Study On Copper Based Current Collector For Lithium Ion Battery Anodes

The lithium metal anode material of lithium-ion battery will inevitably produce dead lithium which reduces battery capacity and lithium dendrites which may cause battery short circuit in the battery cycle,which seriously affects the battery performance.Therefore,in view of these two problems,thesis takes copper,the most common commercial lithium ion battery anode fluid collector material,as the matrix and constructs the anode fluid collector with lipophilic three-dimensional nanostructure through surface engineering design.Due to its high specific surface area and lipophilic surface characteristics,the designed new anode current collector can significantly improve the stability of lithium metal as the anode of lithium ion battery.The main contents of thesis are as follows:（1）In thesis,one-step combustion method is adopted to evenly distribute silver nanoparticles on the surface of copper foam,and Ag-Cu composite three-dimensional porous fluid collector（AC）is constructed.Copper foam is a porous material with large specific surface area,which can eliminate the volume change of lithium anode during charging/discharging process and inhibit the growth of lithium dendrite to a certain extent.The surface silver nanoparticles can effectively reduce the nucleation overpotential of lithium and induce uniform deposition of lithium.The results show that AC has significantly enhanced Coulomb efficiency compared with copper foam.The composite lithium anode composed of fluid and lithium metal also shows good stability in symmetric and full battery tests.（2）A high stability fluid collector（VGC）of graphite-modified copper foil was prepared by covering the surface of two-dimensional copper foil with porous layer of graphite interconnect by plasma enhanced chemical vapor deposition.The nanoscale pores on the surface of VGC collector can make the collector have excellent reversibility of lithium plating/lithium delithium in the charging/discharging process,while graphite itself has a certain lithium philicity,which can induce uniform deposition of lithium.The results show that compared with copper foil,using VGC as collector can significantly improve the electrochemical performance of the battery.Especially,when the current density is 3 m A·cm^-2 and the surface capacity is 3 m A·h·cm^-2,the symmetrical battery can still cycle stably for 500 h.（3）Thesis use physical vapor deposition and annealing methods to generate a copper-Zinc alloy layer on the surface of copper foil,and construct a high performance copper-zinc composite fluid collector（ZC）.The rough three-dimensional surface of ZC can reduce the local current density during the battery cycle and inhibit the growth of lithium dendrites.Uniformly distributed zinc on the surface can be used as nucleation site of lithium and induce uniform deposition of lithium.The results showed that ZC could significantly reduce the nucleation overpotential of lithium from 53.6 m V to 6.7 m V compared with copper foil,and showed excellent electrochemical performance in subsequent electrochemical tests.In particular,in the full battery cycle test at 3 C,the composite lithium anode composed of fluid collector and lithium metal was able to maintain a high capacity retention rate of 85.5%after 800 cycles.