale. Two competing growth modes, i.e., the diffusion...Using the phase field crystal approach, the crystallization process within the liquid-solid coexistence region is inves- tigated for a square lattice on an atomic scale. Two competing growth modes, i.e., the diffusion-controlled growth through long-range atomic migration in liquid and the diffusionless growth through local atom rearrangement, which give rise to two completely different crystallization behaviors, are compared. In the diffusion-controlled regime, the interface migrates in a layerwise manner, leading to a gradual change of crystal morphology from truncated square to four-fold symmetric dendrite with the increase of driving force. For the diffusionless growth mode, a single crystal with no significant density change occupies the whole system at a faster rate while exhibiting a small growth anisotropy. The competition between these two modes is also discussed from the key input of the phase field crystal model： the correlation function.展开更多
基金This research is supported by the National Natural Science Foundation of China (51932003,51872115)2020 International Cooperation Project of the Department of Science and Technology of Jilin Province (20200801001GH)+5 种基金Program for the Development of Science and Technology of Jilin Province (20190201309JC)the Jilin Province/Jilin University Co-Construction Project-Funds for New Materials (SXGJSF2017-3,Branch-2/440050316A36)Project for Self-innovation Capability Construction of Jilin Province Development and Reform Commission (2021C026)the Open Project Program of Wuhan National Laboratory for Optoelectronics (2018WNLOKF022)the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT,2017TD-09)the Fundamental Research Funds for the Central Universities JLU,and“Double-First Class”Discipline for Materials Science&Engineering.
文摘Energy density can be substantially raised and even maximized if the bulk of an electrode material is fully utilized.Transition metal oxides based on conversion reaction mechanism are the imperative choice due to either constructing nanostructure or intercalation pseudocapacitance with their intrinsic limitations.However,the fully bulk utilization of transition metal oxides is hindered by the poor understanding of atomic-level conversion reaction mechanism,particularly it is largely missing at clarifying how the phase transformation(conversion reaction)determines the electrochemical performance such as power density and cyclic stability.Herein,α-Fe_(2)O_(3) is a case provided to claim how the diffusional and diffusionless transformation determine the electrochemical behaviors,as of its conversion reaction mechanism with fully bulk utilization in alkaline electrolyte.Specifically,the discharge productα-FeOOH diffusional from Fe(OH)2 is structurally identified as the atomic-level arch criminal for its cyclic stability deterioration,whereas the counterpartδ-FeOOH is theoretically diffusionless-like,unlocking the full potential of the pseudocapacitance with fully bulk utilization.Thus,such pseudocapacitance,in proof-of-concept and termed as conversion pseudocapacitance,is achieved via diffusionless-like transformation.This work not only provides an atomic-level perspective to reassess the potential electrochemical performance of the transition metal oxides electrode materials based on conversion reaction mechanism but also debuts a new paradigm for pseudocapacitance.
基金partially supported by RFBR, research project No. 14-48-03535
文摘An analytical model was developed to describe Si？As alloy solidification in the whole range of measured interface velocity. It is demonstrated that at low interface velocity, the solidification occurs in the initial transient regime. The model leads to good comparison with the experimental data taking both local nonequilibrium effects at high interface velocity and steady state effects at low interface velocity into account. The local nonequilibrium diffusion effects shrink the initial transient period and lead to diffusionless solidification at high interface velocity.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51174168 and 51274167)the Foundation for Fundamental Research of Northwestern Polytechnical University,China(Grant No.JC20120222)
文摘Using the phase field crystal approach, the crystallization process within the liquid-solid coexistence region is inves- tigated for a square lattice on an atomic scale. Two competing growth modes, i.e., the diffusion-controlled growth through long-range atomic migration in liquid and the diffusionless growth through local atom rearrangement, which give rise to two completely different crystallization behaviors, are compared. In the diffusion-controlled regime, the interface migrates in a layerwise manner, leading to a gradual change of crystal morphology from truncated square to four-fold symmetric dendrite with the increase of driving force. For the diffusionless growth mode, a single crystal with no significant density change occupies the whole system at a faster rate while exhibiting a small growth anisotropy. The competition between these two modes is also discussed from the key input of the phase field crystal model： the correlation function.
