Evoking surface-driven capacitive process through sulfur implantation into nitrogen-coordinated hard carbon hollow spheres achieves superior alkali metal ion storage beyond lithium

Abstract

Owing to the specific merits of low cost, abundant sources, and high physicochemical stability, carbonaceous materials are promising anode candidates for K⁺/Na⁺ storage, whereas their limited specific capacity and unfavorable rate capability remain challenging for future applications. Herein, the sulfur implantation in N-coordinated hard carbon hollow spheres (SN-CHS) has been realized for evoking a surface-driven capacitive process, which greatly improves K⁺/Na⁺ storage performance. Specifically, the SN-CHS electrodes deliver a high specific capacity of 480.5/460.9 mAh g⁻¹ at 0.1 A g⁻¹, preferred rate performance of 316.8/237.4 mAh g⁻¹ at 5 A g⁻¹, and high-rate cycling stability of 87.9%/87.2% capacity retention after 2500/1500 cycles at 2 A g⁻¹ for K⁺/Na⁺ storage, respectively. The underlying ion storage mechanisms are studied by systematical experimental data combined with theoretical simulation results, where the multiple active sites, improved electronic conductivity, and fast ion absorption/diffusion kinetics are major contributors. More importantly, the potassium ion hybrid capacitor consisting of SN-CHS anode and activated carbon cathode deliver an outstanding energy/power density (189.8 Wh kg⁻¹ at 213.5 W kg⁻¹ and 9495 W kg⁻¹ with 53.9 Wh kg⁻¹ retained) and remarkable cycling stability. This contribution not only flourishes the prospective synthesis strategies for advanced hard carbons but also facilitates the upgrading of next-generation stationary power applications.