Designing and Understanding the Superior Potassium Storage Performance of Nitrogen/Phosphorus Co-Doped Hollow Porous Bowl-Like Carbon Anodes

Potassium-ion batteries (PIBs) are promising alternatives to lithium-ion batteries because of the advantage of abundant, low-cost potassium resources. However, PIBs are facing a pivotal challenge to develop suitable electrode materials for efficient insertion/extraction of large-radius potassium ions (K⁺). Here, a viable anode material composed of uniform, hollow porous bowl-like hard carbon dual doped with nitrogen (N) and phosphorus (P) (denoted as N/P-HPCB) is developed for high-performance PIBs. With prominent merits in structure, the as-fabricated N/P-HPCB electrode manifests extraordinary potassium storage performance in terms of high reversible capacity (458.3 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹), superior rate performance (213.6 mAh g⁻¹ at 4 A g⁻¹), and long-term cyclability (205.2 mAh g⁻¹ after 1000 cycles at 2 A g⁻¹). Density-functional theory calculations reveal the merits of N/P dual doping in favor of facilitating the adsorption/diffusion of K⁺ and enhancing the electronic conductivity, guaranteeing improved capacity, and rate capability. Moreover, in situ transmission electron microscopy in conjunction with ex situ microscopy and Raman spectroscopy confirms the exceptional cycling stability originating from the excellent phase reversibility and robust structure integrity of N/P-HPCB electrode during cycling. Overall, the findings shed light on the development of high-performance, durable carbon anodes for advanced PIBs.