Coordination engineering of single zinc atoms on hierarchical dual-carbon for high-performance potassium-ion capacitors

Dual–carbon engineering combines the advantages of graphite and hard carbon, thereby optimizing the potassium storage performance of carbon materials. However, dual–carbon engineering faces challenges balancing specific capacity, capability, and stability. In this study, we present a coordination engineering of Zn–N₄ moieties on dual–carbon through additional P doping, which effectively modulates the symmetric charge distribution around the Zn center. Experimental results and theoretical calculations unveil that additional P doping induces an optimized electronic structure of the Zn–N₄ moieties, thus enhancing K⁺ adsorption. A single–atom Zn metal coordinated with nitrogen and phosphorus reduces the K⁺ diffusion barrier and improves fast K⁺ migration kinetics. Consequently, Zn–NPC@rGO exhibits high reversible specific capacities, excellent rate capability, and impressive cycling stability, and remarkable power and energy densities for potassium–ion capacitors (PICs). This study provides insights into crucial factors for enhancing potassium storage performance.