Method for obtaining pure graphite from extraction residues of waste lithium ion batteries

Abstract

With the wide use of lithium ion batteries (LIBs), the recovery and reuse of LIBs attract wide attention. However, recycling and recovery of graphite anode material are neglected due to low added values and harsh separation steps. Although some direct physical recovery methods have been reported, all these methods are limited by harsh separation steps and laboratory scale. The invention relates to a method for recovering high-purity graphite from extraction residues of waste lithium ion batteries. The method is simple and easy to implement, and 99.9% pure graphite is provided. In addition, the method for recovering the high-purity graphite is clean, green, environmentally friendly and commercially feasible.

Description

Technical Field

[0001] The present invention relates to the recovery of graphite from waste lithium - ion batteries. More specifically, the present invention relates to a method for recovering graphite from the leaching residue of waste lithium - ion batteries, which is environmentally friendly, commercially viable, and economically attractive. Background Art

[0002] From the first discovery in the 1970s to the Nobel Prize in 2019, the use of lithium - ion batteries (LIBs) has grown exponentially. As the world becomes increasingly dependent on the power and convenience brought by LIBs, the manufacturing and processing of LIBs have increasingly become the subject of political and environmental issues.

[0003] Due to the complex structure and diverse materials of lithium - ion batteries, the batteries must undergo various treatments before reuse / recycling. LIBs must first be classified, and usually also require pretreatment by discharging or passivation, disassembly, and separation, and then direct recycling, pyrometallurgy, hydrometallurgy, or a combination of multiple methods for LIBs.

[0004] Currently, graphite is the most advanced anode material for commercial lithium - ion batteries due to its high reversible capacity and good cycle stability. Waste graphite anodes account for 12 wt% to 21 wt% of the battery, containing metals, binders, toxic, and flammable electrolytes. The efficient recovery of waste graphite is an urgent need for environmental protection and sustainable resource development. The prior art describes various recovery and treatment methods such as deep purification, selective lithium extraction, and residual electrolyte removal and their limitations. According to different graphite structural characteristics (including as raw materials for anode materials or catalysts, graphene, and composite membranes), diversified resource recovery routes for recovering graphite and its products are summarized.

[0005] CN111072023B discloses a method for recovering graphite from waste lithium - ion batteries. The total mechanical - crushed lithium - ion battery waste is subjected to alkali leaching and acid leaching to obtain crude graphite and a filtrate containing cobalt, iron, nickel, and manganese metals. This method has a simple process, low cost, low energy consumption, and the recovered graphite has good stability. Calcination is carried out at 500 °C to obtain graphite residue.

[0006] CN112320794 A discloses a method for deep impurity removal of graphite in recycled and recycled retired batteries. By alkali - compounding to form a eutectic compound. Impurity elements that are conventionally difficult to completely remove in retired graphite are thoroughly removed at low temperature. The graphite after impurity removal and regeneration meets the physical and chemical properties of battery - grade graphite and has good electrochemical properties. This process is lengthy and requires the use of multiple chemicals.

[0007] WO2021252433 A9 discloses a method for recovering anode materials from a mixed recycle stream of spent lithium-ion batteries. Strong acid is added to the precipitate to remove residual cathode and separator materials. The strong acid removes residual alumina in the separator by converting it to aluminum sulfate. Washing the acid-treated precipitate removes water-soluble contaminants (such as aluminum sulfate obtained from alumina and sulfuric acid) to produce substantially pure graphite. This method is lengthy, expensive, and difficult to commercialize due to corrosion.

[0008] Hien Tran et al. (World Journal of Research and Review (WJRR) ISSN: 2455 - 3956, Vol. 5, No. 1, July 2017, pp. 23 - 26) disclosed a technique in 2017 for increasing the purity of graphite carbon from 92.6% to 98%. The effects of factors such as leaching agent, sulfuric acid concentration, temperature, time, and liquid-solid ratio on the process were studied. The results showed that the graphite content could be increased from 92.6% to 98%, meeting the requirements of high-purity graphite. However, the calcination was carried out with alkali.

[0009] Yatim LailumNi'mah et al. (Ni’mah&al. / Mor.J.Chem. 10 No 3) proposed a method in 2022 for separating graphite mechanically to remove plastic components. The obtained graphite was washed with dimethyl carbonate (DMC) and N-methyl-20 pyrrolidone (NMP) and leached in H 2 SO 4 The obtained residue was heated in an N 2 atmosphere in a furnace at 500 °C for 1 hour. FTIR and XRD characterizations were carried out to compare the anode materials obtained only through the leaching process and through mechanical treatment.

[0010] Yue Yang et al. (Waste Management 85 (2019) 529 - 537) disclosed the recovery of lithium and graphite from spent lithium-ion batteries in 2019. First, waste graphite was collected through two-stage calcination, with the optimal conditions being 1.5M hydrochloric acid, 60 minutes, and a solid-liquid ratio (S / L) of 100 g L -1 . The collected graphite was subjected to a simple acid leaching, enabling almost 100% of lithium, copper, and aluminum to enter the leaching solution. 99.9% of aluminum and 99.9% of copper were removed from the leaching solution by adjusting the pH, and then lithium was recovered by adding sodium carbonate to the leaching solution to form high-purity (>99%) lithium carbonate. The regenerated graphite was found to have a capacity of 37.2 mA.g -1 (591 mAh.g -1 ), 74.4 mA.g -1 (510 mAh.g -1) and 186 mA·g -1 (335 mAh·g -1 ) has a high initial specific capacity at a rate of, and has a high retention rate of 97.9% after 100 cycles. The method includes double calcination, followed by treatment with HCl and H 2 O 2 .

[0011] Yang Gao et al. (ACS Sustainable Chem. Eng., DOI: 10.1021 / acssuschemeng.0c02321) disclosed a new method for regenerating waste graphite through a combined sulfuric acid curing, leaching, and calcination process in 2021. Sulfuric acid curing-acid leaching experiments were carried out to study the effects of various operating conditions on aluminum removal. The purity of the regenerated graphite reached 99.6%, and it showed good electrochemical performance in terms of charge capacity and cycling. The regenerated graphite was obtained after calcination at 1500 °C, and its morphology and structure were characterized by XRD, Raman spectroscopy, and SAEM analysis. The treatment time was 24 hours.

[0012] In the past few years, more and more research has focused on the recycling of waste graphite, but few have summarized the challenges it faces. The reported existing technologies have problems such as long processes, high temperatures, the use of multiple chemicals, and environmental issues.

[0013] Therefore, a method is needed to solve the problems of the existing technologies and provide a clean, green, environmentally friendly, and commercially viable method. The method disclosed in the present invention is specifically for the removal of high-purity graphite. This method is very useful because it reduces the long process and is commercially viable.

[0014] Objectives of the present invention

[0015] The main objective of the present invention is to provide a method for recovering pure graphite from the leaching residue of waste lithium-ion batteries.

[0016] Another objective of the present invention is to provide a method for recovering pure graphite with a purity of 99.9%, which increases the value of the product.

[0017] Another objective of the present invention is to provide a method that takes less time.

[0018] Another objective of the present invention is to provide a commercially viable and economically attractive method.

[0019] Another objective of the present invention is to provide a simple, clean, green, and environmentally friendly method. Summary of the invention

[0020] The present invention relates to a method for recovering graphite from the leaching residue of waste lithium-ion batteries. The present invention provides an environmentally friendly and commercially viable method for recovering high-purity graphite.

[0021] In one embodiment, the present invention provides a method for recovering graphite from waste lithium-ion batteries, the method comprising the steps of: leaching the black material of the waste lithium-ion batteries to obtain a leaching residue, mixing the leaching residue of the waste lithium-ion batteries with a suitable solvent and water, maintaining the mixture at a predetermined temperature for a predetermined time to obtain a pugged residue. Cooling the pugged residue at room temperature. Stirring the obtained residue with a suitable reagent at a predetermined solid-liquid ratio for a predetermined time to obtain a slurry. Filtering, washing and drying the obtained slurry to obtain pure graphite.

[0022] The method for obtaining pure graphite with a purity of 99.9% is simple and feasible, and increases the value of the product. The method is clean, green, environmentally friendly, commercially viable and economically attractive.

[0023] The above objects and advantages of the present invention will become apparent from the following description of the drawings, detailed description and appended claims. Description of the Drawings

[0024] The method for recovering graphite from the leaching residue of waste lithium-ion batteries according to the present invention can be understood by referring to the following drawings:

[0025] Figure 1 FIG. is a process flow diagram for obtaining pure graphite from the leaching residue of waste lithium-ion batteries according to an embodiment of the present invention. Detailed Description

[0026] The present invention will now be described hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. On the contrary, the embodiments are provided to make the present disclosure more thorough and to fully convey the scope of the present invention to those skilled in the art.

[0027] The present invention will now be described hereinafter with reference to the detailed description, in which some but not all embodiments of the present invention are shown. In fact, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present disclosure meet the applicable legal requirements. The same numerals always refer to the same elements. The present invention is fully described herein with non-limiting embodiments and exemplary experiments.

[0028] The present invention relates to a method for recovering graphite from the leaching residue of waste lithium-ion batteries. The present invention provides an environmentally friendly and commercially viable method for recovering high-purity graphite.

[0029] In a preferred embodiment, the present invention provides a method for recovering pure graphite from waste lithium-ion batteries, comprising the following steps: (a) leaching the black material of the waste lithium-ion batteries to obtain a leaching residue; (b) mixing the leaching residue of the waste lithium-ion batteries obtained in step (a) with a suitable solvent and 20% to 30% water to obtain a mixture; (c) maintaining the mixture obtained in step (b) at a predetermined temperature for a predetermined time to obtain a treated residue; (d) cooling the treated residue obtained in step (c) at room temperature; (e) stirring the cooled residue obtained in step (d) with a suitable reagent at a predetermined solid-liquid ratio for a predetermined time to obtain a slurry; and (f) filtering the slurry obtained in step (e) to obtain a residue, and then washing and drying the residue with water to obtain pure graphite.

[0030] Wherein, the leaching residue of step (a) is obtained by leaching the black material of the waste lithium-ion batteries on operating equipment. The suitable solvent in step (b) is 15% to 20% sulfuric acid (98% (weight / weight)), the predetermined temperature in step (c) is 200 °C to 300 °C, and the predetermined time in step (c) is 2 hours to 4 hours.

[0031] In addition, the suitable reagent in step (e) is 10% to 20% (volume / volume) sulfuric acid, the predetermined time in step (e) is 2 hours to 4 hours. The solid-liquid ratio in step (e) is 1:2.

[0032] The method for obtaining pure graphite with a purity of 99.9% to 99.95% is simple and feasible, adding value to the product. The method is clean, green, environmentally friendly and commercially viable, and is economically attractive.

[0033] Figure 1 The process flow for obtaining pure graphite from the leaching residue of waste lithium-ion batteries is shown. The method is simple and feasible, and helps to recover 99.9% pure graphite.

[0034] The present invention will now be illustrated by the following non-limiting examples.

[0035] Example 1

[0036] Batch analysis

[0037] Batch 1:

[0038] Take 10 kg of the leaching residue of waste lithium-ion batteries from the factory, and mix it with 150 mL of sulfuric acid and 200 mL of water. Then keep the mixture in a muffle furnace at 200 °C for 3 hours, and then let it cool outside. Put the treated material into a plastic container filled with 20 liters of water, and add 2 liters of sulfuric acid with stirring. Stirring continues for 3 hours, filter the slurry, wash the final residue with 13 liters of water and dry it. The analysis of the dried residue - 2 (pure graphite - 9.95 kg), the factory leaching residue and the filtrate (30 L) is shown in the following table.

[0039] Table 1. Analysis of the leaching residue

[0040] Element Fe Cu Ni Co Mn Li Al ％ 0.57 1.27 0.36 0.44 0.04 0.15 0.33

[0041] Table 2. Analysis of the filtrate

[0042] Element Fe Cu Ni Co Mn Li Al g / L 1.9 4.1 1.1 1.45 0.13 0.5 1.1

[0043] Table 3. Analysis of the purified graphite (99.95%)

[0044] Element Fe Cu Ni Co Mn Li Al ％ 0.001 0.05 0.001 0.001 0.001 0.001 0.001

[0045] Batch 2:

[0046] Take 10 kg of the leaching residue of waste lithium-ion batteries from the factory, and mix it with 150 mL of sulfuric acid and 200 mL of water. Keep the residue in a muffle furnace at 200 °C for 3 hours, and then let it cool outside. Put the treated material into a plastic container filled with 20 liters of water, and add 1 liter of sulfuric acid with stirring. Stirring continues for 3 hours, filter the slurry, wash the final residue with 13 liters of water and dry it. The analysis of the dried residue - 2 (pure graphite - 9.96 kg), the factory leaching residue and the filtrate (30 L) is shown in the following table.

[0047] Table 1. Analysis of the leaching residue

[0048] Element Fe Cu Ni Co Mn Li Al ％ 0.57 1.27 0.36 0.44 0.04 0.15 0.33

[0049] Table 2. Analysis of the filtrate

[0050] Element Fe Cu Ni Co Mn Li Al g / L 1.95 4.15 1.1 1.45 0.14 0.5 1.2

[0051] Table 3. Analysis of the purified graphite (99.96%)

[0052] Element Fe Cu Ni Co Mn Li Al ％ 0.001 0.04 0.001 0.001 0.001 0.001 0.001

[0053] The purity of the graphite obtained from the leaching residue of waste lithium-ion batteries is 99.9%.

[0054] Therefore, the present invention provides a simple, clean, easy-to-implement, environmentally friendly and commercially viable method for obtaining pure graphite from waste lithium-ion batteries. The method of obtaining graphite with a purity of 99.9% increases the value of the product.

[0055] Benefiting from the teachings given in the foregoing description and the related drawings, those skilled in the art to which the present invention pertains will readily conceive of various modifications and other embodiments of the present invention described herein. Accordingly, it is to be understood that the present invention is not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method for recovering graphite from waste lithium-ion batteries, characterized in that, the method comprises the following steps: (a) Leaching the black matter of waste lithium-ion batteries to obtain a leaching residue; (b) Mixing the leaching residue of the waste lithium-ion batteries obtained in step (a) with a suitable solvent and 20% to 30% water to obtain a mixture; (c) Maintaining the mixture obtained in step (b) at a predetermined temperature for a predetermined time to obtain a treated residue; (d) Cooling the treated residue obtained in step (c) at room temperature; (e) Stirring the cooled residue obtained in step (d) with a suitable reagent at a predetermined solid-liquid ratio for a predetermined time to obtain a slurry; and (f) Filtering the slurry obtained in step (e) to obtain a residue, and then washing and drying the residue with water to obtain pure graphite.

2. A method for recovering graphite from waste lithium-ion batteries, wherein, the leaching residue of step (a) is obtained by leaching the black matter of the waste lithium-ion batteries on operating equipment.

3. A method for recovering graphite from waste lithium-ion batteries, wherein, the suitable solvent in step (b) is 15% to 20% sulfuric acid (98% (weight / weight)).

4. A method for recovering graphite from waste lithium-ion batteries, wherein, the predetermined temperature in step (c) is 200°C to 300°C, and the predetermined time in step (c) is 2 hours to 4 hours.

5. A method for recovering graphite from waste lithium-ion batteries, wherein, the suitable reagent in step (e) is 10% to 20% (volume / volume) sulfuric acid, and the predetermined time in step (e) is 2 hours to 4 hours.

6. A method for recovering graphite from waste lithium-ion batteries, wherein, the predetermined solid-liquid ratio in step (e) is 1:

2.

7. A method for recovering graphite from waste lithium-ion batteries, characterized in that, the purity of the graphite obtained in step (f) is 99.9% to 99.95%.

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