Method for recycling waste lithium ion secondary battery and recycled lithium iron phosphate powder obtained thereby

Abstract

The purpose of the present invention is to provide a method for recovering a lithium iron phosphate powder as a positive electrode material in an economical and eco-friendly manner from a waste lithium ion secondary battery using lithium iron phosphate as a positive electrode material, and to provide a recycled lithium iron phosphate powder obtainable therefrom. In order to achieve the above object, the method for recycling a spent lithium ion secondary battery according to the present invention comprises: (a) loading an object to be heat-treated, which is at least a part of a spent lithium ion secondary battery in which a lithium iron phosphate powder is a positive electrode material, and which comprises the positive electrode material, into a heat treatment furnace, the method includes the steps of (a) heating an object to be heat-treated in a heat treatment furnace, (b) raising the temperature in the heat treatment furnace to a range of 200 DEG C to 400 DEG C, (c) maintaining the raised temperature to heat-treat the object to be heat-treated, and (d) discharging a first powder generated after the heat treatment is completed, where the first powder includes recycled lithium iron phosphate powder.

Description

Technical Field

[0001] This invention relates to recycled lithium iron phosphate powder that can be obtained by recycling waste lithium-ion batteries in which the cathode material is lithium iron phosphate, and a method for recycling waste lithium-ion batteries. More specifically, it relates to lithium iron phosphate powder that can be obtained by heat-treating waste lithium-ion secondary batteries at low temperature, and a method for recycling waste lithium-ion batteries. Background Technology

[0002] As the automotive industry transitions from internal combustion engine vehicles to electric vehicles, Europe and China, as global growth axes for electric vehicles and secondary batteries, are promoting expanded supply and competitive assurance of electric vehicles through CO2 regulations and environmentally friendly vehicle roadmaps. Therefore, the global electric vehicle market is expected to grow rapidly.

[0003] Since electric vehicle batteries are typically discarded after 5 to 10 years of use, the waste battery market is expected to be highly volatile. The global amount of waste electric vehicle batteries generated is estimated at approximately 160 to 2030 tons, and various European countries have invested heavily in developing methods to recover valuable metals from waste batteries.

[0004] Unlike reuse, the waste battery recycling industry recovers valuable metals from waste batteries and recycles these valuable metals as raw materials, which can solve environmental problems while simultaneously protecting valuable resources.

[0005] Typically, waste battery recycling involves discharging, dismantling, and grinding the waste batteries, and then extracting valuable metals through wet smelting or dry smelting processes. Dry smelting processes, which are suitable for large-scale processing and have high recovery rates, have attracted attention.

[0006] In dry smelting, the powder obtained by grinding is heated to a high temperature to remove organic compounds and polymer components contained in the ground powder, and then wet-ground again using strong acid to extract valuable metals.

[0007] The aforementioned dry smelting process requires a significant amount of time and equipment for discharge and grinding, and further complex processes, making it uneconomical. Moreover, the discharged product after high-temperature heating contains a large number of impurities, which reduces the extraction rate of valuable components that can be obtained from the whole powder. Furthermore, these impurities exist in a large quantity, requiring further grinding and the use of strong acids to extract the valuable components, which causes environmental problems.

[0008] In particular, in recent years, the application of lithium iron phosphate as a cathode material in lithium-ion secondary batteries has been increasing, so recovering lithium iron phosphate powder from waste lithium-ion secondary batteries has become an important task. Summary of the Invention

[0009] One object of the present invention is to provide a method for recovering lithium iron phosphate powder, which is used as a cathode material, from waste lithium-ion secondary batteries in an economical and eco-friendly manner, and to provide recyclable lithium iron phosphate powder that can be obtained therefrom.

[0010] To achieve the above objectives, the method for recycling waste lithium-ion secondary batteries according to the present invention is characterized by comprising: (a) loading an object to be heat-treated into a heat treatment furnace, said object being at least a portion of a waste lithium-ion secondary battery in which lithium iron phosphate powder is the positive electrode material, and including said positive electrode material; (b) raising the temperature inside said heat treatment furnace to a range of 200°C to 400°C; (c) maintaining said raised temperature to heat-treat the object to be heat-treated; and (d) discharging a first powder generated after heat treatment, wherein the first powder comprises recycled lithium iron phosphate powder.

[0011] Furthermore, the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention is characterized in that the first powder does not contain organic components, but contains 2 wt% or less of fluorine.

[0012] Furthermore, the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention is characterized in that the first powder does not contain organic components and fluorine.

[0013] Furthermore, the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention is characterized in that the gases generated in the heat treatment furnace in steps (b) and (c) are forcibly discharged.

[0014] Furthermore, the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention is characterized in that gas is forcibly discharged by generating a negative pressure state in the heat treatment furnace in steps (b) and (c).

[0015] The method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention is characterized in that, in steps (b) and (c), gas is forcibly discharged by a fan provided in a heat treatment furnace.

[0016] In the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention, the forced exhaust of gas by a fan can be performed intermittently.

[0017] In the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention, the object to be heat-treated in step (a) may be a positive electrode recovered by dismantling waste lithium-ion batteries.

[0018] In the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention, after step (d), the first powder is washed with water and subjected to a water washing treatment at a temperature of 30°C or lower.

[0019] In the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention, the first powder is further treated with acid after step (d).

[0020] In the method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention, the recycled lithium iron phosphate powder contained in the first powder may be a powder in which the conductive agent or coating remains intact.

[0021] The method for recycling waste lithium-ion secondary batteries according to an embodiment of the present invention may further include mixing recycled lithium iron phosphate powder with a lithium compound and heat-treating the mixture in the range of 600°C to 800°C.

[0022] Simultaneously, recycled lithium iron phosphate powder recovered by the method for recycling waste lithium-ion secondary batteries according to the present invention can be provided.

[0023] Alternatively, a lithium-ion secondary battery can be provided, which is manufactured using recycled lithium iron phosphate powder recovered by the method for recycling waste lithium-ion secondary batteries according to the present invention.

[0024] Beneficial effects

[0025] The method for recycling waste lithium-ion secondary batteries according to the present invention is economical and environmentally friendly, and thus increases the recycling rate of waste lithium-ion secondary batteries and solves the environmental problems that may occur during the recycling process.

[0026] Furthermore, highly economical lithium-ion secondary batteries can be manufactured by using recyclable lithium iron phosphate powder that is available according to the present invention. Attached Figure Description

[0027] Figure 1 An X-ray diffraction pattern of recycled lithium iron phosphate powder according to an embodiment of the present invention is shown;

[0028] Figure 2 This is a transmission electron microscope image of recycled lithium iron phosphate powder according to an embodiment of the present invention.

[0029] Figure 3 Raman spectral analysis results of recycled lithium iron phosphate powder according to an embodiment of the present invention are shown;

[0030] Figure 4The XRF analysis results of recycled lithium iron phosphate powder according to an embodiment of the present invention are shown;

[0031] Figure 5 Images and results of XRF analysis of the powders processed and recovered according to the comparative example are shown;

[0032] Figure 6 A scanning electron microscope image of recycled lithium iron phosphate powder recovered according to an embodiment of the present invention is shown, along with the results of energy-dispersive X-ray spectroscopy (EDX) plotting using that image; and

[0033] Figure 7 This is a graph showing an evaluation of the recycling properties of recycled lithium iron phosphate powder recovered according to an embodiment of the present invention. Detailed Implementation

[0034] In the following description, embodiments of the invention will be detailed with reference to the accompanying drawings, enabling those skilled in the art to readily practice these embodiments. However, the invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0035] Throughout this specification, when a component is referred to as "comprising" another component, it means that the component may further include other components, rather than excluding other components, unless otherwise specifically stated.

[0036] The terms “about,” “substantially,” etc., used herein are used in a meaning close to the numerical values ​​presented by manufacturing and material tolerances specific to the stated meaning, and are intended to prevent unethical individuals from misusing the statements of exact or absolute values ​​to aid in understanding the disclosure of this invention. Furthermore, the terms “a step-ing” or “a step of” used throughout the specification do not mean “a step for”.

[0037] Throughout the specification, the term "combination thereof" included in the Markush form of the description means one or more mixtures or combinations of the group consisting of the components described in the Markush form of the description, and means one or more of the group consisting of the components described.

[0038] Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

[0039] According to one aspect of the present invention, a method for recycling waste lithium-ion secondary batteries can be provided, the method comprising: (a) loading an object to be heat-treated into a heat treatment furnace, the object being at least a portion of a waste lithium-ion secondary battery wherein lithium iron phosphate powder is a positive electrode material, and including the positive electrode material; (b) raising the temperature within the heat treatment furnace to a range of 200°C to 400°C; (c) maintaining the raised temperature to heat-treat the object to be heat-treated; and (d) discharging a first powder generated after the heat treatment is completed, wherein the first powder comprises recycled lithium iron phosphate powder.

[0040] In this invention, the waste lithium-ion secondary batteries used for recycling are waste lithium-ion secondary batteries that use lithium iron phosphate as the positive electrode material.

[0041] The waste lithium-ion secondary batteries introduced into the heat treatment furnace can be entire waste lithium-ion secondary battery cells, or at least a portion thereof containing such lithium iron phosphate. Furthermore, it can be a black substance, which is powder generated from dismantling and pulverizing waste lithium-ion secondary batteries, or it can be waste lithium-ion secondary batteries discarded during the manufacturing process due to defects, etc.

[0042] Furthermore, in one embodiment of the present invention, in order to effectively recycle lithium iron phosphate, waste lithium-ion secondary batteries can be disassembled, and only the positive electrode in which the current collector and positive electrode material are combined can be separated and introduced into a heat treatment furnace.

[0043] A typical recycling process for waste lithium-ion batteries involves dismantling the batteries, pyrolyzing them at high temperatures, turning the pyrolyzed batteries into a single unit, and then pulverizing the unit. As a result, the waste lithium-ion batteries are ground in their original state, containing not only the recyclable positive and negative electrode materials, but also a large amount of impurities including the casing and current collectors. This causes the positive and negative electrode materials to deviate from their raw material state and undergo significant deformation.

[0044] In contrast, in the recycling method according to the invention, the electrolyte solution is removed by low-temperature heat treatment, and the binder contained in the positive electrode is decomposed, thereby allowing the lithium iron phosphate powder, which is the positive electrode material, to be easily separated from the current collector.

[0045] The recycled lithium iron phosphate powder, which is the positive electrode material separated as described above, can be reused in the manufacture of lithium-ion batteries as is, or it can be reused after processes such as simple cleaning or acid treatment.

[0046] In this invention, the heat treatment process for recovering and recycling lithium iron phosphate powder can be carried out in the range of 200°C to 400°C, 200°C to 350°C, or 250°C to 350°C. The battery is heated at a relatively low temperature, and the binder and electrolyte solution contained in the battery are removed by thermal decomposition. In particular, self-heating of components such as the binder and electrolyte solution can be achieved to realize pyrolysis.

[0047] Compared to typical recycling methods, heat treatment is performed at low temperatures, which reduces energy costs. Furthermore, since lithium iron phosphate powder, used as a cathode material, is recovered without damage through low-temperature heat treatment, the recovered powder can be recycled as is without separate post-processing, which requires significant time and cost.

[0048] Meanwhile, in steps (b) and (c) above, it is preferable to force the gas generated inside the heat treatment furnace to be discharged.

[0049] An important point regarding the emission of the aforementioned gases is that the gases produced by decomposition during the heat treatment of binders and electrolyte solutions contain fluorine. If these fluorine-containing gases are retained in the heat treatment furnace, they can combine with positive and negative electrode materials to form substances with strong bonds. If heat-treated powders are combined to form such substances, it is difficult to pulverize them even through post-processing such as grinding. Therefore, rapid emission of fluorine-containing gases is crucial. However, the high-temperature heat treatment in existing technologies inevitably leads to the rapid generation of gases containing fluorine components, resulting in prolonged retention of these gases in the heat treatment furnace, which accelerates powder aggregation.

[0050] In contrast, the waste lithium-ion secondary battery recycling method according to the present invention controls the decomposition rate of the binder and the like through low-temperature heat treatment, thereby suppressing the rapid generation of gases containing fluorine components, thus maintaining the amount of generated gases at an appropriate level, and at the same time forcibly venting the generated gases, thereby minimizing the time that gases containing fluorine components remain in the heat treatment furnace and preventing powder agglomeration caused by fluorine.

[0051] For the forced gas discharge during the heat treatment process described above, a negative pressure state can be maintained inside the heat treatment furnace. Because of this negative pressure, gases generated from the decomposition of binders, electrolyte solutions, separators, etc., caused by the heating of waste lithium-ion secondary batteries within the heat treatment furnace can be discharged to the outside. To maintain this negative pressure state, the heat treatment furnace can have a gas outlet and a pump connected to the outlet for maintaining the negative pressure state.

[0052] Additionally, the furnace atmosphere can be exhausted using a fan installed within the furnace. The fan can continuously or intermittently exhaust the decomposition gases generated in the heat treatment furnace. If the exhaust volume is too high, it may be difficult to raise and maintain the temperature inside the heat treatment furnace, thus requiring the exhaust to be intermittent in conjunction with the internal temperature.

[0053] Therefore, the negative pressure inside the heat treatment furnace can be maintained by combining temperature control within the furnace with the exhaust of the internal atmosphere via a fan.

[0054] Finally, by removing the internal organic matter and fluorine components, lithium iron phosphate, as a cathode material, can be recycled in powder form without the need for additional processes such as grinding, and the recycled lithium iron phosphate powder can be recycled back into the manufacture of new batteries as is.

[0055] The first powder recovered after heat treatment using the above-described waste lithium-ion secondary battery recycling method may include recycled lithium iron phosphate powder, but may not include organic components and fluorine. Since impurities such as binders are completely removed through low-temperature heat treatment and forced venting, the first powder does not contain organic components and fluorine. Therefore, the recycled lithium iron phosphate powder can be easily recovered in powder form and can be directly used to manufacture lithium-ion secondary batteries without any special reprocessing. Here, "no fluorine" means that fluorine was not detected in X-ray fluorescence spectrometry analysis.

[0056] Meanwhile, the aforementioned first powder may not contain organic components, but may include 2 wt% or less of fluorine. Even if it contains a small amount of fluorine, if the amount of fluorine is at a predetermined level or lower, the waste lithium-ion secondary batteries in powder form can be recycled without powder agglomeration.

[0057] Furthermore, the recycled lithium iron phosphate powder contained in the first powder discharged after the heat treatment process can be powder incorporating the conductive agent contained in the positive electrode. Simultaneously, the first powder can be treated with an acid such as hydrochloric acid to remove the incorporated conductive agent and recover pure lithium iron phosphate powder.

[0058] Meanwhile, the performance of recycled lithium iron phosphate powder may deteriorate due to insufficient lithium ions or develop a partially unstable structure due to repeated recycling. To restore the aforementioned deteriorated performance to the same level as the original performance, a method of mixing the powder with a lithium compound and subjecting the mixture to post-heat treatment can be adopted. Post-heat treatment can be carried out by mixing recycled lithium iron phosphate powder recovered according to general solid-phase methods with lithium carbonate or lithium hydroxide as a lithium compound, and heat-treating the mixture at a high temperature (600°C to 800°C).

[0059] [Example]

[0060] The recycling method according to the present invention processes waste lithium-ion secondary batteries using lithium iron phosphate as the positive electrode material to recover the first powder.

[0061] Undischarged waste lithium-ion batteries are placed in a heat treatment furnace, and then heat-treated while the furnace temperature is adjusted to 250°C. The temperature is raised over 6 hours and then maintained at that raised temperature for 12 hours. During the reaction, the internal atmosphere is exhausted by a fan, and the internal temperature is maintained within the range of 250±15°C using a temperature sensor.

[0062] After the reaction is complete, the powder material is recovered to obtain the first powder. The first powder is added to water, ultrasonicated, and filtered to separate and recover the lithium iron phosphate powder.

[0063] Figure 1 The X-ray diffraction analysis results of the recovered lithium iron phosphate powder are shown. It can be seen that the diffraction peaks of lithium iron phosphate appear strongly, while diffraction peaks of crystalline carbon also appear.

[0064] Figure 2 These are transmission electron microscopy (TEM) images of recovered lithium iron phosphate powder. It can be seen that carbon nanotubes and graphite, acting as conductive agents, are in a composite state.

[0065] Figure 3 The Raman analysis results of the recovered lithium iron phosphate powder after water washing are shown. It can be seen that the powder does not show peaks associated with organic matter other than lithium iron phosphate and carbon, indicating that the organic matter was completely removed.

[0066] Figure 4 The X-ray fluorescence (XRF) analysis results of the lithium iron phosphate powder recovered after water washing show that hydrofluoric acid was not detected.

[0067] at the same time, Figure 5 The diagram shows the powder recovered after heat treatment of a commercially available black substance at low temperature without emitting gases. As described above, the recovered powder is a hard lump, making it difficult to grind, and a significant amount of fluorine was detected in it.

[0068] Figure 6 The results show a scanning electron image of the recovered lithium iron phosphate powder and an energy-dispersive X-ray spectroscopy (EDX) plot using that image. It can be seen that the binder was completely removed from the recovered lithium iron phosphate powder, and the lithium iron phosphate cathode powder was preserved.

[0069] Figure 7The results of manufacturing a coin cell using recycled lithium iron phosphate powder and conducting battery testing on the coin cell are shown. The initial capacity was confirmed at a charge / discharge rate of 0.1°C, and cycle testing was performed at 0.5°C. The initial capacity was confirmed to be equal to the discharge capacity of lithium iron phosphate before typical recycling, and the cycle performance was also confirmed to be consistently maintained.

[0070] As described above, the recycled lithium iron phosphate powder recovered by the recycling method of waste lithium-ion batteries according to the present invention can be directly used in the manufacture of lithium-ion batteries without separate post-processing, thereby enabling the manufacture of highly economical lithium-ion batteries. Furthermore, since this method is carried out through low-temperature heat treatment, the recycling rate of waste lithium-ion secondary batteries can be improved and environmental problems that may occur during the recycling process can be addressed.

Claims

1. A method for recycling a spent lithium-ion secondary battery, the method comprising: (a) loading an object to be heat-treated into a heat treatment furnace, the object being at least a portion of a spent lithium-ion secondary battery in which lithium iron phosphate powder is a positive electrode material, and including the positive electrode material; (b) raising a temperature within the heat treatment furnace to a range of 200°C to 400°C; (c) maintaining the raised temperature to heat-treat the object to be heat-treated; and (d) discharging a first powder produced after the heat treatment is completed, wherein the first powder includes recycled lithium iron phosphate powder.

2. The method according to claim 1, wherein the first powder does not contain an organic component, but contains fluorine in an amount of 2 wt% or less.

3. The method according to claim 1, wherein the first powder does not contain an organic component and fluorine.

4. The method according to claim 1, wherein a gas produced within the heat treatment furnace in step (b) and step (c) is forcibly discharged.

5. The method according to claim 4, wherein in step (b) and step (c), the gas is forcibly discharged by creating a negative pressure state within the heat treatment furnace.

6. The method according to claim 4, wherein in step (b) and step (c), the gas is forcibly discharged by a fan provided in the heat treatment furnace.

7. The method according to claim 6, wherein forcibly discharging the gas by the fan is performed intermittently.

8. The method according to claim 1, wherein the object to be heat-treated in step (a) is a positive electrode recovered by disassembling the spent lithium-ion secondary battery.

9. The method according to claim 1, wherein after step (d), the first powder is washed with water, and the water washing treatment is performed with water at a temperature of 30°C or lower.

10. The method according to claim 1, further comprising, after step (d), subjecting the first powder to an acid treatment.

11. The method according to claim 1, wherein the recycled lithium iron phosphate powder contained in the first powder is a powder in which a conductive agent or a coating remains intact.

12. The method according to claim 1, further comprising mixing the recycled lithium iron phosphate powder with a lithium compound, and heat-treating the mixture at a range of 600°C to 800°C.

13. A recycled lithium iron phosphate powder recovered by the method for recycling a spent lithium-ion secondary battery according to any one of claims 1 to 12.

14. A lithium-ion secondary battery manufactured using a recycled lithium iron phosphate powder recovered by the method for recycling a spent lithium-ion secondary battery according to any one of claims 1 to 12.

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