Nitrogen-doped carbon with antimony nanoparticles as a stable anode for potassium-ion batteries

Potassium-ion batteries are considered promising alternatives to lithium-ion batteries (LIBs) because they have a lower redox K ⁺ /K potential, a lower Stokes radius, abundant raw materials, and economic benefits. However, K has a larger ionic radius than Li, which may limit the diffusion of K ions into electrodes and cause poor electrode rate capability and cycling stability. In this study, N-doped C and Sb (NC@Sb) composites were synthesised using a facile and cost-effective method of carbonisation and ball milling. The NC@Sb composites had an interconnected and highly porous structure, which was formed by the release of gases such as CO, H ₂O, CO ₂, and NH ₃ during carbonisation. Additionally, NC@Sb is a promising anode owing to the synergistic effects of the high specific capacity of Sb and the good cycling stability of NC. In particular, the NC@Sb composite that contained 10 wt% Sb (NC@Sb10) exhibited a high reversible capacity of 264 mAh g ⁻¹ after 100 cycles at a specific current of 200 mA g ⁻¹. Furthermore, the NC@Sb10 electrode maintained 85% of its initial capacity at a high specific current of 1 A g ⁻¹ even after 500 discharge–charge cycles. The excellent electrochemical performance of the NC@Sb composite is mainly attributed to the stable embedding of the Sb nanoparticles in the porous and electrically conductive NC matrix, which can buffer Sb stress and provide a pathway for the penetration of the electrolyte and K ions.