Study On Modified Copper Current Collector For Stable Li Metal Anode

Second metal battery with high energy density has garnered great attention.Because the commercial Li-ion batteries cannot meet the rapid development of society when considering the increasing demand for electric vehicles and portable electronic devices.Li metal is considered to be a very promising anode material,since it holds quite a higher theoretical specific capacity and a lowest redox potential than other anode materials.However,the safety hazards caused by the Li dendrite limit its real applications.As the Li dendrites grow,it can render the breakdown of the solid electrolyte interphase?SEI?,leading to the formation of“dead Li”and deteriorate the lifespan of batteries.At the same time,Li dendrites can penetrate the separator further causing internal short circuits and even catastrophic safety hazards.Thus,inhibiting the growth of Li dendrites is an important prerequisite for achieving the rechargeable batteries with high energy density.Based on the growth mechanism of Li dendrites,in this paper,the modified copper current collectors were prepared to suppress the growth of Li dendrites,thereby improving the stability of the Li metal anode and providing the basis for its commercial application.Firstly,the commercial Cu foam was immersed into the graphene oxide suspension to prepare the rGO@Cu.And the rGO@Cu/Li battery was assembled to prove its excellent performance.Then the LiFePO₄ full cell was built using LiFePO₄ as a cathode and Li metal as an anode with 2D planar Cu foil?LiFePO₄/2D-Cu-Li?,3D Cu foam?LiFePO₄/3D-Cu-Li?,or a rGO@Cu?LiFePO₄/rGO@Cu-Li?current collector,at the same time,the electrochemical performance of these three kinds of cells was compared.At last,a porous Cu was prepared by de-alloying method using Cu-Zn alloy as raw material,the electrochemical performance of the Cu foil and the prepared porous Cu in the process of lithium deposition/stripping was compared.The main research contents and experimental results of this paper are as follows:?1?A spontaneous formation of rGO@Cu foam was occured via the reaction of 3D Cu foam with graphene oxide.Cu was oxidized and the GO was reduced to form rGO.The electrochemical performance and SEM characterization of rGO@Cu/Li prove that the rGO@Cu foam inhibits the growth of Li dendrites effectively as well as exhibiting superior properties to regulate Li nucleation.The rGO@Cu foam delivers a CE as high as 98.5%for over 350 cycles at the current density of 1 mA cm^-2.Furthermore,the LiFePO₄/rGO@Cu-Li full cell is assembled to prove the admirable capacities and indicates commercialization of Li-metal batteries.?2?A porous Cu was prepared by de-alloying method using brass sheet as raw material as well the mixture of H₂SO₄ and ZnSO₄ as a reaction solution.Porous Cu and planar Cu foil were directly used separately to assemble Cu/Li and Porous-Cu/Li batteries with a Li metal sheet as a counter electrode.Compared the electrochemical performance and the morphology of two kinds of current collectors,the porous Cu exhibits the excellent properties.The porous Cu delivers a CE as high as 96%for over 210 cycles at the current density of 0.5 mA cm^-2 and the initial CE is 87.62%.when the current density reaches 1 mA cm^-2,the CE of porous copper is stabilized at 95%during 80 cycles.All the results prove that the porous Cu can suppress the growth of Li dendrites and optimize the electrochemical performance of Li-metal anode.