Hybrid Particle Size Template Method for Controllable Synthesis of Nitrogen-Doped Multilevel Porous Carbon as High-Rate Zn-Ion Hybrid Supercapacitor Cathode Materials.

Abstract

Achieving high rate performance without compromising energy density has always been a critical objective for zinc-ion hybrid supercapacitors (ZHSCs). The pore structure and surface properties of carbon cathode materials play a crucial role. We propose utilizing a hybrid particle size (20 and 40 nm) magnesium oxide templates to regulate the pore structure of nitrogen-doped porous carbon derived from the soybean isolate. The multilevel pore structure enhanced ion transport efficiency while also improving the utilization of micropores. Nitrogen doping and oxygen-containing functional groups enhanced the wettability of carbon materials with aqueous electrolytes and facilitated the chemisorption of Zn²⁺ on the carbon material surface. The nitrogen-doped multilevel porous carbon material (HT-NMPC-1/1) prepared with a 1 : 1 mass ratio of the two templates exhibited a specific capacity of 146.65 mAh g^-1 at 0.2 A g^-1. Moreover, the Swagelok cells assembled with HT-NMPC-1/1 and Zn foil achieved a high energy density of 121.5 W h kg^-1, high power output of 166 W kg^-1, and 93.09 % capacity retention after 8000 cycles at 2 A g^-1. Therefore, HT-NMPC-1/1 is a highly promising candidate for ZHSCs cathode materials. Furthermore, the novel pore regulation strategy and straightforward preparation method offer valuable reference points for other porous carbon-based functional materials.