Some Aspects of LiMn₂ O ₄ Electrochemistry in the 4 Volt Range

is a hopping semiconductor ; as is obtained by full delithiation. A semiconductor‐metal transition is not observed by Li⁺ extraction because the critical Mn‐Mn distance for this transition (2.743 Å) is shorter than those observed for and (2.803 and 2.913 Å, respectively). However, on Li⁺ removal the charge‐transfer resistance of the spinel decreases, perhaps as a consequence of enhanced Li⁺ crossing of the electrolyte/cathode interface. A full charge/discharge cycle does not allow one to reinsert the same amount of Li⁺ extracted as a consequence of a structural alteration. The abrupt voltage drop at the end of the cycle coincides with a unit cell parameter of ∼8.24 Å, i.e., the same value of the original spinel. Spinels prepared at 700–750°C have electrochemical features different from those of spinels made at 800–900°C. In particular, Li⁺ is more easily extracted from the former in a process which seems to create Li⁺ ordering for and ion . The self‐discharge characteristics of fully oxidized spinels in different electrolytes have been examined.