Method for recycling all components of waste lithium iron phosphate battery based on light driving

Abstract

The invention provides a method for recycling all components of a waste lithium iron phosphate battery based on light driving, and belongs to the technical field of waste battery recycling. The method comprises the following steps: discharging and disassembling the waste lithium iron phosphate battery to obtain a lithium iron phosphate-copper foil positive electrode, a carbon-aluminum foil negative electrode, a diaphragm and a battery shell; the method comprises the following steps: mixing and crushing a lithium iron phosphate-copper foil positive electrode and a carbon-aluminum foil negative electrode, performing high-temperature pyrolysis on mixed powder of the positive electrode and the negative electrode of the waste lithium iron phosphate battery in inert gas, and removing a binder; and putting the remaining powder into mixed organic acid, and sequentially carrying out organic acid coordination precipitation of copper, light-driven reduction precipitation of iron, coordination precipitation of aluminum hydroxide and high-alkali heating concentration on the obtained acid leaching solution to prepare lithium phosphate. According to the method, gradient low-energy-consumption recovery of all components in the positive and negative electrode powder of the waste lithium iron phosphate battery is realized, and the industrial problem that iron and phosphorus cannot be effectively recovered and utilized in a high-valued manner and can only be piled up in an iron-phosphorus slag form is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste battery recycling, and particularly relates to a method for recycling all components of waste lithium iron phosphate batteries based on light driving. Background Art

[0002] With the rapid development of modern technology, social energy and environmental problems have become increasingly prominent, and various waste batteries have caused serious pollution to the environment. The technical demand for realizing the full resource recovery of valuable components in the positive and negative black powders of these batteries has become extremely urgent. Lithium iron phosphate batteries (LFP) are known for their high safety, long life, environmental friendliness, cost-effectiveness, and good low-temperature performance. They have a low self-discharge rate, a stable structure, are suitable for use in cold environments, and do not contain harmful heavy metals, having little impact on the environment. These characteristics have made them widely used in electric vehicles, energy storage systems, and portable electronic devices. Therefore, the recycling of waste lithium iron phosphate batteries will become a hot topic in the next 3-5 years.

[0003] At present, the recycling and reuse of waste lithium iron phosphate batteries mainly adopt hydrometallurgy and pyrometallurgy. In hydrometallurgy, valuable metals Fe and Li in waste lithium iron phosphate are first leached into the solution by inorganic strong acids, and then a large amount of oxidant is added to generate FePO 4 precipitate, and then the pH is adjusted and Na 3 PO 4 is added to generate Li 3 PO 4 . However, a large amount of acid and base materials are consumed in the processes of precipitating FePO 4 and precipitating lithium, and at the same time, a large amount of saline wastewater is generated, posing a risk of secondary pollution to the environment. Although pyrometallurgy can recover some of the metals, this process has high energy consumption, generates a large amount of harmful gases and waste residues, causes serious pollution to the environment, and it is difficult to achieve the efficient separation and recovery of elements such as lithium, iron, and phosphorus. In addition, general waste lithium iron phosphate battery recycling methods must achieve the complete and thorough separation of the current collector aluminum foil / copper foil from the positive and negative mixed powders in the pretreatment stage, which is difficult to achieve in large-scale mechanized pretreatment.

[0004] As a clean and renewable energy source, the application of light in chemical reactions has received extensive attention. Light-driven chemical reactions have the advantages of mild reaction conditions, high selectivity, and no need to add additional complex catalysts or oxidants.

[0005] Therefore, how to develop a method for recycling all components of waste lithium iron phosphate batteries by light-driven organic acid cascade, in order to achieve the efficient recovery of all components of the positive and negative mixed powders of waste lithium iron phosphate batteries, recycle the medium in the filtrate, and solve the environmental pollution and low economic benefits caused by the use of a large amount of strong acids and high-cost oxidants in the existing recycling technologies, has become a technical problem to be solved urgently. Summary of the Invention

[0006] The present invention aims to solve the above technical problems, and thus provides a method for the stepwise green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acids. The method provided by the present invention has the advantages of simple process, enabling the full-component recycling and high-value utilization of the mixed powder of the positive and negative electrodes of waste lithium iron phosphate batteries, low cost, high recovery rate, and extremely broad industrial application prospects.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for the stepwise green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acids, comprising the following steps:

[0009] (1) Separating the lithium iron phosphate - copper foil positive electrode and the carbon - aluminum foil negative electrode from the waste lithium iron phosphate battery, pulverizing them with a pulverizer, and simultaneously recovering the residual electrolyte volatilized due to temperature rise through condensation;

[0010] (2) Calcining the mixed powder of the waste lithium iron phosphate positive and negative electrodes obtained in step (1) for 3 - 10 hours under the protection of an inert gas, and the calcination temperature is 300 - 1000 °C;

[0011] (3) Adding an acid leaching solution with a certain concentration to the slurry of the mixed powder of the positive and negative electrodes obtained in step (2) for leaching phosphorus, copper, aluminum, and lithium metals; the acid leaching solution is a mixed organic acid composed of citric acid and oxalic acid;

[0012] (4) Adjusting the temperature of the acid leaching solution, the ratio and concentration of the mixed organic acids in step (3) to precipitate copper through organic acid coordination, and obtaining a filter copper compound and a carbon powder mixture;

[0013] (5) Irradiating the filtrate produced in step (4) with light for a certain time to reduce and precipitate iron through light-driven organic acids, and obtaining an organic acid iron compound that can be directly and highly valued for use in battery negative electrode materials and photocatalytic materials;

[0014] (6) After adjusting the pH value of the filtrate obtained in step (5), precipitating aluminum hydroxide through coordination;

[0015] (7) After adjusting the pH value and temperature of the filtrate obtained in step (6), adding sodium phosphate with 1 / 5 - 1 times the phosphorus content to precipitate lithium phosphate;

[0016] (8) Putting the copper compound and carbon powder mixture obtained in step (4) into a flotation cell, adding flotation reagents to float and separate the carbon powder.

[0017] Further, in step (1), the amounts of the lithium iron phosphate - copper foil positive electrode and the carbon - aluminum foil negative electrode are 1 to 100 units of waste lithium iron phosphate batteries; the pulverization time of the lithium iron phosphate - copper foil positive electrode and the carbon - aluminum foil negative electrode is 5 to 60 min, and the rotation speed is 1000 to 5000 rpm.

[0018] Further, in step (2), the inert protective gas includes any one or any combination of two of nitrogen, argon, helium, neon, krypton or xenon.

[0019] Further, in step (2), the main components and their contents in the mixed powder of the positive and negative electrodes of the waste lithium iron phosphate battery are: Li 2.2 - 3.6%, Fe 15.7 - 24.4%, Al 33.01 - 4.61%, Cu 1.78 - 6.76%, P 18.79 - 22.91%, Ti 0.01 - 0.17% (the remaining components are carbon powder, volatile electrolyte, binder and other materials, and there is no need to recycle them, and their contents are not limited here).

[0020] Further, in step (3), the liquid - solid ratio of the mixed powder of the positive and negative electrodes to the acid leaching solution is 20 - 1500 mL / g, and the acid leaching time is 20 - 1000 min.

[0021] Further, in step (4), the temperature of the acid leaching solution is adjusted to 30 - 100 °C, the weight ratio of the two mixed organic acids is adjusted to 1:100 - 100:1, and the concentration of the mixed organic acid is adjusted to 0.1 - 50 M.

[0022] Further, in step (5), the certain time of light irradiation is carried out by using a mercury lamp, a xenon lamp, an LED lamp or sunlight, the light intensity is 10 mW / cm 2 ~100 mW / cm 2 , and the light irradiation time is 1 - 1000 min.

[0023] Further, in step (6), the pH value adjustment range of the filtrate is 0.1 - 12.

[0024] Further, in step (7), the pH value adjustment range of the filtrate is 0.1 - 12, and the temperature adjustment range is 30 - 100 °C.

[0025] Further, in step (8), the dosage of the copper compound and carbon powder mixture is 2 - 100 g, and the dosage of the flotation reagent is 80 - 1000 g / t.

[0026] The beneficial effects of the present invention are as follows:

[0027] (1) The present invention provides a method for the step-by-step green recycling and utilization of all components of waste lithium iron phosphate batteries by light driving organic acids. This method has the advantages of simple process, enabling the recycling and high-value utilization of all components of the mixed positive and negative powder materials of waste lithium iron phosphate batteries, low cost, high recovery rate, and broad prospects for industrial application.

[0028] (2) In the method provided by the present invention, the filtrate containing only lithium ions is recovered by adding sodium phosphate etc. to generate lithium phosphate; the entire process uses green and environmentally friendly organic acids, and uses light energy to drive the reaction between the organic acid and the metal, without generating acidic or alkaline wastewater, greatly reducing environmental pollution and damage during the recycling process of waste lithium iron phosphate batteries and reducing carbon dioxide emissions. Description of the Drawings

[0029] Figure 1 It is the process flow chart of the present invention. Detailed Embodiments

[0030] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following describes the present invention in detail with reference to the embodiments. It should be noted that the following embodiments are only used to explain and illustrate the present invention, and are not used to limit the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content still fall within the protection scope of the present invention.

[0031] Embodiment 1

[0032] A method for the step-by-step green recycling and utilization of all components of waste lithium iron phosphate batteries by light driving organic acids, comprising the following steps:

[0033] S1. After pre-treating the waste lithium iron phosphate battery, the positive and negative powder materials of waste lithium iron phosphate are obtained. The mass percentages of the main components that can be adopted are as follows: Li 2.2%, Fe 15.7%, Al 33.01%, Cu 1.78%, P 18.79%, Ti 0.01%; (the remaining components are carbon powder, volatile electrolyte, binder material, and the sum of all components is 100%, the same below);

[0034] S2. Mix citric acid and oxalic acid in a molar ratio of 1:1 to obtain an acid leaching solution;

[0035] S3. Mix and leach the positive and negative mixed powder materials in step S1 and the acid leaching solution in step S2 to obtain a leaching solution containing phosphorus, iron, copper, aluminum and lithium;

[0036] S4. Adjust the temperature of the acid leaching solution obtained in step S3 to 30 °C, carry out organic acid coordination precipitation of copper, filter after the reaction ends, and put the filter residue into a drying oven for drying;

[0037] S5. Place the filtrate obtained in step S4 under light reaction conditions;

[0038] S6. Use an LED lamp as the light source / sunlight irradiation, with a light intensity of 20 mW / cm 2 , continuously stir during the reaction. After reacting for 2 h, stop the light irradiation and filter. Put the filter residue into a drying oven for drying; the filter residue is the organic acid-reduced precipitated iron, obtaining an iron organic acid compound that can be directly and highly valorized for use in battery anode materials and photocatalytic materials;

[0039] S7. Adjust the pH of the filtrate obtained in step S6 to 7, and filter to obtain aluminum hydroxide;

[0040] S8. Adjust the pH of the filtrate obtained in step S7 to 10, with a temperature of 90 °C, add 0.2 M sodium phosphate, and filter to obtain lithium phosphate;

[0041] S9. Put the copper compound and carbon powder mixture obtained in step S5 into a flotation cell. The dosage of the mixture is 80 g, and the dosage of the flotation reagent is 1200 g / t, and then float and separate the carbon powder.

[0042] Example 2

[0043] A method for the stepwise green recycling and utilization of all components of waste lithium iron phosphate batteries using light-driven organic acids, comprising the following steps:

[0044] S1. After pre-treating the waste lithium iron phosphate battery, obtain the positive and negative electrode powders of waste lithium iron phosphate. The mass percentages of the main components that can be used are as follows: Li 2.2%, Fe 15.7%, Al 33.01%, Cu 1.78%, P 18.79%, Ti 0.01%;

[0045] S2. Mix citric acid and oxalic acid in a molar ratio of 1:1.5 to obtain an acid leaching solution;

[0046] S3. Mix and leach the positive and negative electrode mixed powders in step S1 and the acid leaching solution in step S2 to obtain a leaching solution containing phosphorus, iron, copper, aluminum, and lithium;

[0047] S4. Adjust the temperature of the acid leaching solution obtained in step S3 to 30 °C, carry out organic acid coordination precipitation of copper. After the reaction ends, filter, and put the filter residue into a drying oven for drying;

[0048] S5. Place the filtrate obtained in step S4 under light reaction conditions;

[0049] S6. Use an LED lamp as the light source, with a light intensity of 20 mW / cm 2, continuously stir during the reaction. After 2 h of reaction, stop the light irradiation and filter. Put the filter residue into a drying oven for drying. The filter residue is the iron precipitated by the reduction of organic acid, and the iron organic acid compound that can be directly and highly valorized for use in the anode material of the battery and the photocatalytic material is obtained;

[0050] S7. Adjust the pH of the filtrate obtained in step S6 to 7, and filter to obtain aluminum hydroxide;

[0051] S8. Adjust the pH of the filtrate obtained in step S7 to 10, keep the temperature at 90 °C, add 0.2 M sodium phosphate, and filter to obtain lithium phosphate.

[0052] S9. Put the copper compound and carbon powder mixture obtained in step S5 into a flotation cell. The dosage of the mixture is 80 g, and the dosage of the flotation reagent is 600 g / t, and then float to separate the carbon powder.

[0053] Example 3

[0054] A method for the stepwise green recycling of all components of waste lithium iron phosphate batteries using light-driven organic acids includes the following steps:

[0055] S1. After the waste lithium iron phosphate battery is pretreated, the positive and negative electrode powders of waste lithium iron phosphate are obtained. The mass percentages of the main components that can be used are as follows: Li 2.2%, Fe 15.7%, Al 33.01%, Cu 1.78%, P 18.79%, Ti 0.01%;

[0056] S2. Mix citric acid and oxalic acid in a molar ratio of 1:1.5 to obtain an acid leaching solution;

[0057] S3. Mix and leach the positive and negative electrode mixed powders in step S1 and the acid leaching solution in step S2 to obtain a leaching solution containing phosphorus, iron, copper, aluminum and lithium;

[0058] S4. Adjust the temperature of the acid leaching solution obtained in step S3 to 30 °C, carry out the coordination precipitation of copper with organic acid. After the reaction is completed, filter, and put the filter residue into a drying oven for drying;

[0059] S5. Place the filtrate obtained in step S4 under the conditions of a light reaction;

[0060] S6. Use an LED lamp as the light source, and the light intensity is 25 mW / cm 2 , continuously stir during the reaction. After 2 h of reaction, stop the light irradiation and filter. Put the filter residue into a drying oven for drying. The filter residue is the iron precipitated by the reduction of organic acid, and the iron organic acid compound that can be directly and highly valorized for use in the anode material of the battery and the photocatalytic material is obtained;

[0061] S7. Adjust the pH of the filtrate obtained in step S6 to 7, and filter to obtain aluminum hydroxide;

[0062] S8. Adjust the pH of the filtrate obtained in step S7 to 10 and the temperature to 90 °C, add 0.2 M sodium phosphate, and filter to obtain lithium phosphate.

[0063] S9. Put the copper compound and carbon powder mixture obtained in step S5 into a flotation cell. The dosage of the mixture is 80 g, and the dosage of the flotation reagent is 600 g / t, and then float and separate the carbon powder.

[0064] Example 4

[0065] A method for the step-by-step green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acids includes the following steps:

[0066] S1. After the waste lithium iron phosphate battery is pretreated, the positive and negative electrode powders of waste lithium iron phosphate are obtained. The mass percentages of the main components that can be used are as follows: Li 2.2%, Fe 15.7%, Al 33.01%, Cu 1.78%, P 18.79%, Ti 0.01%.

[0067] S2. Mix citric acid and oxalic acid in a molar ratio of 1:1.5 to obtain an acid leaching solution.

[0068] S3. Mix and leach the positive and negative electrode mixed powders in step S1 and the acid leaching solution in step S2 to obtain a leaching solution containing phosphorus, iron, copper, aluminum and lithium.

[0069] S4. Adjust the temperature of the acid leaching solution obtained in step S3 to 30 °C, carry out organic acid coordination precipitation of copper, filter after the reaction ends, and put the filter residue into a drying oven for drying.

[0070] S5. Place the filtrate obtained in step S4 under light reaction conditions.

[0071] S6. Use an LED lamp as the light source, with a light intensity of 25 mW / cm 2 , continuously stir during the reaction. After reacting for 2 h, stop the light irradiation and filter, and put the filter residue into a drying oven for drying. The filter residue is the organic acid-reduced precipitation iron, and an organic acid iron compound that can be directly and highly valued for use in battery negative electrode materials and photocatalytic materials is obtained.

[0072] S7. Adjust the pH of the filtrate obtained in step S6 to 7, and filter to obtain aluminum hydroxide.

[0073] S8. Adjust the pH of the filtrate obtained in step S7 to 10.5, the temperature to 90 °C, add 0.2 M sodium phosphate, and filter to obtain lithium phosphate.

[0074] S9. Put the copper compound and carbon powder mixture obtained in step S5 into a flotation cell. The dosage of the mixture is 80 g, and the dosage of the flotation reagent is 600 g / t, and then float and separate the carbon powder.

[0075] Comparative Example 1

[0076] Comparing Comparative Example 1 with Example 1, the only difference is that the pH of the filtrate obtained in step S8 of Comparative Example 1 is adjusted to 7, and other conditions are exactly the same.

[0077] Comparative Example 2

[0078] Comparing Comparative Example 2 with Example 2, the only difference is that the dosage of the flotation reagent in step S9 of Comparative Example 2 is 1000 g / t, and other conditions are exactly the same.

[0079] Comparative Example 3

[0080] Comparing Comparative Example 3 with Example 1, the only difference is that the mixed organic acid in Comparative Example 3 is salicylic acid and benzoic acid, and other conditions are exactly the same.

[0081] Comparative Example 4

[0082] Comparing Comparative Example 3 with Example 2, the only difference is that the mixed organic acid in Comparative Example 4 is formic acid and glutamic acid, and other conditions are exactly the same.

[0083] Comparative Example 5

[0084] Comparing Comparative Example 5 with Example 3, the only difference is that a mercury lamp is used as the light source in Comparative Example 5, and other conditions are exactly the same.

[0085] Test Example 1

[0086] The atomic absorption spectrometry was used to detect the recovery rates of phosphorus, iron, copper, aluminum and lithium in the leachates and leach residues obtained in Examples 1-3 and Comparative Examples 1-5 of the present invention respectively, and the results were recorded as shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] According to Table 1, compared with the recovery rates of phosphorus, iron, copper, aluminum and lithium obtained in Comparative Examples 1-5, the recovery rates of the examples are all improved.

[0091] Thus, it can be seen that the method of the present invention can effectively improve the recovery rate of each component. Recycling the waste lithium iron phosphate battery by using the method of the present invention can significantly improve the recovery rate of each component, and the effect is remarkable.

[0092] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for recycling all components of waste lithium iron phosphate batteries using light-driven organic acid cascade green recycling, characterized in that: The steps include: (1) Separating the lithium iron phosphate-copper foil positive electrode and the carbon-aluminum foil negative electrode from the waste lithium iron phosphate battery, crushing them with a crusher, and recovering the residual electrolyte volatilized due to temperature increase by condensation; (2) roasting the waste lithium iron phosphate positive and negative electrode mixed powder obtained in step (1) under the protection of inert gas for 3 to 10 hours at a roasting temperature of 300 to 1000° C.; (3) adding an acid leaching solution of a certain concentration to the positive and negative electrode mixed powder slurry obtained in step (2) to leach phosphorus, copper, aluminum and lithium metals; the acid leaching solution is a mixed organic acid composed of citric acid and oxalic acid; (4) adjusting the temperature of the acid leaching solution in step (3), the ratio and concentration of the mixed organic acid, and performing organic acid coordination precipitation of copper to obtain a mixture of a copper filtration compound and carbon powder; (5) irradiating the filtrate produced in step (4) with light for a certain period of time to perform light-driven organic acid reduction to precipitate iron, thereby obtaining an organic acid iron compound that can be directly used as a negative electrode material for batteries and a photocatalytic material; (6) adjusting the pH value of the filtrate obtained in step (5) to precipitate aluminum hydroxide; (7) adjusting the pH value and temperature of the filtrate obtained in step (6), adding sodium phosphate having a phosphorus content of 1 / 5 to 1 times, and precipitating lithium phosphate; (8) The copper compound and carbon powder mixture obtained in step (4) is placed in a flotation tank, and a flotation agent is added to separate the carbon powder by flotation.

2. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: In step (1), the amount of the lithium iron phosphate-copper foil positive electrode and the carbon-aluminum foil negative electrode is 1 to 100 units of waste lithium iron phosphate batteries; the crushing time of the lithium iron phosphate-copper foil positive electrode and the carbon-aluminum foil negative electrode is 5 to 60 minutes, and the rotation speed is 1000 to 5000 rpm.

3. The method for green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade according to claim 1, characterized in that: In step (2), the inert protective gas includes any one of nitrogen, argon, helium, neon, krypton or xenon, or a combination of any two of them.

4. The method for green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade according to claim 1, characterized in that: In step (2), the main components and contents of the mixed positive and negative electrode powders of the waste lithium iron phosphate battery are: Li 2.2-3.6%, Fe 15.7-24.4%, Al 33.01-4.61%, Cu 1.78-6.76%, P18.79-22.91%, and Ti 0.01-0.17%.

5. The method for green recycling of all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade according to claim 1, characterized in that: In step (3), the liquid-to-solid ratio of the positive and negative electrode mixed powders to the acid leaching solution is 20 to 1500 mL / g, and the acid leaching time is 20 to 1000 min.

6. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: In step (4), the temperature of the acid leaching solution is adjusted to 30-100° C., the weight ratio of the two mixed organic acids is adjusted to 1:100-100:1, and the concentration of the mixed organic acid is adjusted to 0.1-50M.

7. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: In step (5), the illumination for a certain period of time is performed using mercury lamp, xenon lamp, LED lamp or sunlight, and the illumination intensity is 10mW / cm 2 ~100mW / cm 2 , the illumination time is 1 to 1000 minutes.

8. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: The pH value of the filtrate in step (6) is adjusted in the range of 0.1 to 12.

9. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: The pH value of the filtrate in step (7) is adjusted in the range of 0.1 to 12, and the temperature is adjusted in the range of 30 to 100°C.

10. The method for recycling all components of waste lithium iron phosphate batteries by using light-driven organic acid cascade green recycling according to claim 1, characterized in that: In step (8), the dosage of the copper compound and carbon powder mixture is 2 to 100 g, and the dosage of the flotation agent is 80 to 1000 g / t.

Images