Lithium-containing slag and method for producing valuable metals

Abstract

To provide Li-containing slag which is obtained by melting starting materials such as waste lithium ion batteries containing Li and Al, and which enables effective control of a slag melting point to be under a specific temperature while suppressing the amount of flux addition, abd also enables effective concentration of Li while suppressing the amount of slag.SOLUTION: The present invention provides Li-containing slag which is obtained by melting starting materials that include waste lithium ion batteries containing lithium (Li) and aluminum (Al). The Li-containing slag satisfies the relational expressions Al / Li<5 and silicon (Si) / Li<0.7 in terms of the mass ratio and contains 20 mass% or less of Al, 3 mass% to 20 mass% of Li, and 0 mass% to 7 mass% of Si.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lithium-containing slag and a method for producing valuable metals.

Background Art

[0002] In recent years, lithium-ion batteries have become widespread as lightweight and high-output batteries. A well-known lithium-ion battery has a structure in which a negative electrode material, a positive electrode material, a separator, and an electrolyte are enclosed in an exterior can.

[0003] For example, in a lithium-ion battery, the exterior can is made of a metal such as iron (Fe) or aluminum (Al). The negative electrode material is composed of a negative electrode active material (such as graphite) fixed to a negative electrode current collector (such as a copper foil). The positive electrode material is composed of a positive electrode active material (such as lithium nickelate or lithium cobaltate) fixed to a positive electrode current collector (such as an aluminum foil). The separator is made of a porous resin film of polypropylene or the like. The electrolyte contains an electrolyte such as lithium hexafluorophosphate (LiPF6).

[0004] One of the main applications of lithium-ion batteries is in hybrid vehicles and electric vehicles. Therefore, in accordance with the life cycle of automobiles, it is expected that a large number of mounted lithium-ion batteries will be discarded in the future. There are also lithium-ion batteries discarded as defective products during manufacturing. It is required to recycle such used batteries and defective batteries generated during manufacturing (hereinafter referred to as "waste lithium-ion batteries") as resources.

[0005] As a recycling method, a dry smelting process has been proposed in which a spent lithium-ion battery is completely melted in a high-temperature furnace. The dry smelting process separates and recovers valuable metals typified by cobalt (Co), nickel (Ni), and copper (Cu) and metals with low added value typified by iron (Fe) and aluminum (Al) by utilizing the difference in oxygen affinity between them through melting the crushed spent lithium-ion battery. In this method, metals with low added value are oxidized as much as possible to form slag, while valuable metals are recovered as alloys by suppressing their oxidation as much as possible.

[0006] For example, Patent Document 1 discloses a technology regarding Li2O-supported metallurgical slag characterized by a weight composition containing Al2O3, SiO2, CaO, and MnO, where 3% < Li2O < 20%, 1% < MnO < 7%, 38% < Al2O3 < 65%, CaO < 55%, and SiO2 < 45%. However, the Li2O-supported metallurgical slag disclosed in Patent Document 1 contains Al2O3 at a content exceeding 38%, which not only raises the slag melting point but also increases the slag amount. Therefore, in the process of manufacturing valuable metals from raw materials such as spent lithium-ion batteries, when such Li2O-supported metallurgical slag is generated, it becomes necessary to increase the amount of flux added to lower the slag melting point. Also, as the amount of flux added increases, the amount of slag generated (slag amount) increases, resulting in a reduction in the Li content rate in the slag and an inability to obtain slag with sufficiently concentrated Li.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] This invention was proposed in view of the above circumstances, and aims to provide a method for producing valuable metals, including a method for producing Li-containing slag obtained by melting raw materials such as waste lithium-ion batteries containing Li and Al, which can effectively control the slag melting point to a predetermined temperature or lower while suppressing the amount of flux added, and a slag in which Li is effectively concentrated while suppressing the amount of slag. [Means for solving the problem]

[0009] To solve the above-mentioned problems, the present inventors provide the following:

[0010] (1) The first aspect of the present invention is a Li-containing slag obtained by melting raw materials including waste lithium-ion batteries containing lithium (Li) and aluminum (Al), wherein the mass ratios are Al / Li < 5 and silicon (Si) / Li < 0.7, and the slag contains Al in a proportion of 20% by mass or less, Li in a proportion of 3% by mass or more and 20% by mass or less, and Si in a proportion of 0% by mass or more and 7% by mass or less.

[0011] (2) The second invention of the present invention is a Li-containing slag having a mass ratio of Si / Li < 0.35 in the first invention.

[0012] (3) The third invention of the present invention is a method for producing valuable metals from raw materials including waste lithium-ion batteries containing lithium (Li) and aluminum (Al), comprising: a pretreatment step including a process to remove an outer casing made of Al from the raw materials; and a melting step of melting the raw materials obtained through the pretreatment step to obtain Li-containing slag and a metal containing valuable metals, wherein the Li-containing slag obtained in the melting step has the relationship Al / Li < 5 and silicon (Si) / Li < 0.7 by mass ratio, and contains Al in the proportion of 20% by mass or less, Li in the proportion of 3% by mass or more and 20% by mass or less, and Si in the proportion of 0% by mass or more and 7% by mass or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to effectively control the slag melting point to a predetermined temperature or lower while suppressing the amount of flux added, and to provide a slag in which Li is effectively concentrated while suppressing the amount of slag, as well as a method for producing valuable metals including the production of such slag. [Modes for carrying out the invention]

[0014] The following describes specific embodiments of the present invention (hereinafter referred to as "these embodiments"). It should be noted that the present invention is not limited to the following embodiments, and various modifications are possible without altering the essence of the invention.

[0015] ≪1. Lithium-containing slag≫ The lithium (Li)-containing slag according to this embodiment (hereinafter also simply referred to as "slag") is obtained by melting raw materials containing waste lithium-ion batteries that contain Li and aluminum (Al). The term "raw materials containing waste lithium-ion batteries" includes not only used lithium-ion batteries (waste batteries) but also their components.

[0016] Li-containing slag is used as a raw material for separating, extracting, and recovering lithium. Therefore, it is preferable that the lithium-containing slag is effectively concentrated and has a high lithium content.

[0017] Specifically, the Li-containing slag according to this embodiment has a composition in which Al / Li < 5 and silicon (Si) / Li < 0.7 by mass ratio, and is characterized by containing Al in the proportion of 20% by mass or less, Li in the proportion of 3% by mass or more and 20% by mass or less, and Si in the proportion of 0% by mass or more and 7% by mass or less.

[0018] Li-containing slag contains Al. The Al in the Li-containing slag originates from the outer casing of the waste lithium-ion battery used as raw material, and from the current collector that holds the positive electrode active material. In Li-containing slag, the Al content is 20% by mass or less. Preferably, the Al content is 19% by mass or less, and more preferably 18% by mass or less.

[0019] Thus, by keeping the Al content below 20% by mass, the slag melting point is suppressed, and the amount of flux added in a predetermined ratio to Al during the melting process can be reduced. As a result of reducing the amount of flux added, the amount of slag (slag production) can be reduced, and the concentration of Li contained in the slag can be increased. In other words, Li can be effectively concentrated in the slag.

[0020] In lithium-containing slag, the lithium content is 3% by mass or more. Preferably, the lithium content is 4% by mass or more, and more preferably 6% by mass or more. In slag with a lithium content of 3% by mass or more, the lithium is effectively concentrated, which can lower the melting point of the slag and reduce the cost of recovering lithium from the slag. There is no particular upper limit to the lithium content, but keeping it at 20% by mass or less can prevent damage to the refractory material of the furnace wall used in the melting process.

[0021] Furthermore, in Li-containing slag, the Al / Li mass ratio is less than 5 (Al / Li < 5). Preferably, Al / Li < 4, and more preferably, Al / Li < 3. By satisfying the relationship Al / Li < 5 in this way, the amount of Al2O3 generated in the slag can be reduced, as can the amount of flux added during the melting process, and as a result, the Li concentration in the slag can be effectively increased.

[0022] In the Li-containing slag, Si is contained in a proportion of 0 mass% or more and 7 mass% or less. Further, the Si content ratio is preferably 5 mass% or less, more preferably 3 mass% or less. By the Si content ratio being 7 mass% or less, the Li content ratio in the slag can be increased.

[0023] Also, in the Li-containing slag, the value of Si / Li, which is the mass ratio of Si to Li, is less than 0.7 (Si / Li < 0.7). Thus, by performing the melting treatment so as to obtain a slag satisfying the relationship of Si / Li < 0.7, the Li content ratio in the slag can be effectively increased. That is, in the melting treatment, for example, although the increase in the slag melting point due to Al2O3 generated in the slag is suppressed by the addition of a flux, by avoiding the use of silicon dioxide (SiO2) and the mixing of Si, which have a relatively small effect of lowering the slag melting point, the Li content ratio in the slag can be efficiently increased.

[0024] Incidentally, as the flux, as will be described later, it is preferable to use calcium oxide (CaO) or the like, which has a large effect of lowering the slag melting point.

[0025] Furthermore, in the Li-containing slag, it is more preferable that Si / Li is less than 0.35 in terms of mass ratio. By satisfying the relationship of Si / Li < 0.35, the Li extraction rate (leaching rate) when separating and extracting Li from the slag can be improved. For example, when extracting (leaching) Li contained in the Li-containing slag into a liquid using a mineral acid or the like, if SiO is present around Li, the Li extraction rate will decrease rapidly. Therefore, in the Li-containing slag, preferably, by Si / Li being less than 0.35, Li can be effectively and efficiently separated and extracted.

[0026] ≪2. Method for producing valuable metals≫ The method for producing valuable metals according to this embodiment is a method for separating and recovering valuable metals (e.g., Cu, Ni, Co) from raw materials including waste lithium-ion batteries containing lithium (Li) and aluminum (Al). Therefore, this method can also be described as a method for recovering valuable metals. The method according to this embodiment is mainly a dry smelting process, but it may consist of a dry smelting process and a wet smelting process.

[0027] Specifically, the method according to this embodiment includes a pretreatment step that includes removing an outer casing made of Al from raw materials containing waste lithium-ion batteries, and a melting step that melts the raw materials obtained through the pretreatment step to obtain Li-containing slag and metal containing valuable metals.

[0028] Furthermore, this method is characterized in that the Li-containing slag obtained in the melting process has the following relationships in mass ratio: Al / Li < 5 and silicon (Si) / Li < 0.7, and contains Al in proportions of 20% by mass or less, Li in proportions of 3% by mass or more and 20% by mass or less, and Si in proportions of 0% by mass or more and 7% by mass or less.

[0029] As mentioned above, the raw materials include waste lithium-ion batteries. The term "waste lithium-ion batteries" encompasses not only the used batteries themselves but also their components. The valuable metals included in the raw materials are those targeted by the manufacturing method and are not particularly limited, but include, for example, at least one metal or alloy selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), and combinations thereof.

[0030] [Pre-treatment process for waste batteries] The waste battery pretreatment process S1 is a process of preparing the materials to be melted (raw materials to be melted, furnace charge) for the melting process in which raw materials including waste lithium-ion batteries are melted to obtain a reduced product of Li-containing slag and metal composed of valuable metals. In particular, the waste battery pretreatment process S1 includes a process to remove the outer casing made of Al.

[0031] Waste lithium-ion batteries are generally constructed as a sealed system, with an aluminum (A) outer casing containing the electrolyte and positive / negative electrode active materials. Therefore, processing them as they are is dangerous, as it could lead to explosions due to the electrolyte inside the casing. Furthermore, as mentioned above, since the casing is mainly made of aluminum, if it is melted in its current state, the aluminum will be distributed into the slag, increasing the aluminum content.

[0032] Therefore, in the waste battery pretreatment process S1, the outer casing, which is made of at least Al, is removed. By removing the outer casing, the electrolyte inside the casing can also be removed, resulting in a safer treatment process, and the recovery productivity of valuable metals such as Cu, Ni, and Co can be increased. In addition, since the contamination of Al originating from the outer casing can be avoided, the Al content in the slag can be reduced. In other words, by removing the outer casing in the waste battery pretreatment process S1, the Al content of the slag (Li-containing slag) obtained by the melting process can be adjusted.

[0033] In this way, by separating the Al contained in the outer container, the proportion of Al charged into the melting process S3 can be significantly reduced. This significantly reduces the amount of flack used, which is added in proportion to the Al content. As a result, the amount of slag obtained through the melting process S3 can be greatly reduced, and the concentration of Li contained in the slag can be increased.

[0034] There are no particular limitations on the specific method for removing the outer casing. After discharging the waste lithium-ion battery, including the outer casing, the electrolyte is removed by roasting at a temperature of 200°C to 300°C to obtain the battery contents (roasted material). Then, the obtained battery contents are subjected to a crushing process and sieved to separate the sieved material containing Al from the furnace charge material to be melted. Al can be easily separated into crushed material even with light crushing.

[0035] Furthermore, one of the purposes of the crushing process is to improve the reaction efficiency in the subsequent dry smelting process, and by improving the reaction efficiency, the recovery rate of valuable metals such as Cu, Ni, and Co can be increased. The crushing method is not particularly limited, and the contents of the battery (roasted material) can be crushed using conventionally known crushing machines such as cutter mixers.

[0036] [Preheating process] The pulverized waste lithium-ion battery material that has undergone the waste battery pretreatment step S1 can be subjected to a preheating step S2 as needed, where it is heated to a predetermined temperature and subjected to oxidative roasting. By performing oxidative roasting in the preheating step S2 in this way, impurities contained in the battery contents can be removed by volatilization or thermal decomposition.

[0037] In the preheating step S2, it is preferable to heat at a temperature of 700°C or higher (preheating temperature) to perform oxidative roasting. Setting the preheating temperature to 700°C or higher can improve the efficiency of removing impurities contained in the battery. On the other hand, it is preferable to set the upper limit of the preheating temperature to 900°C or lower, which can suppress thermal energy costs and improve processing efficiency.

[0038] The oxidative roasting process is preferably carried out in the presence of an oxidizing agent. This allows for the efficient oxidation and removal of carbon (C) among the impurities contained in the battery contents. It also allows for the oxidation of Al. In particular, by oxidizing and removing C, the molten fine particles of valuable metals that are generated locally in the subsequent melting process S3 can aggregate without physical obstruction by C, making it easier to integrate and recover the alloy obtained as a molten product. Generally, the main elements constituting waste lithium-ion batteries are oxidized in the following order based on their affinity for oxygen: Al > Li > C > Mn (manganese) > P (phosphorus) > Fe (iron) > Co > Ni > Cu.

[0039] While there are no particular limitations on the oxidizing agent, it is preferable to use an oxygen-containing gas such as air, pure oxygen, or oxygen-enriched gas, due to its ease of handling. Furthermore, the amount of oxidizing agent introduced can be approximately 1.2 times the chemical equivalent required for the oxidation of each substance to be oxidized.

[0040] [Melting process] In the melting process (reduction melting process) S3, the pulverized waste lithium-ion battery material (molten material, furnace charge material) is melted (reduction melting) together with flux to obtain a reduced product consisting of molten metal containing valuable metals and slag containing Li (Li-containing slag). As a result, impurity elements such as Al are incorporated into the slag as oxides, and P is also incorporated into the flux and included in the slag. On the other hand, valuable metals such as Cu, which do not easily form oxides, are melted and can be recovered from the molten product as an integrated alloy.

[0041] In this embodiment, the Li-containing slag obtained by the melting process S3 is characterized by having the following composition. Specifically, the Li-containing slag has the relationship Al / Li < 5 and silicon (Si) / Li < 0.7 in mass ratio, and contains Al in the proportion of 20% by mass or less, Li in the proportion of 3% by mass or more and 20% by mass or less, and Si in the proportion of 0% by mass or more and 7% by mass or less.

[0042] In the melting process that yields this type of Li-containing slag, the slag melting point can be appropriately controlled to below a predetermined temperature while suppressing the amount of flux added. Furthermore, because the amount of flux added can be suppressed, the amount of slag produced can be reduced, thereby obtaining slag with effectively concentrated Li.

[0043] The Li-containing slag obtained by the melting process can be used as a raw material for separating and extracting Li. Therefore, it is preferable that the amount of slag produced through the melting process be small, which increases the Li content and results in a Li-concentrated slag.

[0044] As for the Li-containing slag with the composition described above, a detailed explanation is omitted here, as it is as described above.

[0045] In the melting process, the flux added is preferably one that contains elements that incorporate impurity elements to form basic oxides with low melting points. Among these, it is more preferable to include calcium compounds because they are inexpensive and stable at room temperature. Specifically, calcium compounds such as calcium oxide and calcium carbonate can be used.

[0046] Furthermore, in the melting process, the process may be carried out in the presence of an oxidizing agent and a reducing agent in order to appropriately adjust the degree of oxidation-reduction when melting raw materials containing waste lithium-ion batteries. As the oxidizing agent, known agents can be used, and a solid oxidizing agent may be added, or a gaseous oxidizing agent may be introduced into the furnace. Similarly, as the reducing agent, known agents can be used, but a reducing agent containing carbon atoms is preferred. By adding a reducing agent containing carbon atoms, oxides of valuable metals such as Cu, Ni, and Co contained in waste lithium-ion batteries, which are to be recovered, can be easily reduced.

[0047] The heating temperature (melting temperature) in the melting process is not particularly limited, but it is preferably 1300°C or higher, and more preferably 1350°C or higher. By performing the melting process at a temperature of 1300°C or higher, valuable metals such as Cu, Ni, and Co are efficiently melted, and an alloy is formed with sufficiently high fluidity. Therefore, the separation efficiency of valuable metals and impurity components in the slag separation process S4 described later can be improved. If the heating temperature is less than 1300°C, the separation efficiency of valuable metals and impurities may be insufficient. Furthermore, the upper limit of the heating temperature in the melting process is preferably 1600°C or lower. If the heating temperature exceeds 1600°C, thermal energy is wasted, and the refractory materials such as the crucible and furnace walls are severely consumed, which may reduce productivity.

[0048] Furthermore, during the heating process in the melting treatment, the fluidity of the molten material is low and there are unmelted parts when the heating temperature is reached, so it is necessary to maintain the heating temperature for, for example, 30 minutes or more. Finally, it is preferable to observe the inside of the crucible and confirm that it has become a complete molten state using an iron measuring rod. After melting, the metal and slag, which have become more fluid, separate in the crucible due to their specific gravity, with the metal in the lower layer and the slag in the upper layer. After this, cooling and pulverization treatments are performed.

[0049] Furthermore, while dust and exhaust gases may be generated during the melting process, these can be rendered harmless by applying conventionally known exhaust gas treatment methods.

[0050] [Slag separation process] In the slag separation step S4, slag is separated from the reduced material obtained in the melting step S3 to recover the metal containing valuable metals. This yields the metal to be manufactured. As mentioned above, the metal, which is the reduced material, and the slag are separated in the crucible due to the difference in their specific gravity, so the molten metal can be efficiently recovered by separating the slag.

[0051] Furthermore, as mentioned above, the slag separated from the reduced material is a Li-containing slag with effectively concentrated Li, and by separating and recovering it from the reduced material, it can be used as a raw material for separating and extracting Li. [Examples]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0053] (1) Recovery of valuable metals [Examples 1-4] Valuable metals were recovered using waste lithium-ion batteries as raw materials. The recovery process was carried out according to the following steps.

[0054] <Pre-treatment process for waste batteries (preparation process)> As waste lithium-ion batteries, we prepared 18650 type cylindrical batteries, used prismatic batteries for automobiles, and defective batteries recovered during the battery manufacturing process. These waste batteries were immersed in salt water to discharge, then the moisture was removed, and the electrolyte was removed by roasting at 260°C in the air to obtain the battery contents.

[0055] <Grinding process (preparation process)> The obtained battery contents were crushed using a crusher (Good Cutter, manufactured by Ujiie Seisakusho Co., Ltd.). Next, the contents were separated using an aluminum separator that utilizes eddy currents, and then the crushed material was sieved using a sieve shaker to separate the aluminum as the top layer and the bottom layer as the battery charge.

[0056] <Oxidation roasting process> The resulting pulverized material (charge material) was subjected to oxidative roasting to obtain oxidative roasted material. Oxidative roasting was carried out using a rotary kiln at 900°C in air for 180 minutes.

[0057] <Reduction melting process> To the obtained oxidized roasted product, graphite was added as a reducing agent in a quantity equal to 0.6 times the total number of moles of valuable metals (Cu, Ni, Co), i.e., 1.2 times the number of moles required for the reduction of valuable metals, so that the slag composition would be as shown in Table 1 below. Furthermore, calcium oxide (CaO) was added as a flux so that the Al / Ca ratio of the slag was 2.28 to 2.67, and the mixture was mixed. The resulting mixture was then charged into an alumina (Al2O3) crucible.

[0058] Subsequently, the mixture charged into the crucible was heated and subjected to a reducing melting treatment to alloy the valuable metals, yielding a reduced product containing the alloy and slag (Li-containing slag). The reducing melting treatment was carried out by resistance heating at a temperature of 1450°C for 60 minutes. During the reducing melting treatment, the partial pressure of oxygen in the molten material was measured using an oxygen analyzer equipped with an oxygen probe (OXT-O, manufactured by Kawasou Electric Industries Co., Ltd.) at its tip. The partial pressure of oxygen was adjusted by adding graphite or by blowing in air using a lance.

[0059] <Slag separation process> The slag (Li-containing slag) was separated from the obtained reduced product, and the alloy was recovered, which was then designated as the recovered alloy.

[0060] [Comparative Example 1] The processing was carried out in the same manner as in the examples, except that Al separation was not performed in the grinding process. In the examples, the Al content in the raw material was 9% to 11% by mass, whereas in Comparative Example 1, the Al content in the raw material was 20% by mass.

[0061] (2) Evaluation <Slag component analysis> The component analysis of the Li-containing slag separated from the reduced material was performed as follows: the obtained slag was cooled, pulverized, and then chemically analyzed.

[0062] (3) Results Tables 1 and 2 below show the composition of the Li-containing slag obtained by the treatments of Examples 1-4 and Comparative Example 1. Table 3 below shows the treatment conditions, such as the amount of flux added and the amount of slag produced.

[0063] [Table 1]

[0064] [Table 2]

[0065] [Table 3]

[0066] As shown in the table above, in Comparative Example 1, the flux addition amount / raw material ratio was 0.39, while in Examples 1-3 it was 0.08, and in Example 4 it was 0.09. In addition, in Comparative Example 1 the slag production amount / raw material ratio was 0.95, while in Examples 1-3 it was 0.46-0.54, and in Example 4 it was 0.55.

[0067] In other words, by processing the slag to obtain the compositions of Examples 1 to 4, the amount of flux added can be reduced, thereby effectively suppressing the amount of slag generated. As a result, the Li in the slag is effectively concentrated, and Examples 1 to 3 contained 6% by mass or more of Li, while Example 4 contained 4% by mass or more of Li.

Claims

1. Li-containing slag obtained by melting raw materials including waste lithium-ion batteries containing lithium (Li) and aluminum (Al), In terms of mass ratio, Al / Li < 3.13 and silicon (Si) / Li < 0.

7. Al is 20% by mass or less. 3% by mass or more and 20% by mass or less of Li, It contains Si in a proportion of 0% by mass or more and 7% by mass or less. Li-containing slag.

2. A method for producing valuable metals from raw materials including waste lithium-ion batteries containing lithium (Li) and aluminum (Al), A pretreatment step including a process to remove the outer container made of Al from the raw material, The process includes a melting step in which the raw materials obtained through the aforementioned pretreatment step are melted to obtain Li-containing slag and metal containing valuable metals. The Li-containing slag obtained in the melting process is In terms of mass ratio, Al / Li < 3.13 and silicon (Si) / Li < 0.

7. Al is 20% by mass or less. 3% by mass or more and 20% by mass or less of Li, It contains Si in a proportion of 0% by mass or more and 7% by mass or less. A method for manufacturing valuable metals.

3. The pretreatment step includes a process of removing the outer casing made of Al by crushing and sieving the battery contents of the waste lithium-ion battery from the raw material, The method for producing a valuable metal according to claim 2.

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