Morphology Controllable Of Ultra-Fine Phosphate And Jphosphate Lithium Composite Preparation, Characterization And Small Scale Preparation Research

The lithium iron phosphate and lithium manganese phosphate were synthetized by carbothermal reduction using superfine iron phosphate or manganese phosphate as precursor respectively. The iron phosphate or manganese phosphate were prepared by complexing-homogeneous precipitation method. The samples were analyzed with SEM, XRD, TG/DTA, FT-IR and particle size distribution. Studied the influence of iron phosphate and manganese phosphate morphology and particle sizes by surfactants concentration, reaction temperature, reactant concentration, pH and reaction time. Tests charge-discharge cycle performance of lithium iron phosphate and lithium manganese phosphate. In the end, experimented iron phosphate at the small scale. The main results were as follows:1.The nanoscale of primary particle iron phosphate and manganese phosphate was prepared with complexing-precipitation by using EDTA as complexing agent and surfactant as morphology and particle size control agent. SEM shows that the primary particle size of iron phosphate particle is100～200nm, the average of secondary particle diameter is1.85μm.Columnar of manganese phosphate particle size is1～5μm of length,100～500nm of width. TG/DTA and FI-IR analysis showed that iron phosphate formula is FePO4·2H2O, and the manganese phosphate formula is Mn3(PO4)2·3H2O. XRD results show that iron phosphate and manganese phosphate are monoclinic system, iron phosphate material phase structure parameters are:space group P1321(152), crystal cell parameters a=5.036A, b=5.036A, c=11.255A. Manganese phosphate phase structure parameters were:the space group C2/m (12), a=6.633A,b=8.584A, c=4.546A.2. The average of iron phosphate particle size has decreases with the increases of surfactant concentration, which prepared by complexing-precipitation method. Iron phosphate average particle size is1.85μm when the surfactant concentration at5g·L-1. The iron phosphate particle average size is increasing with the increase of reaction temperature, reaction time and iron concentration. Most of the iron phosphate particle which prepared by complexing-precipitation is tending to be spherical.3. With complexing-homogeneous precipitation method, homogeneous precipitation method preparation of two kinds of iron phosphate as precursors, monohydrate lithium hydroxide as the source of lithium, sucrose and battery graphite as the reducing agent and carbon source, using carbothermal reduction method to prepare lithium iron phosphate. The XRD and FT-IR results revealed that the the two methods of preparation of lithium iron phosphate as high crystallinity of pure phase. Through the assembly simulation of battery to test the charge-discharge performance of lithium iron phosphate at0.5C, the first discharge specific capacity of the former is163.8mA·h·g-1, and the latter of first discharge specific capacity is only95mA·h·g-1. In the end, the studied of influence by different particle size, carbon content, reaction time and reaction temperature showed that the carbon content at6%, roast temperature at700℃and the roast time at10h when the charge-discharge specific capacity of the lithium iron phosphate is g the highest.4. The charge-discharge of lithium manganese phosphate is very low, which one was prepared by carbothermal reduction with the complexing-homogeneous precipitation synthesis of manganese phosphate as precursor. And the change of reaction temperature was little infecting to it.5. With the optimization of the preparation condition of lithium iron phosphate and lithium iron phosphate, to expanse the test of preparing iron phosphate and lithium iron phosphate. The first charge-discharge of lithium iron phosphate was116.1mA·h·g-1at0.5C. After50cycle numbers, the specific capacity was increasing at120.3mA·h·g-1, the cycling efficiency was104%, and these showed that the cycle performance stability of this product is very good. Compared with the business of lithium iron phosphate products, our products of charge-discharge performance is slighter good, and have further enlarge pilot production requirement.