Modification Of Lithium Anode For Lithium Metal-Based Secondary Batteries

Lithium metal negative electrode has high theoretical specific capacity(3862 mAh/g),low redox potential(-3.045 V vs.standard hydrogen electrode)and low specific gravity(M=6.94 g/mol,?=0.59 g/cm3),is considered to be one of the most ideal negative materials at present.However,the generation and growth of lithium dendrites and the volume change of the electrode during cycling seriously hinders the practical application of the lithium metal anode.Titanium nitride has high chemical stability,low reaction activity with lithium ions but has certain lithium-philic characteristics,can regulate the uniform deposition of lithium,improve the stability of the solid electrolytic film;In addition,the molybdenum disulfide layer has a unique two-dimensional nano-layered structure,which can shorten the diffusion path of lithium ions and improve the diffusio n rate of lithium ions at the interface,thereby improving the interface stability of lithium-rich alloy electrodes.Herein,we modify the lithium metal anode through two aspects:electrode surface modification and electrode structure stabilization.Titanium nitride was sputtered on the surface of lithium metal anode by reactive magnetron sputtering.According to electrochemical performance test and physical morphology characterization,it can be seen that when titanium nitride is modified for 30 min,the polarization degree of the electrode in the symmetrical cell is reduced,the coulomb efficiency in the lithium-copper half-cell is basically stable at 95%,the discharge specific capacity in the lithium sulfur cell is increased from 756 mA h/g to 887 mA h/g,and the interface impedance of the electrode is significantly reduced.The growth of lithium dendrites at the interface is obviously inhibited.The results show that titanium nitride layer is helpful to improve the cycla stability of lithium metal electrode.In order to improve the structure stability of the electrode,lithium magnesium alloy electrode was prepared by doping 20%magnesium metal in lithium metal to stabilize the electnxie structurc.The doping of magnesium regulated the uniform deposition of lithium and inhibited the growth of dendrite.The prepared lithium magnesium alloy electrode has a high specific discharge capacity(941 mA h/g)at 0.2 C,low interface impedance,and no obvious dendrite and corrosion on the surface of the electrode after cycling,which shows that the alloy electrode has high structural stability.Based on the above research,the surface modification method was used to modify the electrode of lithium magnesium alloy with the surface of molybdenum disulfide layer.Through electrochemical performance test and physical morphology characterization,the molybdenum disulfide modified alloy electrodes 30 s,alloy electrode showed a small voltage polarization in the symmetrical cell,the coulomb efficiency in the lithium copper half-cell is basically stable at 95%,the discharge specific capacity in the lithium sulfur cell is increased to 977 mA h/g,and there is still 689 mA h/g after 100 cycles,and under the high rate of 1 C,2 C have good retention capacity.The modified alloy electrode shows better interfacial stability and cyclic stability,which indicates that the molybdenum disulfide layer is helpful to improve the electrochemical cycling performance of lithium magnesium alloy electrode.