Structural Engineering of Hard–Soft Carbon Hybrid Anodes for Ultrafast and Ultradurable Potassium‐Ion Storage

Abstract Hard–soft carbon hybrid materials, harvesting the expanded interlayer spacing of hard carbon and the high conductivity of soft carbon, hold great promise as anode materials for potassium‐ion batteries, but efficient and precise structural control remains a major challenge. Herein, hollow porous bowl‐like hard–soft carbon hybrid materials (BHSCs) are facilely synthesized by an in situ hard‐template strategy. It is found that the outer and inner walls of the hard carbon bowls are uniformly wrapped by graphene‐like soft carbon, which accelerates electron transport and promotes the insertion of potassium ions. Finite element simulation further reveals that the soft–hard–soft carbon shell structure releases stress during the insertion of potassium ions. As a result, BHSC anode exhibits an extraordinary rate capability (209 mAh g −1 at 10 A g −1 ) and excellent cycle stability with a capacity of 208 mAh g −1 after 5000 cycles at 2 A g −1 . Impressively, the as‐assembled potassium‐ion hybrid capacitor based on BHSC anode delivers a great energy/power density (116 Wh kg −1 /12980 W kg −1 ) and outstanding capacity retention of 83% after 8000 cycles. This work provides guidance for rational structural design of hard–soft carbon hybrid materials to improve their potassium‐ion storage performance.