阅读说明：本技术 一种废旧磷酸铁锂材料的修复方法 (Method for repairing waste lithium iron phosphate material ) 是由 刘智勇 姜子昂 刘左伟 文达 曹睦林 刘志宏 李启厚 于 2020-04-03 设计创作，主要内容包括：本发明涉及一种废旧磷酸铁锂材料的修复方法,包含以下步骤：1)测定废旧磷酸铁锂材料Li、Fe、P元素的含量；2)配置含有锂盐,铁盐和磷酸的混合溶液,按最终化学计量比Li:Fe:P＝0.75～1.25:1:1加入所述废旧磷酸铁锂材料至所述混合溶液中,搅拌混合,在搅拌过程中用氨水控制混合溶液pH值为5.5～8.5得到混合物；3)将所述混合物在100℃～200℃下水热反应,得到磷酸铁锂前驱体；4)将所述磷酸铁锂前驱体在温度650℃～800℃下进行碳包覆反应得到修复后的磷酸铁锂电池材料。该方法实现了将废旧磷酸铁锂电池正极材料直接进行修复。(The invention relates to a method for repairing a waste lithium iron phosphate material, which comprises the following steps: 1) measuring the content of Li, Fe and P elements in the waste lithium iron phosphate material; 2) preparing a mixed solution containing lithium salt, ferric salt and phosphoric acid, adding the waste lithium iron phosphate material into the mixed solution according to the final stoichiometric ratio of Li to Fe to P of 0.75-1.25 to 1, stirring and mixing, and controlling the pH value of the mixed solution to be 5.5-8.5 by using ammonia water in the stirring process to obtain a mixture; 3) carrying out hydrothermal reaction on the mixture at 100-200 ℃ to obtain a lithium iron phosphate precursor; 4) and carrying out carbon coating reaction on the lithium iron phosphate precursor at the temperature of 650-800 ℃ to obtain the repaired lithium iron phosphate battery material. The method realizes the direct repair of the anode material of the waste lithium iron phosphate battery.)

1. The method for repairing the waste lithium iron phosphate material is characterized by comprising the following steps of:

1) measuring the content of Li, Fe and P elements in the waste lithium iron phosphate material;

2) preparing a mixed solution containing lithium salt, ferric salt and phosphoric acid, adding the waste lithium iron phosphate material into the mixed solution according to the final stoichiometric ratio of Li to Fe to P of 0.75-1.25 to 1, stirring and mixing, and controlling the pH value of the mixed solution to be 5.5-8.5 by using ammonia water in the stirring process to obtain a mixture;

3) carrying out hydrothermal reaction on the mixture at 100-200 ℃ to obtain a lithium iron phosphate precursor;

4) and carrying out carbon coating reaction on the lithium iron phosphate precursor at the temperature of 650-800 ℃ to obtain the repaired lithium iron phosphate battery material.

2. The repairing method according to claim 1, wherein in the step 2), the waste lithium iron phosphate material is added into the mixed solution according to a solid-to-liquid ratio of 50-150 g/L.

3. The repairing method according to claim 1, wherein in the step 3), the mixture is hydrothermally reacted at 100 to 200 ℃ for 2 to 10 hours.

4. Repair method according to claim 3, characterized in that in step 3) the mixture is placed in an autoclave and N is passed through₂Controlling the air pressure to be 0.05-0.2MPa, and carrying out hydrothermal reaction for 2-10 hours at the temperature of 100-200 ℃.

5. The repair method according to claim 1, wherein in step 4), the carbon-coating reaction is performed on the lithium iron phosphate precursor at a temperature of 650 ℃ to 800 ℃ for 4 hours to 8 hours.

6. Repair method according to claim 1, characterized in that, in step 4), theCalcining the lithium iron phosphate precursor in a tubular furnace by using N₂The carbon coating reaction is carried out at the temperature of 650-800 ℃ in protective atmosphere.

7. The repair method according to claim 1, wherein in step 2), the lithium salt is selected from one or more of lithium hydroxide, lithium chloride and lithium sulfate.

8. The repair method according to claim 1, wherein, in the step 2), the iron salt is selected from one or two of ferrous sulfate and ferrous chloride.

9. The repair method according to claim 1, wherein in step 1), the waste lithium iron phosphate material is obtained by: the method comprises the steps of discharging waste lithium iron phosphate batteries, disassembling and separating out positive plates, crushing and separating the positive plates to obtain positive materials and aluminum foils, and further performing gravity screening and impurity removal to obtain the waste lithium iron phosphate materials.

Technical Field

The invention relates to the field of waste lithium ion battery recovery, hydrometallurgy and resource circulation, in particular to a method for repairing a waste lithium iron phosphate material.

Background

At present, the service life of the lithium iron phosphate battery is about 5 years, and with the use of a large amount of lithium iron phosphate power electric automobiles, the amount of waste lithium iron phosphate batteries is gradually increased, and the amount of waste lithium iron phosphate reaches 12-17 ten thousand tons by estimation in this year. The lithium-ion power battery contains a large amount of lithium elements, and the lithium elements are used as main raw materials for producing the lithium-ion power battery, so that the lithium elements are recycled and are very important for the development of lithium-ion power automobiles. Meanwhile, the waste lithium iron phosphate batteries contain a large amount of electrolyte, organic wastes and other pollutants, and are not treated and are discarded at will, so that serious environmental problems are caused, and therefore, the recycling of the waste lithium iron phosphate batteries has important economic and environmental protection significance.

The recovery industry of waste power lithium ion batteries mainly adopts a wet method to recover valuable metals in positive electrode materials, inorganic acid is adopted to dissolve the valuable metals, and metal compounds are obtained by extraction and separation and are sold as products, for example, Chinese patents CN201810592130.7 and CN201910711370.9 disclose a method for recovering valuable metal elements such as lithium in lithium iron phosphate by a leaching process, but the subsequent treatment of a large amount of acid and alkali consumption and environmental pollutants in the process is very complicated.

The method is characterized in that the waste lithium iron phosphate anode material reacts with supplementary raw materials to repair damaged lattices and form regular olivine lithium iron phosphate crystals again, for example, Chinese patents CN201010253859.5 and CN201610623808.4 enable related elements to exist in an ion form through acid leaching, and then the lithium iron phosphate materials are prepared again through processes of ball milling, calcining and the like.

Disclosure of Invention

Based on the technical background, the invention uses a hydrothermal method as a regeneration process method, solves the technical problem of directly repairing the anode material of the waste lithium iron phosphate battery, and obtains a new lithium iron phosphate material through high-temperature calcination, thereby realizing the cyclic utilization of valuable metals and carbon, avoiding leaching, being green and environment-friendly, improving the recovery efficiency and saving the production cost.

In order to solve the technical problems, the invention provides a method for repairing a waste lithium iron phosphate material.

The invention provides a method for repairing a waste lithium iron phosphate material, which comprises the following steps:

1) measuring the content of Li, Fe and P elements in the waste lithium iron phosphate material;

2) preparing a mixed solution containing lithium salt, ferric salt and phosphoric acid, adding the waste lithium iron phosphate material into the mixed solution according to the final stoichiometric ratio of Li to Fe to P of 0.75-1.25 to 1, stirring and mixing, and controlling the pH value of the mixed solution to be 5.5-8.5 by using ammonia water in the stirring process to obtain a mixture;

3) carrying out hydrothermal reaction on the mixture at 100-200 ℃ to obtain a lithium iron phosphate precursor;

4) and carrying out carbon coating reaction on the lithium iron phosphate precursor at the temperature of 650-800 ℃ to obtain the repaired lithium iron phosphate battery material.

Preferably, in the step 2), the waste lithium iron phosphate material is added into the mixed solution according to a solid-to-liquid ratio of 50-150 g/L.

Preferably, in step 3), the mixture is subjected to a hydrothermal reaction at 100 to 200 ℃ for 2 to 10 hours.

Preferably, in step 3), the mixture is placed in an autoclave and N is passed through₂The air pressure was controlled to be 0.05 to 0.2MPa, and carrying out hydrothermal reaction at the temperature of between 100 and 200 ℃ for 2 to 10 hours.

Preferably, in the step 4), the carbon-coated reaction of the lithium iron phosphate precursor is performed at a temperature of 650 to 800 ℃ for 4 to 8 hours.

Preferably, in the step 4), the lithium iron phosphate precursor is calcined in a tube furnace by using N₂The carbon coating reaction is carried out at the temperature of 650-800 ℃ in protective atmosphere.

Preferably, in step 2), the lithium salt is selected from one or more of lithium hydroxide, lithium chloride and lithium sulfate.

Preferably, in step 2), the iron salt is selected from one or both of ferrous sulfate and ferrous chloride.

Preferably, in step 1), the waste lithium iron phosphate material is obtained through the following steps: the method comprises the steps of discharging waste lithium iron phosphate batteries, disassembling and separating out positive plates, crushing and separating the positive plates to obtain positive materials and aluminum foils, and further performing gravity screening and impurity removal to obtain the waste lithium iron phosphate materials.

Compared with the prior art, the invention has the advantages that: measuring the content of Li, Fe and P elements in the waste lithium iron phosphate material to obtain the content of three elements in the waste lithium iron phosphate material, then preparing a mixed solution containing lithium salt, iron salt and phosphoric acid according to the stoichiometric ratio of Li to Fe to P of 0.75-1.25: 1:1, adding the waste lithium iron phosphate material into the mixed solution to supplement corresponding reaction raw materials for repairing the lithium iron phosphate battery material, stirring and mixing, fully contacting the reaction raw materials with the lithium iron phosphate battery material to be repaired, controlling the pH value to be 5.5-8.5 by using ammonia water in the stirring process to obtain a mixture, adjusting the pH value to 5.5-8.5 by using the ammonia water to meet the requirement of precipitation, simultaneously decomposing the ammonia water at high temperature to reduce the introduction of impurities, and then carrying out hydrothermal reaction on the mixture at 100-200 ℃, wherein the hydrothermal condition and appropriate pH control ensure that crystal grains are completely developed, small in particle size, uniformly distributed and lighter in agglomerated particles, the method has the advantages that the defects of grain growth, defect formation, impurity introduction and the like caused in the calcining process of the traditional repairing process are avoided, carbon is facilitated to fall off from damaged lithium iron phosphate crystals into a lithium iron phosphate precursor, the hydrothermal reaction in the prior art is generally used for realizing the synthesis of the lithium iron phosphate material, the hydrothermal reaction has the effects of repairing the waste lithium iron phosphate material, the carbon in the waste lithium iron phosphate material falls off into the precursor, the carbon is conveniently coated on the repaired lithium iron phosphate material, then the carbon coating reaction is carried out on the lithium iron phosphate precursor at the temperature of 650-800 ℃, the fallen carbon is coated on the surface of the lithium iron phosphate material, and the repaired lithium iron phosphate material is obtained, so that the waste lithium iron phosphate material is directly repaired. The method has the advantages of mild process conditions, simple preparation process, low cost, no need of leaching, no generation of a large amount of waste and environmental protection, and can effectively realize the recycling of valuable metals and carbon in the anode material.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a process flow diagram of the method of the present invention.

Fig. 2 is an XRD pattern of the waste lithium iron phosphate as it is, the lithium iron phosphate precursor prepared by the present invention at 150 ℃, and the lithium iron phosphate material prepared by the final calcination of the present invention in example 1 of the present invention.

Fig. 3 is an SEM image of the waste lithium iron phosphate material, which is subjected to separation and impurity removal in example 2 of the present invention, magnified 2000 times.

Fig. 4 is an SEM image of the waste lithium iron phosphate material subjected to separation and impurity removal according to example 2 of the present invention, which is enlarged by 5000 times.

Fig. 5 is an SEM image of the waste lithium iron phosphate material subjected to separation and impurity removal according to embodiment 2 of the present invention, which is magnified 10000 times.

Fig. 6 is an SEM image of an enlarged 2000 of the lithium iron phosphate precursor prepared by a hydrothermal method in example 2 of the present invention.

Fig. 7 is an SEM image of a lithium iron phosphate precursor prepared by a hydrothermal method according to example 2 of the present invention at an enlargement of 5000 a.

Fig. 8 is an SEM image of a lithium iron phosphate precursor prepared by a hydrothermal method in example 2 of the present invention at an enlargement of 10000.

Detailed Description

With reference to fig. 1, the present embodiment provides a method for repairing a waste lithium iron phosphate material, including the following steps:

1) after the waste lithium iron phosphate battery is subjected to discharge treatment, the metal shell is disassembled and removed, and the positive plate, the negative plate, the diaphragm and the electrolyte are separated. Crushing and separating the obtained positive plate to obtain a positive material and an aluminum foil, further performing gravity screening to obtain the waste lithium iron phosphate material, physically removing impurities to ensure that the total impurity element content is lower than 0.5%, and determining the content of elements such as Li, Fe, P and the like in the waste lithium iron phosphate material; aluminum and copper existing in a metal form can be removed through a reselection mode, the total impurity element content in the obtained waste lithium iron phosphate material is lower than 0.5%, and the impurity content in the material is lower than the specified impurity content of industrial-grade lithium iron phosphate. The total content of impurity elements in the waste lithium iron phosphate material is lower than 0.5%, the amount of impurities can be almost ignored, and the low-content impurities cannot influence the follow-up repair of the waste lithium iron phosphate material.

2) Preparing a mixed solution containing lithium salt, ferric salt and phosphoric acid, adding the waste lithium iron phosphate material into the mixed solution according to a final stoichiometric ratio of Li to Fe to P of 0.75-1.25 to 1 and a solid-to-liquid ratio of 50-150 g/L, stirring and mixing, and controlling the pH value of the mixed solution to be 5.5-8.5 by using ammonia water in the stirring process to obtain a mixture; the lithium salt is selected from one or more of lithium hydroxide, lithium chloride and lithium sulfate; the iron salt is selected from one or two of ferrous sulfate and ferrous chloride;

3) the mixture was placed in an autoclave and N was passed through₂Controlling the air pressure to be 0.05-0.2MPa, carrying out hydrothermal reaction at 100-200 ℃ for 2-10 hours while stirring at the stirring speed of 600 rpm, filtering, and drying at 100-120 ℃ for 3-5 hours to obtain a lithium iron phosphate precursor;

4) putting the lithium iron phosphate precursor into a tube furnace for calcination, and adding N₂The carbon coating reaction is carried out for 4 to 8 hours at the temperature of 650 to 800 ℃ in the protective atmosphere to obtain the repaired lithium iron phosphate battery material.

To further illustrate the methods set forth in the practice of the present invention, the methods of the present invention are illustrated by the following detailed examples.