Marrying Ester Group with Lithium Salt: Cellulose‐Acetate‐Enabled LiF‐Enriched Interface for Stable Lithium Metal Anodes

Abstract The practical applications of high‐energy‐density lithium (Li) metal batteries (LMB) have been hindered by the formation and growth of Li dendrites. Homogenizing the Li‐ion flux to suppress Li dendrites by regulating the solid electrolyte interphase (SEI) originating from electrolyte degradation is necessary but still challenging. Herein, ion‐affiliative cellulose acetate (CA) with functional Li salts is prepared to generate the SEI with fast Li + diffusion kinetics. First, the correlations between the functional ester group and LiN(CF 3 SO 2 ) 2 (LiTFSI) are theoretically and experimentally identified, where CO strongly adsorbed N(CF 3 SO 2 ) 2 − through electrostatic interaction to enhance the charge‐transfer‐promoted decomposition of LiTFSI. Furthermore, the CA with ex situ doped LiTFSI amplifies this fluorinated degradation effect, and the LiF‐enriched SEI nanostructure is consequently established in situ, as confirmed by cryogenic transmission electron microscopy. As a result, the dendritic Li growth during cycling is efficiently suppressed, and the lifespan is prolonged by more than six times at a high current density of 3 mA cm −2 . This study provides insights into the interphase design for realizing ultrastable LMB.