Research Of High Performance LiMn₂O₄/C Composite In Lithium Ion Batteries

To reduce the dependence on traditional energy and consumption, most countriesin the world are developing electric vehicles with clean energy. In this paper, spinelLiMn2O4was thoroughly analyzed as a no-pollution, low price cathode material inLithium-ion battery. Synthesized by sol-gel method, tested with the guidance of theuniformity test design experiment, the reasonable optimization of experiment parametersmakes the material we made simplified the preparation processes and show betterperformance. From the results we can see that coating the surface of LiMn2O4materialscan reduce the phenomenon of coated particles after the reunion, which also effectivelyimprove the charge and discharge performance of LiMn2O4.LiMn2O4was prepared by sol-gel method. In the citric acid-nitrate system, or citricacid-acetate system under300?presintered for6h, other10h calcinated under650?would get pure phase LiMn2O4. The XRD and SEM shows that the sample made in citricacid-acetate system reveals smaller particle size and better morphology consistency;whereas the sample made in citric acid-nitrate system represents better specific capacityof113.7mAh/g and107.1mAh/g during first charge and discharge under0.1C. Samplesof citric acid-acetate system under0.1C and0.5C ratio, capacity remains at a rate of97.7%and95.7%, higher than that of the citric acid-nitrate system which are88.0%and94.4%, considering that citric acid-acetate system is more suitable for the preparation ofLiMn2O4.By uniform design to arrange test, according to the selected citric acid-acetatecomplexation system, take seven factors which influence the LiMn2O4cathode materialperformance into consider: Lithium-manganese mole ratio, the dosage of citric acid, thesolution PH, presintering temperature, burning time, burning temperature and burningtime. With12groups of tests, inspecting the specific discharge capacity for the first cycleunder0.1. The LiMn2O4can be synthesised when the molar ratio of metal ions and thecitric acid is3:2. Through the establishment of the linear regression equation andcalculating the optimal solution, we deem that there is no linear relationship between the7factors. With the established nonlinear neural network model of GRNN, worked out theparameters of sol-gel method prepared for LiMn2O4. the first0.1C discharge nonlinearrelationship model of the target, for citric acid-acetate complexation system LiMn2O4cathode material preparation to provide theoretical guidance.Graphene oxide (GO) which covered on LiMn2O4surface with differentproportions is synthesized via modified Hummers method. By the use of polyethyleneglycol (PEG20000), graphene oxide layers are effectively dispersed. LiMn2O4/GOcomposite materials is in the shape of slurry; XRD shows that LiMn2O4/GO is notaffected by the presence of graphene oxide; SEM shows that sample1%GO particles are less aggregation, better dispersion; size of graphene oxide coated layer is about14nm inTEM; tests illustrate the experiment method is feasible; Charge-discharge performance ofthree group coated samples are improved, sample1%GO specific capacity of141.6mAh/g during first charge and discharge under0.1C.discharge capacity is stronger thancommercial LiMn2O4, capacity retention at0.5C and1C ratio is also higher than othergroups. So, the best dosage of coated graphene oxide is1wt%.