Efficient Lithium/Sodium-Ion Storage by Core-Shell Carbon Nanospheres@TiO 2 Decorate by Epitaxial WSe 2 Nanosheets Derived from Bimetallic Polydopamine Composites.

Metal-polydopamine coordination chemistry attracts great attention owing to the synergistic effect of adjustable components and advantageous structures. However, few efforts have been devoted to exploring bimetal-polydopamine composites, especially for multistructural composites with high-capacity components and high stability. In this regard, the TiO 2 @C-WSe 2 core-shell nanospheres are designed and fabricated based on Ti-W-polydopamine composites after selenization, in which the TiO 2 nanoparticles are encapsulated or embedded in the carbon nanospheres and the external WSe 2 nanosheets are grown epitaxially on the carbon surfaces, featuring multiple channels for ion diffusion and abundant active edges for electrochemical reactions. The introduction of WSe 2 not only greatly improves the capacity but also results in exponential growth of the active edge. As a result, the as-prepared TiO 2 @C-WSe 2 displayed long-term cycling performance in lithium-ion batteries. Furthermore, the anode is assembled into sodium-ion batteries, manifesting a stable capacity of 352 mA h g -1 at 1.0 A g -1 even after 2000 cycles, one of the best performances for polydopamine-based composites. Enhanced performance can be attributed to the synergies of high-capacity components and different dimensional materials. This work highlights that the rational design of functional structures provides a novel inspiration for electrodes with effective nanoarchitectures.