A copper-based catalyst, its preparation method and use

Abstract

This invention belongs to the field of electrochemistry, and particularly relates to a copper-based catalyst, its preparation method, and its application. The preparation method provided by this invention includes the following steps: a) placing a copper foil downstream of a tube furnace and a thiourea upstream of the tube furnace, then continuously introducing an inert gas into the tube furnace. After the air in the furnace is purged, the material inside the furnace is heated and calcined to obtain a copper foil with Cu2S loaded on its surface; b) spraying a CuS dispersion onto the surface of the copper foil with Cu2S loaded on its surface, then placing it in a tube furnace, and then continuously introducing an inert gas into the tube furnace. After the air in the furnace is purged, the material inside the furnace is heated and calcined to obtain a copper-based catalyst. The preparation method provided by this invention has the advantages of low preparation cost and high catalytic activity and stability of the product. Using the copper-based catalyst prepared by this method as a working electrode, it can efficiently and stably achieve the selective deposition of cobalt and nickel in the chlorination leaching solution of waste ternary lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry, and particularly relates to a copper-based catalyst, its preparation method, and its application. Background Technology

[0002] The rapid development of the global electronics and electric vehicle industries has driven the widespread application of lithium-ion batteries, but it has also led to a year-on-year increase in the number of spent lithium-ion batteries. Spent ternary lithium-ion batteries contain key metals such as cobalt, nickel, manganese, and lithium, and have significant economic and strategic value, necessitating the development of sustainable recycling strategies.

[0003] Currently, the recycling of spent ternary lithium-ion batteries mainly relies on hydrometallurgical processes, which involve leaching the collected active materials with acid to transfer the metals from the solid phase to the liquid phase for further purification. Cobalt and nickel, due to their similar physicochemical properties, present challenges in selectively separating them from the leachate. Existing recycling processes primarily rely on solvent extraction, precipitation, or combinations thereof to achieve cobalt-nickel separation, but these methods have the following limitations: high cost due to the extensive use of specialized extractants and precipitants; complex and inefficient processes requiring multiple separation and purification steps; and environmental pollution caused by the generation of large amounts of wastewater and waste.

[0004] Electrochemical methods, with their sustainability and good compatibility with renewable energy, represent a promising metal recovery technology. Electrodeposition, as a simple and easily tunable method, can achieve metal separation and recovery by controlling nucleation, growth, and sediment composition. However, due to the similar standard reduction potentials of cobalt and nickel in the leaching solution, the electrodeposition process suffers from inherent selectivity limitations, leading to severe co-deposition and low separation efficiency. Existing research has explored selective separation of cobalt and nickel through electrolyte regulation and interface design, but these efforts still face challenges such as excessive energy consumption, high cost, and low deposition efficiency.

[0005] To address this contradiction, current research has shifted towards designing inexpensive and efficient catalyst electrodes. Copper-based sulfides, with their advantages of high conductivity, abundant active sites, and low cost, have become an ideal choice for controlling electrodeposition cathode materials, and hold promise for achieving selective separation and recycling of cobalt and nickel from spent lithium-ion batteries with low power consumption, low cost, and high efficiency. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a copper-based catalyst, its preparation method and application. The copper-based catalyst preparation method provided by the present invention has the advantages of low preparation cost and high catalytic activity and stability of the product. Using the copper-based catalyst prepared by this method as a working electrode, through electrolyte regulation and electrode interface design, selective deposition of cobalt and nickel in the chlorination leaching solution of waste ternary lithium-ion batteries can be achieved efficiently and stably.

[0007] This invention provides a method for preparing a copper-based catalyst, comprising the following steps:

[0008] a) Place the copper foil downstream of the tube furnace and the thiourea upstream of the tube furnace. Then, continuously introduce inert gas into the tube furnace. After the air in the furnace is exhausted, heat up and calcine the material in the furnace to obtain copper foil with Cu2S loaded on the surface, named: Cu2S / Cu.

[0009] b) Spray CuS dispersion onto the surface of the copper foil loaded with Cu2S, then place it in a tube furnace, and then continuously introduce inert gas into the tube furnace. After the air in the furnace is purged, heat up and calcine the material in the furnace to obtain a copper-based catalyst, named: CuS / Cu2S / Cu.

[0010] In the above preparation method, preferably, the thickness of the copper foil is selected to be 0.2~0.3mm, specifically 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.29mm or 0.3mm. A higher copper foil thickness can ensure the stability of the electrode design for the copper-based catalyst.

[0011] In the above preparation method, preferably, in step a), the copper foil is cleaned before being placed in the tube furnace.

[0012] In the above preparation method, preferably, in step a), the copper foil is cleaned using a 1:1 (volume ratio) mixture of acetone and deionized water, and ultrasonically cleaned for 20-30 minutes to remove oxides and impurities from the surface of the copper foil.

[0013] In the above preparation method, preferably, in step a), the thiourea is ground before entering the tube furnace to ensure a more uniform gas-solid reaction.

[0014] In the above preparation method, preferably, in step a), the mass of the thiourea is 0.2~0.3g.

[0015] In the above preparation method, preferably, in step a), the distance between the copper foil and thiourea in the tube furnace is selected to be 6~10cm, specifically 6cm, 7cm, 8cm, 9cm or 10cm, to ensure greater stability during the gas-solid reaction.

[0016] In the above preparation method, preferably, in step a), the inert gas is argon.

[0017] In the above preparation method, preferably, in step a), the flow rate of the inert gas is selected to be 100~150 mL / min, specifically 100 mL / min, 110 mL / min, 120 mL / min, 130 mL / min, 140 mL / min, or 150 mL / min; the heating rate of the calcination is selected to be 1~3℃ / min, specifically 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, or 3℃ / min; the final calcination temperature is selected to be 350~450℃, specifically 350℃, 370℃, 400℃, 420℃, or 450℃; and the holding time at the final calcination temperature is selected to be 1~2 h, specifically 1 h, 1.5 h, or 2 h. These conditions can enhance the growth stability of Cu2S on the copper foil surface.

[0018] In the above preparation method, preferably, in step b), the CuS content in the CuS dispersion is selected to be 2~5 mg / mL, specifically 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 3.5 mg / mL, 3.75 mg / mL, 4 mg / mL, 4.5 mg / mL or 5 mg / mL.

[0019] In the above preparation method, preferably, in step b), the liquid medium in the CuS dispersion is ethanol.

[0020] In the above preparation method, preferably, in step b), the CuS dispersion is prepared according to the following steps:

[0021] Sodium sulfide solution was slowly added dropwise to copper chloride solution, and the resulting black powder was collected at room temperature, which is CuS powder; then the CuS powder was completely dispersed in ethanol.

[0022] In the above preparation method, preferably, in step b), the molar ratio of sodium sulfide in the sodium sulfide solution to copper chloride in the copper chloride solution is 1:1.

[0023] In the above preparation method, preferably, in step b), the spraying amount of the CuS dispersion is (2~8) mg / cm³. 2 Specifically, it can be 2 mg / cm³ 2 3mg / cm 2 4mg / cm 2 5mg / cm 2 5.3 mg / cm 2 6mg / cm 2 7mg / cm 2 Or 8mg / cm 2 .

[0024] In the above preparation method, preferably, in step b), the spraying method is air spraying, that is, using compressed air to atomize the CuS dispersion and spray it evenly on the Cu2S / Cu surface to form a smooth and uniform coating.

[0025] In the above preparation method, preferably, in step b), the spraying pressure is selected to be 0.2~0.4MPa, specifically 0.2MPa, 0.25MPa, 0.3MPa, 0.35MPa or 0.4MPa; the spraying distance is selected to be 5~10cm, specifically 5cm, 6cm, 7cm, 8cm, 9cm or 10cm.

[0026] In the above preparation method, preferably, in step b), the inert gas is argon.

[0027] In the above preparation method, preferably, in step b), the flow rate of the inert gas is selected to be 50~100 mL / min, specifically 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, or 100 mL / min; the heating rate of the calcination is selected to be 4~6℃ / min, specifically 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, or 6℃ / min; the final calcination temperature is selected to be 100~200℃, specifically 100℃, 120℃, 150℃, 170℃, or 200℃; and the holding time at the final calcination temperature is selected to be 2~4 h, specifically 2 h, 2.5 h, 3 h, 3.5 h, or 4 h. These conditions can promote the crystal growth of CuS on the Cu2S / Cu surface, enhance the material stability, and form a CuS / Cu2S / Cu heterojunction composite material.

[0028] In the above preparation method, Cu2S / Cu is first generated in situ by gas-solid reaction on the surface of copper foil through a tube furnace. Then, a smooth and uniform CuS coating is formed on the surface of Cu2S / Cu by spraying. Finally, CuS crystals are promoted to grow by calcination in a tube furnace to form a stable CuS / Cu2S / Cu heterostructure composite material.

[0029] The present invention also provides a copper-based catalyst prepared according to the preparation method described above; the copper-based catalyst comprises: copper foil, Cu2S supported on the surface of the copper foil, and CuS supported on the surface of the Cu2S.

[0030] In the above-mentioned copper-based catalysts, preferably, the Cu2S is in the form of tiles, and the CuS is in the form of nanoparticles.

[0031] In the above-mentioned copper-based catalysts, preferably, the nanoparticles have a particle size of 50~200 nm.

[0032] The present invention also provides an application of the copper-based catalyst described above in the selective recovery of cobalt and nickel from waste ternary lithium-ion batteries.

[0033] This invention also provides a method for selectively recycling cobalt and nickel from waste ternary lithium-ion batteries, comprising the following steps:

[0034] A three-electrode system was adopted, using the chlorination leachate of waste ternary lithium-ion battery cathode material as the electrolyte for electrochemical deposition, to deposit cobalt and / or nickel on the surface of the working electrode;

[0035] The working electrode includes: the copper-based catalyst described in the above technical solution, and polydimethyldiallyl ammonium chloride (PDADMAC) supported on the surface of the copper-based catalyst.

[0036] In the above-mentioned method for selectively recovering cobalt and nickel, preferably, the number-average molecular weight of the PDADMAC is selected to be 200,000 to 350,000.

[0037] In the above-mentioned methods for selectively recovering cobalt and nickel, preferably, the PDADMAC loading is selected to be 0.03~0.08 mg / cm³ during cobalt deposition. 2 Specifically, it can be 0.03 mg / cm³. 2 0.04 mg / cm 2 0.05 mg / cm 2 0.06 mg / cm 2 0.07 mg / cm 2 Or 0.08 mg / cm 2 The optimal PDADMAC loading for nickel deposition is 1–5 mg / cm³. 2 Specifically, it can be 1 mg / cm³ 2 2mg / cm 2 3mg / cm 2 4mg / cm 2 Or 5mg / cm 2 .

[0038] In the above-described method for selectively recovering cobalt and nickel, preferably, the PDADMAC is loaded in the following manner:

[0039] Dissolve PDADMAC in a 1:1 (volume ratio) mixture of ethanol and deionized water, then drop it onto the surface of the copper-based catalyst using a pipette and allow it to air dry.

[0040] In the above-mentioned method for selectively recovering cobalt and nickel, preferably, 10 mol / L HCl is used to leach the positive electrode active material of the waste ternary lithium-ion battery, and LiOH is used to adjust the pH value of the leachate to 3, so as to create a recovery environment for cobalt and nickel in the electrolyte.

[0041] In the above-described methods for selectively recovering cobalt and nickel, preferably, the electrodeposition of cobalt and nickel is reversible and can be easily stripped off in solution. For example, complete stripping of cobalt and nickel from the working electrode surface can be achieved by applying a potential of -0.01 V vs. Ag / AgCl in 5 mmol / L NaNO3 at pH 3.

[0042] In the above-mentioned method for selectively recovering cobalt and nickel, preferably, the recovery of cobalt and nickel from the leachate can be carried out through multiple electrodeposition and adsorption-desorption processes until the desired cobalt and nickel purity and recovery rate are obtained.

[0043] In the above-mentioned methods for selectively recovering cobalt and nickel, preferably, when the Co / Ni ratio of the leachate is too high, Co electrodeposition can be selectively performed, and when the Ni / Co ratio of the leachate is too high, Ni electrodeposition can be selectively performed. These two selective deposition processes can work in a complementary manner to control the Co / Ni ratio of the leachate at an appropriate level.

[0044] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0045] (1) The copper-based catalyst (CuS / Cu2S / Cu) prepared by the method provided in this invention has a multi-level layered structure. Cu2S grows on the surface of copper foil in the form of tiles. CuS is uniformly loaded on the surface of Cu2S in the form of nanoparticles of about 50~200 nm, which has a large specific surface area and can expose more active sites.

[0046] (2) The copper-based catalyst prepared by the method provided in this invention has a two-interface heterostructure, which can construct a high-speed conductive channel and enhance charge transfer.

[0047] (3) The copper-based catalyst prepared by the method provided in this invention has more active sites, optimized electron transfer paths and lower charge transfer impedance. Compared with copper foil, Cu2S / Cu and CuS / Cu, it shows an earlier electrochemical deposition window, that is, the best deposition effect can be achieved at a lower voltage.

[0048] (4) The copper-based catalyst prepared by the method provided in this invention has the advantages of high conductivity, high catalytic activity, low cost and high acid stability. It can be used efficiently and stably for metal recovery from waste ternary lithium-ion battery acid leaching solution. When the copper-based catalyst prepared in this invention is used as the working electrode, after two selective electrodeposition operations of cobalt and one selective electrodeposition operation of nickel, the final metal purity can reach about 95%. Compared with simple copper foil, the deposition amount of this catalyst can be increased by 2 to 4 times. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0050] Figure 1 The image shows a SEM image of the CuS / Cu2S / Cu catalyst prepared in Example 1.

[0051] Figure 2 (a) is the XRD pattern of the CuS / Cu2S / Cu catalyst prepared in Example 1. Figure 2 (b) XRD patterns of CuS crystallization growth at different temperatures;

[0052] Figure 3 The polarization curves obtained by LSV testing in cobalt or nickel electrolytes for Comparative Examples 4, 5, 6 and 2, respectively, using copper foil, Cu2S / Cu, CuS / Cu and CuS / Cu2S / Cu as working electrodes.

[0053] Figure 4 The LSV polarization curves and it curves were obtained by comparing Comparative Examples 4, 5, 6 and 2 with copper foil, Cu2S / Cu, CuS / Cu and CuS / Cu2S / Cu as working electrodes, respectively, in a mixed cobalt and nickel electrolyte. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] This embodiment provides a method for preparing a copper-based catalyst CuS / Cu2S / Cu, including the following steps:

[0057] (1) Cut a 0.3 mm thick copper foil into 1×1.5 cm pieces, clean it with an ultrasonic cleaning solution of acetone and deionized water in a 1:1 (volume ratio), place it on an alumina ceramic boat, and place it downstream of the tube furnace.

[0058] (2) Grind 0.2 g of thiourea in a corundum mortar and place it on an alumina ceramic boat. Place the boat upstream of the tube furnace with a distance of 8 cm between the two boats.

[0059] (3) Argon gas is continuously introduced into the tube furnace at a flow rate of 100 mL / min. After the air in the furnace is exhausted, the material is calcined by the first programmed temperature rise at a rate of 2 °C / min and held at 400 °C for 1 h. After natural cooling, the downstream alumina ceramic boat is taken out and the material is named Cu2S / Cu.

[0060] (4) Prepare sodium sulfide solution and copper chloride solution respectively. According to the molar ratio of sodium sulfide to copper chloride of 1:1, slowly add sodium sulfide solution to copper chloride solution. Centrifuge at room temperature to collect the black powder generated, transfer it to a corundum mortar and let it dry naturally, then grind it thoroughly and name it CuS Precursors.

[0061] (5) Disperse 8 mg CuS Precursors thoroughly in 2 mL of ethanol, and then use air spraying to completely disperse them on the Cu2S / Cu surface. The spraying pressure is 0.3 MPa and the spraying distance is 10 cm. After spraying, place them in an alumina ceramic boat.

[0062] (6) The alumina ceramic boat was sent into a tube furnace and argon gas was continuously introduced into the tube furnace at a flow rate of 50 mL / min. After the air in the furnace was exhausted, the material was calcined by a second programmed temperature rise at a rate of 5 °C / min and held at 200 °C for 3 h. After natural cooling, the material was taken out from the alumina ceramic boat and a copper-based catalyst was finally obtained, named CuS / Cu2S / Cu.

[0063] Comparative Example 1

[0064] This comparative example prepared a copper-based catalyst using a similar method to Example 1, except that in step (6), the heating rate was 5 °C / min, and the temperature was maintained at 300 °C for 3 h. The remaining steps were the same as in Example 1.

[0065] Figure 1The image shows a SEM image of the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1. Its morphology is a multi-level layered structure. Cu2S appears as tiles on the surface of the copper foil, and CuS is uniformly loaded as nanoparticles of about 50~200 nm on the surface of Cu2S, which has a large specific surface area.

[0066] Figure 2 (a) is the XRD pattern of the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1. Diffraction peaks of Cu2S and Cu can be observed, while the diffraction peak of CuS is masked due to its weak intensity. Therefore, powder XRD tests can be performed on CuS precursors and reactants at different temperatures, such as... Figure 2 As shown in (b), it can be clearly seen that CuS Precursors crystals grow after the reaction, and the crystallinity is significantly improved. However, when the temperature is raised to 300 °C, CuS begins to show impurity peaks, which means that impurities will be generated at this time.

[0067] Comparative Example 2

[0068] This comparative example provides a method for preparing a copper-based catalyst Cu2S / Cu, including the following steps:

[0069] (1) Cut a 0.3 mm thick copper foil into 1×1.5 cm pieces, clean it with an ultrasonic cleaning solution of acetone and deionized water in a 1:1 (volume ratio), place it on an alumina ceramic boat, and place it downstream of the tube furnace.

[0070] (2) Grind 0.2 g of thiourea in a corundum mortar and place it on an alumina ceramic boat. Place the boat upstream of the tube furnace with a distance of 8 cm between the two boats.

[0071] (3) Argon gas is continuously introduced into the tube furnace at a flow rate of 100 mL / min. After the air in the furnace is exhausted, the material is calcined by programmed heating at a rate of 2 °C / min and held at 400 °C for 1 h. After natural cooling, the downstream alumina ceramic boat is removed and the resulting material is named Cu2S / Cu.

[0072] Comparative Example 3

[0073] This comparative example provides a method for preparing a copper-based catalyst CuS / Cu, including the following steps:

[0074] (1) Cut a 0.3 mm thick copper foil into 1×1.5 cm pieces and clean it with ultrasonic cleaning solution of acetone and deionized water in a 1:1 (volume ratio);

[0075] (2) Prepare sodium sulfide solution and copper chloride solution respectively. According to the molar ratio of sodium sulfide to copper chloride of 1:1, slowly add sodium sulfide solution to copper chloride solution. Centrifuge at room temperature to collect the black powder generated, transfer it to a corundum mortar and let it dry naturally, then grind it thoroughly and name it CuS Precursors.

[0076] (3) Place CuS Precursors in an alumina ceramic boat and then send it into a tube furnace. Continuously introduce argon gas into the tube furnace at a flow rate of 50 mL / min. After the air in the furnace is exhausted, calcine the material by programmed temperature increase at a rate of 5 °C / min and hold at 200 °C for 3 h. After natural cooling, remove the material from the alumina ceramic boat to obtain CuS powder.

[0077] (4) 8 mg CuS powder was thoroughly dispersed in 2 mL of ethanol and 50 μL of 5% Nafion solution was added as a binder. Then, it was completely dispersed on the copper foil surface by air spraying. The spraying pressure was 0.3 MPa and the spraying distance was 10 cm. The material obtained after spraying was named CuS / Cu.

[0078] Example 2

[0079] Using the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1 as the working electrode, the electrochemical performance was studied in an electrolyte containing cobalt and nickel, including the following steps:

[0080] (1) The electrodeposition process was carried out using a three-electrode system. The working electrode used was the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1, the counter electrode was a platinum wire, and the reference electrode was an Ag / AgCl electrode. The working electrode CuS / Cu2S / Cu was cut to 1×1.5 cm, and the surface impurities of the contact portion between the back and the electrode clamp were removed with a scraper to construct an ohmic contact. The contact portion between the working electrode and the electrolyte was 1×0.5 cm, and the remaining portion was isolated from the electrolyte with black insulating tape to ensure the accuracy of the working area.

[0081] (2) Prepare an electrolyte containing 10 mmol / L NiCl2 and 10 mol / L LiCl, and perform LSV testing on the working electrode within the potential range of -0.3 ~ -0.8 V vs. Ag / AgCl. Then prepare an electrolyte containing 10 mmol / L CoCl2 and 10 mol / L LiCl, and perform another LSV test on the working electrode within the same potential range.

[0082] (3) Prepare an electrolyte containing 10 mmol / L NiCl2, 10 mmol / L CoCl2 and 10 mol / L LiCl, and perform LSV testing on the working electrode with a potential range of -0.3 ~ -0.8 V vs. Ag / AgCl. Then perform it curve testing on the working electrode with a potential set to -0.65 V vs. Ag / AgCl.

[0083] Comparative Example 4

[0084] Compared to Example 2, Comparative Example 4 directly used a cleaned 1×1.5 cm copper foil as the working electrode. All other operating steps and parameters were the same.

[0085] Comparative Example 5

[0086] Compared with Example 2, Comparative Example 5 directly used the Cu2S / Cu synthesized in Comparative Example 2 as the working electrode, and the remaining operation steps and parameters were the same.

[0087] Comparative Example 6

[0088] Compared with Example 2, Comparative Example 6 directly used the CuS / Cu synthesized in Comparative Example 3 as the working electrode, and the remaining operation steps and parameters were the same.

[0089] Figure 3 For Comparative Examples 4, 5, 6, and 2, the polarization curves obtained from the LSV test in step (2) were performed using copper foil, Cu2S / Cu, CuS / Cu, and CuS / Cu2S / Cu as working electrodes, respectively. The results showed a clear distinction in the deposition initiation potentials of cobalt and nickel in this reaction system. This is because cobalt and nickel undergo complexation in concentrated chloride solution, resulting in the two species existing as ions with opposite charges, forming an electrochemical window for selective deposition of cobalt and nickel. That is, lower potentials favor nickel deposition, while higher potentials favor cobalt deposition. Furthermore, it was clearly observed that when CuS / Cu2S / Cu was used as the working electrode, the electrochemical window was significantly advanced, and the corresponding current density was significantly increased. This means that only a lower working voltage is needed to achieve higher deposition rates and selectivity. This is because the CuS / Cu2S / Cu catalyst has more active sites, an optimized electron transfer path, and lower charge transfer impedance.

[0090] Figure 4For Comparative Examples 4, 5, 6, and 2, copper foil, Cu2S / Cu, CuS / Cu, and CuS / Cu2S / Cu were used as working electrodes, respectively, and the LSV polarization curves and it curves obtained in step (3) were tested. The results showed that the CuS / Cu2S / Cu working electrode always had a higher current density at the same potential, and the current density could be increased by 5 to 10 times compared with copper foil. This indicates that the CuS / Cu2S / Cu catalyst has significantly enhanced catalytic activity, which is attributed to the morphology control and heterostructure design of the catalyst.

[0091] Example 3

[0092] In a mixed electrolyte containing 10 mmol / L NiCl2, 10 mmol / L CoCl2, and 10 mol / L LiCl, the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1 was used as the working electrode. Cobalt and nickel were deposited at different potentials, and their contents were tested. Further, a PDADMAC coating was applied to its surface to control the selective deposition of cobalt and nickel, including the following steps:

[0093] (1) The electrodeposition method was performed using a three-electrode system. The working electrode was the CuS / Cu2S / Cu catalyst prepared according to the above technical solution, the counter electrode was a platinum wire, and the reference electrode was an Ag / AgCl electrode. The electrolyte was an aqueous solution containing 10 mmol / L NiCl2, 10 mmol / L CoCl2, and 10 mol / L LiCl. The working electrode CuS / Cu2S / Cu was cut into 1×1.5 cm pieces, and the surface impurities of the part in contact with the electrode clamp on the back were removed with a scraper to construct an ohmic contact. The part of the working electrode in contact with the electrolyte was left at 1×0.5 cm, and the rest was isolated from the electrolyte with black insulating tape to ensure the accuracy of the working area. PDADMAC with a number average molecular weight of 200,000~350,000 was dissolved in a 1:1 (volume ratio) mixture of ethanol and deionized water, and the PDADMAC dispersion was uniformly drop-coated onto the surface of the working electrode using a pipette.

[0094] (2) Conditions favorable for selective nickel deposition: Multiple it curve tests were performed within the voltage range of -0.52 ~ -0.56 V vs. Ag / AgCl. An additional coating of 2 mg / cm³ concentration was applied to the electrode at the intermediate potential of -0.54 V vs. Ag / AgCl. 2 PDADMAC was used to further control the selective deposition of nickel. Finally, each deposited electrode was digested and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine the content of cobalt and nickel.

[0095] (3) Conditions favorable for selective cobalt deposition: Multiple it curve tests were performed within the voltage range of -0.66 ~ -0.7 V vs. Ag / AgCl. An additional coating of 0.05 mg / cm³ was applied to the electrode at the intermediate potential of -0.68 V vs. Ag / AgCl. 2 PDADMAC was used to further control the selective deposition of cobalt. Finally, each deposited electrode was digested and analyzed by ICP-MS to determine the cobalt and nickel content.

[0096] Comparative Example 7

[0097] In a mixed electrolyte containing 10 mmol / L NiCl2, 10 mmol / L CoCl2, and 10 mol / L LiCl, a cleaned copper foil was used as the working electrode. A PDADMAC coating was applied to its surface to further control the selective deposition of cobalt and nickel, in order to study the differences in the electrochemical deposition window. The process included the following steps:

[0098] (1) The electrodeposition method was performed using a three-electrode system. The working electrode was a copper foil, the counter electrode was a platinum wire, and the reference electrode was an Ag / AgCl electrode. The electrolyte was an aqueous solution containing 10 mmol / L NiCl2, 10 mmol / L CoCl2, and 10 mol / L LiCl. The copper foil of the working electrode was cut into 1×1.5 cm pieces, and the surface impurities of the contact area between the back and the electrode clamp were removed with a scraper to construct an ohmic contact. The contact area between the working electrode and the electrolyte was left at 1×0.5 cm, and the remaining part was isolated from the electrolyte with black insulating tape to ensure the accuracy of the working area. PDADMAC with a number-average molecular weight of 200,000~350,000 was dissolved in a 1:1 (volume ratio) mixture of ethanol and deionized water, and the PDADMAC dispersion was uniformly drop-coated onto the surface of the working electrode using a pipette.

[0099] (2) Conditions favorable for selective cobalt deposition: Multiple it curve tests were performed within the voltage range of -0.70 ~ -0.74 V vs. Ag / AgCl. An additional coating of 0.05 mg / cm³ was applied to the electrode at the intermediate potential of -0.72 V vs. Ag / AgCl. 2 PDADMAC was used to further control the selective deposition of cobalt. Finally, each deposited electrode was digested and analyzed by ICP-MS to determine the cobalt and nickel content.

[0100] Table 1. Content of cobalt and nickel deposited in CuS / Cu2S / Cu and copper foil under different test conditions (the analytical solution after digestion was tested in 8 mL volumes).

[0101]

[0102] Table 1 shows partial data on the cobalt and nickel content deposited by the CuS / Cu2S / Cu catalyst and pure copper foil under different test conditions in Examples 3 and 7. For the selective deposition of nickel by the CuS / Cu2S / Cu electrode, the potential control shows that the closer to the lower the potential, the stronger the selectivity of nickel deposition, but the corresponding deposition amount will decrease. Therefore, the intermediate potential of -0.54 V was selected as the favorable potential for selective nickel deposition. After using the polymer-modified electrode in conjunction, the electrode's nickel deposition selectivity (Ni / Co) increased from 2.30 to 6.82. For the selective deposition of cobalt by the CuS / Cu2S / Cu electrode, the selectivity shows a characteristic of first increasing and then decreasing with the potential. The optimal potential for selective cobalt deposition is -0.68 V, at which point the highest selectivity for cobalt deposition is achieved. After using the polymer-modified electrode in conjunction, the electrode's cobalt deposition selectivity (Co / Ni) increased from 3.07 to 5.30. In contrast, the optimal potential for selective cobalt deposition on copper foil is -0.72 V. The CuS / Cu2S / Cu electrode achieves the highest selectivity with a potential reduction of only 0.04 V, and the deposition rate is increased by 3 to 4 times. The CuS / Cu2S / Cu catalyst can achieve significantly enhanced deposition performance at lower operating voltages.

[0103] Example 4

[0104] In a mixed electrolyte containing 100 mmol / L NiCl2, 100 mmol / L CoCl2, and 10 mol / L LiCl, the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1 was used as the working electrode. Cobalt and nickel were deposited at different potentials, and their contents were tested. Further, a PDADMAC coating was applied to its surface to control the selective deposition of cobalt and nickel, including the following steps:

[0105] (1) The electrodeposition method was performed using a three-electrode system. The working electrode was the CuS / Cu2S / Cu catalyst prepared according to the above technical solution, the counter electrode was a platinum wire, and the reference electrode was an Ag / AgCl electrode. The electrolyte was an aqueous solution containing 100 mmol / L NiCl2, 100 mmol / L CoCl2, and 10 mol / L LiCl. The working electrode CuS / Cu2S / Cu was cut into 1×1.5 cm pieces, and the surface impurities of the part in contact with the electrode clamp on the back were removed with a scraper to construct an ohmic contact. The part of the working electrode in contact with the electrolyte was left at 1×0.5 cm, and the rest was isolated from the electrolyte with black insulating tape to ensure the accuracy of the working area. PDADMAC with a number average molecular weight of 200,000~350,000 was dissolved in a 1:1 (volume ratio) mixture of ethanol and deionized water, and the PDADMAC dispersion was uniformly drop-coated onto the surface of the working electrode using a pipette.

[0106] (2) Conditions favorable for selective cobalt deposition: Multiple it curve tests were performed within the voltage range of -0.66 ~ -0.7 V vs. Ag / AgCl. An additional coating of 0.05 mg / cm³ was applied to the electrode at the intermediate potential of -0.68 V vs. Ag / AgCl. 2 PDADMAC was used to further control the selective deposition of cobalt. Finally, each deposited electrode was digested and analyzed by ICP-MS to determine the cobalt and nickel content.

[0107] In this embodiment, the electrochemical behavior of the CuS / Cu2S / Cu electrode catalyst for selective cobalt deposition was investigated after increasing the cobalt and nickel ion concentrations tenfold. The results show that the catalyst's selective deposition capability for cobalt is significantly enhanced under this environment, and the Co / Ni ratio can be increased to over 10.

[0108] Example 5

[0109] Using the copper-based catalyst CuS / Cu2S / Cu prepared in Example 1 as the working electrode, cobalt and nickel are selectively recovered from waste ternary lithium-ion battery cathode materials, including the following steps:

[0110] (1) Pretreatment steps for waste ternary lithium-ion batteries: First, the batteries are completely discharged in NaCl solution. Then, the batteries are disassembled in a fume hood to separate the positive electrode material. Next, the PVDF binder is dissolved using NMP solvent to separate the positive electrode material and the aluminum current collector. After filtration and drying, the positive electrode active material is obtained.

[0111] (2) Use 30 mL of 10 mol / L HCl to leach 4 g of collected positive electrode active material, separate the insoluble residue by filtration, and then use LiOH to adjust the pH to 3.

[0112] (3) Selective electrodeposition of cobalt was performed using CuS / Cu2S / Cu as the working electrode, with a PDADMAC (Mw=200000~350000) loading of 0.05 mg / cm³. 2 A potential of -0.68 V vs. Ag / AgCl was applied, followed by a stripping process of -0.01 V vs. Ag / AgCl to 5 mmol / L NaNO3. 10 mol / L LiCl was added to the stripping electrolyte, and the selective electrodeposition process for cobalt was repeated once more. Finally, the purity of the sample was determined using ICP-MS.

[0113] (4) After the first selective electrodeposition of cobalt, the leaching solution will form conditions favorable for the selective electrodeposition of nickel. At this time, a first selective electrodeposition of nickel is performed using CuS / Cu2S / Cu as the working electrode, with a PDADMAC (Mw=200000~350000) loading of 2 mg / cm³. 2 A potential of -0.54 V was applied to Ag / AgCl, and the purity of the samples was finally tested using ICP-MS.

[0114] (5) Repeat the above cobalt and nickel electrodeposition and adsorption-desorption processes multiple times until the desired cobalt and nickel purity and recovery rate are obtained. When the Co / Ni ratio of the leachate is too high, Co electrodeposition can be selectively performed, and when the Ni / Co ratio of the leachate is too high, Ni electrodeposition can be selectively performed. These two selective deposition processes can work in a complementary manner to achieve the best cobalt and nickel recovery effect.

[0115] The results show that when CuS / Cu2S / Cu catalyst is used as the working electrode, after two selective deposition processes of cobalt adsorption and desorption and one selective deposition process of nickel adsorption and desorption, the purity of recovered cobalt and nickel can reach about 95%, which is significantly improved compared with pure copper foil.

[0116] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based catalyst, characterized in that, Includes the following steps: a) Place the copper foil downstream of the tube furnace and the thiourea upstream of the tube furnace. Then continuously introduce inert gas into the tube furnace. After the air in the furnace is exhausted, heat up and calcine the material in the furnace to obtain copper foil with Cu2S loaded on the surface. b) Spray CuS dispersion onto the surface of the copper foil loaded with Cu2S, then place it in a tube furnace, and continuously introduce inert gas into the tube furnace. After the air in the furnace is purged, heat up and calcine the material in the furnace to obtain a copper-based catalyst.

2. The preparation method according to claim 1, characterized in that, In step a), the thickness of the copper foil is 0.2~0.3mm.

3. The preparation method according to claim 1, characterized in that, In step a), the distance between the copper foil and thiourea in the tube furnace is 6~10cm.

4. The preparation method according to claim 1, characterized in that, In step a), the flow rate of the inert gas is 100~150mL / min; the heating rate of the calcination is 1~3℃ / min, the final temperature is 350~450℃, and the holding time at the final temperature is 1~2h.

5. The preparation method according to claim 1, characterized in that, In step b), the spraying pressure is 0.2~0.4MPa; the spraying distance is 5~10cm.

6. The preparation method according to claim 1, characterized in that, In step b), the flow rate of the inert gas is 50~100mL / min; the heating rate of the calcination is 4~6℃ / min, the final temperature is 100~200℃, and the holding time at the final temperature is 2~4h.

7. A copper-based catalyst, characterized in that, The copper-based catalyst is prepared according to any one of claims 1 to 6; the copper-based catalyst comprises: copper foil, Cu2S supported on the surface of the copper foil, and CuS supported on the surface of the Cu2S.

8. The copper-based catalyst according to claim 7, characterized in that, The Cu2S is in the form of tiles, and the CuS is in the form of nanoparticles.

9. The application of the copper-based catalyst according to any one of claims 7 to 8 in the selective recovery of cobalt and nickel from waste ternary lithium-ion batteries.

10. A method for selectively recycling cobalt and nickel from waste ternary lithium-ion batteries, characterized in that, Includes the following steps: A three-electrode system was adopted, using the chlorination leachate of waste ternary lithium-ion battery cathode material as the electrolyte for electrochemical deposition, to deposit cobalt and / or nickel on the surface of the working electrode; The working electrode comprises: a copper-based catalyst according to any one of claims 7 to 8, and polydimethyldiallyl ammonium chloride supported on the surface of the copper-based catalyst.

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