Water-Soluble Salt Template-Assisted Anchor of Hollow FeS2 Nanoparticle Inside 3D Carbon Skeleton to Achieve Fast Potassium-Ion Storage

The rationally structural engineering is an efficient strategy to improve the comprehensive performance of potassium-ion storage anode materials. In this paper, a hybrid with hollow FeS2 nanoparticles anchored into the 3D carbon skeleton (labeled as H-FeS2@3DCS) is successfully constructed through two critical steps of in situ chemical deposition and anion-exchange reaction strategies. In the former, the water-soluble Na2CO3 crystals are used as hard templates for the preparation of 3DCS, while Fe3+-containing aqueous solutions are utilized to remove the Na2CO3 templates. Interestingly, the intense collision between Fe3+ and CO32- in aqueous solution produces nanoscale Fe(OH)(3) colloidal particles, which are firmly anchored into the pores of the carbon skeleton to form a "lotus-seed"-like nanostructure. In the latter case, a central void space is created inside the FeS2 nanoparticles due to the different diffusion rates of S-anions and Fe-cations during the subsequent sulfidation process. Thanks to this unique composition model, the H-FeS2@3DCS hybrid not only alleviates the volume expansion efficiently by rationally hollow structure design, but also provides spacious "roads" (3D carbon skeleton) and "houses" (hollow FeS2 nanoparticles) for fast K-ion transition and storage. As the anode of PIBs and PIHCs, the resultant H-FeS2@3DCS electrode delivers an obviously enhanced K-ions storage performance over state-of-the-art.