Study On Optimizing The Interface Of Lithium Anode By Sandwich Garnet Ceramic Electrolyte

Lithium-ion batteries are rapidly taking root in electric vehicles,intelligent electronic devices and other fields.However,as the market with the requirements of high energy density lithium ion battery constantly raise,alone the ascension of the anode material to improve the energy density is still not fully meet the needs of the current energy storage.In terms of the cathode by using lithium metal anode to replace the current mainstream improve the energy density of carbon graphite anode can be impressively,is an effective way to realize the battery to improve the overall energy density.By using solid electrolyte with garnet structure,it not only solves the numerous safety risks caused by liquid electrolyte,but also improves the energy density by matching lithium metal anode due to its stability to lithium metal.However,the practical application of solid electrolyte system with garnet structure is mainly hindered by poor interfacial wettability with lithium anode and dendrite growth of lithium.In this paper,garnet-type solid electrolyte with high ionic conductivity was prepared by doping Ta and Ti element.Meanwhile,the problem of lithium-metal-anode/LLZO interface was solved by using sandwich type ceramic electrolyte,which successfully improved the interface wettability and inhibited the dendrite growth of lithium,and effectively improved the electrochemical performance.The main research contents are as follows:(1)A sandwich type ceramic electrolyte of Ti-LLZTO/LLZTO/Ti-LLZTO electrolyte is produced by doping Ti and Ta.The employment of the identical crystal structures of Ti-LLZTO with LLZTO enables a seamless contact and a barrier less Li+transport between them.The cycle life of the assembled Li/Ti0.25-LLZTO/LLZTO/Ti0.25-LLZTO/Li symmetric cell is greatly improved,which effectively inhibits the growth of lithium dendrites.With the help of Ti-LLZTO layer,long-cycle stable lithium plating/stripping was reached for a large areal capacity of 3.0 mAh cm-2.In addition,Li/Ti0.25-LLZTO/LLZTO/LiFePO4 cell cycles 100 times after charge and discharge,the discharge capacity retention rate is 96%,and the coulombic efficiency reaches more than 99%,showing good cycle stability.(2)Meanwhile,with an in-situ reduction of Ti-LLZTO by Li-metal,the electronic conductivity of Ti0.25-LLZTO after lithium insertion is 80 times higher than that before lithium insertion and the interfacial wettability was improved,a mixed ion-electron conducting layer was established.Both features would not only reduce defects/pores on interface,but also homogenizes the interfacial ionic/electronic flux,facilitating the reduction of interfacial resistance and suppression of dendrites.