Robust Micro-Sized and Defect-Rich Carbon-Carbon Composites as Advanced Anodes for Potassium-Ion Batteries

Pitch-derived carbon (PC) anode features the merits of low-cost, rich edge-defect sites, and tunable crystallization degree for potassium ion batteries (PIBs). However, gaining the PC anode with both rich edge-defect sites and robust structure remains challenging. Herein, micro-sized and robust PC/expanded-graphite (EG) composites (EGC) with rich edge-defect sites are massively synthesized via melting impregnation and confined pyrolysis. The PC is in situ encapsulated in micro-sized EG skeleton with robust chemical bonds between PC and EG after thermal treatment, endowing the structural stability as micro-sized carbon-carbon composites. The confinement effect originating from EG skeleton could suppress the crystallization degree of the PC and contribute rich edge-defect sites in EGC composites. Additionally, the EG skeleton inside EGC could form continuous electronic conduction nets and establish low-tortuosity carbonaceous electrodes, facilitating rapid electron/ion migration. While applied in PIBs, the EGC anode delivers a reversible capacity that up to 338.5 mAh g^-1 at 0.1 A g^-1 , superior rate performance of 127.5 mAh g^-1 at 5.0 A g^-1 , and long-term stability with 204.8 mAh g^-1 retain after 700 cycles at 1.0 A g^-1 . This novel strategy highlights an interesting category of heterogeneous carbon-carbon composite materials to keep pace with the demand for the future PIBs industry.