Lithium recovery method

Abstract

The present invention relates to a method for efficiently recovering valuable metals from scrapped waste batteries in a dry smelting manner, and more particularly, to a lithium recovery method in which a flux and a sulfur component are mixed with crushed or crushed waste lithium batteries and then melted at a high temperature of 1400 DEG C or higher, and then a lithium sulfur compound (Li2S) volatilized therefrom is obtained.

Description

Technical Field

[0001] The present disclosure relates to a method for effectively recovering valuable metals from scrapped waste lithium batteries by a dry smelting method, and more particularly, to a lithium recovery method in which a flux and a sulfur component are mixed with shredded or crushed waste lithium batteries, then melted at a high temperature above 1400 °C, and then a lithium sulfide compound (Li2S) volatilized therefrom is obtained. Background Art

[0002] Waste batteries are generated because primary or secondary batteries, which are daily used as power sources for various electronic devices such as mobile phones, laptop computers, cassette toys, and emergency power supplies, reach the end of their service life.

[0003] These waste batteries contain harmful metals such as lead, cadmium, and mercury, and KOH, NH4Cl, lithium salts, H2SO4, and organic solutions are used as electrolytes; therefore, the environmental impact may not be negligible. In addition, since these batteries contain valuable metals such as silver, cobalt, nickel, zinc, manganese, and lithium, it is necessary to recycle waste batteries to protect the environment and effectively use limited resources.

[0004] In particular, since the 1990s, the demand for lithium-ion batteries (LiBs) has increased with the growth of the portable electronic device market, and due to the rapid expansion of the electric vehicle market, the demand has recently further increased worldwide.

[0005] Therefore, in the near future, the demand will greatly exceed the amount of lithium supplied from natural resources, which may bring instability to the lithium resource supply. In addition, the continuously accumulating waste batteries may also cause major environmental problems.

[0006] To solve these problems, it is very important to recycle used lithium secondary batteries. That is, if available materials can be recovered from waste batteries, less raw materials can be extracted from limited underground supply sources. In addition, if waste LiBs can be recycled, serious negative environmental impacts caused by mining and processing ores can be avoided.

[0007] Methods for recovering valuable metals contained in waste batteries include hydrometallurgy and pyrometallurgy.

[0008] Hydrometallurgy includes pretreatment, followed by leaching and selective precipitation to recover cathode materials, as well as additional purification and recovery techniques such as solvent extraction for ion exchange and extraction of valuable metals (see KR 10-2019-0084081). Due to the high valence state of the cathode active material and the strong binding force of the organic binder, some hydrometallurgical processes have the disadvantages of relatively long leaching times and low leaching efficiencies. In addition, the extensive use of highly concentrated acidic solutions and reducing agents, as well as complex processes, generate a large amount of wastewater, which may cause secondary pollution due to the discharge of wastewater and harmful gases during the leaching process. In particular, lithium may be dispersed during the separation and purification process, which may result in low lithium recovery rates.

[0009] To overcome these disadvantages and extract and purify metals, pyrometallurgical methods can be used (see KR 10-2021-0094615, KR 10-2313417, KR 10-0717389, and KR 10-2015-0096849). Pyrometallurgical recovery processes have the advantage of reducing processing and process costs because large-scale processing is possible due to rapid chemical reactions. In addition, the feed materials are relatively flexible, the process is simple, and the environmental impact of the slag is also at a relatively low level. Since the mixed waste batteries are directly loaded into the furnace for treatment without classification, the problems of fire and explosion hazards during the treatment of lithium batteries can be particularly solved, and the inert atmosphere for setting up a crushing process during the wet process is not considered.

[0010] However, the purity of the recovered metals is low, and there are limitations in recovering high-value-added metal powders. In addition, there is a disadvantage of needing to treat the exhaust gas generated during the process. In particular, since lithium is absorbed into the slag, there is also a problem of needing an additional process to utilize lithium.

[0011] In addition, most research results on lithium battery recycling focus on the separation and recovery of Co and Ni, and there is currently little research on Li.

[0012] Therefore, it is important to develop a revolutionary recycling process to more effectively extract and separate lithium from valuable metals in waste batteries containing a high ratio of heavy metals and toxic electrolytes. Summary of the Invention

[0013] Technical Problem

[0014] The present disclosure aims to eliminate the above limitations. One aspect of the present disclosure aims to provide a method in which, compared with conventional methods, by applying a dry smelting method in the recycling of waste lithium batteries, the process is simple and environmentally friendly, the processing speed is fast, and lithium is effectively recovered from the process side.

[0015] Technical Solution

[0016] To solve the above problems, a method for recovering lithium from waste lithium batteries according to an embodiment of the present disclosure includes: performing pretreatment of crushing or shredding on the waste lithium batteries; mixing a flux and a sulfur component with the pretreated waste lithium batteries; loading the mixture into a heating furnace and melting it at a high temperature above 1400 °C; and obtaining lithium sulfide compounds volatilized from the slag in the form of dust by air cooling.

[0017] The waste lithium batteries include any one of battery cells, cell packs, battery assemblies, or their waste materials.

[0018] The flux includes at least any one of SiO2, CaO, FeO, MnO, and Al2O3.

[0019] The sulfur component includes any one of sulfur, sulfide ions, sulfur compounds, sulfates, and sulfur mixtures.

[0020] The melting is carried out at a temperature of 1400 °C to 1800 °C.

[0021] The lithium sulfide compound may be Li2S.

[0022] The sulfur component may not be mixed with the flux but added during melting.

[0023] According to the lithium recovery method, a device for recovering lithium from the waste lithium batteries is provided.

[0024] According to the lithium recovery method, a lithium sulfide compound for all-solid-state batteries is provided.

[0025] Beneficial Effects

[0026] As described above, since waste lithium batteries directly crushed and shredded into pieces at the battery cell, cell pack, and battery module levels from an exemplary embodiment of the present disclosure are used, it has the effect of reducing the time and cost of the pretreatment process. Additionally, since the mixed waste batteries are directly loaded into a furnace for treatment without a sorting process, it can solve the problems of fire and explosion hazards during the treatment of lithium batteries.

[0027] Furthermore, since an exemplary embodiment of the present disclosure utilizes a dry smelting recovery process, the advantages are that there is no wastewater discharge and environmental pollution, and large-scale treatment can be carried out through rapid chemical reactions to reduce treatment and process costs.

[0028] In addition, from an exemplary embodiment of the present disclosure, more than 90% of lithium can be extracted, which is difficult to recover using conventional wet methods. Description of the Drawings

[0029] Figure 1 is a flowchart that step - by - step describes a lithium recovery method according to an exemplary embodiment of the present disclosure.

[0030] Figure 2 is a flowchart that step - by - step describes a lithium recovery method according to another exemplary embodiment of the present disclosure. Detailed Description of the Invention

[0031] Hereinafter, the present disclosure will be described in detail.

[0032] All terms and words used in this specification and the claims should not be construed as limited to their ordinary or dictionary meanings, but rather, based on the principle that the inventor can appropriately define terms to best explain his or her own invention, they should be construed as conforming to the meaning and concept of the technical concept of the present disclosure.

[0033] An exemplary embodiment of the present disclosure relates to a method for effectively recovering valuable metals from scrapped waste lithium batteries through a dry smelting method.

[0034] The term "lithium battery" used in this specification has the meaning of including all primary batteries, secondary batteries, or all - solid - state batteries containing lithium. Batteries that have reached the end of their service life or are discarded after use are collectively referred to as "waste lithium batteries".

[0035] Generally, different from secondary batteries, primary batteries cannot be recharged once used and are discarded. Secondary batteries are energy - saving devices that can be repeatedly charged / discharged approximately more than 500 times, and the battery can convert chemical energy into electrical energy and vice versa. Representative examples thereof include lithium - ion batteries, lithium - polymer batteries, nickel - cadmium batteries, nickel - metal hydride batteries, etc. Among them, compared with other secondary batteries, lithium - ion batteries have better energy storage capacity and lifespan.

[0036] In addition, a lithium - ion battery is configured with a positive electrode, a negative electrode, a separator, and an electrolyte, while an all - solid - state battery is a battery in which the electrolyte is not liquid but solid. Therefore, since an all - solid - state battery does not require safety devices or separators to cope with temperature changes and external impacts, costs can be reduced and high capacity with the same size can be achieved, and it has the advantage of being free from fire hazards.

[0037] As key materials used at the positive electrode of a lithium - ion battery, LCO (LiCoO2), NCM (Li[Ni, Co, Mn]O2), NCA (Li[Ni, Co, Al]O2), LMO (LiMn2O4), and LFP (LiFePO4) are used according to the components of metal salts. In addition, at the negative electrode, carbonaceous materials such as graphite or copper can be used.

[0038] According to an exemplary embodiment of the present disclosure, since the above component materials contain a large amount of valuable metals such as cobalt, copper, aluminum, steel, and lithium, a dry smelting method is used in one of the high-temperature heat treatment methods to effectively recover the valuable metals as economically valuable waste resources.

[0039] The term "smelting" generally refers to the use of heat and a chemical reducing agent to decompose ore in such a way that the metal remains after other elements are driven off into a gas or slag. At this time, the reducing agent is usually a carbon source such as coke or early charcoal. Carbon removes oxygen from the ore to leave elemental atoms. Therefore, carbon (C) is oxidized to produce carbon dioxide. Since most ores are impurities, rocks such as limestone used as fluxes need to be removed as slag.

[0040] Figure 1 is a flowchart that stepwise describes a lithium recovery method according to an exemplary embodiment of the present disclosure. To recover lithium from waste lithium batteries, an exemplary embodiment of the present disclosure includes: performing pretreatment of crushing or breaking on the waste lithium batteries; mixing a flux and a sulfur component (S) with the pretreated waste lithium batteries; loading the mixture into a heating furnace and melting it at a high temperature above 1400 °C; and obtaining a lithium sulfide compound volatilized from the slag in the form of dust by air cooling. In summary, an exemplary embodiment of the present disclosure relates to a method for recovering lithium as a lithium sulfide compound from waste lithium batteries. The lithium sulfide compound may be Li2S.

[0041] That is, when a sulfur component is added during the mixing process to produce Li2S from the slag according to the following chemical reaction formula, most of the lithium volatilizes into a gas and then is obtained in the form of dust by air cooling.

[0042] <Chemical reaction formula>

[0043] Li2O + S + CO(g) -> Li2S + CO2(g)

[0044] In this formula, since the Gibbs free energy ΔG < 0, it is a spontaneous reaction, and as the temperature rises, it reacts with S to form volatile Li2S. The boiling point of Li2S is 1372 °C, and its vapor pressure is about 1 atm at 1400 °C. Li2S volatilizes below 1400 °C.

[0045] Here, when the melting temperature is too high, the performance of removing impurities such as aluminum deteriorates. Therefore, the melting temperature is preferably in the range of 1400 °C to 1800 °C, and the melting time is also preferably maintained for more than 1 hour at the melting temperature.

[0046] Here, it is necessary to block oxygen during the temperature rise or inject an inert gas such as N2 or Ar to prevent the oxidation of the sulfur component (S).

[0047] As another exemplary embodiment of the present disclosure, the sulfur component is not mixed with the flux, but is added during the mixing step after the pretreatment step. However, it can also be added separately to the liquid charge during the melting step (see Figure 2 ).

[0048] Here, the amount of the sulfur component added can be used based on the stoichiometry of lithium in the charge. That is, 0.5 to 10 times the equivalent of lithium can be mixed, and preferably 2 to 4 times, but not limited thereto.

[0049] The above sulfur component can include not only sulfur, sulfide ions, sulfur compounds, sulfates, and sulfur mixtures, but also all sulfur compounds and mixtures containing sulfur. As examples of sulfur compounds, there are hydrogen sulfide, sulfur dioxide, sodium sulfide, copper sulfide, and nickel sulfide. In addition, as sulfates, there are copper sulfate, manganese sulfate, nickel sulfate, cobalt sulfate, magnesium sulfate, calcium sulfate, etc., but not limited thereto.

[0050] In particular, sulfur compounds are preferably used as the sulfur component, and the sulfur compounds can decompose into sulfur during the melting process.

[0051] The waste lithium batteries can be battery cells, battery packs, battery modules, or their scraps.

[0052] The flux of an exemplary embodiment of the present disclosure can include at least any one of SiO2, CaO, FeO, MnO, and Al2O3, which is charged into the refining furnace in the form of fine particles or powder. Considering the melting point, etc., the composition ratio of the components can vary, and additional components can also be used as needed.

[0053] Preferably, a CaO-based flux with high removal efficiency for aluminum, which is a large amount of impurity in waste lithium batteries, is used. The flux includes SiO2, MnO, Al2O3, etc. that all have sufficient viscosity at the melting temperature.

[0054] The amount of the flux can vary according to the type of waste battery, but 0.5 to 10 times the weight of the waste battery can be used, and preferably 2 to 5 times.

[0055] In summary, by controlling the amount of the sulfur component, the flux content, and the ratio of carbon as a reducing agent from the above chemical reaction formula, the lithium sulfide (Li2S) required for recovering waste lithium is obtained.

[0056] The Li2S evaporated into gas after generation can be separated or collected using a scrubber, bag filter, electrostatic precipitator, cyclone separator, etc.

[0057] <Exemplary Embodiment 1>

[0058] Crush 1 kg of spent lithium batteries that have reached the end of their service life into a size that is easy to load. Load the crushed spent lithium batteries together with 2 kg of a CaO-based flux containing SiO2, MnO, and Al2O3 into a heating furnace. At this time, insert and mix sulfur directly as a sulfur component, then heat the mixture in an Ar atmosphere at a heating rate of 5 °C / min or more to a temperature as high as 1500 °C, then add a small amount of oxygen to melt in a region with a low oxygen partial pressure, and keep the mixture in an Ar atmosphere for 1 hour to 3 hours so that the generated Li2S can volatilize. Thereafter, air-cool it and obtain it in the form of dust.

[0059] <Exemplary Embodiment 2>

[0060] When mixing sulfur, instead of adding sulfur directly, sulfur is added separately after melting and heated to melting. The others are carried out in the same manner as in Exemplary Embodiment 1.

[0061] <Exemplary Embodiment 3>

[0062] Use sodium sulfide instead of sulfur. The others are carried out in the same manner as in Exemplary Embodiment 1.

[0063] It can be confirmed that these methods are very suitable for recovering lithium from spent lithium batteries with a high recovery rate of more than 90%.

[0064] Solid electrolytes are characteristically used in all-solid-state batteries with improved density and stability compared to lithium-ion batteries, and since Li2S is a core material of solid electrolytes, the Li2S obtained according to an exemplary embodiment of the present disclosure can be recovered as a raw material for all-solid-state batteries.

Claims

1. A method for recovering lithium from waste lithium batteries, the method comprising: Pre-treat the waste lithium batteries by pulverizing or crushing them; Mix the flux and sulfur component with the pre-treated waste lithium batteries; Load the mixture into a heating furnace and melt it at a high temperature above 1400 °C; And Obtain the lithium-sulfur compound volatilized from the slag in the form of dust by air cooling.

2. The method according to claim 1, wherein, The waste lithium batteries include any one of battery cells, battery packs, battery modules, or their waste materials.

3. The method according to claim 1, wherein, The flux includes at least any one of SiO2, CaO, FeO, MnO, and Al2O3.

4. The method according to claim 1, wherein, The sulfur component includes any one of sulfur, sulfide ions, sulfur compounds, sulfates, and sulfur mixtures.

5. The method according to claim 1, wherein, The melting is carried out at a temperature of 1400 °C to 1800 °C.

6. The method according to claim 1, wherein, The lithium-sulfur compound is Li2S.

7. The method according to claim 1, wherein, The sulfur component is not mixed with the flux but is added during melting.

8. An apparatus for recovering lithium from waste lithium batteries according to the method for recovering lithium according to any one of claims 1 to 7.

9. A lithium-sulfur compound for all-solid-state batteries, obtained according to the method according to any one of claims 1 to 7.

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