Synthesis And Dope Study Of Spinel LiMn₂O₄ Anode Materials For Li-Ion Batteries

There is 148mAh/g theory capacity in spinel LiMn2O4, which has lots of advantages, such as synthesize method is simple, the price is low, and is friendly to environment. The spinel LiMn2O4 is perfect substitution of Li-ion batteries cathode. But now it has not been commercialized because its capacity fades during the cycle of charge-discharge. The capacity fading has several possible reasons, including manganese dissolution, distortion of the crystal lattice due to the Jahn-Teller effect and electrolyte oxidation. Doping the spinel with Al and Mg was introduced in this paper to improve performance of Li-ion batteries cathode material.In this work, spinel LiMn2O4 and LiAlxMn2-xO4 and LiMgyMn2-yO4 have been synthesized by a sol-gel-complexation method and their structure and electrochemical properties have been examined. Citric acid was used as complexing reagent. At first, the citrate precursor formed and was heated to remove water. After drying, the precursors were decomposed at 300℃to eliminate organic contents. The decomposed powers were slightly ground and then sintered at different temperature in air.The structure of material was tested by TG-DTA, XRD, SEM and TEM. The capability was tested by charge-discharge cycle. The influences of various synthesized condition, sintering time and the amount of Al and Mg were studies and correlative parameter to improve performance of material were optimized.The XRD pattern suggested LiMn2O4 and LiAlxMn2-xO4 and LiMgyMn2-yO4 synthesized by sol-gel belongs to spinel structure. The crystallinity is increased with increasing temperature as indicated by the sharpness of the intensities of the XRD peaks. The impurity peaks were observed in the LiAlxMn2-xO4 XRD patterns are due to the formation of Mn2O3 and some other substances during firing. It wasn't integrated spinel structure until heated at 800℃. SEM shows that the samples grew bigger and then became thinner with the calcinations temperature increasing. The particle is fine, inerratic and integrate at 800 heated treatment.