Enhancing the interface stability of Li1.3Al0.3Ti1.7(PO4)3 and lithium metal by amorphous Li1.5Al0.5Ge1.5(PO4)3 modification

Li1.3Al0.3Ti1.7(PO4)3 (LATP) has become the focus of research because of its high ionic conductivity, high oxidation voltage, and low air sensitivity. However, Ti4+ is easily reduced by Li metal. In this paper, amorphous Li1.5Al0.5Ge1.5(PO4)3 (a-LAGP) is introduced as an interface modification layer, because LAGP has the small electrochemical potential difference and Ge4+ is more difficult to be reduced by Li. Radio frequency sputtering (RF sputtering) is adopted to modify the a-LAGP thickness less than 100 nm. Compared with crystalline LAGP layer, a-LAGP has a better effect on improving the interface stability of LATP and Li. With the a-LAGP film, the Li/a-LAGP/LATP/a-LAGP/Li symmetrical cell is still stable after 100 cycles with the over potential changing from 1 V to 3 V. The probable mechanism of the good stability between a-LAGP and Li are discussed.