The effect of doping on the electrochemical performance was studied for spinel type Li1.02MxMn2-xQyO4-y used as cathode material in lithium-ion battery. TG/DTA curves of the precursor (the raw materials) doped with different elements were studied. The spinel materials Li1.02Mn2O4, Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98, Li1.02Co0.02Cr0.01 La0.01Mn1.96Cl0.02O3.98, Li1.02Co0.02La1.02Mn1.97Cl0.02O3.98, Li1.02Co0.02Cr0.01Mn1.97O4, were prepared by solid-state reaction method after the pretreatment of conversion under low temperature and uniform mixing. X-ray diffraction patterns showed that all the samples had perfect spinel structure. SEM indicated that the particles of the samples had uni- form size and were distributed evenly. The results of the charge/discharge curves showed that Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98 had better performance than other materials according to the inhibition of decline of reversible capacity of spinel Li1.02MxMn2-xQyO4-y. Therefore, cycle performance had been improved so obviously that 93.9% of the initial capacity were preserved after 100 cycles. Furthermore, electrochemical impedance tests were carried out with the spinel Li1.02Co0.02Cr0.01La0.01Mn1.96F0.02O3.98 as working electrode, Lithium as counter elec- trode and reference electrode. Results showed that this material possessed good charge/discharge reversible capa- bility and had the lowest impedance in 3.95￣4.25 V range (on the stage of charge / discharge).
The application of cyclohexyl benzene(CHB)as the overcharge protection additive in lithium ion batteries was analyzed.Through 1C overcharge testing,battery performance testing, electrochemical impedance testing,electrolyte conductivity and self-discharge testing,the use of cyclohexyl benzene as the overcharge protection additive and the effect of cyclohexyl benzene on battery performance were investigated.The possible mechanism of cyclohexyl benzene as the overcharge protection addtive was discussed.When the content of cyclohexyl benzene was more than 5%(mass),the battery could be protected from explosion.When the content of the cyclohexyl benzene exceeded 7%(mass),a detrimental effect on battery performance was found.Cyclohexyl benzene could also decrease electrolyte conductivity,leading to increased self-discharge.The proper content of cyclohexyl benzene was between 5%(mass) and 7%(mass).
