Manipulating Interphase Chemistry by Endogenous Doping Toward High-Performance Hard Carbon Anodes for Sodium-Ion Batteries

The practical of hard carbon (HC) anodes in sodium-ion batteries is primarily limited by their unsatisfactory initial coulombic efficiency (ICE), cycling stability and rate performance, which are closely related to their interphase chemistry and microstructure. Herein, a unique manipulating interphase chemistry strategy by endogenous N/S doping is proposed to simultaneously achieve the both issues. Specifically, a series of reducing sugars and amino acid have been proven to trigger the Maillard reaction, thereby enabling endogenous N/S doping and microstructural design for HC anodes. Endogenous doping facilitates the formation of an inorganic-enriched solid–electrolyte interface (SEI) layer on cycled HC, which can effectively accelerate ion transport kinetics and reduce side effects for enhanced rate, ICE, cycling performance and reversible capacity. Meanwhile, the increase in the number of closed pores boosts both the platform capacity and cycling stability of HC. Consequently, the features HC anodes demonstrate a splendid reversible capacity (363 mAh g−1 at 0.05 A g−1), superior cycling performance (over 2500 cycles with 79% retention at 5.0 A g−1) and adequate ICE (89%). The assembled full cell with Na3V2(PO4)3 cathode exhibits splendid cycling stability over 700 cycles with capacity retention of 89.2% at 1 C. Surprisingly, the pouch cell with high cathode mass loading of 20.7 mg cm−1 maintains 98.1% capacity retention after 175 cycles at 1 C. This strategy provides new ideas and insights for the design and screening of high-performance HC anodes.