Study On Lithium Metal Anode Based On Skeleton Surface Modification And Its Electrochemical Performance

In recent years,it is urgent to develop batteries with high specific capacity to meet the requirements of long-endurance electric vehicles.Lithium metal has the potential to become the next-generation anode material because of its ultra-high theoretical capacity and low electrochemical potential.However,the growth of lithium metal in discharge process is usually uncontrollable,and the generation of lithium dendrites and dead lithium during cycling make lithium metal batteries face severe safety problems.In order to induce the uniform deposition of lithium metal and reduce the generation of lithium dendrites and dead lithium effectively,starting with the modification of skeleton surface of lithium metal batteries,this thesis carried out the following two work:1.Ni Foam modified with Bi-nanosheets(Ni@Bi Foam)was constructed,then a smooth and dense lithiophilic Li3Bi layer was in situ formed during the discharge process.On one hand,the formation of lithiophilic Li3Bi layer remodeled the thermodynamics of the skeleton surface and accelerated the kinetic process of lithium metal plating,then the uniform deposition of lithium metal was induced effectively and the generation of dendrites and dead lithium was alleviated.On the other hand,the smooth and dense Li3Bi layer also laid a good foundation for the subsequent uniform deposition of lithium metal.In half cells(1 mA cm-2&1 mAh cm-2),Ni@Bi Foam exhibited great stability(>500 cycles)with a high average Coulombic Efficiency(CE)as high as 98.46%.When assembled with high-loading LiFePO4 cathode(10.1 mg cm2),Ni@Bi Foam still exhibited excellent cycling stability and rate performance.2.Through introducing Bi2S3 into Cu Mesh(Cu@Bi2S3 Mesh),a SEI with Li3Bi and Li2S can be pre-constructed.Compared with the disordered deposition of lithium metal on Cu Mesh,Li mainly deposited uniformly along the skeleton of Cu@Bi2S3 Mesh.In this way,lithium metal exhibited excellent plating/stripping performance.Assembling a symmetrical cell(1 mA cm-2&1 mAh cm-2),it could maintain a small overpotential(15 mV)of Li deposition,and cycled for over 1300 h stably.After cycling at 0.5 C for 120 cycles,the capacity attenuation of LiFePO4 full cell assembled with Cu@Bi2S3 Mesh in per cycle is only 0.027%.