阅读说明：本技术 提升废旧锂离子电池再生的正极活性材料电学性能的方法 (Method for improving electrical property of positive active material regenerated from waste lithium ion battery ) 是由 杨声海 介亚菲 张刚 赖延清 缪永华 黄勇 陈佳杰 张凯 田忠良 薛驰 陈永明 于 2018-06-26 设计创作，主要内容包括：本发明属于废旧电池材料回收技术领域,提升废旧锂离子电池再生的正极活性材料电学性能的方法,从废旧锂离子电池中获得需要回收的废旧正极活性材料,对废旧正极活性材料进行除氟处理,用于提升再生的正极活性材料的电学性能。本发明通过对废旧正极活性材料进行所述的熟化除氟过程,可以明显改善回收得到的正极活性材料的电学性能；例如,明显提升放电容量,对其循环性能也有所改善。(The invention belongs to the technical field of waste battery material recovery, and discloses a method for improving the electrical property of a regenerated positive electrode active material of a waste lithium ion battery. According to the invention, the electrical properties of the recycled positive active material can be obviously improved by carrying out the curing defluorination process on the waste positive active material; for example, the discharge capacity is obviously improved, and the cycle performance is also improved.)

1. A method for improving the electrical property of a positive active material regenerated by a waste lithium ion battery is characterized in that the waste positive active material needing to be recovered is obtained from the waste lithium ion battery; placing the waste positive electrode active material in acid liquor, and carrying out curing defluorination treatment under the condition of negative pressure or under the condition of continuous air flow blowing; and (2) leaching the solution subjected to the curing defluorination treatment with water to obtain an acid leaching solution, sequentially carrying out copper removal, aluminum removal, P, Fe and Li molar ratio regulation and control to be (1.0-1.1): 1, and coprecipitation treatment on the acid leaching solution to obtain the regenerated positive electrode active material.

2. The method of claim 1, wherein the waste positive active material is subjected to a ripening defluorination process for increasing the discharge capacity of the regenerated positive active material.

3. The method of claim 1, wherein the acid solution is a strong inorganic acid solution; the acid solution is at least one of hydrochloric acid, sulfuric acid and phosphoric acid;

the acid liquor is at least one of concentrated hydrochloric acid, concentrated sulfuric acid and concentrated phosphoric acid; h of the acid liquor⁺The concentration is not lower than 12 mol/L.

4. The method of claim 1, wherein the temperature of the curing process is 100 to 255 ℃; the time is 0.5h to 5.0 h.

5. The method of claim 1, wherein the degree of vacuum during the aging process is not greater than 0.09 MPa; and in the continuous air flow purging process, the flow rate of the air flow is not lower than 500 ml/min.

6. The method of claim 1, wherein the fluorine content of the regenerated positive electrode active material is controlled to be not higher than 20 ppm.

7. The method according to any one of claims 1 to 6, wherein the waste lithium ion battery is a waste lithium iron phosphate battery.

8. The method of claim 1, wherein in the water leaching process, the volume of water and the mass ratio of the positive electrode active material are 3: 1 mL/g-10: 1mL/g, the water leaching temperature is normal temperature-95 ℃, and the water leaching time is 0.5 h-5.0 h;

the copper removal process comprises the steps of adding iron powder into the acid leaching solution, and carrying out copper removal treatment to obtain a copper removal leaching solution; wherein the adding amount of the iron powder is 1.0-1.5 times of the theoretical molar weight, the copper removal reaction temperature is normal temperature-95 ℃, and the copper removal reaction time is 0.25-2.0 h;

carrying out extraction and dealumination treatment on the copper-removed leaching solution to obtain an dealumination leaching solution;

in the process of extracting and removing aluminum, the extracting agent is P204 (di (2-ethylhexyl) phosphate) -sulfonated kerosene mixed liquor, wherein the concentration of P204 is 0.6-1.5 mol/L; the initial pH value of the water phase is 1.5-3.0 in the extraction process compared with 1: 1-1/5;

adjusting the molar ratio of Li to Fe to P of the aluminum-removing leaching solution to be (1.0-1.1) to 1.

9. The method of claim 1, wherein the co-precipitation comprises adding ascorbic acid to the solution with the molar ratio of Li: Fe: P adjusted, stirring at 50-100 ℃ for 1.0-3.0 h, controlling the pH to 7-11, and filtering to obtain the regenerated positive electrode active material.

Technical Field

The invention belongs to the field of waste battery recovery, and particularly relates to a method for recovering and regenerating a positive active material from a waste lithium ion battery with high electrical performance.

Background

Because of the advantages of good safety performance, long cycle life, low material cost and the like of the lithium iron phosphate battery, the lithium iron phosphate battery is considered to be an ideal battery for electric vehicles at present and is widely applied to the automobile industry. However, with the rapid growth of the electric automobile industry, according to the forecast of the research center of automobile technology in China, the accumulated scrappage of electric automobile power batteries in China will reach 32.2 million tons (most of the electric automobile power batteries are lithium iron phosphate power batteries) in 2020. If the waste batteries can not be effectively recycled, severe ecological pollution and resource waste are faced immediately. Therefore, in order to recycle materials and save cost, it becomes necessary to recycle lithium iron phosphate materials in waste lithium iron phosphate power batteries.

Driven by economic benefits, the currently reported waste lithium iron phosphate batteries mainly recover lithium elements, and lithium carbonate, lithium phosphate or lithium dihydrogen phosphate is obtained by a precipitation method, and some reports also recover phosphorus and iron elements by obtaining iron phosphate precipitates. In the prior art, defluorination, purification and copper and aluminum impurity removal are not considered in the recovery of lithium iron phosphate, and LiF and copper aluminum elements can enter a synthesized lithium iron phosphate crude product through coprecipitation, so that the electrochemical performance of the lithium iron phosphate anode material is influenced finally.

Disclosure of Invention

In order to solve the technical problem that the performance of the regenerated anode active material of the existing waste lithium ion battery is not ideal, the invention provides a method for improving the electrical performance of the regenerated anode active material of the waste lithium ion battery, and the electrical performance of the regenerated anode active material (or the recycled anode active material) can be unexpectedly improved by innovatively carrying out curing defluorination treatment (the invention is also called curing for short) on the waste anode active material.

A method for improving the electrical property of a regenerated anode active material of a waste lithium ion battery comprises the steps of obtaining the waste anode active material needing to be recovered from the waste lithium ion battery; the waste positive active material is placed in acid liquor, and curing defluorination treatment is carried out under the negative pressure condition or under the continuous air flow purging condition, so as to improve the electrical property of the regenerated positive active material.

The inventor creatively discovers through a great deal of research that one main factor restricting the performance of the positive active material obtained by recycling the waste battery is residual fluorine raw material in the waste positive active material, and the performance of the recycled positive active material can be obviously improved by carrying out the innovative curing defluorination treatment on the recovery process of the positive active material.

In the invention, the waste positive active material can be obtained from the waste lithium ion battery by adopting the conventional method. For example, the waste lithium ion battery is subjected to short-circuit discharge and disassembly to obtain a material containing the positive plate, and then the material is crushed, oxidized, roasted, binder removed and screened to obtain the waste positive active material.

The inventor finds that the electrical performance of the regenerated positive electrode active material can be improved by performing curing defluorination treatment on the waste positive electrode active material, for example, compared with the non-cured defluorinated regenerated active material, the electrical performance of the regenerated positive electrode active material, such as discharge capacity and cycle, can be obviously improved by recycling the regenerated positive electrode active material.

Preferably, the method comprises the step of performing curing defluorination treatment on the positive active material of the waste lithium ion battery, so as to improve the discharge capacity of the regenerated positive active material. The inventor continuously and deeply researches to discover that the aging and fluorine removal of the waste positive active material is helpful to obviously improve the discharge capacity of the regenerated positive active material.

The inventor researches and discovers that flowing gas is blown into a curing system or negative pressure conditions are continuously generated, and flowing gas flow (such as air) or negative pressure equipment is adopted to carry away and remove hydrogen fluoride gas generated by curing. The method of curing under the negative pressure condition or under continuous air flow blowing is adopted, so that the fluorine of the waste anode active material can be obviously removed, the electrical property of the regenerated anode active material is ensured, and the discharge capacity of the regenerated material is obviously improved; moreover, the method is beneficial to leaching the positive active material, improves the crystalline phase purity of the regenerated material, and further improves the performance of the regenerated material.

The inventor researches and discovers that the curing and fluorine removing effects can be further improved by controlling parameters such as the acid usage amount, the curing time, the curing temperature, the vacuum degree or the gas flow in the curing process and the like in the curing process, and the electrical properties of the recycled positive active material can be further improved; in addition, the recovery rate of the positive electrode active material can be improved.

Preferably, the acid solution is concentrated inorganic acid. The concentrated mineral acid is, for example, a commercially available mineral acid without dilution. Researches find that the concentrated inorganic acid is beneficial to further improving the leaching effect of each component and also beneficial to improving the curing and curing defluorination effect, thereby improving the performance of the recycled electrode material.

Preferably, the H + concentration of the acid solution is not lower than 12 mol/L.

More preferably, the acid solution is at least one of concentrated hydrochloric acid, concentrated sulfuric acid and concentrated phosphoric acid. The concentration of the concentrated hydrochloric acid is not lower than 12mol/L for example. The concentrated sulfuric acid concentration is, for example, not lower than 18.4 mol/L. The concentration of the concentrated phosphoric acid is, for example, not less than 15 mol/L. The use of the preferred concentrated acid solution can improve the aging effect, for example, the leaching rate of the positive electrode active material is more than 95%, and can further improve the aging and fluorine removal effects.

More preferably, the acid solution is concentrated sulfuric acid (18.4 mol/L). The aging by concentrated sulfuric acid has unexpected technical effects, such as greatly improving the leaching rate of the positive active material to be close to 100%.

Preferably, the temperature of the aging process is 100 ℃ to 255 ℃. Most of the fluorine remaining in the positive electrode active material in this temperature range is removed, for example, the removal rate is 90% or more.

Further preferably, the temperature of the curing process is 200-255 ℃; more preferably 240 to 250 ℃. The fluorine element removal rate of the positive active material in the temperature range is more than 99%.

Preferably, the aging time is 0.5 to 5.0 hours.

Under the curing condition, the vacuum degree or the flow of the introduced airflow is further controlled, so that the curing and fluorine removing effects can be further ensured.

Preferably, the vacuum degree of the curing process is not higher than 0.09 MPa; preferably not higher than 0.05 MPa.

During the maturation, a gas flow is introduced, for example, in an inert atmosphere, such as nitrogen.

Preferably, the flow rate of the gas flow is not lower than 500 ml/min; more preferably 0.75 to 2L/min.

By the curing conditions, good curing and fluorine removal effects can be ensured, and the leaching rate of the positive active material can be obviously improved.

Preferably, the fluorine content of the regenerated positive electrode active material is controlled to be not higher than 20 ppm. The inventor researches and discovers that the electrical property of the material can be obviously improved by controlling the fluorine content of the regenerated positive electrode active material to be below the range.

Preferably, the waste lithium ion battery is a waste lithium iron phosphate battery.

The method of the invention also preferably comprises the steps of leaching the aged and defluorinated solution (namely the aged solution) by water to obtain an acidic leaching solution, and sequentially carrying out copper removal, aluminum removal, P, Fe and Li molar ratio regulation and coprecipitation treatment on the acidic leaching solution to obtain the regenerated positive electrode active material. The solution after curing and defluorination is subjected to the series of treatments, so that the curing and defluorination effects can be further improved, and the recovery rate of the positive active material is improved.

Preferably, the aging defluorination treatment of the present invention is performed under a high-concentration inorganic acid, and the solution after the aging defluorination treatment is subjected to water leaching (also referred to as water leaching in the present invention) to obtain an acidic leachate enriched with the positive electrode active material.

The water leaching method of the solution after curing and defluorination can adopt the prior method.

Preferably, the liquid-solid ratio is 3: 1 mL/g-10: 1mL/g during water leaching, and the liquid-solid ratio is the volume (in mL) of water corresponding to each unit mass (in g) of the positive electrode active material.

The water leaching temperature is between normal temperature and 95 ℃.

The water leaching time is 0.5 to 5.0 hours.

The acid leachate obtained by water leaching is mainly enriched with elements of positive active materials, such as materials of iron, phosphorus, lithium and the like, and also contains impurities, such as copper ions, aluminum ions and the like, and the fluorine content in the acid leachate is well controlled.

In the invention, under the innovative curing method of the invention, the electrical property of the recycled positive active material can be further improved by cooperating with the copper removal and aluminum removal treatment in the acidic leaching solution.

The copper and aluminum can be removed by the existing method.

Preferably, the copper removal process comprises adding iron powder into the acidic leaching solution, and performing copper removal treatment to obtain copper removal leaching solution; wherein the adding amount of the iron powder is 1.0-1.5 times of the theoretical molar amount (namely the amount of the iron powder in the acidic leaching solution for replacing copper ions and reducing ferric ions). The reaction temperature for copper removal is normal temperature-95 ℃. The reaction time for copper removal is 0.25 h-2.0 h.

After the copper removal treatment, solid-liquid separation is carried out, and the obtained filtrate (namely the copper removal leaching solution) is subjected to subsequent aluminum removal treatment.

And (4) carrying out extraction and dealumination treatment on the decoppered leaching solution to obtain the dealuminated leaching solution.

In the process of the extraction and aluminum removal treatment, the extractant is P204-sulfonated kerosene mixed liquor, wherein the concentration of P204 is 0.6-1.5 mol/L. The ratio of the extraction process is 1: 1-1/5 (the ratio of the extraction process is the volume of the extracting agent to the volume of the water phase). The initial pH value of the water phase is 1.5-3.0.

Namely, the pH value of the copper-removing leaching solution is adjusted to be 1.5-3.0 in advance, and then the extractant is added according to the ratio for extraction and aluminum removal treatment; the extracted water phase is the leaching solution with the impurity removed.

Adjusting the molar ratio of Li to Fe to P of the aluminum-removing leaching solution to be (1.0-1.1) to 1.

In the invention, after the molar ratio of P, Fe and Li is adjusted, lithium iron phosphate is obtained; the method for obtaining lithium iron phosphate can adopt the conventional method, such as coprecipitation method.

In the present invention, the molar ratio can be controlled by a material containing one or more elements selected from P, Fe, and Li.

Preferably, the molar ratio of P, Fe and Li is regulated by a lithium source and/or a phosphorus source.

Further preferably, the lithium source includes at least one of lithium sulfate, lithium hydroxide, lithium carbonate, or lithium phosphate. The phosphorus source comprises at least one of ammonium monohydrogen phosphate and diammonium hydrogen phosphate.

And recovering the solution with the molar ratio of Li to Fe to P by adopting a coprecipitation method to obtain the regenerated positive active material.

The coprecipitation process comprises the steps of adding ascorbic acid into a solution with the molar ratio of Li to Fe to P adjusted, stirring for 1.0-3.0 h at the temperature of 50-100 ℃, controlling the pH value to be 7-11, and filtering to obtain the regenerated positive electrode active material.

The invention relates to a method for improving the electrical property of a positive active material regenerated by a waste lithium iron phosphate battery, which comprises the following steps of

Step (1), carrying out short-circuit discharge and disassembly on waste lithium iron phosphate batteries to obtain a material containing a positive plate, then crushing the material, carrying out oxidizing roasting at 400-660 ℃ to remove a binder, and screening to obtain a positive active material;

curing the obtained positive electrode active material with acid liquor at 240-250 ℃; the curing process is carried out under the condition of negative pressure or under the condition of continuous air flow blowing; the acid liquor is at least one of concentrated hydrochloric acid, concentrated sulfuric acid and concentrated phosphoric acid;

leaching the aged materials with water to obtain an acidic leaching solution, and then removing copper and aluminum to obtain an aluminum-removed leaching solution;

and (4) regulating and controlling the molar ratio of P, Fe and Li in the aluminum-removing leaching solution obtained in the step (3), and carrying out coprecipitation to obtain regenerated lithium iron phosphate.

In the preferable method, through the innovative aging treatment in the step (2), airflow is continuously blown into a solution system in the aging treatment process, and HF formed by the reaction of fluorine raw materials in the positive electrode active material in the aging process is carried by the airflow; or, the curing system is placed under a continuous negative pressure condition through vacuum equipment, so that the formed HF is continuously gasified from the curing solution system and enters the vacuum system; the aim of curing and removing fluorine impurities in the positive electrode active material is achieved through the two preferable modes. The inventor discovers through research that the electrical property of the recycled positive active material can be obviously improved through the curing defluorination process of the waste positive active material; for example, the discharge capacity is obviously improved, and the cycle performance is also improved.

In the invention, the existing methods known by the technicians in the field can be adopted for the methods of short-circuit discharge, disassembly, crushing and the like of the waste lithium iron phosphate batteries.

Preferably, the material containing the positive plate also allows the negative plate and the separator to be contained. The method allows the mixing and crushing of the anode plate, the cathode plate and the diaphragm; thus, the production automation of enterprises can be improved.

In the preferred method, under the oxidizing roasting, the method can help the fluorine removal of the subsequent curing process, and further help the performance of the obtained positive active material to be recycled.

The invention relates to a more preferable recycling method of a positive active material of a waste lithium iron phosphate battery, which comprises the following specific steps of

Step (1) after the residual electric quantity of the waste lithium iron phosphate battery is discharged, directly crushing a battery cell obtained by disassembling to obtain a mixture of a positive plate, a negative plate and a diaphragm; and roasting the mixture at low temperature in an oxidizing atmosphere, removing the binder, and then screening to separate the positive active powder of the lithium iron phosphate battery from clean aluminum and copper foils, wherein the aluminum and the copper foils are recovered by smelting.

Step (2) inorganic acid curing is carried out on the battery material of the undersize product, and meanwhile, the fluorine element in the lithium iron phosphate battery material volatilized by hydrogen fluoride gas is taken away by adopting flowing air;

adding water into the cured battery material according to a certain liquid-solid ratio, keeping the temperature constant, and leaching by stirring; and (3) adding iron powder into the acidic leaching solution for replacement and copper removal, and extracting and removing aluminum from the P204-sulfonated kerosene to obtain the leaching solution after impurity removal.

And (4) adding a lithium source and a phosphorus source into the acidic leaching solution, adjusting the concentrations of metal ions and phosphate ions in the leaching solution, and performing coprecipitation to prepare lithium iron phosphate.

Preferably, in the step (1), discharging residual electric quantity from the waste lithium iron phosphate battery, disassembling the battery, and directly crushing the disassembled battery cell to obtain a mixed battery material of the positive electrode sheet, the negative electrode sheet and the diaphragm; roasting the battery material at the temperature of 400-660 ℃ (preferably 500-600 ℃) for 0.5-5.0 h, then separating the heat-treated positive active powder from the aluminum foil and the copper foil through screening, and recovering the aluminum foil or the copper foil through smelting.

Preferably, in the step (2), the amount of the inorganic acid is controlled to cure the separated positive electrode active powder, and flowing air or negative pressure equipment is adopted to carry away the curing to generate hydrogen fluoride gas, wherein the curing temperature is 100-260 ℃, and the curing time is 0.5-5.0 h; soaking the aged lithium iron phosphate in water, wherein the liquid-solid ratio is 3: 1 mL/g-10: 1mL/g, the water soaking temperature is room temperature-95 ℃, and the water soaking time is 0.5 h-5.0 h; carrying out medium vacuum filtration or filter pressing on the leachate obtained by water leaching to obtain acidic filtrate, and then detecting and analyzing the contents of fluorine, iron, phosphorus, lithium, copper and aluminum in the leachate;

preferably, in the step (3), iron powder is adopted to replace and remove copper impurities, the adding amount of the iron powder is 1.0-1.5 times of the theoretical dosage, the reaction temperature is normal temperature-95 ℃, and the reaction time is 0.25-2.0 h; and (3) extracting P204-sulfonated kerosene to remove aluminum impurities, wherein the concentration of P204 is 0.6-1.5 mol/L, and the initial pH value of the water phase is 1.5-3.0 compared with 1: 1-1: 5.

Preferably, in the step (4), a lithium source and an iron source are added to adjust the molar ratio of Li to Fe to P to be (1.0-1.1) to 1, 10 g-200 g of ascorbic acid is added, the mixture is stirred for 1.0 h-3.0 h at 50 ℃ -100 ℃, ammonia water is added to control the pH value to be 7-11, and the mixture is filtered to obtain lithium iron phosphate precipitate.

Compared with the prior art, the invention has the following advantages or positive effects.

(1) The invention innovatively discovers that the electrical property of the recovered positive active material can be unexpectedly improved by carrying out curing defluorination treatment on the waste positive active material.

(2) Researches also find that the anode plate can be cooperated with a subsequent curing step by roasting, so that the curing and fluorine removal effects are obviously improved, the crystalline phase of materials is improved, and the electrical properties of the recycled anode active material are improved.

(3) Compared with the existing treatment method of the waste lithium iron phosphate power battery, the method does not need to separate the positive plate, the negative plate and the diaphragm, but directly crushes and roasts at low temperature to thermally oxidize and decompose the binder PVDF, thereby separating the battery active material from the aluminum foil, reducing the process flow and facilitating the automatic production of enterprises.

(4) Compared with the existing treatment method of the waste lithium iron phosphate power battery, the method has the advantages that the active material obtained by low-temperature roasting is subjected to curing and water leaching by adopting concentrated sulfuric acid, so that the leaching rate of phosphorus, lithium and iron elements is close to hundred percent, the process is simple, the efficiency is high, and the consumption of the concentrated sulfuric acid is small.

(5) Compared with the existing treatment method of the waste lithium iron phosphate power battery, the method disclosed by the invention has the advantages that the active material is subjected to sulfuric acid curing by adopting concentrated sulfuric acid, the curing temperature is controlled, and the hydrogen fluoride gas generated by curing can be effectively taken away by adopting flowing air or negative pressure equipment, so that the condition that the performance of the lithium iron phosphate anode active material subsequently synthesized is influenced by the fluorine ions entering the leachate is prevented, and the cost for subsequently treating fluorine-containing wastewater is increased.

(6) Compared with the existing treatment method of the waste lithium iron phosphate power battery, the method adopts iron powder displacement to remove copper and adopts P204-sulfonated kerosene extraction to remove aluminum to purify the acidic leaching solution, thereby reducing the influence of copper and aluminum element impurities on the performance of the lithium iron phosphate prepared by coprecipitation in the step (3).

(7) According to the technical scheme, the discharge capacity of the recycled lithium iron phosphate at 0.2 ℃ can be increased to 159.4 mA-h/g, and compared with a non-aging defluorination technology, the discharge capacity is increased by 30%.

Drawings

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

FIG. 2 shows XRD patterns of lithium iron phosphate prepared by coprecipitation;

fig. 3 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in example 1;

fig. 4 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in comparative example 1;

fig. 5 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in example 2;

fig. 6 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in comparative example 2;

fig. 7 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in example 3;

fig. 8 is a graph showing the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in comparative example 3;

fig. 9 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in example 4;

fig. 10 is a graph showing the discharge specific capacity and cycle performance of the lithium iron phosphate material prepared in comparative example 4;

fig. 11 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material recovered in example 5;

fig. 12 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material recovered in example 6;

fig. 13 shows the discharge specific capacity and cycle performance of the lithium iron phosphate material recovered in example 7.

Detailed Description

The following will further explain the recycling method of the waste lithium iron phosphate battery positive active material in the invention with reference to the accompanying drawings and the specific embodiment.

As shown in fig. 1, after the waste lithium iron phosphate battery is discharged with residual electric quantity, the battery core obtained by dismantling is directly crushed to obtain a mixture of a positive plate, a negative plate and a diaphragm; and roasting the mixture at low temperature in an oxidizing atmosphere, removing the binder, and then screening to separate the positive active powder of the lithium iron phosphate battery from clean aluminum and copper foils, wherein the aluminum and the copper foils are recovered by smelting. Inorganic acid curing of undersize cell materials while fluorination with moving air entrainmentFluorine element in the lithium iron phosphate battery material with hydrogen gas volatilized. Adding water into the cured battery material according to a certain liquid-solid ratio, keeping the temperature constant, and stirring and leaching; and (3) adding iron powder into the acidic leaching solution for replacement and copper removal, and extracting and removing aluminum from the P204-sulfonated kerosene to obtain the leaching solution after impurity removal. Adding a lithium source and a phosphorus source into the acidic leaching solution, adjusting the concentration of metal ions and phosphate ions in the leaching solution, and performing coprecipitation to prepare lithium iron phosphate. As shown in FIG. 2, the XRD pattern obtained by the present invention is comparable to that of standard LiFePO₄The samples are the same, which shows that the lithium iron phosphate obtained by the invention is similar to standard LiFePO₄The sample unit cells are identical. In the following examples and comparative examples, the concentration of concentrated hydrochloric acid was 12 mol/L. The concentration of concentrated sulfuric acid is 18.4 mol/L. The concentration of concentrated phosphoric acid was 15 mol/L. All were commercially available analytical pure materials.