M3+-modified LiMn2O4 spinel intercalation cathodes. II. Electrochemical stabilization by Cr3+

The 4 V rechargeable capacity of the spinel LiMn 2 O 4 was stabilized by substituting less than 1 mole percent (m/o) Mn 3+ with Cr 3+ . The optimum composition was determined as LiCr 0.012 Mn 1.988 O 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 3+ substitution). The effects of varying electrolyte salt, temperature, and current density were also investigated. Capacity losses in 4 V LiMn 2 O 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 + transport through the anodic solid-electrolyte interphase. Substitution of even a small amount of Mn 3+ by trivalent Cr 3+ minimized this dissolution and resulted in enhanced cathodic electrochemical stability