Method of preparing lithium iron phosphate cathode material through hydrothermal method, and the cathode material

A technology for lithium iron phosphate and positive electrode materials, which is applied in the direction of chemical instruments and methods, phosphorus compounds, battery electrodes, etc., can solve the problem of not being able to significantly improve the electronic conductivity of lithium iron phosphate positive electrode materials, shorten the distance of lithium ion transmission paths, and improve The effect cannot be continued, etc., to achieve the effect of small particle size, low cost, and anti-dropping

Pending Publication Date: 2016-05-18
SHENZHEN BAK POWER BATTERY CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, pure LiFePO 4 There are two major disadvantages of low electronic conductivity and small diffusion coefficient of lithium ions. Researchers have improved LiFePO by coating carbon layers or conductive polymers, and doping high-valence cations. 4 Electronic conductivity; and by reducing the particle size, thereby shortening the lithium ion transport path distance, in order to improve the LiFePO 4 Li-ion diffusion coefficient of
Coating invisible carbon is the simplest and most reliable improvement method, but there are also some shortcomings. During the cha

Method used

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  • Method of preparing lithium iron phosphate cathode material through hydrothermal method, and the cathode material
  • Method of preparing lithium iron phosphate cathode material through hydrothermal method, and the cathode material
  • Method of preparing lithium iron phosphate cathode material through hydrothermal method, and the cathode material

Examples

Experimental program
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Effect test

Embodiment 1

[0042] In this example, LiOH·H 2 O, H 3 PO 4 and FeSO 4 ·7H 2 O is used as a raw material, and the molar ratio Li:Fe:P is 3:1:1 for batching to prepare 0.3mol of LiFePO 4 . details as follows:

[0043] 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, then slowly add the phosphorus source solution into the lithium source solution to make a mixed solution A; 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 was mixed to make a mixed solution B; under the action of mechanical stirring, the mixed solution B was slowly added to the mixed solution A to form a reaction system solution, and the reaction system solution was transferred to 1L volume of reaction The reaction is carried out in the kettle; the filling volume of the reaction kettle is 80%, the pH value of the reaction sys...

Embodiment 2

[0047] This example will press LiFePO 4 The 4wt.% phenolic resin of product and the carbon-coated LiFePO that embodiment one prepares 4 The product was mixed evenly by ball milling to obtain the post-treatment precursor; the post-treatment precursor was calcined at 750°C for 12 hours in a flowing nitrogen atmosphere, and cooled after calcining to obtain a spherical LiFePO with double-layer coating morphology. 4 / C / PAS.

[0048] The high-resolution transmission electron microscope image of the double-coated lithium iron phosphate cathode material prepared in this example is as follows Figure 5 As shown in the figure, PASlayer is the conductive polymer coating layer, and carbonlayer is the carbon coating layer, which proves that the product has a double-layer coating effect.

[0049] X-ray diffraction analysis and detection shows that the diffraction pattern of the double-coated lithium iron phosphate cathode material prepared in this example is consistent with the standard ...

Embodiment 3

[0054] According to the hydrothermal method of Example 1, lithium iron phosphate was mixed with 4wt.% glucose of lithium iron phosphate weight, roasted at 750 ° C for 12 hours, and ball milled after cooling to obtain a spherical carbon-coated lithium iron phosphate material. .

[0055] After inspection, the initial discharge capacity at 0.2C rate current is 155.8mAh / g, and it maintains 133.2mAh / g after 50 cycles at 1C, which is as high as 97.9% relative to the initial capacity retention at 1C.

[0056] It can be seen that the effect of invisible carbon coating on the products prepared by the hydrothermal method is relatively poor. The main reason is that the invisible carbon coating layer is eroded by the electrolyte during the electrochemical process of the battery and is easy to fall off, resulting in poor battery performance. Therefore, comparatively speaking, the double-layer coating effect of Example 2 is better, and both the initial charge and discharge capacity and cycl...

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Abstract

The application discloses a method of preparing a lithium iron phosphate cathode material through a hydrothermal method, and the cathode material. The method includes the steps of preparing carbon-coated LiFePO4 through the hydrothermal method and coating the carbon-coated LiFePO4 with a conductive polymer, wherein the preparation of the carbon-coated LiFePO4 through the hydrothermal method includes a step of only adding a lithium source, an iron source, a phosphorus source and a natural neutral water-soluble high molecular substance to a reaction system solution to prepare the carbon-coated LiFePO4; and the conductive polymer coating step includes the operations of 1) uniformly mixing the carbon-coated LiFePO4 with a resin-type high molecular substance through ball milling; and 2) performing high-temperature calcination to the mixture under a nitrogen atmosphere to obtain the lithium iron phosphate which is coated by both the conductive polymer and the carbon in a double-layer manner. In the application, the lithium iron phosphate is coated by both the conductive polymer and the carbon in a double-layer manner for the first time, wherein not only is excellent electric conductive efficiency ensured but also carbon is prevented from stripping off, so that the cathode material is improved in performance, is high in specific discharge capacity, is good in cycle performance and is low in cost, and establishes a basis for application of lithium ion batteries in the field of industrial macrocells.

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 positive electrode materials by using a hydrothermal method, and the prepared lithium iron phosphate positive electrode materials. 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] LiFePO 4 As a high-capacity lithi...

Claims

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Application Information

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IPC IPC(8): H01M4/58C01B25/45
CPCY02E60/10
Inventor 杜炳林陈邦义祖文林
Owner SHENZHEN BAK POWER BATTERY CO LTD
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