Despite of the good stability with Li-metal, Li6.75 La3 Zr1.75 Ta0.25 O12 (LLZTO) suffers from large interfacial resistance and severe Li-metal penetration. Herein, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO was developed, with the reducible Ti-LLZTO layer contacting Li-metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti-LLZTO and LLZTO enables a seamless contact and a barrierless Li+ transport between them. The densities of Ti-LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and a mixed ion-electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm-2 .
Keywords: Li metal anode; interface; mixed ion-electron conductors; multi-layer ceramic; solid state batteries.
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