The Improvement Of Spinel Manganic Acid Lithium Used For Lithium-Ion Battery Cathode Material

The spinel manganic acid lithium is promising to be cathodes for Li-ion battery, due to its relatively high energy density and low toxicity. However, the capacity of spinel manganic acid lithium fades rapidly in the charge-discharge cycle process. It has been suggested that the capacity fading is due to Jahn-Teller distortion , dissolution of manganese into the electrolyte and decomposition of the electrolyte.In this dissertation, two methods are adopted to prepare spinel manganic acid lithium. One is combustion method, the other is separate sect sintering method. In method one, manganese nitrate(50%wt,aqueous solution), lithium nitrate and carbamide are adopted to prepare spinel manganic acid lithium. This section also discusses some factors which affect the spinel manganic acid lithium's performance. They are the way of heating, the amount of CO(NH2)2 and LiNO3, replacing part Mn(NO3)2 with MnCO3. In method two,Li2CO3, electrolytic manganese dioxide and NH4HCO3 are used as reactants to prepare spinel manganic acid lithium. This section also discusses some factors which affect the spinel manganic acid lithium's performance. The factors include technics(such as sinter temperature, reactant molar ratio and sinter time), doping CoSO4,NiSO4,Cr2O3,CrO3.This dissertation uses X-ray apparatus to characterize the material made by both methods. And the material is proved to be spinel manganic acid lithium. Two electrodes laboratory battery is made using spinel manganic acid lithium as cathode material. Three electrodes laboratory battery is also made by adding lithium bar as reference electrode on the basis of two electrodes laboratory battery. PCBT-32D-B programmable battery testing system and LK98BII computer electric chemistry analysis system are adopted to test the character of discharging under constant current and cycle voltammetric of two and three electrodes laboratory battery respectively, in this way, this dissertation study and optimize the technique of making spinel manganic acid lithium.This dissertation finds some optimized technics to prepare spinel manganic acid lithium and some meaningful results. When the molar ratio of LiNO3:Mn(NO3)2:CO(NH2)2 is 1.1:2:3, the first step temperature is 600℃, the material is sintered under 800℃ for 10h at the second step, the performance of the materials obtained are better. Further more, for the sake of economy and environment protection, part of the reactant Mn(NO3)2 can be replaced by MnCO3. In scheme two, when the first stem temperature is 650℃, the molar ratio of Li2CO3:MnO2:NH4HCO3 is 1:4:2, the performance of the materials obtained are better. The performance of the spinel manganic acid lithium made is better when dope CoSO4,NiSO4,Cr2O3 and CrO3 during preparation. The reason why the doping is helpful is that those ion used to dope have stronger bond energy and similar ion radius and octahedron selection energy compared with manganese ion. The spinel manganic acid lithium materials have best performance when Li2CO3:MnO2:CoSO4(NiSO4):NH4HCO3(molar ratio) is 1.02:4:0.02:2.02 and Li2CO3:MnO2: Cr2O3,(CrO3):NH4HCO3(molar ratio) is 1.02:4:0.04:2.02.The dissertation is helpful for further improvement of spinel manganic acid lithium.