Lithium compound for recovering valuable metals and method for producing the same

Abstract

The present invention relates to a lithium compound for valuable metal recovery and a recovery method thereof. The recovery method for the lithium compound for valuable metal recovery includes the steps of preparing a battery, freezing and forcibly discharging the battery, crushing the battery, and heating the crushed battery material. The heating step is performed at a temperature of 1,100 to 1,400°C, and the degree of vacuum (LogP [atm]) during the heating step is performed in a range of -4 to 0. The lithium compound recovered through the heating step contains impurities, which may include, by weight, Na: 1.8 wt% or less (excluding 0 wt%), K: 0.06 wt% or less (excluding 0 wt%), Ca: 0.62 wt% or less (excluding 0 wt%), and Mg: 0.47 wt% or less (excluding 0 wt%).

Description

[Technical Field]

[0001] The present invention relates to waste batteries, and more particularly to a lithium compound for recovering valuable metals recovered from reused waste batteries, and a method for producing the same. [Background technology]

[0002] As demand for electric vehicles grows worldwide, the disposal of waste batteries from these vehicles is becoming a social issue. Lithium secondary batteries, which are the main raw materials for such waste batteries, contain organic solvents, explosive materials, and heavy metals such as Ni, Co, Mn, and Fe. Ni, Co, Mn, and Li are highly valuable as valuable metals, and therefore, the recovery and reuse process of discarded lithium secondary batteries has emerged as an important research field.

[0003] Specifically, a lithium secondary battery mainly comprises copper and aluminum used as a current collector, an oxide containing Li, Ni, Co, and Mn that constitutes the cathode material, and graphite used as the anode material, a separator that separates the cathode material from the anode material, and an electrolyte that is poured into the separator. The solvent and salt that constitute the electrolyte are typically a mixture of carbonate organic compounds such as ethylene carbonate and propylene carbonate, e.g., LiPF6.

[0004] In order to utilize the waste batteries, there has been growing interest in a waste battery recycling process in which the waste batteries are crushed to generate intermediate materials such as waste battery crushed material or black powder, and valuable metals are recovered through a post-process.

[0005] Specifically, the main components of waste batteries are expensive, valuable metal elements such as Ni, Co, Mn, and Li. These waste batteries are, for example, secondary batteries that have reached the end of their lifespan after being used for 5 to 10 years. Reusing the main components of these waste batteries is essential for environmental and cost reasons. These waste batteries undergo conventional crushing, pulverization, or gravity separation processes to produce a mixture of cathode and anode materials in the form of black powder, an intermediate product. The valuable metals essential for battery production are recovered from the black powder through wet processes such as leaching, solvent extraction, or crystallization. This facilitates the supply and demand of raw materials and dramatically reduces battery manufacturing costs.

[0006] In order to reuse waste batteries, they must be physically disassembled, which is a very dangerous process as it involves safety concerns such as battery explosion and electric shock. After physical disassembly, the battery is punctured and discharged in salt water. After discharge is complete, the battery is crushed and subjected to high-temperature heat treatment to remove water and electrolyte.

[0007] When discharging saltwater, the salt used contains large amounts of impurities such as Na, K, Mg, and Ca, which are present in the waste batteries. In the case of Cl, a certain amount is removed by high-temperature heat treatment, but crushed waste batteries and black powder made from crushed batteries contain impurities such as Na, K, and Mg.

[0008] The crushed material is obtained by crushing batteries in the same way, and the black powder is a powder form obtained by further processing the crushed material to remove Al, Cu, and part of the separator, and is a mixture of Ni-Co-Mn-Li-O oxide and C. When the crushed waste battery material is heat-treated at high temperature, oxygen is removed from the oxide, and Ni-Co-Mn-Cu alloy, lithium-containing compounds, carbon, and carbon-containing ash are produced.

[0009] In this case, impurities Na, K, and Mg contained in saltwater discharge during the wet treatment process of lithium-containing compounds act as impurities during wet treatment, and among these, Na, K, Mg, and Ca cause process loads when they go through a process similar to causticization (NaOH) used in wet recovery of Li, increasing processing time and costs. Also, in the case of Cl, corrosion of pipes that process chloride ions increases, resulting in problems such as increased equipment and maintenance costs. Summary of the Invention [Problem to be solved by the invention]

[0010] The lithium compound for valuable metal recovery according to one embodiment of the present invention increases the operating efficiency of the wet process, reduces the equipment maintenance cost, and provides a lithium compound component with a low impurity content.

[0011] A method for producing lithium compounds for valuable metal recovery according to another embodiment of the present invention provides a method for producing lithium compounds having the aforementioned advantages. [Means for solving the problem]

[0012] According to one embodiment of the present invention, the lithium compound is a lithium compound for recovering valuable metals recovered from waste batteries, and includes Li, Al, and impurities, which include, in weight percent, Na: 1.8 wt% or less (excluding 0 wt%), K: 0.06 wt% or less (excluding 0 wt%), Ca: 0.62 wt% or less (excluding 0 wt%), and Mg: 0.47 wt% or less (excluding 0 wt%), and can satisfy the following formula 1. <Expression 1> <al> / ≦1.30 ( <al>and< / al> (The numbers mean the number of moles of Al and Li, respectively.)

[0013] In one embodiment, the lithium compound may satisfy the following formula 2: <Expression 2> ([Na] + [K] + [Mg]) / [Ca]≦3.6 ([Na], [K], [Mg], and [Ca] mean the weight percentages of Na, K, Mg, and Ca, respectively.)

[0014] In one embodiment, the lithium compound may satisfy the following formula 3: <Expression 3> <al> =0.3702×< / al> +0.0832±0.5 ( <al> and< / al> (The numbers mean the number of moles of Al and Li, respectively.)

[0015] According to another embodiment of the present invention, a method for recovering lithium compounds for valuable metal recovery includes preparing a battery, freezing and forcibly discharging the battery, crushing the battery, and heating the crushed battery material, wherein the heating is performed at a temperature of 1,100 to 1,400°C and at a vacuum level (LogP [atm]) of -4 to 0. The lithium compound recovered through the heating includes impurities, which may include, by weight, Na: 1.8 wt% or less (excluding 0 wt%), K: 0.06 wt% or less (excluding 0 wt%), Ca: 0.62 wt% or less (excluding 0 wt%), and Mg: 0.47 wt% or less (excluding 0 wt%).

[0016] In one embodiment, the lithium compound recovered through the heating step may contain lithium in an amount of 13.0 wt% or more.

[0017] In one embodiment, the method for recovering lithium compounds for valuable metal recovery can satisfy the following formula 2: <Expression 2> ([Na] + [K] + [Mg]) / [Ca]≦3.6 ([Na], [K], [Mg], and [Ca] mean the weight percentages of Na, K, Mg, and Ca, respectively.)

[0018] In one embodiment, the heating of the crushed battery fragments may be performed in an atmosphere of at least one gas selected from the group consisting of an inert gas, carbon dioxide, carbon monoxide, and a hydrocarbon gas.

[0019] In one embodiment, the freezing and forced discharging of the battery may be performed by cooling the battery to -150 to -60°C.

[0020] In one embodiment, the freezing and forced discharging of the battery may be performed by cooling the battery to -60 to -20°C under a vacuum atmosphere of 1000 torr or less.

[0021] In one embodiment, the step of freezing and forcibly discharging the battery may satisfy the following equation 4: <Expression 4> 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)

[0022] In one embodiment, the step of freezing and forcibly discharging the battery may include forcibly discharging at a discharge rate of less than 0.04 V / min. [Effects of the Invention]

[0023] According to one embodiment of the present invention, the lithium compound for valuable metal recovery provides a lithium compound component with a low content of impurities such as Na, K, Mg, and Ca by controlling the temperature and pressure in the heat treatment step in the valuable metal recovery method. This reduces the problem of an additional process load for impurity removal to increase the Li recovery rate in the wet recovery process, thereby providing economic benefits to valuable metal recovery.

[0024] Another embodiment of the present invention provides a method for producing lithium compounds for valuable metal recovery, which provides a method for recovering valuable metals by producing lithium compounds having the above-mentioned advantages. [Brief explanation of the drawings]

[0025] [Figure 1] 10 is a graph of minimum cooling time according to one embodiment of the present invention. [Figure 2] 1 is a graph showing the relationship between battery weight, external cooling temperature, and cooling time according to an embodiment of the present invention. [Figure 3a] 10 is a photograph showing a fire that occurred when the product was crushed after being frozen for a shorter time than the minimum cooling time according to a comparative example of the present invention. [Figure 3b] 10 is a photograph showing a fire that occurred when the product was crushed after being frozen for a shorter time than the minimum cooling time according to a comparative example of the present invention. [Figure 3c] 10 is a photograph of an example in which no fire occurred when the product was frozen for a longer period than the minimum cooling time and then crushed according to an example of the present invention. [Figure 3d] 10 is a photograph of an example in which no fire occurred when the product was frozen for a longer period than the minimum cooling time and then crushed according to an example of the present invention. [Figure 4] 4 is a photograph showing an evaluation of the amount of expansion depending on the discharge rate of a battery cell according to an embodiment of the present invention; [Figure 5] 1 shows an XRD analysis of a lithium compound produced after high temperature heat treatment according to one embodiment of the present invention. [Figure 6a] 1 is a graph illustrating the correlation of temperature and pressure for removing impurities according to one embodiment of the present invention. [Figure 6b] 1 is a graph illustrating the correlation of temperature and pressure for removing impurities according to one embodiment of the present invention. [Figure 6c] 1 is a graph illustrating the correlation of temperature and pressure for removing impurities according to one embodiment of the present invention. [Figure 6d] 1 is a graph illustrating the correlation of temperature and pressure for removing impurities according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Terms such as "first," "second," and "third" are used to describe various portions, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one portion, component, region, layer, or section from another portion, component, region, layer, or section. Therefore, a first portion, component, region, layer, or section described below can be referred to as a second portion, component, region, layer, or section without departing from the scope of the present invention.

[0027] The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the phrase clearly dictates otherwise. As used in the specification, the term "comprising" refers to the inclusion of certain features, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0028] When a part is referred to as being "on" or "on" another part, this means that it is directly on or above the other part, or there may be other parts between them. In contrast, when a part is referred to as being "directly on" another part, there are no other parts between them.

[0029] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries are to be interpreted in addition to those having meanings consistent with the relevant technical literature and the presently disclosed content, and are not to be interpreted in an ideal or very formal sense unless otherwise defined.

[0030] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the preferred embodiments of the present invention is provided by way of example only and is not intended to limit the scope of the present invention, which is defined solely by the scope of the claims set forth below.

[0031] According to one embodiment of the present invention, the lithium compound for valuable metal recovery is a lithium compound for valuable metal recovery recovered from waste batteries, and contains Li, Al, and impurities, which may include Na, K, Ca, and Mg.

[0032] In one embodiment, the lithium compound for recovering valuable metals may satisfy the following formula 1: <Expression 1> <al> / < / al> ≦1.30 ( <al> and< / al> (The numbers mean the number of moles of Al and Li, respectively.)

[0033] The above formula 1 represents the molar ratio of aluminum to lithium. The formula 1 can be 1.30 or less, specifically 0.61 or less. By satisfying the formula 1, Li is recovered in the form of a stable aluminate such as LiAlO2 or Li5AlO4, which has the advantage of minimizing deviation in Li recovery rate. If the formula 1 does not satisfy the above range, Li is recovered in the form of alumina such as Al2O3 rather than in the form of aluminate, which increases the process cost for removing Al impurities.

[0034] In one embodiment, the lithium compound may satisfy the following formula 2: <Expression 2> ([Na] + [K] + [Mg]) / [Ca]≦3.6 ([Na], [K], [Mg], and [Ca] mean the weight percentages of Na, K, Mg, and Ca, respectively.)

[0035] The above equation 2 is a relational expression relating to the ratio of impurity content and can be used as a measure of impurity removal concentration. Specifically, in equation 2, Na and K are impurities that are relatively easy to remove, but Mg and Ca can only be removed when the temperature is high and the vacuum level is low. Therefore, equation 2 can be used as a measure of whether impurities, specifically Na and K, have been sufficiently removed.

[0036] The formula 2 can satisfy a value of 3.6 or less, specifically, a range of 2.0 to 3.6, and more specifically, a range of 2.2 to 3.2. If the formula 2 is out of the above range, there is a problem that impurities cannot be adequately removed.

[0037] In one embodiment, the lithium compound may satisfy the following formula 3: <Expression 3> <al> =0.3702×< / al> +0.0832±0.5 ( <al> and< / al> (The numbers mean the number of moles of Al and Li, respectively.)

[0038] It was confirmed through the above formula 3 that elements with strong oxidizing power at high temperatures, such as Li and Al, produce reaction products such as LiAlO2 or Li5AlO4 that are stable at high temperatures. Thus, during high-temperature heat treatment, the reaction between the Al cover or Al current collector of the LiB battery and Li in the cathode material occurs stably according to the above formula, and by satisfying the formula 3, it was confirmed that there is an advantage in that the Li recovery rate can be improved.

[0039] According to another embodiment of the present invention, a method for recovering lithium compounds for valuable metal recovery includes preparing a battery, freezing and forcibly discharging the battery, crushing the battery, and heating the crushed battery material. By heating the crushed battery material, various forms of lithium compounds can be generated or recovered from lithium oxide (LiO) contained in the cathode material.

[0040] The step of preparing the battery may involve crushing a material to be used as a base material for the crushed battery material, or preparing the crushed material itself. The base material for the crushed battery material may include end-of-life batteries, waste batteries, and waste generated during the manufacturing process of lithium-ion batteries. Specifically, the waste batteries may include cathode materials such as scrap, jelly rolls, and slurry that constitute the waste batteries, as well as defective products generated during the manufacturing process, residual materials within the manufacturing process, and waste generated during the manufacturing process. The crushed material itself may be the crushed product itself, such as black powder. By reusing waste batteries in this way, manufacturing crushed battery material is environmentally friendly and economically advantageous.

[0041] In one embodiment, the freezing and forced discharging of the battery may be performed by cooling the battery to a temperature range of −150 to −60° C. If the temperature is outside the upper limit of the temperature range, the voltage remaining inside the battery may not drop to 0 V, which may cause a battery reaction due to a short circuit, and the electrolyte may not be completely frozen.

[0042] In one embodiment, the freezing and forced discharging of the battery may be performed by cooling the battery to -60 to -20°C under a vacuum atmosphere of 1000 torr or less. The freezing and forced discharging of the battery is performed at a temperature sufficient to freeze the electrolyte contained in the battery. Specifically, the freezing and forced discharging of the battery may be performed at a temperature range of -150 to -20°C. More specifically, the temperature range may be -150 to -50°C, and even more specifically, the temperature range may be -80 to -60°C.

[0043] When the battery is frozen within this temperature range, the small amount of voltage remaining inside the battery, for example, about 2V to 3V, drops to nearly 0V. Therefore, even if a short circuit occurs due to direct contact between the positive and negative electrodes, no battery reaction occurs, the battery temperature does not increase, and gas generation and combustion of the electrolyte do not occur. Furthermore, because the electrolyte is in a frozen state or a state in which vaporization is suppressed, the mobility of lithium ions is very low, which significantly reduces the electrical conductivity due to the lithium ion migration, and because vaporization of the electrolyte does not occur, flammable gases such as ethylene, propylene, and hydrogen are not generated.

[0044] If the freezing process is performed outside the above temperature range, for example, if the temperature is higher than -60°C, the remaining voltage 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, which is not appropriate. Furthermore, if the battery is cooled to -150°C, the electrolyte will be sufficiently frozen and the internal voltage of the battery will also drop to 0V, so there is no need to lower the temperature. Thus, by including a step of freezing batteries such as lithium secondary batteries before crushing them, the battery disposal method advantageously prevents the risk of fire that may occur during the battery crushing process.

[0045] In one embodiment, the freezing and forced discharging of the battery may be performed 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 freezing process of the battery is performed by cooling at a temperature range of −60 to −20° C., the supply of oxygen is suppressed to prevent the electrolyte from reacting with oxygen, which may result in an explosion, and the vaporization of the electrolyte may be suppressed to prevent the generation of flammable gases such as ethylene, propylene, or hydrogen.

[0046] In one embodiment, the step of freezing and forcibly discharging the battery may satisfy the following equation 4: <Expression 4> 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)

[0047] In Equation 4, W represents the weight of the battery, e.g., the weight of a battery pack, a single battery, or a combination thereof. The minimum cooling time is the external cooling temperature applied to the battery, e.g., the target temperature for cooling the electrolyte in the battery.

[0048] The steps of freezing and forcibly discharging the battery are advantageous in that the electrolyte inside the battery is cooled by performing the steps for the minimum cooling time or longer, thereby enabling subsequent processes to be performed stably. However, if the steps of freezing and forcibly discharging the battery are performed for a time shorter than the minimum cooling time, the electrolyte may not be cooled, which may result in a risk of fire when the battery is crushed.

[0049] In one embodiment, the step of freezing and forcibly discharging the battery may be performed at a discharge rate of less than 0.04 V / min. Specifically, the forced discharge may be performed at a discharge rate of 0.03 V / min. If the discharge rate is outside this range, the battery may expand to an increased extent, resulting in reduced stability.

[0050] The step of crushing the battery may refer to a step of applying impact or pressure to the battery so that a portion of the battery falls off the battery. In one embodiment, the step of crushing the battery may refer to a step of crushing the battery, a step of cutting the battery, a step of compressing the battery, and combinations thereof. Specifically, the step of crushing may include all steps of breaking the battery into small pieces.

[0051] In one embodiment, the step of crushing the battery may include all of the steps of compressing the frozen and discharged battery or applying an external force such as a shear force or a tensile force to crush the battery. The step of crushing the battery may be performed using, for example, a crusher.

[0052] In one embodiment, the step of crushing the battery may be performed at least once, and more specifically, the step of crushing the battery may be performed at least once continuously or discontinuously.

[0053] In one embodiment, the battery crushing step may be performed so that the maximum size of the battery fragments is 100 mm or less. Specifically, the size of the battery fragments may be 50 mm or less. If the maximum size of the battery fragments is 100 mm or more, the temperature of heat generated due to instability caused by crushing the battery fragments may rise to a temperature range of 120°C, which is the average vaporization temperature of the electrolyte, and stability issues such as fire may occur.

[0054] The step of heating the crushed battery fragments may involve heating the crushed battery fragments to a temperature above the melting point by placing the crushed battery fragments in a heating furnace capable of raising the temperature to a high temperature. Specifically, the step of heating the crushed battery fragments may involve heat treatment conditions for performing a high-temperature reduction reaction without a melting step.

[0055] In one embodiment, the heating of the shredded battery material may be performed at a temperature ranging from 1,100 to 1,400°C. Specifically, the heating may be performed at a temperature ranging from 1,200 to 1,400°C.

[0056] Within this temperature range, the carbon in the crushed battery material can be burned to a minimum, allowing the reduction reaction to occur with almost no carbon dioxide generation. If the temperature range is outside the upper limit of this range, there is a problem of lithium being lost due to evaporation. If the temperature range is outside the lower limit of this range, there is a problem of alloying elements not being sintered and reduced.

[0057] In one embodiment, the step of heating the shredded battery fragments may be performed at a vacuum level (LogP [atm]) ranging from -4.0 to 0. Specifically, the vacuum level may be in the range of -4.0 to -1.0, more specifically, -3.6 to -1.0. The vacuum level refers to the logarithmic value of the pressure (P) inside the heating furnace.

[0058] When the crushed battery material is heated within the above-mentioned range of the degree of vacuum, there is an advantage in that the concentrations of impurities such as Na, K, Ca, and Mg are reduced. When the degree of vacuum is outside the upper limit of the above-mentioned range, there is a problem that Na, K, Ca, and Mg are not vaporized, and therefore the impurities are not removed. When the degree of vacuum is outside the lower limit of the above-mentioned range, there is a problem that the Li recovery rate is reduced due to the vaporization of Li.

[0059] In one embodiment, the heating of the crushed battery fragments can be performed in an atmosphere of at least one gas selected from the group consisting of an inert gas, carbon dioxide, carbon monoxide, and a hydrocarbon gas. The inert gas may include, for example, at least one of argon and nitrogen. By heating the crushed battery fragments in the gas atmosphere, lithium can be effectively recovered by generating lithium-containing compounds contained in the crushed battery fragments.

[0060] In one embodiment, the lithium compound recovered through the heating step may include at least one of lithium aluminate (LiAlO2), lithium carbonate (LiCO3), lithium fluoride (LiF), and lithium chloride (LiCl). Specifically, the lithium aluminate, lithium carbonate, and lithium fluoride may be prepared through the following Reaction Schemes 1 to 3.

[0061] [Reaction Scheme 1] Li2O(s) + AlO3(s) = 2LiAlO2(s) [Reaction Scheme 2] Li2O(s) + C(s) + O2(g) = Li2CO3(s) [Reaction Scheme 3] Li2O+2F=2LiF+1 / 2O2(g)

[0062] As shown in Reactions 1-3 above, Li2O in the positive electrode material can produce LiAlO2 by reacting with the Al current collector or Al cover material, Li2CO3 can be produced by combining with the carbon negative electrode material and oxygen from the positive electrode material or oxygen in the air, and Li2O can react with fluorine contained in the electrolyte to produce LiF. The active production of these lithium compounds reduces the content of impurities such as Na, K, Ca, and Mg. Specifically, these impurities may be dissolved in small amounts within the crystalline lithium compound.

[0063] In one embodiment, the lithium compound contains impurities, which may include, by weight, Na: 1.8 wt% or less (excluding 0 wt%), K: 0.06 wt% or less (excluding 0 wt%), Ca: 0.62 wt% or less (excluding 0 wt%), and Mg: 0.47 wt% or less (excluding 0 wt%).

[0064] The reasons for limiting the content of the impurities will be explained below.

[0065] Na: 1.8% by weight or less (0% excluded) Sodium (Na) is a homologous element in the downstream process of recovering valuable metals from the crushed battery material. It reacts partially with lithium to form sodium hydroxide instead of lithium in the lithium hydroxide formation process, which can reduce lithium recovery or increase costs in the causticization process. The lithium compound may contain sodium at 1.8 wt% or less. Specifically, the sodium may be contained at 1.0 wt%, more specifically, 0.3 wt% or less.

[0066] If the sodium content is greater than the above range, there is a problem that the recovery rate decreases in the process required to produce lithium carbonate when Na is the same Group 1 element as Li during the crystallization process of Li dissolved in the solvent after the leaching process and solvent extraction process.

[0067] Ca: 0.62% by weight or less (0% excluded) Calcium (Ca), like sodium, is an element that reduces the recovery rate of valuable metals in the downstream process of recovering valuable metals from the crushed battery material. The lithium compound may contain 0.62 wt % or less of calcium, specifically 0.61 wt % or less, and more specifically 0.3 wt % or less of calcium.

[0068] If the calcium content is greater than the above range, the yield and process time may increase during the solid-liquid separation process, which is a process for purifying impurities after the leaching process. In addition, if the calcium content is too high, when the precursors nickel, cobalt, manganese hydroxide, and lithium hydroxide are synthesized to produce the cathode material, Li[NiCoMn] 1-x Ca x )]O2, and the potassium forms the oxide structure of the cathode material, hindering the movement of lithium ions and reducing the capacity of the battery.

[0069] Mg: 0.47% by weight or less Magnesium (Mg) is an element that prevents separation of solid and liquid phases during acid leaching in the valuable metal recovery process. The lithium compound may contain 0.47 wt% or less of magnesium, specifically 0.46 wt% or less, and more specifically 0.3 wt% or less.

[0070] If the magnesium content is greater than the above range, it may cause a problem of burdening the recovery process of nickel, cobalt, lithium, etc. Also, if the magnesium content is too high, when the magnesium is synthesized with the precursors nickel, cobalt, manganese hydroxide, and lithium hydroxide to produce a cathode material, Li[NiCoMn] 1-x Mg x )]O2, which forms an oxide structure in the cathode, hindering the movement of lithium ions and reducing battery capacity.

[0071] K: 0.06% by weight or less Potassium (K) is also a lithium homologue that inhibits lithium from forming hydroxides. The lithium compound may contain 0.06 wt % or less of potassium, specifically 0.05 wt % or less, more specifically 0.01 wt % or less.

[0072] If the potassium content is greater than the above range, it may cause a load in the causticizing step, resulting in a decrease in the recovery rate of lithium.

[0073] Preferred examples and comparative examples of the present invention will be described below. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited to the following examples. [Example]

[0074] <Experimental Example> <Battery internal temperature based on minimum freezing time> The battery pack used in the example was crushed without freezing using the same crusher as in the example. During the crushing process, a flame occurred due to a short circuit, as shown in Figures 3a and 3b.

[0075] As described above, through the examples and comparative examples, it can be confirmed that by including a step of freezing the battery pack including the battery before crushing the battery, no short circuit occurs, no flame occurs, and excellent stability is achieved during the battery crushing step.

[0076] FIG. 1 shows the change in voltage of a battery with cooling temperature according to one embodiment of the present invention.

[0077] Referring to Figure 1, when the battery voltage was measured while the battery was frozen at -80°C, the battery pack showed almost the same voltage at high temperatures of about 40°C, room temperature, and temperatures up to -60°C, confirming that the battery characteristics were not lost. Next, when the temperature dropped from -60°C to -70°C, the voltage dropped sharply, and at -70°C the voltage became 0. As such, it was confirmed that no short circuit occurred when the battery was frozen at temperatures between -60 and -150°C.

[0078] FIG. 2 is a graph showing the relationship between battery weight, external cooling temperature, and cooling time according to one embodiment of the present invention.

[0079] Referring to FIG. 2, it can be seen that a battery treatment method according to an embodiment of the present invention can derive a minimum cooling time for cooling a battery during the freezing step. Specifically, it can be seen that the minimum cooling time is related to the battery weight, external cooling temperature, and 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 cooling the battery, it can be seen that the battery electrolyte begins to cool after a predetermined time and the voltage becomes zero. This indicates that a minimum maintenance time is required to sufficiently cool the battery interior, specifically the electrolyte.

[0080] Specifically, when the specific heat of the battery itself is taken into account in the heat transfer situation for cooling in which heat is taken to the outside, it is possible to confirm the battery weight and the time required for cooling. Thus, in order to cool the battery, the present invention can confirm the minimum time required for cooling using the external cooling temperature for refrigeration, the target temperature, and the battery weight.

[0081] Table 1 below lists the minimum cooling time depending on the battery weight and external cooling temperature.

[0082] [Table 1]

[0083] From Table 1 above, it can be seen that the smaller the battery weight, the shorter the minimum cooling time required for the battery that is subject to cooling. It can also be seen that when the battery is cooled for the minimum cooling time derived from the relationship between the battery weight, external cooling temperature, and target temperature, the battery, specifically the battery electrolyte, is cooled. Furthermore, when the battery is cooled for a time longer than the minimum cooling time, no fire occurs during the subsequent battery crushing process. Figures 3a and 3b are photographs of a comparative example of the present invention in which a fire occurred when frozen for a shorter time than the minimum cooling time and then crushed, while Figures 3c and 3d are photographs of an example of the present invention in which no fire occurred when frozen for a longer time than the minimum cooling time and then crushed.

[0084] 3a and 3b, an experiment was conducted to determine the fire risk of crushed materials when a battery was cooled for a time shorter than the minimum required cooling time. In this experiment, the battery weight was 25 kg, the external cooling temperature was -95°C, and the target freezing temperature was -70°C. When the value of Equation 4 below is 7 hours, the experiment was conducted for 5 hours, which is shorter than the value of Equation 4.

[0085] <Expression 4> Minimum cooling time=A×(W 0.33 ) (A=4×e (-0.02×dT) ,W=battery weight (kg), dT=|external cooling temperature - target temperature|, || means absolute value)

[0086] Figures 3c and 3d show an experiment on the fire outbreak status of crushed batteries when the batteries were frozen for more than the minimum freezing time required for cooling. The experiment was conducted with the same battery weight, external cooling temperature, and minimum freezing time as Figures 3a and 3b, but for more than 7 hours.

[0087] Table 2 below compares the fire occurrence status of the Example and Comparative Example with the same battery weight, external cooling temperature, and minimum freezing time (3a to 3d). The fire occurrence status was judged as "O" if a fire was observed after the battery was crushed, and "X" if not.

[0088] [Table 2]

[0089] Looking at Table 2 above, it can be seen that if the battery is cooled at a value less than the value of Equation 4, which corresponds to the minimum cooling time, the electrolyte will not be cooled down and a fire will break out after the battery is crushed.As such, if the battery is cooled using the value of Equation 4 as the minimum cooling time, it can be seen that the crushed battery can be safely reused without a fire breaking out after being crushed.

[0090] <Forced discharge> When electrical discharge is performed for forced discharge, the discharge is performed close to 0V, and the discharge rate (V / min) is set so that the pack unit is 5V or less per minute. Generally, a battery pack unit has a voltage of about 500V, but this varies depending on the state of charge, number of uses, and vehicle conditions. Therefore, testing is performed on a battery cell basis, which is the smallest unit within the battery, and the battery cell has a maximum voltage of 4.2V.

[0091] Table 3 below shows the behavior of the battery expansion amount per cell depending on the discharge rate and temperature.

[0092] [Table 3]

[0093] Figure 4 is a photograph showing the evaluation of the amount of expansion depending on the discharge rate of a battery cell according to an embodiment of the present invention. Looking at Table 3 and Figure 4, it was found that if the cell is forced to discharge at a rate of 0.04 V / min or more, the chemical structure inside the battery is rapidly broken down, making the battery very unstable and causing an increase in the amount of expansion due to phenomena such as evaporation of the cathode material and electrolyte inside the battery.

[0094] <Comparison of impurity components in crushed battery material depending on discharge method> Table 4 below compares the impurities such as Na, K, Mg, and Ca in the crushed batteries produced by discharging in salt water and then crushing the batteries, and in the crushed batteries produced by forced discharge and freeze-shredding.

[0095] [Table 4]

[0096] Looking at Table 4 above, it can be seen that when freeze-shredding and forced electrical discharge are performed, the content of impurities such as Na, K, Mg, and Ca is lower than when saltwater discharge is performed.

[0097] <Comparison of lithium compound components and content generated after high-temperature heat treatment> Table 5 below shows the components and contents of the products and lithium compounds produced when the crushed materials of the examples containing the impurities shown in Table 4 are heat-treated at a high temperature of 1300°C.

[0098] [Table 5]

[0099] As seen in Table 5 above, the impurities Na, K, Mg, and Ca in the frozen crushed material were found to be concentrated by approximately 800%. This is because the weight of the lithium compound produced after high-temperature heat treatment per 100 g of crushed material is reduced to a 6% level. Furthermore, in the case of lithium compounds produced by external force, the impurity contents of Na, K, Mg, and Ca can be controlled to within 0.3%, 0.1%, 0.3%, and 0.5%, respectively. Figure 5 shows the results of XRD analysis of the lithium compound produced after high-temperature heat treatment according to one embodiment of the present invention.

[0100] 5, it was confirmed that no crystalline phase containing impurities such as Na, K, Ca, or Mg was observed. Specifically, it was confirmed that most of the impurities were dissolved in small amounts in the crystalline phases of LiAlO2, Li2CO3, or LiF.

[0101] Specifically, LiAlO2 compositions may have XRD peaks at least one of 20.5-21.5°, 29.0-29.5°, 31.5-32.0°, 32.2-33.0°, 60.5-61.5°, and 70.0-72.0°. Li5AlO4 compositions may have XRD peaks at least one of 19.5-20.2° and 21.6-22.2°. LiF compositions may have XRD peaks at least one of 37.5-40.2°, 43.9-46.5°, and 64.5-66.5°. Li2CO3 compositions may have XRD peaks at least one of 24.0-26.0°, 27.0-29.0°, 34.0-36.0°, and 37.0-39.0°.

[0102] Table 6 below compares the alloy and lithium compound components that were separated after high-temperature heat treatment and by external force.

[0103] [Table 6]

[0104] Looking at Table 6 above, it can be seen that the impurity content in lithium compounds that have undergone high-temperature heat treatment after saltwater discharge is approximately 2 to 11 times higher than that of freeze-shattering. When saltwater discharge is followed by high-temperature heat treatment, the high impurity content necessitates the addition of an impurity removal process for lithium recovery during the wet process, which increases the process load. Therefore, by performing high-temperature heat treatment after cryogenic freeze-shattering and forced discharge, the impurity contents of Na, K, Mg, and Ca can be controlled to within 0.3%, 0.1%, 0.3%, and 0.5%, respectively.

[0105] <Impurity control through temperature and vacuum during high-temperature heat treatment> 6a-6d are graphs illustrating the correlation of temperature and pressure for removing impurities according to one embodiment of the present invention.

[0106] 6a to 6d are graphs showing the correlation between temperature and pressure for removing the impurities Na, K, Ca, and Mg. Specifically, impurities such as volatile substances Ca, Mg, Na, and K can be removed while suppressing the volatilization reaction of Li by adjusting the temperature and vacuum. The temperature can be adjusted in the range of 300 to 1400°C, and the vacuum can be adjusted in the range of logP (atm) -4 to 0.

[0107] When crushed LiB batteries or black mass containing high levels of the above impurities are charged into a high-temperature heat treatment reactor, Na, K, Ca, and Mg can be removed through the following reaction formula.

[0108] Specifically, the conditions for volatilizing Na, K, Ca, and Mg are as shown in the following reaction formulas 1 to 4. [Reaction Scheme 1] Na volatilization condition: Reaction temperature = 94.58 × log P (atm) + 801.28 [Reaction Scheme 2] K volatilization condition: Reaction temperature = 68.425 × log P (atm) + 623.35 [Reaction Scheme 3] Ca volatilization conditions: Reaction temperature = 119.26 × log P (atm) + 1557.9 [Reaction Scheme 4] Mg volatilization conditions: Reaction temperature = 140.25 × log P (atm) + 1805.1

[0109] Table 7 below shows the changes in the Na, K, Ca, and Mg components after high-temperature heat treatment depending on the temperature and degree of vacuum.

[0110] [Table 7]

[0111] Looking at item 7 above, we confirmed that when the temperature is low at 1,000°C, even if the vacuum level is reduced, there is a problem of Ca, Mg, Na, and K not being sufficiently removed. Also, when the temperature is between 1,100 and 1,400°C, and the vacuum level is too low at -5, we confirmed that Li disappearance occurs. Furthermore, at 1,500°C, which is higher than 1,400°C, Li disappearance occurs at a vacuum level of -3, demonstrating the inferiority of the process at high temperatures.

[0112] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention. < / al>

Claims

1. A lithium compound for recovering valuable metals recovered from waste batteries, Contains Li, Al, and impurities, The impurities include, in weight percent, Na: 1.8 wt % or less (0 wt % excluded), K: 0.06 wt % or less (0 wt % excluded), Ca: 0.62 wt % or less (0 wt % excluded), and Mg: 0.47 wt % or less (0 wt % excluded), A lithium compound satisfying the following formula 1: <Formula 1> <Al> / ≦1.30 (<Al> and mean the number of moles of Al and Li, respectively.)

2. The lithium compound according to claim 1, which satisfies the following formula 2: <Formula 2> ([Na]+[K]+[Mg]) / [Ca]≦3.6 ([Na], [K], [Mg], and [Ca] mean the weight percentages of Na, K, Mg, and Ca, respectively.)

3. The lithium compound according to claim 1, which satisfies the following formula 3: <Formula 3> <Al>=0.3702×+0.0832±0.5 (<Al> and mean the number of moles of Al and Li, respectively.)

4. Preparing the battery; freezing and force-discharging the battery; crushing the battery; and Heating the shredded battery fragments, The heating step is performed at a temperature in the range of 1,100 to 1,400°C, The heating step is performed under a vacuum level (Log P [atm]) of -4 to 0, The lithium compound recovered through the heating step contains impurities, and the impurities include, in weight percent, Na: 1.8 wt % or less (excluding 0 wt %), K: 0.06 wt % or less (excluding 0 wt %), Ca: 0.62 wt % or less (excluding 0 wt %), and Mg: 0.47 wt % or less (excluding 0 wt %).

5. 5. The method for recovering a lithium compound for valuable metal recovery according to claim 4, wherein the lithium compound recovered through the heating step contains lithium in an amount of 13.0 wt% or more.

6. 5. The method for recovering a lithium compound for valuable metal recovery according to claim 4, which satisfies the following formula 2: <Formula 2> ([Na]+[K]+[Mg]) / [Ca]≦3.6 ([Na], [K], [Mg], and [Ca] mean the weight percentages of Na, K, Mg, and Ca, respectively.)

7. 5. The method for recovering lithium compounds for valuable metal recovery according to claim 4, wherein the step of heating the crushed battery material is performed in an atmosphere of at least one gas selected from the group consisting of an inert gas, carbon dioxide, carbon monoxide, and a hydrocarbon gas.

8. 5. The method for recovering lithium compounds for valuable metal recovery according to claim 4, wherein the step of freezing and forcibly discharging the battery is performed by cooling the battery to a temperature of -150 to -60°C.

9. 5. The method of claim 4, wherein the step of freezing and forcibly discharging the battery is performed by cooling the battery to −60 to −20° C. under a vacuum atmosphere of 1000 torr or less.

10. 5. The method for recovering lithium compounds for valuable metal recovery according to claim 4, wherein the step of freezing and forcibly discharging the battery satisfies the following formula 4: <Formula 4> 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)

11. 5. The method for recovering lithium compounds for valuable metal recovery according to claim 4, wherein the step of freezing and forcibly discharging the battery comprises forcibly discharging at a discharge rate of less than 0.04 V / min.

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