A Multilayer Ceramic Electrolyte for All-solid-state Li Batteries.

Garnet structured solid-state electrolytes Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO), despite of the advantages of good chemical stability with Li-metal and high ionic conductivity, suffers from large interfacial resistance and quick short circuit owing to a poor wettability with Li-metal and severe Li-metal growth on both interface and inside. To address these issues, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO electrolyte was developed with the electrochemically reducible Ti-LLZTO layer contacting the Li-metal and the LLZTO layer contacting the cathode. The employment of the identical crystal structures of Ti-LLZTO with LLZTO enables a seamless contact and a barrier less Li + transport between them. In the same preparation condition, the densities of Ti-LLZTO pellets are obviously higher than that of the undoped LLZTO. In addition, with an in-situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and 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. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached for a large areal capacity of 3.0 mAh cm -2 .