A method for removing magnetic substances from waste lithium battery positive electrode materials

Abstract

The present invention provides a method for removing magnetic substances from waste lithium battery positive electrode materials, comprising the following steps: (1) subjecting waste lithium battery positive electrode materials to a two-stage calcination treatment; (2) adding a dispersant to the calcined material, and adding water for stirring and slurrying to obtain a mixed slurry; and (3) subjecting the mixed slurry to magnetic separation to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity and the non-magnetic product is a positive electrode material. The present invention first uses a two-stage calcination treatment to fully convert the elemental iron in the waste lithium battery positive electrode material into ferroferric oxide, and then disperses the calcined material in water and performs magnetic separation to finally obtain a recyclable positive electrode material with the magnetic impurities removed. Since the positive electrode material is calcined before the magnetic separation, the structure of the battery positive electrode material can also be made denser, which can improve the electrochemical performance of subsequent regeneration and repair.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of waste batteries, and in particular relates to a method for removing magnetic substances from positive electrode materials of waste lithium batteries. Background Art

[0002] Lithium-ion batteries (Li-ion batteries) have become the power source for numerous mobile devices due to their high energy density and operating voltage, long cycle life, low self-discharge rate, wide operating temperature range, and minimal environmental pollution. However, due to their limited service life, their widespread use inevitably leads to a significant amount of battery waste. Failure to properly dispose of spent Li-ion batteries can lead to serious environmental problems and a waste of resources. Therefore, cost-effectively recovering the valuable components from spent Li-ion batteries is crucial.

[0003] Lithium-ion batteries are generally composed of positive electrode materials, negative electrode materials, electrolytes, separators, current collectors, and casings. The positive electrode materials hold significant economic value, and therefore, their recycling is attracting increasing attention from researchers. Currently, the recycling of spent lithium-ion battery positive electrode materials primarily involves three aspects: the enrichment and purification of metal elements, the separation and enrichment of mixed electrode materials, and the regeneration and restoration of battery materials. Currently, the enrichment and purification of metal elements primarily utilizes traditional chemical and metallurgical methods to recover valuable metal components from positive electrode materials. However, this process has drawbacks such as high production costs and the potential for secondary pollution. It also disrupts the battery material structure, reducing the material's recovery value. The separation and enrichment of mixed electrode materials primarily involves separating and purifying the mixed positive and negative electrode materials without compromising the functional integrity of the electrode materials, thereby obtaining a higher-purity electrode material product. Currently, the separation and enrichment of mixed electrode materials is typically performed using physical methods, typically employing flotation, gravity separation, and color sorting. Physical sorting methods to separate positive and negative electrode mixed materials can ensure the integrity of the electrode materials to the greatest extent, facilitate subsequent regeneration and repair, and achieve higher economic value. Therefore, it is a current research hotspot in the field of lithium battery recycling.

[0004] However, due to the complex composition of mixed electrode materials, the cathode materials obtained through separation and enrichment still contain certain magnetic impurities (mainly elemental Fe). If these magnetic impurities cannot be effectively removed, they will seriously affect the electrochemical performance of the regenerated and repaired electrode materials, causing battery self-discharge and posing a significant safety hazard. Therefore, it is of great significance to develop an economical, environmentally friendly, simple and efficient method for removing magnetic substances from recycled cathode materials. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the existing waste battery recycling process and provide a method for removing magnetic substances in the positive electrode materials of waste lithium batteries to solve the problem of high magnetic impurity content in the current waste battery electrode materials. The method has simple process, easy operation, low production cost, clean and efficient.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for removing magnetic substances from anode materials of waste lithium batteries comprises the following steps:

[0008] (1) The waste lithium battery positive electrode material is subjected to a two-stage roasting treatment;

[0009] (2) adding a dispersant to the calcined material, adding water, stirring and slurrying to obtain a mixed slurry;

[0010] (3) The mixed slurry is subjected to magnetic separation to obtain magnetic products and non-magnetic products, wherein the magnetic products are magnetic impurities and the non-magnetic products are positive electrode materials.

[0011] The present invention first uses a two-stage calcination process to fully convert the elemental iron in the waste lithium battery positive electrode material into ferroferric oxide. The calcined material is then dispersed in water and subjected to magnetic separation, ultimately obtaining a recyclable positive electrode material with magnetic impurities removed. The calcination step before magnetic separation allows the positive electrode material to oxidize any remaining elemental iron. This also makes the battery positive electrode material more compact, improving the electrochemical performance and safety of subsequent regeneration and repair.

[0012] Compared to conventional calcination treatments for cathode materials, the present invention performs a first-stage calcination to remove volatile impurities contained in the waste lithium battery cathode material while converting some elemental iron into ferroferric oxide. This is followed by a second-stage calcination, which allows the iron to be converted to the highly magnetic ferroferric oxide as much as possible under relatively mild reaction conditions, thus avoiding a violent reaction that could damage the cathode material's usable properties. This two-stage calcination also avoids the problem of a single-stage calcination, which can prevent some elemental iron from converting into ferroferric oxide.

[0013] More preferably, in the above step (1), the calcination temperature of the first stage is 350-600° C., and the calcination time is 1-3 h.

[0014] Further preferably, in the above step (1), the second stage of calcination is performed at a temperature of 500-1000°C and for a time of 1-5 hours. Temperatures that are too low or too high, or calcinations that are too short or too long, can result in insufficient or excessive oxidation of the elemental iron, generating other components and ultimately reducing the removal effect of magnetic impurities.

[0015] More preferably, the first calcination is performed in an air atmosphere, and the second calcination is performed in a steam atmosphere. The air atmosphere of the first calcination is used to expel volatile impurities from the cathode material and to cause a small amount of iron to react first to form ferroferric oxide. The steam atmosphere of the second calcination is used to cause the primary reaction, which is to cause the iron in the cathode material to react first to form ferroferric oxide.

[0016] Further preferably, the water vapor atmosphere is adjusted by continuously introducing water vapor from the lower air inlet of the tubular furnace during the second-stage roasting process to completely replace the air, and allowing excess water vapor to be discharged from the upper air outlet of the atmosphere furnace.

[0017] More preferably, the dispersant is one or more of water glass, sodium hexametaphosphate, sodium polyacrylate, and carboxymethyl cellulose. The use of these dispersants can prevent the positive electrode material from introducing substances that affect the performance of the material after the magnetic material is separated.

[0018] More preferably, the amount of the dispersant is 5 to 900 grams per ton of the calcined material. The purpose of the dispersant is to fully disperse the positive and negative electrode materials in the water. If the amount of dispersant is too low, the dispersion effect will not be achieved, affecting the subsequent magnetic separation effect. If the amount is too high, it will increase costs and waste resources, and will also affect subsequent filtration, making filtration difficult and prolonging the filtration time.

[0019] More preferably, the mass concentration of the mixed slurry is 5% to 55%.

[0020] Further preferably, in the above step (2), the stirring device used for stirring and slurrying is a mechanical stirrer, the stirring speed is 100 to 3000 r / min, and the stirring time is 2 to 30 minutes. The purpose of controlling the appropriate stirring speed and time is to fully disperse the magnetic impurities and the positive electrode material. Too low a speed or too short a time will cause uneven dispersion, affecting the subsequent magnetic separation effect. Too high a speed or too long a time will cause waste.

[0021] Further preferably, in the above step (3), the magnetic separation equipment is a wet high-intensity magnetic separator with a magnetic field strength of 0.1 to 1T.

[0022] The main technical principles of the present invention are as follows:

[0023] In step (1), elemental iron is calcined to produce ferroferric oxide, which has stronger magnetic properties. The chemical reaction equation is as follows:

[0024]

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The advantage of the present invention is that it can make elemental iron generate ferroferric oxide with stronger magnetic properties, thereby improving the efficiency of magnetic separation. The present invention subjects waste lithium battery positive electrode materials to a calcination treatment to make elemental iron generate ferroferric oxide with stronger magnetic properties, and adds a dispersant to the calcined mixture to obtain a relatively uniform mixed slurry, thereby improving the removal efficiency of fine-grained magnetic impurities and removing magnetic impurities to the greatest extent. The present invention mainly addresses the difficult problem of removing magnetic impurities from fine-grained waste lithium battery positive electrode materials due to entrainment and other reasons, and has the advantages of high removal efficiency, economy and environmental protection, simple operation, and easy large-scale production. In addition, since the calcination step is carried out before the positive electrode material is subjected to magnetic separation, the positive electrode material can simultaneously oxidize a small amount of elemental iron that has not been removed, thereby improving the safety of subsequent repair of the electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart for removing magnetic substances from the positive electrode materials of waste lithium batteries. DETAILED DESCRIPTION

[0028] In order to facilitate understanding of the present invention, the present invention is described in more comprehensive and detailed manner below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0029] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0031] Example 1

[0032] Reference Figure 1 In an embodiment of the present invention, a method for removing magnetic substances from a cathode material of a waste lithium battery comprises the following steps:

[0033] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 480 ° C for 1.5 h; the second calcination was carried out in a steam atmosphere at a temperature of 600 ° C for 2 h to obtain a calcined product.

[0034] (2) The calcined material was placed in a beaker, and carboxymethyl cellulose was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 500 r / min and a stirring time of 20 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0035] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.1 T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0036] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 99.35%.

[0037] Example 2

[0038] In an embodiment of the present invention, a method for removing magnetic substances from a cathode material of a waste lithium battery comprises the following steps:

[0039] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 500 ° C and a calcination time of 1.4 h. The second calcination was carried out in a steam atmosphere at a temperature of 650 ° C and a calcination time of 1.8 h to obtain a calcined product.

[0040] (2) The calcined material was placed in a beaker, and sodium hexametaphosphate was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 600 r / min and a stirring time of 18 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0041] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.15T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0042] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 99.41%.

[0043] Example 3

[0044] In an embodiment of the present invention, a method for removing magnetic substances from a cathode material of a waste lithium battery comprises the following steps:

[0045] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 520°C for 1.3 h. The second calcination was carried out in a steam atmosphere at a temperature of 680°C for 1.7 h to obtain a calcined product.

[0046] (2) The calcined material was placed in a beaker, and sodium polyacrylate was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 800 r / min and a stirring time of 15 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0047] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.13T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0048] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 99.49%.

[0049] Comparative Example 1

[0050] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 800 ° C for 1.5 h; the second calcination was carried out in a steam atmosphere at a temperature of 1200 ° C for 2 h to obtain a calcined product.

[0051] (2) The calcined material was placed in a beaker, and carboxymethyl cellulose was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 500 r / min and a stirring time of 20 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0052] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.1 T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0053] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 43.19%.

[0054] Comparative Example 2

[0055] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 500 ° C and a calcination time of 1.4 h. The second calcination was carried out in a nitrogen atmosphere at a temperature of 650 ° C and a calcination time of 1.8 h to obtain a calcined product.

[0056] (2) The calcined material was placed in a beaker, and sodium hexametaphosphate was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 600 r / min and a stirring time of 18 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0057] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.15T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0058] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 63.78%.

[0059] Comparative Example 3

[0060] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. The first calcination was carried out in an air atmosphere at a temperature of 520°C for 1.3 h. The second calcination was carried out in a steam atmosphere at a temperature of 680°C for 1.7 h to obtain a calcined product.

[0061] (2) The calcined material was placed in a beaker, and sodium polyacrylate was added in the manner of adding 100 g of dispersant per ton of calcined material, and water was added to make the volume 1000 mL. The mixture was stirred and slurried using an electric mechanical stirrer at a stirring speed of 800 r / min and a stirring time of 15 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material;

[0062] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.13T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0063] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 84.18%.

[0064] Comparative Example 4

[0065] (1) 200 g of recycled waste lithium battery positive electrode material was introduced into a reaction chamber for calcination. A one-stage calcination process was adopted. The calcination was carried out in an air atmosphere at a temperature of 480 ° C and a calcination time of 1.5 h to obtain a calcined product.

[0066] (2) The calcined material was placed in a beaker, and carboxymethyl cellulose was added in the manner of adding 100 g of dispersant per ton of calcined material. Water was added to make the volume 1000 mL and an electric mechanical stirrer was used to stir and prepare the slurry. The stirring speed was 500 r / min and the stirring time was 20 min to fully disperse the magnetic impurity ferroferric oxide and the positive electrode material.

[0067] (3) The stirred mixed slurry is subjected to magnetic separation using a wet high-intensity magnetic separator with a background magnetic field strength of 0.1 T to obtain a magnetic product and a non-magnetic product, wherein the magnetic product is a magnetic impurity (ferroferric oxide) and the non-magnetic product is a positive electrode material.

[0068] After testing, the removal rate of magnetic impurity Fe in the final positive electrode material product was 75.88%.

[0069] The above are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for removing magnetic substances from the positive electrode material of waste lithium batteries, characterized in that: The following steps are involved: (1) subjecting the waste lithium battery positive electrode material to a two-stage calcination treatment; wherein the calcination temperature of the first stage is 350-600°C, the calcination time is 1-3 hours, the calcination temperature of the second stage is 500-1000°C, the calcination time is 1-5 hours, the calcination atmosphere of the first stage is an air atmosphere, and the calcination atmosphere of the second stage is a steam atmosphere; (2) adding a dispersant to the calcined material, adding water, stirring and slurrying to obtain a mixed slurry; (3) The mixed slurry is subjected to magnetic separation to obtain magnetic products and non-magnetic products, wherein the magnetic products are magnetic impurities and the non-magnetic products are positive electrode materials.

2. The removal method according to claim 1, characterized in that The water vapor atmosphere is adjusted in such a way that during the second stage roasting process, water vapor is continuously introduced from the air inlet at the bottom of the tubular furnace to completely replace the air, and excess water vapor is discharged from the air outlet at the top of the atmosphere furnace.

3. The removal method according to any one of claims 1 to 2, characterized in that: The dispersant is one or more of water glass, sodium hexametaphosphate, sodium polyacrylate, and carboxymethyl cellulose.

4. The removal method according to claim 3, characterized in that: The amount of the dispersant used is 5 to 900 grams per ton of the material obtained after roasting.

5. The removal method according to claim 4, characterized in that: The mass concentration of the mixed slurry is 5% to 55%.

6. The removal method according to claim 1, characterized in that: In the step (2), the stirring device used for stirring and slurrying is a mechanical stirrer, the stirring speed is 100 to 3000 r / min, and the stirring time for stirring and slurrying is 2 to 30 minutes.

7. The removal method according to claim 6, characterized in that: In the step (3), the magnetic separation equipment is a wet high-intensity magnetic separator with a magnetic field strength of 0.1 to 1T.

Images