PNNL

Abstract

Lithium (Li) metal polymer batteries (LMPBs) are a promising candidate of solid-state batteries with high safety. However, rare progress has been demonstrated so far in high voltage stability of polyethylene oxide (PEO) based polymer electrolytes for LMPBs. Herein, we revived the polymer-in-salt electrolyte (PISE) strategy based on the PEO-LiFSI system with EO/Li = 8 through a dry process to avoid the contamination of the residual solvent. The obtained PISEs exhibit quite different morphologies and coordination structures which greatly enhance the oxidative stability of polymer electrolytes. P(EO)1LiFSI has a low melting temperature, a high ionic conductivity at 60 ?C and an oxidative stability of ~4.5 V vs. Li/Li+ (overcoming the inherent low oxidative stability of PEO). With an effective interphase rich in inorganic species, in combination with good stability of the hybrid polymer electrolyte towards Li metal, the cycling stability of Li||LiNi1/3Co1/3Mn1/3O2 is greatly improved. The LMPB can retain 74.4% of capacity after 186 cycles at 60 ?C under the charge cutoff voltage of 4.3 V. The findings point out a promising strategy to develop high-voltage stable polymer electrolytes for high energy-density and safe LMPBs.