Facile synthesis of antimony-embedded nitrogen-rich carbon composites using sacrificial template: Enhanced stability for high-performance sodium-ion hybrid capacitors

Sodium-ion hybrid capacitors (SIHCs) offer a cost-efficient, high-energy, high-power solution for next-generation energy storage. The primary challenge is the development of suitable active materials. Ideal anodes should possess high capacity, low operating voltage, excellent rate performance, and cycling stability. In particular, alloy-based materials have the potential to serve as efficient anodes if their volume changes during cycling can be suppressed. In this work, we developed a facile and simple approach for the synthesis of alloy-based Sb nano-particles embedded in a nitrogen-enriched carbon matrix (denoted as Sb@NC) through a straightforward chelation process. By incorporating NaCl as a sacrificial template, we successfully reduced the overall size of the carbon matrix, further mitigating volume change during charge-discharge process, and formed pores in the composite that facilitate the transport of sodium ions (denoted as s-Sb@NC). The material exhibited a high capacity (544.4 mAh g-1@0.1 A g-1), superior rate performance (238.9 mAh g-1@5 A g-1), and robust stability, with the capacity of 224.2 mAh g-1 after 1000 cycles. Through in-situ analyses, we determined the char-ge-discharge mechanism, and ex-situ cross-sectional imaging revealed the causes behind the decreased performance of commercial Sb and Sb@NC with the progress of the charge-discharge cycle. SIHC device was assembled with our developed materials and activated carbon and it exhibited outstanding energy/power density and cycle stability compared with recently reported results. SHIC delivered a maximum energy and power density of 192.6 Wh kg- 1 and 18.6 kW kg -1, and showed a capacity fade of only 0.0028 % per cycle over 20,000 cycles at a high current density of 5 A g-1.