WO2012062111A1

WO2012062111A1 - Processing method of lithium iron phosphate used as positive electrode material of lithium ion battery

Info

Publication number: WO2012062111A1
Application number: PCT/CN2011/075934
Authority: WO
Inventors: 朱杰; 杜振山
Original assignee: 河北力滔电池材料有限公司
Priority date: 2010-11-10
Filing date: 2011-06-20
Publication date: 2012-05-18
Also published as: CN102009969A; CN102009969B

Abstract

A processing method of lithium iron phosphate used as the positive electrode material of a lithium ion battery comprises: 1) wet-treating the lithium iron phosphate material, i.e. processing the lithium iron phosphate material with a wetting agent of 0.1-3% wt. in concentration, to obtain a homogeneous aqueous suspension of lithium iron phosphate material; 2) leaching high active iron ions on the surface of the lithium iron phosphate material with acid solution, i.e. adding an acid solution with pH value of 0-1 into the suspension of lithium iron phosphate under agitation, to keep the pH value of the obtained solution at the range between 1.5-2.5, while rendering a complete reaction by agitating; 3) filtering and drying, i.e. filtering the solution, washing the filtered lithium iron phosphate with distilled water or pure water, and drying the washed lithium iron phosphate material under vacuum condition or protective gas atmosphere to obtain the finished lithium iron phosphate material. The lithium iron phosphate material is carbon coated. The shelf life and high temperature property of the battery can be improved by the method.

Description

Method for processing lithium iron phosphate cathode material lithium iron phosphate

The invention belongs to the technical field of lithium ion batteries, and in particular relates to a method for treating a lithium iron phosphate cathode material. Background technique

At present, the lithium iron phosphate material for lithium ion batteries has unparalleled safety, long cycle life, good high temperature performance and stable discharge platform. It is used in electric vehicles, energy storage batteries and large power tool batteries. The only candidate for the positive electrode material. Lithium iron phosphate materials produced by different processes have considerable performance differences. Among them, the self-discharge problem of lithium iron phosphate material is one of the more serious problems. For example, many solid phase lithium iron phosphate materials have a monthly self-discharge of more than 3%. The carbon coating is good, and the hydrothermal method for producing lithium iron phosphate material has a monthly self-discharge of less than 1%. Materials with high self-discharge generally have high temperature cycling and storage performance. Typical data are: 55°C cycle 300 times attenuation capacity over 20%. According to the literature, this is because Fe203 or other highly active iron compounds remaining in lithium iron phosphate, during the cycle, iron ions continue to electrochemically or chemically dissolve, iron ions migrate to the negative electrode, blocking the lithium ion diffusion channel, thereby Causes a rapid decline in cycle life. After dissecting the battery with poor performance, the separator and the negative electrode will also be brown or yellow, and ion probe chromatography will show a large amount of iron ions. Therefore, the dissolution and migration of iron ions are eliminated, and the self-discharge performance and high-temperature performance of the battery can be effectively improved. Summary of the invention

The present invention provides a method for treating a lithium iron battery positive electrode material lithium iron phosphate in order to solve the problems existing in the prior art.

The object of the present invention is to provide a lithium ion battery cathode material lithium iron phosphate which has the advantages of simple process, convenient operation, excellent material performance, and can effectively improve the shelf life and high temperature performance of the battery, stable product quality, and greatly improved battery performance. Approach. The iron ion elution is prevented from migrating to the negative electrode, and the lithium ion diffusion channel of the negative electrode is prevented from being clogged, thereby improving the self-discharge and high-temperature performance of the lithium iron phosphate material.

The technical principle of the present invention is: First, the wettability of the lithium iron phosphate material is improved, and then the high activity iron ions on the surface of the lithium iron phosphate are leached with an acid solution. The acidity of the solution is such that the high-activity iron ions are dissolved without dissolving the lithium iron phosphate, and the pH of the solution is controlled to be between 1. 5 and 2.5. After leaching high-activity iron ions, the lithium iron phosphate material is washed and dried to obtain a desired lithium iron phosphate material.

The method for treating the lithium iron phosphate cathode material of the present invention adopts the following technical scheme:

A lithium ion battery cathode material lithium iron phosphate treatment method, characterized in that: lithium ion battery cathode material lithium iron phosphate treatment process includes:

1) Wetting treatment of lithium iron phosphate material: firstly treating phosphorus with a wetting agent of 0.1 to 3% by weight a lithium iron phosphate material, forming a carbon-coated lithium iron phosphate material to form a uniform aqueous suspension;

2) Leaching the high-activity iron ions on the surface of the lithium iron phosphate with an acid solution: Adding the acid solution having a pH of 0-1 to the lithium iron phosphate suspension under stirring to maintain the pH of the final solution at 1. 5-2. 5, stirring to make the system fully react;

3) Filtration and drying: The solution is filtered, and the filtered lithium iron phosphate is washed with distilled water or purified water; the washed lithium iron phosphate material is dried under vacuum or a protective gas atmosphere to obtain a final lithium iron phosphate material. .

The method for treating the lithium iron phosphate cathode material of the present invention can also adopt the following technical measures: The lithium ion battery cathode material lithium iron phosphate treatment method is characterized in that the wetting agent is ethanol, methanol, acetone or butyl. Ketone organic solvent. It can wet the surface of lithium iron phosphate material, and it can be dissolved infinitely with water. At the same time, it will evaporate during the drying process without affecting the performance of the system.

The lithium ion battery cathode material lithium iron phosphate treatment method is characterized in that: when the wetting agent treats the lithium iron phosphate material, the weight ratio of the lithium iron phosphate material to the wetting solution is 1: 1-10.

The method for treating a lithium iron battery positive electrode material lithium iron phosphate is characterized in that: the acid in the acid solution is nitric acid and oxalic acid. Both acids can reach a pH of 0-1, and the trace acid remaining after washing can be evaporated or sublimated during the subsequent drying process without affecting the performance of the system.

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Stir between 1 and 3 hours between -2.5.

The method for treating a lithium iron battery positive electrode material lithium iron phosphate is characterized in that: the protective gas is nitrogen, argon, helium or a mixed gas of one or more of them.

The lithium ion battery cathode material lithium iron phosphate treatment method is characterized in that: the filtered lithium iron phosphate is washed twice with steamed water or pure water of 10-20 times weight of lithium iron phosphate material, and the operation control temperature is 10-25 ° C.

The method for treating a lithium iron battery positive electrode material lithium iron phosphate is characterized in that: the drying temperature is 180-250 ° C under vacuum conditions or a protective gas atmosphere.

The invention has the advantages and positive effects:

Lithium ion battery cathode material lithium iron phosphate treatment method, due to the use of the novel technical solution of the invention, compared with the prior art, the invention produces lithium iron phosphate cathode material, after acid washing, the surface of high activity iron ions The magnitude is reduced. After being assembled into a lithium iron phosphate battery, the iron dissolution of the positive electrode is greatly reduced, and the battery life and high temperature performance are effectively improved. The lithium iron phosphate battery treated by the invention has a monthly self-discharge reduction of 0.8%, and the 55 °C high temperature 1C/300 cycle decay rate is reduced from the original 20% to 11.6%, and the battery performance is greatly improved.

The invention has the advantages of simple process, convenient operation, excellent material performance, effective improvement of the shelf life and high temperature performance of the battery, stable product quality, and greatly improved battery performance. detailed description

In order to further understand the technical content, features and effects of the present invention, the following examples are listed, and Next:

Example 1

Lithium ion battery cathode material lithium iron phosphate treatment method, firstly prepared 100 kg 0.1% concentration of ethanol water solution. After mixing, slowly add 10 kg of lithium iron phosphate powder material to stir into a uniform suspension. Then, 50 kg of a nitric acid solution having a pH of 0 was prepared, and the nitric acid solution was slowly added to the lithium iron phosphate suspension under stirring, and the pH of the final solution was 2.5%. After reaching the set pH value, the mixture was stirred for 1 hour, and then the solution was filtered to filter out the lithium iron phosphate material therein. Wash twice with 150 kg of distilled water. All of the above operating ambient temperatures and solution temperatures are 25 °C. The washed lithium iron phosphate material. Dry at 200 ° C under vacuum to constant weight (completely dried) to obtain the final product.

Example 2

For the treatment of lithium iron phosphate as a positive electrode material for lithium ion batteries, firstly, 1000 kg of a 3% concentration of butanone aqueous solution is prepared. After the preparation, slowly add 1000 kg of lithium iron phosphate powder material to stir into a uniform suspension. Then, 4000 kg of a nitric acid solution having a pH of 1 was prepared, and the nitric acid solution was slowly added to the lithium iron phosphate suspension under stirring, and the pH of the final solution was 1.5. After reaching the set pH value, the mixture was stirred for 3 hours, and then the solution was filtered, and the lithium iron phosphate material was filtered off. Wash twice with 20,000 kg of steamed water. All of the above operating ambient and solution temperatures are 15 °C. The washed lithium iron phosphate material. Dry to 200 ° C under an argon atmosphere to constant weight (completely dried) to obtain the final product.

Example 3

For the treatment of lithium iron phosphate cathode material lithium iron phosphate, first prepare 500 kg of 1% methanol aqueous solution. After the preparation, slowly add 100 kg of lithium iron phosphate powder material to stir into a uniform suspension. Prepare 600 kg of oxalic acid solution with a pH of 0.5, and slowly add the oxalic acid solution to the lithium iron phosphate suspension under stirring, with the pH of the final solution reaching 2. 0. After reaching the set pH value, the mixture was stirred for 2 hours, and then the solution was filtered to filter out the lithium iron phosphate material therein. Wash twice with 1500 kg of distilled water. All of the above operating ambient temperatures and solution temperatures are 25 °C. The washed lithium iron phosphate material. Dry at 200 ° C under vacuum to constant weight (completely dried) to obtain the final product.

The lithium iron phosphate cathode material prepared by the invention has been subjected to acid washing, and the surface active iron ions are greatly reduced. After being assembled into a lithium iron phosphate battery, the iron dissolution of the positive electrode is greatly reduced, and the battery life and high temperature performance are effectively improved.

Claims

Claim

A lithium ion battery cathode material lithium iron phosphate treatment method, characterized in that: lithium ion battery cathode material lithium iron phosphate processing process includes:

1), the wetting treatment of the lithium iron phosphate material: firstly treating the lithium iron phosphate material with a wetting agent of 0.1-3% by weight, so that the carbon-coated lithium iron phosphate material forms a uniform aqueous suspension;

2), leaching high-activity iron ions on the surface of lithium iron phosphate with an acid solution: adding an acid solution having a pH of 0-1 to a suspension of lithium iron phosphate under stirring to maintain the pH of the final solution at 1.5 Between -2.5, stirring to fully react the system;

3), filter drying: solution filtration, filtered lithium iron phosphate washed with distilled water or purified water; washed lithium iron phosphate material, vacuum or protective gas atmosphere to dry, to obtain the final lithium iron phosphate material.

2. The method for treating a lithium ion battery cathode material lithium iron phosphate according to claim 1, wherein the wetting agent is an organic solvent of ethanol, methanol, acetone or methyl ethyl ketone.

The method for treating a lithium iron battery positive electrode material lithium iron phosphate according to claim 1 or 2, wherein: the weight ratio of the lithium iron phosphate material to the wetting solution is 1 when the wetting agent treats the lithium iron phosphate material. : 1-10.

4. The method for treating a lithium ion battery cathode material lithium iron phosphate according to claim 1, wherein the acid in the acid solution is nitric acid and oxalic acid.

The method for treating a lithium ion battery cathode material lithium iron phosphate according to claim 4 or 5, wherein the weight ratio of the acid solution to the lithium iron phosphate suspension is 1: 0.5-2, and the pH of the final solution Stir for 1-3 hours while maintaining the value between 1.5 and 2.5.

6. The method for treating a lithium iron battery positive electrode material lithium iron phosphate according to claim 1, wherein the protective gas is nitrogen gas, argon gas, helium gas or a mixed gas of one or more of them.

7. The method for treating a lithium ion battery cathode material lithium iron phosphate according to claim 1, wherein the filtered lithium iron phosphate is washed with distilled iron or purified water having a weight of 10-20 times of lithium iron phosphate material. The operating control temperature is 10-25 °C.

8. The method for treating a lithium ion battery cathode material lithium iron phosphate according to claim 1, wherein the drying temperature is 180 to 250 ° C under vacuum or a protective gas atmosphere.