Reactive Dissolution–Thermal Conversion Enables Closed‐Pore Filling in Hard Carbon toward Potassium Storage
Hongliang Li, Yifan Chen, Linlin Wang, Jiale Chen, Xiaogang Niu, Guangqiang Hou, Jiapeng Lu, Yue Bai, Yuxuan Xing, Shiwan Zhang, Yujie ZhuABSTRACT
Hard carbon (HC) is a leading anode candidate for potassium‐ion batteries (PIBs), yet its low capacity and high operating potential limit energy density and practical application. Herein, a reactive dissolution–thermal conversion strategy is developed to engineer HC microstructure at the molecular level. Phosphoric acid dissolves cellulose at room temperature to form P─O─C crosslinks as a structural scaffold, while subsequent mild air oxidation induces ring opening to generate thermally labile C═O and C─O─C groups that act as gas‐sculpting agents during carbonization. Their synergy creates larger closed pores, and concurrent phosphorus doping expands the interlayer spacing, thereby facilitating K + pore filling and markedly enhancing the low‐voltage plateau capacity. As a result, the optimized HC anode delivers a reversible capacity of 341.2 mAh g − 1 , including 242 mAh g − 1 below 0.4 V, with 73.9% capacity retention after 1000 cycles. Coupled with a K 2 Mn[Fe(CN) 6 ] cathode, the full cell exhibits an average discharge voltage of 3.61 V, a specific energy of 312.8 Wh kg − 1 (based on the total mass of K 2 Mn[Fe(CN) 6 ] and HC), and 83.1% capacity retention after 1000 cycles at 0.5 C. This work provides a molecular‐level design strategy for HC anodes toward high‐energy PIBs.