Synergistically enhanced electrochemical performance using nitrogen, phosphorus and sulfur tri-doped hollow carbon for advanced potassium ion storage device

Carbonaceous materials have been acknowledged as a promising electrode material yet rational synthesis and practical application remain a handicap. Here, N, P, S tri-doped hollow carbon (NPS-HC) is synthesized via a facile template method with poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) as both carbon source and N, P and S source. The NPS-HC features distinctive hollow structure, large interlayer space and rich defects. The N doping is conducive to K+ transport and surface wettability while the P, S doping not only effectively improves electric conductivity and hydrophilicity but also is in favor of forming abundant active sites. The effect among N, P, S doping is witnessed by the impressive rate capability (217.3 mAh g−1 at 2000 mA g−1) and unprecedented cyclability (198.8 mAh g−1 over 16,000 cycles at 1000 mA g−1 for nearly 6314 h). Moreover, the kinetics analysis and density functional theory clarify that the N, P, S doping contributes to K+ insertion, adsorption and diffusion. Notably, the as-fabricated potassium ion hybrid capacitor (PIHC) shows impressive energy density of 76.4 Wh kg−1 and 96.46% of capacity retention at 1 A g−1 after 5000 cycles. These results offer a broad avenue to dig into insightful anode engineering technology for potassium storage.