Preparation And Performance Study Of Rich Lithium Material Li_1.2Ni_0.13Co_0.13Mn_0.54O₂

Rich lithium material xLi2MnO3·(1-x)LiMO2has been mainly researched inrecent years because it has the advantages of LiNiO2, LiCoO2and LiMn2O4. However,its cycle capability and rate capability remains to improve. In this paper,Li1.2Ni0.13Co0.13Mn0.54O2is prepared by sol-gel method and optimized synthesistechnology in order to obtain the best reaction condition. Besides, the material iscoated to improve its rate capability and cycle capability.In this paper, Li1.2Ni0.13Co0.13Mn0.54O2is synthesized by sol-gel method firstly andcharacterized and analyzed by testing measures such as XRD, SEM. Theelectrochemical capability was researched testing measures such as charge anddischarge technology, cycle voltammograms and electrochemical impedancespectroscope. According to experimental results, the optimal flowsheet was obtained:Aerogels prepared by sol-gel method was calcined at900°C for10h in flow air afterbeing decomposed at550°C for5h in air. LiNO3was regarded as lithium source withan excess of5%. In this condition，the material had a typical layered structure ofα-NaFeO2.The material had a well distributed morphology and a low ion mixeddegree. The results showed that the initial discharge specific capacity ofLi1.2Ni0.13Co0.13Mn0.54O2was207.96mAh/g and the highest discharge specificcapacity was222.13mAh/g in2.0~4.8V at0.1C (1C=278mAh/g) rate. After30cycles,the discharge specific capacity was210.32mAh/g, which still retained94.7%.AlF3was coated on the surface of the material and the results indicated that aftercoating AlF3, the layered structure was not been changed. But the initial dischargespecific capacity was reduced at0.1C.That was because AlF3has no activity，whichlead to the percentage of active substance in material decreased. The cycle capabilityhad a great performance evidently. After20cycles, the discharge specific capacity of3%AlF3was188.19mAh/g, which still retained95.4%. The rate capability wasimproved for which the reaction between the material and the electrolyte was avoidedbecause they were separated by AlF3. Compared different coating amount,3%wasregarded as a better one to improve the capability of the material.CeO2was coated on the surface of the material and the results indicated that aftercoating CeO2, the layered structure was not been changed. The ion mixed degree waslowered obviously when the coating amount was1%. The initial discharge specific capacity was reduced at0.1C.That was because the percentage of active substance inmaterial decreased. However, the irreversible capacity loss was lowered by coatingCeO2suitably. The cycle capability had a great performance evidently. After30cycles,the discharge specific capacity of1%CeO2was161.05mAh/g, which retained105.7%.The rate capability was improved for which the reaction between the material and theelectrolyte was avoided because they were separated by CeO2. Compared differentcoating amount,1%was regarded as a better one to improve the capability of thematerial. Compared with1%CeO2, the effect of3%AlF3coated to the material isbetter.