Improving electric field strength of interfacial electric double layer and cycle stability of Li-ion battery via LiCl additive

Abstract

Many works have focused on building an improved solid electrolyte interface (SEI) film by consuming additives during the first several cycles. However, the effects of electric double layers (EDLs) on interface chemistry are often overlooked. Here in, experimental and calculated results have proved the anion-building EDLs have a stronger electric field than the one by Li+ ions, resulting in more generation of protective LixPFyOz compounds. Specifically, the small volume anions to the benefit of improving the electric field of EDLs. Based on this finding, the electrolyte additive of LiCl with the property of small molecular volume is introduced to stabilize SEI films. As expected, it strengthens the electric field, facilitates the self-decomposition of PF6− anions, contributes to a moderate increase in the quantity of LixPFyOz product, and improves the cycle stability of Li-ion batteries. We expect that the method which adjusts the interfacial property by introducing non-consumed small anions provides a new trail in screening and designing electrolyte additives for advanced batteries.