Onset Mechanism of Jahn-Teller Distortion in 4 V LiMn[sub 2]O[sub 4] and Its Suppression by LiM[sub 0.05]Mn[sub 1.95]O[sub 4] (M = Co, Ni) Coating

There have been several causes for the capacity fading of reported by many authors, which include Mn dissolution into the electrolyte, and the onset of a Jahn-Teller distortion. One of the main remedies suggested to combat those causes has been doping with other transition-metal ions. However, most of the deterioration reactions take place on the surface. In this study, was coated with a doped-spinel oxide to combat the causes of capacity fading in , which modifies only the surface of the electrodes, and its effect was diagnosed using the bending beam method (BBM). The doped-spinel coated showed an excellent cycle performance. From the BBM data, it was confirmed that this excellent performance was largely due to the suppression of the Jahn-Teller distortion, which takes place at the end of the cathodic sweep in the 4 V range. Furthermore, the mechanism for the onset and suppression of Jahn-Teller distortion in 4 V is proposed based on the strain variations of the stoichiometric, doped, and doped-spinel coated spinel electrodes.