Method for room temperature repair and pre-lithiation of waste lithium iron phosphate electrode

Abstract

This invention discloses a room-temperature repair and pre-lithiation method for waste lithium iron phosphate electrodes, relating to the field of lithium battery recycling. The method involves discharging and disassembling waste lithium iron phosphate batteries to obtain positive electrode sheets. After washing and drying with an organic solvent, the intact electrode sheets are directly replenished with lithium at 25°C using either chemical bonding or electrochemical 0V constant-voltage discharge. After washing and drying, regenerated electrode sheets are obtained. The chemical method involves attaching a lithium metal sheet with electrolyte droplets to the positive electrode sheet and holding it for 2-30 minutes. The electrochemical method involves using the electrode sheet as the positive electrode and lithium metal as the negative electrode in an electrolyte solution with a 0V constant-voltage discharge for 1-30 minutes. This invention eliminates the need for electrode breakage, high temperatures, and additional reducing agents, achieving direct lithium replenishment and repair at the electrode layer and forming a lithium-rich phase. This effectively compensates for the loss of active lithium in the first cycle of pouch batteries. The specific capacity and cycle performance of the regenerated electrode sheets are superior to commercial materials. The process is simple, has a short cycle time, and can be directly used for battery assembly, making it suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling and regeneration, specifically to a room temperature repair and pre-lithiation method for waste lithium iron phosphate electrodes. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage industries, lithium iron phosphate (LFP) batteries have become the mainstream technology due to their high safety, long cycle life, and low cost. Industry forecasts predict that the first large-scale retirement wave will occur between 2025 and 2030, with the cumulative retirement volume expected to exceed one million tons. How to efficiently and environmentally dispose of used LFP batteries has become a key bottleneck for the sustainable development of the industry.

[0003] The current mainstream pyrometallurgical recovery (high-temperature smelting to extract metals) and hydrometallurgical recovery (acid leaching to separate metal ions) have obvious drawbacks: pyrometallurgical recovery requires temperatures above 1200℃, resulting in high energy consumption; hydrometallurgical recovery generates a large amount of acid-containing waste liquid, resulting in high treatment costs. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a room temperature repair and pre-lithiation method for waste lithium iron phosphate electrodes.

[0005] The technical solution of the present invention is as follows: A room temperature repair and pre-lithiation method for waste lithium iron phosphate electrodes involves first discharging and disassembling the waste lithium iron phosphate batteries to obtain positive electrode sheets. After washing and drying with an organic solvent, the positive electrode sheets are directly lithium-added at 20-30°C using chemical bonding or electrochemical 0V constant voltage discharge. After washing and drying, regenerated electrode sheets are obtained.

[0006] Preferably, the chemically applied lithium replenishment involves attaching a positive electrode to a lithium metal sheet containing electrolyte and maintaining it for 2-30 minutes.

[0007] Preferably, the electrochemical method involves discharging at a constant voltage of 0V in an electrolyte for 1-30 minutes using a positive electrode sheet as the positive electrode and lithium metal as the negative electrode.

[0008] Preferably, the organic solvent is DMC or DEC.

[0009] Preferably, in the chemical patch lithium replenishment method, the mass ratio of electrolyte to positive electrode active material is 5-9 μL / mg.

[0010] Preferably, in the chemical bonding lithium replenishment method, the area of ​​the lithium metal sheet is the same as the area of ​​the positive electrode sheet, and the mass ratio of the two is 8-12:1.

[0011] Preferably, the electrolyte is LB-006 electrolyte.

[0012] The beneficial effects of this invention are: this invention does not require broken electrode sheets, high temperature, or additional reducing agents, and can directly achieve lithium replenishment and repair at the electrode layer to form a lithium-rich phase, effectively compensating for the loss of active lithium in the first cycle of soft-pack batteries. The specific capacity and cycle performance of the regenerated electrode sheets are superior to those of commercial materials. The process is simple, the cycle is short, and it can be directly used for battery assembly, making it suitable for industrial production. Attached Figure Description

[0013] Figure 1 The first charge-discharge curves are for a waste lithium iron phosphate electrode (SLFP), a lithium iron phosphate electrode after pre-lithiation in Example 1 (PLFP), and a commercial lithium iron phosphate electrode (CLFP).

[0014] Figure 2 The first charge-discharge curves are shown for the waste lithium iron phosphate electrode (SLFP), the pre-lithiated lithium iron phosphate electrode (PLFP) of Example 2, and the commercial lithium iron phosphate electrode (CLFP). Detailed Implementation

[0015] A room temperature repair and pre-lithiation method for waste lithium iron phosphate electrodes involves first discharging and disassembling the waste lithium iron phosphate batteries to obtain positive electrode sheets. After washing and drying with an organic solvent, the positive electrode sheets are directly lithium-added at room temperature of 20-30°C using chemical bonding or electrochemical 0V constant voltage discharge. After washing and drying, regenerated electrode sheets are obtained.

[0016] Specifically, the chemically applied lithium replenishment involves attaching the positive electrode to a lithium metal sheet soaked in electrolyte and maintaining it for 2-30 minutes, which can be 2, 4, 6, 8, 10, 12, 15, 20, 25, or 30 minutes. The lithium metal is then brought into contact with the electrolyte-wetted SLFP electrode, and under the drive of the potential difference, the Li metal ionizes to produce Li. + And electrons, replenishing the missing active Li in SLFP + As contact time increases, SLFP transforms from a lithium-deficient phase (Li). 0.74 FePO4 transforms into a lithiation phase (LiFePO4, RLFP), and then into a lithium-rich phase (Li). 1.15 FePO4, PLFP).

[0017] Specifically, the electrochemical method involves using a positive electrode as the positive electrode and lithium metal as the negative electrode, followed by constant voltage discharge at 0V in an electrolyte for 1-30 minutes, which can be 1, 3, 5, 7, 9, 15, 20, 25, or 30 minutes. Preferably, lithium metal is used as the negative electrode, and waste lithium iron phosphate electrode is used as the positive electrode. The electrolyte is 1M LiPF6 in DEC:EC = 1:1 wt%. After assembling the battery, it is discharged at 0V for 1-30 minutes, causing lithium ions from the negative electrode to embed into the waste lithium iron phosphate electrode under potential-driven conditions.

[0018] Specifically, the organic solvent is DMC or DEC.

[0019] Specifically, in the method of chemically applied lithium replenishment, the mass ratio of electrolyte to positive electrode active material is 5-9 μL / mg.

[0020] Specifically, in the chemical bonding lithium replenishment method, the area of ​​the lithium metal sheet is the same as the area of ​​the positive electrode sheet, and the mass ratio of the two is 8-12:1.

[0021] Specifically, the electrolyte is LB-006 electrolyte.

[0022] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0023] DMC: dimethyl carbonate; DEC: ethylene carbonate.

[0024] LB-006 electrolyte is a secondary electrolyte composed of a 1.0M LiPF6 in EC:DEC=1:1 Wt% formulation.

[0025] Example 1 The direct regeneration of waste lithium iron phosphate electrodes to obtain recycled lithium iron phosphate electrodes includes the following steps: (1) Collection of positive electrode sheets: Completely discharge and disassemble the waste lithium-ion batteries, wash away the residual electrolyte on the surface of the waste lithium iron phosphate electrode sheets with DMC / DEC solution, and dry to obtain waste lithium iron phosphate positive electrode sheets; (2) Chemical regeneration: A suitable amount of electrolyte (LB-006) was added to the lithium metal sheet, and the waste lithium iron phosphate positive electrode sheet was attached to the lithium metal sheet with the electrolyte. The mass ratio of electrolyte to active material of lithium iron phosphate positive electrode sheet was 7 μL / mg, the area of ​​lithium metal sheet was the same as that of waste lithium iron phosphate electrode sheet, the mass ratio of the two was 10:1, and the attachment time was 6 minutes. After regeneration, the regenerated lithium iron phosphate positive electrode sheet was cleaned with DMC solvent to remove the residual electrolyte on the surface, and then the positive electrode sheet was dried at room temperature for 2 hours to obtain the pre-lithiated regenerated lithium iron phosphate electrode. All the above operations were carried out in a glove box filled with Ar gas.

[0026] Example 2 The direct regeneration of waste lithium iron phosphate electrodes to obtain recycled lithium iron phosphate electrodes includes the following steps: (1) Collection of positive electrode sheets: Completely discharge and disassemble the waste lithium-ion batteries, wash away the residual electrolyte on the surface of the waste lithium iron phosphate electrode sheets with DMC / DEC solution, and dry to obtain waste lithium iron phosphate positive electrode sheets; (2) Electrochemical regeneration: The electrochemical method involves assembling a battery using waste lithium iron phosphate positive electrode sheets as the positive electrode and lithium metal as the negative electrode in LB-006 electrolyte, and then maintaining a constant voltage of 0V for 7 minutes. After regeneration, the regenerated lithium iron phosphate electrode sheets are cleaned with DMC solvent to remove residual electrolyte from the surface, and then the electrode sheets are dried at room temperature for 2 hours to obtain a pre-lithiated regenerated lithium iron phosphate electrode. All the above operations are carried out in a glove box filled with Ar gas.

[0027] The half-cells (SLFP) assembled from the samples of Examples 1 and 2, as well as the waste lithium iron phosphate electrode (SLFP) and the commercial lithium iron phosphate electrode (CLFP), were subjected to electrode performance testing. The test results are shown in [Figure 1]. Figure 1 and Figure 2 .

[0028] from Figure 1 and Figure 2 It can be seen that, compared with the waste lithium iron phosphate cathode, the first-cycle charge specific capacity of the recycled pre-lithiated lithium iron phosphate cathode sheets in Examples 1 and 2 has been recovered. Furthermore, compared with commercial lithium iron phosphate, the first-cycle charge specific capacity of the pre-lithiated lithium iron phosphate cathode is higher, which is due to the Li ionization of lithium metal. + While filling lithium vacancies, lithium iron phosphate is also formed into a lithium-rich phase, which can release excess capacity in the first cycle, improve the energy density of the battery, and realize the first electrochemical direct lithium replenishment on waste lithium iron phosphate cathode sheets.

[0029] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0030] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A room temperature remediation and pre-lithiation method for waste lithium iron phosphate electrodes, characterized in that, First, the waste lithium iron phosphate batteries are discharged and disassembled to obtain the positive electrode sheet. After being washed and dried with an organic solvent, the positive electrode sheet is directly replenished with lithium by chemical bonding or electrochemical 0V constant voltage discharge at 20-30℃. After washing and drying, the regenerated electrode sheet is obtained.

2. The method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 1, characterized in that, The chemical patching for lithium replenishment involves attaching the positive electrode to a lithium metal sheet containing electrolyte and leaving it for 2-30 minutes.

3. The method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 1, characterized in that, The electrochemical method involves using a positive electrode as the positive electrode and lithium metal as the negative electrode to discharge at a constant voltage of 0V in an electrolyte for 1-30 minutes.

4. The method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 1, characterized in that, The organic solvent is DMC or DEC.

5. The method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 2, characterized in that, In the aforementioned chemical patch lithium replenishment method, the mass ratio of electrolyte to positive electrode active material is 5-9 μL / mg.

6. The method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 2, characterized in that, In the aforementioned chemical bonding lithium replenishment method, the area of ​​the lithium metal sheet is the same as the area of ​​the positive electrode sheet, and the mass ratio of the two is 8-12:

1.

7. A method for room temperature remediation and pre-lithiation of waste lithium iron phosphate electrodes according to claim 2 or 3, characterized in that, The electrolyte is LB-006 electrolyte.

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