Preparation And Performance Study Of Transition Metal Fluoride Modified Three-Dimensional Carbon Cloth For Lithium Metal Anode

Lithium metal is widely considered as one of the most promising anode materials due to its extremely high theoretical specific capacity(3860 m Ah g^-1)and extremely low electrode potential（-3.045 V vs.SHE）.However,due to uncontrollable dendritic growth,volume expansion,and interfacial side reactions,lithium metal negative electrodes may experience short circuits or even explosions during practical cycling,which seriously hinders their practical application.In order to solve the above problems,this paper selects commercial carbon cloth as the substrate for 3D current collector,and improves the lithium affinity of the carbon cloth by growing a transition metal fluoride nano sheet array,regulating the deposition behavior of metal lithium,ultimately making the composite lithium metal negative electrode have ultra-long cycle stability.CoF₂ nanosheet array modified carbon cloth（CoF₂@CC）was prepared by a simple liquid phase precipitation method combined with high temperature fluorination heat treatment.The nanosheet array increased the specific surface area of carbon cloth and generated Lif-rich SEI film in situ during the initial lithium nucleation process.Under the combined action of the two,the lithium deposition capacity can reach 12 m Ah cm^-2.In addition,the symmetrical battery assembled with the composite lithium metal anode has an ultra-long life of more than 9000 h at a current density of 1 m A cm^-2 and a cycle capacity of 1 m Ah cm^-2.The assembled half battery also exhibits good coulombic efficiency,which can still maintain about 99%after 410 cycles.Full battery matching Li Fe PO₄ positive electrode（Li@Co F₂@CC||LFP）exhibits excellent cycle stability and capacity retention,capable of stable cycling for 1000 cycles at 2 C,with a capacity retention rate of 92%.Based on the fluorinated monometallic metal,fluorinated bimetallic carbon cloth modified with Ni F₂/Co F₂ nanosheet array was prepared by hydrothermal method and high temperature fluorination heat treatment（Ni F₂/Co F₂@CC）.It was found that Ni F₂/Co F₂nanosheet array increased the specific surface area of carbon cloth.At the beginning of the lithium deposition process,Ni F₂ and Co F₂ react with lithium to form Li F rich SEI films,which play a regulatory role in the deposition behavior of lithium.Ni F₂/Co F₂@CC composite lithium metal anode assembly of symmetrical battery,with 5 m A cm^-2 high current density and 5 m Ah cm^-2 high cycle capacity with more than 5000 h cycle life.Whole battery assembled with Ni F₂/Co F₂@CC negative electrode and Li Fe PO₄ positive electrode（Li@Ni F₂/Co F₂@CC||LFP）exhibits ultra-long cycle stability,with a high capacity of 98 m Ah g^-1 after 3000 cycles at 2 C.In addition,a full battery matching Li Ni_0.9Co_0.05Mn_0.05O₂（NCM）ternary positive electrode（Li@Ni F₂/Co F₂@CC||NCM）has a capacity of 155 mAh g^-1 after 130 cycles（capacity retention rate of 80%）.