Bi-continuous nanoporous carbon sphere derived from SiOC as high-performance anodes for PIBs

Abstract

Potassium-ion batteries (PIBs) are considered as promising alternative candidates to replace lithium-ion batteries due to their low cost, adequate reserves and high energy density. However, a large ionic radius of K+ ions leads to a huge volume expansion and a low ion diffusion rate, restricting its cycling stability and rate performance. Herein, bi-continuous and nanoporous carbon spheres (BC-NCS), consisting of continuous nanocarbon framework and interconnected nanopores, are designed and prepared by etching carbon-rich SiOC ceramics. The interconnected nanopores provide fast ion diffusion channels and sufficient room for tolerating the volume expansion, thus leading to high rate performance and long cycle stability, while the continuous carbon framework possesses a defective nature, an expanded interlayer distance (0.39 nm) and various oxygen‐containing functional groups on its surface induced during the etching process, further endowing it with high reversible capacity and stability. Therefore, the BC-NCS exhibits a high initial reversible capacity (336 mAh g−1 at 0.1 A g−1), long cycle and high rate performance (191 mAh g−1 after 2000 cycles at 0.5 A g−1). Importantly, we investigate the potential application of bi-continuous carbon materials in high performance PIBs, and the bi-continuous structure could be induced into various active materials for the application in different batteries.