Manipulating interphase chemistry by endogenous doping toward high‑performance hard carbon anodes for sodium‑ion batteries

As the demand for sustainable energy storage continues to grow, sodium-ion batteries have emerged as promising alternatives to lithium-ion systems due to abundant sodium resources and cost-effectiveness. However, the commercial development of hard carbon anodes has been hindered by compromises in initial coulombic efficiency, reversible capacity, rate capability, and cycle life. Now, researchers from Central South University, led by Professor Anqiang Pan and Professor Shuang Zhou, have presented an innovative solution inspired by the Maillard reaction principle.

Why This Strategy Matters

The Maillard reaction, commonly known in food chemistry, enables endogenous N/S doping by triggering reactions between reducing sugars and amino acids. This approach simultaneously addresses multiple performance bottlenecks: it facilitates formation of an inorganic-rich solid-electrolyte interphase layer that accelerates ion transport kinetics, while increasing closed pore density to enhance platform capacity and cycling stability without sacrificing initial coulombic efficiency.

Innovative Design and Features

The hard carbon anode (1300-FCA) achieves an expanded interlayer spacing of 0.388 nm and demonstrates a remarkable reversible capacity of 363 mAh g^-1 at 0.05 A g^-1. The homogeneous SEI layer, rich in inorganic components including Na₂CO₃, Na₂O, and NaF, ensures fast Na⁺ diffusion and reduces side reactions. The material maintains low specific surface area while providing abundant Na⁺ storage sites through optimized microstructural design.

Applications and Performance

The assembled full cell with Na₃V₂(PO₄)₃ cathode exhibits excellent cycling stability over 700 cycles with 89.2% capacity retention at 1C, using an N/P ratio of 1.12. Impressively, a pouch cell with high cathode mass loading of 20.7 mg cm^-2 maintains 98.1% capacity retention after 175 cycles at 1C, demonstrating strong potential for commercial applications.

This comprehensive study provides valuable insights for developing next-generation hard carbon anodes through interdisciplinary research bridging food chemistry principles with advanced materials engineering.