Fluorinated carbon nitride-assisted solvation-regulation engineering toward polyvinylidene fluoride-based electrolytes for long-lifespan solid-state lithium batteries

Abstract

Polyvinylidene fluoride (PVDF)-based electrolytes show huge potential in applications of solid-state lithium batteries (SSLBs) due to their broad potential windows and reliable mechanical strength. However, the critical interfacial problems associated with highly reactive residual solvents cause rapid deterioration in the stability of electrolytes toward long-term cycling. Herein, a solvation-regulation engineering method is proposed by introducing two-dimensional fluorinated C₃N₅ (F-C₃N₅) with a distinctive electronic structure to restrain residual solvents. The strong adsorption effect of F-C₃N₅ contributes to the selective capture of residual solvent, enabling more anions to participate in solvation by weakening the binding strength between Li⁺ and solvent. Both anion-rich solvation structures and F-C₃N₅ fillers are involved in forming inorganic-dominated cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) layers, which inhibit undesirable parasitic reactions occurring at electrode/electrolyte interfaces. Consequently, the integration of F-C₃N₅ with a PVDF-based electrolyte endows a Li symmetric cell with a high critical current density of 2.3 mA cm⁻², and stable Li plating/stripping cycling of 800 h at 0.5 mA cm⁻². The corresponding LiNi_0.6Co_0.2Mn_0.2O₂/Li cell delivers excellent capacity retention of 86.4% after 300 cycles at 1C. This work provides a novel perspective on using functionalized F-C₃N₅ to tailor solvation structures for the stabilization of PVDF-based electrolytes.