Simultaneous Structure, Thermal, and Mechanics Regulation for Boosting Performance of PVDF-Based Solid-State Electrolytes

Poly(vinylidene fluoride) (PVDF) is promising for polymer solid-state electrolytes (PSEs) but faces challenges such as low ionic conductivity, uneven strain distribution, and poor lithium (Li) dendrite inhibition. Herein, an effective strategy is proposed to enhance PVDF-based PSEs by incorporating a fast ion conductor LiZr₂(PO₄)₃ (LZP) with a negative thermal expansion property and a NASICON-type structure, and the effects are investigated using multifarious methods. The added LZP not only enhances the mobility of the PVDF chain and the concentration of free Li⁺, but regulates heat release and volume expansion of PSEs during cycles, thereby protecting electrode morphology and structure, as well as improving the interface between the electrode and electrolyte. Compared to the pristine PVDF-based PSEs, the ionic conductivity is increased to 3.3 × 10^-4 S cm^-1, and the stability is augmented by adding 10 wt % LZP. At 25 °C and 0.5 C, the values of the discharge capacity retention of the Li|PVDF-10 wt %LZP|LiFePO₄ and Li|PVDF-10 wt %LZP|LiNi_0.8Co_0.1Mn_0.1O₂ full cells without liquid electrolytes are improved from 61.4 and 53.4% to 90.4 and 87.7% after 300 and 200 cycles, respectively. The enhancement mechanisms are proposed based on the interactions of heat, deformation, interface, and ion transfer. It paves a unique way to develop solid-state electrolytes by simultaneously adjusting the structure, heat, and mechanics.