A method for spontaneously recycling waste lithium batteries through metal electrical contact

Abstract

The present invention belongs to the field of comprehensive utilization of resources, and particularly relates to a method for spontaneously recycling waste lithium batteries through metal electrical contact, comprising the following steps: after short-circuit discharging and disassembling the waste lithium batteries, the positive electrode active material and the current collector are obtained, and the positive electrode active material is kept in electrical contact with a metal, where the metal is the current collector metal of the waste lithium battery or other metals with a standard electrode potential < 1.51 V. The metal in electrical contact with the positive electrode active material and the positive electrode active material are immersed in an electrolyte solution to undergo an oxidation-reduction reaction, and after leaching out lithium ions and transition metal ions, a metal-enriched solution is obtained; a precipitant generated in-situ during the leaching process or other additional precipitants are used to precipitate lithium ions and transition metal ions respectively. The method of the present invention has a simple process, uses the potential difference between the metal and the transition metal as the driving force, does not rely on high temperature and strong acids or alkalis, has strong operability, low cost, low GHG emissions, and the leaching efficiency of each metal is close to 100%.

Description

Technical Field

[0001] The present invention belongs to the field of comprehensive utilization of resources, and particularly relates to a method for spontaneously recycling waste lithium batteries through metal electrical contact. Background Art

[0002] Lithium-ion batteries (LIBs) are widely used in a variety of modern devices, including mobile phones, portable electronic devices, and computers, etc. Improper disposal of waste batteries will lead to environmental pollution and the loss of a large amount of non-renewable resources. From an economic perspective, lithium, cobalt, nickel, and manganese in waste batteries are all expensive metal resources. Therefore, recycling waste lithium batteries is of great significance.

[0003] Pyrometallurgy and hydrometallurgy are the most commonly used recycling methods in industry at present. Pyrometallurgy is widely used in industry due to its convenient operation, but the pyrometallurgical process requires extremely high temperatures. First, it needs to be pretreated at 550 °C for 500 minutes, and then calcined with graphite at a temperature above 1000 °C for 30 minutes. This method will result in high energy consumption and carbon emissions. Some researchers have found that the pyrometallurgical recycling temperature can be reduced by adding salt for co-roasting. However, since the pyrometallurgical recycling product is an alloy and lithium cannot be recycled, most of the current research recycling methods are hydrometallurgy. Hydrometallurgy is to dissolve waste battery powder with strong acids and alkalis, and then use chemical precipitants to precipitate transition metal ions. The recovery rate of hydrometallurgy is relatively high, and more than 90% of lithium and other metals can be recovered. For hydrometallurgy, it has been reported that using organic acids (such as citric acid and acetic acid, etc.) instead of concentrated inorganic acids can reduce environmental damage. Ionic liquids and deep eutectic solvents have high leaching efficiency and recyclability, and have also been studied for recycling lithium-ion batteries.

[0004] However, these methods cannot avoid their inherent limitations, including high energy consumption and greenhouse gas (GHG) emissions. These disadvantages not only cause environmental pollution but also increase the cost of the recycling process. Recycling one ton of waste lithium-ion batteries through pyrometallurgy requires an energy input of about 3.9×10 5 MJ and produces approximately 1311 kg of carbon dioxide. Hydrometallurgy avoids the need for high temperatures, but mechanical separation of aluminum foil from the positive electrode active material is required during the pretreatment process, which also requires some energy consumption. During the process of leaching valuable metal elements, various chemicals are used, including concentrated sulfuric acid, concentrated nitric acid, and hydrogen peroxide. Subsequently, chemical precipitants, such as sodium carbonate, are required for the precipitation step. The use of these chemicals results in a large amount of greenhouse gas and toxic gas emissions. Therefore, there is an urgent need to develop an environmentally friendly recycling method for waste LIBs, which has the characteristics of low energy consumption, reduced GHG emissions, and less chemical use. Summary of the Invention

[0005] To solve the problems of high energy consumption, high carbon emissions, and the formation of a large amount of waste acid and wastewater caused by the current reliance on high-temperature smelting and acid leaching (alkali leaching) to recycle lithium batteries, the present invention provides a method for spontaneously recycling waste lithium batteries through metal electrical contact. Through the potential difference formed between the positive electrode active material of the waste battery and the metal, electrons are transferred to the positive electrode material in the electrolyte solution. After the transition metal in the positive electrode material in the high valence state receives the electrons, reduction occurs, and hydrogen-lithium exchange occurs in the solution while lithium and other transition metals are leached. The transition metal ions and Li + precipitate. After the precipitate is filtered, the electrolyte solution can be reused. This method uses the potential difference as the driving force for leaching the positive electrode active material, has a simple process, strong operability, low cost, low GHG emissions, and the leaching efficiency of each metal is close to 100%.

[0006] The technical solution provided by the present invention is as follows:

[0007] A method for spontaneously recycling waste lithium batteries through metal electrical contact, comprising the following steps: After short-circuit discharging and disassembling the waste lithium batteries, the positive electrode active material and the current collector are obtained, and the positive electrode active material is kept in electrical contact with the metal. The metal is the current collector metal of the waste lithium battery or other metals with a standard electrode potential < 1.51 V. The metal kept in electrical contact with the positive electrode active material and the positive electrode active material are immersed in the electrolyte solution to undergo an oxidation-reduction reaction, and after leaching lithium ions and transition metal ions, a metal-enriched solution is obtained; Using the precipitant generated in-situ during the leaching process or adding other precipitants separately to precipitate lithium ions and transition metal ions respectively.

[0008] Further, the method for short-circuit discharging the waste lithium batteries includes: soaking the waste lithium batteries in a salt solution and discharging until the termination voltage is 0.5 - 1.5 V; The salt solution is an NaCl solution, and the concentration of the salt solution is 4 - 6 wt%.

[0009] Further, the metal is any one or more of aluminum, copper, iron, zinc, magnesium, titanium, chromium, vanadium, nickel, cobalt, and manganese.

[0010] Further, the electrical contact method includes at least one of stirring, ultrasonic, and ball milling.

[0011] Further, the waste lithium batteries include at least one of lithium manganese oxide, lithium cobalt oxide, nickel-aluminum-cobalt lithium oxide, and nickel-manganese-cobalt lithium batteries.

[0012] Further, the solute of the electrolyte solution is at least one of soluble gas, acid, base, and salt, and the inlet pressure of the soluble gas is 0.1 - 4 Mpa. Preferably, the soluble gas introduced is CO 2 , NO 2 , SO2 。

[0013] Furthermore, the in-situ generated precipitant includes CO 2 After being used as the electrolyte solution, CO is in-situ generated during the reaction process 3 2- , or OH in-situ generated when an alkaline electrolyte solution is used - . The in-situ generated precipitant reacts with transition metal ions during the leaching process to precipitate the transition metal ions

[0014] Furthermore, during the precipitation process, the pH is adjusted to be between 10 and 14 to precipitate the transition metal ions. After filtering the transition metal precipitate, carbonate or phosphate is added to precipitate lithium ions

[0015] Furthermore, the molar ratio of the cathode active material to the metal is 0.1 - 3:1

[0016] Furthermore, the reaction temperature for the redox reaction when the metal and the cathode active material maintaining electrical contact are immersed in the electrolyte solution is 25 - 200 °C, and the reaction time is 1 - 50 hours. Preferably, the reaction temperature is 50 - 80 °C

[0017] Beneficial effects

[0018] This method utilizes the potential difference between the positive electrode current collector and the positive electrode material of waste lithium batteries to spontaneously reduce the positive electrode material of waste lithium batteries. Only an electrolyte solution is required as an ion transport medium to achieve the leaching of metals in waste lithium batteries, avoiding the use of a large amount of strong acids, strong alkalis, and reducing agents in traditional wet methods. It also does not require high-temperature smelting like pyrometallurgy. The operation is simple, and at the same time, the complicated pretreatment process is avoided. The metal current collector that needs to be removed through various means in general recycling methods is fully utilized, and the electrolyte solution can be reused, enabling the method described in the present invention to generate substantial profits while avoiding high carbon emissions. The method described in the present invention converts the harmful corrosion of metals into an effective electrochemical pathway for recycling lithium-ion batteries. This method is applicable to almost all commercial positive electrode systems, such as layered LCO, spinel LMO, and ternary materials, and the recovery rates of lithium and transition metals are close to 100%. In Example 1, carbon dioxide and water were used as leaching agents and precipitating agents, and lithium salts and transition metal salts were successfully leached and precipitated without adding additional chemicals. Compared with the 1311 kg of carbon dioxide emitted per ton of waste batteries recycled by traditional pyrometallurgy and 1843 kg of carbon dioxide emitted per ton of waste batteries recycled by wet metallurgy, using the method of the present invention to recycle one ton of waste batteries can absorb 236 kg of carbon dioxide. Since the method of the present invention has simple steps, can avoid the consumption of chemical reagents, and does not require high temperature, the cost is very low. Currently, due to the significant decline in the prices of lithium salts and cobalt salts, pyrometallurgy and wet metallurgy can no longer achieve profitability, but this method can still achieve a profit of 9000 yuan per ton. Description of the Drawings

[0019] Figure 1 It is the lithium and cobalt leaching efficiency curve of lithium cobalt oxide in carbonic acid solution in contact with aluminum for 32 hours in Example 1;

[0020] Figure 2 It is the X-ray diffraction peak intensity curve of the lithium carbonate precipitate collected after the reaction in Example 1;

[0021] Figure 3 It is the X-ray diffraction peak intensity curve of the cobalt carbonate precipitate collected after the reaction in Example 1;

[0022] Figure 4 It is the lithium and cobalt leaching efficiency curve of lithium cobalt oxide in sulfurous acid solution in contact with aluminum for 20 hours in Example 2;

[0023] Figure 5 It is the scanning electron microscope images of the lithium cobalt oxide electrode before and after the reaction in Example 2;

[0024] Figure 6 It is the lithium, cobalt, nickel, and manganese leaching efficiency curve of lithium nickel manganese cobalt oxide (NMC111) in ammonium acetate solution in contact with aluminum for 48 hours in Example 3;

[0025] Figure 7SEM images of lithium nickel manganese cobalt oxide (NMC111) before and after the reaction in Example 3;

[0026] Figure 8 Leaching efficiency curves of lithium and manganese for lithium manganate reacting with iron in ammonium chloride solution for 12 hours in Example 4;

[0027] Figure 9 Comparison of metal ion leaching efficiency with and without current collector in Comparative Example 1 and Example 1;

[0028] Figure 10 Comparison of leaching efficiency between Comparative Example 3 and Example 4 with and without metallic electrical contact with iron;

[0029] Figure 11 Comparison of implementation steps between traditional pyrometallurgy and hydrometallurgy and Example 1;

[0030] Figure 12 Cost comparison between traditional pyrometallurgy and hydrometallurgy and Example 1;

[0031] Figure 13 Comparison of carbon dioxide emissions caused by traditional pyrometallurgy and hydrometallurgy and Example 1. Detailed implementation manners

[0032] To more clearly illustrate the technical solutions of the present invention, the present invention will be further described below; Obviously, only some of the embodiments are described below. For those of ordinary skill in the art, without creative efforts, the technical solutions described in the present invention can also be applied to other similar scenarios according to these; To more clearly illustrate the technical solutions of the present invention, the technical solutions of the present invention will be further described in detail below.

[0033] Example 1

[0034] Spontaneous recovery of lithium cobalt oxide is achieved by electrical contact between an aluminum current collector and a lithium cobalt oxide electrode material in a carbonic acid solution:

[0035] (1) Soak the used lithium manganate battery in a 5wt% NaCl solution and discharge it to a voltage of 1V. Since the current collector of the lithium battery is aluminum foil, the lithium cobalt oxide positive electrode sheet containing the current collector aluminum is obtained after disassembly, and 1 - 2 g of the sheet is taken;

[0036] (2) Place the lithium cobalt oxide positive electrode sheet containing the current collector aluminum obtained in step (1) in a reaction kettle, and add 50 mL of distilled water to the reaction kettle;

[0037] (3) Introduce 2 Mpa of carbon dioxide into the reaction kettle in step (2);

[0038] (4) Set the temperature of the reaction kettle in step (3) to 50°C and react for 32 hours;

[0039] (5) Evaporate and concentrate the solution in step (4) at 60 °C. After discharging the excess carbon dioxide in the solution, the pH rises to about 6.1.

[0040] (6) Filter the solid precipitate in step 5, and the precipitate contains Al 3+ Al(OH) formed due to pH 3 ;

[0041] (7) Continue to evaporate the aqueous solution in step (6) until it is completely dried to obtain a mixture of lithium carbonate and cobalt carbonate, and separate it using the magnetism of cobalt carbonate.

[0042] The leaching rates of lithium and cobalt in lithium cobaltate are characterized by an inductively coupled plasma optical emission spectrometer (ICP-OES), and the collected products are characterized by X-ray diffraction (XRD).

[0043] The lithium and cobalt leaching efficiency curve of lithium cobaltate in contact with aluminum in carbonic acid solution for 32 hours is as Figure 1 shown, indicating that the lithium leaching efficiency reaches 100% and the cobalt leaching efficiency reaches 96%; the X-ray diffraction peak intensity curves of the lithium carbonate and cobalt carbonate precipitates collected after the reaction are as Figure 2 and 3 shown, which are completely consistent with the characteristic peaks of lithium carbonate and cobalt carbonate, and the peak shapes are sharp, indicating that the components of the precipitated cobalt carbonate and lithium carbonate are pure, with good crystallinity and no obvious impurities; among them, Li 2 C0 3 -PDF#22-1141 refers to the standard card of lithium carbonate, and CoCO 3 -PDF#11-0692 refers to the standard card of cobalt carbonate.

[0044] Example 2

[0045] Spontaneous recovery of lithium cobaltate is achieved by electrical contact between an aluminum current collector and a lithium cobaltate electrode material in sulfurous acid solution:

[0046] (1) Immerse the waste lithium cobaltate battery in a 5 wt% NaCl solution and discharge it to a voltage of 1 V. Since the current collector of the lithium battery is aluminum foil, the lithium cobaltate positive electrode sheet containing the current collector aluminum is obtained after disassembly, and 1-2 g of the sheet is taken.

[0047] (2) Place the lithium cobaltate positive electrode sheet containing the current collector aluminum obtained in step (1) in a reaction kettle, and add 50 mL of distilled water to the reaction kettle.

[0048] (3) Introduce sulfur dioxide at 0.5 Mpa into the reaction kettle in step (2).

[0049] (4) Set the temperature of the reactor in step (3) to 50 °C and react for 20 hours;

[0050] (5) Evaporate and concentrate the solution in step (4) at 60 °C. After discharging the excess sulfur dioxide in the solution, the pH rises to about 6.5;

[0051] (6) Filter the solid precipitate in step (5), where the precipitate contains Al 3+ Al(OH) formed due to pH 3 ;

[0052] (7) First add NaOH to the metal-enriched solution in step (6) to adjust the pH to 10 - 14, so that the transition metals form hydroxide precipitates and are filtered. Then add carbonate to precipitate Li + as Li 2 CO 3 .

[0053] The leaching rates of Li + , Co 2+ in lithium cobaltate are characterized by ICP. The surface of the LCO positive electrode sheet before and after the reaction is characterized by scanning electron microscopy (SEM). The lithium and cobalt leaching efficiency curve of lithium cobaltate in contact with aluminum in sulfurous acid solution for 20 hours is as Figure 4 shown, indicating that after 20 hours of leaching, the recovery rates of Li + and Co 2+ both reach 100%. The SEM observation of the electrode sheets before and after the reaction is as Figure 5 shown. It is found that before the reaction, the LCO particles are evenly distributed on the surface of the electrode sheet, and the carbon black tightly surrounds the LCO particles. After the reaction, the LCO particles on the electrode sheet disappear, and pits appear at the positions where the particles were originally located, proving that the LCO has been completely leached.

[0054] Example 3

[0055] Spontaneous recovery of lithium nickel manganese cobaltate (NMC111) is achieved by the electrical contact of an aluminum current collector with a lithium nickel manganese cobaltate (NMC111) electrode material in an ammonium acetate solution:

[0056] (1) Immerse the used lithium nickel manganese cobaltate (NMC111) battery in a 5wt% NaCl solution and discharge it to a voltage of 1V. Since the current collector of the lithium battery is aluminum foil, after disassembling, a positive electrode sheet of lithium nickel manganate containing the current collector aluminum is obtained, and 1 - 2 g of the electrode sheet is taken;

[0057] (2) Place the positive electrode sheet of lithium nickel manganese cobaltate containing the current collector aluminum obtained in step (1) in a reactor, and add 50 mL of distilled water to the reactor;

[0058] (3) Add 0.5 g of ammonium acetate to the reaction kettle in step (2), stir to dissolve, and the pH = 6.0;

[0059] (4) Set the temperature of the reaction kettle in step (3) to 50 °C and react for 48 hours;

[0060] (5) For the Al in step (4) 3+ The Al(OH) formed due to pH 3 precipitate, filter it to obtain the metal enriched solution;

[0061] (7) First add NaOH to the metal enriched solution in step (6) to adjust the pH to 10 - 14, filter after the transition metals form hydroxide coprecipitates, and then add carbonate to precipitate Li + as Li 2 CO 3 .

[0062] The leaching rates of lithium, nickel, manganese, and cobalt in lithium nickel manganese cobaltate are characterized by ICP. The leaching efficiency curves of lithium, cobalt, nickel, and manganese in lithium nickel manganese cobaltate reacting with aluminum in ammonium acetate solution for 48 hours are as Figure 6 shown, indicating that the leaching rates of lithium, nickel, manganese, and cobalt metal elements all reach 100%. The surface of the NMC111 positive electrode sheet before and after the reaction is characterized by scanning electron microscopy (SEM). As Figure 7 shown, it is found that the NMC111 particles are evenly distributed on the surface of the electrode sheet before the reaction, and the particles on the surface of the electrode sheet disappear after the reaction, and pits appear at the positions where the original particles were located, proving that the NMC111 has been completely leached.

[0063] Example 4

[0064] Spontaneously recover lithium manganate by the electrical contact of metallic iron with lithium manganate in ammonium chloride solution:

[0065] (1) Immerse the used lithium manganate battery in 5wt% NaCl solution and discharge it to a voltage of 1V. After disassembling, obtain the lithium manganate electrode sheet. After removing the current collector and pulverizing, obtain the lithium manganate black powder. Mix the lithium manganate black powder and iron powder in a ratio of 1:3, and take 1 - 2 g of the mixed powder;

[0066] (2) Place the mixed powder obtained in step (1) in a beaker, and add 50 mL of distilled water to the reaction kettle;

[0067] (3) Add 0.5 g of ammonium chloride solid to the reaction kettle in step (2) and stir to dissolve;

[0068] (4) Set the temperature in step (3) to 50 °C, stir and react for 12 hours, filter out the solid impurities to obtain the metal enriched solution;

[0069] (5) In step (4), NaOH is first added to the metal-enriched solution to adjust the pH to 10 - 14, so that the transition metals form a common hydroxide precipitate and are then filtered. Then carbonate is added to precipitate Li + as Li 2 CO 3 .

[0070] The leaching rates of lithium and manganese in lithium manganate are characterized by ICP. The lithium and manganese leaching efficiency curves of lithium manganate in ammonium chloride solution in contact reaction with iron for 12 hours are as Figure 8 shown, indicating that the lithium leaching efficiency is relatively high, and it has been completely leached in 8 hours, while the manganese leaching rate also reaches 100% after 12 hours.

[0071] Comparative Example 1

[0072] Used lithium cobalt oxide waste is leached. Other steps are the same as in Example 1, and the only difference is that the current collector aluminum of the waste battery is removed. Figure 9 For the comparison of lithium and cobalt leaching efficiency with and without the current collector in the leaching for 32 hours, in the case of no current collector, after 32 hours of leaching, only 2.215% of lithium and 0.445% of cobalt are leached. The difference between Example 1 and Comparative Example 1 lies in the presence or absence of the current collector, which leads to the difference in the leaching rate of valuable metal elements. The role of the current collector is to provide electrons for the transition metals of the waste battery, promoting their reduction leaching. At the same time, the reduction of high-valent transition metals promotes the hydrogen-lithium exchange process. Therefore, under the condition of the presence of the current collector, the lithium and cobalt leaching efficiency is close to 100%, while in the case of no current collector, the leaching efficiency is very low.

[0073] Comparative Example 2

[0074] Used lithium manganate waste is leached. Other steps are the same as in Example 4, and the only difference is that the black powder of waste lithium manganate is no longer mixed with iron powder, and the black powder is directly immersed in ammonium chloride solution for reaction for 12 hours. Figure 10 For the comparison of the leaching effects with and without electrical contact with iron after 12 hours of leaching, in the case of no iron, after 12 hours of leaching, only 1.07% of lithium and 0.53% of manganese are leached. The difference between Example 4 and Comparative Example 3 lies in whether there is electrical contact with iron, which leads to the difference in the leaching rate of valuable metal elements. The role of iron is to provide electrons for the transition metal manganese of the waste battery, promoting its reduction leaching.

[0075] Comparative Example 3

[0076] Figure 11The conventional method is compared with the specific steps of Example 1. The conventional method is relatively complicated. The present method uses the potential difference between the aluminum foil of the waste battery and the lithium transition metal oxide as the driving force. No additional reducing agent is required, and the use of irritating chemicals is avoided. High-temperature smelting is not required. Water and carbon dioxide act as leaching agents and precipitants at the same time, and the target products of lithium carbonate and cobalt carbonate are obtained in one step.

[0077] Comparative Example 4

[0078] Figure 12 The cost of recycling waste batteries by traditional methods (fire and wet methods) is compared with that of recycling waste batteries by the method in Example 1. The traditional method requires high temperature or strong acid to drive the leaching of valuable metal elements, and then precipitate metal ions by salt. The operation process is cumbersome, and the cost includes waste batteries, chemicals, electricity, and some other costs (this part of the cost includes transportation, storage, management, etc., and this part of the cost of all methods is considered to be the same). Compared with the traditional wet method and fire method, this work does not require high-temperature smelting or chemicals to drive metal ion leaching. Relying on the current collector aluminum to provide electrons as a driving force, spontaneous recovery can be achieved in an environment of water and carbon dioxide. Carbon dioxide also acts as a precipitant, so no additional chemical reagents are required for precipitation, so the cost is low and the economic benefit is high.

[0079] Comparative Example 5

[0080] Figure 13 The carbon emissions of waste batteries recovered by traditional methods (pyrometallurgy and hydrometallurgy) are compared with those of waste batteries recovered by the method in Example 1. The traditional method requires high temperature or strong acid to drive the leaching of valuable metal elements, and then salt to precipitate metal ions. The energy consumption and the use of chemicals are converted into corresponding carbon dioxide emissions. Compared with the traditional hydrometallurgy and pyrometallurgy, this work does not require high-temperature smelting or chemicals to drive the leaching of metal ions. Relying on the current collector aluminum to provide electrons as a driving force, spontaneous recovery can be achieved in a water and carbon dioxide environment. Using carbon dioxide as a precipitant not only does not emit carbon dioxide, but also achieves negative carbon recovery.

Claims

1. A method for spontaneously recycling waste lithium batteries through metal electrical contacts, characterized in that: The method comprises the following steps: immersing a waste lithium battery in a NaCl solution with a solubility of 5wt%, discharging the battery to a voltage of 1V, and disassembling the battery to obtain a lithium cobalt oxide positive electrode sheet containing current collector aluminum; placing the lithium cobalt oxide positive electrode sheet containing current collector aluminum in a reactor, adding distilled water into the reactor, introducing 2Mpa of carbon dioxide into the reactor, setting the temperature of the reactor to 50°C, and reacting for 32 hours; evaporating and concentrating the reacted solution at 60°C, discharging excess carbon dioxide in the solution, raising the pH to 6.1, and filtering the solid precipitate in the solution, wherein the solid precipitate contains Al 3+ Al(OH)3 is formed due to pH; the solution is evaporated continuously until it is completely dried to obtain a mixture of lithium carbonate and cobalt carbonate, and the lithium carbonate and cobalt carbonate are separated by utilizing the magnetic properties of cobalt carbonate.

Images