Enhancement of Li+ Transport Through Intermediate Phase in High-Content Inorganic Composite Quasi-Solid-State Electrolytes

Abstract Quasi-solid-state electrolytes, which integrate the safety characteristics of inorganic materials, the flexibility of polymers, and the high ionic conductivity of liquid electrolytes, represent a transitional solution for high-energy-density lithium batteries. However, the mechanisms by which inorganic fillers enhance multiphase interfacial conduction remain inadequately understood. In this work, we synthesized composite quasi-solid-state electrolytes with high inorganic content to investigate interfacial phenomena and achieve enhanced electrode interface stability. Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 particles, through surface anion anchoring, improve Li + transference numbers and facilitate partial dissociation of solvated Li + structures, resulting in superior ion transport kinetics that achieve an ionic conductivity of 0.51 mS cm −1 at room temperature. The high mass fraction of inorganic components additionally promotes the formation of more stable interfacial layers, enabling lithium-symmetric cells to operate without short-circuiting for 6000 h at 0.1 mA cm −2 . Furthermore, this system demonstrates exceptional stability in 5 V-class lithium metal full cells, maintaining 80.5% capacity retention over 200 cycles at 0.5C. These findings guide the role of inorganic interfaces in composite electrolytes and demonstrate their potential for advancing high-voltage lithium battery technology.