Method for recycling positive electrode material of light-driven lithium ion battery

Abstract

The invention discloses a light-driven lithium ion battery positive electrode material recovery method which comprises the following steps: constructing a water / oil two-phase light-driven recovery system, dispersing a photocatalyst in an upper-layer oil phase, and dispersing a lithium ion battery positive electrode material and acid in a lower-layer water phase; illumination is applied to the water / oil two-phase light-driven recovery system in an oxygen or air atmosphere to drive a catalytic reaction, metal ions are leached from the lithium ion battery positive electrode material, and then the metal ions are recovered by adopting a chemical precipitation method. The invention provides a green method for recycling a positive electrode material of a photocatalytic driven lithium ion battery. Efficient recycling of high-value metals such as lithium and cobalt is realized by coupling a photocatalytic-photothermal synergistic effect and regulating and controlling an oil-water interface. Compared with an existing recycling process, the recycling process has the advantages that an external heating device and a chemical reducing agent adding link are abandoned, and a green, low-energy-consumption and low-cost strategy is provided for recycling of the lithium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery recycling, and in particular to a method for recycling positive electrode materials of light-driven lithium ion batteries. Background Art

[0002] Lithium-ion batteries, with their excellent energy storage performance, are widely used in many fields, including new energy vehicles, smart grids, and portable electronic devices. However, the large amount of toxic electrolytes, heavy metals, and other pollutants generated during the large-scale production and disposal of lithium-ion batteries pose a major threat to the stability of ecosystems and human health and safety. At the same time, the unsustainable mining and disposal of high-value metals such as lithium, cobalt, and nickel not only causes serious environmental degradation but also leads to a huge waste of resources. Therefore, the recycling and reuse of key metals in lithium-ion batteries is of great significance both in terms of environmental protection and economic development.

[0003] At present, in the field of lithium-ion battery cathode material recycling, the main process is hydrometallurgical process. This process uses acid to provide protons and anions to achieve metal leaching, which has the advantages of mild reaction conditions and high metal recovery rate. Its reaction kinetics is similar to that of high-valent metals (such as Co 3+ ) is closely related to the reduction process of H2O2. In actual operation, it is usually necessary to strategically introduce H2O2 as a reducing agent to effectively accelerate the reaction process. However, this technical system still faces many severe challenges in practical application: First, H2O2 is mainly prepared by the anthraquinone method in industry. This method has the disadvantages of high energy consumption and high pollution, resulting in a significant increase in carbon emissions from the entire battery recycling industry chain; second, high-concentration H2O2 has the risk of combustion and explosion during storage and use, which greatly increases the difficulty of production safety management; third, H2O2 will decompose rapidly in a heated environment and the presence of transition metal ions, causing its effective concentration to decay rapidly. In order to maintain the reaction efficiency, it needs to be continuously replenished, which not only significantly increases the reagent cost, but also makes the process flow control extremely complicated due to frequent operations. In addition, the existing technology also requires continuous heating to improve the reaction kinetics, which further aggravates energy loss and increases production costs.

[0004] In summary, developing a sustainable lithium-ion battery cathode material recycling strategy that combines high efficiency and energy-saving characteristics with industrial application potential has become a key technical issue that needs to be urgently addressed in this field. Summary of the invention

[0005] To solve the above technical problems, the present invention provides a light-driven lithium-ion battery cathode material recycling method, which has the advantages of being green and low in energy consumption, and can achieve efficient extraction and recovery of high-value metal elements in the cathode material.

[0006] The present invention is achieved through the following technical solutions: A method for recycling the cathode material of a photo-driven lithium-ion battery, comprising the following steps: constructing a water / oil two-phase photo-driven recycling system, dispersing a photocatalyst in the upper oil phase, and dispersing the cathode material of the lithium-ion battery and an acid in the lower water phase; applying light to the water / oil two-phase photo-driven recycling system in an oxygen or air atmosphere to drive a catalytic reaction, leaching metal ions from the cathode material of the lithium-ion battery, and then recovering the metal ions by a chemical precipitation method.

[0007] In the method for recycling the cathode material of a photo-driven lithium-ion battery provided by the present invention, the photocatalyst dispersed in the oil phase generates hydrogen peroxide (H2O2) under light irradiation and diffuses into the water phase. With the assistance of the photo-induced thermal effect, the reduction of high-valent metals in the cathode material of the lithium-ion battery is promoted, such as the reduction of high-valent Co in LiCoO2 3+ ions to Co 2+ ions, and then the lattice of the electrode material is destroyed and dissolved in an acidic environment to achieve the leaching of Li + and Co 2+ leaching.

[0008] The present invention proposes a green method for recycling the cathode material of a photo-driven lithium-ion battery, which realizes the efficient recovery of high-value metals such as lithium and cobalt by coupling the photo-catalytic-photo-thermal synergistic effect and the regulation of the oil-water interface. This method uses light energy as the only energy input source, and the photocatalyst in-situ converts oxygen into hydrogen peroxide under light irradiation, synchronously realizing the self-supply of the reducing agent and the self-heating of the reaction system, thereby achieving the efficient leaching of metal ions. Compared with the existing recycling process, the present invention abandons the external heating device and the addition link of the chemical reducing agent, provides a green, low-energy-consuming and low-cost strategy for the recycling of lithium-ion batteries, realizes the maximization of the photo-catalytic efficiency, and can meet the needs of continuous production.

[0009] Further, to ensure the reaction efficiency and stability of the overall system, the photocatalyst should be selected from an organic semiconductor material with hydrophobicity and thermal / acid stability. Considering that the rigid conjugated skeleton can enhance the light absorption ability, the photocatalyst is selected from one or more of the following T1-T3 structures: 、 、 。

[0010] Further, the photocatalyst is obtained by reacting an aldehyde monomer and an amine monomer in an organic solvent at 80-150 °C; The aldehyde monomer is 2,3,6,7,10,11 - hexakis(4 - formylphenyl)triphenylene, and the amine monomer is 2,5 - diamino - 1,4 - benzenedithiophene dihydrochloride, 2,5 - diamino - 1,4 - dihydroxybenzene dihydrochloride, or 1,2,4,5 - benzenetetramine tetrahydrochloride.

[0011] Further, the structural formula of 2,3,6,7,10,11 - hexakis(4 - formylphenyl)triphenylene is , and the structural formula of 2,5 - diamino - 1,4 - benzenedithiophene dihydrochloride is , the structural formula of 2,5 - diamino - 1,4 - dihydroxybenzene dihydrochloride is , and the structural formula of 1,2,4,5 - benzenetetramine tetrahydrochloride is .

[0012] Specifically, under the condition of oxygen (or air), the aldehyde group and the amine group first undergo a Schiff - base condensation reaction to produce an imine bond. Subsequently, under the oxidation of molecular oxygen, a dehydrogenative cyclization reaction occurs between the imine and the thiol group (for synthesizing T1) or the hydroxyl group (for synthesizing T2) or the amino group (for synthesizing T3), and finally a stable benzobisoxazole linking unit is formed. The prepared photocatalyst has a fully conjugated backbone structure and excellent chemical stability.

[0013] Further, the organic solvent is N,N - dimethylformamide (DMF).

[0014] Further, the concentration of the aldehyde monomer in the organic solvent is 1.5 - 2 mM, preferably 1.8 M.

[0015] Further, the concentration of the amine monomer in the organic solvent is 5 - 6 mM, preferably 5.6 M.

[0016] Preferably, the photocatalyst is a compound containing a thiazole ring and a triphenylene unit, and the structural formula is: .

[0017] Further, the concentration of the photocatalyst in the oil phase is 0.1 - 100 g / L, preferably 0.5 - 30 g / L, and more preferably 1 - 3 g / L.

[0018] Further, the oil phase is a water - insoluble alcohol solvent with a density less than that of water and a boiling point greater than 100 °C.

[0019] Further, the oil phase is selected from one or more of n - pentanol, iso - pentanol, n - hexanol, iso - hexanol, 2 - ethylhexanol, n - octanol, iso - octanol, n - decanol, and iso - decanol.

[0020] Preferably, considering the comprehensive factors of low viscosity, high hole consumption rate and procurement cost, n-octanol is selected as the oil phase.

[0021] Further, the positive electrode material of the lithium ion battery is selected from one or more of LiCoO2, LiFePO4, LiCo x Ni y Mn 1-x-y O2, LiMn2O4, LiNiCoAlO2, LiV2O4, Li2FeTiO4; wherein, 0 < x, 0 < y, and x + y < 1.

[0022] Further, the concentration of the positive electrode material of the lithium ion battery in the aqueous phase is 0.1-100 g / L, preferably 0.5-30 g / L, and more preferably 1-10 g / L.

[0023] Further, the acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, formic acid, acetic acid, citric acid, maleic acid, malic acid and ascorbic acid.

[0024] Preferably, considering factors such as cost and efficiency, acetic acid is selected as the acid.

[0025] Further, the concentration of the acid in the aqueous phase is 0.05-5 M, preferably 0.05-2 M, and more preferably 0.2-1.0 M.

[0026] Further, the volume ratio of the oil phase to the aqueous phase is (0.1-10):1, preferably 1:3-3:1.

[0027] Further, sunlight or an artificial light source is used to apply light, and a Fresnel lens can also be used to increase the light intensity and thermal effect.

[0028] Further, the artificial light source is a xenon lamp or an LED.

[0029] Further, the intensity of the light is 50-600 mW·cm -2 2, preferably 200-600 mW·cm -2 .

[0030] Further, the temperature of the water / oil two-phase light-driven recovery system is 60-90 °C, preferably 80 °C.

[0031] The beneficial effects of the present invention are: 1. The method for recycling the cathode material of a photo-driven lithium-ion battery provided by the present invention does not require external addition of H2O2. It continuously supplies H2O2 in situ through photochemistry at normal temperature and pressure, accelerating the reduction of metal ions, avoiding the defect of continuously replenishing reducing agents in the existing methods, eliminating the need for manual monitoring and replenishment of reducing agents, saving the procurement, transportation and storage costs of reducing agents, and reducing the frequency of manual intervention; the dynamic mass transfer process effectively alleviates the problem of catalyst degradation caused by the accumulation of H2O2 concentration, maintaining the stability of the photocatalyst and the continuous operation of the system; the generation of H2O2 and the leaching of metal ions in the water / oil two-phase photo-driven recycling system are continuously carried out in the same reactor, reducing the number of equipment used; the energy input of the water / oil two-phase photo-driven recycling system completely depends on light energy, only using the photothermal effect to provide heat for heating, without relying on the heating device in the traditional system, further reducing energy consumption and costs.

[0032] 2. The physical phase separation strategy in the method for recycling the cathode material of a photo-driven lithium-ion battery provided by the present invention successfully blocks the competitive absorption of incident light by the dark cathode material, ensuring the light energy capture efficiency of the photocatalyst; the photocatalysis and chemical acid etching processes are independently carried out in immiscible two-phase systems respectively, so as to realize the continuous collection of the lower-layer metal ion solution and facilitate the dynamic replenishment of acid solution; the mass transfer barrier formed at the two-phase interface can effectively prevent the pollution of the photocatalyst by the leached metal ions, ensuring the stability of the photocatalytic performance. Brief Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the reaction system for recycling the cathode material of a photo-driven lithium-ion battery provided by the present invention.

[0034] Figure 2 It is an infrared structure characterization spectrum of the photocatalyst shown by the T1-T3 structure.

[0035] Figure 3 It is the solid 13 13C nuclear magnetic spectrum of the photocatalyst shown by the T1-T3 structure.

[0036] Figure 4 It is a morphology characterization diagram of the photocatalyst shown by the T1-T3 structure; among them, a is a scanning electron microscope (SEM) image of the photocatalyst shown by the T1 structure, b is an SEM image of the photocatalyst shown by the T2 structure, c is an SEM image of the photocatalyst shown by the T3 structure, d is a transmission electron microscope (TEM) image of the photocatalyst shown by the T1 structure, e is a TEM image of the photocatalyst shown by the T2 structure, and f is a TEM image of the photocatalyst shown by the T3 structure.

[0037] Figure 5 For the recycling of Li in the cathode material of a photo-driven lithium-ion battery in Example 1 + and Co2+ Detection result diagram; among them, the left diagram shows the Li + and Co 2+ amount of substance dissolved from LiCoO2 by unit mass of photocatalyst over time; the right diagram shows the Li + and Co 2+ dissolution efficiency data diagram after 4 hours of light irradiation.

[0038] Figure 6 For Examples 1 - 3 of the photocatalytic lithium-ion battery cathode material for recycling Li + and Co 2+ amount of substance of Li + and Co 2+ dissolved from LiCoO2 by unit mass of photocatalyst after 4 hours of light irradiation, comparison diagram.

[0039] Figure 7 For Example 4 of the photocatalytic lithium-ion battery cathode material for recycling Li + and Co 2+ Detection result diagram; among them, the left diagram shows the Li + and Co 2+ amount of substance dissolved from LiCoO2 by unit mass of photocatalyst over time; the right diagram shows the Li + and Co 2+ dissolution efficiency data diagram after 4 hours of light irradiation.

[0040] Figure 8 For Examples 1 and 5 - 8 of the photocatalytic lithium-ion battery cathode material for recycling Li + and Co 2+ amount of substance of Li + and Co 2+ dissolved from LiCoO2 by unit mass of photocatalyst after 4 hours of light irradiation, comparison diagram.

[0041] Figure 9 For Examples 1 and 9 - 13 of the photocatalytic lithium-ion battery cathode material for recycling Li + and Co 2+ amount of substance of Li + and Co 2+ dissolved from LiCoO2 by unit mass of photocatalyst after 4 hours of light irradiation, comparison diagram.

[0042] Figure 10 For Example 14 of the photocatalytic lithium-ion battery cathode material for recycling Li + amount of substance of Li + dissolved from LiFePO4 by unit mass of photocatalyst over time and the corresponding Li + dissolution efficiency data diagram.

[0043] Figure 11 Detection result graph for the recovery of Li + , Co 2+ , Ni 2+ and Mn 2+ in the positive electrode material of the photocatalytic lithium-ion battery in Example 15; among them, the left graph is the graph of the change trend of the amount of substance of Li 1 / 3 , Ni 1 / 3 , Mn 1 / 3 dissolved from LiCo + , Co 2+ , Ni 2+ and Mn 2+ per unit mass of photocatalyst over time; the right graph is the graph of the dissolution efficiency data of Li + , Co 2+ , Ni 2+ and Mn 2+ after 4 hours of light irradiation.

[0044] Figure 12 Detection result graph for the recovery of Li + and Co 2+ in the positive electrode material of the photocatalytic lithium-ion battery in Example 16; among them, the left graph is the graph of the change trend of the amount of substance of Li + and Co 2+ dissolved from LiCoO2 per unit mass of photocatalyst over time; the right graph is the graph of the dissolution efficiency data of Li + and Co 2+ after 4 hours of light irradiation.

[0045] Figure 13 Comparison graph of the amount of substance of Li + and Co 2+ dissolved from LiCoO2 per unit mass of photocatalyst after 4 hours of light irradiation in Example 1 and Examples 17 - 18 for the recovery of Li + and Co 2+ in the positive electrode material of the photocatalytic lithium-ion battery.

[0046] Figure 14 Detection result graph for the recovery of Li + and Co 2+ in the positive electrode material of the photocatalytic lithium-ion battery in Comparative Example 1; among them, the left graph is the graph of the change trend of the amount of substance of Li + and Co 2+ dissolved from LiCoO2 per unit mass of photocatalyst over time; the right graph is the graph of the dissolution efficiency data of Li + and Co 2+ after 4 hours of light irradiation.

[0047] Figure 15 Detection result graph for the recovery of Li + and Co2+ Detection result diagram; among them, the left diagram shows the Li + and Co 2+ amount of substance dissolved from LiCoO2 by unit mass of photocatalyst over time; the right diagram is the data diagram of the dissolution efficiency of Li + and Co 2+ after 4 hours of light irradiation.

[0048] Figure 16 For Comparative Example 3, it is the detection result diagram of the recovery of Li + and Co 2+ from the cathode material of a photo-driven lithium-ion battery; among them, the left diagram shows the Li + and Co 2+ amount of substance dissolved from LiCoO2 by unit mass of photocatalyst over time; the right diagram is the data diagram of the dissolution efficiency of Li + and Co 2+ after 4 hours of light irradiation.

[0049] Figure 17 It is the experimental result diagram of the cycle stability test of Test Example 1.

[0050] Figure 18 It is a schematic diagram of an outdoor experimental device based on natural sunlight; among them, a is the schematic diagram of the outdoor experimental device, and b is the enlarged view.

[0051] Figure 19 It is the diagram of the change trend of the dissolved amount of metal ions and the sunlight intensity over time during the recovery of Li + and Co 2+ in the cathode material of a photo-driven lithium-ion battery under sunlight irradiation.

[0052] Figure 20 It is the diagram of the change trend of the daily dissolved amount of metal ions and the weather on the day during the 30-day outdoor empirical study of Test Example 2. Detailed implementation manner

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the specification of this invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0054] The present invention provides a method for recycling the cathode material of a photo-driven lithium-ion battery, comprising the following steps: constructing a water / oil two-phase photo-driven recycling system, where the photocatalyst is dispersed in the upper oil phase, and the cathode material and acid of the lithium-ion battery are dispersed in the lower water phase; applying light to the water / oil two-phase photo-driven recycling system in an oxygen or air atmosphere to drive the catalytic reaction, leaching metal ions from the cathode material of the lithium-ion battery, and then recovering the metal ions by chemical precipitation.

[0055] In a specific embodiment, the schematic diagram of the reaction system for recycling the cathode material of a photo-driven lithium-ion battery is as Figure 1 shown. The reaction in the water / oil two-phase photo-driven recycling system is carried out in a double-layer glass two-phase reactor (the inner layer is made of quartz for light transmission, and the outer layer has a jacket for temperature control). The top is open and connected to a gas inlet, and a magnetic stirrer is arranged at the bottom for stirring. The aqueous phase dispersed with the cathode material and acid of the lithium-ion battery is injected into the bottom of the reactor, and the oil phase dispersed with the photocatalyst is slowly added. The spatial separation is achieved through the density difference and interfacial characteristics of the two phases to form a clear interface. The light source irradiates the oil phase layer through the transparent reactor top cover, acting on the photocatalyst to drive the reaction, exciting the photocatalyst to generate H2O2 and using the photothermal effect to heat the reaction solution to accelerate the reaction. The generated H2O2 diffuses in situ to the aqueous phase, promoting the reduction of high-valent metal ions in the cathode material, thereby accelerating the dissolution and leaching of metal ions from the cathode material of the lithium-ion battery. During the reaction process, samples can be taken regularly to analyze the concentration of metal ions in the aqueous phase, and then the metal ions are recovered by chemical precipitation. In addition, a leachate collector is used to collect the metal ion solution, and the aqueous phase can be replaced.

[0056] In one embodiment of the present invention, the photocatalyst is selected from one or more of the following T1-T3 structures: 、 、 。

[0057] Figure 2 The infrared structural characterization spectrum of the photocatalyst shown in the T1-T3 structure. Figure 3 For the solid 13 13C NMR spectrum of the photocatalyst shown in the T1-T3 structure. Figure 4 The morphological characterization diagram of the photocatalyst shown in the T1-T3 structure; where a is the SEM image of the photocatalyst shown in the T1 structure, b is the SEM image of the photocatalyst shown in the T2 structure, c is the SEM image of the photocatalyst shown in the T3 structure, d is the TEM image of the photocatalyst shown in the T1 structure, e is the TEM image of the photocatalyst shown in the T2 structure, and f is the TEM image of the photocatalyst shown in the T3 structure.

[0058] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited do not limit the present invention.

[0059] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods, and the materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified.

[0060] Example 1 A method for recycling the cathode material of a photo-driven lithium-ion battery uses Figure 1 the reaction system for recycling the cathode material of a photo-driven lithium-ion battery shown in the figure, and specifically includes the following steps: Configuration of the oil phase: Disperse the photocatalyst (30 mg) shown in Structure T1 in n-octanol (15 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0061] Configuration of the water phase: Add LiCoO2 (50 mg) to 0.2 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio (the volume ratio of the oil phase and the water phase) is 1:1.

[0062] Construct a water / oil two-phase photo-driven recycling system, slowly add the above-mentioned oil phase to the water phase, and spontaneously form a stable oil-water interface. Pass oxygen into the water / oil two-phase photo-driven recycling system, then seal the reactor, irradiate it with a 300 W xenon lamp light source, and at the same time use a Fresnel lens to adjust the light intensity in the range of 500 mW·cm -2 to maintain the water phase temperature at about 80 °C, and metal ions gradually leach out from the cathode material of the lithium-ion battery. After the leaching process is completed, an leaching solution containing Li + and Co 2+ is obtained, and the selective recovery of metals needs to be carried out by the fractional precipitation method. Add 65 mg of oxalic acid to every 50 mL of the leaching solution and stir for 30 minutes. Filter and wash the generated pink precipitate to obtain cobalt oxalate solid and lithium-rich solution. Subsequently, add 10 mL of saturated sodium carbonate aqueous solution to the lithium-rich solution, heat it at 95 °C for 2 hours, filter the generated white precipitate and wash it repeatedly with water, and finally obtain lithium carbonate solid.

[0063] Example 2 A method for recycling the cathode material of a photo-driven lithium-ion battery is basically the same as the method of Example 1, and the difference is that: Configuration of the oil phase: Disperse the photocatalyst (30 mg) shown in Structure T2 in n-octanol (15 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0064] Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.2 M aqueous acetic acid solution (15 mL), with an oil / water volume ratio of 1:1.

[0065] Example 3 A method for recycling the cathode material of a photo-driven lithium-ion battery is basically the same as the method in Example 1, except that: Oil phase preparation: Disperse the photocatalyst shown in the T3 structure (30 mg) in n-octanol (15 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0066] Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.2 M aqueous acetic acid solution (15 mL), with an oil / water volume ratio of 1:1. During the reaction process of Examples 1-3, take aqueous phase samples (0.15 mL) every hour, and filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After the filtrate is diluted in a certain proportion, use an inductively coupled plasma optical emission spectrometer to perform quantitative detection of the Li + and Co 2+ contents. The detection results are as Figure 5 and Figure 6 shown. Figure 5 The left figure in it shows the change of the amount of substance of Li + and Co 2+ that can be leached per gram of photocatalyst on average within 4 hours of light irradiation. The dissolution amounts of Li + and Co 2+ show an approximately linear growth trend with the light irradiation time, and the dissolution rates reach 3083 and 2555 μmol·h -1 ·g -1 -1, respectively. As shown in the right figure of Figure 5 , after 4 hours of light irradiation, the recovery rates (dissolution efficiencies) of Li + and Co 2+ are 72% and 61%, respectively.

[0067] Figure 6 shows a comparison chart of the dissolution amounts of metal ions when using the photocatalysts shown in the T1, T2, and T3 structures respectively, indicating that the dissolution amount of metal ions is the highest when using the photocatalyst shown in the T1 structure and the lowest when using the photocatalyst shown in the T3 structure.

[0068] Example 4 A method for recycling the cathode material of a photo-driven lithium-ion battery includes the following steps: Oil phase preparation: Disperse the photocatalyst shown in the T1 structure (30 mg) in n-octanol (15 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0069] Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.2 M aqueous citric acid solution (15 mL) with an oil / water volume ratio of 1:1.

[0070] Construct a water / oil two-phase photo-driven recovery system. Slowly add the above-mentioned oil phase to the aqueous phase to spontaneously form a stable oil-water interface. Introduce oxygen into the water / oil two-phase photo-driven recovery system, then seal the reactor, irradiate it with a 300 W xenon light source, and at the same time use a Fresnel lens to adjust the light intensity in the range of 500 mW·cm -2 to maintain the aqueous phase temperature at about 80 °C, and metal ions gradually leach from the positive electrode material of the lithium-ion battery. The collected aqueous phase leachate realizes the precipitation and recovery of metal ions through chemical precipitation.

[0071] During the reaction, take aqueous phase samples (0.15 mL) every hour, and filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, use an inductively coupled plasma optical emission spectrometer to quantitatively detect the contents of Li + and Co 2+ . The detection results are as Figure 7 shown. Figure 7 The left figure in + shows the variation of the amount of substances of Li 2+ and Co + that can be leached per gram of photocatalyst on average with time within 4 hours of light irradiation. The dissolution amounts of Li 2+ and Co -1 ·g -1 show an approximately linear growth trend with the light irradiation time, and the dissolution rates reach 4082 and 3805 μmol·h Figure 7 respectively. As shown in the right figure in + , after 4 hours of light irradiation, the recovery rates (dissolution efficiencies) of Li 2+ and Co

[0072] Example 5 A method for recovering the positive electrode material of a photo-driven lithium-ion battery is basically the same as the method in Example 1, except that: Oil phase preparation: Disperse the photocatalyst shown in the T1 structure (30 mg) in n-octanol (22.5 mL) and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0073] Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.2 M aqueous acetic acid solution (7.5 mL) with an oil / water volume ratio of 3:1.

[0074] Example 6 A method for recycling the cathode material of a photo-driven lithium-ion battery is basically the same as the method of Example 1, except that: Configuration of the oil phase: Disperse the photocatalyst (30 mg) shown in the T1 structure in n-octanol (20 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0075] Configuration of the water phase: Add LiCoO2 (50 mg) to 0.2 M acetic acid aqueous solution (10 mL), and the oil / water volume ratio is 2:1.

[0076] Example 7 A method for recycling the cathode material of a photo-driven lithium-ion battery is basically the same as the method of Example 1, except that: Configuration of the oil phase: Disperse the photocatalyst (30 mg) shown in the T1 structure in n-octanol (10 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0077] Configuration of the water phase: Add LiCoO2 (50 mg) to 0.2 M acetic acid aqueous solution (20 mL), and the oil / water volume ratio is 1:2.

[0078] Example 8 A method for recycling the cathode material of a photo-driven lithium-ion battery is basically the same as the method of Example 1, except that: Configuration of the oil phase: Disperse the photocatalyst (30 mg) shown in the T1 structure in n-octanol (7.5 mL), and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0079] Configuration of the water phase: Add LiCoO2 (50 mg) to 0.2 M acetic acid aqueous solution (22.5 mL), and the oil / water volume ratio is 1:3.

[0080] During the reaction process of Examples 5-8, take water phase samples (0.15 mL) every hour, and filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, an inductively coupled plasma optical emission spectrometer is used for quantitative detection of the contents of Li + and Co 2+ The detection results are as Figure 8 shown, Figure 8 It shows that within 4 hours of light irradiation, in the presence of an average of 1 g of photocatalyst, when the oil / water volume ratio is 1:3, the dissolution rates of Li + and Co 2+ reach 2474 and 2048 μmol·h -1 ·g -1In addition, in Examples 1 and 5 - 8, the performance is best when the oil / water volume ratio is 1:1. When the oil / water ratio is optimized from 3:1 to 1:1, the dissolution amounts of Li + and Co 2+ increase. However, when the oil / water ratio changes from 1:1 to 1:3, the dissolution amounts of Li + and Co 2+ decay, showing a volcano - type distribution pattern.

[0081] Example 9 A method for recycling the cathode material of a light - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.1 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio is 1:1.

[0082] Example 10 A method for recycling the cathode material of a light - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.4 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio is 1:1.

[0083] Example 11 A method for recycling the cathode material of a light - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.6 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio is 1:1.

[0084] Example 12 A method for recycling the cathode material of a light - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCoO2 (50 mg) to 1.0 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio is 1:1.

[0085] Example 13 A method for recycling the cathode material of a light - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCoO2 (50 mg) to 1.5 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio is 1:1.

[0086] During the reaction process of Examples 9 - 13, aqueous phase samples (0.15 mL) were taken every hour and filtered through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, inductively coupled plasma optical emission spectrometry was used to quantitatively detect the content of Li + and Co 2+ . The detection results are as shown in Figure 9 . Figure 9 It shows that within 4 hours of light irradiation, in the presence of an average of 1 g of photocatalyst, when the concentration of acetic acid is 1.5 M, the dissolution rates of Li + and Co 2+ reach 1925 and 1802 μmol·h -1 ·g -1 respectively. In addition, in Examples 1 and 9 - 13, the performance is the best when the concentration of acetic acid is 0.6 M. When the acid concentration is optimized from 0.1 M to 0.6 M, the dissolution amounts of Li + and Co 2+ increase. However, when the acetic acid concentration changes from 0.6 M to 1.5 M, the dissolution amounts of Li + and Co 2+ decay, showing a volcano - type distribution rule.

[0087] Example 14 A method for recycling the cathode material of a photo - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: 50 mg of LiFePO4 was added to 15 mL of 0.2 M acetic acid aqueous solution, and the oil / water volume ratio was 1:1.

[0088] During the reaction process, aqueous phase samples (0.15 mL) were taken every hour and filtered through a 0.22 μm needle filter to remove solid particles (unreacted LiFePO4). After dilution in a certain proportion, inductively coupled plasma optical emission spectrometry was used to quantitatively detect the content of Li + . The detection results are as shown in Figure 10 . The LiFePO4 cathode material shows excellent decomposition rate in this system, and almost 100% complete deconstruction is achieved in only 60 minutes, corresponding to a Li + dissolution rate of 15800 μmol·h -1 ·g -1 . Under these experimental conditions, the recovery rate of Li + reaches 98.7%.

[0089] Example 15 A method for recycling the cathode material of a photo - driven lithium - ion battery is basically the same as the method of Example 1, except that: Aqueous phase preparation: Add LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 (50 mg) into 0.2 M acetic acid aqueous solution (15 mL), with an oil / water volume ratio of 1:1.

[0090] During the reaction, take aqueous phase samples (0.15 mL) every hour and filter them through a 0.22 μm needle filter to remove solid particles (unreacted LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2). After dilution in a certain proportion, use an inductively coupled plasma optical emission spectrometer to quantitatively detect the contents of Li + 、Co 2+ 、Ni 2+ 、Mn 2+ . The detection results are as Figure 11 shown. Figure 11 The left figure in + shows the change of the amount of substance of Li 2+ 、Co 2+ 、Ni 2+ and Mn + that can be leached per gram of photocatalyst on average within 4 hours of light irradiation, demonstrating that the system still maintains excellent recovery ability for complex component materials. The dissolution rates of the four metal ions of Li 2+ 、Co 2+ 、Ni 2+ and Mn -1 ·g -1 reach 4033, 845, 887.5 and 758 μmol·h Figure 11 . As shown in the right figure in + 、Co 2+ 、Ni 2+ and Mn 2+ The recovery rates (dissolution efficiencies) are 93.6%, 82.1%, 85% and 75.9% respectively.

[0091] Example 16 A method for recycling the cathode material of a photo-driven lithium-ion battery, comprising the following steps: Oil phase preparation: Disperse the graphitic carbon nitride ( g -C3N4) photocatalyst (30 mg) in n-octanol (15 mL) and ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension.

[0092] Aqueous phase preparation: Add LiCoO2 (50 mg) into 0.2 M acetic acid aqueous solution (15 mL), with an oil / water volume ratio of 1:1.

[0093] Oxygen was introduced into the system, and then the reactor was sealed. It was irradiated with a 300 W xenon light source, and at the same time, a Fresnel lens was used to adjust the light intensity in the range of 500 mW·cm -2 to maintain the water phase temperature at about 80 °C, and metal ions gradually leached from the cathode material of the lithium-ion battery.

[0094] During the reaction, an aqueous phase sample (0.15 mL) was taken every hour and filtered through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain ratio, an inductively coupled plasma emission spectrometer was used to quantitatively detect the contents of Li + and Co 2+ . The detection results are as Figure 12 shown. Figure 12 The left figure in + shows the change in the amount of substance of Li 2+ and Co + that can be leached per gram of photocatalyst on average within 4 hours of light irradiation. In the first 2 hours of light irradiation, the dissolution amounts of Li 2+ and Co -1 showed an increasing trend with the light irradiation time, and the dissolution rates reached 1713 and 1258 μmol·h -1 ·g Figure 12 respectively. After 2 hours of light irradiation, the metal dissolution amount hardly increased any more. As shown in the right figure in + and Co 2+ , the recovery rates (dissolution efficiencies) of Li

[0095] Example 17 A method for recycling the cathode material of a light-driven lithium-ion battery is basically the same as the method in Example 1, except that: Configuration of the oil phase: The photocatalyst (15 mg) shown in the T1 structure was dispersed in n-octanol (15 mL) and ultrasonically dispersed for 10 minutes to form a uniformly dispersed suspension.

[0096] Configuration of the water phase: LiCoO2 (50 mg) was added to 0.2 M acetic acid aqueous solution (15 mL), and the oil / water volume ratio was 1:1.

[0097] Example 18 A method for recycling the cathode material of a light-driven lithium-ion battery is basically the same as the method in Example 1, except that: Configuration of the oil phase: The photocatalyst (45 mg) shown in the T1 structure was dispersed in n-octanol (15 mL) and ultrasonically dispersed for 10 minutes to form a uniformly dispersed suspension.

[0098] Aqueous phase preparation: Add LiCoO2 (50 mg) to 0.2 M acetic acid aqueous solution (15 mL), with an oil / water volume ratio of 1:1.

[0099] During the reaction process of Examples 17 - 18, take aqueous phase samples (0.15 mL) every hour, and filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, use an inductively coupled plasma optical emission spectrometer to perform quantitative detection of the Li + and Co 2+ contents. The detection results are as Figure 13 shown, Figure 13 showing that within 4 hours of light irradiation, in the presence of a photocatalyst concentration of 1 g / L as shown in the T1 structure, the dissolution rates of Li + and Co 2+ reach 2648 and 2223 μmol·h -1 ·g -1 respectively. When the catalyst concentration is 3 g / L, the dissolution rates of Li + and Co 2+ reach 2208 and 1888 μmol·h -1 ·g -1 respectively. It is proved that when the catalyst concentration is 2 g / L, the best performance is exhibited.

[0100] Comparative Example 1 A method for recycling the cathode material of a photo - driven lithium - ion battery includes the following steps: System solution preparation: Disperse the photocatalyst (30 mg) shown in the T1 structure in n - octanol (15 mL), ultrasonically disperse for 10 minutes to form a uniformly dispersed suspension, and directly add LiCoO2 (50 mg) and 0.2 mL of glacial acetic acid to the suspension.

[0101] Introduce oxygen into the system, then seal the reactor, irradiate with a 300 W xenon light source, and at the same time use a Fresnel lens to adjust the light intensity in the range of 500 mW·cm -2 to maintain the aqueous phase temperature at about 80 °C, and metal ions gradually leach out from the cathode material of the lithium - ion battery.

[0102] During the reaction process, take aqueous phase samples (0.15 mL) every hour, and filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, use an inductively coupled plasma optical emission spectrometer to perform quantitative detection of the Li + and Co 2+ contents. The detection results are as Figure 14 shown, Figure 14 The left figure in it shows that within 4 hours of light irradiation, the Li that can be leached+ and Co 2+ The change of the amount of substance over time. Li + and Co 2+ The dissolution amounts are very small, and the dissolution rates are 35 and 26 μmol·h -1 ·g -1 respectively. As shown in the right figure of Figure 14 , after 4 hours of light irradiation, the recovery rates (dissolution efficiencies) of Li + and Co 2+ are 0.8% and 0.6% respectively.

[0103] Comparative Example 2 A method for recycling the cathode material of a photo-driven lithium-ion battery, comprising the following steps: System solution preparation: Add the T1 photocatalyst (30 mg) and LiCoO2 (50 mg) into 0.2 M acetic acid aqueous solution (15 mL), and ultrasonically disperse for 10 minutes.

[0104] Introduce oxygen into the system, then seal the reactor, irradiate with a 300 W xenon lamp light source, and at the same time use a Fresnel lens to adjust the light intensity in the range of 500 mW·cm -2 to maintain the water phase temperature at about 80 °C, and metal ions gradually leach out from the cathode material of the lithium-ion battery.

[0105] During the reaction, take aqueous phase samples (0.15 mL) every hour, filter through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, use an inductively coupled plasma emission spectrometer to quantitatively detect the contents of Li + and Co 2+ . The detection results are as shown in Figure 15 . Figure 15 The left figure of + shows the change of the amount of Li 2+ and Co + that can be leached out per gram of photocatalyst on average within 4 hours of light irradiation. 2+ The dissolution amounts of Li -1 and Co -1 show an approximately linear growth trend with the light irradiation time, and the dissolution rates reach 1057 and 1055 μmol·h Figure 15 ·g + respectively. As shown in the right figure of 2+ , after 4 hours of light irradiation, the recovery rates (dissolution efficiencies) of Li

[0106] and Co Comparative Example 3 A method for recycling the cathode material of a photo-driven lithium-ion battery, comprising the following steps: Preparation of the oil phase: The photocatalyst (30 mg) shown in the T1 structure was dispersed in n-octanol (15 mL), and ultrasonic dispersion was carried out for 10 minutes to form a uniformly dispersed suspension.

[0107] Preparation of the water phase: LiCoO2 (50 mg) was added to 0.2 M aqueous acetic acid solution (15 mL), and the oil / water volume ratio was 1:1.

[0108] Argon was introduced into the system while the reactor was sealed, and irradiation was carried out with a 300 W xenon light source. At the same time, a Fresnel lens was used to adjust the light intensity in the range of 500 mW·cm -2 to maintain the water phase temperature at about 80 °C, and metal ions gradually leached from the cathode material of the lithium-ion battery.

[0109] During the reaction, aqueous phase samples (0.15 mL) were taken every hour and filtered through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, inductively coupled plasma optical emission spectrometry was used for quantitative detection of the contents of Li + and Co 2+ . The detection results are as Figure 16 shown. Figure 16 The left figure in + shows the variation of the amount of substance of Li 2+ and Co + and Co 2+ that could be leached per gram of photocatalyst on average within 4 hours of light irradiation. The dissolution amounts of Li -1 and Co -1 showed an approximately linear growth trend with the light irradiation time, but the dissolution rate was slow, being 294 and 128 μmol·h -1 ·g -1 respectively. As shown in the right figure in Figure 16 , after 4 hours of light irradiation, the recovery rates (dissolution efficiencies) of Li + and Co 2+ were only 6.9% and 3% respectively.

[0110] Test Example 1 To verify the long-term operation stability of the water / oil two-phase photo-driven recovery system of the present invention, a continuous cycle experiment was carried out. The reaction conditions were the same as those in Example 1. After each 4-hour reaction ended, the lower aqueous phase was taken out, and LiCoO2 (50 mg) and 0.2 M aqueous acetic acid solution (15 mL) were re-added.

[0111] Figure 17These are the experimental results of the cycling stability test. After the water / oil two-phase photocatalytic recovery system ran for 6 cycles (a total of 24 hours of reaction), the dissolution rate of metal ions did not show a significant decline, demonstrating the excellent stability of the water / oil two-phase photocatalytic recovery system. The excellent stability of the water / oil two-phase photocatalytic recovery system is mainly attributed to the following factors: 1. The n-octanol oil phase can act as a hole sacrificial agent, which can not only accelerate the oxygen reduction to produce H2O2, but also effectively inhibit the self-oxidation of the catalyst; 2. The establishment of the two-phase interface enables the in-situ generated H2O2 to migrate rapidly and directionally to the aqueous phase, and then participate in the decomposition reaction of LiCoO2, avoiding the continuous exposure of the photocatalyst to the environment of H2O2 and reactive oxygen species, thereby further reducing the degradation risk of the photocatalyst. 3. In the molecular structure of the photocatalyst, a rigid and irreversible benzobisoxazole structure is used as the linking unit, greatly improving its chemical stability in the case of heating and acidic media.

[0112] Test Example 2 Based on the feasibility at the laboratory scale, an outdoor scaled-up experimental system based on natural sunlight was constructed. The outdoor experimental device is shown in Figure 18 a as shown, and the enlarged view is shown in Figure 18 b as shown. In the outdoor experiment, a 70 cm × 70 cm square Fresnel lens was used to focus sunlight so that the light spot could cover the entire reactor. The angle and distance between the lens and the reactor were continuously adjusted according to the position of the sun to achieve the regulation of light intensity and reaction temperature.

[0113] The reaction conditions in the outdoor experiment were scaled up by 20 times compared with those in the laboratory. The specific reaction conditions are as follows: Configuration of the oil phase: Disperse the T1 photocatalyst (600 mg) in n-octanol (300 mL), and form a homogeneous dispersion system by ultrasonic treatment; Configuration of the aqueous phase: Disperse LiCoO2 (1 g) in 0.6 M aqueous acetic acid solution (300 mL), and the oil / water volume ratio is 1:1.

[0114] After the water and oil phases were loaded into the reactor, it was sealed outdoors under an air atmosphere. This device can save the energy consumption of artificial light sources and heating devices. At the same time, a peristaltic pump (flow rate 0.5 - 50 mL·min -1 adjustable) was configured to achieve the timely separation of products and the timely replenishment of raw materials. The metal ion solution precipitated in the lower layer can be exported to the storage tank in real time, and the fresh acetic acid solution in the lower layer can be continuously input into the reaction. The temperature, natural light intensity, and focused light intensity were recorded in real time through a thermometer and a light intensity meter.

[0115] During the reaction process, aqueous phase samples (0.15 mL) were taken every hour and filtered through a 0.22 μm needle filter to remove solid particles (unreacted LiCoO2). After dilution in a certain proportion, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to quantitatively detect the contents of Li + and Co 2+ . The detection results are as shown in Figure 19 . Under the condition of full sunlight irradiation throughout the process, the cumulative dissolution amounts of Li + and Co 2+ reached 10371.7 and 9472.5 μmol respectively, and the corresponding dissolution rates could reach 1482 and 1353 μmol·h -1 . The dissolution rate of metal ions showed a strong positive correlation with sunlight intensity. During the startup stage (09:00 - 12:00) with an initial light intensity of 30 - 60 mW·cm -2 , the dissolution rates of Li + and Co 2+ stabilized at ~2200 μmol·h -1 and ~2000 μmol·h -1 respectively; while when the sunlight intensity gradually decreased to 20 - 50 mW·cm -2 during the period (13:00 - 15:00), the average dissolution rates of Li + and Co 2+ could only reach ~600 μmol·h -1 . During the period from 15:00 to 16:00, the dissolution rate of metal ions almost dropped to zero.

[0116] The sunlight-driven outdoor system demonstrated excellent long-term operation stability and practical application prospects. A 30-day outdoor empirical study was carried out, and the research results are as shown in Figure 20 . It was proved that within a complete experimental cycle including 4 cloudy days, the recovery efficiency of system metal ions remained stable, and the daily average dissolution amounts of Li + and Co 2+ reached 8.7 mmol and 8.4 mmol respectively. Particularly noteworthy is that even on the 7th day with the lowest light intensity during the experiment (cloudy weather, average temperature 8 °C, average daily sunlight intensity only 30 mW·cm -2 ), the system still maintained a dissolution efficiency of about 60%. The continuous and stable operation of the system achieved the recovery of high-value metal ions in lithium-ion batteries completely relying on solar energy. This technological breakthrough verified the feasibility of using solar energy as a single energy input to achieve efficient recycling of waste batteries.

[0117] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. Those skilled in the art should understand that other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for recycling the cathode material of a light-driven lithium-ion battery, characterized in that, It includes the following steps: Construct a water / oil two-phase photocatalytic recovery system, where the photocatalyst is dispersed in the upper oil phase, and the cathode material of the lithium-ion battery and the acid are dispersed in the lower water phase; apply light to the water / oil two-phase photocatalytic recovery system in an oxygen or air atmosphere to drive the catalytic reaction, leach metal ions from the cathode material of the lithium-ion battery, and then recover the metal ions by chemical precipitation.

2. The method according to claim 1, wherein, The photocatalyst is selected from one or more of the following T1-T3 structures: 、 、 。 3. The method according to claim 1, characterized in that, The photocatalyst is obtained by reacting an aldehyde monomer with an amine monomer in an organic solvent at 80-150 °C. The aldehyde monomer is 2,3,6,7,10,11-hexakis(4-formylphenyl)triphenylene, and the amine monomer is 2,5-diamino-1,4-benzenedithiophene dihydrochloride, 2,5-diamino-1,4-dihydroxybenzene dihydrochloride, or 1,2,4,5-benzenetetramine tetrahydrochloride.

4. The method according to claim 1, characterized in that, The concentration of the photocatalyst in the oil phase is 0.1-100 g / L.

5. The method according to claim 1, wherein The oil phase is a water-insoluble alcohol solvent with a density less than that of water and a boiling point greater than 100 °C.

6. The method according to claim 1, wherein The positive electrode material of the lithium ion battery is selected from one or more of LiCoO2, LiFePO4, LiCo x Ni y Mn 1-x-y O2, LiMn2O4, LiNiCoAlO2, LiV2O4, Li2FeTiO4; wherein, 0 < x, 0 < y, and x + y < 1.

7. The method according to claim 1, wherein The concentration of the cathode material of the lithium-ion battery in the water phase is 0.1-100 g / L.

8. The method according to claim 1, characterized in that The acid is selected from one or more of sulfuric acid, hydrochloric acid, nitric acid, formic acid, acetic acid, citric acid, maleic acid, malic acid, and ascorbic acid.

9. The method according to claim 1, wherein The concentration of the acid in the water phase is 0.05-5 M.

10. The method according to claim 1, characterized in that, The volume ratio of the oil phase to the water phase is (0.1-10):1.

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