Heterojunction Ferroelectric Materials Enhance Ion Transport and Fast Charging of Polymer Solid Electrolytes for Lithium Metal Batteries

Abstract

Solid polymer electrolytes offer great promise for all-solid-state batteries, but their advancement is constrained due to the low ionic conductivity at ambient temperature and non-uniform ion transport, which hampers fast-charging capabilities. In this study, a ferroelectric heterojunction composite is incorporated into poly(vinylidene difluoride) (PVDF) based solid electrolytes to establish an interfacial electric field that enhances lithium salt dissociation and promotes uniform ion deposition. Electrospun 1D BaTiO₃ nanofibers serve as a long-range organic/inorganic (polymer/filler) interface for ion transport, while MoSe₂ hydrothermally grown on BaTiO₃ forms Li₂Se-rich high-speed ion conductors. The piezoelectric effect of the ferroelectric material helps suppress lithium dendrite growth by reversing internal charges and reducing local overpotentials. Consequently, the PVBM electrolyte achieves a substantia ionic conductivity of 6.5 × 10⁻⁴ S cm⁻¹ and a Li-ion transference number of 0.61 at 25 °C. The LiFePO₄/PVBM/Li solid-state batteries demonstrate an initial discharge capacity of 146 mAh g⁻¹ at 1 C, with a capacity preservation of 80.2% upon completion of 1200 cycles, and an initial discharge capacity of 110.7 mAh g⁻¹ at 5 C. These findings highlight the prospect of ferroelectric ceramic fillers to significantly improve ion transport and fast-charging performance in polymer electrolytes.