Fabrication of N/O/S co-doped carbon bubbles with nanoporous structure for potassium-ion storage

Potassium ion batteries and hybrid supercapacitors are promising new energy storage devices with high energy and power densities, as well as long cycle life. Carbon materials are ideal as the electrodes due to their low cost and wide availability. However, the large ionic radius of K-ions causes poor rate and cycling performance for carbon-based electrode materials. Herein, N/O/S co-doped porous carbon (NOSPC) bubbles are developed for Kion storage. The carbon bubbles are similar to 300 nm in size with openings, and possess hierarchical nanoporous structures and large surface area (644 m(2)/g). Heteroatom-doping can increase active sites and enhance the wettability of carbon bubbles. The half-cell with carbon nano-bubbles as the electrode delivers a high capacity of 430.3 mAh/g at 0.1 A/g and maintains an outstanding retention of 82.9 % after 5000 cycles at 2 A/g. It demonstrates that the N/O/S co-doped carbon bubbles with nanoporous structure provide prospects for highperformance potassium ion storage applications.