Building expressway for K⁺ transport in soft carbon with graphene cushion to boost rate capability

Carbonaceous materials have been demonstrated as the promising anode for potassium ion batteries (KIBs). However, up to now, limited number of strategies could improve the power density of carbonaceous anode without sacrificing the energy density, showing restricted stability and rate capability. In this manuscript, a defect-rich and interlayer spacing expanded graphene cushion (GC) is employed to build expressway network for K⁺ transport in soft carbon (SC) and buffer the volumetric variation. Meanwhile, SC is divided into nanodomains by GC, in which the diffusion distance is shortened and fracture energy is increased. During the electrochemical reaction process, K⁺ is preferentially transported along the wall of GC and then diffuses into/out of SC nanodomains. At 1.6 A·g⁻¹, the voltage polarization decreases from 2.02 V of SC to 0.54 V of SCGC, and the discharge specific capacity increases from 4.9 to 197.6 mAh·g⁻¹. Additionally, the unique cushion structure with high Young’s modulus can increase the expansion tolerance and guarantee a long service life. The cycling stability test shows a capacity retention of 72.2% even after 1000 cycles at 1 A·g⁻¹. Thus, this type of anode materials might be potentially suitable for high performance KIBs.