Regulating Interphase Chemistry by Targeted Functionalization of Hard Carbon Anode in Ester-Based Electrolytes for High-Performance Sodium-Ion Batteries

Commercial hard carbon (HC) anode suffers from unexpected interphase chemistry rooted in the parasitic reactions between surface oxygen-functional groups and ester-based electrolytes. Herein, an innovative strategy is proposed to regulate interphase chemistry by tailoring targeted functional groups on the HC surface, where highly active undesirable oxygen-functional groups are skillfully converted into a Si−O−Si molecular layer favorable for anchoring anions. Then, an inorganic/organic hybrid solid electrolyte interphase with low interfacial charge transfer resistance and enhanced cycling durability is constructed successfully. Consequently, the modified HC anode delivers an excellent rate capability of 206.2 mAh g⁻¹ at 0.5 A g⁻¹ and a remarkable capacity retention of 92.5 % after 1000 cycles at 1.0 A g⁻¹. Moreover, the coin-type full-cell equipped with Na₂Fe[Fe(CN)₆] cathode exhibits an exceptional capacity retention ratio of 80.9 % after 800 cycles at 1C. The present simple and effective interfacial modification strategy offers a promising and alternative avenue for promoting the development and practicability of HC anode in ester-based electrolytes for sodium-ion batteries.