Asymmetrical Coordination of Cobalt Single-Atom Catalyzed Interfacial Chemistry in Hard Carbon Anodes for Fast and Reversible Potassium Storage.

Abstract

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.