Structure and Electrochemical Properties of LiMn2O4-xFx

LiMn2O4-xFx prepared by the sol-gel .method has a perfect crystal formation . The crystal par-ticle size of the material was medium and distributed uniforrrdy. The substitution of F for O increased the specific capacity of the material at the cost of the cycleability . The explanation of this results is that the F decreases the valence of Mn, that is, more Mn^3+ and less Mn^4 + exist in the material. The increase of Mn^3 + will improve the initial specific capacity and Mn^3+ is the original reason for Jahn- Teller effea that caused the poor cycleability of the cathode material by the micro-distortion of the crystal structure. In addition, the expanded measurement of the crystal lattice is also the reason for the poor cycleability. Therefore, the results of F-substitution and cation-substitu-tion are opposite. If the two methods are combined, they can compensate the inability each other and the satisfactory results may be obtained.