Enhancement of Li<sup>+</sup> 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_1.3Al_0.3Ti_1.7(PO₄)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.