Urchin-like Co3O4microspheres were prepared by a hydrothermal and sintering method; oxygen vacancies induce a local built-in electric field to boost battery performance.

Scheme 1. Schematic illustration for the preparation process of cobalt oxides with cationic vacancies.

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After optimization using percolation theory, excellent absorbing properties (90% absorption) were achieved for Ni/C nanocomposites with advantages such as thin thickness (1.75 and 1.5 mm) and light weight (25 and 30 wt%).

To enhance the performance of Li-ion batteries, hierarchical carbon-based hollow frameworks embedded with cobalt nanoparticles are prepared by the pyrolysis of core-shell ZIF-8@ZIF-67 polyhedrals prepared via a seedmediated growth method. The resultant hollow frameworks are composed of the N-doped carbon as the inner shells and the porous graphitic carbon embedded with cobalt nanoparticles as the outer shells. Benefiting from the unique hollow architecture with large surface area and good electrical conductivity, the electrode materials exhibit good electrochemical performance with improved specific capacities, high-rate capability, and good cycling stability for Li-ion batteries. More importantly, the quantitative kinetic analysis reveals the crucial contributions of N doping and the porous structure of graphitic carbon with cobalt nanoparticles for boosting the performance of carbon-based materials. The rational design of the unique carbon-based architecture and the understanding of the underlying mechanism for the charge storage process are crucial to construct advanced carbon-based materials for high-performance Li-ion batteries.