Carbonyls Mediated Dual-Function Enables High-Performance Carbon Anodes in Ester-based Electrolyte

Constructing an "ether solid electrolyte interphase (SEI)"-like layer in ester electrolyte is highly attractive to realize excellent capacity and cycling stability for hard carbon anode, but has barely been mentioned yet. Herein, the hard carbon grafted by caffeic acid is developed via a surface reconstruction strategy, in which rich C═O moieties are introduced. Varied characterizations reveal that the existing C═O exhibits stronger adsorption energy on salt (PF₆ ^-) than solvent (e.g., EC and DEC), thus accelerating salt decomposition to produce a stable inorganic SEI layer. Besides, C═O moieties can also adsorb K-ions reversibly, accounting for a high capacitive contribution. Benefiting from the double merits of C═O moieties, the interfacial stability and surface properties of the optimized sample are greatly improved, and as a result, the reversible capacity can reach 462.7 mAh g^-1 (0.1 A g^-1 over 50 cycles) and rate performance is quite superior as well (321.8 mAh g^-1 at 2 A g^-1). Besides, a prolonged cycle life of over 2000 cycles is smoothly realized at 2 A g^-1 in ester-based electrolytes. This work provides insight into the electrochemical performance improvement of ester-based electrolytes via structure design.