Two α-MnO2 crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO2 prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO2 crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO2 crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO2 material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO2 material has better electrochemical performance.

An alternative electrodeposition technology, which provides an efficient way to complete a better interface contact between electroactive materials and metal foil substrates, was used to prepare Ni 3 S 2 /Ni composites in aqueous solutions contained thiourea (TU). The deposition parameters, such as time and TU concentration, were optimized. Surface morphology, chemical composition, and crystal structure of Ni 3 S 2 /Ni composites were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), respectively. A Ni 3 S 2 /Ni composite, which consisted of submicrometer grains with size in the range of 0.2−2 μm, was obtained. Galavostatic battery testing shows that the submicrometer Ni 3 S 2 /Ni 4 composites as cathodes for lithium batteries exhibit a high specific capacity of 338 mAh g −1 at a current density of 0.17 A/g (∼0.6 C), extraordinary capacity retention as well as 95.3% after 100 cycles, and outstanding rate performance, for example, still delivering 180 mAh g −1 at 1.7 A g −1 (∼6 C). The performances may benefit from their miscellaneous submicrometer structures and subsequently formed tremella-like structures during discharge/charge cycles.