Method for recovering lithium precursor from lithium secondary battery

Abstract

In the method for recovering lithium hydroxide from a lithium secondary battery, an electrode powder is prepared from a lithium secondary battery. A calcium compound is mixed with the electrode powder to produce a positive electrode active material mixture. The positive electrode active material mixture is reduced to form a preliminary precursor mixture. A lithium precursor is recovered from the preliminary precursor mixture. This makes it possible to obtain a lithium precursor with high purity without complicated leaching and additional processes that are caused by a wet-based process using an acid solution.

Description

[Technical Field]

[0001] The present invention relates to a method for recovering a lithium precursor from a lithium secondary battery, and more particularly to a method for recovering a high-purity lithium precursor from a used lithium secondary battery. [Background technology]

[0002] Secondary batteries are capable of repeated charging and discharging, and have been widely used in portable electronic communication devices such as camcorders, mobile phones, and laptops with the development of the information and communication and display industries. Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have been actively developed and applied due to their high operating voltage and energy density per unit weight, as well as their advantages of fast charging and lightweight design.

[0003] The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator, and an electrolyte solution impregnated in the electrode assembly. The lithium secondary battery may further include, for example, a pouch-shaped outer casing that accommodates the electrode assembly and the electrolyte solution.

[0004] The positive electrode active material of the lithium secondary battery can be a lithium composite oxide, which can further contain a transition metal such as nickel, cobalt, or manganese.

[0005] Since the positive electrode active material uses the aforementioned expensive valuable metals, the production of the positive electrode material accounts for more than 20% of the production cost. In addition, with the recent increase in interest in environmental protection, research into methods for recycling positive electrode active materials is progressing.

[0006] Conventionally, a method has been used in which waste cathode active material is leached in a strong acid such as sulfuric acid to sequentially recover valuable metals. However, the wet process has disadvantages in terms of regeneration selectivity and regeneration time, and can cause environmental pollution.

[0007] For example, Japanese Patent Application Laid-Open Publication No. 2019-178395 discloses a method for recovering lithium precursors using a wet method. However, this method does not take into account the reduction in purity due to impurities generated from materials and components other than the lithium precursor. Therefore, research is needed to recover lithium precursors with high purity using dry-based reactions. Summary of the Invention [Problem to be solved by the invention]

[0008] One object of the present invention is to provide a method for recovering a highly pure lithium precursor from waste lithium secondary batteries. [Means for solving the problem]

[0009] In a method for recovering a lithium precursor for a lithium secondary battery according to an exemplary embodiment, an electrode powder is prepared from a lithium secondary battery, a calcium compound is mixed with the electrode powder to produce a positive electrode active material mixture, the positive electrode active material mixture is reduced to form a pre-precursor mixture, and a lithium precursor is recovered from the pre-precursor mixture.

[0010] The lithium secondary battery according to some exemplary embodiments may include an End-of-Life (EOL) lithium secondary battery.

[0011] In some embodiments, the step of preparing the electrode powder can include dry-milling the lithium secondary battery.

[0012] In some embodiments, the electrode powder can include components derived from a positive electrode active material, a negative electrode active material, a binder, a conductive material, and an electrolyte.

[0013] In some embodiments, producing the positive electrode active material mixture or forming the pre-precursor mixture can include at least partially removing components from the negative electrode active material, the electrolyte, the conductive material, and the binder by reacting them with the calcium compound.

[0014] In some embodiments, the components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder can include a fluorine component and a carbon component.

[0015] In some embodiments, the calcium compound can include calcium oxide.

[0016] In some embodiments, reacting the calcium compound with the electrode powder may include mixing a calcium compound containing 0.5 to 1.5 times the amount of calcium element relative to the amount of fluorine element contained in the electrode powder.

[0017] In some embodiments, the step of preparing the cathode active material mixture can include heat treating the electrode powder and the calcium compound together at a temperature of 300 to 600°C, preferably 400 to 500°C.

[0018] In some embodiments, the reduction process can include dry reduction using hydrogen gas or a carbon-based material.

[0019] In some embodiments, the temperature of the reduction treatment may be 400 to 600°C.

[0020] In some embodiments, recovering the lithium precursor from the pre-precursor mixture can include washing the pre-precursor mixture with water to obtain a lithium precursor hydrate.

[0021] In some embodiments, the recovery of lithium hydroxide in the lithium precursor hydrate may be 93% or greater. [Effects of the Invention]

[0022] According to the above-described exemplary embodiment, lithium precursors can be recovered from waste lithium-ion batteries through a dry-based process using a dry reduction process, thereby obtaining lithium precursors with high purity without the complicated leaching and additional processes that would be caused by a wet-based process using an acid solution.

[0023] According to an exemplary embodiment, a calcium compound is mixed with waste electrode active material from EOL lithium secondary batteries, so that impurities such as hydrogen fluoride and carbon dioxide generated in the dry reduction process react with calcium before reacting with lithium, thereby improving the yield of lithium precursor. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic flow chart illustrating a method for recovering a lithium precursor of a lithium secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present invention provides a method for recovering lithium precursors from lithium secondary batteries in high purity and high yield by dry reduction reaction.

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below with reference to the accompanying drawings. However, these embodiments are merely illustrative and are not intended to limit the present invention.

[0027] The term "End-of-Life (EOL) lithium secondary battery" as used herein includes a battery that has been manufactured as a finished product and used to the end of its life, or a lithium secondary battery that has been manufactured as a finished product and used to the end of its life but has been discarded, even if its life has not yet ended. For example, it may be a battery that has experienced a 25% output reduction based on the USABC (United States Advanced Battery Consortium) standard.

[0028] The term "precursor" as used herein may refer collectively to a compound containing a specific metal to provide the specific metal contained in the electrode active material.

[0029] The term "electrode powder" as used herein may refer to a raw material that is input into the reduction reaction treatment described below after the positive and negative electrode current collectors have been substantially removed from the waste battery.

[0030] 1 is a schematic flow chart illustrating a method for recovering a lithium precursor for a lithium secondary battery according to an exemplary embodiment. For convenience of explanation, FIG. 1 shows both the process flow and a schematic diagram of a reactor.

[0031] Referring to FIG. 1, an electrode active material (eg, electrode powder) can be prepared from a lithium secondary battery (eg, step S10).

[0032] The process of recovering lithium from lithium secondary batteries may include, for example, a method of recovering lithium from scrap or a method of recovering lithium from EOL (End-of-Life) lithium secondary batteries.

[0033] The scrap includes cathode material scrap generated during the manufacturing process of cathode materials or secondary batteries. Because the scrap has never come into contact with an anode or has no history of use, the raw materials for the lithium precursor recovery process contain almost no impurities. In contrast, the EOL lithium secondary battery differs from the scrap in that it has been manufactured as a finished product and has a history of use. Therefore, in the case of the lithium precursor recovery process for EOL lithium secondary batteries, the starting material contains more impurities generated from the anode, electrolyte, etc. than the scrap.

[0034] For example, the impurity content, calculated as the mass ratio of impurities to the total mass of the electrode powder, of the EOL lithium secondary battery may be 8 times or more that of the scrap. The carbon content of the impurities of the EOL lithium secondary battery may be 12 times or more that of the scrap. The fluorine content of the impurities of the EOL lithium secondary battery may be 1.5 times or more that of the scrap.

[0035] The present invention can perform the process described below on EOL lithium secondary batteries, which can achieve a higher recovery rate of the lithium precursor than the cathode material scrap, despite the fact that the EOL lithium secondary batteries contain more impurities than the cathode material scrap.

[0036] The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and may include an electrolyte impregnating the electrode assembly. The positive electrode and the negative electrode may include a positive electrode active material layer and a negative electrode active material layer coated on a positive electrode current collector and a negative electrode current collector, respectively.

[0037] For example, the positive electrode active material contained in the positive electrode active material layer may include an oxide containing lithium and a transition metal.

[0038] In some embodiments, the positive electrode active material may include a compound represented by Formula 1:

[0039] [Chemical formula 1] Li x M1 a M2 b M3 c O y

[0040] In Chemical Formula 1, M1, M2, and M3 are Ni, Co, Mn 、T I, V, Cr, Cu, Zn 、A g 、Z r, Nb and M o or In Chemical Formula 1, 0 may be a transition metal selected from the group consisting of: <x≦1.1、2≦y≦2.02、0<a<1、0<b<1、0<c<1、0<a+b+c≦1であってもよい。

[0041] In some embodiments, the positive electrode active material may be an NCM-based lithium oxide containing nickel, cobalt, and manganese, where M1, M2, and M3 in Formula 1 may be Ni, Co, and Mn, respectively.

[0042] The positive electrode active material layer may contain a conductive material and a binder in addition to the positive electrode active material.

[0043] The conductive material may be included to promote electron transfer between active material particles, and may include, for example, carbon-based materials such as graphite, carbon black, graphene, and carbon nanotubes, or metal-based materials including tin, tin oxide, titanium oxide, and perovskite materials such as LaSrCoO3 and LaSrMnO3.

[0044] Examples of the binder include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, styrene butadiene rubber (SBR), polyvinyl alcohol, polyacrylic acid (PAA), carboxymethyl cellulose (CMC), hydroxypropyl cellulose, diacetylcellulose, etc. The above-mentioned exemplary binders can be used not only in the positive electrode but also in the negative electrode.

[0045] According to an exemplary embodiment, the negative electrode active material may be any material known in the art that can absorb and desorb lithium ions, without any particular limitation. For example, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, and carbon fibers; lithium alloys; silicon (Si)-based compounds; and tin.

[0046] In some embodiments, the negative electrode active material layer can include both a conductive material and a binder in addition to the negative electrode active material described above.

[0047] The conductive material may be, for example, substantially the same as or similar to the material used to form the positive electrode.

[0048] In some embodiments, the electrolyte solution can be a non-aqueous electrolyte solution. The non-aqueous electrolyte solution contains a lithium salt as an electrolyte and an organic solvent. The lithium salt is, for example, Li + X - The anion (X - ) as F -, Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - Examples include:

[0049] According to an exemplary embodiment, the step of preparing the electrode powder may include the steps of separating waste batteries into cell units, discharging the cells, and separating current collectors from the cells.

[0050] In some embodiments, the step of separating the waste battery into cell units may include the steps of separating a case and an electric wire of the waste battery, separating the waste battery into module units, and separating the module units again into cell units.

[0051] Even if the battery is a waste battery, residual electric charge may remain in the lithium ion battery, which may cause sparks or other damage during processing, leading to a risk of fire. Therefore, lithium secondary batteries may be discharged before being processed.

[0052] In some embodiments, the discharge can be performed by immersing the EOL lithium ion battery in salt water, in which case the salt water discharge can be performed for 72 hours or more.

[0053] In some embodiments, the discharge can be performed using a separate discharger. For example, in the case of saltwater discharge, salt may adhere to the cell or lithium may dissolve in the saltwater, which may reduce the recovery rate of the lithium precursor in the recovery process described below. Therefore, discharge using a discharger may be more advantageous in the lithium precursor recovery process.

[0054] In an exemplary embodiment, the step of separating the current collector from the lithium secondary battery may include a step of separating the electrode active material layer from the electrode current collector. In some embodiments, the step of separating the current collector from the lithium secondary battery may be performed simultaneously with dry-pulverizing the cell that has undergone the discharging step, as described below.

[0055] According to an exemplary embodiment, the step of preparing the electrode powder may include dry-milling the lithium secondary battery, so that the electrode powder may be prepared in a powder form.

[0056] In some embodiments, the separated electrode active material layer may be pulverized to produce an electrode powder, which may be produced in a powder form and collected in the form of, for example, black powder.

[0057] In an exemplary embodiment, the electrode powder may contain not only a positive electrode active material, but also some components derived from a negative electrode active material, an electrolyte, a conductive material, and a binder.

[0058] In some embodiments, the electrode powder may have an average particle size (D50) (average particle size in cumulative volume distribution) of 5 to 100 μm, which allows the reduction reaction to be easily carried out in a fluidized bed reactor, as described below.

[0059] For example, in step S20, a calcium compound may be mixed with the electrode powder to prepare a positive electrode active material mixture.

[0060] In some embodiments, the step of preparing the positive electrode active material mixture or the step of forming a pre-precursor mixture described below can include at least partially removing components from the negative electrode active material, the electrolyte, the conductive material, and the binder by reacting them with the calcium compound.

[0061] In some embodiments, the components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder may include a fluorine component and a carbon component. When the fluorine component and the carbon component react with lithium, they form lithium fluoride (LiF) and lithium carbonate (Li2CO3), resulting in a decrease in the yield of the lithium precursor. Therefore, when a calcium compound is mixed with an electrode powder to produce a positive electrode active material mixture, the fluorine component and the carbon component can react first with calcium during the heat treatment or reduction treatment described below to form calcium fluoride (CaF2) and calcium carbonate (CaCO3).

[0062] According to an exemplary embodiment, the calcium compound may preferably include calcium oxide (CaO). By mixing calcium oxide into the electrode powder, the fluorine component and the carbon component react with calcium before reacting with lithium, thereby preventing lithium from reacting with impurities. Therefore, the yield of the lithium precursor, which is the target of recovery, can be improved.

[0063] According to an exemplary embodiment, reacting the calcium compound with the electrode powder may include mixing a calcium compound containing 0.5 to 1.5 times the amount of calcium element relative to the amount of fluorine element contained in the electrode powder. This range optimizes the reaction of the calcium compound with hydrogen fluoride (HF) and carbon dioxide (CO2), which helps to improve the recovery rate of the lithium precursor.

[0064] In some embodiments, the cathode active material mixture may be heat-treated before being introduced into the reductive reactor 100 described below. The heat treatment may remove or reduce impurities, such as the anode active material, the electrolyte, the conductive material, and the binder, contained in the waste cathode active material mixture. This allows the lithium-transition metal oxide to be introduced into the reductive reactor with high purity.

[0065] According to an exemplary embodiment, the step of preparing the positive electrode active material mixture may include heat treating the electrode powder and the calcium compound together at a temperature of 300 to 600°C, preferably 400 to 500°C.

[0066] According to an exemplary embodiment, the step of preparing the positive electrode active material mixture may include at least partially removing components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder by reacting them with the calcium compound. The components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder may include a fluorine component and a carbon component. For example, when heat-treated at a temperature of 400 to 600°C, components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder, such as hydrogen fluoride and carbon dioxide, may react with calcium before lithium to form calcium fluoride (CaF2) and calcium carbonate (CaCO3).

[0067] The temperature of the heat treatment may be, for example, about 600° C. or less, about 300 to 600° C. in one embodiment, and preferably about 400 to 500° C. Within this range, the impurities are substantially removed, and decomposition and damage to the lithium-transition metal oxide can be prevented.

[0068] In one embodiment, the heat treatment can be performed in a reducing reactor 100. In this case, a carrier gas such as nitrogen (N), helium (He), or argon (Ar) can be injected through a reactant gas passage 102 connected to the lower reactor portion 110, and fluidized heat treatment can be performed in the reducing reactor 100.

[0069] In one embodiment, the cathode active material mixture may be separately heat-treated before being charged into the reducing reactor 100 .

[0070] For example, in step S30, the positive electrode active material mixture may be reduced in a reducing reactor 100 to form a pre-precursor mixture 80.

[0071] 1, the reductive reactor 100 can be divided into a reactor body 130, a reactor lower part 110, and a reactor upper part 150. The reactor body 130 may include a heating means such as a heater, or may be integrated with the heating means.

[0072] The positive electrode active material mixture may be supplied to the reactor body 130 through the supply passages 106a and 106b. The positive electrode active material mixture may be dropped through the first supply passage 106a connected to the upper portion 150 of the reactor or may be added through the second supply passage 106b connected to the bottom of the reactor body 130. In one embodiment, the positive electrode active material mixture may be supplied using both the first and second supply passages 106a and 106b.

[0073] For example, the positive electrode active material mixture powder may be fixed by disposing a support 120 between the reactor main body 130 and the reactor lower portion 110. The support 120 may include pores or injection holes through which a reducing reactant gas and / or a carrier gas passes during the reduction process described below.

[0074] A reducing reactant gas for converting the positive electrode active material mixture into a pre-precursor can be supplied into the reactor body 130 through a reactant gas passage 102 connected to the reactor lower portion 110 .

[0075] According to an exemplary embodiment, the reduction process may include dry reduction using hydrogen gas or a carbon-based material.

[0076] In some embodiments, the reducing gas provided during the reduction process may include hydrogen (H) gas, and may further include a carrier gas such as nitrogen (N) or argon (Ar).

[0077] In some embodiments, the concentration of hydrogen in the reducing reactant gas may be about 10-40% by volume (vol %), or the concentration of hydrogen may be the vol % of hydrogen in the total volume of the mixed gas.

[0078] According to an exemplary embodiment, the temperature of the reduction treatment can be adjusted in the range of about 400 to 800°C, preferably in the range of about 400 to 600°C, and more preferably in the range of about 400 to 500°C.

[0079] In addition, the reduction treatment can be finely adjusted by adjusting process conditions such as hydrogen concentration, reaction temperature, and reduction reaction time.

[0080] During the reduction process, hydrogen gas may be supplied from the lower part of the reducing reactor 100 and contact the positive electrode active material mixture. As a result, the positive electrode active material mixture may react with the reducing reactant gas while moving to the upper part 150 of the reactor or while remaining in the reactor body 130, and may be converted into the pre-precursor mixture 80.

[0081] In some embodiments, during the reduction process, hydrogen gas or a carrier gas may be injected to form a fluidized bed in the reactor body 130. Therefore, the reduction reactor 100 may be a fluidized bed reactor.

[0082] That is, according to an exemplary embodiment, the step of forming the pre-precursor mixture 80 may include subjecting the cathode active material mixture to the reduction treatment in a fluidized bed reactor.

[0083] The repeated up-flow, dwell, and down-flow of the cathode active material mixture in the fluidized bed increases the reaction contact time and promotes particle dispersion, thereby obtaining a pre-precursor mixture 80 with a uniform particle size.

[0084] However, the concept of the present invention is not necessarily limited to a fluidized bed reaction. For example, a stationary reaction can be performed by preloading a cathode active material mixture into a batch reactor or a tubular reactor and then supplying a reducing reactant gas.

[0085] In some embodiments, the reduction process of the lithium-transition metal oxide may produce a pre-lithium precursor 60 including, for example, lithium hydroxide (LiOH), a lithium oxide (e.g., LiO), and a transition metal or transition metal oxide.

[0086] For example, as the reduction process progresses, the crystalline structure of Li(NCM)O2 may be disrupted and Li may leave the crystalline structure, while NiO and CoO may be produced from the crystalline structure, and as the reduction process continues, Ni and Co phases may be produced together.

[0087] The step of forming the preliminary precursor mixture 80 may include at least partially removing components from the negative electrode active material, the electrolyte, the conductive material, and the binder by reacting them with the calcium compound.

[0088] The components derived from the negative electrode active material, the electrolyte, the conductive material, and the binder may include a fluorine component and a carbon component. When the fluorine component and the carbon component react with lithium, lithium fluoride (LiF) and lithium carbonate (Li2CO3) are formed, resulting in a decrease in the yield of the lithium precursor. Therefore, by including calcium oxide as a calcium compound in the positive electrode active material mixture, impurities generated during the high-temperature reduction treatment, such as hydrogen fluoride (HF) and carbon dioxide (CO2), can be induced to react first with calcium.

[0089] For example, by generating calcium fluoride (CaF) and calcium carbonate (CaCO) before lithium fluoride (LiF) and lithium carbonate (LiCO), the yield of lithium precursor particles 60 in the preliminary precursor mixture 80 can be improved, thereby significantly improving the recovery rate of the target product.

[0090] After the reduction process, a pre-precursor mixture 80 including preliminary lithium precursor particles 60 and transition metal-containing particles 70 (e.g., the transition metal or transition metal oxide) can be formed within the reactor body 130. The preliminary lithium precursor particles 60 can include, for example, lithium hydroxide (LiOH), lithium oxide (LiO), and / or lithium carbonate (LiCO), and can preferably be lithium hydroxide (LiOH).

[0091] According to an exemplary embodiment, recovering the lithium precursor from the pre-precursor mixture 80 may include washing the pre-precursor mixture 80 with water to obtain a lithium precursor hydrate (e.g., step S40).

[0092] For example, the pre-precursor mixture 80 obtained by the dry reduction process can be collected for a subsequent recovery process.

[0093] In one embodiment, the transition metal-containing particles 70, including nickel, cobalt, or manganese, are relatively heavier than the preliminary lithium precursor particles 60, which can be collected first via outlets 160a, 160b.

[0094] In one embodiment, the preliminary lithium precursor particles 60 can be discharged through a first outlet 160a connected to the upper portion of the reactor 150. In this case, selective recovery of the preliminary lithium precursor particles 60 can be facilitated by a weight gradient.

[0095] In one embodiment, a pre-precursor mixture 80 containing the preliminary lithium precursor particles 60 and the transition metal-containing particles 70 can be collected through a second outlet 160b connected to the reactor body 130. In this case, the pre-precursor mixture 80 can be directly recovered in the fluidized bed formation zone, thereby improving the yield.

[0096] In one embodiment, the pre-precursor mixture 80 may be collected via first and second outlets 160a, 160b.

[0097] The spare lithium precursor particles 60 collected via the outlet 160 can be recovered as lithium precursor.

[0098] For example, water (eg, distilled water) may be directly added to the reactor body 130 to recover the lithium precursor from the pre-precursor mixture 80 obtained by the dry reduction process.

[0099] In some embodiments, the preliminary lithium precursor particles 60 in the preliminary precursor mixture 80 can be subjected to a water washing process. The water washing process allows the preliminary lithium precursor particles in the form of lithium hydroxide (LiOH) to be substantially dissolved in water and separated and preferentially recovered from the transition metal precursor. The lithium hydroxide dissolved in water can be subjected to a crystallization process or the like to obtain a lithium precursor substantially composed of lithium hydroxide (lithium precursor hydrate).

[0100] According to an exemplary embodiment, the recovery rate of lithium hydroxide in the lithium precursor hydrate may be 93% or more. Here, "recovery rate" refers to the product of conversion rate and selectivity. The "conversion rate" refers to the weight ratio of lithium dissolved in water to the weight of lithium in the initial electrode powder. The "selectivity" refers to the weight ratio of lithium compounds (e.g., lithium hydroxide, lithium carbonate, or lithium fluoride) remaining in the aqueous solution to the weight of lithium dissolved in water. This allows high-purity lithium precursor hydrate to be recovered from used lithium secondary batteries.

[0101] According to an exemplary embodiment, when the above-described lithium precursor recovery step is performed on an EOL lithium secondary battery, the recovery rate of the lithium hydroxide can be made higher than when the step is performed on scrap.

[0102] In one embodiment, the reserve lithium precursor particles in the form of lithium oxide and lithium carbonate can be substantially removed by the water washing process, hi one embodiment, the reserve lithium precursor particles in the form of lithium oxide and lithium carbonate can be at least partially converted to lithium hydroxide by the water washing process.

[0103] If necessary, the preliminary lithium precursor particles 60 can be reacted with a carbon-containing gas such as carbon monoxide (CO) or carbon dioxide (CO) to obtain lithium carbonate (e.g., LiCO) as a lithium precursor. The reaction with the carbon-containing gas can produce a crystallized lithium precursor. For example, a carbon-containing gas can be injected during the water washing process, and lithium carbonate can be collected.

[0104] The temperature of the crystallization reaction using the carbon-containing gas may be, for example, in the range of about 60 to 150° C. Within this temperature range, highly reliable lithium carbonate can be produced without damaging the crystal structure.

[0105] As previously mentioned, according to exemplary embodiments, lithium precursors can be recovered from spent cathodes by a series of dry processes.

[0106] According to embodiments of the present invention, lithium precursors are collected through a dry reduction reaction that eliminates the use of solutions, thereby reducing by-products, increasing yields, and enabling the design of environmentally friendly processes that do not require wastewater treatment.

[0107] Specific examples are presented below to aid in understanding the present invention, but these examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications can be made to these examples within the scope and technical spirit of the present invention, and it is natural that these changes and modifications also fall within the scope of the appended claims.

[0108] Example 1 Battery cases and wires were removed from EOL (End-of-Life) waste batteries to obtain lithium secondary batteries in cell units. The EOL lithium secondary batteries in cell units were discharged using a discharger and then cut into several centimeter-long pieces using a shredder and a cut crusher. The electrode active material on the aluminum and copper foil current collectors was separated from the cut cells using an impact crusher. The aluminum and copper were then removed using a twist screen, and the resulting cells were heat-treated at 450°C for 1 hour and pulverized by milling to obtain 1 kg of electrode powder.

[0109] 200 g of the electrode powder was mixed with 7 g of calcium oxide to prepare a positive electrode active material mixture, which was then introduced into a fluidized bed reactor.

[0110] While the internal temperature of the reactor was maintained at 480°C, 100% nitrogen gas was injected from the bottom of the reactor at a flow rate of 5.5 L / min, and fluidization heat treatment was carried out for 3 hours.

[0111] After the heat treatment process, the reactor temperature was lowered to 460°C, and a mixed gas of 20 vol% hydrogen and 80 vol% nitrogen was injected into the bottom of the reactor at a flow rate of 5.5 L / min for 4 hours to carry out a reduction reaction. During this time, the internal temperature of the fluidized bed reactor was maintained at 460°C. After the reduction reaction, the reactor temperature was lowered to 25°C to obtain a pre-precursor mixture.

[0112] The resulting pre-precursor mixture and water (19 times by weight) were mixed together and stirred. The concentration of lithium dissolved in the water was analyzed, and the lithium conversion rate was determined by the weight ratio of the lithium dissolved in the water to the weight of the lithium in the initial electrode powder.

[0113] The selectivity was also measured depending on the molar concentrations of lithium hydroxide, lithium carbonate, and lithium fluoride remaining in the aqueous solution.

[0114] Comparative Example Comparative Example 1 Except for not containing calcium oxide, the process was carried out in the same manner as in Example 1. The evaluation results are summarized in Table 1 below.

[0115] Comparative Example 2 The same process as in Example 1 was carried out except that the electrode powder was produced from used positive electrodes derived from scrap, rather than from lithium-ion batteries. However, in this case, the process of separating the used batteries into cells and discharging them, as in Example 1, was omitted. The evaluation results are summarized in Table 1 below.

[0116] [Table 1]

[0117] From Table 1, it was confirmed that in the process of recovering a lithium precursor from an EOL lithium secondary battery, when calcium oxide was included within the range according to the above-described embodiment of the present invention, the lithium conversion rate and the recovery rate of the lithium precursor were significantly high. It was also confirmed that lithium carbonate and lithium fluoride were converted to calcium carbonate and calcium fluoride. Furthermore, it was confirmed that the recovery rate of lithium hydroxide was higher when the recovery process was performed using electrode powder from an EOL battery compared to electrode powder from scrap.

Claims

1. Preparing an electrode powder from a lithium secondary battery; mixing calcium oxide (CaO) with the electrode powder to prepare a positive electrode active material mixture; performing a dry reduction process on the positive electrode active material mixture to form a pre-precursor mixture; and recovering the lithium precursor from the preliminary precursor mixture.

2. 2. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1, wherein the lithium secondary battery includes an EOL (End-of-Life) lithium secondary battery.

3. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1 , wherein the step of preparing the electrode powder comprises dry-pulverizing the lithium secondary battery.

4. 2. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1, wherein the electrode powder contains components derived from a positive electrode active material, a negative electrode active material, a binder, a conductive material, and an electrolyte.

5. 5. The method for recovering a lithium precursor from a lithium secondary battery according to claim 4, wherein the step of producing the positive electrode active material mixture or the step of forming the preliminary precursor mixture comprises at least partially removing components derived from the negative electrode active material, the electrolyte solution, the conductive material, and the binder by reacting them with the calcium oxide.

6. The method for recovering a lithium precursor from a lithium secondary battery according to claim 5 , wherein the components derived from the negative electrode active material, the electrolyte solution, the conductive material, and the binder include a fluorine component and a carbon component.

7. 7. The method for recovering a lithium precursor from a lithium secondary battery according to claim 6, wherein reacting the electrode powder with the calcium oxide comprises mixing calcium oxide containing 0.5 to 1.5 times the amount of calcium element relative to the amount of fluorine element contained in the electrode powder.

8. 2. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1, wherein the step of preparing the positive electrode active material mixture comprises heat-treating the electrode powder and the calcium oxide together at a temperature of 300 to 600°C.

9. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1 , wherein the dry reduction treatment uses hydrogen gas or a carbon-based substance.

10. 2. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1, wherein the temperature of the dry reduction treatment is 400 to 600°C.

11. 2. The method for recovering a lithium precursor from a lithium secondary battery according to claim 1, wherein the step of recovering the lithium precursor from the pre-precursor mixture includes washing the pre-precursor mixture with water to obtain a lithium precursor hydrate.

12. 12. The method for recovering a lithium precursor from a lithium secondary battery according to claim 11, wherein the recovery rate of lithium hydroxide in the lithium precursor hydrate is 93% or more.

Images