Facile synthesis of N,O-codoped hard carbon on the kilogram scale for fast capacitive sodium storage

Abstract

Hard carbon has been identified as a promising anode material for sodium-ion batteries (SIBs). Herein, a facile self-templating strategy has been developed for the kilogram-scale preparation of N,O-codoped hierarchical porous hard carbon cuttlefish-like nanowire bundles (denoted as NOHPHC cuttlefishes). The unique nanoarchitecture leads to ultrafast pseudocapacitive sodium storage, excellent reversibility, and negligible degradation of the host material. NOHPHC delivers a high reversible capacity of 184 mA h g⁻¹ at 0.5 A g⁻¹, which is maintained at 114 mA h g⁻¹ at 5 A g⁻¹ for over 30 000 cycles, as well as exceptional rate capability of up to 20 A g⁻¹ with a capacity of approximately 100 mA h g⁻¹. Importantly, samples prepared before and after kilogram scaling are comparable in performance. Coupled with a Na₃V₂(PO₄)₃/C cathode, a full cell successfully obtains a high energy density of 52.6 W h kg⁻¹ at 50 W kg⁻¹ and 34 W h kg⁻¹ at 1.4 kW kg⁻¹.