OPTIMIZATION OF SPINEL LI1-YO4 AS A 4 V LI-CELL CATHODE IN TERMS OF ALI-MN-O PHASE-DIAGRAM(XMN2)

A semiquantitative Li-Mn-O phase diagram is proposed to analyze the re lationship between the capacity and rechargeability of spinel Li1+2Mn2 -nO4 (-0.11 less than or equal to chi less than or equal to 0.33, 0 le ss than or equal to y less than or equal to 0.33) as a 4 V cathode for lithium-ion batteries. Each compound on the LiMn2O4-Li4Mn5O12-Li2Mn4O 9 triangle can be prepared directly by solid-solid reaction techniques . The chemical formula for each compound is expressed as Li8n/(n+m)Mn8 /(n+m)O-4 (0.5 less than or equal to n less than or equal to 0.8, 3.5 less than or equal to m less than or equal to 4.0) through knowledge o f the Li/Mn molar ratio, n, and the average Mn valence, m. Each compou nd has an initial capacity of 1184 x (4 - m)/(m + n) mAh/g. The capaci ty decreases with increases in both Lithium content and vacancy rate a long one sheet of the hyperboloid, while the rechargeability improves. The synthesis conditions for preparation of an optimal spinel with a large capacity and an ideal rechargeability can be estimated.