Engineering of Nanonetwork-Structured Carbon to Enable High-Performance Potassium-Ion Storage

Abstract Potassium-ion batteries (KIBs) have been developed as an emerging electrochemical energy storage device due to the low cost of potassium and resource-abundance. However, they suffer insufficient cyclability and poor rate capability caused by the large K+, severely limits their further applications. Herein, a nanonetwork-structured carbon (NNSC) is reported to address the issue, cycling stability with very low decay rate of 0.004% per cycle over 2000 cycles and excellent rate capability of 261 mAh g-1 at 100 mA g-1 and 108 mAh g-1 at 5000 mA g-1 are achieved. The superior performance is attributed to the unique structure of NNSC, in which the three-dimensional interconnected hierarchical porous structure with hollow nanosphere as network units not only can effectively alleviate the volume expansion induced by the insertion of large K+, but also can offer fast pathways for potassium ion diffusion. In addition, the local graphitized carbon shell of NNSC can promote conductivity of material and reduce the resistance to K+ transportation. Thus, the nanonetwork-structured carbon has great potential in developing stable-structure and high-rate electrodes for next generation KIBs.