| The lithium-ion batteries have various advantages,high voltage,high specific capacity,high energy density,no memory effect,longer life and calender life,environment friendly and so on.Therefore,the lithium-ion batteries(LIB)is widely used in electric vehicle and hybrid electric vehicle.Cathode materials is the key material for LIBS,they play the crucial role for the performance of LIBS.Olivine-type lithium iron phosphate(LiFePO4)becomes more attractive for its high capacity(170mAh/g),nontoxicity,environment friendly and high safety.etc.LiFePO4 as cathode material,its charge and discharge curve is formed by a high level of horizontal and sudden drop,the verticality of high vertical is nonlinear relationship between voltage and capacity,making it difficult to calculate the battery SOC by measuring the battery voltage and brings inconvenience for calculate the battery capacity to the battery management systems.In the view of existing problems,the lithium-ion battery cathode material LiFePO4 cathode material are doped and modified,and on this basis,according to the practical application of lithium-ion battery,the first time pure electric tourist raft is made with lithium-ion battery as power,and test its dynamic performance in Lijiang river in GuiLin,through the practical application to find and solve the problem of lithium-ion battery.(1)The motor raft in the tourism essence period of the LiJiang river in GuiLin who have big noise,severe pollution and energy consumption problems.Then the plan that the motor raft are replaced by pure electric raft with as-prepared LiFePO4/Li2FeSiO4/C composite lithium-ion battery as power is proposed after research.Ensure the safety of the pure electric raft,the low voltage and high current lithium-ion battery pack for the electric tourist raft was determined.Separate the 72V200Ah lithium-ion battery power model as four 18V200Ah lithium-ion battery pack,convenient installation and transportation.The pure electric tourist raft drive system was composed of low voltage and high power density permanent magnet motor,low pressure waterproof permanent magnet motor drive controller and the control system.Concluded the pure electric tourist raft is limited by production technology,and between the lithium-ion battery exists the difference of capacity,voltage,resistance and so on.And the equilibrium strategy of battery cell and the battery equalization technology becomes the key technology of lithium-ion battery power module manufacturing.(2)Using LiOH、TEOS and FeCl2 as raw materials and Li2FeSiO4 was synthesized by hydrothermal methode.Different hydrothermal time and hydrotherma temperature effect on the morphology and structure of the Li2FeSiO4 cathode material are studied,and electrochemical performance are test,found that when the hydrothermal time is 24h and hydrotherma temperature is 180℃,the product most fusiform and relatively uniform while the material long size is 1.5um and width is 300nm.With the increase of hydrothermal time,the crystallinty of the material is better and with the increase of hydrotherma temperature,the structure of the material appear complex phase.Through carbon coating can improve the electrical conductivity of Li2FeSiO4 cathode material,we use glucose as carbon source and research the mount of carbon coated influence on the structure and properties of the material.And found that when the amount of glucose is wt-10%,the material has the best electrochemical performance,its first discharge specific capacity is159.2mAh/g at 0.2C and after 100 cycle its specific capacity is169.3mAh/g.The Li2FeSiO4/C-10%material under different discharge rate at 0.2C,0.5C,1C,2C and 5C,its ischarge specific capacity is159.2mAh/g,147.6mAh/g,136.7mAh/g,125.4mAh/g and 110.2mAh/g.When after 5C discharge rate back to 1C,its discharge specific capacity get good recovery and show its good capacity retention.(3)Commercial LiFePO4 and as-prepared Li2FeSiO4 as raw material,Span-80 as carbon source,prepared LiFePO4/LiFeSiO4/C composite after simple physical mixing and calcination.Through test of XRD,EDS and XPS,it can be seen that the composite are formed with LiFePO4 and Li2FeSiO4 uniform mixing After charge and discharge test,found that the there is a small slope in the composite discharge platform than the LiFePO4.The initial discharge capacity of the composite and LiFePO4 are 153mAh/g,and after 50 cycles,the discharge capacity of the composite is 152.8mAh/g.It can be seen that the slope platform didn’t disappear when the composite discharge at different rate.Through the graph of the SOC change with the battery voltage,found that the composite voltage began to slowly decline when the battery capacity was 30%,and the commercial LiFePO4 is 10%.The accuracy of the LiFePO4 battery SOC estimation was improved with the slop platform. |
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