Design of hybrid nanocomposite solid polymer electrolytes using nano lithium salt for enhanced ionic transport in solid-state lithium batteries

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-benzyl 7 (BF 3 Li) 3 nano lithium salt, and POSSPEG 13.3 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% POSSPEG 13.3 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 ( t ion = 0.99). A wide electrochemical stability window of ∼4.7 V vs. Li/Li⁺ is obtained. Solid-state LiFePO 4 /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.