阅读说明：本技术 一种废旧磷酸铁锂电池正极活性材料回收利用方法 (Method for recycling positive active material of waste lithium iron phosphate 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,具体公开了一种废旧磷酸铁锂电池正极活性材料回收利用方法,废旧磷酸铁锂电池经短路放电、拆解得包含正极片的物料,随后将该物料破碎、脱粘结剂、筛分,得正极活性材料；将得到的正极活性材料进行酸液熟化去氟处理；熟化过程在负压条件或者在连续气流吹扫下进行；熟化后的物料经水浸出,得浸出液；调控得到的浸出液的P、Fe、Li摩尔比,回收得到磷酸亚铁锂。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 particularly discloses a method for recycling a positive active material of a waste lithium iron phosphate battery, wherein the waste lithium iron phosphate battery is subjected to short-circuit discharge and disassembly to obtain a material containing a positive plate, and then the material is crushed, subjected to binder removal and screened to obtain the positive active material; carrying out acid liquor curing defluorination treatment on the obtained positive electrode active material; the curing process is carried out under the condition of negative pressure or under the condition of continuous air flow blowing; leaching the cured materials with water to obtain a leaching solution; and regulating and controlling the molar ratio of P, Fe and Li in the obtained leachate, and recycling to obtain the lithium iron phosphate. 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 recycling a positive active material of a waste lithium iron phosphate battery is characterized by comprising the following steps:

(1) carrying out short-circuit discharge and disassembly on the waste lithium iron phosphate battery to obtain a material containing a positive plate, crushing the material, removing a binder and screening to obtain a positive active material;

(2) performing acid liquor curing defluorination treatment on the positive electrode active material in the step (1); the curing treatment process is carried out under the condition of negative pressure or under the condition of continuous air flow purging;

(3) carrying out water leaching treatment on the material aged in the step (2) to obtain a leaching solution;

(4) regulating the molar ratio of P, Fe and Li of the leachate obtained in the step (3) to be (1.0-1.1): 1, and recovering to obtain the lithium iron phosphate.

2. The method for recycling the positive active material of the waste lithium iron phosphate batteries according to claim 1, wherein the material containing the positive plate in the step (1) further comprises a negative plate and a diaphragm.

3. The method for recycling the positive active material of the waste lithium iron phosphate battery as claimed in claim 1, wherein in the step (1), the binder is removed by an oxidizing roasting method; wherein the temperature of the oxidizing roasting process is 400-660 ℃.

4. The method for recycling the positive active material of the waste lithium iron phosphate battery as claimed in claim 1, wherein in the step (2), the acid solution is a strong inorganic acid solution, and the strong inorganic acid is at least one of hydrochloric acid, sulfuric acid and phosphoric acid.

5. The method for recycling the positive active material of the waste lithium iron phosphate battery as claimed in claim 4, wherein in the step (2), the acid solution 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.

6. The method for recycling the positive active material of the waste lithium iron phosphate batteries as claimed in any one of claims 1 to 3, wherein in the water leaching process, the volume ratio of water to the positive active material is 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.

7. The method for recycling the positive active material of the waste lithium iron phosphate batteries as claimed in any one of claims 1 to 5, wherein the temperature of the curing process is 100 ℃ to 260 ℃ and the curing time is 0.5h to 5.0 h.

8. The method for recycling the positive active material of the waste lithium iron phosphate batteries according to claim 7, wherein in the step (3), the obtained leachate is subjected to copper removal and aluminum removal to obtain an impurity-removed leachate, and then the impurity-removed leachate is subjected to the step (4).

9. The method for recycling the positive active material of the waste lithium iron phosphate batteries according to claim 1, wherein in the step (3): adding iron powder into the leaching solution, and performing copper removal treatment to obtain a copper-removed 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.

10. The method for recycling the positive active material of the waste lithium iron phosphate batteries according to claim 9, wherein in the step (3): extracting the copper-removing leaching solution to obtain an impurity-removing leaching solution; the extractant is P204-sulfonated kerosene mixed liquor, wherein the concentration of P204 is 0.6 mol/L-1.5 mol/L; the initial pH value of the aqueous phase is 1.5-3.0 in the extraction process compared with 1: 1-1: 5.

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 iron phosphate battery.

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. Patent CN101916889B discloses a method for recycling and preparing lithium iron phosphate by a lithium ion power battery, and the method uses inorganic acid to leach Li after separating lithium iron phosphate anode active material⁺、Fe²⁺And PO₄ ^3-And then adding a lithium source or an iron source and ascorbic acid, controlling the pH value to obtain a precipitate, and finally performing ball milling, drying and calcining in a sucrose aqueous solution to obtain the lithium iron phosphate.

Disclosure of Invention

In order to solve the technical problem that the performance of the positive active material (the lithium iron phosphate) recovered from the existing waste lithium iron phosphate battery is not ideal, the invention provides a method for recycling the positive active material of the waste lithium iron phosphate battery, and aims to improve the electrical performance of the recovered positive active material by innovatively carrying out curing defluorination treatment on the positive active material.

A method for recycling a positive active material of a waste lithium iron phosphate battery comprises the following steps of

Step (1), carrying out short-circuit discharge and disassembly on the waste lithium iron phosphate battery to obtain a material containing a positive plate, and then crushing, removing a binder and screening the material to obtain a positive active material;

step (2), carrying out acid liquor curing defluorination treatment on the positive electrode active material obtained in the step (1); the curing process is carried out under the condition of negative pressure or under the condition of continuous air flow blowing;

leaching the aged materials with water to obtain leachate;

regulating the molar ratio of P, Fe and Li of the solution (leachate) obtained in the step (3) to be (1.0-1.1): 1, and recovering to obtain the lithium iron phosphate.

The inventor creatively discovers through a great deal of research that one main factor for restricting the performance of the positive active material obtained by recycling the waste lithium iron phosphate batteries 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 defluorination treatment on the recovery process of the positive active material. In the invention, through the innovative curing treatment in the step (2), airflow is continuously blown into a solution system in the curing treatment process, and HF formed by the reaction of fluorine raw materials in the anode active material in the curing 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 by carrying out the defluorination process in the step (2) on 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 electrode plate in the step (1) also allows the negative electrode plate and the separator to be contained. The method allows the mixing and crushing of the anode plate, the cathode plate and the diaphragm, so that the production automation of enterprises can be improved.

In the present invention, the binder removal method can adopt the existing methods, such as organic solvent soaking, oxidation roasting, etc. Further research shows that the oxidizing roasting treatment can cooperate with the innovative curing and defluorination steps of the invention, unexpectedly improve the defluorination effect in the subsequent curing process, improve the leaching rate of the anode active material, and also can unexpectedly recover the performance of the obtained anode active material.

Preferably, in step (1), binder is removed by an oxidizing roasting method; wherein the temperature of the oxidizing roasting process is 400-660 ℃. It was found that, at the preferred oxidizing and calcining temperature, the fluorine removal effect can be further improved unexpectedly, and the electrical properties of the recovered positive electrode active material can be further improved.

The oxidizing roasting process is carried out in an oxygen-containing atmosphere.

The oxygen-containing atmosphere is, for example, oxygen, air or a gas with different mixture ratios of nitrogen and oxygen.

Further preferably, the oxidizing/calcining temperature is 500 to 600 ℃. At this preferable temperature, it contributes to further increase of the leaching rate of lithium iron phosphate.

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

One key point of the invention is that flowing gas is blown into the curing system or negative pressure conditions are continuously created during the curing process, and flowing gas flow (such as air) or negative pressure equipment is adopted to carry away and remove hydrogen fluoride gas generated by curing. Moreover, research also finds that controlling parameters such as the acid usage amount, the curing time, the curing temperature and the like in the curing process can further improve the fluorine removal effect and further improve the electrical properties of the recycled positive active material.

Preferably, the acid solution is concentrated inorganic acid in step (2). 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 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. By using the preferred concentrated acid solution, the aging effect can be improved, for example, the leaching rate of the positive electrode active material is more than 95%, which contributes to further improving the defluorination effect.

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 260 ℃. 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 150-250 ℃; more preferably 240 ℃ to 250 ℃. The fluorine element removal rate of the positive active material in the temperature range is more than 99%.

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

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 fluorine removal effect 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 airflow is not lower than 500 mL/min; more preferably 0.75 to 1L/min.

By the aging condition, good fluorine removal effect can be ensured, and the leaching rate of the anode active material can be obviously improved.

After the aging treatment, a water leaching (also referred to as water leaching in the present invention) treatment is performed.

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 deionized water corresponding to the solid of each unit mass of the positive electrode active powder (in g).

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

The water leaching time is 0.5 to 5.0 hours.

The leachate obtained by water leaching is mainly enriched with elements of the positive active material, 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 leachate is well controlled.

Research shows that in the step (3), the obtained leachate is subjected to copper removal and aluminum removal treatment to obtain impurity-removed leachate, and then the impurity-removed leachate is subjected to the treatment in the step (4). Under the innovative curing method, the electrical property of the recycled positive active material can be further improved by cooperating with the copper removal and aluminum removal treatment.

Preferably, in the step (3), iron powder is added into the leaching solution to carry out copper removal treatment, so as 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 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.

Preferably, in the step (3), the copper-removal leaching solution is subjected to extraction treatment to obtain an impurity-removal leaching solution.

The extractant is P204 (di (2-ethylhexyl) phosphate) -sulfonated kerosene mixed liquor, wherein the concentration of the P204 is 0.6 mol/L-1.5 mol/L. The ratio of the extraction process to the extraction process is 1: 1-1: 5 (the ratio of the extraction agent volume to the water phase volume in the extraction process). 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.

In the invention, the lithium iron phosphate is obtained by adjusting the molar ratio of P, Fe and Li in the solution (leachate or impurity-removed leachate) obtained in the step (3), and the conventional method, such as a coprecipitation method, can be adopted for obtaining the lithium iron phosphate.

Preferably, in the step (4), the molar ratio of P, Fe and Li is adjusted to (1.0-1.1): 1.

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, a lithium source and/or a phosphorus source is added to the leachate obtained in step (4), and the molar ratio is controlled.

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.

The invention relates to a 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 ℃ for 0.5-5.0 h, separating the heat-treated positive active powder from aluminum foil and copper foil by screening, and recovering the aluminum foil or the copper foil by 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.

Further 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 the temperature of 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.

Preferably, the fluorine content of the recovered 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.

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 anode active material can be unexpectedly improved by carrying out defluorination treatment on the waste anode active material.

(2) Researches also find that the anode plate can be cooperated with a subsequent curing step by roasting treatment, so that the defluorination effect is obviously improved, the crystalline phase of materials is improved, and the electrical property of the recycled anode active material is 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-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.

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.