Research On Dendrite Suppression Strategies For Lithium Anode

Lithium metal is considered to be one of the potential materials for the negative electrode of high energy density batteries in the future,with high energy density（3860m Ah g-1）and low reduction potential（-3.04 V vs NHE）.However,the problem of lithium dendrite growth and low coulombic efficiency limit the use of lithium on the commercialization.In view of the problems of lithium anode,the paper carried out research work from two aspects:the surface modification of lithium anode and the design of gel polymer electrolytes.Committed to reducing the contact between the lithium anode and electrolyte,promoting the uniform deposition of Li⁺and reducing the expansion effect of anode,inhibiting the growth of lithium dendrites and improving the cycle life and coulomb efficiency.（1）The specific mechanism of Li Zn alloy layer inhibiting lithium dendrites was understood from a thermodynamic point of view in this chapter.Theoretical calculation results showed that the alloy layer provides a smaller diffusion barrier for the diffusion of lithium atoms and reduces the opportunity of lithium dendrite growth.On this basis,an alloy-polymer composite layer was prepared on the surface of lithium metal to protect the lithium anode and improve the lithium deposition behavior.Alloy-polymer protective layer with dense surface can effectively isolate negative side reaction.In addition,the alloy component in the protective layer provided a fast transmission channel and high diffusion rate for lithium ions.The polymer component relieved the stress caused by lithium deposition,can effectively promote the uniform deposition of lithium ions,inhibited the growth of lithium dendrites,and improved the surface deposition of lithium metal morphology and electrochemical performance.At a current density of 1.0 m A cm^-2,the lithium anode protected by the alloy-polymer composite layer ran stably for 1700 times and still maintain a small polarization voltage.At a larger current density(2.0 m A cm^-2,3.0 m A cm^-2),it also showed a relatively stable deposition voltage and long cycle life.The Li||Li Fe PO₄ full cell had an initial discharge specific capacity of 165 m Ah g^-1 at a charge-discharge rate of 1C and a capacity retention rate of 75%after 750 cycles.（2）Gel polymer electrolyte was prepared by in-situ thermal polymerization instead of liquid electrolyte to reduce the corrosion of lithium metal by liquid electrolyte.The protective effect of different contents of DME on lithium metal anode was investigated.The gel polymer electrolyte has good mechanical strength and high decomposition voltage.The introduction of DME improved the Li⁺conductivity of the gel polymer electrolyte.The results showed that the gel polymer electrolyte containing10%volume fraction DME shows the best electrochemical performance.Under the current of 0.5 m A cm^-2,the Li||Li symmetric cell cycled steadily for 1400 h and maintained a polarization voltage of 50 m V.At the rate of 0.5C,the Li||Li Fe PO4 full cell cycles ran stably for 1700 times without obvious capacity attenuation.