Carbon dots decorated on the ultrafine metal sulfide nanoparticles implanted hollow layered double hydroxides nanocages as new-type anodes for potassium-ion batteries

Although layered double hydroxides (LDH) stands out among various electrode materials with considerable theoretical capacities, the intrinsically poor electronic conductivity and inevitable aggregations of the fragile 2D structure impede their practical application in rechargeable metal-ion battery. In the present work, nickel/cobalt LDH hollow nanocages derived from metal-organic frameworks (MOFs) were synthesized. Afterward, the ultrafine metal sulfide nanoparticles were implanted into the LDH nanocages (LDH-S) through a in-situ sulfide method. Such a LDH-S architecture achieves an initial discharge capacity of 1387 mAh g−1 and stable specific capacity of 391 mAh g−1 at 0.1 A g−1 after 200 cycles while using as potassium-ion battery anode material. In addition, when LDH-S nanocages are decorated with carbon dots ([email protected]), it exhibits an excellent long-term lifespan achieving 188 mAh g−1 after 8000 cycles at 1.0 A g−1. With the aid of ex-situ characterization and density functional theory (DFT) calculation, the excellent performance of [email protected] can be contributed to the hetero-structure, in which the interlayer confinement of ultrafine metal sulfides enhances the electrical/ionic conductivity. Furthermore, the well-defined internal voids and functional shells promise intimate contact between the electrolyte and electrode material, and also could avoid agglomeration during repeated potassium-ion insertion and extraction process. In addition, the presence of carbon dots (CDs) further enhances the electrical conductivity and stabilizes the electrode structure. This work proves that LDH-based anode with high capacity and low cost may be one of the promising candidates for potassium-ion storage and the introduction of CDs maybe an efficient way for construction of high-efficient electrode materials for potassium-ion storage.