Co quantum dots embedded in modified montmorillonite loaded with graphitized carbon as an ultra-stable anode material for sodium-ion battery.

Carbonaceous materials are competitive anodes in sodium-ion batteries (SIBs) due to their advantages, such as low cost, abundant active sites, and porosity. However, this type of material still suffers from slow rate capability and low capacity, which greatly hinders its application. In this work, the biomass-derived carbon is optimized based on a layered montmorillonite (Mt) skeleton and the cobalt quantum dots (Co QDs). A three-dimensional (3D) combination, specifically a 3D flower-like structure, of 0D material (Co QDs) and a two-dimensional (2D) material (Mt) has been achieved. The optimization and local limited effects of the Co QDs on the electronic properties have been demonstrated by density functional theory (DFT). The metallic Co QDs and carbon could form a Mott-Schottky junction, enhancing the conductivity and Na adsorption. Due to the synergetic improvement of structure and conductivity, the stripped Mt embedded with Co QDs loaded with nitrogen doped carbon (FMt@Co-NC) shows ultra-stable cycle stability (99.12% retention after 10,000 cycles at 10 A/g). This is the first time that Mt has been employed in high performance SIBs, which incubates a grand blueprint for effectively utilizing similar inactive energy-storage materials, through a simple and reliable approach.