Effect of acid treatment of Li7La3Zr2O12on ionic conductivity of composite solid electrolytes

Abstract

The garnet-type metal oxide Li7La3Zr2O12(LLZO) is considered to be one of the most promising compounds for solid lithium ion batteries because of its high ionic conductivity at room temperature and excellent chemical stability with the metal Li. LLZO is unstable in humid air and easily forms Li2CO3 on the surface, which leads to the decrease of ion conductivity. In this paper, chemical treatment by oxalic acid is carried out to remove the lithium carbonate on the surface of LLZO. The results show that oxalic acid with a concentration ratio of 5% can completely remove lithium carbonate. Composite polymer electrolyte membranes fabricated by the polyvinylidene fluoride (PVDF)and LLZO before and after the acid treatment are prepared to evaluate the effect on ionic conductivity. The ionic conductivity is 1.4×10-4 Scm-1 and 9.0×10-4 S cm-1 for samples added the LLZO before and after the acid treatment, respectively.