Method for stripping positive electrode material of waste lithium ion battery by using tartaric acid under assistance of ultrasonic waves

Abstract

The invention belongs to the technical field of retired power battery recovery, and particularly relates to a method for stripping a positive electrode material of a waste lithium ion battery by ultrasonic-assisted tartaric acid. The method comprises the following steps: firstly, preparing a tartaric acid solution with a set concentration at normal temperature, adding the prepared tartaric acid solution into an ultrasonic cleaning instrument, then immersing the to-be-separated positive electrode material containing the aluminum foil into the tartaric acid solution, carrying out ultrasonic cleaning, and carrying out solid-liquid separation to obtain the aluminum foil and the positive electrode material. Tartaric acid is non-toxic and low in cost, active materials can be stripped basically without damage, and harmless degradation of PVDF can be achieved. According to the method, the positive electrode material and the aluminum foil can be efficiently separated, the two parts of materials can be further treated and recycled respectively, the loss of valuable components is reduced, and the method has important practical significance for realizing resource regeneration and environmental protection of the waste lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of retired power battery recycling, and in particular relates to a method for ultrasonically assisted tartaric acid stripping of positive electrode materials of waste lithium-ion batteries. Background Art

[0002] Waste lithium-ion batteries (LIBs) play a vital role in modern technology and are widely used in portable electronic products, electric vehicles, and power storage devices. However, with the popularity and age of lithium-ion batteries, the number of discarded batteries has also increased rapidly. It is predicted that the number of discarded LIBs worldwide will exceed 1,100 tons in 2030. Therefore, the recycling and resource regeneration of LIBs are of great significance to environmental protection and sustainable development.

[0003] In the recycling process, the separation of positive electrode materials and aluminum foil is a key link. Polyvinylidene fluoride (PVDF), as the main binder of positive electrode materials, has excellent chemical stability and mechanical strength, but it also makes it difficult to separate positive electrode materials from aluminum foil by simple mechanical methods. The existing technology for stripping positive electrode materials and aluminum foil of waste lithium-ion batteries still has many shortcomings and limitations in practical applications. For example, the high-temperature heat treatment method releases toxic hydrogen fluoride (HF) gas by calcining the positive electrode at 500°C to 600°C to decompose PVDF, causing air pollution and equipment corrosion; the chemical dissolution method uses strong acid / strong base to separate positive electrode materials, which not only produces a large amount of strong base / acid waste liquid, but also causes the loss of aluminum foil; the organic solvent produced by solvent dissolution of PVDF to separate positive electrode materials and aluminum foil is volatile and toxic, and the recycling cost is high.

[0004] In the prior art, Guo Yafeng et al. used ultrasound to assist strong polar solvents (DMAc, NMP and DMF) to separate positive electrode materials and aluminum foil. However, these strong polar solvents are expensive and have certain toxicity, which will cause harm to the environment. In addition, the ultrasonic time in this method is too long, which will destroy the integrity of the aluminum foil and is not conducive to regeneration and recycling (Guo Yafeng, Xia Zhidong, Mao Qianjin, et al. Ultrasonic assisted treatment to recover positive electrode materials of lithium-ion batteries [J]. Electronic Components and Materials, 2007, 26 (5): 3). Chen X et al. used ultrasound to assist Fenton's reagent to generate hydroxyl radicals to remove polyvinylidene fluoride in the battery, but Fenton's reagent is a strong oxidant and contains Fe 2+, which will affect the stripping of the positive electrode material and the aluminum foil. The stripping rate in this method is 97%, and will affect the purity of the aluminum foil, making the purity of the aluminum foil lower than 70% (Chen X, Li S, Wang Y, et al. Recycling of LiFePO4 cathode materials from spent lithium-ion batteries through ultrasound-assisted Fentonreaction and lithium compensation[J]. Waste Management, 2021, 136: 67-75.).

[0005] Therefore, providing a safe, non-toxic, low-cost, and efficient method for separating positive electrode materials and aluminum foil is of great practical significance for achieving resource recycling of waste lithium-ion batteries and environmental protection. Summary of the invention

[0006] In order to solve the above technical problems, one of the objectives of the present invention is to provide a method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials comprises the following steps: preparing a tartaric acid solution with a mass fraction of 1 to 50% at room temperature, adding the prepared tartaric acid solution into an ultrasonic cleaning instrument, and then immersing the positive electrode material containing aluminum foil to be separated into the tartaric acid solution. After ultrasonic cleaning, the separated aluminum foil and positive electrode material are obtained.

[0009] Preferably, the positive electrode material containing aluminum foil to be separated is first broken into fragments with an average diameter of 1 to 2 cm before immersion.

[0010] Preferably, the cleaning procedure is: first heat the system temperature to 30-45° C., turn on the ultrasonic cleaning instrument, the ultrasonic power is 130 W, the ultrasonic frequency is 45 KHz, and ultrasonic cleaning is performed until the positive electrode material is peeled off from the surface of the aluminum foil.

[0011] Preferably, the ultrasonic cleaning time is 40 to 120 seconds.

[0012] Preferably, the mass fraction of the tartaric acid solution is 30%, the system temperature is heated to 45°C, and ultrasonic cleaning is performed for 60 seconds.

[0013] Preferably, after the positive electrode material is peeled off from the surface of the aluminum foil, the aluminum foil is taken out, cleaned, dried and recovered; the remaining part is subjected to solid-liquid separation, and the solid obtained by separation is the positive electrode material, which is cleaned, dried and recovered.

[0014] The beneficial effects of the present invention are:

[0015] The present invention uses tartaric acid to strip the positive electrode material. The principle is that tartaric acid enhances the permeability of carboxylic acid with the assistance of ultrasound, so that tartaric acid and the surface of aluminum foil (Al 2 O 3 The PVDF / positive electrode material layer on the aluminum foil surface reacts with the positive electrode material layer to completely desorb the PVDF / positive electrode material layer on the aluminum foil surface, thus separating the aluminum foil and the positive electrode material. 3+ Complexation occurs to form a passivation layer, protecting the aluminum foil from further corrosion by tartaric acid and reducing subsequent interference from impurity ions. On the other hand, the experimental results show that PVDF itself, as a fluorine-containing dielectric material, can undergo an interfacial contact electrocatalytic reaction with water and oxygen molecules under appropriate ultrasonic cavitation by controlling the ultrasonic power and frequency, achieving in-situ synthesis of the reducing component hydrogen peroxide, and then generating highly active free radicals to degrade PVDF, ultimately achieving separation and purification of the positive electrode material.

[0016] The technology of the present invention does not need to use any polluting and toxic organic solvents. Tartaric acid is non-toxic and low-cost, which greatly reduces environmental hazards and industrial production costs. In addition, this technology can not only strip the active material without damage, but also achieve harmless degradation of PVDF, which cannot be achieved by organic solvent dissolution treatment alone. In this method, ultrasound only takes about 40 seconds to achieve a positive electrode material stripping rate of more than 99%, and the aluminum foil is intact and basically intact, which does not affect its regeneration and use.

[0017] Since this method uses tartaric acid to react with the alumina layer in advance, the positive electrode material is completely stripped. 3+ After leaching, tartaric acid immediately forms a complex passivation layer with it, protecting the aluminum foil from further corrosion, which not only improves the stripping rate of the positive electrode material, but also improves the purity of the aluminum foil. Experiments show that the positive electrode material stripping rate of this method is over 99.5%, and the purity of the aluminum foil is higher than 99%. The technical effect is far better than other existing recycling methods.

[0018] The method of the present invention can efficiently separate the positive electrode material and the aluminum foil, and the two parts of the material can be further processed and recycled respectively, reducing the loss of valuable components, and has important practical significance for realizing the resource recycling of waste lithium-ion batteries and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a comparison of the disassembled positive electrode sheet before and after processing;

[0020] Figure 2The sample diagram of ultrasonic recovery of positive electrode sheets of Example 1 and Comparative Example 1, the leftmost side of the figure is Comparative Example 1 (the tartaric acid concentration is 0), and the other concentrations are 1%, 5%, 10%, 20%, 30%, and 40% by mass from left to right;

[0021] Figure 3 This is a sample picture of the positive electrode sheet recovered by ultrasonic wave in Example 2;

[0022] Figure 4 is the stripping rate of valuable metals in the positive electrode material and the corrosion rate of the aluminum foil in Example 1;

[0023] Table 1 compares the stripping rate of valuable metals in the positive electrode material and the recovery rate of aluminum foil at 10%, 20% and 30% tartaric acid mass fractions in Example 2. DETAILED DESCRIPTION

[0024] Unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art.

[0025] The technical solution of the present invention is described in more detail below in conjunction with the embodiments:

[0026] Example 1

[0027] Separation experiments

[0028] Here are the steps:

[0029] Step 1: After discharging the waste lithium battery, place it in a glove box filled with nitrogen and disassemble it. Separate the positive electrode sheet, diaphragm, and negative electrode sheet. Get the positive electrode sheet containing aluminum foil and cut it into positive electrode discs with a diameter of 1.5 cm. Figure 1 ;

[0030] Step 2: Add a set amount of tartaric acid into deionized water at room temperature, stir for 10 minutes at a stirring speed of 150 rpm, and prepare tartaric acid solutions with mass fractions of 1%, 5%, 10%, 20%, 30% and 40% respectively;

[0031] Step 3: Heat the ultrasonic cleaning instrument to the desired stripping temperature of 30°C;

[0032] Step 4: Mix the disassembled waste lithium battery positive electrode sheet with the prepared tartaric acid solution in a mass ratio of 0.05:1;

[0033] Step 5: placing the above mixed material in an ultrasonic cleaner and ultrasonicating for 40 seconds at 30° C., an ultrasonic frequency of 45 KHz, and an ultrasonic power of 130 W;

[0034] Step 6: Take out the aluminum foil from the mixed material, rinse it with clean water, and dry it for recycling;

[0035] Step 7: Use centrifugation to separate the remaining solid and solution in the above mixed solution. The solid is the positive electrode material. The positive electrode material is washed and dried for recovery.

[0036] Example 2

[0037] The specific experimental steps of this example are the same as those of Example 1, except that tartaric acid solutions with mass fractions of 5%, 10%, 20%, 30%, 40% and 50% were used and ultrasonicated at 45° C. for 60 s.

[0038] Comparative Example 1

[0039] The specific experimental steps of this embodiment are the same as those of embodiment 1, except that a tartaric acid solution with a mass fraction of 0%, i.e., pure water, is used.

[0040] The aluminum foil, positive electrode material and the remaining soluble acid collected in Examples 1-2 and Comparative Example 1 were immersed in 6M hydrochloric acid solution respectively, and the concentration of valuable metal ions therein was tested by ICP to calculate the stripping rate (Li + ,Co 3+ ) and aluminum foil corrosion rate (Al 3+ ).

[0041] Figure 2 The results of Example 1 and Comparative Example 1 are shown. It can be seen that the positive electrode material and the aluminum foil cleaned by ultrasonic cleaning under the condition of tartaric acid have different degrees of separation, among which the separation efficiency of 10% and 20% is the best.

[0042] Figure 3 The treatment results of Example 2 and Comparative Example 1 are shown. Figure 2 By comparison, it can be seen that under the same tartaric acid concentration condition, increasing the ultrasonic temperature and ultrasonic time improves the separation efficiency of aluminum foil and positive electrode material. The calculation results of the stripping rate of valuable metal elements and the recovery rate of aluminum foil in Example 2 are shown in Table 1, and the calculation results of the stripping rate of valuable metal elements and the corrosion rate of aluminum foil in Example 1 and Comparative Example 1 are shown in Table 2. Figure 4 Wherein, recovery rate = (1-corrosion rate) × 100%.

[0043] Table 1 Stripping rate of valuable metal ions in Example 2

[0044]

[0045] It can be seen that the purity of the aluminum foil recovered under the condition of 30% mass fraction of tartaric acid is as high as 99%, and the recovery rate of valuable metals is greater than 99.5%.

[0046] This recycling method uses environmentally friendly and low-cost tartaric acid solution, which can quickly strip the active material without damage under low-temperature ultrasonic conditions. Experiments show that the positive electrode material stripping rate of this method is more than 99.5%, and the aluminum foil recovery rate is higher than 99%. The technical effect is far better than other existing recycling methods, and it has important practical significance for realizing the resource recycling of waste lithium-ion batteries and environmental protection.

[0047] The above are only preferred practical examples of the present invention and are not intended to limit the invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials, characterized in that: A tartaric acid solution with a mass fraction of 1 to 50% is prepared at room temperature, and the prepared tartaric acid solution is added into an ultrasonic cleaning instrument, and then the positive electrode material containing aluminum foil to be separated is immersed in the tartaric acid solution, and after ultrasonic cleaning, the separated aluminum foil and positive electrode material are obtained.

2. The method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials according to claim 1, characterized in that: The positive electrode material containing aluminum foil to be separated is first broken into fragments with an average diameter of 1 to 2 cm before being soaked.

3. The method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials according to claim 1, characterized in that: The cleaning procedure is as follows: firstly, the system temperature is heated to 30-45° C., an ultrasonic cleaning instrument is turned on, the ultrasonic power is 130 W, the ultrasonic frequency is 45 KHz, and ultrasonic cleaning is performed until the positive electrode material is peeled off from the surface of the aluminum foil.

4. The method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials according to claim 3, characterized in that: The ultrasonic cleaning time is 40 to 120 seconds.

5. The method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials according to claim 4, characterized in that: The mass fraction of the tartaric acid solution is 30%, the system temperature is heated to 45° C., and ultrasonic cleaning is performed for 60 seconds.

6. A method for ultrasonically assisted tartaric acid stripping of waste lithium-ion battery positive electrode materials according to any one of claims 1 to 5, characterized in that: After the positive electrode material is peeled off from the surface of the aluminum foil, the aluminum foil is taken out, cleaned, dried and recovered; the remaining part is subjected to solid-liquid separation, and the separated solid is the positive electrode material, which is cleaned, dried and recovered.

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