METHOD FOR THE SAFE PYROLYSIS AND REMOVAL OF CONTAMINATIONS FROM WASTE LITHIUM BATTERIES AND ITS APPLICATION

Abstract

A method for the safe removal of contaminants from a waste lithium battery by pyrolysis, comprising the following steps: (1) primary heating, quenching, and subsequent layer sieving of electrode fragments from a waste lithium battery to obtain a current collector fragment and electrode material, wherein in step (1) an ultrasonic vibrating sieve is used for sieving and the mesh count of a main mesh of the ultrasonic vibrating sieve is 16 or 20 meshes, the mesh count of a transition mesh of the ultrasonic vibrating sieve is 100, 140, or 200 meshes, and the mesh count of a sub-mesh of the ultrasonic vibrating sieve is 500, 540, or 600 meshes; (2) mixing and grinding the electrode material and a grinding aid, soaking the mixture in an alkaline solution, filtering, and removing filter residues to obtain electrode powder;and (3) secondary heating of the electrode powder to obtain a positive electrode material, wherein the secondary heating is carried out at a temperature of 600 °C to 1000 °C and lasts 60 to 90 minutes, and the secondary heating is carried out in an air or oxygen atmosphere, wherein in step (1) the quenching consists of spraying a freeze spray to cool the electrode fragment of the waste lithium battery to a temperature of less than 50 °C within 90 seconds; and the freeze spray is cold air with a temperature of less than 15 °C.

Description

TECHNICAL FIELDThe present disclosure relates to the technical field of recycling an electrode material through a high temperature process, and more particularly, to a method and application (use) for safely removing contaminants from a waste lithium battery through pyrolysis.BACKGROUNDAt present, electrode materials are usually recycled by a wet method and a high temperature method. In the high temperature method, the metal shell of an old lithium battery is broken down into small particles by mechanical grinding, and the electrode material is separated from the electrode fragments by sieving. Meanwhile, organic binders (such as polyvinylidene fluoride and polytetrafluoroethylene), conductive materials, and organic solvents of the electrode material are pyrolyzed. After high temperature heating, there are many impurities present in the electrode material that cannot be effectively pyrolyzed: the organic binder (e.g., polyvinylidene fluoride and polytetrafluoroethylene), polyolefins (e.g., polypropylene and polyethylene) in a separator, conductive agents, carbonic esters (e.g., ethylene carbonate and methylethyl carbonate) in an electrolyte, plastic shell remains of the waste lithium battery, and the like are still present in the particles of the electrode material after high temperature pyrolysis due to uneven heating. At the same time, the mechanical grinding and sieving cannot remove a small part of the residual aluminum and copper powder in the electrode material particles. At a high temperature (above 1200° C.), a positive electrode material and the copper powder in the electrode material may react with the aluminum powder, and the reaction proceeds as follows:First step: LiNi e Co f Mn g O 2 →LiO + eNiO + f CoO + g MnO, e + f + g = 1; (main reaction) 2Cu + O 2 → 2CuO.Second step: eNiO + fCoO + gNbO+2 / 3(e+f+g)Al → 1 / 3(e+f+g)Al 2 O 3+ eNi + fCo + gNb; (main reaction) 3CuO+2A1 → 3Cu+Al 2 O 3.The reaction speed in the second stage is extremely fast, and a large amount of heat is released in a short time so that the temperature in the reaction region reaches more than 2800°C, whereby not only the electrode material in the vicinity of the reaction region can melt but also the high temperature melt is scattered and further melted by a refractory material of an inner wall of a heating furnace and the inner wall of the heating furnace, which is very dangerous.There are more contaminants in the electrode material that not only affect the purity of the electrode material of the waste lithium battery, but also increase the complexity of subsequent treatment of the electrode material, damage equipment, and increase uncertainty factors in the environment of the electrode material treatment.CN105895854A discloses a method for recovering a positive electrode residual material of a lithium ion battery, the method comprising the steps of: completely crushing the positive electrode residual material of the lithium ion battery, heating the positive electrode residual material to 450-650° C. and holding for 90-150 minutes; cooling and sieving the positive electrode residual material to obtain positive electrode material powder collected below a mesh grid and aluminum particles remaining on the mesh grid; washing the positive electrode material powder with an alkaline solution, standing and layering, decanting a supernatant liquid and floating material, and filtering, washing and drying the bottom slurry to obtain the positive electrode material.CN109904546A discloses a method for recovering aluminum foil and cathode materials from used lithium ion batteries. The method comprises the steps of: (1) discharging the lithium ion waste batteries at a certain temperature, manually disassembling the discharged batteries, and then recovering battery cathodes; (2) regularly crushing the recovered battery cathodes into regular cathode fragments in a geometrically regular form; (3) charging the recovered regular cathode fragments into a ceramic crucible to be subjected to aerobic roasting under normal pressure; (4) soaking the roasted cathode fragments and quenching them with water at a certain temperature, sieving the water-quenched cathode fragments, and then recovering the aluminum foil; and (5) placing the sieving underflow into alkaline brine to be soaked to remove aluminum impurities, and after filtering and drying, recovering the cathode materials.CN112960705A discloses a method for positive electrode material recovery for quaternary lithium ion batteries. The method comprises the steps of: decomposing and roasting; performing ball milling; leaching an aluminum-containing solution; precipitating aluminum hydroxide; and precipitating the Li element.WO2012161168A1 discloses a method for recovering valuable material from a positive electrode in a lithium ion secondary battery containing a collector comprising aluminum and valuable material comprising at least one of cobalt and nickel, the method comprising: a heating step in which the positive electrode in the lithium ion secondary battery is heated to 500-600°C, preferably 590-610°C; and a screen-screen step in which the positive electrode is screened using a screen having mesh openings of not more than 2.0 mm after the heating step, and recovered material containing the valuable material and having a collector content of not more than 2% by mass is obtained.SUMMARYThe features of the method according to embodiments of the present invention are defined in the appended claims.The present disclosure aims to solve at least one of the above-mentioned technical problems of the related art. To this end, the present disclosure provides a method and use for safely removing contaminants from a waste lithium battery by pyrolysis. The process eliminates residual organic binders, conductive agents, organic solvents, aluminum, and other impurities in the electrode material of the waste lithium battery and improves the purity of the electrode material and safety during pyrolysis.In order to achieve the above objects, the following technical solutions are applied in the present disclosure.A method for safely removing impurities from a lithium waste battery by pyrolysis comprises the steps of: (1) primarily heating electrode fragments from a lithium waste battery, quenching and subsequent layer screening to obtain a current collector fragment and an electrode material; (2) mixing and grinding the electrode material and a grinding aid, soaking the mixture in an alkali liquor, filtering and removing filter residues to obtain electrode powder; and (3) secondary heating the electrode powder to obtain a positive electrode material.Preferably, in the step (1), the electrode fragment of the waste lithium battery is obtained by discharging and crushing the waste lithium battery.The comminution reduces the formation of fine aluminum and copper particles, reduces contaminants in the battery material and facilitates recycling of the current collector fragment.Preferably, the quenching in step (1) is to spray a frozen spray to cool the electrode fragment of the waste lithium battery to a temperature of less than 50°C within 90 seconds; and the frozen spray is cold air having a temperature of less than 15°C.Preferably, in the step (1), the primary heating is carried out at a temperature of 420°C to 600°C and takes 45 minutes to 90 minutes.Preferably, in step (1), the primary heating is carried out in an air or oxygen atmosphere.When the electrode waste fragments are heated, the adhesion property of the binders (polyvinylidene fluoride and polytetrafluoroethylene) decreases and the electrode materials become brittle; in the meantime, the surface temperature of the electrode waste fragment rapidly decreases, a notch of the current collector (aluminum foil and copper foil) on the waste electrode becomes thinner, the temperature of the notch portion decreases more rapidly, a shrinking force is generated first, and then the notch of the current collector fragment rapidly rolls in, and the notch between the current collector fragment and the electrode material of the waste lithium battery is larger. After the sieving, the electrode material of the waste lithium battery is more likely to fall off.Preferably, in the step (1), an ultrasonic vibrating screen is used for the layered screening, and the mesh number of a main mesh (mother mesh) of the ultrasonic vibrating screen is 16 meshes or 20 meshes, the mesh number of a transition mesh of the ultrasonic vibrating screen comprises 100 meshes or 140 meshes or 200 meshes, and the mesh number of a sub-mesh (daughter mesh) of the ultrasonic vibrating screen comprises 500 meshes or 540 meshes or 600 meshes.By using the ultrasonic vibrating screen for the layer screening, the screen function is utilized with high precision and high mesh width, and at the same time, a narrow particle size range of the electrode material of the waste lithium battery can be controlled, contributing to improvement of the screen accuracy and the discharge efficiency by 20 to 50%. When three layers of mesh screens are used together, an ultrasonic vibration screen can be connected to a plurality of electric / acoustic energy converters at the same time and screen at different powers and vibration frequencies. The electrode material of the waste lithium battery has the properties of certain adsorption and high static electricity during sieving. These adverse properties can be eliminated by using the ultrasonic vibrating screen, so that the electrode material and the collector can be separated efficiently by simply screening.Screening and sorting by the three mesh layers consisting of the main mesh, the transition mesh and the sub-mesh can recycle different types of material well and different materials in a targeted manner. The main net mainly intercepts the fragments of the current collector, the transition net intercepts the fragments of the electrode material containing more impurities, the sub net intercepts some coarse electrode materials containing more impurities, and fine electrode materials pass through the sub net. The electrode materials having different sizes and shapes intercepted by the main mesh, transition mesh and sub-mesh are subjected to a second screening and collection.In the step (1), the electrode material preferably refers to an electrode material fragment, a coarse electrode material, and a fine electrode material.The electrode material fragment and the coarse electrode material are further preferably crushed and sieved to obtain coarse current collector particles and the coarse electrode material, then the coarse electrode material is crushed and sieved to obtain the fine electrode material.After most of the aluminum and copper have been removed, the electrode fragment and coarse electrode material are further crushed in a crusher and passed through the subnet.Preferably, in the step (1), the current collector fragment is washed with water and dried, and then the current collector fragment is recycled.In step (2), the grinding aid preferably comprises at least one of the following substances: white carbon black, opal powder, quartz powder. (The main component of the white carbon black, the opal powder or the quartz powder is silica.)Preferably, in the step (2), the mass ratio of the grinding aid to the electrode material is (0.1 to 0.5):100.Preferably, the grinding in step (2) takes 30 minutes to 120 minutes, and the rotational speed of a grinding machine used for grinding is 300 U / min to 600 U / min.In the step (2), the alkali liquor is preferably sodium hydroxide, magnesium hydroxide, potassium hydroxide or calcium hydroxide.More preferably, the OH - concentration of the alkali solution is 0.01 mol / L to 0.2 mol / L.Preferably, the soaking in step (2) takes between 10 and 15 minutes.Preferably, the process in step (2) further comprises the steps of washing and drying the filter cake.Preferably, in step (2), the filtered filtrate is treated with alkali, which can be used for resoaking the ground electrode powder.Preferably, in the step (3), the secondary heating is carried out at a temperature of 600°C to 1000°C and takes 60 minutes to 90 minutes.Preferably, in step (3), the secondary heating is carried out in an air or oxygen atmosphere.The present disclosure further provides an application of the method in recycling electrode materials.Compared with the prior art, the present disclosure has the following advantageous effects. 1. according to the method of the present disclosure, the primary heating is performed on the electrode fragment of the waste lithium battery to reduce the adhesion property of the binder while rapidly reducing the surface temperature of the electrode fragment of the waste lithium battery. Since the notch of the collector fragment (aluminum foil and copper foil) is thinner, the temperature of the notch portion decreases more quickly, the shrinkage force is generated first, and then the notch of the current collector fragment rolls in first. Therefore, the notch between the current collector fragment and the electrode material of the waste lithium battery is enlarged, and after the shield, the electrode material of the waste lithium battery is more likely to fall off. 2. in the method of the present disclosure, the grinding aid is used to reduce the density of the electrode material and increase the uniformity of the ground electrode material, thereby avoiding an agglomeration phenomenon in dry grinding of the electrode material, eliminating an electrostatic effect, promoting a reaction between the aluminum in the electrode material and diluted alkali, and lowering the temperature of the secondary heating. Then, the residual aluminum powder can be dissolved by soaking the electrode material with the alkali solution, and the grinding aid is also dissolved in the diluted alkali, so that the diluted alkali can synchronously remove the aluminum and the grinding aid from the electrode material, and the filtered diluted alkali filtrate can be reused in alkali leaching of the electrode material of the waste lithium battery, thereby reducing alkali consumption. 3. In the primary heating, most of the organic binders (such as polyvinylidene fluoride and polytetrafluoroethylene), conductive agents, organic solvents and other impurities are pyrolyzed, and in the secondary heating, a few residual impurities which cannot be pyrolyzed in the primary heating are pyrolyzed and carbonized.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will be explained in more detail below with reference to the attached drawings and exemplary embodiments, wherein: FIG. 1 is a process flow chart of Embodiment 1 of the present disclosure.DETAILED DESCRIPTIONEmbodiment 1A method for safely removing impurities from a waste lithium battery by pyrolysis of this embodiment comprises the following steps: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 7.34 kg, putting the electrode waste fragments into a heating furnace for primary heating for 45 minutes under the conditions of 586°C and introducing oxygen, moving the heated electrode waste fragments in a screen basket and spraying cold air at 10°C for quenching, selecting an ultrasonic vibrating screen for screening (16 meshes for a main net, 100 meshes for a transition net and 540 meshes for a sub-net), wherein the main net collects current collector fragments, the transition net collects material fragments containing contaminants, and the sub net collects coarse electrode materials containing more contaminants; (2) Washing and drying the current collector fragments captured by the main net, collecting the current collector fragments, crushing the electrode material fragments captured by the transition net and the coarse electrode materials captured by the sub net into fine particles by a breaker, sieving with the transition net and the sub net of the ultrasonic vibrating sieve for the second time, in the second sieving, capturing and collecting the coarse current collector particles by the transition net, and using the coarse electrode material captured by the sub net for crushing again into fine particles by the breaker, and then sieving the fine particles by the sub net to obtain the electrode material; (3) Supplying white carbon black and the electrode material in a mass ratio of 0.41:100 to an oscillating ball mill at a revolution number of 540 U / min for grinding for 87 minutes, soaking in a sodium hydroxide solution having an OH - concentration of 0.031 mol / L for 12 minutes and filtering to obtain a filtrate and a filter residue, wherein the filtrate can be used for re-soaking the electrode powder when supplemented with alkali, and washing the filter residue with water and then drying the filter residue to obtain electrode powder; and (4) charging the electrode powder to a heating furnace and then heating in the heating furnace at 755° C. for 87 minutes with supply of air to obtain 5.37 kg of positive electrode material.FIG. 1 is a process flow chart of Embodiment 1 of the present disclosure. From Fig. 1, it is seen that the waste lithium battery is discharged and subjected to first crushing to obtain the electrode waste fragments, and then subjected to first heating, cooling and sieving, and then laminated and sieved by using the ultrasonic vibrating sieve, i.e., sieved and graded by the three layers of nets comprising the main net, the transition net and the sub-net, and then removed by the diluted brine of impurities, filtered and subjected to second heating to obtain the electrode powder.Embodiment 2A method of this embodiment for safely removing impurities from a waste lithium battery by pyrolysis comprises the steps of: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 8.79 kg, charging the electrode waste fragments into a heating furnace for primary heating for 69 minutes under the conditions of 550°C and introducing oxygen, moving the heated electrode waste fragments into a screen basket and spraying cold air at 10°C for quenching, selecting an ultrasonic vibrating screen for screening (20 meshes for a main net, 100 meshes for a transition net and 540 meshes for a sub-net), wherein the main net collects current collector fragments, the transition net collects material fragments containing contaminants, and the sub net collects coarse electrode materials containing more contaminants; (2) Washing and drying the current collector fragments captured by the main net, collecting the current collector fragments, crushing the electrode material fragments captured by the transition net and the coarse electrode materials captured by the sub net into fine particles by a breaker, sieving with the transition net and the sub net of the ultrasonic vibrating sieve for the second time, in the second sieving, the capturing and collecting of the coarse current collector particles is performed by the transition net and the use of the coarse electrode material captured by the sub net for crushing into fine particles again by the breaker, then sieving of the fine particles is performed by the sub net to obtain the electrode material; (3) Supplying white carbon black and the electrode material in a mass ratio of 0.27:100 to an oscillating ball mill at a revolution number of 480 rpm for grinding for 104 minutes, soaking in a dilute sodium hydroxide solution having an OH - concentration of 0.157 mol / L for 10 minutes and filtering to obtain a filtrate and a filter residue, wherein the filtrate can be used for re-soaking the electrode powder when supplemented with alkali, and washing the filter residue with water and then drying the filter residue to obtain electrode powder; and (4) charging the electrode powder into a heating furnace and then heating in the heating furnace at 695° C. for 78 minutes with supply of air to obtain 6.64 kg of positive electrode material.Embodiment 3A method of this embodiment for safely removing impurities from a waste lithium battery by pyrolysis comprises the steps of: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 3.37 kg, introducing the electrode waste fragments into a heating furnace for primary heating for 57 minutes under the conditions of 580°C and introducing oxygen, moving the heated electrode waste fragments into a screen basket and spraying cold air at 10°C for quenching, selecting an ultrasonic vibrating screen for screening (20 mesh for a main net, 100 mesh for a transition net and 600 mesh for a sub-net), wherein the main net collects current collector fragments, the transition net collects material fragments containing contaminants, and the sub net collects coarse electrode materials containing more contaminants; (2) Washing and drying the current collector fragments captured by the main net, collecting the current collector fragments, crushing the electrode material fragments captured by the transition net and the coarse electrode materials captured by the sub net into fine particles by a breaker, sieving with the transition net and the sub net of the ultrasonic vibrating sieve for the second time, in the second sieving, the capturing and collecting of the coarse current collector particles by the transition net and using the coarse electrode material captured by the sub net for crushing again into fine particles by the breaker, and then sieving the fine particles by the sub net to obtain the electrode material; (3) Supplying white carbon black and the electrode material in a mass ratio of 3:100 to an oscillating ball mill at a revolution number of 540 U / min for grinding for 76 minutes, soaking in a diluted sodium hydroxide solution having an OH - concentration of 0.138 mol / L for 15 minutes and filtering to obtain a filtrate and a filter residue, wherein the filtrate can be used for re-soaking the electrode powder when supplemented with alkali, and washing the filter residue with water and then drying the filter residue to obtain electrode powder; and (4) charging the electrode powder into a heating furnace and then heating in the heating furnace at 845° C. for 67 minutes with supply of air to obtain 6.31 kg of positive electrode material.Embodiment 4A method of this embodiment for safely removing impurities from a waste lithium battery by pyrolysis comprises the steps of: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 7.83 kg, putting the electrode waste fragments into a heating furnace for primary heating for 68 minutes under the conditions of 490°C and introducing oxygen, moving the heated electrode waste fragments into a screen basket and spraying cold air at 10°C for quenching, selecting an ultrasonic vibrating screen for screening (16 meshes for a main net, 200 meshes for a transition net and 600 meshes for a sub-net), wherein the main net collects current collector fragments, the transition net collects material fragments containing contaminants, and the sub net collects coarse electrode materials containing more contaminants; (2) Washing and drying the current collector fragments captured by the main net, collecting the current collector fragments, crushing the electrode material fragments captured by the transition net and the coarse electrode materials captured by the sub net into fine particles by a breaker, sieving with the transition net and the sub net of the ultrasonic vibrating sieve for the second time, in the second sieving, the capturing and collecting of the coarse current collector particles by the transition net and using the coarse electrode material captured by the sub net for crushing again into fine particles by the breaker, and then sieving the fine particles by the sub net to obtain the electrode material; (3) Feeding opal powder and the electrode material in a mass ratio of 0.14 : 100 into an oscillating ball mill at a speed of 540 U / min for grinding for 69 minutes, soaking in a diluted potassium hydroxide solution having an OH - concentration of 0.175 mol / L for 15 minutes and filtering to obtain a filtrate and a filter residue, wherein the filtrate can be used for re-soaking the electrode powder when supplemented with alkali, and washing the filter residue with water and then drying the filter residue to obtain electrode powder; and (4) feeding the electrode powder into a heating furnace and then heating in the heating furnace at 755° C. for 75 minutes with feeding air to obtain 5.64 kg of positive electrode material.Comparative Example 1A method of this comparative example for safely removing impurities from a waste lithium battery by pyrolysis comprises the steps of: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 7.45 kg, charging the electrode waste fragments into a heating furnace for cooling at a normal temperature for 53 minutes under the conditions of 615°C and introducing oxygen, selecting an ultrasonic vibrating screen for screening (16 mesh for a main net, 140 mesh for a transition net, and 500 mesh for a sub net), the main net collecting current collector fragments, the transition net collecting material fragments containing impurities, The subnet collects coarse electrode materials containing more impurities; (2) washing and drying the current collector fragments captured by the subnet, collecting the current collector fragments, crushing the electrode material fragments captured by the subnet and the coarse electrode materials captured by the subnet into fine particles by a breaker, sieving with the subnet and the subnet of the ultrasonic vibrating sieve for the second time, in the second sieving, the capturing and collecting of the coarse current collector particles by the subnet and using the coarse electrode material captured by the subnet to be re-crushed into fine particles by the breaker, and then sieving the fine particles by the subnet to obtain the electrode material; (3) Supplying white carbon black and the electrode material in a mass ratio of 0.43:100 to an oscillating ball mill at a revolution number of 480 rpm / min for grinding for 72 minutes, soaking in a diluted sodium hydroxide solution having an OH - concentration of 0.076 mol / L for 14 minutes, and filtering to obtain a filtrate and a filter residue, wherein the filtrate can be used for re-soaking the electrode powder when supplemented with alkali, and washing the filter residue with water, and then drying the filter residue to obtain electrode powder; (4) Charging the electrode powder into a heating furnace and then heating in the heating furnace at 850°C for 74 minutes under the condition that air is supplied to obtain 5.64 kg of positive electrode material.Comparative Example 2A method of this comparative example for safely removing impurities from a waste lithium battery by pyrolysis comprises the following steps: (1) recycling a waste lithium battery, discharging and precomminuting to obtain electrode waste fragments having a length and width of 2 cm to 3 cm and a mass of 8.07 kg, putting the electrode waste fragments into a heating furnace for primary heating for 45 minutes under the conditions of 585°C and introducing oxygen, moving the heated electrode waste fragments into a screen basket and spraying cold air at 10°C for quenching, selecting an ultrasonic vibration screen for screening (16 mesh for a main net, 200 mesh for a transition net and 600 mesh for a sub-net), wherein the main net collects current collector fragments, the transition net collects material fragments containing contaminants, and the sub net collects coarse electrode materials containing more contaminants; (2) Washing and drying the current collector fragments captured by the main net, collecting the current collector fragments, crushing the electrode material fragments captured by the transition net and the coarse electrode materials captured by the sub net into fine particles by a breaker, sieving with the transition net and the sub net of the ultrasonic vibrating sieve for the second time, in the second sieving, the capturing and collecting of the coarse current collector particles by the transition net and using the coarse electrode material captured by the sub net for crushing again into fine particles by the breaker, and then sieving the fine particles by the sub net to obtain the electrode material; (3) Feeding the electrode material into an oscillating ball mill at a revolution number of 540 rpm / min for grinding for 78 minutes, soaking in a dilute potassium hydroxide solution having an OH - concentration of 0.094 mol / L for 15 minutes and filtering to obtain a filtrate and a filter residue, wherein the filtrate could be used for re-soaking the electrode powder when supplemented with alkali and washing the filter residue with water and then drying the filter residue to obtain electrode powder; and (4) charging the electrode powder into a heating furnace and then heating in the heating furnace at 780°C for 87 minutes with supply of air to obtain 6.24 kg of positive electrode material. Table 1 shows detection values of aluminum and carbon in electrode materials of Working Examples 1, 2, 3 and 4 and Comparative Examples 1 and 2 Table 1 shows detection values of aluminum and carbon in electrode materials of Working Examples 1, 2, 3 and 4 and Comparative Examples 1 and 2Embodiment 10.780.0510.670.017Embodiment 20.330.0460.450.013Embodiment 30.610.0480.880.018Embodiment 40.690.0310.710.015Comparative Example 10.910.210.830.023Comparative Example 20.780.150.910.031It is apparent from Table 1 that the positive electrode materials obtained by the removal of impurities by pyrolysis by the methods of Embodiments 1 to 4 of the present disclosure have a low aluminum content while the method of Comparative Example 1 cools slowly at normal temperature, which is not detrimental to the low degree of curling of the current collector fragment. As a result, the notch between the current collector fragment and the electrode material of the waste lithium battery is reduced, and the electrode material of the waste lithium battery does not easily fall off after sieving, so that the aluminum content before diluted alkali treatment is high. In Comparative Example 2, no grinding aid is added, resulting in an agglomeration phenomenon unfavorable for the particle dispersion, resulting in a larger particle size unfavorable for the carbonized scab dispersion by heating the binders, conductive agents and organic solvents, and thus unfavorable for the reaction between aluminum and diluted alkali, resulting in aluminum residues after the treatment with diluted alkali.

Claims

A method for safely removing impurities from a lithium waste battery by pyrolysis, comprising the steps of: (1) primarily heating, quenching, and then layer-screening electrode fragments from a lithium waste battery to obtain a current collector fragment and an electrode material, wherein in the step (1), an ultrasonic vibrating screen is used for screening, and a mesh number of a main mesh of the ultrasonic vibrating screen is 16 meshes or 20 meshes, a mesh number of a transition mesh of the ultrasonic vibrating screen is 100 meshes or 140 meshes or 200 meshes, and a mesh number of a sub-mesh of the ultrasonic vibrating screen is 500 meshes, 540 meshes or 600 meshes; (2) Mixing and grinding the electrode material and a grinding aid, soaking the mixture in an alkali solution, filtering and removing filter residues to obtain electrode powder; and (3) secondary heating the electrode powder to obtain a positive electrode material, wherein the secondary heating is performed at a temperature of 600°C to 1000°C and takes 60 minutes to 90 minutes, and the secondary heating is performed in an air or oxygen atmosphere, wherein in the step (1), the quenching is to spray a freeze spray to cool the electrode fragment of the lithium waste battery to a temperature of less than 50°C within 90 seconds; and the freeze spray is cool air having a temperature of less than 15°C.The method according to claim 1, wherein in the step (1), the primary heating is performed at a temperature of 420°C to 600°C and takes 45 minutes to 90 minutes, and the primary heating is performed in an air or oxygen atmosphere.The method according to claim 1, wherein in the step (2), the grinding aid is white carbon black and / or opal powder and / or quartz powder.The method according to claim 1, wherein in the step (2), the mass ratio of the grinding aid to the electrode material is 0.1 to 0.5:100.The method of claim 1, wherein in step (2), the alkali liquor is one of the following elements: sodium hydroxide, magnesium hydroxide, potassium hydroxide, calcium hydroxide.The process according to claim 1, wherein in the step (2), the OH concentration of the alkali liquor is 0.01 mol / L to 0.2 mol / L.Use of the method according to one of claims 1 to 6 in the recycling of an electrode material.

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