Design,Preparation And Electrochemical Performance Of MXene-based Lithium Anodes For Lithium-sulfur Batteries

Lithium-sulfur batteries are the next-generation power batteries with high energy density and low-cost sulfur cathodes.A lot of research work has focused on improving the conductivity,loading and suppressing the shuttle effect of sulfur cathodes.In contrast,lithium metal anodes have received relatively less attention.There have been many problems with lithium metal anodes,such as dendrites and infinite volume expansion.However,these problems will be further aggravated by the multiple effects of high-rate discharge and polysulfide corrosion in lithium-sulfur batteries,which seriously affect the cycle stability and safety of Li-S batteries.Therefore,according to the special needs of lithium-sulfur batteries,it is particularly important to design and construct lithium metal anodes with high rate performance and stability against the polysulfides.In order to solve the above problems of the anodes in lithium-sulfur batteries,this article proposes a design idea to construct two-dimensional layered lithium metal anodes using surface-active layered materials to achieve multiple inhibition of the corrosion by polysulfide and dendrite growth,thereby improving the electrochemical performance of lithium-sulfur batteries.The pristine GO/Ti₃C₂T_x hybrid membrane was prepared by vacuum filtration using graphene oxide（GO）and Ti₃C₂T_x MXene as raw materials,and capillary action was introduced into the hybrid membrane layers through the thermal reduction of GO,Li-rGO/Ti₃C₂T_x electrodes with a two-dimensional layered structure were prepared through capillary self-implantation of lithium.The evolution process,influencing factors and the role of each component in the preparation of the electrode were explored,an efficient and stable Li-rGO/Ti₃C₂T_xelectrode preparation was achieved by adjusting the preparation conditions and component ratios.the design idea of the anode in the lithium-sulfur battery is firstly proposed.The problem of infinite volume expansion of the anode should be solved in priority.Secondly,the corrosion of lithium by polysulfides should be prevented as much as possible.Finally,the problems such as dendrites that have been alleviated can be assisted by selecting materials with suitable structure and surface activity.According to this idea,we prepared a two-dimensional layered electrode Li-rGO/Ti₃C₂T_x based on graphene oxide（GO）and Ti₃C₂T_x MXene to alleviate the volume change of lithium and block the corrosion of polysulfides.We explore its change mechanism in the preparation process,and the role and influencing factors of each component on the material structure.It is verified by experiments that the designed and constructed Li-rGO/Ti₃C₂T_x material has good electrochemical performance.Due to its stable layered structure,rGO/Ti₃C₂T_x anode can effectively alleviate the volume change of lithium during charging and discharging.The toughness of the 2D material can also cope with the surface deformation of the anode without cracking.In addition,the rich surface functional groups on Ti₃C₂T_x provide more nucleation sites for lithium.The Ti₃C₂T_x has a synergistic effect with rGO to jointly improve the adsorption energy of lithium and reduce the energy barrier of lithium transfer between the layers,which induces the uniform deposition and lateral growth of lithium between the layers,and suppresses dendrite formation.The symmetric cell assembled with Li-rGO/Ti₃C₂T_x composite electrode can be cycled stably for more than 1000 h at a current density of 10 mA cm^-2 without dendrite formation.In addition,the layered structure of rGO/Ti₃C₂T_x can prevent the direct contact between the polysulfide and the lithium metal in the lithium-sulfur full battery,protect the interlayer lithium metal from corrosion,which can also reduce the irreversible side reactions of the anode,thereby effectively alleviating the irreversible capacity loss of the cathode caused by the shuttle effect.The lithium-sulfur full battery with Li-rGO/Ti₃C₂T_x as the anode exhibits high cycle stability,after 300 cycles,the coulombic efficiency of the battery is still as high as 99.8%,and the surface of the anode is still flat,without dendrites and dead lithium.