An asymmetrical cobalt single-atom coordination strategy is explored to modulate the interfacial chemistry of hard carbon, which reduces K⁺ diffusion barriers and improves charge transfer kinetics, due to the enhanced electron delocalization, an upshift of d-band center, and the decreased KFSI dissociation barrier. The as-prepared hard carbon anode possesses excellent rate capability, high reversible capacities, and remarkable cycling performance.

Potassium-ion batteries (PIBs) have triggered intense attention as promising alternatives to lithium-ion batteries for grid-level large-scale applications. However, sluggish potassium storage kinetics due to the large ionic radius of K⁺ always results in poor rate and unsatisfactory cycling capability. Herein, an asymmetrical cobalt single-atom coordination strategy is proposed to modulate the interfacial chemistry of hard carbon. The unique asymmetrical configuration of Co single atom effectively reduces K⁺ diffusion barriers and improves charge transfer kinetics, due to the enhanced electron delocalization, an upshift of d-band center, and the decreased KFSI dissociation barrier. Consequently, the obtained Co-NPC anode exhibits a high reversible capacity of 245.1 mAh g⁻¹ at 0.2 A g⁻¹, an excellent rate capability of 179.0 mAh g⁻¹ at 1 A g⁻¹, and a remarkable cycling stability. When paired with commercial activated carbon, the resulting potassium-ion hybrid capacitors exhibit a notable energy density of 147.3 Wh kg⁻¹ and a power density of 392.2 W kg⁻¹, manifesting their promising potential for practical energy storage applications. This work offers a novel pathway for achieving efficient and reversible potassium storage in hard carbon anodes for high-performance PIBs.