Dielectric Polarization of a High-Energy Density Graphite Anode and Its Physicochemical Effect on Li-Ion Batteries

Abstract

The high energy density graphite anode for the commercial LIBs has critical problems on Li+-ion kinetics due to decreases both in electrode porosity and electrolyte permeability. To overcome issues, interfaces of graphite particles in the anode are polarized using poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) with the high dielectric constant (ε = 8.4), high solubility with lithium salt, and ability to trap a large amount of liquid electrolyte. The PVDF-HFP treatment promoted electrolyte permeability into the graphite electrode with a high mass loading of 13.8 mg cm–2 and a density of 1.7 g cc–1 (a current density over 5 mA cm–2) which particularly leads to an improvement of capacity retention from 77% of a bare electrode to 95% over 40 cycles. These achievements were attributed not only to the enhancement of the lithium-ion kinetics but also to the stable formation of a solid electrolyte interface (SEI) layer on the graphite surface.