CN116177511A

CN116177511A - A method for rebuilding defective iron phosphate

Info

Publication number: CN116177511A
Application number: CN202310036247.8A
Authority: CN
Inventors: 冯克敏; 彭海南; 何兵兵; 吴松; 盛国臣; 谭义凤; 张明松; 余欣鑫
Original assignee: Guizhou Phosphate New Energy Technology Co ltd
Current assignee: Guizhou Phosphate New Energy Technology Co ltd
Priority date: 2023-01-10
Filing date: 2023-01-10
Publication date: 2023-05-30
Anticipated expiration: 2043-01-10
Also published as: CN116177511B

Abstract

The invention discloses a method for remanufacturing an iron phosphate defective product. The method comprises the following steps of (1) dissolving the iron phosphate defective product: and adding a certain amount of sulfuric acid into the iron phosphate defective product solution to enable the iron phosphate to reach critical granularity. (2) ferric phosphate reaction crystallization and aging crystal transformation: ammonia water and a surfactant are added in the reaction process, the dropping rate, the reaction temperature and the stirring rate of the ammonia water are controlled, and meanwhile, the pH value of a phosphoric acid regulating system is supplemented in the aging process to promote the progress of the crystal transformation process and the release of impurities. (3) washing the crude product and washing after aging: the soluble salts and the part of the free acid after the crystal transformation are removed. (4) drying and calcining: free water and crystal water in the product are removed. The invention solves the problem of disposal of the iron phosphate defective products caused by adjustment of equipment and process parameters, improves the proportion table and reduces the content of sulfur and other impurities.

Description

Method for remanufacturing iron phosphate defective products

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a method for manufacturing iron phosphate defective products.

Background

With the continuous and deep development of new energy industry, the power battery industry as new energy and environmental protection low carbon is rapidly developed. And lithium ion batteries are the main stream development direction of many power batteries by virtue of their excellent performance and moderate manufacturing cost. The lithium iron phosphate material has the advantages of stable charging and discharging platform, good safety, less self-discharge, low cost and no pollution to the environment. Is the future development direction of the positive electrode material of the high-energy lithium battery super-capacity power supply, wind energy and solar energy storage equipment of the prior ideal hybrid power and electric automobile. At present, the market demand of the Chinese lithium iron phosphate anode material presents a spiral rising trend. Iron phosphate is used as an important precursor for synthesizing lithium iron phosphate, and the related quality and performance index of the iron phosphate have important influence on a lithium iron phosphate battery. Each ton of battery grade lithium iron phosphate produced theoretically consumes 0.92 ton of anhydrous iron phosphate, corresponding to a demand of 90% of lithium iron phosphate. As the application of lithium iron phosphate batteries in the fields of energy storage, 5G base stations and the like is rapidly expanding, the demand of lithium iron phosphate is also expanding, and thus, the demand of iron phosphate as a raw material is also increasing.

Currently, the preparation process of ferric phosphate includes a solid-phase synthesis method, a hydrothermal method, a sol-gel method, a template method, an ultrasonic chemical method, a homogeneous precipitation method, an ion exchange lithium removal method, an air oxidation method and the like. The domestic method for preparing the ferric phosphate is mainly a coprecipitation method, ferrous sulfate is used as a raw material, and the product is crystallized and prepared by adjusting the pH value of the solution. Under the existing production process, the indexes of sulfate radical and other impurities in the ferric phosphate are increasingly strict along with the upgrading and reconstruction of downstream products, and the index control is a difficult problem in the production of the ferric phosphate all the time. The conventional washing and the use of additives can achieve a certain effect, but partial impurities which are entrained in the iron phosphate internal package cannot be completely removed. In the production process, the iron phosphate defective product is formed due to unstable control of parameters and unstable product indexes caused by abnormal equipment. The iron phosphate defective products of the part cannot remove impurities through the existing washing and calcining, and the re-calcining under the high temperature condition has a certain influence on the morphology and the specific surface of the product. The invention re-dissolves and re-crystallizes the iron phosphate defective products, obtains the iron phosphate of the superior products by means of secondary combination of crystal structures, morphology control and the like, and has important significance for the stock removal and the valued application of the iron phosphate defective products.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides a method for remanufacturing the iron phosphate defective product.

The preparation method for realizing the remanufacturing of the iron phosphate defective product comprises the following steps:

(1) And adding the iron phosphate defective products, sulfuric acid and desalted water into a reactor according to a certain proportion, and stirring and dissolving to obtain iron phosphate defective product dissolved slurry.

(2) And adding alkali liquor and a surfactant into the dissolved slurry, adjusting the pH value, and stirring for reaction to obtain the ferric phosphate dihydrate slurry.

(3) And (3) carrying out solid-liquid separation on the ferric phosphate dihydrate slurry obtained in the steps, and washing the solid phase supplementing washing liquid twice.

(4) Adding phosphoric acid solution and desalted water into the washed ferric phosphate dihydrate slurry, adjusting pH, heating, stirring for ageing, and filtering to obtain the aged ferric phosphate dihydrate.

(5) And (3) carrying out solid-liquid separation on the aged ferric phosphate dihydrate slurry obtained in the steps, and washing the solid phase supplementing washing liquid twice.

(6) And (3) carrying out solid-liquid separation on the washed ferric phosphate dihydrate obtained in the steps, taking a solid phase for drying and crushing, and then calcining to obtain a reconstituted ferric phosphate product.

In the step (1), the addition amount of the iron phosphate defective products and desalted water is 1:2-2.5, and the addition amount of sulfuric acid is 20-50% of the theoretical use amount, preferably 20-30%.

In the step (2), the alkali liquor is 8% ammonia water, the surfactant is citric acid, and the addition amount is 0.03% -0.1% of the mass of the dissolved slurry, preferably 0.05% -0.1%. The pH after the reaction is 1.7 to 2.0, preferably 1.70 to 1.85. The reaction temperature is controlled to be 50-70 ℃, and the reaction rotating speed is controlled to be 500-700rpm.

In the step (3) and the step (5), the washing liquid is desalted water with the temperature of 50-70 ℃, and the volume of desalted water is kept consistent with that of the filtered filtrate.

In the step (4), phosphoric acid is added to a concentration of 70%, and the pH is adjusted to 1.7-1.9, preferably 1.8-1.85. The aging temperature is 80-95 ℃, preferably 93-95 ℃. The aging rotating speed is 500-700rpm, and the constant temperature stirring is carried out for 30-60 min after the aging and whitening.

In the step (6), the drying temperature is 150-170 ℃ and the drying time is 1.5-2.5 h. The calcination temperature is 600-700 ℃, the calcination time is 2-3 h, preferably 650-680 ℃, and the calcination time is 2-2.5 h.

The most critical concept of the invention is as follows: the invention achieves the critical granularity by skillfully utilizing the ferric phosphate dissolved in sulfuric acid. The iron phosphate at this critical particle size has good crystal surface energy and formation energy, resulting in the formation of stable nuclei of iron phosphate. The residual small crystal nucleus with irregular shape or defect in supersaturated solution is completely dissolved to reach critical granularity range. The morphology structure of the product iron phosphate is destroyed, the iron phosphate solution is precipitated by controlling the pH value in the solution to achieve a recombined state, and then the phenomenon of agglomeration of iron phosphate particles is reduced and the morphology of the product is regulated and controlled by controlling the stirring rate and the addition of a surfactant, and the particle size of the iron phosphate particles is regulated, so that the reacted iron phosphate reaches a high-grade at a microscopic level. Meanwhile, the content of sulfate radical and impurities carried among particles can be reduced, and the problem of agglomeration and encapsulation is fundamentally solved. In the subsequent steps, the residual sulfate radical and other soluble salt impurities in the sulfate radical mother liquor are removed through a secondary washing process after the reaction, so that the contents of impurities and sulfur indexes in the product are reduced. In addition, the phosphoric acid is supplemented in the aging process, so that an ion channel can be slightly dissolved out of the surface of the ferric phosphate, and release of metal impurities and sulfur is facilitated. The secondary washing process after ageing is used for removing impurities released in the ageing process and washing away the phosphoric acid supplemented in the ageing process, so that the iron and phosphorus index of the product is maintained normal and the purity in the product is up to the grade of a superior product.

The method for manufacturing the iron phosphate defective products has at least the following beneficial effects:

1. according to the invention, the iron phosphate defective products are innovatively dissolved in sulfuric acid, the formed iron phosphate structure and morphology are broken, part of iron phosphate is returned to a solution ion state, the pH value and stirring speed in the reaction process are controlled, the granularity of ferric phosphate dihydrate is reduced, the crystallization agglomeration phenomenon in the reaction process is reduced, the sulfate radicals wrapped in the iron phosphate defective products can be better dissolved in water, and the sulfur content in the product reaches the level of superior products with other impurity indexes in a multistage washing mode.

2. The invention supplements a small amount of phosphoric acid in the aging process, slightly dissolves an ion channel on the surface of the ferric phosphate, is more beneficial to release of metal impurities and sulfur, and is used for removing the impurities released in the aging process and washing the phosphoric acid supplemented in the aging process in the secondary washing process after the aging, so that the iron-phosphorus index of the product is maintained normal and the purity in the product is also enabled to reach the grade of superior products.

3. The invention has simple process flow and stable control, recycles the cheap iron phosphate inferior products and the waste iron phosphate, creates a larger economic benefit effect, and solves the problems of stock pressure and environmental protection of a storehouse.

Description of the drawings

The invention is further described with reference to the accompanying drawings and examples, in which:

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

Detailed Description

For a detailed description of the technical content of the present invention and a full understanding of the objects and effects of the present invention, the following description will be made with reference to the embodiments and drawings.

Example 1

Referring to a process flow chart of fig. 1, the method for remanufacturing the iron phosphate defective product comprises the following specific steps:

(1) Dissolution of iron phosphate rejects

Mixing the iron phosphate defective product with desalted water according to the proportion of 1:2.1, fully stirring and mixing, wherein the adding amount of sulfuric acid is 20% of the theoretical using amount, and stirring for 15min to obtain the ferric phosphate defective product dissolved slurry.

(2) Synthesis reaction and reaction washing

Firstly, raising the temperature of the iron phosphate defective product dissolved slurry to 50 ℃, then slowly adding 5% ammonia water solution into the iron phosphate defective product dissolved slurry, simultaneously adding a surfactant with the mass of 0.03% of the dissolved slurry, strictly controlling the ammonia water feeding speed, adjusting the pH value to 1.76, and keeping the rotating speed of 500rpm for fully stirring to enable the solution to react, thus obtaining the reclaimed ferric phosphate dihydrate slurry. And filtering the reaction slurry to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 50℃and the volume of desalted water was kept the same as that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 50 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And obtaining a ferric phosphate filter cake after reaction and washing.

(3) Aging and aging washing

Dispersing the iron phosphate filter cake after reaction washing into desalted water at 85 ℃, adding 69% phosphoric acid solution, adjusting the pH to 1.72, heating the reaction temperature to keep the temperature at 85 ℃ unchanged and keeping the rotating speed at 500rpm, and continuously stirring for 30min and then performing filter pressing treatment when the iron phosphate slurry turns into pure white to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 50℃and the volume of desalted water was kept the same as that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 50 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And (5) obtaining an aged and washed ferric phosphate filter cake.

(4) Drying and calcining

And (3) placing the aged and washed ferric phosphate filter cake in a vacuum drying oven for drying at the drying temperature of 150 ℃ for 1.5h, taking out the dried ferric phosphate for crushing after the drying is finished, and placing the crushed ferric phosphate in a calcination square boat for moving to a muffle furnace after the crushing is finished, wherein the calcination temperature is 620 ℃ and the calcination time is 3h. And (5) carrying out jet milling after calcination and cooling to obtain the rebuilt superior ferric phosphate.

Example 2

(1) Dissolution of iron phosphate rejects

Mixing the iron phosphate defective product with desalted water according to the proportion of 1: and 2.5, fully stirring and mixing, wherein the adding amount of sulfuric acid is 25% of the theoretical using amount, and stirring for 15min to obtain the ferric phosphate defective product dissolved slurry.

(2) Synthesis reaction and reaction washing

Firstly, raising the temperature of the iron phosphate defective product dissolved slurry to 60 ℃, then slowly adding 8% ammonia water solution into the iron phosphate defective product dissolved slurry, simultaneously adding a surfactant with the mass of 0.06% of the dissolved slurry, strictly controlling the ammonia water feeding speed, adjusting the pH value to 1.93, and keeping the rotating speed of 600rpm for fully stirring to enable the solution to react, thus obtaining the reclaimed ferric phosphate dihydrate slurry. And filtering the reaction slurry to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 60℃to keep the volume of desalted water consistent with that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 60 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And obtaining a ferric phosphate filter cake after reaction and washing.

(3) Aging and aging washing

Dispersing the iron phosphate filter cake after reaction washing into desalted water at 95 ℃, adding 69% phosphoric acid solution, adjusting the pH to 1.87, heating the reaction temperature to keep the temperature unchanged at 95 ℃, keeping the rotating speed at 600rpm, and continuously stirring for 1h and performing filter pressing treatment when the iron phosphate slurry turns into pure white to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 60℃to keep the volume of desalted water consistent with that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 60 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And (5) obtaining an aged and washed ferric phosphate filter cake.

(4) Drying and calcining

And (3) placing the aged and washed ferric phosphate filter cake in a vacuum drying oven for drying at the drying temperature of 160 ℃ for 2 hours, taking out the dried ferric phosphate for crushing after the drying is finished, and placing the crushed ferric phosphate in a calcination ark for transferring to a muffle furnace after the crushing is finished, wherein the calcination temperature is 700 ℃ and the calcination time is 2 hours. Calcining, cooling and crushing to obtain the rebuilt superior ferric phosphate.

Example 3

(1) Dissolution of iron phosphate rejects

Mixing the iron phosphate defective product with desalted water according to the proportion of 1:2.3, fully stirring and mixing, wherein the adding amount of sulfuric acid is 40% of the theoretical using amount, and stirring for 15min to obtain the ferric phosphate defective product dissolved slurry.

(2) Synthesis reaction and reaction washing

Firstly, raising the temperature of the iron phosphate defective product dissolved slurry to 70 ℃, then slowly adding 7% ammonia water solution into the iron phosphate defective product dissolved slurry, simultaneously adding a surfactant with the mass of 0.1% of the dissolved slurry, strictly controlling the ammonia water feeding speed, adjusting the pH value to 2.0, and keeping the rotating speed of 700rpm for fully stirring to enable the solution to react, thus obtaining the reclaimed ferric phosphate dihydrate slurry. And filtering the reaction slurry to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 70℃and the volume of desalted water was kept the same as that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 70 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And obtaining a ferric phosphate filter cake after reaction and washing.

(3) Aging and aging washing

Dispersing the iron phosphate filter cake after reaction washing into desalted water at 80 ℃, adding 69% phosphoric acid solution, adjusting the pH to 1.75, heating the reaction temperature to keep the temperature at 80 ℃ unchanged and keeping the rotating speed at 700rpm, and continuously stirring for 45min and then performing filter pressing treatment when the iron phosphate slurry turns into pure white to obtain a first filter cake and a first filtrate. Then, the first filter cake was dispersed in desalted water at 70℃and the volume of desalted water was kept the same as that of the first filtrate, and the mixture was stirred for 15 minutes and then filtered. And obtaining a second filter cake and a second filtrate, dispersing the second filter cake into desalted water at 70 ℃, keeping the volume of desalted water consistent with that of the second filtrate, stirring for 15min, and filtering. And (5) obtaining an aged and washed ferric phosphate filter cake.

(4) Drying and calcining

And (3) placing the aged and washed ferric phosphate filter cake in a vacuum drying oven for drying at the drying temperature of 170 ℃ for 2.5 hours, taking out the dried ferric phosphate for crushing after the drying is finished, and placing the crushed ferric phosphate in a calcination square boat for transferring to a muffle furnace after the crushing is finished, wherein the calcination temperature is 650 ℃ and the calcination time is 2.5 hours. Calcining, cooling and crushing to obtain the rebuilt superior ferric phosphate.

Through detection, various indexes of the obtained regenerated ferric phosphate product can far meet the standard requirements of 'HG/T4701-2021 ferric phosphate for batteries', and various performance indexes are shown in Table 1.

TABLE 1 iron phosphate Performance index

Claims

1. A method for rebuilding defective ferric phosphate, characterized in that, comprising the following steps:

(1) Add the defective ferric phosphate, sulfuric acid, and desalted water into the reactor in a certain proportion, stir and dissolve, and obtain the dissolved slurry of the defective ferric phosphate;

(2) Add lye and surfactant to the dissolving slurry, adjust pH, stir and react to obtain ferric phosphate dihydrate slurry;

(3) Separating the solid-liquid ferric phosphate dihydrate slurry obtained in the above steps, and washing the solid-phase supplementary washing liquid twice;

(4) adding phosphoric acid solution and desalted water to the washed ferric phosphate dihydrate slurry, adjusting pH, heating and stirring for aging, and filtering to obtain aged ferric phosphate dihydrate;

(5) Separating the solid-liquid of the aged ferric phosphate dihydrate slurry obtained in the above steps, and washing the solid-phase supplementary washing solution twice;

(6) Separating the washed ferric phosphate dihydrate obtained in the above steps from solid to liquid, taking the solid phase for drying and crushing, and then calcining to obtain a reconstituted ferric phosphate product.

2. The method for remanufacturing defective iron phosphate products according to claim 1, characterized in that: the defective iron phosphate products mainly have problems of excessive sulfur content and low specific surface area, S≥400ppm, and specific surface area≤4m ² / g.

3. The method for remanufacturing defective iron phosphate products according to claim 1, characterized in that, in step (1), the addition amount of the defective iron phosphate product and desalted water is 1:2-2.5, and the addition amount of sulfuric acid 20% to 50% of the theoretical dosage.

4. The method for remanufacturing defective ferric phosphate according to claim 1, characterized in that in step (2), the lye is ammonia water with a concentration of 5% to 8%, and the surfactant is citric acid, adding The amount is 0.03%-0.1% of the mass of the dissolved slurry, the pH after the reaction is 1.7-2.0, the reaction temperature is controlled at 50°C-70°C, and the reaction speed is controlled at 500-700rpm.

5. The method for remanufacturing defective iron phosphate products according to claim 1, characterized in that, in step (3) and step (5), the washing liquid is desalted water at 50°C to 70°C, and the volume of desalted water is Keep the same volume as the filtrate after filtration.

6. The method for remanufacturing defective iron phosphate products according to claim 1, characterized in that in step (4), the concentration of phosphoric acid added is 70%, the adjusted pH is 1.7-1.9, and the aging temperature is 80 ~95°C, the aging speed is 500~700rpm, after aging and turning white, stir at constant temperature for 30~60min.

7. The method for remanufacturing defective iron phosphate according to claim 1, characterized in that in step (6), the drying temperature is 150-170°C, the drying time is 1.5-2.5h, and the calcination temperature is 600°C ~700°C, the calcination time is 2~3h.