Synthesis of sandwich-like structured carbon spheres @ MXene as anode for high-performance potassium-ion batteries

Potassium-ion batteries are receiving increasing attention owing to their rich potassium storage and cheap. However, relatively large radius of K+ hinder it smooth embedding and extraction from the electrode material, leading to poor electrode dynamics and structural instability. Due to the disadvantages of insufficient large layer spacing for Ti3C2 MXene, we develop a novel carbon spheres coating and embedding on the surface and inter -layer of the Ti3C2 MXene composite (CSs@Ti3C2) with the freeze drying and annealing method. The carbon spheres embedding on the interlayer of the Ti3C2, which can enlarge the lattice distance and improve potassium ion insertion/extraction the Ti3C2. Furthermore, the carbon spheres can provide high surface area and many active sites for storage the K+, obtaining high specific capacity. Therefore, the CSs@Ti3C2 exhibits splendid cycling property (195.8 mAhg- 1 at 100 mAg-1 after 200 cycles) and long-life charge and discharge (143.3 mAhg-1 at 500 mAg-1 after 1000 charge and discharge). This study offers a new method for achieving high property MXene as anodic material for storage system.