Enhancing the ionic conductivity of PVDF-HFP/LLZTO composite solid electrolytes using alkaline neutralizing agents

Polymer-based solid electrolytes offer high safety, flexibility, and mechanical strength but suffer from low room-temperature ionic conductivity (10 ‐8 to 10 ‐6 S·cm ‐1 ), limiting their practical application in solid-state lithium batteries. This study incorporates Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) as an inorganic filler to enhance ion transport but addresses its tendency to form an insulating Li 2 CO 3 layer upon exposure to air. Surface modifications using polyacrylic acid (PAA) and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) were explored to mitigate this issue. PAA treatment improved ionic conductivity to 1.82 × 10 ‐4 S·cm ‐1 and expanded the electrochemical window to 4.7 V, while NH 4 H 2 PO 4 treatment increased conductivity to 1.39 × 10 ‐4 S·cm ‐1 but reduced the electrochemical window to 3.5 V. These findings highlight the effectiveness of surface modification in optimizing composite solid electrolytes for high-performance applications.