Nanocubes Composed of FeS2@C Nanoparticles as an Advanced Anode Material for K-ion Storage
Potassium-ion batteries (KIBs) are considered as one of the most promising devices for large-scale energy storage because of the comparable output voltage with lithium ion batteries and the abundant reserves of potassium. FeS2 is regarded as a very important anode material for KIBs due to its low cost and high capacity. However, the poor electronic conductivity of FeS2 and the huge volume expansion during discharge/charge process strongly inhibit the K-storage performance. To solve these problems, herein, unique core-shell FeS2@C nanocubes with nanoparticles in the interior and carbon shells in the exterior are designed. The inside FeS2 nanoparticles are beneficial for K+ diffusion and the penetration of electrolyte, while the outside carbon shells can enhance the electronic conductivity and suppress the volume expansion. The unique core-shell structure displays outstanding K-storage performance with impressive specific capacity, excellent cycling stability and superior rate capability with 73% retention rate at 2 A g-1. This work not only provides solutions to obtain superior anode material for KIBs, but also offers insights to design hierarchical structure for energy storage systems.