Zr Interface-crossing in Al-doped Li 7 La 3 Zr 2 O 12 Based Solid State Cell

Abstract Garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) based solid electrolytes deliver a high ionic conductivity of ca. 10 -3 S/cm at room temperature, which demonstrate a promising application in developing better solid-state batteries. While, using a series of Al doped LLZO (Al-LLZO) solid electrolytes, postmortem analysis shows there is an obvious Zr ion interface-crossing diffusion from Al-LLZO to the LiFePO 4 cathode inside the cycled LiFePO 4 |Al-LLZO|Li solid batteries, although they exhibit a stabilized cycling performance and capacity retention between 2.0 and 4.25 V. This finding indicates that the electrochemical profile of the present solid-state batteries should have more complex processes than ever known, and the decoding of this inconspicuous instability should have higher priority before building solid state batteries.