A Structurally Stable α-MnO2 nanorod Cathode for Enhanced Reversible Divalent Zinc Storage

Tuesday, October 13, 2015
West Hall 1 (Phoenix Convention Center)
V. Mathew, Z. Xiu, M. H. Alfaruqi, J. Gim, S. Kim, J. Song, T. Vu Thi, D. P. Tung, J. P. Baboo (Chonnam National University), and J. Kim (Chonnam National University)
In this study, a nanorod-type α-MnO2 cathode prepared by a facile hydrothermal reaction was utilized for rechargeable aqueous zinc-ion battery (ZIB) applications. Electron microscopy studies revealed rod-type particles with approximately 20 and 200 nm of width and length, respectively. When tested for zinc storage properties, the nanorod cathode exhibited an initial discharge capacity of 176.8 mAh/g at a current density of 83 mA/g and demonstrated nearly 100% Coulombic efficiencies under prolonged cycling. Further, rate performance measurements revealed that specific capacities of 43.33 and 31.48 mAh/g were attained at current densities as high as 1333 and 1666 mA/g. Ex-situ XAS investigations confirmed the reversibility of electrochemical Zn-insertion into the a-MnO2 electrode. Moreover, a combination of ex-situ synchrotron XRD studies, visualization and pattern-fitting software programs not only established the electrochemical Zn-insertion into the host a-MnO2 structure but also indicated that the unit cell volume of the [2x2] tunnels in the a-MnO2 host expands by approximately 3.12% during Zn-insertion. The present study thus paves the way for further development of aqueous ZIB as an ideal energy storage system due to its excellent safety and reliability.