Studies of Mg-Substituted Li[sub 4−x]Mg[sub x]Ti[sub 5]O[sub 12] Spinel Electrodes (0≤x≤1) for Lithium Batteries

Magnesium-substituted spinel electrodes have been investigated as insertion electrodes for lithium batteries. The substitution of divalent Mg ions for monovalent Li ions in the structure necessitates that the difference in charge must be compensated by a reduction of an equivalent number of Ti cations from to The substitution increases the conductivity of the spinel framework by many orders of magnitude, from for insulating in which all the titanium ions are tetravalent, to for in which the average titanium oxidation state is 3.8. The improved conductivity decreases the area specific impedance of cells and increases the rate capability of electrodes for small x , typically The rechargeable capacity of electrodes, particularly those with x close to 1 (130 mAh/g), is inferior to that of unsubstituted electrodes 150 mAh/g); the smaller capacity is attributed to the partial occupation of tetrahedral (8a) sites by Mg ions in the spinel structure. © 2000 The Electrochemical Society. All rights reserved.