Enhancing low-temperature electrolyte performance through intermittent discharge for improved LiODFB additive film formation

The challenge of improving low-temperature performance in lithium-ion batteries (LIBs) is attributed to the formation of an unstable solid electrolyte interphase (SEI) film. Lithium difluoro(oxalate)borate (LiODFB) has demonstrated potential in enhancing capacity retention and reducing impedance at low temperatures by establishing a high ion conductivity and stable SEI layer. Previous research indicates that the BOF2- anion, a soluble product of film formation additive of LiODFB hinder salt decomposition by aggregating on the electrode surface. This study presents a strategy to intensify the film formation process of LiODFB additives by introducing an optimal standing time during intermittent discharge processes. Three specific stages of soluble product diffusion are discussed. Diffusion starts from the outer layer of adsorption composed of soluble substances, gradually extends to the inner layer of adsorption, and finally establishes a new connection with the electrode. A brief standing time proves insufficient for inner adsorption layer diffusion, while excessively extended standing time fails to accelerate LiODFB decomposition. A standing time of 2300 s is selected to promote a stable SEI layer. This strategy elevates the capacity retention rate of cells at -20 degrees C from 66.59 % to 84.44 %. The study offers a method to address battery performance degradation in low-temperature conditions.