CN116789150A - Method for removing organic fluorine in lithium ion positive electrode material - Google Patents

Abstract

The invention relates to the technical field of harmless treatment of waste lithium-ion batteries, and specifically relates to a method for removing organic fluorine from lithium-ion cathode materials; the method for removing organic fluorine from lithium-ion cathode materials includes the following steps: Obtaining waste lithium-ion batteries The positive electrode sheet is crushed and screened to obtain positive electrode material; the obtained positive electrode material is mixed with alkaline metal hydroxide and then roasted anaerobically; the product after anaerobic roasting is washed and filtered. The present invention uses alkaline metal hydroxide as a catalyst and capture agent to realize the thermal catalytic removal and solidification separation of organic fluorine in the lithium ion battery cathode material in one step, which not only effectively removes the organic fluorine binder, but also facilitates the removal of the cathode material. Resource utilization, while effectively avoiding the potential secondary environmental pollution risks of organic fluorine. This method relies on heat treatment technology that is widely used in industry, is simple to operate, easy to apply on a large scale, and has broad industrial application potential.

Description

A method for removing organic fluorine from lithium ion cathode materials

Technical field

The present invention relates to the technical field of harmless treatment of waste lithium-ion batteries, and in particular to a method for removing organic fluorine in lithium-ion positive electrode materials.

Background technique

With the rapid development of the new energy vehicle industry, my country's new energy vehicle sales increased to 3.521 million units in 2021, ranking first in the world for 7 consecutive years. New energy vehicles have become my country's green and low-carbon strategic industry. As the core component of new energy vehicles, power batteries account for more than 40% of the total vehicle cost. At present, because ternary power lithium-ion batteries consume a large amount of rare and precious resources such as lithium, cobalt, and nickel, my country's external dependence on such resources exceeds 80%, seriously affecting the national security of my country's new energy automobile industry. Therefore, recycling strategic metals such as lithium, cobalt, and nickel in used power batteries can effectively alleviate the dependence on external resources and complete the key chain of the internal cycle of my country's new energy automobile industry. At present, the treatment and disposal of used lithium-ion battery cathode materials has become a hot topic in resource utilization.

According to the "White Paper on the Development of China's Waste Li-ion Battery Recycling, Dismantling and Echelon Utilization Industry (2022)", China's theoretical waste power battery recycling volume in 2021 will be 294,000 tons. For the recycling of waste power batteries, the industry uses a combination of methods such as electrified crushing and physical separation to quickly dissociate battery components and enrich waste cathode materials for resource utilization. Among them, the obtained waste cathode material is tightly wrapped with an organic fluorine binder such as polyvinylidene fluoride (PVDF). Because PVDF has excellent mechanical strength, resistance to ultraviolet radiation, chemical stability and anti-aging properties, it is difficult to be decomposed by acids, alkalis, strong oxidants or halogens, which is seriously detrimental to the resource utilization of waste cathode materials. In order to achieve efficient utilization of waste cathode materials, the PVDF binder needs to be removed first. At the same time, improper handling may cause serious secondary fluorine pollution. Therefore, how to remove PVDF economically, efficiently and environmentally friendly has an important prerequisite impact on the resource utilization of waste cathode materials.

Contents of the invention

The object of the present invention is to overcome the above-mentioned shortcomings in the prior art and provide a method for removing organic fluorine in lithium ion cathode materials.

In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

A method for removing organic fluorine from lithium ion cathode materials, including the following steps:

Obtain positive electrode sheets from used lithium-ion batteries;

Crush and screen the positive electrode sheets to obtain positive electrode materials;

Mix the obtained cathode material with alkaline metal hydroxide and then perform oxygen-free roasting;

The product after anaerobic roasting is washed and filtered with water to separate the fluoride salt and the cathode material for removing organic fluorine.

The method provided by the invention specifically relates to a method for removing organic fluorine in lithium ion cathode materials, and in particular to a method for catalytically pyrolyzing fluorine-containing organic matter in the cathode material into inorganic fluorine and solidifying it in situ into fluoride salts, wherein, The organic fluorine in the cathode material refers to fluorine-containing organic matter such as polyvinylidene fluoride (PVDF), and the cathode material is separated and enriched by crushing and screening the cathode sheets of used lithium-ion batteries. get;

At present, there are many methods for treating organic fluorine in lithium-ion battery cathode materials, such as the organic solvent/molten salt method, which uses the solubility of organic fluorine in the organic phase or molten salt phase to dissolve and remove it. However, the complex organic fluorine after treatment The treatment of phase/molten salt phase has become a new problem; such as direct pyrolysis method, under high-temperature roasting, organic fluorine is cracked into fugitive products such as hydrogen fluoride, vinyl fluoride, trifluorobenzene, etc., which will cause serious secondary pollution.

In the present invention, the obtained cathode material is mixed with an alkaline metal hydroxide and then subjected to an oxygen-free roasting treatment. The organic fluorine in the cathode material is thermally catalytically converted into inorganic fluorine and solidified in situ into a fluoride salt, thereby achieving the The organic fluorine in the cathode material is removed;

Specifically, alkaline metal hydroxide melts under high temperature conditions and reacts with organic fluorine to play a catalytic role, promoting the breakage of C-F bonds to generate inorganic fluorine products such as HF. Then, the alkaline metal hydroxide converts inorganic fluorine products such as HF into The fluorine product is captured and eventually a neutralization reaction occurs. The present invention uses alkaline metal hydroxide as a catalyst and capture agent to realize the thermal catalytic removal and solidification separation of organic fluorine in the lithium ion battery cathode material in one step, which not only effectively removes the organic fluorine binder, but also facilitates the removal of the cathode material. Resource utilization, while effectively avoiding the potential secondary environmental pollution risks of organic fluorine. This method relies on heat treatment technology that is widely used in industry, is simple to operate, easy to apply on a large scale, and has broad industrial application potential.

In a more preferred embodiment, the crushing speed is 1000-2000 rpm, and the crushing time is 5-30 minutes.

In a more preferred embodiment, the mesh size of the screening is greater than 100 mesh.

In a more preferred embodiment, the cathode material of the lithium-ion battery is one or more of lithium cobalt oxide, ternary lithium, lithium manganate, lithium titanate and lithium iron phosphate.

In a more preferred embodiment, the alkaline metal hydroxide is one or a mixture of sodium hydroxide and potassium hydroxide.

In a more preferred embodiment, the mass ratio of the mixture of the positive electrode material and the alkaline metal hydroxide is 100:20-5; since the added alkaline metal hydroxide is to thermally catalytically convert organic fluorine into inorganic Fluorine is cured in situ into fluoride salt, and its dosage should be controlled at 5%-20%. If the addition ratio of alkaline metal hydroxide is too low, the catalytic and curing effects will be poor; if it is too high, it will affect the subsequent recovery of metal elements in the cathode material.

In a more preferred embodiment, the reaction temperature of the oxygen-free roasting is 300-500°C, and the reaction time of the oxygen-free roasting is 0.5-2h.

In a more preferred embodiment, the anaerobic roasting is performed under the condition of a nitrogen/argon flow rate of 50-100 ml/min.

In a more preferred embodiment, the oxygen-free roasting is performed under a vacuum degree of less than 1000 Pa.

In a more preferred embodiment, the solid-to-liquid ratio used for the water washing and filtration is 100-200g/L, and the time is 30 minutes.

To sum up, this application includes at least one of the following beneficial technical effects:

(1) The thermal catalytic treatment technology used can effectively improve the removal efficiency of organic fluorine, reduce the reaction energy barrier, and guide the thermal catalytic conversion of organic fluorine into inorganic fluorine, which is beneficial to the solidification of pollution;

(2) Using alkaline metal hydroxide as a catalyst and capture agent, the directional converted inorganic fluorine can be captured in situ and solidified into fluoride salt to avoid fluorine-containing pyrolysis products from escaping and causing secondary pollution.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other beneficial effects of the present invention may be realized and obtained by the structure particularly pointed out in the specification, claims and drawings.

Description of the drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts; in the following description, the positional relationships described in the drawings, Unless otherwise specified, the directions of the components in the illustrations are used as the basis.

Figure 1 is a process road map of the method for removing organic fluorine in lithium ion cathode materials according to the present invention;

Figure 2 is an XPS image of the C/F elements in the lithium-ion battery cathode material before and after the thermal catalytic technology treatment proposed by the present invention;

Figure 3 is an XRD pattern of the fluoride salt (fluoride salt) separated by the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, not all of them; the technical features designed in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

In the description of the present invention, it should be noted that all terms (including technical terms and scientific terms) used in the present invention have the same meaning as commonly understood by those of ordinary skill in the field to which the present invention belongs, and cannot be understood as being a definition of the present invention. Limitations of the Invention; It should be further understood that the terms used in the present invention should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense. , unless explicitly so defined in the present invention.

The technical solutions of the present invention will be further illustrated and described below through specific examples. However, the protection scope of the present invention is not limited to this.

Example 1

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:10, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 91.23%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

Example 2

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:10, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 400°C, and the reaction time to 1 hour.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 88.56%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

Example 3

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:10, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 300°C, and the reaction time to 2 hours.

3. The residue after the reaction was washed and filtered to obtain the positive electrode material and sodium fluoride solution respectively. The final fluorine fixation rate was 51.04%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes. Compared with other implementations, For example, in this embodiment, due to the lower reaction temperature, the fluorine fixation rate decreases.

Example 4

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:5, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 67.81%. The solid-liquid ratio used in the water washing and filtration was 200g/L and the time was 30 minutes. Compared with other implementations, For example, in this embodiment, the dosage ratio of sodium hydroxide is relatively low, so the fluorine fixation rate decreases.

Example 5

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:20, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 92.54%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

Example 6

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and potassium hydroxide at a mass ratio of 100:20, and then perform oxygen-free roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 90.07%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

Example 7

This embodiment provides a method for removing organic fluorine from lithium ion cathode materials, as shown in Figure 1, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material with the sodium hydroxide/potassium hydroxide mixture (mass ratio of sodium hydroxide and potassium hydroxide 1:1) at a mass ratio of 100:10, and then perform anaerobic roasting. Control the nitrogen flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 93.11%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

It should be noted that the specific parameters or some commonly used reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, and are not limitations thereof; those skilled in the art, within the concept and protection scope of the present invention, Adaptable adjustments are possible. In addition, unless otherwise specified, the raw materials used may also be conventional commercially available products in the art, or may be prepared by conventional methods in the art.

Comparative example 1

This comparative example provides a method for removing organic fluorine from lithium ion cathode materials, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and sodium hydroxide at a mass ratio of 100:1, and then perform oxygen-free roasting. Control the argon flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 500°C, and the reaction time to 0.5h.

3. The reaction residue was washed and filtered to obtain the cathode material and sodium fluoride solution respectively. The final fluorine fixation rate was 21.23%. The solid-liquid ratio used for water washing and filtration was 200g/L and the time was 30 minutes.

4. Because the amount of alkaline metal hydroxide used is too low, the removal and solidification effect of organic fluorine is not good, and the fluoride salt is not effectively obtained.

If the ratio is too high (that is, more than 100:20), the fluoride fixation rate will become stable, that is, it will start to level off after reaching 93%. Continuing to increase the dosage of sodium hydroxide/potassium hydroxide will have no significant impact on the increase in the fluorine fixation rate. , therefore, the optimal ratio range is below 100:5-20.

Comparative example 2

This comparative example provides a method for removing organic fluorine from lithium ion cathode materials, including the following steps:

1. Disassemble the used lithium-ion battery to obtain the positive electrode sheet, then crush the positive electrode sheet at 1500 rpm for 10 minutes, and then undergo multi-stage screening to obtain the positive electrode material powder (>100 mesh);

2. Evenly mix the obtained cathode material and calcium hydroxide at a mass ratio of 100:10, and then perform oxygen-free roasting. Control the argon flow rate to 50 ml/min, the heating rate to 10°C/min, the reaction temperature to 300°C, and the reaction time to 2 hours.

3. Wash and filter the residue after the reaction to obtain the positive electrode material and sodium fluoride solution respectively. The final fluorine fixation rate is 0%. The washing and filtration conditions are: solid-liquid ratio 200g/L, time 30 minutes.

4. Since the alkaline metal hydroxide used is calcium hydroxide, calcium hydroxide affects the catalytic and fluorine fixation effects due to its high melting and boiling point.

Figure 2 is an SEM image of the cathode material of a lithium-ion battery treated by the removal method proposed by the present invention and an EDS image of the C/O/F/Na element. It can be seen from Figure 2 that after thermal catalytic treatment, the organic fluorine in the cathode material is effectively removed Removed and solidified into sodium fluoride, specifically corresponding to the treated cathode material in Example 1.

Figure 3 is an XRD pattern of the fluoride salt (fluoride salt) separated by the present invention. It can be seen from Figure 3 that when an alkaline metal hydroxide is used for thermal catalytic treatment, the organic fluorine in the cathode material is directionally converted into inorganic fluoride. Solidify into fluoride salt, specifically corresponding to Examples 1-4.

In summary, the present invention uses alkaline metal hydroxide as both a catalyst and a capture agent to realize the thermal catalytic removal and solidification separation of organic fluorine in the lithium-ion battery cathode material in one step, effectively removing the organic fluorine binder. , conducive to resource utilization of cathode materials, and at the same time effectively avoids potential secondary environmental pollution risks of organic fluorine. This method relies on heat treatment technology that is widely used in industry, is simple to operate, easy to apply on a large scale, and has broad industrial application potential.

In addition, those skilled in the art should understand that although there are many problems in the prior art, each embodiment or technical solution of the present invention can only be improved in one or several aspects, without having to simultaneously solve the problems in the prior art or All technical issues listed in the background art. Those skilled in the art will understand that content not mentioned in a claim shall not be used as a limitation on the claim.

Although terms such as cathode sheet, cathode material, alkaline metal hydroxide, oxygen-free roasting, water washing and filtration are frequently used in this article, the possibility of using other terms is not excluded. The use of these terms is only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention; the description and claims of the embodiments of the present invention and the above appendix The terms "first", "second", etc. (if present) in the figures are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. A method for removing organic fluorine in a lithium ion positive electrode material, comprising the steps of:

obtaining a positive plate of the waste lithium ion battery;

crushing and screening the positive plate to obtain a positive material;

mixing the obtained anode material with alkaline metal hydroxide, and then performing anaerobic roasting;

and washing and filtering the product after anaerobic roasting.

2. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the rotational speed of the crushing is 1000-2000rpm, and the crushing time is 5-30min.

3. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the mesh number of the screening is more than 100 meshes.

4. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the positive electrode material of the lithium ion battery is one or more of lithium cobaltate, ternary lithium, lithium manganate, lithium titanate and lithium iron phosphate.

5. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the alkaline metal hydroxide is one or a mixture of two of sodium hydroxide and potassium hydroxide.

6. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the mass ratio of the positive electrode material to the alkaline metal hydroxide is 100:20-5.

7. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the reaction temperature of the anaerobic roasting is 300-500 ℃, and the reaction time of the anaerobic roasting is 0.5-2h.

8. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the anaerobic roasting is carried out under the condition of 50-100ml/min of nitrogen/argon flow.

9. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the anaerobic roasting is carried out under the condition that the vacuum degree is less than 1000 Pa.

10. The method for removing organic fluorine in a lithium ion cathode material according to claim 1, wherein: the solid-liquid ratio used for the water washing and filtering is 100-200g/L, and the time is 30min.