Ammonium persulfate assisted synthesis of ant-nest-like hierarchical porous carbons derived from chitosan for high-performance supercapacitors and zinc-ion hybrid capacitors

Abstract

Effectively preserving the high specific surface area and diverse heteroatom functional groups of biomass-derived porous carbons is crucial, but there is still work to be done in developing energy storage technologies with high-rate survival and superior, long-lasting capacitive activity. Herein, we report an efficient method for ammonium persulfate assisted synthesis of ant-nest-like hierarchical porous carbons (AH-PCs) originating from chitosan for superior-quality supercapacitors and zinc-ion hybrid capacitors (ZIHCs). The extensive cross-linking of chitosan results in an ant-nest-like hierarchical structure and a high specific surface area of 3518 m² g⁻¹, with 83.48% micropores, ideal for ion transport. The AH-PCs exhibit a high heteroatom (N and O) content of 21.49%. Employed as electrode materials for supercapacitors, the AH-PCs exhibit an extremely high 500 F g⁻¹ specific capacitance in a 6 M KOH electrolyte. With a remarkable capacity retention rate of 71.65%, the symmetric supercapacitor produces a high capacitance of 329.4 F g⁻¹ at a 0.5 A g⁻¹ discharge rate, and it retains 236 F g⁻¹ even at 20 A g⁻¹. Impressively, after 400 000 cycles at 10 A g⁻¹, the capacity retention rate remains at 94.9%, with an average loss of just 0.00001275% per cycle. In a 1 M Na₂SO₄ electrolyte, a high energy density of 37.69 W h kg⁻¹ can be achieved at 225 W kg⁻¹. Used as positive electrode materials of ZIHCs, a high energy density of 137.61 W h kg⁻¹ can be yielded. Remarkably, even after 20 000 cycles at a high current density of 20 A g⁻¹, the capacity retention rate remains at 100% with an ultra-low self-discharge rate of 2.67 mV h⁻¹. These exceptional electrochemical properties hold significant promise for advanced supercapacitors and ZIHCs.