Ba0.6Sr0.4TiO3 ferroelectric filler-reinforced poly(vinylidene fluoride) polymer electrolytes for dendrite-free solid-state Li metal batteries†

Polyvinylidene fluoride (PVDF)-based electrolytes have attracted significant attention for their potential use in solid-state lithium batteries (SSLBs) due to their superior electrochemical performance and safety. However, their low ionic conductivity and uneven lithium deposition hinder the further application of PVDF-based electrolytes. Herein, this work focuses on incorporating Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric ceramics into PVDF to form composite solid-state electrolytes (CSEs). The BST ferroelectric ceramics can create an intrinsic electric field that facilitates lithium-ion transport and enables uniform Li deposition. In addition, benefiting from the high dielectric constant of BST and dipoles generated from the asymmetric structure, PVDF–BST CSEs achieve a high ionic conductivity (1.79 × 10⁻⁴ S cm⁻¹) due to more free lithium ions, a wide electrochemical window of 4.8 V (vs. Li/Li⁺) and a high Li⁺ transference number (0.37). The assembled Li|PVDF–BST|Li symmetrical cells can steadily cycle for 1100 h at 0.1 mA cm⁻² at 25 °C. The assembled Li|PVDF–BST|LiFePO₄ cells show long-term cycling stability with a capacity retention of 85.6% after 100 cycles at 0.5C and a capacity retention of 81.4% after 200 cycles at 1C. This work provides a new strategy for improving the performance of the PVDF-based electrolytes by incorporating ferroelectric ceramics.