Method for recovering lithium from secondary batteries by means of plasma electric arc furnace

Abstract

The present invention relates to a method for recovering lithium from secondary batteries by means of a plasma electric arc furnace, the method enabling lithium to be recovered, using plasma arc heat, at a very high recovery rate from black mass obtained by crushing secondary batteries. The method for recovering lithium from secondary batteries by means of a plasma electric arc furnace, of the present invention, comprises: a black mass production step of producing black mass through a pretreatment step of pulverizing or crushing waste lithium battery cells in order to recover lithium from waste lithium batteries; a flux addition step of adding CaO and Al2O3 to the black mass in a ratio of CaO:Al2O3 of 1-1.2 and adding CaCl2 and CaSO4 so as to adjust the molar ratio of LiCl : Li2SO4 to 1-1.2; a step of melting, in a plasma electric arc furnace, raw material to which flux is added; and a step of recovering lithium dust from the plasma electric arc furnace through a bag filter.

Description

Method for recovering lithium from a secondary battery by a plasma electric arc

[0001] The present invention relates to a method for recovering lithium from a secondary battery using a plasma electric arc, and more particularly to a method for recovering lithium from a secondary battery using a plasma electric arc capable of recovering lithium with a very high recovery rate from black mass obtained by crushing a secondary battery using plasma arc heat.

[0002] The demand for lithium-ion batteries (LiBs) has been increasing alongside the portable electronic device market since the 1990s, and has recently surged globally due to the rapid expansion of the electric vehicle market. As a result, the supply and demand of lithium resources could soon become a major issue, as much more lithium will be needed than can be obtained from natural resources. Furthermore, the continuous accumulation of waste batteries can also cause significant environmental problems.

[0003] To address these issues, the recycling of used lithium-ion batteries is crucial. If waste LiBs can be recycled, environmental damage can be reduced.

[0004] Hydrometallurgy and pyrometallurgy are methods for recovering valuable metals contained in spent batteries. Hydrometallurgy involves pretreatment to recover cathode materials, followed by additional purification and recovery techniques such as leaching, selective precipitation, ion exchange, and solvent extraction to extract valuable metals. Some hydrometallurgy processes have disadvantages, such as relatively long leaching times and low leaching efficiency, due to the high valence state of the cathode active material and the strong binding forces of organic binders. Furthermore, the extensive use of high-concentration acidic solutions and reducing agents, along with complex process steps, generates significant wastewater, which can cause secondary pollution through the emission of wastewater and harmful gases. In particular, lithium can become dispersed during these separation and purification steps, leading to low lithium recovery rates.

[0005] To overcome these disadvantages and extract lithium, a dry smelting method can be used. The dry smelting recycling process has the advantage of reducing processing and operation costs by enabling large-scale processing through rapid chemical reactions. Additionally, the feed materials are relatively flexible, the process is simple, and the environmental impact of dross is minimal. Mixed waste batteries can be directly charged into a blast furnace without undergoing a sorting process, which can resolve issues such as fire and explosion risks, particularly when processing lithium batteries. Furthermore, it eliminates the need to consider the creation of an inert atmosphere during the crushing process in wet smelting. However, the aforementioned dry smelting process has the disadvantages of low purity of recovered metals and the need for exhaust gas treatment during the processing. In particular, unlike other precious metals, lithium is absorbed into the slag along with low-cost metals, so there is also the issue that additional processes are required to effectively recover lithium.

[0006] Korean Registered Patent No. 10-2641852 (Title of Invention: Method for Recovering Lithium from Waste Lithium Batteries) discloses a lithium recovery method in which a flux containing a Ca compound and a sulfur component are mixed with crushed or shredded waste lithium battery cells, and the mixture is melted at a high temperature of 1300°C or higher to obtain a volatile lithium-sulfur compound (Li2SO4). However, since the lithium recovery rate of this conventional technology is approximately 90%, there is a need for a method that can recover lithium more efficiently to recycle resources, and there is a need to develop a process capable of recycling waste lithium batteries in large quantities.

[0007] The present invention was devised to solve the aforementioned conventional problems, and the objective of the present invention is to provide a method for recovering lithium from a secondary battery by a plasma electric arc that can achieve a high lithium recovery rate of 97% or more.

[0008] Another objective of the present invention is to provide a method for recovering lithium from a secondary battery by a plasma electric arc furnace that is environmentally friendly and capable of reducing waste generation by using clean energy.

[0009] Another objective of the present invention is to provide a method for recovering lithium from a secondary battery using a plasma electric arc, which can reduce the processing steps in the wet post-processing stage and recover high-quality lithium by removing impurities through high-temperature melting by the plasma electric arc.

[0010] Another objective of the present invention is to provide a method for recovering lithium from secondary batteries using a plasma electric arc furnace capable of processing waste batteries in large quantities and processing waste batteries of various specifications.

[0011] The method for recovering lithium from a secondary battery by a plasma electric arc of the present invention comprises: a black mass generation step of producing black mass through a pretreatment step of crushing or crushing spent lithium battery cells to recover lithium from spent lithium batteries; a flux addition step of adding CaO:Al2O3 to the black mass to adjust the ratio to 1 to 1.2, and adding CaCl2 and CaSO4 to adjust the molar ratio of LiCl:Li2SO4 to 1 to 1.2; a step of melting the raw material with the added flux in a plasma electric arc; and a step of recovering lithium dust from the plasma electric arc through a bag filter.

[0012] The method for recovering lithium from a secondary battery by a plasma electric arc of the present invention further comprises a step of producing black powder by reducing the black mass produced in the black mass generation step in a shaft reduction furnace.

[0013] In the method for recovering lithium from a secondary battery by a plasma electric arc of the present invention, the lithium dust is further recovered as lithium carbonate by a wet process.

[0014] According to the method for recovering lithium from a secondary battery by the plasma electric arc of the present invention with the above configuration, it is possible to recover lithium with a high recovery rate of 97% or more.

[0015] In addition, according to the present invention, by recovering lithium from a lithium secondary battery using clean energy, it becomes environmentally friendly and reduces waste generation.

[0016] In addition, according to the present invention, by removing impurities through high-temperature melting by a plasma electric arc furnace, the processing steps in the wet post-processing stage can be reduced, and high-quality lithium can be recovered.

[0017] In addition, according to the present invention, secondary battery waste can be processed in large quantities, and lithium can be recovered by processing waste batteries of various specifications.

[0018] FIG. 1 is a flowchart of a method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention.

[0019] FIG. 2 is a drawing showing a cross-section of a plasma electric arc according to the present invention.

[0020] Figure 3 is a photographic diagram showing the process of Example 2 of the method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention.

[0021] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0022] In this specification, the term "lithium battery" is used to include all primary batteries, secondary batteries, or all-solid-state batteries containing lithium, and lithium batteries that have reached the end of their lifespan or are discarded after use are collectively referred to as "waste lithium batteries."

[0023] FIG. 1 is a flowchart of a method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention, wherein the present invention comprises a black mass generation step (11), a black mass reduction step (13), a flux addition step (15), a melting step (17) in a plasma electric arc, and a lithium dust recovery step (19).

[0024] In order to recover lithium from waste lithium batteries, black mass (11) is produced by undergoing a pretreatment step of crushing or crushing waste lithium battery cells. As can be seen in the table below, the waste battery contains 45 to 55 wt% of black mass.

[0025]

[0026] The black mass is reduced by a reduction process (13) in a shaft reduction furnace to remove graphite, binder, and electrolyte, and the exhaust gas from the shaft reduction furnace is subjected to secondary combustion and discharged into the atmosphere through a scrubber. The shaft reduction furnace is operated at approximately 1400–1500°C along with the heat of graphite combustion, and oxides are reduced by graphite, and Li2CO3 / LiF is also produced. The black mass is burned at a rate of approximately 300–400 kg / h, and the weight loss is approximately 45–55 wt%.

[0027] When graphite is removed from black mass, it becomes black powder. Since the processing capacity of black powder in the subsequent recovery process is twice that of black mass, it is desirable to reduce black mass into black powder through a reduction process in a reduction furnace and recover lithium in the subsequent process.

[0028] Lithium has good reactivity with Al and Si, so LiAlO6, LiSiO4, LiAl(Si2O6), etc. are easily formed when making slag. To prevent this, CaO / Al2O3 is added in a ratio of 1 to 1.2 (15) to adjust the basicity, and a catalyst is used to allow Li to bond more than Al. In addition, to produce the lithium compound LiCl / Li2SO4, fluxes of CaCl2 and CaSO4 are mixed to adjust the molar ratio of LiCl and Li2SO4 to 1 to 1.2.

[0029] LiF has a vaporization temperature of 1,676°C and poor solubility in water. Li2CO3 has a vaporization temperature of 1,310°C but poor solubility in water, and Li2O has good solubility in water but a vaporization temperature of 2,600°C.

[0030] In contrast, the vaporization temperature of LiCl is 1,382°C and that of Li2SO4 is 1,377°C, which are relatively low. Since both LiCl and Li2SO4 have good solubility in water and are suitable for water leaching in subsequent processes, it is desirable to generate lithium dust of LiCl and Li2SO4 components. To this end, CaCl2 is added as a flux to provide Cl to the black mass.

[0031] The slag must be at least 1,450°C or higher, and the slag CaO / Al2O3 ratio must be adjusted to 0.8~1.2.

[0032] The raw material that has undergone the above-mentioned reduction step (13) and flux addition step (15) is subjected to 300KV of DC 250V / 1700A electricity in a plasma electric arc furnace (EAF) to produce lithium dust, Ni, Co, Cu alloy ingot (25), and CaO / Al2O3 slag (23).

[0033] FIG. 2 is a drawing showing a cross-section of a plasma electric arc according to the present invention.

[0034] At this time, the ratio of raw material quantity to (catalyst and CaCl2 or CaSO4) input is approximately 1:1, and it is input in the form of powder rather than pellets. The operating temperature is 1600-1650℃. The lithium dust is recovered (19) through a bag filter, and then lithium carbonate (21) is manufactured in a subsequent wet process.

[0035] [Example 1]

[0036] In Example 1 of the present invention, black mass or black powder was separated into Ni-Co alloy and lithium-containing dust in a small plasma electric arc furnace, and then the recovery rates of Ni, Co, and Li were measured.

[0037] The raw material components of Example 1 are as shown in Table 2 below.

[0038] Elemental Nickel (Ni) Cobalt Manganese Lithium Content (%) 54.22.5406.78

[0039] Here, the recovery rates of Ni, Co, and Li were evaluated as shown in Table 3 below.

[0040]

[0041] According to the measurement results of Example 1, 12% of the input raw material was left as dust, and the recovery rates of Ni and Co were confirmed to be over 98%, and the recovery rate of Li was over 95%.

[0042] [Example 2]

[0043] 120 kg of NCA-based waste batteries and 125 kg of a blended binder were mixed through a mixer for 10 minutes and then loaded into a plasma arc furnace. Nickel and cobalt were reduced to metal alloys, and lithium was converted into lithium compounds and collected as dust. As confirmed in Table 4 below, the lithium recovery rate is 97.19%.

[0044] Figure 3 is a photograph illustrating the test process of Example 2 of the method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention. As shown in the figure, Example 2 measured the lithium recovery rate through the steps of measuring the weight of the raw material, measuring the weight of the binder, mixing the raw material and the binder, adding the raw material, reacting with the plasma arc, and measuring the product after the reaction.

[0045]

Claims

1. A black mass generation step (11) for producing black mass by undergoing a pretreatment step of crushing waste lithium battery cells to recover lithium from waste lithium batteries; A flux addition step (15) in which CaO:Al2O3 is added to the black mass to a ratio of 1 to 1.2, and CaCl2 and CaSO4 are added to adjust the molar ratio of LiCl:Li2SO4 to 1 to 1.2; A step (17) of melting the raw material with the above flux added in a plasma electric arc furnace; and A method for recovering lithium from a secondary battery by a plasma electric arc, characterized by including the step (19) of recovering lithium dust from the above plasma electric arc through a bag filter.

2. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, further comprising a step (13) of reducing the black mass produced in the black mass generation step (11) in a shaft reduction furnace to produce black powder.

3. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized by further including a process (21) of recovering the lithium dust as lithium carbonate by a wet process.

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