CN111977628A - Method for recovering and preparing lithium iron phosphate from lithium ion battery - Google Patents

Abstract

The present invention provides a method for recovering and preparing lithium iron phosphate from a lithium ion battery disclosed in the present invention, comprising the following steps: S1: disassemble a decommissioned lithium iron phosphate battery after discharge treatment to obtain a positive electrode of the battery; Crushing and sieving, then air separation to obtain lighter powder; S2: carrying out oxidative leaching of the powder obtained in S1 to obtain filtrate and filter residue containing metal ions, phosphate ions and acid ions; S3: to the filtrate obtained in S2 Phosphoric acid is added to obtain an iron phosphate precipitate containing aluminum element, which is used as a precursor for preparing lithium iron phosphate material; S4: The precursor obtained in S3 is mixed with a lithium source to obtain a mixture; S5: The mixture obtained in S4 and the carbon source are ground evenly High temperature sintering is performed in an inert atmosphere to obtain an aluminum-doped lithium iron phosphate cathode material. The preparation process of the invention is short, the cost is low, the operability is strong, and the prepared lithium iron phosphate positive electrode material has excellent performance and high application value.

Description

Method for recovering and preparing lithium iron phosphate from lithium ion battery

technical field

The invention relates to the technical field of energy storage materials, in particular to a method for recovering and preparing lithium iron phosphate from a lithium ion battery.

Background technique

Since Japan's Sony Corporation took the lead in commercializing lithium-ion batteries in 1991, lithium-ion batteries have the advantages of high discharge voltage, large specific energy, small self-discharge, long cycle life and no memory effect, and have gradually replaced traditional secondary power sources. , widely used in portable electronic equipment, electric vehicles, space technology, defense industry, etc. Lithium iron phosphate batteries have gradually dominated the lithium-ion battery market due to their good safety, low cost, and non-toxicity.

With the popularization of electric vehicles, the number of retired batteries has grown rapidly, and direct disposal will cause environmental pollution and waste of resources. How to properly recycle retired batteries has become the focus of attention. Patent CN111370800A treats the lithium iron phosphate cathode sheet to obtain iron phosphate, iron hydroxide and lithium carbonate. The obtained iron phosphate is not doped with elements. If it is used as a lithium iron phosphate precursor, it cannot be used to dope lithium iron phosphate. Modification effect. The patent CN102664294A crushes the battery into pieces, soaks it with sodium hydroxide solution and stirs it, separates the current collector from the positive and negative electrode powder by filtering, washing and sieving, then adjusts the ratio of each element in the powder, and sinters to obtain lithium iron phosphate Positive electrode material, the patent ignores the dissolution effect of sodium hydroxide solution on the aluminum foil of the positive electrode current collector. During the soaking process, a certain amount of aluminum will dissolve in the solution and exist in the form of Al ³⁺ , which affects the preparation of lithium iron phosphate positive electrode. Patent CN111135939A separates electrode materials by mechanical crushing and vibrating screening, recovers lithium resources by hydrometallurgical treatment, and does not recover other valuable elements, and the mechanical separation process of current collectors and powder materials in this patent is complicated ,higher cost. According to the above content, it can be found that the existing recycling process has disadvantages such as cumbersome steps, high cost, and low practical application value. It is imperative to develop a simple and efficient process for recycling decommissioned lithium iron phosphate batteries.

SUMMARY OF THE INVENTION

The present invention provides a method for recovering and preparing lithium iron phosphate from a lithium ion battery, the purpose of which is to provide a simple and efficient lithium battery recovery and utilization process, which is convenient and quick to recover and prepare lithium iron phosphate from decommissioned lithium iron phosphate batteries. The lithium iron phosphate precursor is obtained and the lithium iron phosphate positive electrode material with excellent performance is re-prepared.

In order to achieve the above object, the present invention provides a method for recovering and preparing lithium iron phosphate from a lithium ion battery, comprising the following steps:

S1: dismantling the decommissioned lithium iron phosphate battery after discharge treatment to obtain the positive electrode of the battery, crushing, sieving, and air sorting the obtained positive electrode of the battery, and collecting the powder;

S2: carry out oxidative leaching with the powder obtained in S1 under acidic conditions to obtain filtrate and filter residue;

S3: the pH of the filtrate obtained by S2 is adjusted to 1-3 with an alkaline solution, and phosphoric acid is added to the filtrate to obtain a ferric phosphate precipitate containing a small amount of aluminum, which is used as a precursor for preparing lithium iron phosphate materials;

S4: mixing the precursor obtained in S3 with the lithium source to obtain a mixture;

S5: After grinding the mixture obtained in S4 and the carbon source uniformly, sintering is performed in an inert atmosphere to obtain an aluminum-doped lithium iron phosphate positive electrode material.

Preferably, in the S1, sieves with a mesh diameter of 0.5-2mm are used for screening, and the air separation equipment is a cyclone separator, and the powder that does not meet the requirements is returned to the crusher for further crushing.

Preferably, in the S2, the acid used for leaching is one or more of hydrochloric acid, sulfuric acid, acetic acid, oxalic acid, methanesulfonic acid and benzenesulfonic acid, and the acid concentration is 0.1-5 mol/L.

Preferably, in the S2, hydrogen peroxide is added to carry out oxidative leaching, and the concentration of the hydrogen peroxide is 5-20%.

Preferably, in the S2, the filtrate contains metal ions, phosphate ions and acid ions, the metal ions are Fe ³⁺ and Al ³⁺ , and the filter residue is a mixture of binder and positive conductive carbon.

Preferably, in the S3, the alkali solution is one or more of NaOH solution, KOH solution and ammonia water, the alkali concentration in the alkali solution is 0.1-5 mol/L, and the phosphoric acid concentration is 1-3 mol/L,

Preferably, in the S3, the molar ratio of aluminum element to iron element in the iron phosphate precipitate is 0.1-10:100.

Preferably, in the S4, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium phosphate, and lithium dihydrogen phosphate.

Preferably, in the S4, the mass ratio of lithium in the lithium source to iron in the precursor is 1.05-1.15:1.

Preferably, in the S5, the carbon source is one of graphite, conductive carbon, acetylene black, conductive carbon black, carbon fiber, carbon nanotubes, nanocarbon microspheres, glucose, cellulose, sucrose, fructose, and phenolic resin or Several, the mass ratio of the carbon source to the mixture is 0.005:1 to 0.2:1.

Preferably, in the S5, the sintering temperature is 600-850° C., the sintering time is 8-12 hours, the inert gas is argon or a hydrogen-argon mixture, and the hydrogen in the hydrogen-argon mixture accounts for 3% of the total volume of the hydrogen-argon mixture. 1% to 10%.

The above-mentioned scheme of the present invention has the following beneficial effects:

1. The recycling process is simple. The positive electrode of the battery is directly crushed and then sieved. The different physical and chemical properties of the positive electrode current collector aluminum foil and the positive electrode material are used to carry out airflow separation without adding chemical reagents to separate the electrode sheet and the positive electrode material. Energy consumption and cost lower.

2. A small amount of aluminum element contained in the powder obtained by air separation does not need to be ion impurity removal. When using phosphoric acid to precipitate iron ions, a part of aluminum will enter into the iron phosphate precursor together. In the subsequent material preparation process Aluminium-doped lithium iron phosphate cathode material can be directly obtained.

3. Recycling and preparing lithium iron phosphate cathode materials from decommissioned lithium iron phosphate batteries has a short process, low cost and strong operability.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, the following will be described in detail with reference to specific embodiments.

Example 1

A method for recovering and preparing lithium iron phosphate from a lithium ion battery, comprising the following steps:

(1) Disassemble the decommissioned lithium iron phosphate battery after discharge treatment to obtain the positive electrode of the battery, crush and sieve the positive electrode of the battery with a crusher, sieve with a 1mm screen, and then conduct airflow sorting on the screening material , collect lighter powder;

(2), use the hydrochloric acid of 1mol/L and 10% hydrogen peroxide to carry out oxidative leaching to the powder obtained in step (1), obtain the filtrate and the filter residue containing metal ion, phosphate ion and acid ion, and the metal ion in the filtrate is Fe ³⁺ , Al ³⁺ , the anions are PO ₄ ^3- and Cl ^- , the filter residue is a mixture of binder and positive electrode conductive carbon;

(3), use the NaOH solution of 0.5mol/L to adjust the pH of the filtrate obtained in step (2) to 2, and add the phosphoric acid of 3mol/L to the filtrate to obtain the iron phosphate precipitation containing a small amount of aluminum, and aluminum in the precipitation The molar ratio with iron element is 8:100;

(4), the obtained precursor in step (3) is mixed with lithium carbonate, and control lithium: iron is 1.15:1;

(5) After grinding and mixing the mixture obtained in step (4) and glucose according to a mass ratio of 1:0.2, in a hydrogen-argon mixture containing 5% hydrogen, react at 700° C. for 10 hours to obtain an aluminum-doped lithium iron phosphate cathode material .

After testing, the sintered aluminum-doped lithium iron phosphate cathode material was charged and discharged at 0.1C between 2 and 3.75V, the first charge specific capacity was 159mAh g ^-1 , the first discharge specific capacity was 154mAh g ^-1 , and the first charge and discharge capacity was 154mAh g -1 . The efficiency is 96.8%, and the reversible capacity is still 122mAh g ^-1 after 100 cycles at 1C.

Example 2

A method for recovering and preparing lithium iron phosphate from a lithium ion battery, comprising the following steps:

(1) Disassemble the decommissioned lithium iron phosphate battery after discharge treatment to obtain the positive electrode of the battery, crush and sieve the positive electrode of the battery with a crusher, sieve with a 1.5mm screen, and then conduct airflow separation on the screened material Select and collect lighter powder;

(2), use the sulfuric acid of 2mol/L and the hydrogen peroxide of 15% to carry out oxidative leaching to the powder obtained in step (1), obtain the filtrate and the filter residue containing metal ion, phosphate ion and acid ion, and the metal ion in the filtrate is Fe ³⁺ , Al ³⁺ , the anions are PO ₄ ^3- and SO ₄ ^2- , the filter residue is a mixture of binder and positive electrode conductive carbon;

(3), the pH of the filtrate obtained in step (2) is adjusted to 1.5 using the ammonia solution of 1 mol/L, and the phosphoric acid of 2 mol/L is added to the filtrate to obtain the ferric phosphate precipitation containing a small amount of aluminum, and in the precipitation, aluminum and The molar ratio of iron is 10:100;

(4), the obtained precursor in step (3) is mixed with lithium phosphate, and control lithium: iron is 1.1:1;

(5) After grinding and mixing the mixture obtained in step (4) and acetylene black according to a mass ratio of 1:0.02, in a hydrogen-argon mixture containing 10% hydrogen, react at 600° C. for 12 hours to obtain an aluminum-doped lithium iron phosphate positive electrode Material.

After testing, the sintered aluminum-doped lithium iron phosphate cathode material was charged and discharged at 0.1C between 2 and 3.75V, the first charge specific capacity was 158mAh g ^-1 , and the first discharge specific capacity was 152mAh g ^-1 . The discharge efficiency is 96.2%, and the reversible capacity is still 119mAh g ^-1 after 100 cycles at 1C.

Example 3

A method for recovering and preparing lithium iron phosphate from a lithium ion battery, comprising the following steps:

(1) Disassemble the decommissioned lithium iron phosphate battery after discharge treatment to obtain the positive electrode of the battery, crush and sieve the positive electrode of the battery with a crusher, sieve with a 0.5mm screen, and then conduct airflow separation on the screened material Select and collect lighter powder;

(2), use the hydrochloric acid of 5mol/L and the hydrogen peroxide of 5% to carry out oxidative leaching to the powder material obtained in step (1), obtain the filtrate and the filter residue that contain metal ion, phosphate ion and acid ion, and the metal ion in the filtrate is Fe ³⁺ , Al ³⁺ , the anions are PO ₄ ^3- and Cl ^- , the filter residue is a mixture of binder and positive electrode conductive carbon;

(3), use the KOH solution of 0.5mol/L to adjust the pH of the filtrate obtained in step (2) to 2.5, and add the phosphoric acid of 5mol/L to the filtrate to obtain a ferric phosphate precipitation containing a small amount of aluminum, and aluminum in the precipitation The molar ratio with iron element is 0.5:100;

(4), the obtained precursor in step (3) is mixed with lithium acetate, and control lithium: iron is 1.05:1;

(5), after grinding and mixing the mixture obtained in step (4) and carbon nanotubes in a mass ratio of 1:0.005. In an argon atmosphere, the reaction was carried out at 800 °C for 15 h. An aluminum-doped lithium iron phosphate positive electrode material is obtained.

After testing, the sintered aluminum-doped lithium iron phosphate cathode material was charged and discharged at 0.1C between 2 and 3.75V, the first charge specific capacity was 155mAh g ^-1 , and the first discharge specific capacity was 151mAh g ^-1 . The discharge efficiency is 97.4%, and the reversible capacity is still 127mAh g ^-1 after 100 cycles at 1C.

The above are the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A method for recovering and preparing lithium iron phosphate from a lithium ion battery is characterized by comprising the following steps:

s1: the method comprises the following steps of (1) discharging the retired lithium iron phosphate battery, disassembling to obtain a battery anode, crushing, screening and airflow sorting the obtained battery anode, and collecting to obtain powder;

s2: carrying out oxidation leaching on the powder obtained in the step S1 under an acidic condition to obtain filtrate and filter residue;

s3: adjusting the pH of the filtrate obtained in the step S2 to 1-3 by using an alkali solution, and adding phosphoric acid into the filtrate to obtain an iron phosphate precipitate containing an aluminum element, wherein the iron phosphate precipitate is used as a precursor for preparing a lithium iron phosphate material;

s4: mixing the precursor obtained in the step S3 with a lithium source to obtain a mixture;

s5: and grinding the mixture obtained in the step S4 and a carbon source uniformly, and sintering in an inert atmosphere to obtain the aluminum-doped lithium iron phosphate cathode material.

2. The method for recycling and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S1, a screen with the mesh diameter of 0.5-2 mm is used for screening, and the airflow separation equipment is a cyclone separator.

3. The method for recovering and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S2, the acid used for leaching is one or more of hydrochloric acid, sulfuric acid, acetic acid, oxalic acid, methanesulfonic acid and benzenesulfonic acid, and the concentration of the acid is 0.1-5 mol/L.

4. The method for recovering and preparing lithium iron phosphate from the lithium ion battery according to claim 1, wherein hydrogen peroxide is added to S2 for oxidation leaching, and the concentration of the hydrogen peroxide is 5-20%.

5. The method for recovering and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S3, the alkali solution is one or more of a NaOH solution, a KOH solution and ammonia water, the alkali concentration in the alkali solution is 0.1-5 mol/L, and the phosphoric acid concentration is 1-3 mol/L.

6. The method for recovering and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S3, the molar ratio of aluminum element to iron element in the ferric phosphate precipitate is 0.1-10: 100.

7. The method of claim 1, wherein in S4, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium phosphate, and lithium dihydrogen phosphate.

8. The method for recovering and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S4, the mass ratio of lithium in the lithium source to iron in the precursor is 1.05-1.15: 1.

9. The method for recovering and preparing lithium iron phosphate from the lithium ion battery according to claim 1, wherein in S5, the carbon source is one or more of graphite, conductive carbon, acetylene black, conductive carbon black, carbon fibers, carbon nanotubes, carbon nanospheres, glucose, cellulose, sucrose, fructose and phenolic resin, and the mass ratio of the carbon source to the mixture is 0.005: 1-0.2: 1.

10. The method for recovering and preparing lithium iron phosphate from a lithium ion battery according to claim 1, wherein in the step S5, the sintering temperature is 600-850 ℃, the sintering time is 8-12 h, the inert gas is argon or a hydrogen-argon mixture, and hydrogen in the hydrogen-argon mixture accounts for 1-10% of the total volume of the hydrogen-argon mixture.