Structural and electrochemical study of Li–Al–Mn–O–F spinel material for lithium secondary batteries

The structural and electrochemical properties of various Li–Al–Mn–O–F spinels were studied. Li[LixAlyMn2−x−y]O4−zFz (x = 0, 0.05, y = 0, 0.1, 0 ≤ z ≤ 0.2) spinels were synthesized by a solid-state reaction method. Fluorine substitution in Li[LixAlyMn2−x−y]O4−zFz led to well-developed crystallization with octahedral morphology. In addition, Li[LixAlyMn2−x−y]O4−zFz showed superior cycling performance and better thermal stability than LiMn2O4 and LiAl0.1Mn1.9O4. Fluorine substitution also suppressed Mn dissolution which led to stable cycling performance at 55 °C. The differential scanning calorimetry (DSC) results showed that the anion (F for O) and cation (Li, Al for Mn) substituted spinel had better thermal stability than LiMn2O4, Li[AlyMn2−y]O4, or Li[LixAlyMn2−x−y]O4.