The design of LiTFSI-based poly(vinylidene fluoride)-poly(vinyl acetate) composite polymer electrolyte and its integrated membrane with electrodes

Abstract

Solid-state lithium metal batteries are promising energy storage devices. However, there are factors limiting their electrochemical performance and practical applications. These include the low ionic conductivity of solid-state electrolytes, poor electrode-electrolyte compatibility, inhomogeneous current density, and lithium dendrite growth problems. This work employs a straightforward slurry casting and drying technique to prepare composite polymer electrolytes (denoted as PVDF/AC) using the polyvinylidene fluoride (PVDF), polyvinyl acetate (PVAC), ‌Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and N,N-Dimethylformamide (DMF) as raw materials. The fabricated electrolyte membrane demonstrates a high ionic conductivity (1.73 × 10⁻⁴ S cm⁻¹), an electrochemical stability window of approximately 4.67 V, and a favorable lithium ion transference number of 0.51. Additionally, a straightforward cathode-solid electrolyte integration strategy is proposed to address the poor interface compatibility caused by solid-solid point contact. By employing this strategy, the integrated battery demonstrates reduced resistance (121.6 Ω), enhanced cycling stability (retaining a discharge capacity of 162 mAh/g at 0.5C after 170 cycles, with a capacity retention of 96.4 %), and superior rate performance in comparison to conventional batteries. It is anticipated that this integration strategy will be widely adopted to enhance the interfacial stability and electrochemical performance of all solid-state batteries.