Single-Crystalline LiMn2O4 Nanotubes Synthesized Via Template-Engaged Reaction as Cathodes for High-Power Lithium Ion Batteries

Single-crystalline nanotubes of spinel LiMn2O4 with a diameter of about 600 nm, a wall thickness of about 200 nm and a length of 1-4 mu m have been synthesized via a template-engaged reaction using beta-MnO2 nanotubes as a self-sacrifice template. In this fabrication, a minimal structural reorganization can be responsible for the chemical transformation from [001]-oriented beta-MnO2 template to [110]-oriented LiMn2O4. Galvanostatic charge/discharge measurements indicate that the nanotubes exhibit superior high-rate capabilities and good cycling stability. About 70% of its initial capacity can be retained after 1500 cycles at 5 C rate. Importantly, the tubular nanostructures and the single-crystalline nature of the most LiMn2O4 nanotubes are also well preserved after prolonged charge/discharge cycling at a relatively high current density, indicating good structural stability of the single-crystalline nanotubes during lithium intercalation/deintercalation process. As is confirmed from Raman spectra analyses, no evident microstructural changes occur upon long-term cycling. These results reveal that single-crystalline nanotubes of LiMn2O4 will be one of the most promising cathode materials for high-power lithium ion batteries.