Cobalt Nanoparticles Synergize with Oxygen‐Containing Functional Groups to Realize Fast and Stable Potassium Storage for Carbon Anode

Abstract Oxygen‐containing functional groups (OFGs) grafted by carbon materials surface can serve as active sites to reversibly store potassium and simultaneously contribute to forming a stable solid‐electrolyte interphase layer, leading to increased capacity and cycling stability. However, the excessive OFGs will damage conductivity and hence causes the increase in electron transfer resistance, easily resulting in a poor rate. Herein, it is theoretically demonstrated that the embedded metallic Co particles can synergize with C‐O‐C moieties in OFGs to accelerate K‐ion adsorption (△E = −1.62 eV) and regulate electronic structure, ensuring high capacity and rate. In view of this, O‐doped carbon with implanted Co is well established, and it is found that pyrolysis temperature can effectively regulate Co content and C‐O‐C proportion. Various characterizations unveil that the introduced Co species not only evidently promote the adsorption capability of C‐O‐C to K‐ion, but catalyze the generation of graphitic carbon. Benefiting from these merits (e.g., enhanced adsorption ability and electronic conductivity), the sample with the optimal Co content and C‐O‐C proportion presents a high capacity of 254.7 mAh g⁻¹ and an excellent rate capability (202.9 mAh g⁻¹ at 2 A g⁻¹). The unique design route makes fast and stable K‐storage of carbon anode possible.