CN116315229A

CN116315229A - Method for recovering lithium from waste lithium ion battery and cooperatively repairing lithium iron phosphate material

Info

Publication number: CN116315229A
Application number: CN202310270219.2A
Authority: CN
Inventors: 杨则恒; 刘淳; 张卫新; 池梓维
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2023-03-20
Filing date: 2023-03-20
Publication date: 2023-06-23

Abstract

The invention discloses a method for recovering lithium from a waste lithium ion battery to cooperatively repair a lithium iron phosphate material. The method of the invention comprises the following steps: firstly, lithium resources in the anode material of the waste lithium ion battery can be selectively removed and effectively recycled; secondly, the waste lithium iron phosphate material can be subjected to lithium supplementing, repairing and regenerating so as to prepare a new lithium iron phosphate electrode material; thirdly, useful materials such as byproduct ferric phosphate, cobalt oxide, manganese oxide and the like after lithium removal can be obtained.

Description

Method for recovering lithium from waste lithium ion battery and cooperatively repairing lithium iron phosphate material

Technical Field

The invention relates to a method for recovering lithium from waste lithium ion batteries and cooperatively repairing regenerated lithium iron phosphate electrode materials, belonging to the field of lithium ion battery recovery and positive electrode material preparation.

Background

With the rapid growth of energy storage demands of consumer electronics, electric automobiles and wind energy and solar power generation facilities, lithium ion batteries have undergone a leap-type development. Particularly, the installed capacity of the power battery has exceeded the consumer electronics market under the push of the development of new energy automobiles. In 2025, the global lithium battery market demand is expected to reach 6942.65 billion dollars, and the volume of sales will reach 439.32GWh; with this, the retired power lithium battery reaches 134.49GWh, and the retired amount reaches 80.36 ten thousand tons. At present, strategic metal resources such as lithium, nickel, cobalt and the like are short, raw material prices are high, and along with the deep penetration of sustainable development strategies and the promotion of a double-carbon target, china puts forward higher requirements on renewable energy sources. Therefore, the development of the green, efficient and low-carbon process for recycling the retired lithium ion battery has very important significance.

Currently, the main methods for lithium ion battery recovery include two types of hydrometallurgy and pyrometallurgy, wherein: the hydrometallurgical process generally uses strong acid and strong alkali solutions, thereby generating a large amount of wastewater, and easily causing secondary pollution and environmental management problems; pyrometallurgy also has the problems of high energy consumption, difficulty in removing metal impurities, emission of toxic smoke and the like.

The existing recovery technology based on hydrometallurgy or pyrometallurgy generally carries out evaporation concentration or extraction enrichment on the recovered lithium-containing solution, and then sodium carbonate or phosphoric acid is added to form lithium salt precipitate for separation and recovery. In the practical process, the evaporation and concentration can bring huge energy consumption, and the addition of sodium carbonate or phosphoric acid can increase the additional material cost. In addition, the introduction of phosphate and sodium ions increases the difficulty of separation and purification, resulting in a decrease in recovery rate of lithium, resulting in waste of lithium resources. For the above reasons, there is still a need to develop a more green and efficient process technology for recycling lithium resources of waste lithium ion batteries.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for recovering lithium from waste lithium ion batteries to cooperatively repair lithium iron phosphate materials, namely, under the electrolysis condition, lithium can be removed from waste positive pole pieces of the lithium ion batteries on the positive side, and removed lithium ions are inserted into waste lithium iron phosphate on the negative side to play a role in lithium supplementing and repairing. The method not only can effectively solve the problem of recycling lithium resources of various waste lithium ion battery electrode materials, but also can cooperatively carry out lithium supplementing and repairing of the waste lithium iron phosphate electrode materials, thereby solving the following two problems: (1) The waste lithium ion battery anode materials are various in variety and different in specification, and the recycling process has no problem of universality; (2) At present, the technology for recovering lithium resources from waste lithium ion batteries is complex and has high cost.

The invention adopts the following technical scheme for realizing the purpose:

a method for recovering lithium from waste lithium ion batteries to cooperatively repair lithium iron phosphate materials comprises the following steps:

step 1: discharging and disassembling the retired lithium ion battery to obtain a waste positive electrode plate, soaking the positive electrode plate in dimethyl carbonate (DMC) solvent at normal temperature, and dissolving and removing residual electrolyte in the positive electrode plate; then taking out the positive plate, flushing with deionized water to remove DMC, and obtaining a pretreated positive plate;

step 2: taking the pretreated positive electrode plate obtained in the step 1 as a positive electrode, placing the positive electrode plate in a direct current electrolytic tank, carrying out constant-current electrolysis on a negative electrode by using a waste lithium iron phosphate positive electrode plate pretreated according to the same method as the step 1 in a lithium salt solution of 0.1-2 mol/L by adopting an electrochemical method, removing lithium ions in a positive electrode side electrode plate into the solution under the drive of an electric field, and carrying out reduction and lithium supplementation on a negative electrode side electrode plate to obtain a repaired lithium iron phosphate electrode plate;

step 3: and (3) placing the lithium iron phosphate pole piece repaired in the step (2) in an oven for drying, and effectively separating the electrode material from the aluminum foil current collector because the electrode material and the aluminum foil current collector are already layered at the end of electrolysis. After drying, respectively obtaining aluminum foil and lithium iron phosphate material repaired by lithium supplement, and ball-milling the lithium iron phosphate material repaired by lithium supplement to obtain lithium iron phosphate powder with uniformly dispersed particles;

step 4: and (3) placing the lithium iron phosphate powder obtained in the step (3) in inert atmosphere such as nitrogen or argon for roasting, and obtaining the repairing regenerated lithium iron phosphate positive electrode material.

Further, in the step 1, the waste positive electrode sheet is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium nickel cobalt manganate and lithium nickel cobalt aluminate positive electrode sheet, and preferably is lithium iron phosphate. That is, in the electrolysis of step 2, the positive electrode may be any one of the above-mentioned waste positive electrode sheets, and the negative electrode may be a waste lithium iron phosphate positive electrode sheet.

Further, in the step 1, the soaking time of the positive electrode plate in the DMC solvent is 3-5 h.

Further, in step 2, the lithium salt is one or more of lithium chloride, lithium sulfate, lithium nitrate, lithium acetate and lithium hydroxide, preferably lithium sulfate.

Further, in the step 2, the constant current electrolysis time is 1-24 hours, the reaction temperature is 10-50 ℃, the current range is 1-100 mA, and the voltage range is 0.1-10V.

Further, in the step 3, the drying temperature is 50-100 ℃ and the drying time is 1-24 hours.

Further, in the step 3, the ball milling is carried out at 600-1500 rpm for 1-10 h.

Further, in the step 4, the roasting is to heat up to 200-500 ℃ at a heating rate of 1-10 ℃/min, heat preservation is carried out for 1-12 h, and then the roasting is naturally cooled to room temperature.

According to the method, lithium in the positive electrode material of the waste lithium ion battery is used as a lithium source, and lithium extracted from the waste positive electrode material is supplemented and embedded into the negative side waste lithium iron phosphate material through electric field driving, so that the lithium supplementing and repairing of the waste lithium iron phosphate material are realized. The method comprises the following three steps: firstly, lithium resources in the anode material of the waste lithium ion battery can be selectively removed and effectively recycled; secondly, the waste lithium iron phosphate material can be subjected to lithium supplementing, repairing and regenerating so as to prepare a new lithium iron phosphate electrode material; thirdly, useful materials such as byproduct ferric phosphate, cobalt oxide, manganese oxide and the like after lithium removal can be obtained. Compared with the conventional recovery process of the electrode material of the waste lithium ion battery, the method has the advantages of simple process, environment friendliness, low cost and the like.

Compared with the prior art, the invention has the beneficial effects that:

the invention discloses a method for recovering lithium from waste lithium ion batteries and cooperatively repairing lithium iron phosphate materials, which comprises the steps of preprocessing waste lithium ion positive electrode materials through dissolution of an organic solvent, then driving by an electric field, carrying out lithium removal recovery on the waste lithium ion battery positive electrode materials on the positive electrode side, carrying out electrochemical lithium supplementation on the waste lithium iron phosphate materials on the negative electrode side, and compensating lithium lost by the waste lithium iron phosphate materials in the process of repeated charge and discharge use, so as to repair the electrochemical performance of the lithium iron phosphate positive electrode materials. The method can effectively solve the problem of delithiation recovery of the positive electrode materials of various waste lithium ion batteries while repairing and regenerating the prepared lithium iron phosphate materials, and realize the general recovery of the positive electrode materials in retired lithium ion batteries.

Drawings

Fig. 1 is a process flow diagram of example 1 of the present invention.

Fig. 2 is an XRD pattern of a lithium iron phosphate positive electrode material regenerated by electrochemical lithium supplementation according to example 1 of the present invention.

Fig. 3 is an XRD pattern of iron phosphate obtained by electrochemical delithiation of example 1 of the present invention.

Fig. 4 is a first-turn charge-discharge curve of the button cell prepared by repairing the regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material in example 1 of the present invention at a current density of 0.1C.

Fig. 5 is a graph showing the rate performance of button cells prepared from the regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material recovered in example 1 of the present invention.

Detailed Description

The following describes in detail the examples of the present invention, which are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following examples.

Example 1

As shown in fig. 1, in this embodiment, the regenerated lithium iron phosphate positive electrode material is recovered from the waste lithium iron phosphate battery as follows:

discharging and disassembling a retired lithium iron phosphate battery with the positive electrode material of lithium iron phosphate to obtain a waste lithium iron phosphate positive electrode plate, soaking the positive electrode plate in DMC solvent for 3 hours at normal temperature, and dissolving and removing residual electrolyte in the positive electrode plate. And then taking out the pole piece, and flushing with deionized water to remove DMC, thus obtaining the pretreated positive pole piece.

Two pretreated positive pole pieces are respectively used as a positive pole and a negative pole and are placed in a direct current electrolytic tank. And (3) carrying out constant-current electrolysis in a lithium sulfate solution with the concentration of 1mol/L for 1h by adopting an electrochemical method, wherein the initial current is 10mA, the reaction temperature is 20 ℃, and the voltage is 0.1-3V. Lithium ions in the positive electrode side pole piece are separated and embedded into the solution under the drive of an electric field, and the negative electrode side pole piece is reduced and supplemented with lithium to obtain the repaired lithium iron phosphate pole piece.

And (3) respectively placing the repaired lithium iron phosphate pole piece and the lithium-removed lithium iron phosphate pole piece in a 100 ℃ oven for drying for 12 hours, and respectively obtaining aluminum foil, ferric phosphate and lithium-supplementing repaired lithium iron phosphate material after drying because the electrode material and the aluminum foil of the current collector are layered after the electrolysis is finished. And ball-milling the lithium iron phosphate material repaired by lithium supplement at the rotating speed of 1200rpm for 2 hours to obtain the lithium iron phosphate powder with uniformly dispersed particles.

And (3) placing the lithium iron phosphate powder subjected to electrochemical lithium supplementing and repairing in a nitrogen atmosphere, heating to 300 ℃ at a heating rate of 5 ℃/min, carrying out heat preservation treatment for 6 hours, and finally naturally cooling to room temperature to obtain the repaired and regenerated lithium iron phosphate positive electrode material.

Fig. 2 is an XRD pattern of the lithium iron phosphate positive electrode material recovered and regenerated by electrochemical lithium supplementation in this example, and it can be seen from the figure that the diffraction peak corresponds to the standard card of lithium iron phosphate (JPCDS: 83-2092), and the peak is sharp and no impurity peak appears.

Fig. 3 is an XRD pattern of the iron phosphate obtained by electrochemical delithiation in this example, and it can be seen from the figure that the diffraction peak corresponds to standard card of iron phosphate of isophosphoric manganese iron ore type (JPCDS: 70-1555), and conforms to the crystal structure of the delithiation product of lithium iron phosphate.

The recovered and regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material (in order to obtain the original performance of the waste lithium iron phosphate positive electrode material, the powder scraped off by the pretreated positive electrode sheet is used as the waste lithium iron phosphate positive electrode material) obtained in the embodiment are fully mixed with acetylene black and polyvinylidene fluoride (PVDF) according to the ratio of 8:1:1 (mass ratio), NMP (1-methyl-2-pyrrolidone) is added to be mixed into paste, the paste is uniformly coated on an aluminum foil, the coating thickness is 75 mu m, and the aluminum foil is dried at 80 ℃, rolled and sheared into positive electrode sheets with the diameter of 12mm, and vacuum drying is carried out for standby. A CR2032 button cell is assembled in an argon glove box by taking a metal lithium sheet as a negative electrode and taking a Cellgard2400 type polypropylene film as a diaphragm, and then the cell is subjected to constant voltage constant current charge and discharge test at 25 ℃.

Fig. 4 is a first-cycle charge-discharge curve of the button cell prepared from the regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material at a current density of 0.1C, and it can be seen from the graph that the first-cycle charge-discharge capacity of the regenerated lithium iron phosphate positive electrode material is 119.3mAh/g and 147.0mAh/g, which are obviously higher than 75.5mAh/g and 105.4mAh/g of the waste positive electrode powder respectively.

Fig. 5 is a graph of the rate performance of a button cell prepared from the regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material, and the graph can be seen from the graph: the discharge capacity of the recovered and regenerated lithium iron phosphate positive electrode material at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C is respectively 154.1mAh/g, 151.0mAh/g, 145.5mAh/g, 141.9mAh/g, 134.7mAh/g, 125.5mAh/g and 115.5mAh/g, which are obviously higher than that of the waste positive electrode powder, namely 107.0mAh/g, 105.4mAh/g, 104.04mAh/g, 100.8mAh/g, 97.5mAh/g, 91.1mAh/g and 84.5mAh/g. Electrochemical test results show that electrochemical lithium supplementation can effectively repair the electrochemical performance of the waste lithium iron phosphate positive electrode material.

Example 2

The embodiment recovers regenerated lithium iron phosphate positive electrode materials from waste lithium cobalt oxide batteries and lithium iron phosphate batteries according to the following steps:

discharging and disassembling a retired lithium iron phosphate battery with the anode material of lithium iron phosphate to obtain a waste lithium iron phosphate pole piece, soaking the lithium iron phosphate pole piece in DMC solvent for 3 hours at normal temperature, and dissolving and removing residual electrolyte in the lithium iron phosphate pole piece. And then taking out the lithium iron phosphate pole piece, and flushing with deionized water to remove DMC, thus obtaining the pretreated lithium iron phosphate pole piece.

Discharging and disassembling a retired lithium cobalt oxide battery with a positive electrode material of lithium cobalt oxide to obtain a waste lithium cobalt oxide pole piece, soaking the lithium cobalt oxide pole piece in DMC solvent for 3 hours at normal temperature, and dissolving and removing residual electrolyte in the lithium cobalt oxide pole piece. And then taking out the lithium cobalt oxide pole piece, and flushing with deionized water to remove DMC, thus obtaining the pretreated lithium cobalt oxide pole piece.

The pretreated lithium cobalt oxide pole piece and the pretreated lithium iron phosphate pole piece are respectively used as an anode and a cathode and are placed in a direct current electrolytic tank. And (3) carrying out constant-current electrolysis in a lithium sulfate solution with the concentration of 1mol/L for 1h by adopting an electrochemical method, wherein the initial current is 10mA, the reaction temperature is 20 ℃, and the voltage is 0.1-3V. Lithium ions in the positive electrode side lithium cobalt oxide pole piece are deintercalated into the solution under the drive of an electric field, and the negative electrode side lithium iron phosphate pole piece is subjected to reduction and lithium supplementation to obtain the repaired lithium iron phosphate pole piece.

And (3) respectively placing the repaired lithium iron phosphate pole piece and the cobalt oxide pole piece obtained by lithium removal in a drying oven at 100 ℃ for 12 hours, and respectively obtaining aluminum foil, cobalt oxide and lithium supplementing repaired lithium iron phosphate material after drying because the electrode material and the aluminum foil of the current collector are already layered at the end of electrolysis. Ball milling the lithium iron phosphate material repaired by lithium supplementing at the rotating speed of 1200rpm for 2 hours to obtain lithium iron phosphate powder with uniformly dispersed particles;

and (3) placing the lithium iron phosphate powder repaired by electrochemical lithium supplementation in nitrogen atmosphere for roasting, heating to 300 ℃ at a heating rate of 5 ℃/min, carrying out heat preservation treatment for 6 hours, and finally naturally cooling to room temperature to obtain the repaired and regenerated lithium iron phosphate positive electrode material.

The above description is illustrative of the invention and is not intended to be limiting, but is to be construed as being included within the spirit and scope of the invention.

Claims

1. The method for recovering lithium from waste lithium ion batteries to cooperatively repair lithium iron phosphate materials is characterized by comprising the following steps:

step 1: discharging and disassembling the retired lithium ion battery to obtain a waste positive electrode plate, soaking the positive electrode plate in DMC solvent at normal temperature, and dissolving and removing residual electrolyte in the positive electrode plate; then taking out the positive plate, flushing with deionized water to remove DMC, and obtaining a pretreated positive plate;

step 3: placing the lithium iron phosphate pole piece repaired in the step 2 into an oven for drying to respectively obtain an aluminum foil and a lithium iron phosphate material repaired by lithium supplement, and ball-milling the lithium iron phosphate material repaired by lithium supplement to obtain lithium iron phosphate powder with uniformly dispersed particles;

step 4: and (3) placing the lithium iron phosphate powder obtained in the step (3) in an inert atmosphere for roasting to obtain the regenerated lithium iron phosphate positive electrode material.

2. The method according to claim 1, characterized in that: in the step 1, the waste positive electrode sheet is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium nickel cobalt manganate and lithium nickel cobalt aluminate positive electrode sheet.

3. The method according to claim 1, characterized in that: in the step 1, the soaking time of the positive pole piece in the DMC solvent is 3-5 h.

4. The method according to claim 1, characterized in that: in the step 2, the lithium salt is one or more of lithium chloride, lithium sulfate, lithium nitrate, lithium acetate and lithium hydroxide.

5. The method according to claim 1, characterized in that: in the step 2, the constant current electrolysis time is 1-24 h, the reaction temperature is 10-50 ℃, the current range is 1-100 mA, and the voltage range is 0.1-10V.

6. The method according to claim 1, characterized in that: in the step 3, the drying temperature is 50-100 ℃ and the drying time is 1-24 h.

7. The method according to claim 1, characterized in that: in the step 3, the ball milling is carried out for 1 to 10 hours at the rotating speed of 600 to 1500 rpm.

8. The method according to claim 1, characterized in that: in the step 4, the roasting is to heat up to 200-500 ℃ at a heating rate of 1-10 ℃/min, heat preservation is carried out for 1-12 h, and then the roasting is naturally cooled to room temperature.