Core-Shell Nanofiber Containing Large Amount of Flame Retardants via Coaxial Dual-Nozzle Electrospinning as Battery Separators

TL;DR

This study presents a novel coaxial electrospinning method to produce core-shell nanofiber separators with over 60% flame retardants, enhancing safety in lithium-ion batteries without sacrificing performance.

Contribution

Developed a dual-nozzle coaxial electrospinning technique to significantly increase flame retardant content in battery separators, improving safety and maintaining electrochemical performance.

Findings

Achieved over 60 wt.% flame retardants in nanofibers.

Battery cells with these separators show excellent flame retardancy.

The nanofiber separators maintain cycling stability and rate performance.

Abstract

Lithium-ion batteries have attracted enormous interests recently as promising power sources. However, the safety issue associated with the employment of highly flammable liquid electrolyte impedes the further development of next-generation lithium-ion batteries. Recently, researchers reported the use of electrospun core-shell fiber as the battery separator consisting of polymer layer as protective shell and flame retardants loaded inside as core. In case of a typical battery shorting, the protective polymer shell melts during thermal-runaway and the flame retardants inside would be released to suppress the combustion of the electrolyte. Due to the use of a single precursor solution for electrospinning containing both polymer and flame retardants, the weight ratio of flame retardants is limited and dependent. Herein, we developed a dual-nozzle, coaxial electrospinning approach to fabricate the core-shell nanofiber with a greatly enhanced flame retardants weight percentage in the final fibers. The weight ratio of flame retardants of triphenyl phosphate in the final composite reaches over 60 wt.%. The LiFePO4-based cell using this composite nanofiber as battery separator exhibits excellent flame-retardant property without compromising the cycling stability or rate performances. In addition, this functional nanofiber can also be coated onto commercial separators instead of being used directly as separators.