Rationally Engineered Two-Phase Heterostructured Carbons with a Desired Operating Voltage for High-Performance Potassium-Ion Storage

To address challenges hindering the development of potassium-ion batteries (PIBs), namely, the absence of anode materials that deliver high capacity, safe operating voltages, and rapid ion transport simultaneously, this study introduces a two-phase heterostructured carbon (THC) material, featuring a gradient graphitic degree. This unique architecture is achieved via a meticulously designed phase engineering of the postcoating and pyrolysis process. This heterostructure integrates a less graphitic outer layer featuring expanded interlayer spacing with a higher graphitic inner layer and increased close pore volume, synergistically leveraging intercalation-dominated kinetics and pore-filling mechanisms at a desired operating voltage to enhance capacity and rate performance. Moreover, the two-phase heterostructure effectively overcomes two major drawbacks: it prevents the hazardous ultralow-voltage plating commonly seen in traditional highly graphitic hard carbon while also avoiding the compromised energy density associated with traditional less graphitic hard carbon that lacks closed pores. The desired THC anode achieves a reversible capacity of ∼400 mA h g^–1 at 50 mA g^–1, an average operating potential of 0.54 V (vs K⁺/K), exceptional rate capability (retaining >150 mA h g^–1 at 1000 mA g^–1), and high initial Coulombic efficiency (61%), outperforming existing carbon-based PIB anodes.