Ferroelectric BiFeO3 modified PVDF-based electrolytes for high-performance lithium metal batteries

Abstract

PVDF-based electrolytes are promising candidates for solid-state lithium batteries (SSLBs) due to their high safety, interface compatibility and electrochemical stability. However, the low ionic conductivity of PVDF and uncontrollable dendrite growth in the related SSLBs restrict their development and application. Herein, ferroelectric BiFeO₃ is introduced into PVDF to improve its electrolyte performance. The developed PVDF-based composite electrolytes achieve a high ionic conductivity (1.39 × 10⁻⁴ S cm⁻¹) and Li⁺ transference number (0.35). Benefitting from the introduced BiFeO₃, the assembled Li symmetrical batteries exhibit good cycle performance and can steadily cycle for 2500 h at 0.1 mA cm⁻², at 25 °C. Matched with LiNi_0.8Co_0.1Mn_0.1O₂ cathodes, the assembled batteries show excellent long-term cycling stability with a capacity retention of 94% after 100 cycles at 0.1C and capacity retention of 89% after 400 cycles at 0.3C. The ferroelectric effect of BiFeO₃ restrains the inhomogeneous electric field and adjusts the Li⁺ distribution at the electrolyte/electrode interface, achieving uniform Li deposition. The ferroelectric BiFeO₃ powder facilitates the decomposition of lithium salts and regulates the chemical composition of the solid electrolyte interphase (SEI).