Rate Capabilities of Nanostructured LiMn[sub 2]O[sub 4] Electrodes in Aqueous Electrolyte

Nanostructured LiMn 2 O 4 electrodes consisting of LiMn 2 O 4 nanotubules that protrude from a current collector surface like the bristles of a brush were prepared using the template method. The rate capabilities of these nanostructured electrodes were investigated at the 4 V (vs. Li/Li + ) potential plateau in aqueous LiNO 3 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 rate 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 he eliminated and good cycle life is observed. These data show that the nanostructured electrodes offer a unique advantage to this particular electrode/electrolyte system.