Insights into the effects of different inorganic fillers on the electrochemical performances of polymer solid electrolytes

Compared with polymer electrolyte, organic/inorganic composite solid electrolyte (CSE) shows greater advantage in solid lithium battery. The choice of inorganic filler in composition, morphology and conductivity determines the different electrochemical performance of CSE, which affects the ion migration and interface compatibility of electrolyte. Therefore, we compared inorganic fillers (LLZO particles, LLZO fibers, Al2O3 particles and Al2O3 fibers) into the polypropylene oxide (PPO) polymer to study the different effects of these four fillers on the properties of CSE. The results show that fibrous fillers have a long-distance ion transport path compared with particles, the active filler LLZO fiber has higher conductivity than the inert filler Al2O3 fiber, which greatly improves the ionic conductivity of the composite electrolyte (4.59 × 10−4 S cm−1). In addition, the existence of LiF component builds a high-strength solid electrolyte interface to protect lithium metal, especially the Li-Al-O formed at the interface of Al2O3 fiber better guarantees the stability of lithium, and solves the problem of dendrite growth and interface compatibility.