Interface engineering of Li_1.3Al_0.3Ti_1.7(PO₄)₃ ceramic electrolyte via multifunctional interfacial layer for all-solid-state lithium batteries

Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) suffers from high interfacial resistance and instability with Li which hinder its application in all-solid-state lithium batteries. Herein, we propose an effective method to overcome these obstacles by introducing a LATP nanoparticle-reinforced composite polymer electrolyte (CPE) at LATP/Li interface. The multifunctional CPE interfacial layer can not only avoid side reactions between LATP and Li, but also ensure intimate contact at LATP/Li interface to reduce interfacial resistance. Moreover, the soft CPE layer can mitigate the large volume change of Li anode during cycling due to its high viscosity and flexible features. With the assistance of LATP fillers, the CPE interfacial layer can inhibit the formation and penetration of Li dendrites with enhanced mechanical strength and uniform Li deposition. After the modification of CPE interfacial layer, solid-state electrolyte with the sandwiched structure of CPE/LATP/CPE possesses satisfactory features such as high ionic conductivity, high interfacial stability and wide electrochemical window. Symmetric Li cell exhibits significant reduction in interfacial resistance (from 2852 Ω cm² to 505 Ω cm²) and overpotential (from 2.03 V to 0.04 V), which ensures a stable galvanostatic cycle for more than 400 h at 0.05 mA cm⁻². Solid-state LiFePO₄/LATP/CPE/Li batteries deliver remarkable cycling ability and high coulombic efficiency.