Two-dimensional carbon-coated CoS2 nanoplatelets issued from a novel Co(OH)(OCH3) precursor as anode materials for lithium ion batteries

Abstract We establish a unique bottom-up route to fabricate well-defined two-dimensional (2D) carbon coated CoS2 (CoS2@C) nanoplatelets as anode materials for highly reversible lithium ion batteries (LIBs). A novel platelet-like Co(OH)(OCH3) precursor is firstly prepared with a solvothermal method, and subsequently immersed in dopamine aqueous solution to generate a Co(OH)(OCH3)/polydopamine composite. Finally, 2D CoS2@C nanoplatelets are obtained through the topotactic sulfurization of Co(OH)(OCH3) into CoS2 nanoplatelets and the simultaneous carbonization of polydopamine coating by thermal annealing at 450 °C. The 2D porous CoS2 nanoplatelet cores offer abundant active sites for Li storage and shorten transport lengths of lithium ions and electrons, while the amorphous carbon shells increase the electronic conductivity, retard the dissolution of intermediate reactants in the electrolyte, and accommodate volume change during the charge-discharge process. As a result, the hierarchical CoS2@C nanoplatelets deliver a high reversible specific capacity of 1100 mAh g−1 at 0.2 A g−1 and maintain 740 mAh g−1 after 400 cycles at 1.0 A g−1. Moreover, the rate capability is also significantly improved relative to the bare CoS2. This work offers a new strategy for the synthesis of 2D transition metal sulfide nanoplatelets and their rational design to achieve desirable electrochemical performances for LIBs.