Surface Modification Of Stainless Steel Mesh Collector For Depressing Lithium Dendrite Growth

Lithium metal is an ideal anode material for rechargeable lithium batteries due to its high theoretical specific capacity(3860 mAh g^-1),low density(0.59 g cm^-3)and the lowest electrochemical potential?-3.04V vs RHE?.Unfortunately,some key issues,such as Li dendrite growth,low columbic efficient and uncontrolled volume expansion,have prevented Li metal anodes from wide commercial applications.The corresponding inhibition strategies,like the uniform lithium ion flux method,the SEI protection method,the stable deposition by using host and the electrostatic shielding methods also had been raised.These strategies can alleviate the growth of lithium dendrites to a certain extent,but they all fail to meet the requirements of commercial applications.Therefore,a low-temperature plasma ion nitriding and one-step chemical solution methods were used to modify the surface lithiophilic of the low-cost woven 304 stainless steel mesh current collector,and then to fabricate composite Li anode by infiltrating with the molten lithium metal anode.The chemical composition,the micron pores,good conductivity and the surface lithiophilic layer of the stainless steel mesh were used to accommodate and homogenize the nucleation of lithium,as well as the depressing of dendrite growth,and then to improve the coulomb efficiency and cycle performance of lithium metal anode.The mainconclusions can be drawn as follows:Firstly,we fabricated Li/stainless steel composite anodes with different meshes by using molten lithium infiltration method,which lithium can be infiltrated into the internal pores of the stainless steel mesh in 2³ min.The results showed that the composite Li anodes prepared by molten lithium infiltration method has more excellent cycle stability and cycle life than that prepared by the mechanical pressing.Among them,SS?M500?current collector showed the best electrochemical performance considering the factors of price and weight,and its symmetrical cell showes a cycle life of more than 1000 hours?500 cycles?,which is twice times longer than that of the symmetrical cell using lithium foil.However,its weight is 77%of lithium foil,and its price is 41%of lithium foil.The full cell prepared by the M-SS?M500?/Li composite anode showes a initial discharge capacity of 138mA h g^-1,and the capacity retention after 200 cycles is 95.6%,which is much higher than a full battery using lithium foil?62.1%?.Although the composite anode has better cycle stability performance and cycle life than the lithium foil,the voltage of Li stripping/plating and polarization voltage are still relatively high,indicating that the stainless steel meshesexhibit poor wettability to lithium.Then,we modified the surface of SS?M500?current collector via low-tempearture plasma nitridation to form an amorphous Cr2N and CrN lithiophilic layer.The N-3 SS?M500?current collector obtained by plasma nitridation at 350°C for 1 hour showes the best electrochemical performance in a half-cell test,which the average coulombic efficiency cycled at a current density of 2 mA cm^-2,with a capacity of 1 mA h cm^-2 for 200 cycles is97.51%,and is 1.22%higher than SS?M500?.And the Li stripping/plating voltage is 16 mV,and also much lower than SS?M500?.In the symmetrical cells test,the N-3 SS 500/Li symmetrical cell has a cycle life of more than 2000h?1000 cycles?,which is twice times longer than that of M-SS?M500?/Li symmetrical cells,and the longest record ever reported in all the references until now.Furthermore,Li stripping/plating voltage hysteresis is about 11mV.In the full cell test,the capacity retention of full cell using N-3 SS?M500?/Li composite anode cycled at 3C rate for 200 cycles is 98.0%,which is 2.4%higher than that of the M-SS?M500?/Li full cell.Finally,we modified 3D stainless steel mesh with N-doped graphene,which was mainly composed of pyrrolic nitrogen.The results shown that the average coulombic efficiency of N-C-SS?M500?cycled at 2 mA cm^-2,1 mA h cm^-2 for 200 cycles is 97.73%,and an ultralow Li stripping/plating voltage hysteresis of 15 mV,which is the lowest value ever reported until now.It is indicated that N-doped graphene layer can greatly improve the lithiophilicity of 3D porous stainless steel mesh.In a symmetrical cell,the N-C-SS?M500?/Li composite anode showes a cycle life of more than 1850 hours?925 cycles?and 210 hours?330 cycles?,at the current densities of 1 mA cm^-2 and 3 mA cm^-2.The N-C-SS?M500?/Li composite anode exhibits a capacity retention of 96.9%cycled at 3 C for 200 cycles,indicating that the N-doped graphene coating also can improve the cycle stability and cycle life of the Li composite anode.