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Novel graphene oxide double-shell hollow-spheres decorated with Mn 3 O 4 nanocrystals were synthesized via a facile solvothermal self-assembly method. They had the uniform outer diameter in ca. 100 nm and the thickness of each shell in ca. 5 nm. The electrochemical supercapacitive properties of the prepared double-shell hollow-sphere composites showed the capacitance of 225 F•g −1 at the scan rate of 5 mV•s −1 , high electrochemical stability that retained about 99.5 % capacitance after cycling 6000 times, and the energy density as high as 34.1 Wh·kg-1 at the power density of 251 W·kg-1. These performances were superior to those of most reported planar graphene-Mn 3 O 4 nanocomposites as well as pure Mn 3 O 4 nanocrystals.

In this paper, a phase transfer method is reported which was used to prepare ultrasmall manganese(ii) sulfide nanocrystals in which prefabricated MnS aggregations are transferred from cyclohexane into an aqueous solution of sodium citrate.

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As anodes for lithium‐ion batteries, CoCO3 has a much higher specific capacity than graphite and can meet the urgent demands of electric vehicles and portable electronics. However, reported CoCO3 anodes are of micrometer‐sized morphology (0.4–10 µm) that severely limits long‐term and rate performances (in particular >2.0 A g−1) due to intrinsically low conductivity and high volume expansion. Mesoporous materials have uniform open mesopores to offer sufficient solid/electrolyte contact, rapid Li+ transport, and large pore volume. However, it is still challenging to prepare uniform mesoporous CoCO3 nanostructures. This work reports a urea–NH4HCO3–ethylene glycol (EG) solvothermal system to fabricate uniform mesoporous CoCO3 nanospindles and concurrently composite with multilayered graphite nanosheets. The obtained mesoporous CoCO3 has a specific surface area of 143.7 m2 g−1, 12.4 times that of commercial CoCO3. The preparation mechanism is studied in‐depth, where urea, NH4HCO3, EG, and crystal water play essential and respective roles. The synergistic effect of the mesopore and graphite nanosheets facilitates long‐term cycling stability (1465 mAh g−1 after 450 cycles at 200 mA g−1 with 101.1% capacity retention) and high‐rate performance (1033 mAh g−1 at 2.0 A g−1). The essential roles of mesopores and graphite nanosheets in boosting the kinetic change are investigated.