Kinetically well-matched dual-carbon electrodes derived from poly(aniline-co-pyrrole) hollow nanospheres for advanced sodium-ion capacitors

Abstract

Kinetically matched electrode design is key to enhancing the high energy–power characteristics of dual-carbon sodium-ion capacitors (SICs). In this study, poly (aniline-co-pyrrole) (PACP) hollow nanospheres are used as a homogenous precursor to synthesize N/O co-doped hard carbon negative electrodes and porous carbon positive electrodes, enabling well-matched kinetic behavior between the negative and the positive electrodes. The results show that when the carbonization temperature is optimized to 1300 °C, the resulting hard carbon hollow nanospheres (HCHNS-1300) exhibits an optimal degree of graphitization suitable for sodium-ion storage, delivering a reversible capacity of 259 mAh g⁻¹ at 0.1 A g⁻¹ and maintaining 70 % capacity retention after 10,000 cycles at a high rate of 2 A g⁻¹. For the positive electrode, adjusting the mass ratio of PACP to the activating agent of potassium citrate (1:4) yields porous carbon hollow nanospheres/nanosheets (PCHNS-4) with a high defect density and specific surface area (1947 m² g⁻¹), significantly improving the kinetics of ions adsorption/desorption. The SIC device assembled with this dual-carbon electrode system delivers a specific energy of 92.5 Wh kg⁻¹ at a specific power of 249.7 W kg⁻¹. Notably, even at an ultra-high specific power of 11,869.5 W kg⁻¹, it still retains a specific energy of 82.4 Wh kg⁻¹. The kinetic matching between the negative and positive electrodes is induced by N/O co-doping and homologous-derived hierarchical porosity engineering. This study offers an integrated material–structure–function strategy for the rational design of kinetics well-matching dual-carbon electrodes for SICs.