Dual regulation of structure and interface enabled high-rate and high-capacity hard carbon anode for sodium-ion batteries

Hard carbon (HC) is the most ideal commercial anode material for sodium-ion batteries (SIBs). The current research has made significant advances in the structural design of HC. However, the overall performance of SIBs is also contingent upon the properties of the anode interfacial layer. Therefore, it is essential to consider both the intrinsic structure and the development of the interfacial layer during the cycling of the hard carbon anode. Herein, we successfully synthesized chitosan-derived HC for high-rate and high-capacity SIBs through leveraging the regulatory effect of Zn on the carbon layer structure during the carbonization process, as well as the inducement of a stable SEI by residual Zn during battery cycling. Benefiting from the expanded interlayer spacing, the micropores formed by partial Zn evaporation at high temperatures and the high pyridinic-N content induced by the Zn-doped, it provides more channels for sodium-ion diffusion, lowering the diffusion barrier and offers a large specific capacity. Meanwhile, we confirmed that the Zn-doped adjusts the composition and structure of the solid electrolyte interphase (SEI), improved transfer kinetics. As a result, the optimized HC exhibits high specific capacity (390 mAh g-1) and excellent rate performance (162 mAh g-1 at 10 A g-1). This work provides a new perspectives on the modification of HC anodes to enhance sodium storage performance and further understanding for the regulation of HC by the Zn-doped.