Chemically Driven Conformational Rearrangement of PVDF-Based Polymer Electrolyte to improve ionic conductivity for Long-cycling Lithium Metal Batteries

Abstract

Poly(vinylidene fluoride) (PVDF)-based solid polymer electrolytes (SPEs) have garnered widespread attention owing to the excellent thermal stability and film-forming ability. However, low ionic conductivity and interfacial side reactions limit their practical applications. Herein, we propose a chemically driven approach to induce molecular chain conformational rearrangement of PVDF, which possesses more highly polar β-phase to promote Li salt dissociation. And an interchain Li+ transportation pathway with low-energy-barrier is designed through synergy of strong coordinated Li+···-SO3– (in Nafion) and weak dipole -C-F···Li+ interaction. Thereby the ionic conductivity is enhanced to 1.81 mS cm–1. The transportation process is traced by 6Li and two-dimensional 1H spectrum, demonstrating that the proportion of Li+ transportation through the designed low-energy-barrier pathway increases from 44% to 79%. The strong coordinated Li+···-SO3– also promotes uniform Li+ diffusion and surface inorganic-rich interphases formation. The Li||Li symmetric cell achieves stable cycling for 7800 h at 0.1 mA cm–2. LFP||Li batteries undergo more than 2000 and 1400 cycles at 1 and 5 C, and NCM811||Li battery maintains a discharge capacity of 152 mAh g–1 at 500 cycles, respectively. Additionally, 1.3 Ah pouch cell passes the nail penetration test with high safety, which provides a novel strategy for designing SPEs.