Rate capabilities of nanostructured LiMn2O4 electrodes in aqueous electrolyte

Nanostructured LiMn2O4 electrodes consisting of LiMn2O4 nanotubules that pr otrude from a current collector surface like the bristles of a brush were p repared using the template method. The rare capabilities of these nanostruc tured electrodes were investigated at the 4V (vs. Li/Li+) potential plateau in aqueous LiNO3 electrolyte. Rate capability improved with decreasing wal l thickness of the tubules which formed the electrode. This result is in ag reement with our prior investigations of template-synthesized electrode mat erials which showed that rare capabilities improve with decreasing distance for Li+ transport in the solid state. The rate capabilities of electrodes prepared from the smallest-wall-thickness tubules are extraordinary; these electrodes can be cycled at C rates as high as 109 C. In addition, these in vestigations suggest that the poor cycling performance observed in prior st udies of this electrode/electrolyte system results from unwanted oxidation of water during the charging process. By controlling the charge rate and th e dimensions of the nanotubules making up the template-synthesized cathodes , this unwanted side reaction can be eliminated and good cycle life is obse rved. These data show that the nanostructured electrodes offer a unique adv antage to this particular electrode/electrolyte system. (C) 2000 The Electr ochemical Society. S0013-4651(99)12-001-9. All rights reserved.