Ionic conductivity enhanced by crown ether bridges for lithium-ion battery separators

Abstract

PVDF separator is more competitive for lithium-ion batteries (LIBs) due to its physicochemical and electrochemical stability. However, improvement of the ionic conductivity of PVDF separator remains challenging due to its lower affinity of electrolyte and higher crystallinity. In this work, 4′-aminobenzo-15-crown-5 (AB15C5, CE), which has befitting cavities (∼2.0 Å) with Li+ (∼1.6 Å), is introduced into electrospun PVDF nanofibrous separator as a bridge for enhancement of Li+ transport via mussel-inspired dopamine (DA) chemistry. In the as-prepared separators, attendance of CE in separator will reduce the crystallinity of PVDF. Besides, the energy barrier of Li+ transfer through separator obtained is reduced from 0.6 eV (PVDF separator) to 0.3 eV (CE modified separator) based on density functional theory (DFT) simulation. As a result, the ionic conductivity of the modified separator is increased from 0.59 to 2.77 mS·cm−1. Moreover, the modified PVDF separator exhibits improved hydrophilicity and wettability, thus effectively enhancing cycling and C-rate performances of lithium-ion batteries. This work will provide prospects for the development of high-performance separator for LIBs.