Li+ affinity ultra-thin solid polymer electrolyte for advanced all-solid-state lithium-ion battery

Abstract

The chasing for all-solid-state lithium-ion batteries (ASSLIBs) is based on the need for safer and higher energy density batteries. In this regard, solid polymer electrolytes (SPEs) are well-renowned for their processability and electrochemical stability, yet slimmer and more flexible SPE with higher ionic conductivity is still desired. Herein, an ultrathin (35 µm), rigidity-enhancing co-blending SPEs design using electrospinning was proposed, blending bio-polyamide with a N-substituted pyrrolidone ring (IBD) with polyethylene oxide/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI). IBD is confirmed to possess the dominant Li+ affinity. Then IBD with flexible chain segments of PEO, triggers a concerted ion-transport mechanism synergistically, in which IBD is responsible for the processes of enhanced ion-pair dissociation resulting in dynamic association between the mobile cations and the long-chain molecules that constitute the SPE. Meanwhile, it could broaden the ion transport channel in some extent. The ionic conductivity of the SPE is up to 4.26 × 10−4 S cm−1 at 50 ℃. Furthermore, the high strength modulus, low crystallinity, and ultra-thin characteristic of IBD-PEO/LiTFSI power-assisted the ASSLIBs of LiFePO4//Li to achieve extraordinary cycle performance (80.5 % capacity retention after 580 cycles at C/2 rate) and the average coulomb efficiency exceeds 99.5 % at 50 ℃. Moreover, it has the ability to withstand folding and bending conditions.