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Method for removing impurities from lithium iron phosphate (LiFePO4) and LiFePO4 battery

A technology of lithium iron phosphate and carbon-coated lithium iron phosphate, which is applied in the direction of battery electrodes, circuits, electrical components, etc., can solve the problems of product residue, damage to material structure, and failure to fundamentally suppress it, so as to reduce self-discharge ability and eliminate Black spots, the effect of improving battery safety performance

Inactive Publication Date: 2015-01-07
HUAWEI TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] In the process of realizing the present invention, the inventors have found that the prior art has at least the following problems: the existing schemes are all carried out under water system conditions, and the removal of impurities with distilled water can only remove water-soluble impurities in the material, and the water-insoluble Fe elemental and compound removal is not ideal
However, the pH buffer solution is used to clean lithium iron phosphate, and the buffer solution reacts with Fe metal and oxides in the material, which is likely to destroy the material structure and affect the electrochemical performance of the material.
Even in the case of ensuring that the structure of the material itself is not destroyed, it is impossible to fundamentally inhibit the soluble Fe 3+ , Fe 2+ hydrolysis, the hydrolyzed products still remain in the material

Method used

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  • Method for removing impurities from lithium iron phosphate (LiFePO4) and LiFePO4 battery
  • Method for removing impurities from lithium iron phosphate (LiFePO4) and LiFePO4 battery
  • Method for removing impurities from lithium iron phosphate (LiFePO4) and LiFePO4 battery

Examples

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Effect test

Embodiment 1

[0041] Weigh 10.00g of carbon-coated lithium iron phosphate from the domestic manufacturer a, soak it in 120ml of HF aqueous solution with a pH of 3.5, stir rapidly, and keep it warm at 40°C to detect the change of the pH value of the system. When the pH rises to 4, drop Add HF aqueous solution with a pH value of 2 to keep the pH of the reaction system at 4.0, react for 100 h, and monitor the iron content in the solution. Then filter, wash the filtered residue with absolute ethanol, wash three times, dry at 100°C for 6h, dry, grind to obtain the treated material, and then place the treated material in a muffle furnace under argon protection Calcined at 100°C for 6 hours to obtain lithium iron phosphate material.

Embodiment 2

[0043] Weigh 10.00g of carbon-coated lithium iron phosphate from domestic manufacturer a, soak it in 120ml of HCl aqueous solution with a pH of 4.0, stir rapidly, and keep it warm at 60°C to detect the change of the pH value of the system. When the pH rises to 4.5, add dropwise HCl aqueous solution with a pH value of 3 keeps the pH of the reaction system constant at 4.5, reacts for 40 hours, and monitors the iron content in the solution after soaking. Then filter, wash the filtered residue with anhydrous methanol, wash four times, dry at 100°C for 6h, dry, grind to obtain the treated material, and then place the treated material in a muffle furnace under nitrogen protection Calcined at 600°C for 1 hour to obtain lithium iron phosphate material.

Embodiment 3

[0045] Weigh 10.00 g of carbon-coated lithium iron phosphate from domestic manufacturer b and soak it in 120 ml of H with a pH of 3.5. 3 PO 4 In the aqueous solution, stir rapidly and keep warm at 80°C to detect the change of the pH value of the system. When the pH value rises to 4, add dropwise H 3PO 4 aqueous solution, keep the pH of the reaction system constant at 4, react for 6 hours, and monitor the iron content in the solution after soaking. Then filter, wash the filtered residue with diethyl carbonate (DEC), wash three times, dry at 100°C for 6h, dry, grind to obtain the treated material, and then place the treated material in a muffle furnace , and roasted at 200°C for 3h under the protection of nitrogen to obtain lithium iron phosphate material.

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Abstract

The invention discloses a method for removing impurities from lithium iron phosphate (LiFePO4) and a LiFePO4 battery. The method comprises the following steps of: soaking a carbon-coated LiFePO4 material in an inorganic acid aqueous solution with the pH value of 3.5-8.0, stirring, carrying out heat preservation at the temperature of 40-90 DEG C, and detecting the change of a pH value of a system; when the pH value is increased to 4.0-8.0, dropwise adding an inorganic acid aqueous solution with the pH value of 1-6.0 so as to enable the pH value of a reaction system to constantly be 3.5-8.0; carrying out reaction for 1-100 hours at the temperature of 40-90 DEG C, filtering, cleaning a residue obtained through filtering by using an organic solvent, drying and grinding the residue so as to obtain the processed material; and then, calcining the material under the protection of inert gas to obtain the LiFePO4 which is subjected to impurity removal. The battery contains the LiFePO4 which is subjected to impurity removal. According to the embodiment of the invention, the impurities, such as Fe simple substance, FeO, Fe2O3, Fe2P and the like, can be removed without destroying Fe in the LiFePO4, so that black spots on the cathode and a diaphragm in the battery are eliminated, the self-discharge capacity of the battery is lowered, and the safety performance of the battery is improved.

Description

technical field [0001] The invention relates to a method for removing impurities, in particular to a method for removing impurities in lithium iron phosphate and a battery thereof. Background technique [0002] At present, lithium-ion batteries are increasingly used in communications, transportation, computers and other industries all over the world, providing countless conveniences for people's lives. The preparation materials of lithium-ion batteries have also attracted people's attention. Lithium-ion battery cathode active material selection olivine-type LiFePO 4 , olivine-type LiFePO 4 The source of raw materials is abundant, the price is low, the environment is friendly, the heat stability and safety number are high, the specific capacity is high, and the cycle life is long. The synthesis of lithium iron phosphate mainly includes solid-phase method, liquid-phase method, co-precipitation method, etc. In the existing method, due to uneven mixing or uneven reaction, im...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/58
CPCY02E60/10
Inventor 丁杰
Owner HUAWEI TECH CO LTD
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