Method for separating positive and negative materials of waste lithium battery by flotation

Abstract

The application relates to a method for separating positive and negative materials of waste lithium batteries by flotation with amino acids as inhibitors. The mixed powder of positive and negative materials can be obtained by physical separation of waste batteries. The separation of positive and negative materials is beneficial to the comprehensive recovery or direct regeneration of subsequent positive and negative materials. The flotation method is a method for separating materials by utilizing the difference in hydrophilicity and hydrophobicity of particles, and has the advantages of low cost and simple process. However, the surface of the positive material of the lithium ion battery is usually coated with a layer of hydrophobic polyvinylidene fluoride (PVDF) binder, which makes it difficult to separate the positive material from the same hydrophobic negative material graphite by flotation. In the application, hydrophilic amino acids are used as flotation inhibitors, and the strong adsorption between the amino acids and the PVDF makes the surface of the positive material change from hydrophobic to hydrophilic, so that the flotation separation of the positive and negative materials is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the recycling technology of waste lithium batteries, in particular to a method for separating positive and negative electrode materials of waste lithium batteries by using flotation method. BACKGROUND

[0002] With the exploitation and use of traditional energy and the popularization of environmental protection awareness, new energy development and utilization gradually attract widespread attention. In recent years, the new energy vehicle industry has developed rapidly, and China has become the world's largest lithium ion battery producer and consumer.

[0003] Lithium batteries are widely used in electric vehicles, mobile communications, portable electronic devices and other fields as high-performance energy storage devices. With the large use and consumption of lithium batteries, the number of waste lithium ion batteries is growing rapidly. Waste lithium batteries are composed of positive electrode materials, negative electrode materials, separators, electrolytes and other components, among which the positive and negative electrode materials are the core part of lithium batteries, containing high-value metal elements such as cobalt, nickel, manganese, aluminum, and carbon materials such as graphite, silicon, etc. Therefore, how to handle and recycle waste lithium batteries has become an important environmental and resource problem.

[0004] Since the positive electrode material has the largest economic value, it has always been the focus of domestic and foreign researchers. For waste lithium ion batteries, after physical sorting, mixed powders of positive and negative electrodes can be obtained, and then the materials can be separated according to the difference in hydrophilicity and hydrophobicity of the particles. However, the surface of the positive electrode material of the lithium ion battery is usually coated with a layer of hydrophobic polyvinylidene fluoride (PVDF) binder, which makes it difficult to separate from the also hydrophobic negative electrode material graphite by flotation method. In the present application, we use hydrophilic amino acids as flotation inhibitors, and use the strong adsorption between amino acids and PVDF to change the surface of the positive electrode material from hydrophobic to hydrophilic, so as to realize the flotation separation of the positive and negative electrode materials. SUMMARY

[0005] The present application aims to provide a method for separating positive and negative electrode materials of waste lithium batteries by flotation using amino acids, to improve the separation efficiency and recovery rate of positive and negative electrode materials of waste lithium batteries, and to reduce the impact on the environment.

[0006] In order to achieve the above-mentioned purpose, the present application provides a method for separating positive and negative electrode materials of waste lithium batteries by flotation using amino acids, comprising the following steps:

[0007] (1) crushing the waste lithium battery to obtain a mixture containing positive and negative electrode materials, separators and other components.

[0008] (2) screening the mixture to remove the separators and other components to obtain a powder containing positive and negative electrode materials.

[0009] (3) The powder is mixed with water and placed in a flotation tank and stirred to prepare a pulp, and then an amino acid inhibitor, a collector and a frother are added in sequence to perform a reverse flotation roughing operation to obtain a froth product and a sink.

[0010] (4) The froth product obtained in the step (3) is further mixed with water and then an amino acid inhibitor, a collector and a frother are added to perform a reverse flotation scavenging operation, and finally a scavenging froth product and a sink are obtained, wherein the froth product is a reverse flotation tailing graphite and the sink is returned to the roughing operation.

[0011] (5) The sink obtained in the reverse flotation roughing operation is mixed with water and placed in a flotation tank and stirred to prepare a pulp, and then an amino acid inhibitor, a collector and a frother are added in sequence to perform a scavenging operation, and finally a froth product and a sink are obtained according to the wettability difference of the positive and negative electrode materials in water, wherein the sink is returned to the roughing operation.

[0012] Preferably, the waste lithium battery is crushed into small pieces of 5-20 mm by using a crushing device in the step (1).

[0013] Preferably, the mixture is sieved into a powder of 0.074-2 mm by using a sieving device in the step (2).

[0014] Preferably, in the steps (3), (4) and (5), a 1.5L self-suction mechanical stirring flotation machine is used, the rotation speed of the flotation machine is 1980 rpm, and the flotation time is 5 min.

[0015] Preferably, in the steps (3), (4) and (5), the frother is MIBC, and the amount used is 20-60 g / t.

[0016] Preferably, in the steps (3), (4) and (5), the collector is kerosene, and the amount used is 50-150 g / t.

[0017] Preferably, the addition amount of the amino acid inhibitor in the step (3) is 8-20% (w / v), which is adjusted according to the type and proportion of the positive and negative electrode materials.

[0018] Preferably, the amino acid inhibitor in the step (3) refers to a functional group composed of an amino group (-NH2) and a carboxyl group (-COOH), and a side chain connected to each amino acid, and the branched chain exhibits hydrophilicity; and one or more of cysteine, aspartic acid, glutamic acid, histidine, asparagine, glutamine, serine, threonine and tyrosine.

[0019] Preferably, the stirring time in the step (4) is 5-30 min.

[0020] The present application has the following technical effects:

[0021] (1) Using amino acid inhibitors as flotation inhibitors can effectively suppress the flotation of positive electrode materials and promote the flotation of negative electrode materials, thereby achieving the separation of positive and negative electrode materials.

[0022] (2) The method of the present invention is simple to operate, has high separation efficiency, consumes a small amount of chemical reagents, and generates a small amount of wastewater and waste residue, which has a small impact on the environment.

[0023] (3) The method of this invention is applicable to the separation of positive and negative electrode materials of various types of waste lithium batteries, such as ternary lithium batteries and lithium iron phosphate batteries. The method of this invention provides a new technical means for the recycling of waste lithium batteries. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process for separating positive and negative electrode materials from waste lithium batteries by amino acid flotation.

[0025] Figure 2 This is a schematic diagram of the process for separating positive and negative electrode materials from waste lithium batteries by amino acid flotation. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0027] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

[0028] The features and performance of the present invention will be further described in detail below with reference to embodiments. A flow chart of amino acid flotation separation of waste lithium battery positive and negative electrode materials is shown below. Figure 1 As shown in the diagram, the process schematic is as follows: Figure 2 As shown.

[0029] Example 1

[0030] A preferred embodiment of the present invention provides a method for separating positive and negative electrode materials of waste lithium batteries using amino acid flotation, the specific steps of which are as follows:

[0031] (1) The waste lithium battery is crushed to obtain a mixture containing positive and negative electrode materials, separator and other components;

[0032] (2) The mixture is sieved to remove the membrane and other components, and a powder containing positive and negative electrode materials is obtained.

[0033] (3) Take 500 g of powder and mix with water in a 1.5 L flotation tank for slurry preparation, the stirring speed is 1980 rmp, and during the slurry preparation process, first add 80 g / t of cysteine, then add 50 g / t of kerosene and 20 g / t of MIBC, after stirring, carry out reverse flotation roughing operation, the flotation time is 5 min, to obtain foam product and sediment;

[0034] (4) Mix the foam product obtained by roughing with water and add 90 g / t of cysteine, 50 g / t of kerosene and 30 g / t of MIBC, and place it in a flotation tank for reverse flotation scavenging operation, the flotation time is 5 min, finally obtain the scavenging foam product and sediment, the foam product is the reverse flotation tailing graphite, and the sediment returns to the roughing operation;

[0035] (5) Mix the sediment obtained by reverse flotation roughing with water and place it in a flotation tank for stirring and slurry preparation, the stirring speed is 1980 rmp, add 90 g / t of cysteine, 50 g / t of kerosene and 30 g / t of MIBC in turn during the slurry preparation process and carry out cleaning operation, the flotation time is 5 min, to obtain cleaning foam product and sediment, the foam product returns to the roughing operation, and the sediment is the reverse flotation concentrate positive material.

[0036] In this embodiment, the positive material in the waste lithium battery is mainly lithium cobalt oxide with a layered structure, and the negative material is mainly graphite with a layered structure. Cysteine is a hydrophilic amino acid inhibitor, which is weakly alkaline in water. By adding cysteine, the positive material surface can be positively charged, and the negative material surface can be negatively charged. In this way, cysteine will be adsorbed on the surface of the positive material, increasing its hydrophilicity and making it settle at the bottom of the water; and because cysteine is adsorbed on the positive material, it will not react with the negative material, so that the negative material remains hydrophobic and floats to the water surface. By the method in this embodiment, efficient separation of the positive and negative materials of the waste lithium battery can be achieved. Through detection, the final recovery rate and grade of the positive cobalt lithium oxide product are 98.03% and 97.23% respectively, and the final recovery rate and grade of the negative graphite powder are 98.89% and 98.26% respectively.

[0037] Example 2

[0038] The preferred embodiment of the present application provides a method for separating positive and negative materials of waste lithium batteries by using amino acid flotation, and the specific steps are as follows:

[0039] (1) The waste lithium battery is crushed to obtain a mixture containing positive and negative materials, separators and other components;

[0040] (2) The mixture is screened to remove the separators and other components, and a powder containing positive and negative materials is obtained;

[0041] (3) Take 500 g of powder and mix with water in a 1.5 L flotation tank for slurry preparation, the stirring speed is 1980 rmp, and during the slurry preparation process, first add 90 g / t of cysteine, then add 50 g / t of kerosene and 20 g / t of MIBC, after stirring, carry out reverse flotation roughing operation, the flotation time is 5 min, to obtain foam product and sediment;

[0042] (4) Mix the foam product obtained by roughing with water and add 100 g / t of cysteine, 50 g / t of kerosene and 30 g / t of MIBC, and place it in a flotation tank for reverse flotation scavenging operation, the flotation time is 5 min, finally obtain the scavenging foam product and sediment, the foam product is the reverse flotation tailing graphite, and the sediment returns to the roughing operation;

[0043] (5) Mix the sediment obtained by reverse flotation roughing with water and place it in a flotation tank for stirring and slurry preparation, the stirring speed is 1980 rmp, add 100 g / t of cysteine, 50 g / t of kerosene and 30 g / t of MIBC in turn during the slurry preparation process and carry out cleaning operation, the flotation time is 5 min, to obtain cleaning foam product and sediment, the foam product returns to the roughing operation, and the sediment is the reverse flotation concentrate positive material.

[0044] In this embodiment, the positive material in the waste lithium battery is a polycrystalline structure mainly composed of ternary composite oxide, and the negative material is an amorphous structure mainly composed of silicon. By adding cysteine, the positive material surface can be positively charged, and the negative material surface can be negatively charged. In this way, cysteine will be adsorbed on the surface of the positive material, increasing its hydrophilicity and making it settle at the bottom of the water; and because cysteine is adsorbed on the positive material, it will not react with the negative material, so that the negative material remains hydrophobic and floats to the water surface. By the method in this embodiment, efficient separation of the positive and negative materials of the waste lithium battery can be achieved.

[0045] By the method in this embodiment, efficient separation of the positive and negative materials of the waste lithium battery can be achieved. Through detection, the final recovery rate and grade of the positive lithium cobalt oxide product are 98.20% and 97.10% respectively, and the final recovery rate and grade of the negative graphite powder are 98.80% and 98.47% respectively.

[0046] Example 3

[0047] The preferred embodiment of the present application provides a method for separating positive and negative materials of waste lithium batteries by using amino acid flotation, and the specific steps are as follows:

[0048] (1) Crush the waste lithium battery to obtain a mixture containing positive and negative materials, separators and other components;

[0049] (2) The mixture is subjected to screening treatment to remove the diaphragm and other components, obtaining a powder containing positive and negative electrode materials;

[0050] (3) 500g of the powder is placed in a 1.5L flotation tank and mixed with water for slurry preparation, the stirring speed is 1980rmp, and during the slurry preparation process, 95g / t of cysteine is first added, then 50g / t of kerosene and 20g / t of MIBC are added, after stirring, the reverse flotation roughing operation is carried out, and the flotation time is 5min, to obtain a foam product and a sediment;

[0051] (4) The foam product obtained by roughing is mixed with water and added with 105g / t of cysteine, 50g / t of kerosene and 30g / t of MIBC, and placed in a flotation tank for reverse flotation scavenging operation, the flotation time is 5min, finally the scavenging foam product and the sediment are obtained, the foam product is the reverse flotation tailing graphite, and the sediment returns to the roughing operation;

[0052] (5) The sediment obtained by reverse flotation roughing is mixed with water and placed in a flotation tank for stirring and slurry preparation, the stirring speed is 1980rmp, 105g / t of cysteine, 50g / t of kerosene and 30g / t of MIBC are added in turn during the slurry preparation process and the cleaning operation is carried out, the flotation time is 5min, the cleaning foam product and the sediment are obtained, the foam product returns to the roughing operation, and the sediment is the reverse flotation concentrate positive material.

[0053] In this embodiment, the positive material in the waste lithium battery is a polycrystalline structure mainly composed of lithium nickel cobalt manganese oxide, and the negative material is a polycrystalline structure mainly composed of lithium titanate. By adding cysteine, the positive material surface can be positively charged, and the negative material surface can be negatively charged. In this way, cysteine will be adsorbed on the surface of the positive material, increasing its hydrophilicity and making it settle at the bottom of the water; and because cysteine is adsorbed on the positive material, it will not react with the negative material, so that the negative material remains hydrophobic and floats to the surface of the water. Through the method in this embodiment, efficient separation of the positive and negative materials of the waste lithium battery can be achieved.

[0054] Through the method in this embodiment, efficient separation of the positive and negative materials of the waste lithium battery can be achieved. Through detection, the final recovery rate and grade of the positive cobalt lithium product are 98.15% and 97.02% respectively, and the final recovery rate and grade of the negative graphite powder are 98.77% and 98.30% respectively.

[0055] Comparative Example 1

[0056] A method for separating positive and negative materials of waste lithium batteries by acid and alkali leaching, the specific steps are as follows:

[0057] (1) The waste lithium battery powder obtained after disassembling and crushing is placed in a reaction kettle, and an appropriate amount of water and 10% sodium hydroxide solution are added, the temperature is controlled at 80°C, and stirring reaction is carried out for 2 hours to obtain an alkaline leaching solution and solid residue;

[0058] (2) The alkaline leaching solution obtained in step (1) is filtered, and the filtrate is collected, which contains the positive electrode material;

[0059] (3) The solid residue obtained in step (1) is placed in another reaction kettle, and an appropriate amount of water and 10% sulfuric acid solution are added, the temperature is controlled at 80°C, and stirring reaction is carried out for 2 hours to obtain an acidic leaching solution and solid residue;

[0060] (4) The acidic leaching solution obtained in step (3) is filtered, and the filtrate is collected, which contains the negative electrode material;

[0061] (5) The filtrates obtained in steps (2) and (4) are further purified and separated to obtain positive and negative electrode material powders.

[0062] In this comparative example, the waste lithium battery is a lithium ion battery with lithium cobalt oxide positive electrode and graphite negative electrode. In this comparative example, the separation rates of the positive electrode material and the negative electrode material are 96.2% and 95.6%, respectively.

[0063] Comparative Example 2

[0064] A method for separating positive and negative electrode materials of waste lithium batteries by a heat treatment method, the specific steps are as follows:

[0065] (1) The waste lithium battery powder obtained after disassembling and crushing is placed in a heat treatment furnace, and heat treatment is carried out at a temperature of 600°C for 1 hour to make the positive and negative electrode materials undergo oxidation reaction, and obtain an oxide mixture;

[0066] (2) The oxide mixture obtained in step (1) is washed with water to remove the surface oxide layer, and obtain a positive and negative electrode material mixture;

[0067] (3) The positive and negative electrode material mixture obtained in step (2) is subjected to magnetic separation with a magnetic separator to separate out the negative electrode material powder;

[0068] (4) The non-magnetic part obtained in step (3) is washed with water to remove the residual negative electrode material, and obtain the positive electrode material powder.

[0069] In this comparative example, the waste lithium battery is a lithium ion battery with lithium cobalt oxide positive electrode and graphite negative electrode. In this comparative example, the separation rates of the positive electrode material and the negative electrode material are 97.4% and 96.8%, respectively.

[0070] Comparative Example 3

[0071] A method for separating positive and negative materials of waste lithium batteries by mechanical separation method, the specific steps are as follows:

[0072] (1) The waste lithium battery powder obtained after disassembling and crushing is placed in a screening machine for screening, and powders of different particle sizes are separated according to the particle size difference of the positive and negative materials;

[0073] (2) The finest particle size powder obtained in step (1) is subjected to air separation by an air separator, and powders of different densities are separated according to the density difference of the positive and negative materials;

[0074] (3) The lightest density powder obtained in step (2) is collected and dehydrated to obtain negative material powder;

[0075] (4) The heaviest density powder obtained in step (2) is collected and dehydrated to obtain positive material powder.

[0076] In the comparative example, the waste lithium battery is a lithium ion battery with lithium cobalt oxide positive electrode and graphite negative electrode. In the comparative example, the separation rates of the positive material and the negative material are 95.8% and 95.2%, respectively.

[0077] Through the comparison between the above examples and the comparative example, it can be concluded that the separation of positive and negative materials of waste lithium batteries by flotation with amino acid inhibitors can improve the separation rate of positive and negative materials of waste lithium batteries under certain conditions.

[0078] It should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations exist in any such actual relationship or order. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or apparatus. Without more limitations, the elements defined by the statement "comprising" do not exclude the presence of additional identical elements in the process, method, article or apparatus including the elements.

[0079] The above examples are only used to illustrate the technical solutions of the present application and are not limited. The present application has been described in detail with reference to the preferred embodiments. Those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A method for separating positive and negative materials of waste lithium batteries by flotation, characterized in that, The application discloses a flotation separation method for positive and negative electrode materials of waste lithium batteries by using amino acids as positive electrode inhibitors. The method comprises the following steps: (1) crushing the waste lithium batteries to obtain a mixture containing positive and negative electrode materials and a diaphragm; (2) screening the mixture obtained in step (1) to remove the diaphragm and obtain a powder containing the positive and negative electrode materials; (3) mixing the powder obtained in step (2) with water, placing the mixture in a flotation tank and stirring and pulp conditioning, wherein the target mineral is the positive electrode material, and then adding an amino acid inhibitor, a collector and a foaming agent in the stirring process, and performing reverse flotation roughing to obtain a foam product and a sediment; (4) further mixing the foam product obtained in step (3) with water, adding an amino acid inhibitor, a collector and a foaming agent, and then placing the mixture in a flotation tank to perform reverse flotation scavenging, so as to finally obtain a scavenging foam product and a sediment, wherein the foam product is a reverse flotation tailing graphite, and the sediment returns to the roughing operation; (5) mixing the sediment obtained in step (3) with water, placing the mixture in a flotation tank and stirring and pulp conditioning, wherein the amino acid inhibitor, the collector and the foaming agent are sequentially added in the stirring and pulp conditioning process, and then performing cleaning to obtain a cleaning foam product and a sediment, wherein the foam product returns to the roughing operation, and the sediment is a reverse flotation concentrate positive electrode material; The mechanical stirring flotation machine is used in steps (3), (4) and (5); the rotation speed of the flotation machine is 1980 rpm, and the flotation time is 5 min; The addition amount of the amino acid inhibitor in steps (3), (4) and (5) is 8-20 % w / v; 2. The method of claim 1, wherein, The amino acid inhibitor in step (4) is composed of an amino group and a carboxyl group, and a side chain connected to each amino acid, and the branched chain exhibits hydrophilicity; the amino acid is cysteine.

3. The method of claim 1, wherein, The crushing treatment in step (1) adopts a shearing machine, a hammer crusher or a blade crusher to crush the waste lithium batteries into small pieces with a size of 5-20 mm. In step (2), the mixture is screened by using a vibrating screen, an air flow screen or a centrifugal screen to screen the mixture into a powder with a size of 0.074-2 mm.

4. The method according to any one of claims 1-3 is applied to separation of positive and negative electrode materials of waste lithium batteries.

Images