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Method for preparing lithium iron phosphate by hydrothermal method and lithium iron phosphate prepared by method

A lithium iron phosphate and hydrothermal technology, applied in electrical components, battery electrodes, circuits, etc., can solve the problems of complex operation, affecting the pH value of the reaction system, lengthy process, etc., and achieve the goal of inhibiting particle growth, simple preparation method, The effect of high discharge specific capacity

Pending Publication Date: 2016-04-27
SHENZHEN BAK POWER BATTERY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Other methods are complex in operation, lengthy in process and high in cost
[0005] When existing hydrothermal method is used for lithium iron phosphate lithium ion battery cathode material, generally will add surfactant such as polyvinyl alcohol (PVA), polyethylene glycol (EG), sodium dodecyl sulfonate ( CTAB), etc., make lithium iron phosphate precipitates easier to form, and make the crystal grains grow in a certain direction, improve the order of grain growth, and achieve the purpose of controlling the morphology. However, the amount and mechanism of action of surfactants have not yet been Clear; therefore, it is difficult to control the shape and the effect is not ideal
In addition, when the existing hydrothermal method is used to prepare lithium iron phosphate, in order to control the particle size, most researchers choose to add organic substances with strong reducing properties such as glucose, ascorbic acid, and citric acid, while preventing the oxidation of ferrous iron. The purpose of inhibiting particle growth, but adding strong reducing organic matter affects the pH value of the reaction system. If the pH value is too low or too high, a large amount of by-products will be produced in the reaction system, which will affect the quality of lithium iron phosphate; some studies have shown that in strong acid or Lithium iron phosphate cannot even be generated under strong alkaline conditions

Method used

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  • Method for preparing lithium iron phosphate by hydrothermal method and lithium iron phosphate prepared by method
  • Method for preparing lithium iron phosphate by hydrothermal method and lithium iron phosphate prepared by method
  • Method for preparing lithium iron phosphate by hydrothermal method and lithium iron phosphate prepared by method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] In this example, LiOH·H 2 O, H 3 PO 4 and FeSO 4 ·7H 2 O is used as raw material, and the molar ratio of Li:Fe:P is 3:1:1, and the improved hydrothermal method is used to prepare 0.3mol LiFePO 4 . details as follows:

[0037] a. LiOH·H 2 O is prepared into a 3mol / L lithium source solution, and the H 3 PO 4 Prepare a 1.5mol / L phosphorus source solution, slowly add the phosphorus source solution into the lithium source solution in proportion to make a mixed solution A;

[0038] b. FeSO 4 ·7H 2 O is prepared into a 1mol / L iron source solution, and added to the iron source solution to theoretically generate LiFePO 4 20wt.% of the total weight of starch, mixed to make mixed solution B;

[0039] c. Slowly add the mixed solution B into the mixed solution A under mechanical stirring to form a reaction system solution, and transfer the reaction system solution to a 1L reactor for reaction. After the reaction is completed, filter to obtain LiFePO 4 product.

[0040]...

Embodiment 2

[0043] This example is the same as the method of Example 1, wherein the amount of starch added in the iron source solution is theoretically generated LiFePO 4 10wt.% of the total weight, all the other components and consumption are the same.

[0044] For the LiFePO prepared in this example 4 Product is carried out scanning electron microscope observation, it can be seen that the LiFePO prepared in this example 4 The product is prismatic, and as Figure 4 As shown, the particle size is about 1 μm in length and 200 nm in thickness, indicating that the main reason for the change in product morphology is the change in starch content. It can be seen that starch plays a role in inhibiting particle size and controlling the formation of morphology in the system reaction. The high-resolution transmission electron microscope results showed that there were disorderly arranged small particles of lithium iron phosphate on the surface of the product, indicating that the starch acted as a ...

Embodiment 3

[0046] This example is the same as the method of Example 1, wherein the amount of starch added in the iron source solution is theoretically generated LiFePO 4 The 30wt.% of total weight, all the other components and consumption are the same.

[0047] For the LiFePO prepared in this example 4 Product is carried out scanning electron microscope observation, it can be seen that the LiFePO prepared in this example 4 The product is in the shape of a rib, and the particle size is about 1 μm in length and 200 nm in thickness; LiFePO 4 The product is similar to Example 2, and there are small particles of lithium iron phosphate disorderly arranged on the surface of the particles, as shown in the scanning electron microscope Figure 5 As shown, it can be seen that with the change of starch content in the reaction system, there is an obvious trend in the control of particle size and shape. At 20wt.%, spherical lithium iron phosphate products can be prepared, and diamond-shaped granula...

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Abstract

The invention discloses a method for preparing lithium iron phosphate by a hydrothermal method and the lithium iron phosphate. The method disclosed by the invention comprises the following steps: only adding a lithium source, an iron source, a phosphorus source and a natural neutral water-soluble polymer to a reaction system solution; and filtering the reaction system solution after the reaction system solution reacts in a reaction kettle, so as to obtain an LiFePO<4> product. According to the method disclosed by the invention, a traditional surfactant and a strongly organic reducing substance are replaced with the natural neutral water-soluble polymer, the shape and form, the particle size and the particle size distribution of a lithium iron phosphate product can be simply and effectively controlled; impurities caused by oxidation of ferrous iron at a high temperature can also be prevented; the pH value of a reaction system is not affected by the neutral water-soluble polymer; the reducing substance formed by cracking at the high temperature also plays a role in inhibiting particle growth; and the production quality of the lithium iron phosphate is improved. With the lithium iron phosphate as a cathode material for a lithium-ion battery, the specific discharge capacity is high; the cycle performance is good; and a foundation is laid for application of the lithium-ion battery in the field of an industrial large battery.

Description

technical field [0001] The present application relates to the field of preparation of positive electrode materials for batteries, in particular to a method for preparing lithium iron phosphate by a hydrothermal method. Background technique [0002] Lithium-ion batteries were introduced to the market by Sony Corporation of Japan in the 1990s. Because of their high operating voltage, high energy density, and long cycle life, they are widely used in mobile phones, laptops and other small mobile power fields. With the further improvement of the energy density and power density of lithium-ion batteries, it has been regarded as an ideal power source for hybrid electric vehicles and pure electric vehicles, and is a type of energy storage device with broad application prospects; it has been further developed into aerospace applications. [0003] At present, the commercial application of lithium-ion battery cathode material has LiCoO 2 , Li 2 MnO 2 , LiFePO 4 and LiNi (1-x-y) co...

Claims

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Application Information

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IPC IPC(8): H01M4/1397H01M4/136
CPCY02E60/10
Inventor 杜炳林林建陈邦义
Owner SHENZHEN BAK POWER BATTERY CO LTD
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