Stability of Li1.3Al0.3Ti1.7(PO4)3-Based Composite Electrolytes against Lithium Anodes Enhanced by Uniform Surface Coating of Two-Dimensional Graphene-like C3N4 on Particle Surfaces

All-solid-state lithium (Li) batteries have attracted considerable interest due to their potential in high energy density as well as safety. However, the realization of a stable Li/solid-state electrolyte (SSE) interface remains challenging. Herein, two-dimensional graphene-like C3N4 (g-C3N4) as a coating layer on Li1.3Al0.3Ti1.7(PO4)3 (LATP) electrolyte (LATP@CN) has been applied to construct the stable Li/SSE interface. The g-C3N4 layer is uniformly coated on the LATP surface using the in situ calcination method, which not only enhances the dispersibility of LATP particles in poly(ethylene oxide) (PEO) through the interaction between surface functional groups but also suppresses the side reactions between Li and LATP. The coating layer can effectively improve the interfacial stability. As a result, the conductivity and stability of the obtained composite solid-state electrolytes (CSEs) against Li are enhanced. The Li∥CSEs∥Li symmetric cells stably cycle for 670 and 600 h at 0.1 and 0.2 mA cm-2, respectively. The Li∥CSEs∥LiFePO4 cells stably cycle more than 100 times at 0.1 and 0.2 C with a capacity retention rate of about 86% and 88%, respectively. This work inspires a new strategy to avoid the reactions between LATP and Li.