Copper sulfide(CuS)is a promising cathode for lithium-ion batteries(LIBs)due to its impeccable theoretical energy density(~1015 Wh·kg^(−1) and 4743 Wh·L^(−1)).However,it suffers from voltage decay leaded ene...Copper sulfide(CuS)is a promising cathode for lithium-ion batteries(LIBs)due to its impeccable theoretical energy density(~1015 Wh·kg^(−1) and 4743 Wh·L^(−1)).However,it suffers from voltage decay leaded energy density loss and low energy efficiency,which hinders its application.In this work,with combined ex-situ/in-situ X-ray diffraction(XRD)and electrochemical analysis,we explore detailed degradation mechanisms.For the voltage decay,it is attributed to a spontaneous reaction between CuS cathode and copper current collector(Cu CC).This reaction leads to energy density loss and active materials degradation(CuS→Cu_(1.81)S).As for energy efficiency,CuS undergoes a series of phase transformations.The main phase transition processes are CuS→α-LiCuS→Li_(2−x)Cu_(x)S+Cu→Li_(2)S+Cu for discharge;Li_(2)S+Cu→Li_(2−x)Cu_(x)S→β-LiCuS→CuS for charge.Here,α-LiCuS,β-LiCuS,and Li_(2−x)CuxS are newly identified phases.These phase changes are driven by topotactic-reaction-related copper diffusion and rearrangement.This work demonstrates the significance of transition-metal diffusion in the intermediates formation and phase change in conversion-type materials.展开更多
Copper oxide nanowires with varying oxidation states are prepared and their activity for water oxidation is studied. The nanowires with a CuO phase are found to be the most active, and their degree of crystallinity is...Copper oxide nanowires with varying oxidation states are prepared and their activity for water oxidation is studied. The nanowires with a CuO phase are found to be the most active, and their degree of crystallinity is important in achieving efficient water oxidation. For the crystalline CuO nanowires in a weakly basic Na2CO3 electrolyte, a Tafel slope of 41 mV/decade, an overpotential of approximately 500 mV at - 10 mA/crn2 （without compensation for the solution resistance）, and a faradaic efficiency of nearly 100% are obtained. This electrode maintains a stable current for over 15 lx The low overpotential of 500 mV at 10 mA/cm2, small Tafel slope, long-term stability, and low cost make CuO one of the most promising catalysts for water oxidation. Moreover, the evolution of the CuO nanowire morphology over time is studied by electron microscop）-revealing that the diffusion of Cu ions from the interior of the nanowires to their surface causes the aggregation of individual nanowires over time. However, despite this aggregation, the current density remains nearly constant, because the total electrochemically active surface area of CuO does not change.展开更多
基金supported by the National Natural Science Foundation of China(No.52072061)the Natural Science Foundation of Sichuan,China(No.2023NSFSC1914).
文摘Copper sulfide(CuS)is a promising cathode for lithium-ion batteries(LIBs)due to its impeccable theoretical energy density(~1015 Wh·kg^(−1) and 4743 Wh·L^(−1)).However,it suffers from voltage decay leaded energy density loss and low energy efficiency,which hinders its application.In this work,with combined ex-situ/in-situ X-ray diffraction(XRD)and electrochemical analysis,we explore detailed degradation mechanisms.For the voltage decay,it is attributed to a spontaneous reaction between CuS cathode and copper current collector(Cu CC).This reaction leads to energy density loss and active materials degradation(CuS→Cu_(1.81)S).As for energy efficiency,CuS undergoes a series of phase transformations.The main phase transition processes are CuS→α-LiCuS→Li_(2−x)Cu_(x)S+Cu→Li_(2)S+Cu for discharge;Li_(2)S+Cu→Li_(2−x)Cu_(x)S→β-LiCuS→CuS for charge.Here,α-LiCuS,β-LiCuS,and Li_(2−x)CuxS are newly identified phases.These phase changes are driven by topotactic-reaction-related copper diffusion and rearrangement.This work demonstrates the significance of transition-metal diffusion in the intermediates formation and phase change in conversion-type materials.
文摘Copper oxide nanowires with varying oxidation states are prepared and their activity for water oxidation is studied. The nanowires with a CuO phase are found to be the most active, and their degree of crystallinity is important in achieving efficient water oxidation. For the crystalline CuO nanowires in a weakly basic Na2CO3 electrolyte, a Tafel slope of 41 mV/decade, an overpotential of approximately 500 mV at - 10 mA/crn2 （without compensation for the solution resistance）, and a faradaic efficiency of nearly 100% are obtained. This electrode maintains a stable current for over 15 lx The low overpotential of 500 mV at 10 mA/cm2, small Tafel slope, long-term stability, and low cost make CuO one of the most promising catalysts for water oxidation. Moreover, the evolution of the CuO nanowire morphology over time is studied by electron microscop）-revealing that the diffusion of Cu ions from the interior of the nanowires to their surface causes the aggregation of individual nanowires over time. However, despite this aggregation, the current density remains nearly constant, because the total electrochemically active surface area of CuO does not change.
