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Abstract:
Solid polymer electrolytes with high ionic conductivity, dominant ion transport, and long-term electrochemical stability are essential for next-generation solid-state lithium batteries. In this study, a fully hybrid nanocomposite solid polymer electrolyte based on poly(ethylene oxide) (PEO), POSS-benzyl7(BF3Li)3 nano lithium salt, and POSSPEG13.3 nano plasticizer is developed using solution casting technique, in which both the salt and plasticizer possess organic–inorganic hybrid architectures. The optimized electrolyte containing 40 wt% POSSPEG13.3 exhibits a high room-temperature ionic conductivity of 8.64 × 10−4 S cm⁻¹ and follows Vogel–Tammann–Fulcher (VTF) behavior. Structural and thermal analyses reveal near-complete suppression of PEO crystallinity (∼1%) and good thermal stability up to ∼235 °C. The electrolyte shows excellent mechanical flexibility and a near-unity ion transference number (tion = 0.99). A wide electrochemical stability window of ∼4.7 V vs. Li/Li⁺ is obtained. Solid-state LiFePO4/Li cells deliver an initial discharge capacity of 169.3 mAh g⁻¹ at 0.1 C with 89.8% capacity retention after 100 cycles. These results demonstrate the effectiveness of the fully hybrid electrolyte design for solid-state lithium batteries.

Keywords:
Solid polymer electrolyte, POSS lithium salt, Nano plasticizer, Ion transference number, Solid-state lithium batteries