Effect of Low-Temperature Fluorine Doping on the Properties of Spinel LiMn[sub 2−2y]Li[sub y]M[sub y]O[sub 4−η]F[sub η] (M=Fe, Co, and Zn) Cathodes

Spinel oxy-fluoride compositions ( , Co, and Zn) have been synthesized by a selective, low-temperature fluorination with of the corresponding spinel oxides that were synthesized at . With a given cation-substituted composition, the lattice parameter and reversible capacity increase with increasing fluorine content due to a lowering of the Mn oxidation state, confirming the bulk substitution of for in the lattice. The fluorine incorporation with the low melting also provides an added advantage of increased tap density due to a closer particle-particle contact. A correlation of the cyclability of the various compositions to Mn valence reveals that the Mn valence needs to be to impart good capacity retention at 25 and .