Layered Manganese Oxide Intergrowth Electrodes for Rechargeable Lithium Batteries. 2. Substitution with Al

The structural and electrochemical characterization of layered Li x Al y Mn 1 - y O 2 compounds prepared from sodium-containing precursors is described. A quaternary phase diagram showing composition ranges for pure P2 and P3 structures and P2/P3 intergrowths obtained in the Na−Al−Mn−O system is presented. Upon ion-exchange, these compounds change to O2, O3, or O2/O3 stacking arrangements, respectively. The oxygen array in O3 and spinel structures is similar, and most of the O3 structures convert to spinel rapidly upon electrochemical cycling in lithium cells. This process is delayed somewhat by increased Al substitution, but not completely inhibited. More effective suppression of the phase transformation is observed in O2/O3 intergrowth electrodes. Additionally, the capacity retention upon cycling of cells containing intergrowth electrodes is superior to those with pure O2 structures.