Ester-Enhanced Inorganic-Rich Solid Electrolyte Interphase Enabled Dendrite-Free Fast-Charging Lithium Metal Batteries

Building lithium fluoride (LiF)-rich solid electrolyte interphases (SEIs) by the decomposition of fluorinated salts has been widely adopted to be effective to suppress lithium dendrite growth, thus prolonging the lifespan of fast-charging lithium metal batteries (LMBs). Nevertheless, the slow dissociation of LiF salts reduces both their utilization and the formation of inorganic SEI. Herein, cellulose acetate (CA) was incorporated into the electrolyte to create an inorganic-rich SEI through ester groups, where the lithiophilic oxygen atoms in the ester group (C═O) enhanced lithium-ion diffusion and anion dissociation rates. Therefore, rapid ion diffusion and dendrite-free anodes were achieved in the ester-based electrolyte with CA (named as CA-E). As a result, the lithium symmetric batteries with the CA-E electrolyte exhibited stable cycling performance for 5,000 h at a current density/capacity of 3 mA cm⁻²/1 mAh cm⁻², while a short-circuiting was observed after ~450 h for the bare electrolyte. Benefiting from the rational design, lithium iron phosphate batteries with the CA-E electrolyte showed an excellent C-rate performance with a capacity of 100.7 mAh g⁻¹ at the rate of 10 C. Moreover, a specific capacity of 110.3 mAh g⁻¹ was maintained after 300 cycles at the rate of 6 C with a Coulombic efficiency of 99.87%. This work proposes a new approach to dendrite inhibitors for fast-charging LMBs.