Enhancing Lithium ion conductivity and all-solid-state secondary battery performance in polymer composite electrolyte membranes with β-Crystalline-rich Poly(vinylidene fluoride) Nanofibers

Solid polymer electrolytes (SPEs) have been actively studied for all-solid-state lithium ion batteries (ASS-LIBs). Here we show high-performance SPEs based on lithium salt-containing crystalline poly(vinylidene fluoride) (PVDF) nanofibers. It first reveals that the higher β-phase crystallinity of the PVDF nanofibers gives composite SPEs with the higher ion conductivity (σ = 6.0 × 10−4 S cm−1 at 60°C) and the higher lithium ion transference number (tLi+ = 0.58 at 60°C). The PVDF nanofiber composite SPEs possess good electrochemical stability and mechanical durability as investigated in the galvano static constant current cycling tests (Li | PVDF/Li-16 Nf composite membrane | Li). The ASS-LIB composed of the PVDF nanofiber composite SPEs (Li | PVDF/Li-16 Nf composite membrane | LiFePO4) show outstanding rate capability and charge-discharge cycling behavior. Finally, multi-layered stacked batteries are fabricated to produce quintuple cell potentials of 17.0 V, promising future batteries that achieve high-voltage operation and high energy densities.