80 wt % LATP-Loaded Composite Electrolyte via Solution Casting: Enabling 5.6 V High-Voltage Solid-State Batteries

Ceramic-polymer composite electrolytes represent a transformative solution for addressing safety challenges in lithium metal batteries, combining inherent nonflammability with superior ionic conductivity and dendrite-suppression properties. This study demonstrates a breakthrough in electrolyte design by developing a high-loading composite membrane containing 80 wt % Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) within a PVDF-HFP matrix, fabricated via a simple and environmentally friendly solution-casting method. The optimized architecture features vertically aligned LATP particles creating continuous ion conduction pathways, achieving exceptional room-temperature performance: lithium ion transference number of 0.625, ionic conductivity of 5.23 × 10 –4 S·cm –1, and an extended electrochemical stability window up to 5.62 V vs Li + /Li. The dual-phase design enables remarkable interfacial stability, as evidenced by stable Li plating/stripping over 500 h at 0.1 mA cm –2 in symmetric cells. When paired with LiFePO 4 cathodes, full cells deliver an initial capacity of 158.64 mAh g –1 at 0.1C (25 °C) with 83.37% capacity retention after 100 cycles. This study establishes a paradigm for solid-state electrolyte engineering through synergistic microstructure control, resolving critical challenges in ceramic loading limits while maintaining interfacial compatibility - a crucial advancement toward practical high-voltage lithium metal batteries.