Deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride and its use

Abstract

This invention discloses a deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride and its application, belonging to the field of resource recycling technology for waste lithium-ion batteries. It solves the technical problems of poor environmental friendliness, low selectivity, and high energy consumption in the traditional strong acid leaching method for recycling waste lithium-ion battery cathode materials. The technical solution is as follows: the deep eutectic solvent is composed of p-hydroxybenzenesulfonic acid as a hydrogen bond donor and choline chloride as a hydrogen bond acceptor. The beneficial effects of this invention are: the deep eutectic solvent is liquid at room temperature and exhibits excellent metal leaching rates at mild leaching temperatures and in a short time when used for recycling waste lithium-ion battery cathode materials; the preparation method of this deep eutectic solvent has a simple process flow, which is conducive to promoting the large-scale recycling of waste lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery recycling technology, specifically relating to a deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride and its application. Background Technology

[0002] Against the backdrop of the accelerated global energy structure transformation from fossil fuels to new energy sources, lithium-ion batteries (LIBs) have become a core supporting technology for new energy vehicles and energy storage systems (Nature, 2008, 451: 652–657). Due to their high energy density and long cycle life, lithium-ion batteries are widely used in electric vehicles, consumer electronics, energy storage systems, and medical devices (Joule, 2019, 3: 2622–2646). With the rapid development of the global energy storage market, the amount of discarded energy storage batteries is also gradually increasing. The reserves of key metals such as cobalt and lithium are limited, and the energy industry's demand for them is constantly increasing. Efficiently recycling waste lithium cobalt oxide cathode materials can alleviate the demand for cobalt imports, thereby reducing the supply risk of cobalt resources (ACS Sustainable Chemistry & Engineering, 2020, 8(14): 5437–5445).

[0003] Hydrometallurgy and pyrometallurgy are the mainstream methods for treating waste lithium-ion batteries. Although these methods are relatively mature in industrial practice, they are accompanied by problems such as environmental pollution and high energy consumption (RSC Sustainability, 2023, 1: 270–278), making it difficult to fully meet the requirements of green recycling and sustainable development. Therefore, developing new recycling systems with milder conditions and lower environmental burden has become an important research direction in this field.

[0004] Deep eutectic solvents, a novel solvent system formed by hydrogen bond donors (HBDs) and acceptors (HBAs) through intermolecular interactions, possess advantages such as tunable composition, simple preparation process, and strong solubility for metal oxides, enabling efficient leaching under mild conditions. By adjusting the types and molar ratios of HBAs–HBDs, the solvent's acidity, reducing properties, and viscosity can be synergistically controlled to a certain extent, thereby achieving selective leaching and subsequent separation of lithium and cobalt. This process provides an efficient, environmentally friendly, and economical solution for recovering lithium and cobalt from waste lithium-ion batteries.

[0005] Therefore, developing a novel deep eutectic solvent system with higher leaching efficiency, milder reaction conditions, and better environmental friendliness is of great significance for promoting the green and efficient recycling of waste lithium-ion batteries. Summary of the Invention

[0006] To address the technical problems of insufficient leaching efficiency and high reaction temperature in existing lithium-ion battery recycling systems for waste cathode materials, the present invention aims to provide a deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride. The deep eutectic solvent is liquid at room temperature and has low volatility. Another objective of the present invention is that the above-mentioned deep eutectic solvent has a good metal ion leaching rate when used to recycle waste cathode materials under mild conditions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride, wherein the deep eutectic solvent is composed of p-hydroxybenzenesulfonic acid as a hydrogen bond donor and choline chloride as a hydrogen bond acceptor.

[0008] Furthermore, the molar ratio of p-hydroxybenzenesulfonic acid to choline chloride is 0.5:1 to 2:1.

[0009] Furthermore, the molar ratio of p-hydroxybenzenesulfonic acid to choline chloride is 0.5:1.

[0010] A method for preparing a deep eutectic solvent as described above includes the following steps: mixing p-hydroxybenzenesulfonic acid and choline chloride at a molar ratio of 0.5 to 2:1, and stirring at 25°C to 100°C until a homogeneous and transparent liquid is formed.

[0011] A method for leaching valuable metals from waste lithium-ion battery cathode materials includes the following steps: taking commercial lithium-ion battery cathode powder, adding it to the above-mentioned deep eutectic solvent and mixing to form a leaching system; stirring the leaching system under heating conditions for leaching reaction; after the reaction is completed, performing solid-liquid separation to obtain a leachate containing valuable metal ions.

[0012] Furthermore, the leaching reaction temperature is from 25°C to 100°C; the reaction time is from 0.5 hours to 24 hours.

[0013] Furthermore, the solid-liquid ratio of the cathode material powder to the deep eutectic solvent is 20~60 mg / g.

[0014] Furthermore, the solid-liquid ratio is 30 mg / g.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) This invention uses p-hydroxybenzenesulfonic acid as a hydrogen bond donor. Its sulfonic acid group (-SO3H) has strong proton acidity, which can effectively break the metal-oxygen bond (such as Co-O) in the cathode material, and can significantly improve the leaching rate of valuable metals. In addition, this method can be prepared by simple heating and mixing. The raw materials are readily available and the cost is low, making it suitable for large-scale industrial application and conducive to promoting the recycling of waste lithium-ion batteries. Experiments show that under the conditions of 30 mg / g, 80°C, and stirring for 6 h, the leaching rates of lithium and cobalt can reach more than 97.98% and 95.40%, respectively.

[0017] (2) The leaching of cathode materials by the deep eutectic solvent provided by this invention can be completed under medium and low temperature conditions of atmospheric pressure and 25-100℃, without the need for high temperature and high pressure equipment, resulting in low energy consumption and high process safety. Compared with inorganic strong acids, p-hydroxybenzenesulfonic acid and choline chloride are both low-volatility and low-toxicity compounds. The prepared deep eutectic solvent is biodegradable, and no harmful gases are generated during the leaching process. The waste liquid is easy to treat, making it a truly green leaching technology. Attached Figure Description

[0018] Figure 1 Optical photographs of the deep eutectic solvents of Examples 1, 3, 4 and Comparative Example 1 at 25 °C, (a) is Comparative Example 1, (b) is Examples 1, 3, and 4;

[0019] Figure 2 FTIR spectrum of the deep eutectic solvent prepared in Example 1;

[0020] Figure 3 H is the deep eutectic solvent prepared in Example 1 1 NMR spectrum;

[0021] Figure 4 This is a bar chart showing the effect of the deep eutectic solvent of the present invention on the leaching rate of cobalt and lithium in lithium cobalt oxide cathode material at different molar ratios.

[0022] Figure 5 This is a bar chart showing the effect of the deep eutectic solvent of the present invention on the leaching rate of cobalt and lithium in lithium cobalt oxide cathode material at different reaction temperatures.

[0023] Figure 6 This is a bar chart showing the effect of the deep eutectic solvent of the present invention on the leaching rate of cobalt and lithium in lithium cobalt oxide cathode material under different solid-liquid ratios.

[0024] Figure 7 This is a bar chart showing the effect of the deep eutectic solvent of the present invention on the leaching rate of cobalt and lithium in lithium cobalt oxide cathode material under different stirring times.

[0025] Figure 8Scanning electron microscope (SEM) images of waste lithium cobalt oxide cathode material leached at 80 °C for (a) 0 h, (b) 0.25 h, (c) 0.5 h, and (d) 1 h using the deep eutectic solvent prepared in Example 1. Detailed Implementation

[0026] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0027] Example 1

[0028] The deep eutectic solvent in this embodiment is composed of p-hydroxybenzenesulfonic acid and choline chloride in a molar ratio of 0.5:1, and is obtained by the following steps: 3.908g of p-hydroxybenzenesulfonic acid and 6.092g of choline chloride are mixed together and stirred at 80°C for 0.5h to obtain a colorless and transparent homogeneous solution, which is then cooled to room temperature for later use.

[0029] The leaching method for valuable metals in the cathode material of waste lithium-ion batteries in this embodiment includes the following steps: taking 30mg of lithium cobalt oxide cathode powder ( Add 1g of the deep eutectic solvent prepared in Example 1 (molar ratio 0.5:1) to a solid-liquid ratio of 30mg / g. Place the mixture in a metal bath at 80℃ and stir magnetically for 6 hours. After the reaction is complete, centrifuge, take the supernatant, digest and dilute it, and then determine the concentrations of cobalt and lithium by ICP-OES to calculate the leaching rate.

[0030] Example 2

[0031] The deep eutectic solvent in this embodiment is composed of p-hydroxybenzenesulfonic acid and choline chloride in a molar ratio of 0.5:1, and is obtained by the following steps: 3.908g of p-hydroxybenzenesulfonic acid and 6.092g of choline chloride are mixed together and stirred at 80°C for 0.5h to obtain a colorless and transparent homogeneous solution, which is then cooled to room temperature for later use.

[0032] The leaching method for valuable metals in the cathode material of waste lithium-ion batteries in this embodiment includes the following steps: taking 30mg of lithium cobalt oxide cathode powder ( Add 1g of the deep eutectic solvent prepared in Example 1 (molar ratio 0.5:1) to a solid-liquid ratio of 40mg / g. Place the mixture in a metal bath at 80℃ and stir magnetically for 24 hours. After the reaction is complete, centrifuge, take the supernatant, digest and dilute it, and then determine the concentrations of cobalt and lithium by ICP-OES to calculate the leaching rate.

[0033] Example 3

[0034] The deep eutectic solvent of this embodiment is composed of p-hydroxybenzenesulfonic acid and choline chloride in a molar ratio of 1:1, and is obtained by the following steps: 3.48g of p-hydroxybenzenesulfonic acid and 2.80g of choline chloride are weighed, and the same preparation method as in Example 2 is used to obtain a deep eutectic solvent in a molar ratio of 1:1.

[0035] The leaching method for valuable metals in the cathode material of waste lithium-ion batteries in this embodiment includes the following steps: except for using the deep eutectic solvent (molar ratio 1:1) prepared in this embodiment, the other conditions are the same as the leaching method in Example 2.

[0036] Example 4

[0037] The deep eutectic solvent of this embodiment is composed of p-hydroxybenzenesulfonic acid and choline chloride in a molar ratio of 2:1, and is obtained by the following steps: 3.48g of p-hydroxybenzenesulfonic acid and 1.40g of choline chloride are weighed, and the same preparation method as in Example 2 is used to obtain a deep eutectic solvent in a molar ratio of 2:1.

[0038] The leaching method for valuable metals in the cathode material of waste lithium-ion batteries in this embodiment includes the following steps: except for using the deep eutectic solvent (molar ratio 2:1) prepared in this embodiment, the other conditions are the same as the leaching method in Example 2.

[0039] Comparative experiment:

[0040] The deep eutectic solvent used in this comparative experiment consisted of p-toluenesulfonic acid and choline chloride in a molar ratio of 0.5:1, and was obtained by the following steps: 2.792 g of choline chloride and 1.722 g of p-toluenesulfonic acid were weighed, and the same preparation method as in Example 1 was used to obtain the p-toluenesulfonic acid-choline chloride deep eutectic solvent (molar ratio 0.5:1).

[0041] The leaching method for valuable metals in the cathode material of waste lithium-ion batteries in this comparative example includes the following steps: taking 30 mg of lithium cobalt oxide cathode powder ( Add 1g of the p-toluenesulfonic acid-choline chloride deep eutectic solvent (molar ratio 0.5:1) prepared in this comparative example, with a solid-liquid ratio of 30mg / g. Place the mixture in a metal bath at 80℃ and stir magnetically for 6 hours. After the reaction is complete, centrifuge, take the supernatant, digest and dilute it, and then determine the concentrations of cobalt and lithium by ICP-OES to calculate the leaching rate.

[0042] Figure 1Optical photographs of the deep eutectic solvents prepared in Examples 1, 3, and 4 and Comparative Example 1 at 25 °C are shown. (a) is Comparative Example 1, and (b) is Examples 1, 3, and 4. It can be seen that Comparative Example 1 is solidified at room temperature, while the deep eutectic solvents prepared in Examples 1 to 3 exhibit good fluidity and uniformity, indicating that they maintain stable chemical and physical properties at room temperature. Figure 2 The FTIR spectrum of the deep eutectic solvent prepared in Example 1 is approximately 3400 cm⁻¹. -1 The presence of a broad peak (corresponding to the OH stretching vibration peak) and the redshift observed in DES indicate the formation of a hydrogen bond structure. Figure 3 The ¹H NMR spectrum of the deep eutectic solvent prepared in Example 1 shows that the characteristic peaks of the relevant hydrogens in p-hydroxybenzenesulfonic acid and choline chloride have undergone slight chemical shifts, proving that a hydrogen bond network has been formed between the two components.

[0043] Figure 4 The bar chart shows the effect of the deep eutectic solvent prepared in Examples 1, 3, and 4 on the leaching rate of cobalt and lithium in the lithium cobalt oxide cathode material. It can be seen that among Examples 1, 3, and 4, the optimal molar ratio of p-hydroxybenzenesulfonic acid to choline chloride in Example 1 is 0.5:1.

[0044] Using the deep eutectic solvent prepared in Example 2 (molar ratio 0.5:1), the solid-liquid ratio was determined to be 40 mg / g, the stirring time was 24 h, and the reaction temperatures were set at 25℃, 50℃, 65℃, 80℃, and 100℃, respectively. The results are as follows: Figure 5 As shown, the leaching rate gradually increases with increasing temperature; at temperatures above 80℃, the leaching rates of cobalt and lithium can reach 89.84% and 93.38% or higher, respectively, with the best results achieved at 100℃. Considering energy consumption, 80℃ is selected as the optimal temperature.

[0045] Using the deep eutectic solvent (molar ratio 0.5:1) prepared in Example 1, solid-liquid ratios of 20 mg / g, 30 mg / g, 40 mg / g, and 60 mg / g were set respectively. The results are as follows: Figure 6 As shown, the leaching effect is best when the solid-liquid ratio is 30 mg / g; if the solid-liquid ratio is too low, the system viscosity will be too high and affect mass transfer, and if the solid-liquid ratio is too high, the metal concentration will be too low and affect the economy.

[0046] Using the deep eutectic solvent prepared in Example 1 (molar ratio 0.5:1), the solid-liquid ratio was determined to be 30 mg / g, and the reaction stirring times were set to 0.5 h, 2 h, 4 h, and 6 h, respectively. The results are as follows: Figure 7 As shown, the leaching rate gradually increases with the extension of stirring time; after stirring for 6 hours, the leaching rates of cobalt and lithium can reach 97.98% and 95.40%, respectively.

[0047] To demonstrate that the deep eutectic solvent can effectively erode lithium cobalt oxide powder and improve the leaching efficiency of metal ions, the morphology of the surface of the lithium cobalt oxide cathode powder that did not fully react within 0.25 to 1 hour in Example 1 was observed using SEM. Figure 8 The images are scanning electron microscope (SEM) images of waste lithium cobalt oxide cathode material leached at 80 °C for (a) 0 h, (b) 0.25 h, (c) 0.5 h, and (d) 1 h using the deep eutectic solvent prepared in Example 1. As can be seen, the layered structure is gradually destroyed as the reaction proceeds, and metal ions dissolve from the solid phase into the DES liquid phase.

[0048] This method is simple to prepare, uses inexpensive and readily available raw materials, and is suitable for large-scale production, showing great application potential. The cobalt and lithium leaching efficiency was tested by adding lithium cobalt oxide powder to the deep eutectic solvents prepared in Examples 1-4 and Comparative Example 1. The results are listed in Table 1.

[0049] Table 1. Performance of cobalt and lithium leaching efficiency tests using deep eutectic solvents prepared in Examples 1-4 and Comparative Example 1.

[0050]

[0051] As can be seen from Table 1, the deep eutectic solvent prepared in Example 1 has good leaching efficiency under mild conditions and at a suitable time.

[0052] In summary, the deep eutectic solvent containing p-hydroxybenzenesulfonic acid and choline chloride of this invention can disrupt the cathode structure to a certain extent. Its acidity and reducing properties effectively reduce trivalent cobalt to divalent cobalt and efficiently leach lithium and cobalt ions. Using it for lithium-ion battery cathode recycling helps reduce energy consumption. Furthermore, this method has a simple process flow and can be extended to other cathode material systems, which is beneficial for large-scale production and application.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A deep eutectic solvent comprising p-hydroxybenzenesulfonic acid and choline chloride, characterized in that, The deep eutectic solvent consists of p-hydroxybenzenesulfonic acid as a hydrogen bond donor and choline chloride as a hydrogen bond acceptor.

2. The deep eutectic solvent according to claim 1, wherein The molar ratio of p-hydroxybenzenesulfonic acid to choline chloride is 0.5:1 to 2:

1.

3. The deep eutectic solvent according to claim 2, wherein The molar ratio of p-hydroxybenzenesulfonic acid to choline chloride is 0.5:

1.

4. A method for producing the deep eutectic solvent according to any one of claims 1 to 3, characterized by, The process includes the following steps: mixing p-hydroxybenzenesulfonic acid and choline chloride at a molar ratio of 0.5 to 2:1, and stirring at 25°C to 100°C until a homogeneous and transparent liquid is formed.

5. A method for leaching valuable metals from a spent lithium-ion battery cathode material, characterized by, The process includes the following steps: taking commercial lithium-ion battery cathode powder, adding it to the deep eutectic solvent described in any one of claims 1 to 3 and mixing them to form a leaching system; stirring the leaching system under heating conditions to carry out a leaching reaction; after the reaction is completed, performing solid-liquid separation to obtain a leachate containing valence metal ions.

6. The leaching process according to claim 5, characterized in that, The leaching reaction is carried out at a temperature of 25°C to 100°C for a reaction time of 0.5 hours to 24 hours.

7. The leaching method according to claim 5, characterized in that, The solid-liquid ratio of the cathode material powder to the deep eutectic solvent is 20~60 mg / g.

8. The leaching method according to claim 7, characterized in that, The solid-liquid ratio is 30 mg / g.

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