The synthesis of a core-shell MnO2/3D-ordered hollow carbon sphere composite and its superior electrochemical capability for lithium ion batteries

An almost complete and highly reversible conversion reaction of MnO2 with a 4e process by utilizing 3D ordered hollow carbon spheres (HCS) as a conductive matrix was reported. A PMMA emulsion was used as a template and resorcinol formaldehyde as a carbon precursor to form HCS. The template was decomposed and then the precursor was carbonized into the uniform structure of HCS after sintering at 800°C for 1 h under a N2 atmosphere. Nano-structured MnO2 was grown in situ on the surface of HCS via a facile redox method, using P123 as a surfactant. KMnO4 was reduced by the external carbon layer of HCS and then nano-crystalline MnO2 was uniformly grown in situ on the 3D ordered surfaces of HCS. The superior electrochemical performance can be attributed to the synergistic effect of the hierarchical architecture. The conductive HCS matrix improves the ion and electron transportation in the MnO2 bulk phase, while also decreasing the resistance at the interface of the electrode/electrolyte.