Optimizing Kinetics for Enhanced Potassium-Ion Storage in Carbon-Based Anodes

The sluggish kinetics in traditional graphite anode greatly limits its fast-charging capability, which is critically important for commercialization of potassium ion batteries (PIBs). Hard carbon possesses randomly oriented pseudo-graphitic crystallites, enabling homogeneous reaction current and superior rate performance. Herein, a series of hybrid anodes with different hard carbon/graphite ratios are prepared by uniformly mixing graphite and hard carbon with ball-milling. Comprehensive experimental results in combination phase-field simulations reveal that the hybrid anode possesses a homogeneous reaction current and an intriguing potential difference between K+-adsorbed hard carbon and non-potassiated graphite. The homogeneous reaction current in the hybrid anode promotes sufficient utilization of electrode material, leading to an increase in the reversible capacity. The present potential difference between K+-adsorbed hard carbon and non-potassiated graphite provides an additional electric field force that facilitates the diffusion of K+ from hard carbon into the nearest neighbor graphite. All these together, emphasize the synergistic effects between hard carbon and graphite in hybrid anodes toward satisfactory rate and cycling performance. The hybrid strategy proposed here is compatible with the commercial battery manufacturing, offering a practical pathway for the development of high-performance PIBs. Hybrid anodes via mixing graphite and hard carbon are reported to show fast charging K-ion storage, which is achieved by the presence of a homogeneous reaction current and the formation of a self-built electric field that promote the K+ intercalation from hard carbon to nearest neighboring graphite.image