Engineering stable carbon sponge with moderate interlayer spacing and porous architecture for rapid K+-intercalation

The practical application of graphitic carbon materials in potassium-ion batteries (PIBs) is severely hindered by slow K+-intercalation kinetics and severe volume changes during (de)potassiation process. It is challenging but necessary to achieve satisfactory carbon anode with good structural stability and rapid K+-intercalation rate at low potential. Herein, we theoretically investigated the relationship between K intercalation behavior and carbon interlayer spacing by density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) simulation, and proposed that kinetics of K intercalation improves gradually with the expanding of interlayer spacing. We accordingly constructed a free-standing carbon sponge material with moderate interlayer spacing and porous hollow structure, which achieves synergistically boosting K+-intercalation rate at low potential and enhancing structural stability. As a result, the porous hollow carbon sponge provides rapid K+-intercalation rate at high current density and accommodate volume variety to ensure excellent structural stability during the long-term (de)potassiation process (over 1000 cycles). Moreover, the full cell is successfully assembled with outstanding cycling performance (over 500 cycles) and high voltage output (2.0–3.7 V). This work provides a novel strategy for developing high-performance graphitic carbon anode with rapid K+-intercalation rate and high structural stability for PIBs.