Unit battery shredded material, battery shredded material containing the same, and battery processing method

Abstract

The present invention relates to crushed unit batteries, crushed battery material including the same, and a battery processing method, wherein the crushed unit batteries are for recovering valuable metals from waste batteries, and the crushed unit batteries have a layered structure including a separator membrane having a positive electrode or a negative electrode laminated on at least one surface thereof, and can satisfy the following conditions 1 and 2: <Condition 1> The layered structure is a laminated structure of 1 to 7 layers. <Condition 2> The size of the crushed unit battery is 100 mm or less based on the longest axis among the horizontal, vertical, and height directions.

Description

[Technical Field]

[0001] This invention relates to waste batteries, specifically to unit battery fragments extracted from waste battery recycling, battery fragments containing these fragments, and battery processing methods. [Background technology]

[0002] As demand for electric vehicles increases globally, the problem of disposing of waste batteries generated from these vehicles is emerging as a social issue. In the case of lithium secondary batteries, which are the main raw materials for these waste batteries, organic solvents, explosives, and heavy metals such as Ni, Co, Mn, and Fe are contained. However, Ni, Co, Mn, and Li have significant rarity value as valuable metals, and the recovery and reuse processes of lithium secondary batteries after they are discarded are emerging as an important research area.

[0003] Specifically, a lithium secondary battery mainly consists of copper and aluminum used as current collectors, Li, Ni, Co, and Mn-containing oxides that constitute the positive electrode material, and graphite used as the negative electrode material. It also includes a separator plate that separates the positive and negative electrode materials and an electrolyte injected into the separator plate. The solvent and salt used to constitute the electrolyte are mainly a mixture of carbonate organic materials such as ethylene carbonate and propylene carbonate, for example, LiPF6 is used.

[0004] In order to utilize the aforementioned waste batteries, there is active development of waste battery recycling processes that involve crushing the waste batteries to produce intermediate materials such as waste battery crushed material or black powder, and then recovering valuable metals through subsequent processes.

[0005] However, in the aforementioned waste battery recycling process, although there are differences depending on the number of times the battery has been used and its condition, generally the waste battery has a voltage in the range of 3.0 to 3.2V when fully discharged on a cell-by-cell basis and a voltage close to 4V when fully charged. Modules and packs in which tens to hundreds of cells are linked together have very large amounts of energy in such residual voltages, so when waste batteries are physically disassembled by applying external shock, safety issues related to battery explosion and electric shock arise.

[0006] To prevent this, after the disassembly, holes are created in the battery and discharge is performed using salt water. After the discharge is complete, the battery undergoes a crushing stage and then high-temperature heat treatment to remove water and electrolyte.

[0007] At this time, the salt used in the saltwater discharge contains large amounts of substances such as Na, K, Cl, Mg, and Ca. Of the aforementioned substances, Cl in particular is partially removed during the high-temperature heat treatment process, but the crushed waste battery material and the black powder, which is a powder in which Al, Cu, and Ni-Co-Mn-Li-O oxide with C are mixed after further processing of the crushed material and a portion of the separation membrane are removed, contain impurities such as Na, K, and Mg.

[0008] The aforementioned impurities cause a problem in the extraction process using acid leaching in the later stages of the waste battery recycling process, which reduces the recovery rate. Therefore, research is needed on methods to solve this problem. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] One embodiment of the present invention provides crushed unit batteries with low impurity content and fire prevention through the recycling of waste batteries.

[0010] The present invention provides a battery shredder that has the aforementioned advantages and includes at least one or more unit battery shredders.

[0011] Another embodiment of the present invention provides a battery processing method that can stably process waste batteries in a simple process without explosion or fire. [Means for solving the problem]

[0012] According to one embodiment of the present invention, the unit battery shredder is a unit battery shredder for recovering valuable metals from waste batteries, wherein the unit battery shredder has a layered structure including a separation membrane on which a positive electrode or a negative electrode is laminated on at least one surface, and can satisfy the following conditions 1 and 2. <Condition 1> The layered structure is a laminated structure consisting of 1 to 7 layers. <Condition 2> The size of the unit battery shredded material is 100 mm or less, with respect to the longest axis among the horizontal, vertical, and height directions.

[0013] In one embodiment, the surface of the crushed unit battery includes a burnt portion, which is a region where at least a part of the surface has been burned, and a normal portion, which is free from burn marks, and the area ratio of the burnt portion to the normal portion may be 30% or less. In one embodiment, the burnt portion can be formed on the edge of the surface.

[0014] A battery shredder according to another embodiment of the present invention may include a battery shredder comprising at least one of the aforementioned unit battery shredders.

[0015] In one embodiment, the content of the unit battery fragment may be 90% or more of the total volume of the battery fragment. In one embodiment, the battery fragment may contain impurities of the following weight percent: Na: 0.4% or less, Ca: 0.03% or less, Mg: 0.02% or less, and K: 0.02% or less.

[0016] According to still another embodiment of the present invention, a battery treatment method comprises a step of freezing a battery;

[0017] a step of crushing the frozen battery to obtain crushed battery material; and a step of stabilizing the crushed battery material using a cooling fluid, wherein the crushed battery material includes at least one unit crushed battery piece, the unit crushed battery piece has a layered structure including a separation membrane having a positive electrode or a negative electrode laminated on at least one surface thereof, and can satisfy the following condition 1 and condition 2. <Condition 1> The layered structure is a laminated structure of 1 layer or more and 7 layers or less. <Condition 2> Based on the long axis which is the longest axis among the transverse, longitudinal and height directions, the size of the unit crushed battery piece is 100 mm or less.

[0018] In one embodiment, the crushing step may include a step of controlling the proportion of the unit crushed battery pieces to 90% or more of the total volume of the crushed battery material. In one embodiment, the step of freezing the battery can satisfy the following formula 1. <Formula 1> Minimum cooling time (Hr)=A×(W 0.33 ) (A=4×e (-0.02×dT) , W=battery weight (Kg), dT=|external cooling temperature - target temperature|, || means an absolute value)

[0019] In one embodiment, the freezing step can be performed by cooling at -150°C to -20°C. In one embodiment, the step of stabilizing the crushed battery material using a cooling fluid can be performed under a condition of 15 to 40°C.

[0020] In one embodiment, the cooling fluid can be at least one of air, vacuum, nitrogen, inert gas, and water. In one embodiment, when the cooling fluid is a gas, the stabilization average time can satisfy the following equation 2. <Expression 2> B = 0.0125A 2 +2.6979A+170.9±100 (In formula 2 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

[0021] In one embodiment, when the cooling fluid is a liquid, the stabilization average time can satisfy the following equation 3. <Expression 3> B = -0.0007A 2 +0.3246A+37.07±50 (In formula 3 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

[0022] In one embodiment, the freezing step can be carried out by cooling at -60°C to -20°C, and the crushing step can be carried out under a vacuum atmosphere of 100 torr or less. In one embodiment, the recovery time required to lower the temperature of the crushed battery material to a range of 20 to 50°C in the crushing step may be 200 minutes or less. In one embodiment, after the crushing step, the process may further include a step of magnetic separation or specific gravity separation to separate products with a maximum size of 1 mm or less. [Effects of the Invention]

[0023] According to one embodiment of the present invention, a valuable metal alloy can be provided with a low impurity content and fire-preventing crushed unit battery material by freezing the waste battery at a predetermined temperature and then crushing it.

[0024] According to another embodiment of the present invention, a battery shredder can be provided that has at least one unit battery shredder having the aforementioned advantages.

[0025] According to another embodiment of the present invention, a battery recycling method can be provided that prevents the flammable substance in the electrolyte from reacting with oxygen by going through the steps of freezing the waste battery at a predetermined temperature and then crushing it. [Brief explanation of the drawing]

[0026] [Figure 1] This shows the change in battery voltage due to cooling temperature according to one embodiment of the present invention. [Figure 2] This graph shows the relationship between battery weight, external cooling temperature, and cooling time according to one embodiment of the present invention. [Figure 3a] This is a photograph of an example demonstrating the minimum cooling time of the present invention. [Figure 3b] This is a photograph of an example demonstrating the minimum cooling time of the present invention. [Figure 3c] This is a photograph of a comparative example using the minimum cooling time of the present invention. [Figure 3d] This is a photograph of a comparative example using the minimum cooling time of the present invention. [Figure 4] This is a temperature graph of crushed material over time, according to one embodiment of the present invention. [Figure 5a] The following shows a unit battery fragment according to one embodiment of the present invention and a comparative example. [Figure 5b] This shows the mixing ratio by weight ratio of battery fragments according to one embodiment of the present invention. [Figure 5c] This shows the burnt and normal areas on the surface of the crushed unit battery. [Figure 6a] This graph shows the stabilization time when battery fragments are stabilized with a gaseous cooling fluid according to one embodiment of the present invention. [Figure 6b] This graph shows the stabilization time when battery fragments are stabilized with a liquid cooling fluid according to one embodiment of the present invention. [Modes for carrying out the invention]

[0027] The terms First, Second, and Third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the First Part, component, region, layer, or section described below may be referred to as the Second Part, component, region, layer, or section without departing from the scope of the present invention.

[0028] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the phrase expressly indicates otherwise. The meaning of “including” as used in this specification embodies certain characteristics, domains, integers, stages, operations, elements, and / or components, and does not exclude the presence or addition of other characteristics, domains, integers, stages, operations, elements, and / or components.

[0029] When one part is described as being "on top of" or "on" another part, it may be directly on top of or on the other part, or the other part may be present between them. In contrast, when one part is described as being "directly on top of" another part, there is no other part in between them.

[0030] Although not defined differently, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are interpreted in addition to having meanings that correspond to relevant technical documents and the content currently disclosed, and are not interpreted in their ideal or highly formal sense unless otherwise defined.

[0031] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and do not limit the present invention, which is defined solely by the scope of the claims described below.

[0032] One embodiment of the present invention provides a unit battery shredder for recovering valuable metals from waste batteries, and has a layered structure including a separation membrane on which a positive or negative electrode is laminated on at least one surface. Specifically, the layered structure may include a configuration in which a positive or negative electrode is included on one or both surfaces of the separation membrane, with the separation membrane as the reference point. More specifically, the number of layers in the layered structure may correspond to the number of separation membranes.

[0033] The layered structure includes, for example, one of the following: positive electrode-separator-negative electrode, positive electrode-separator, separation membrane-positive electrode, separation membrane-negative electrode, and negative electrode-separator. For example, positive electrode-separator-negative electrode-separator-positive electrode-separator-negative electrode can have a three-layered structure. Specifically, the unit battery shredded material can have a predetermined thickness in the thickness direction by stacking at least one layer.

[0034] In one embodiment, the unit battery shredder can satisfy the following condition 1. <Condition 1> The layered structure may be a laminated structure of 1 to 7 layers.

[0035] The unit battery shredder may have a layered structure having one to seven layers. Specifically, the layered structure may have one to five layers. By stacking the layered structure within the above range, the temperature rise of the shredder is minimized and the heating time is appropriate. If the layered structure is stacked thicker than the upper limit of the above range, the temperature rise increases excessively, the heating time also increases, and combustion occurs, which can cause a fire.

[0036] In one embodiment, the crushed unit battery can satisfy the following condition 2. <Condition 2> The size of the unit battery shredded material may be 100 mm or less, based on the longest axis among the horizontal, vertical, and height directions.

[0037] In one embodiment, the unit battery shredder may have a size of 100 mm or less with respect to its long axis. Specifically, the size of the unit battery shredder may be 50 mm or less. If the size of the unit battery shredder is excessively large, there is a high possibility that the temperature of the battery shredder itself will rise to 100°C or higher, causing a fire.

[0038] In one embodiment, the surface of the unit battery shredder may include a burnt area and a normal area. The burnt area means an area on the surface of the unit battery shredder in which at least a portion has been burned, and the normal area means a normal area on the surface in which there are no traces of burning.

[0039] In one embodiment, the area ratio of the burnt portion to the normal portion on the surface of the crushed unit battery can satisfy the condition of 30% or less. By satisfying the area ratio of the burnt portion to the normal portion of 30% or less, the possibility of the crushed unit battery burning and causing a fire can be prevented. If the area ratio of the burnt portion to the normal portion exceeds 30%, there is a risk that the crushed unit battery will burn and cause a fire accompanied by smoke.

[0040] In one embodiment, the combustion portion may be located at the edge of the surface of the unit battery shredder. The normal portion may be located near the center of the surface of the unit battery shredder. The combustion portion refers to an area that exhibits a darker color compared to the normal portion.

[0041] In other embodiments of the present invention, the battery shredder may contain at least one of the aforementioned unit battery shredders. In one embodiment, the battery shredder may contain at least one of the unit battery shredders, which may make up 90% or more of the total volume of the battery shredder. Specifically, the content of the unit battery shredder may be 95% or more of the total volume of the battery shredder.

[0042] Specifically, the proportion of unit battery fragments having a stacked structure exceeding seven layers in the battery fragments may be 10% or less, specifically 5% or less, of the total volume of the battery fragments, or the proportion of at least one unit battery fragment that exceeds 100 mm in size based on its long axis may be 10% or less, specifically 5% or less, of the total volume of the battery fragments.

[0043] In this way, fires can be prevented if the ratio of battery shreds having a layered structure with more than 7 layers per unit volume within the total volume of battery shreds, or the ratio of unit battery shreds with a size exceeding 100 mm based on their long axis, satisfies the aforementioned range.

[0044] In one embodiment, the battery shredder is recovered from a waste battery and contains impurities, which may include Na, Ca, Mg, and K in weight percent. The battery shredder may also be a shredded residue or black powder produced through a process of recovering and crushing the waste battery, which is a pretreatment process for the waste battery recycling process.

[0045] The battery fragments may contain impurities such as Na, Ca, Mg, and K. By reducing the content of these impurities, the battery fragments can facilitate the extraction of Li, a valuable metal of the same group, in subsequent processes.

[0046] According to one embodiment of the present invention, the battery shredded material contains impurities, which may include, in weight percent, Na: 0.4% or less (excluding 0%), Ca: 0.03% or less (excluding 0%), Mg: 0.02% or less, and K: 0.02% or less.

[0047] The reasons for limiting the content of the aforementioned impurities are explained below.

[0048] "Na: 0.4% by weight or less (0% excluded)" Sodium (Na) has the side effect of reducing lithium recovery or increasing costs in the causticization process by partially reacting with lithium in the lithium hydroxide formation process as a congener element in the subsequent process of recovering valuable metals from the battery waste, thereby forming sodium hydroxide instead of lithium. The battery waste may contain sodium in an amount of 0.4% by weight or less, specifically, the sodium may contain 0.1% by weight or less.

[0049] When the sodium content exceeds the aforementioned range, as the Na increases, there is a problem in which the actual yield decreases in the necessary steps when Na forms lithium carbonate as a group 1 element, the same as Li, during the crystallization process of Li dissolved in the solvent after the leaching and solvent extraction steps.

[0050] "Ca: 0.03% by weight or less (0% excluded)" Calcium (Ca), like sodium, is an element that reduces the recovery rate of valuable metals in the subsequent process of recovering valuable metals from the battery waste. When calcium forms lithium aluminate, it is more reactive than aluminum and forms a lithium calcinate structure, thereby hindering the formation of lithium aluminate, which is more reactive thereafter, and thus reducing the recovery rate of final lithium. The battery waste may contain calcium in an amount of 0.03% or less, specifically, calcium may be contained in an amount of 0.02% by weight or less.

[0051] If the calcium content exceeds the aforementioned range, when Ca increases, there is a problem in that the actual yield and process time increase in the solid-liquid separation process, which is an impurity purification process, after the leaching process. Also, if the calcium content is excessively high, when nickel, cobalt, manganese hydroxide, and lithium hydroxide, which are in a precursor state, are synthesized to produce the cathode material, Li[NiCoMn] 1-x Ca x )]When synthesized as O2, the potassium constitutes the cathode material oxide structure, which hinders the movement of lithium ions and causes a problem in which the battery capacity is reduced.

[0052] "Mg: 0.02% by weight or less" Magnesium (Mg) is an element that makes it difficult to separate the solid and liquid phases during acid leaching in the valuable metal recovery process. The crushed battery material may contain magnesium in an amount of 0.02% by weight or less, specifically 0.01% by weight or less.

[0053] If the magnesium content exceeds the aforementioned range, it creates a problem of burdening the recovery process for nickel, cobalt, lithium, etc. Furthermore, if the magnesium content is excessively high, when synthesizing it with precursor nickel, cobalt, manganese hydroxide, and lithium hydroxide to produce a cathode material, Li[NiCoMn] 1-x Mg x )]It is synthesized as O2, which forms a positive electrode oxide structure that hinders lithium ion movement and reduces battery capacity.

[0054] "K: 0.02% by weight or less" Potassium (K), being a congener of lithium, also plays a role in inhibiting the formation of lithium hydroxide. The battery fragments may contain potassium in an amount of 0.02% by weight or less, specifically 0.01% by weight or less. If the potassium content exceeds this range, it can cause a load during the causticization process, reducing the lithium recovery rate.

[0055] A battery processing method according to another embodiment of the present invention includes the steps of freezing a battery, crushing the frozen battery, and stabilizing the crushed battery using a cooling fluid. The battery processing method may also be a method for processing various types of batteries, including lithium-ion batteries, where the battery may be, for example, a lithium secondary battery separated from an automobile, or a secondary battery separated from an electronic device such as a mobile phone, camera, or laptop computer, specifically a lithium secondary battery.

[0056] In one embodiment, the step of freezing the battery can satisfy the following Formula 1. <Formula 1> Minimum cooling time (Hr)=A×(W 0.33 ) (A=4×e (-0.02×dT) , W=battery weight (Kg), dT=|external cooling temperature - target temperature|, || means absolute value)

[0057] W in the above Formula 1 means the weight of the battery, for example, the weight for a battery pack, a single battery, or a combination thereof. The minimum cooling time is an external cooling temperature which is a cooling temperature applied to the battery, and refers to, for example, a target temperature for cooling an electrolyte in the battery.

[0058] The step of freezing the battery is performed for a time not less than the minimum cooling time, which has the advantage that the electrolyte inside the battery is also cooled, allowing subsequent processes to be stably performed. If the step of freezing the battery freezes the battery for a time shorter than the minimum cooling time, there is a problem that the electrolyte is not cooled, which may cause a risk of fire during crushing.

[0059] The step of freezing the battery is performed at a temperature sufficient to freeze the electrolyte contained in the battery. Specifically, the freezing step can be performed, for example, in a temperature range of -150°C to -20°C. More specifically, the temperature range can be -150°C to -50°C, and even more specifically, the step can be performed in a temperature range of -80°C to -60°C.

[0060] When the battery is frozen within the aforementioned temperature range, the voltage remaining inside the battery, for example, approximately 2V to 3V, drops to near 0V. Therefore, even if a short circuit occurs where the positive and negative electrodes come into direct contact, no battery reaction occurs, the battery temperature does not rise, and thus no gas generation or combustion of the electrolyte occurs. Furthermore, because the electrolyte is frozen or its vaporization is suppressed, the mobility of lithium ions is very low, and the current-carrying characteristics due to lithium ion movement are significantly reduced. As a result, no vaporization of the electrolyte occurs, and therefore no flammable gases of ethylene, propylene, and hydrogen are generated.

[0061] If the freezing process deviates from the temperature range, for example, if the battery is cooled to a temperature higher than -60°C, the voltage remaining inside the battery will not drop to 0V, which may cause a battery reaction due to a short circuit, and the electrolyte will not be completely frozen, making it unsuitable. On the other hand, if the battery is cooled to -150°C, the electrolyte will be sufficiently frozen and the internal voltage of the battery will drop to 0V, so there is no need to lower the temperature any further. Thus, the battery processing method has the advantage of preventing the risk of fire that may occur in the battery crushing process by including a freezing step before crushing batteries such as lithium secondary batteries.

[0062] The step of crushing the frozen battery may mean a step of applying shock or pressure to the battery so that a part of the battery falls off. In one embodiment, the step of crushing the battery may mean a step of pulverizing the battery, a step of cutting the battery, a step of compressing the battery, and a combination thereof. Specifically, the crushing step may include all steps of destroying the battery to obtain small fragments.

[0063] In one embodiment, the step of crushing the battery may include all steps of compressing the frozen battery or destroying the battery by applying an external force such as shear force or tensile force. The step of crushing the battery may be carried out, for example, using a crusher.

[0064] In one embodiment, the step of crushing the battery can be performed at least once. Specifically, the crushing step can be performed at least once, either continuously or discontinuously.

[0065] In one embodiment, the battery crushing step can be carried out under conditions of supplying an inert gas, carbon dioxide, nitrogen, water, or a combination thereof, or under a vacuum atmosphere of 100 torr or less. For example, when the battery freezing step is carried out by cooling in a temperature range of -60 to -20°C, carrying it out under the aforementioned conditions can suppress oxygen supply, prevent the electrolyte from reacting with oxygen, prevent explosions, suppress the vaporization of the electrolyte, and prevent the generation of flammable gases such as ethylene, propylene, or hydrogen.

[0066] In one embodiment, at least one of the unit battery fragments contained within the battery fragments can satisfy the following condition 1.

[0067] <Condition 1> The aforementioned layered structure may consist of one to seven layers.

[0068] Condition 1 above can mean that the layered structure of the unit battery shredder, which includes a separation membrane on which a positive or negative electrode is laminated on at least one surface, is controlled to be shredded into a layered structure of 1 to 7 layers.

[0069] In one embodiment, the layered structure may be a laminated structure of 1 to 7 layers. Specifically, the layered structure may be a laminated structure of 1 to 5 layers. By laminating the layered structure within the above range, the temperature rise of the crushed material is minimized and the heating time is appropriately controlled. If the layered structure is laminated to a thickness exceeding the upper limit of the above range, the temperature rise increases excessively, and the heating time also increases, leading to the problem of combustion.

[0070] In one embodiment, at least one of the unit battery fragments contained within the battery fragments can satisfy the following condition 2.

[0071] <Condition 2> The size of the unit battery shredded material may be 100 mm or less, with respect to the longest axis among the horizontal, vertical, and height directions.

[0072] In one embodiment, the size of the unit battery shredded material, specifically the longest axis among the horizontal, vertical, and height directions, can be controlled during the shredding stage to be 100 mm or less, specifically 50 mm or less. If the maximum size of the battery shredded material is greater than 100 mm, the heat generated due to instability caused by the shredding of the battery shredded material may rise to the 120°C temperature range, which is the average vaporization temperature of the electrolyte, potentially causing stability problems such as fire.

[0073] In one embodiment, the step of crushing the battery may further include a step of controlling the proportion of the unit battery fragments to 90% or more, specifically 95% or more, of the total volume of the battery fragments. Specifically, this may correspond to controlling the proportion of unit battery fragments having a stacked structure with more than 7 layers to 10% or less of the total volume of the battery fragments. Specifically, the proportion of unit battery fragments having a stacked structure with more than 7 layers can be controlled to 5% or less of the total volume of the battery fragments. Satisfying the above range has the advantage of preventing fire.

[0074] In one embodiment, the recovery time required to lower the temperature of the crushed battery material to a range of 20-50°C during the crushing stage may be 200 minutes or less. Specifically, the recovery time required to lower the temperature of the crushed battery material to a range of 35-45°C may be 200 minutes or less.

[0075] In one embodiment, the step of stabilizing the crushed battery material using a cooling fluid can be performed in a temperature range of -20 to 80°C. If the step is performed outside the lower temperature limit, additional equipment is required to maintain the temperature, which is uneconomical. If the step is performed outside the upper temperature limit, the instability of the battery material against fire cannot be eliminated.

[0076] In one embodiment, the step of stabilizing the crushed battery fragments using a cooling fluid can be performed in a range of 30 minutes to 10 hours, depending on the type of cooling fluid. If the time exceeds the lower limit of the above time range, there is a problem of fire occurring due to reheating, and if it exceeds the upper limit of the above time range, there is a problem of decreased production volume due to increased process time.

[0077] In one embodiment, the step of stabilizing the crushed battery fragments using a cooling fluid can be at least one of air, vacuum, inert gas, nitrogen, or water. Stabilizing the battery fragments using the aforementioned cooling fluid has the advantage of obtaining battery fragments with a low Na content among the impurities in the battery fragments. It can be observed that the time required for stabilization is longer when using a gaseous or vacuum atmosphere than when using a liquid.

[0078] In one embodiment, when the battery processing method is performed using a gas as the cooling fluid, the stabilization average time can satisfy the following equation 2.

[0079] <Expression 2> B = 0.0125A 2+2.6979A+170.9±100 (In formula 2 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

[0080] In one embodiment, when the battery processing method is performed using a liquid cooling fluid, the stabilization average time can satisfy the following equation 3.

[0081] <Expression 3> B = -0.0007A 2 +0.3246A+37.07±50 (In formula 3 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

[0082] The aforementioned stabilization average time is the time (in minutes) it takes for the battery fragments to cool down to room temperature after their temperature rise, and represents the average time relative to the maximum and minimum times. Specifically, Equation 2 has a lower limit of 0.0125A. 2 +2.6979A + 70.9 and an upper limit of 0.0125A 2 This can satisfy the range of +2.6979A+270.9. Equation 3 has a lower limit of B = -0.0007A 2 +0.3246A - 12.93 and upper limit B = -0.0007A 2 This can satisfy the range of +0.3246A+87.07.

[0083] The battery processing method of the present invention has the advantage of reducing the possibility of fire in the crushed material by appropriately maintaining the stabilization of the crushed material according to its size, by satisfying Equations 2 and 3, respectively, when the stabilization step is performed with a gas or a liquid.

[0084] In one embodiment, a further step can be taken to separate the crushed product from the product having a maximum size of 1 mm or less. This separation step can be carried out by magnetic separation or specific gravity separation, and any separation process widely known in the field is acceptable. By thus carrying out the separation step, a powder containing a mixture of positive electrode active material, negative electrode active material, positive electrode current collector, and negative electrode current collector can be obtained. In another embodiment, after carrying out the crushing step, a step of removing and separating the electrolyte can also be carried out. This electrolyte removal step can be performed by heat treatment of the crushed product or by vacuum drying.

[0085] The following describes preferred embodiments and comparative examples of the present invention. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to these embodiments. [Examples]

[0086] <Battery internal temperature based on minimum freezing time> The battery pack used in the embodiment was not frozen, and was crushed using the same crusher as in the embodiment. During the crushing process, flames were generated due to a short circuit, as shown in Figures 3a and 3b.

[0087] Thus, through the examples and comparative examples, it can be confirmed that by including a step of freezing the battery pack containing the battery before crushing the battery, no short circuits or flames occur during the battery crushing stage, resulting in excellent stability.

[0088] Figure 1 shows the change in battery voltage due to cooling temperature in one embodiment of the present invention.

[0089] Referring to Figure 1, measuring the battery voltage while freezing the battery at -80°C confirms that the battery pack exhibits almost identical voltages up to approximately 40°C, room temperature, and -60°C, thus demonstrating that it does not lose its battery characteristics. Next, when the temperature decreases from -60°C to -70°C, the voltage drops sharply, and it was confirmed that the voltage becomes 0 at -70°C. Thus, it was confirmed that no short circuit occurs when freezing the battery at -60 to -150°C.

[0090] Figure 2 is a graph showing the relationship between battery weight, external cooling temperature, and cooling time according to one embodiment of the present invention.

[0091] Referring to Figure 2, it can be confirmed that the battery processing method according to one embodiment of the present invention allows for the derivation of the minimum cooling time required to cool the battery during the battery freezing stage. Specifically, it can be confirmed that the minimum cooling time is related to the battery weight, the external cooling temperature, and the target temperature. Specifically, the external cooling temperature and minimum cooling time are shown when the target temperature is set to -70°C and the battery weights are 2.5 kg (A), 10 kg (B), 20 kg (C), and 50 kg (D), respectively. When the battery is cooled, it can be confirmed that the electrolyte of the battery starts to cool and the voltage drops to 0 after a predetermined time. This confirms that a minimum maintenance time is required to sufficiently cool the inside of the battery, specifically the electrolyte, when cooling the battery.

[0092] Specifically, when considering the specific heat of the battery itself in the heat transfer situation for cooling, where heat is removed to the outside, it can be confirmed that the battery weight and the time required for cooling are necessary. Thus, in this invention, the minimum time required for cooling the battery can be determined using the external cooling temperature for freezing, the target temperature, and the battery weight.

[0093] Table 1 below lists the minimum cooling time based on battery weight and external cooling temperature.

[0094] [Table 1]

[0095] Table 1 above shows that the smaller the battery weight, the shorter the minimum cooling time required for the battery to be cooled. Furthermore, when the battery is cooled for the minimum time according to the value of Equation 1 derived from the relationship between battery weight, external cooling temperature, and target temperature, it can be confirmed that the battery, specifically the electrolyte of the battery, is cooled. In addition, when the battery is cooled for a time longer than the value of Equation 1, no fire occurs in the subsequent battery crushing process. Figures 3a and 3b are photographs of an example using the minimum cooling time of the present invention, and Figures 3c and 3d are photographs of a comparative example using the minimum cooling time of the present invention.

[0096] Referring to Figures 3a and 3b, an experiment was conducted to determine the fire-causing state of crushed materials when a battery was frozen for a shorter time than the minimum required cooling time. In the experiment, with a battery weight of 25 kg, an external cooling temperature of -95°C, and a target freezing temperature of -70°C, when the value of Equation 1 below was 7 hours, the experiment was conducted for a shorter time of 5 hours.

[0097] <Expression 1> Minimum cooling time=A×(W 0.33 ) (A=4×e (-0.02×dT) W = Battery weight (kg), dT = |External cooling temperature - Target temperature|, || represents the absolute value)

[0098] Referring to Figures 3c and 3d, these figures show the experimental results of fire outbreaks in crushed materials when a battery is frozen for a period exceeding the minimum freezing time required for cooling. In these experiments, the same battery weight, external cooling temperature, and minimum freezing time as in Figures 3a and 3b were used, but with a minimum freezing time of 7 hours or more.

[0099] Table 2 below compares the fire occurrence conditions of the examples and comparative examples, based on 3a to 3d, with identical battery weight, external cooling temperature, and minimum freezing time. The fire occurrence conditions were classified as "O" if a fire was observed after battery crushing, and "X" otherwise.

[0100] [Table 2]

[0101] As can be seen in Table 2 above, when the battery is cooled for a time smaller than the value in Equation 1 which corresponds to the minimum cooling time, the electrolyte is not cooled, and a fire occurs after the battery is crushed. Thus, when the value in Equation 1 is used as the minimum cooling time for cooling the battery, it can be confirmed that the crushed material can be used stably without a fire occurring after the battery is crushed.

[0102] <Battery shredding stage - size of shredded material> Even if a refrigerated battery is crushed, the likelihood of a fire occurring during the crushing process is low. However, the battery's charge state will create a potential difference within the crushed material. In this invention, a standard for stabilizing the crushed material is established by measuring how high its temperature rises.

[0103] Figure 4 is a temperature graph of crushed material over time, according to one embodiment of the present invention.

[0104] Figure 4 shows the temperature change over time to determine the maximum exothermic temperature, using a 20mm-sized fragment as a reference. Specifically, after crushing a battery that had undergone a refrigeration stage, the temperature change over time was measured by placing a 20mm-sized fragment in the atmosphere and using an air-cooling method. For a 20mm-sized fragment, it can be confirmed that the maximum ignition temperature is approximately 65°C. This is lower than the average vaporization temperature of the electrolyte, which is 120°C.

[0105] Table 3 below shows the temperature increase measured according to the size of the crushed material.

[0106] [Table 3]

[0107] Table 3 above shows that the reheating temperature differs depending on the size of the crushed material, and it was confirmed that at the stabilization temperature for process design, the average size of the crushed material must be such that the longest axis (the longest of the horizontal, vertical, and height directions) is within 100 mm.

[0108] <Battery shredding stage - size of shredded material> Furthermore, depending on the size of the crushed material, it requires time for the material to physically stabilize. To stabilize the crushed material, it is necessary to maintain a temperature below 120°C for a predetermined process time, or to maintain it for a predetermined process time with an inert gas introduced to reduce contact with oxygen in the atmosphere.

[0109] In this invention, the average crushed material size is 20 mm, and the temperature is maintained at room temperature (30°C) for about 3 hours. During this time, it can be confirmed that the temperature of the crushed material has dropped back down to room temperature.

[0110] For crushed materials of 100 mm or less, the stabilization time can be kept for a few minutes without issue. However, for crushed materials exceeding 100 mm, a minimum stabilization time of 3 hours or more is required.

[0111] <Battery shredding stage - Shredded material layer control stage of battery shredder> When crushing is performed for a period shorter than the minimum freezing time for the crushed material, problems arise where the crushed material does not undergo brittle fracture at extremely low temperatures, resulting in large fragment sizes, or where the thickness of the crushed material increases due to the presence of multiple layers of positive and negative electrode current collectors. The increased thickness of the crushed material layers leads to a large temperature rise and a long heating time.

[0112] Table 4 below shows the temperature rise due to the layered structure in a unit battery fragment according to one embodiment of the present invention, as measured by a thermal imaging camera.

[0113] Referring to Table 4 below, in the case of a layered structure, the positive electrode-separator membrane-negative electrode constitutes one layer, and when the crushed material is stacked in multiple layers, it is arranged in the order of positive electrode-separator membrane-negative electrode-separator membrane-positive electrode-separator membrane-negative electrode... Specifically, it means that the separator membrane structure is arranged in multiple layers with one layer between the positive electrode or the negative electrode inside the waste battery. Specifically, it may also be the case that the positive electrode or negative electrode is arranged on at least one surface of the separator membrane, with the separator membrane as the reference point.

[0114] Table 4 below shows the average size of the crushed material, evaluated as 20 mm, and the temperature evaluation of the crushed material by layer after crushing, as well as the recovery time required for the temperature to rise from the freezing temperature to the maximum temperature and then drop back down to 40°C.

[0115] In this case, the size of the crushed material was measured based on the longer axis of the crushed material, which is one of the two axes of the crushed material.

[0116] [Table 4]

[0117] Figures 5a to 5c show crushed unit batteries according to one embodiment of the present invention and comparative examples. Referring to Figure 5a, examples and comparative examples can be seen in terms of the size of the crushed unit batteries and the number of layers in the layered structure.

[0118] Looking at Figure 5a and Table 4 together, it was confirmed that when the number of layers in the layered structure is three or less, the temperature of the crushed material is stably maintained at 110°C or below, and when there are more than seven layers, the temperature rises above 105°C before combustion occurs due to a reaction with the electrolyte.

[0119] Referring to Figure 5b, the mixing ratio based on the weight ratio of the crushed battery material can be confirmed. Specifically, the weight of the crushed battery material with a layered structure of 7 layers or less (left side of Figure 5b) was 905g, and the weight of the crushed battery material with a layered structure exceeding 7 layers (right side of Figure 5b) was 95g, which was used in the mixing.

[0120] We confirmed that, in the case of a single layer of crushed battery material, if the size exceeds 100 mm, the maximum temperature rises above 105°C, significantly increasing the likelihood of fire. We also confirmed that even if the size is less than 100 mm, if the number of layers in the layered structure is 10 or more, specifically more than 7, the likelihood of fire increases significantly.

[0121] Table 5 below shows the likelihood of fire occurring in the battery shredded material of the present invention, based on the weight percentage ratio of shredded material with more than 7 layers of layered structure.

[0122] [Table 5]

[0123] As shown in Table 5 above, the results of measuring the frequency of fire occurrences in the crushed material several times per 1 kg cell unit confirmed that when the weight ratio of crushed material with more than 7 layers of layered structure was 10% or less of the total weight ratio, fire occurrences were almost nonexistent. On the other hand, when the weight ratio of crushed material with more than 7 layers of layered structure exceeded 10% of the total weight ratio, fires occurred in all three experiments. In this case, it was confirmed that the ignition point of the fires started from the crushed material with 7 or more layers. Thus, it was confirmed that when the weight ratio of crushed material with more than 7 layers of layered structure is 10% or less of the total weight of the crushed material, specifically 5% or less, fires in the crushed material can be prevented, and that when more than 10% of the total battery crushed material consists of crushed material with 7 or more layers of layered structure or crushed material larger than 100 mm in size, the frequency of fire occurrences increases.

[0124] Furthermore, Table 6 below shows the results of confirming the presence or absence of smoke generation based on the ratio of combustion traces on the surface of the crushed material according to one embodiment of the present invention.

[0125] [Table 6]

[0126] Figure 5c shows the burnt and normal areas on the surface of a crushed unit battery according to one embodiment of the present invention. Referring to Figure 5c, it can be seen that the surface of the crushed unit battery shows normal areas without traces of burning due to high temperature and areas with traces of burning due to high temperature. The burnt areas are areas with traces of burning due to high temperature, and may specifically be areas that were rapidly heated, and refer to areas that are darker in color compared to the normal areas which are unburnt parts. It can be seen that the edges of most of the burnt areas were burned.

[0127] Looking at Figure 5c and Table 6, it was confirmed that when there were almost no traces of high-temperature combustion on the surface of the crushed unit battery, or when the amount of combustion traces within the surface area was 30% or less, the presence or absence of smoke was evaluated and combustion did not occur. When the amount of combustion traces within the surface area exceeded 30%, it was confirmed that a fire accompanied by smoke occurred.

[0128] <Battery stabilization stages - stabilization time> Table 7 below shows the stabilization time depending on the type of cooling fluid and the size of the crushed material. Specifically, the stabilization time refers to the time (min) required for the crushed material to cool down to room temperature (30°C) after its temperature rise.

[0129] [Table 7]

[0130] Figure 6a is a graph showing the stabilization time when battery fragments are stabilized with a gaseous cooling fluid according to one embodiment of the present invention. Referring to Figure 6a, the stabilization time varies depending on the size of the fragments when a gas is used as the cooling fluid. Specifically, the average stabilization time of the gas is the average of the maximum and minimum times, and it can satisfy the aforementioned Equation 2.

[0131] Figure 6b is a graph showing the stabilization time when battery fragments are stabilized with a liquid cooling fluid according to one embodiment of the present invention.

[0132] Referring to Figure 6b, the stabilization time is shown for different sizes of crushed material when a liquid is used as the cooling fluid. Specifically, the average stabilization time of the liquid is the average of the maximum and minimum times, and it can satisfy Equation 3 mentioned above.

[0133] <Battery Stabilization Stage - Comparison of Components of Final Crushed Material> Table 8 below shows the Na content in impurities after a stabilization step using a cooling fluid. The cooling fluids refer to air, vacuum (1 torr), argon (Ar), nitrogen, tap water, saline solution with a concentration of 1% or less, saline solution with a concentration of 10% or less, and saline solution with a concentration of 15% or less.

[0134] [Table 8]

[0135] As can be seen in Table 8 above, in the cooling fluid test to stabilize the crushed material after cryopreservation, the impurity Na showed a low level of 0.054% in air, but when salt such as salt was included at a concentration of about 15%, it was confirmed that the Na level rose to 0.83%. This allows for the control of various impurities contained in salt. Table 9 below compares the Na, K, Mg, and Ca component values ​​of crushed material that underwent the stabilization step in air after cryopreservation (Example 1) and crushed material that was subjected to saltwater discharge in saltwater containing 15% salt (Comparative Example 1).

[0136] [Table 9]

[0137] As can be seen in Table 9 above, the battery fragments produced through the battery recycling method involving cryogenic crushing and stabilization have lower impurity content, specifically lower levels of Na, K, Mg, and Ca, compared to battery fragments produced by saltwater discharge.

[0138] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, using the basic concepts defined in the following claims, also fall within the scope of the present invention.

Claims

1. A unit battery shredder for recovering valuable metals from waste batteries, The aforementioned unit battery fragment has a layered structure including a separation membrane on which a positive or negative electrode is laminated on at least one surface, and satisfies the following conditions 1 and 2: The surface of the aforementioned unit battery shredded material is A combustion area in which at least a portion of the surface is a burned region, and The surface includes a normal portion without any traces of burning, A unit battery fragment in which the area ratio of the combustion part to the normal part is 30% or less. <Condition 1> The layered structure is a laminated structure consisting of one to seven layers. <Condition 2> The size of the unit battery shredded material is 100 mm or less, with respect to the longest axis among the horizontal, vertical, and height directions.

2. The unit battery shredded material according to claim 1, wherein the combustion portion is formed on the edge portion of the surface.

3. A battery shredder comprising at least one unit battery shredder according to claim 1 or 2.

4. The battery shredder according to claim 3, wherein the content of the unit battery shredder is 90% or more of the total volume of the battery shredder.

5. The battery crushed material according to claim 3, comprising impurities of the following weight percentages: Na: 0.4% or less (excluding 0%), Ca: 0.03% or less (excluding 0%), Mg: 0.02% or less (excluding 0%), and K: 0.02% or less (excluding 0%).

6. The stage of freezing the battery; A step of crushing the frozen battery as battery fragments; and The step includes stabilizing the crushed battery fragments using a cooling fluid, The aforementioned battery shredder includes at least one unit battery shredder. The unit battery fragment has a layered structure including a separation membrane on which at least one side has either a positive or negative electrode. The surface of the aforementioned unit battery shredded material is A combustion area in which at least a portion of the surface is a burned region, and The surface includes a normal portion without any traces of burning, The area ratio of the combustion section to the normal section is 30% or less. A battery processing method that satisfies the following conditions 1 and 2. <Condition 1> The aforementioned layered structure is a laminated structure consisting of one to seven layers. <Condition 2> The size of the unit battery shredded material is 100 mm or less, with respect to the longest axis among the horizontal, vertical, and height directions.

7. The battery processing method according to claim 6, wherein the crushing step includes a step of controlling the ratio of the unit battery crushed material to 90% or more of the total volume of the battery crushed material.

8. The battery processing method according to claim 6, wherein the step of freezing the battery satisfies the following formula 1. <Formula 1> Minimum cooldown time (Hr) = A × (W) ０．３３ ) (A = 4 × e （－０．０２×ｄＴ） W = Battery weight (kg), dT = |External cooling temperature - Target temperature|, || represents absolute value)

9. The battery processing method according to claim 6, wherein the freezing step is carried out by cooling at -150°C to -20°C.

10. The battery processing method according to claim 6, wherein the step of stabilizing the crushed battery material using a cooling fluid is performed at a temperature of 15 to 40°C.

11. The battery processing method according to claim 6, wherein the cooling fluid is at least one of air, vacuum, nitrogen, inert gas, and water.

12. The battery processing method according to claim 6, wherein when the cooling fluid is a gas, the stabilization average time satisfies the following equation 2. <Formula 2> B=0.0125A ２ +2.6979A+170.9±100 (In formula 2 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

13. The battery processing method according to claim 6, wherein, when the cooling is performed by a liquid, the stabilization average time satisfies the following equation 3. <Formula 3> B=-0.0007A ２ +0.3246A+37.07±50 (In formula 3 above, A represents the size of the crushed material [mm], and B represents the stabilization time [min].)

14. The aforementioned freezing step is carried out by cooling at -60°C to -20°C. The battery processing method according to claim 6, wherein the crushing step is carried out under a vacuum atmosphere of 100 torr or less.

15. The battery processing method according to claim 6, wherein the recovery time required to lower the crushed battery material to a temperature range of 20 to 50°C during the crushing stage is 200 minutes or less.

16. The battery processing method according to claim 6, further comprising a step of magnetic separation or specific gravity separation to separate products having a maximum size of 1 mm or less after the crushing step.

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