Synthesis and electrochemical properties of nonstoichiometric LiAlxMn2−xO4−δ as cathode materials for rechargeable lithium ion battery

Nonstoichiometric spinel oxides, LiAlxMn2−xO4−δ   (x=0.1,0.2x=0.1,0.2), were synthesized under controlled partial pressure of oxygen, and their elecrochemical performances were investigated. As an Al content increases, solubility limit of the oxygen nonstoichiometry, δ  , increased, while partial molar enthalpy ΔH¯O2 of the formation of oxygen nonstoichiometry decreased.Cycle performance of LiAlxMn2−xO4 showed significant improvement comparing with that of LiMn2O4 cathode. However, the decrease of theoretical capacity was accompanied with Al doping. Nonstoichiometric LiAlxMn2−xO4−δ showed the increase in capacity with keeping good cycle performances as well as stoichiometric LiAlxMn2−xO4. Although the introduction of oxygen nonstoichiometry leads to the increase of Mn3+ which is known as Jahn–Teller ion, DSC curves for LiAlxMn2−xO4−δ showed no exothermic peak due to phase transition arising from Jahn–Teller distortion around room temperature.

Defect introduction into spinel.Figure optionsDownload as PowerPoint slide