Rate capabilities of nanostructured LiMn2O4 electrodes in aqueous electrolyte

Nanostructured LiMn2O4 electrodes consisting of LiMn2O4 nanotubules that protrude from a current collector surface like the bristles of a brush were prepared using the template method. The rare capabilities of these nanostructured electrodes were investigated at the 4V (vs. Li/Li+) potential plateau in aqueous LiNO3 electrolyte. Rate capability improved with decreasing wall thickness of the tubules which formed the electrode. This result is in agreement with our prior investigations of template-synthesized electrode materials 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 investigations suggest that the poor cycling performance observed in prior studies of this electrode/electrolyte system results from unwanted oxidation of water during the charging process. By controlling the charge rate and the dimensions of the nanotubules making up the template-synthesized cathodes, this unwanted side reaction can be eliminated and good cycle life is observed. These data show that the nanostructured electrodes offer a unique advantage to this particular electrode/electrolyte system. (C) 2000 The Electrochemical Society. S0013-4651(99)12-001-9. All rights reserved.