Urchin-like α-MnO2 formed by nanoneedles for high-performance lithium batteries

MnO2 nanoneedles (NNs) were synthesized by sol-gel assisted by a redox reaction between ascorbic acid and KMnO4. X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Raman, far-infrared spectroscopy, and magnetic measurements confirm the tunnel structure of the tetragonal alpha-MnO2 phase. The MnO2 NNs prepared by sol-gel at moderate temperature (T ae 350 A degrees C) aggregate with an urchin-like morphology observed by scanning electron (SEM) and high-resolution transmission electron (TEM) microscopy. Electrochemical investigations show an outstanding initial specific capacity ca. 230 mAh g(-1) and 45 % capacity retention at 100th cycle was obtained for these MnO2 nanoneedles.