Controllable Interfacial Neutralization for Enhanced Interfacial Compatibility in Composite Solid-State Electrolytes

Poly(vinylidene fluoride) (PVDF)-based composite solid-state electrolytes (CSEs) have high application value in the field of solid-state electrolytes due to their high dielectric constant, excellent electrochemical stability, and thermal stability. However, compatibility issues between the polymer matrix and inorganic filler have hindered the development of CSEs. Furthermore, PVDF is prone to dehydrofluorination in alkaline environments, which exacerbates the agglomeration of inorganic filler and decreases the electrolyte’s overall performance. Herein, a controlled treatment of the surface of inorganic ceramic filler Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is carried out by an appropriate amount of introducing acetic acid (HAc), thereby efficiently removing Li2CO3 from the surface of LLZTO and precisely adjusting the pH of the electrolyte slurry. Moreover, the distribution of LLZTO in the polymer matrix is significantly improved, enhancing the mechanical strength of the electrolyte membrane and optimizing the Li+ transport path. The optimized CSEs exhibit high room-temperature ionic conductivity of 0.577 mS·cm–1 and enhance compatibility with the lithium metal anode. The lithium symmetric battery can be stably cycled at 0.1 mA·cm–2 for 1750 h. The LiFePO4∥Li full battery exhibits good stability at 1C, with an initial specific discharge capacity of 138.4 mAh·g–1 and a capacity retention of 94.9% after 200 cycles and 70.6% after 500 cycles. This study provides a simple and effective solution to optimize the preparation process and improve the overall performance of CSEs.