Lithium-ion batteries utilizing solid-state electrolytes have potential to alleviate safety issues, prolong discharge/charge cycle life, reduce packaging volume, and enable flexible design. Polymer-ceramic composite electrolytes are more attractive and recognized because the combination can remedy and/or transcend individual constituent’ properties. We have fabricated a series of free-standing composite electrolyte membranes consisting of L_i1.4Al_0.4Ge_1.6(PO₄)₃ (LAGP), polyethylene oxide (PEO), and two different lithium-salts, i.e. LiBF₄ and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). It is determined that the type of lithium salt can prevail the ceramic LAGP loadings on altering the thermal, mechanical, and electrical properties of the composite electrolytes.

In this paper, we will present the results and discuss the differences in the aspects of melting transition, mechanical reinforcement, and ionic conduction resulting from the two different lithium salts together with the content of LAGP ceramic fillers in the lithiated PEO/LAGP composite electrolytes. The changes in these three aspects can be ascribed to the different interactions between the polymer matrix and lithium salt in the composite setting.