M{sup 3+}-modified LiMn{sub 2}O{sub 4} spinel intercalation cathodes. 2: Electrochemical stabilization by Cr{sup 3+}

The 4 V rechargeable capacity of the spinel LiMn{sub 2}O{sub 4} was stabilized by substituting less than 1 mole percent (m/o) Mn{sup 3+} with Cr{sup 3+}. The optimum composition was determined as LiCr{sub 0.012}Mn{sub 1.988}O{sub 4}, which had a discharge capacity exceeding 110 mAh/g even after 100 cycles, although improved stabilities were attained for all Cr-modified compositions studied (0.1 to 7.0 m/o Cr{sup 3+} substitution). The effects of varying electrolyte salt, temperature, and current density were also investigated. Capacity losses in 4 V LiMn{sub 2}O{sub 4}-based spinel systems were attributed to Mn dissolution into the electrolyte causing structural degradation of the cathode and an increase in cell polarization from deposited Mn interfering with Li{sup +} transport through the anodic solid-electrolyte interphase. Substitution of even a small amount of Mn{sup 3+} by trivalent Cr{sup 3+} minimized this dissolution and resulted in enhanced cathodic electrochemical stability.