Method and system for recycling lithium battery material under assistance of photocatalysis

Abstract

The invention discloses a method and a system for recycling a lithium battery material under the assistance of photocatalysis. The method comprises the following steps: (1) mixing lithium battery black powder with malic acid and hydrogen peroxide, and adding a titanium dioxide / graphene composite photocatalyst; (2) carrying out a leaching reaction under ultraviolet irradiation, and releasing metal ions through a photocatalysis-chemical synergistic effect; and (3) separating Fe / Al, Co / Ni and Li components step by step by adopting a multi-stage light-operated gradient precipitation method. The method disclosed by the invention is green and efficient, reduces the dosage of strong acid and oxidizing agent, can recycle the photocatalyst, and has no secondary pollution. According to the method, an ultraviolet light catalysis method is adopted to enhance the leaching efficiency and promote effective precipitation of metal ions, and the energy consumption in the recovery process can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery material recycling, and in particular to a method and system for photocatalytically assisted recycling of lithium battery materials. Background Art

[0002] As a core component of new energy vehicles and energy storage systems, the market for lithium-ion batteries is experiencing explosive growth. By 2023, China's total lithium battery production will exceed 940GWh, a year-on-year increase of 25%, with the industry's total output value exceeding 1.4 trillion yuan. However, due to issues such as degradation of the positive and negative electrode crystal structures, the electrochemical performance of lithium batteries gradually declines over time, leading to their retirement and disposal. The current surge in lithium battery production has been accompanied by a year-on-year increase in the number of used batteries. It is estimated that by 2030, my country's annual production of retired power batteries will exceed 1 million tons. In contrast to the large amount of used lithium batteries, lithium resources are relatively scarce in the Earth's crust and are primarily distributed in a few countries. This leads to geopolitical risks and price volatility in the lithium supply chain. With the rapid expansion of the new energy vehicle and energy storage industries, market demand for lithium is growing exponentially, far exceeding current lithium supply capacity. Therefore, developing efficient lithium battery recycling technologies and enabling the recycling of lithium resources is crucial to ensuring national energy security and economic development.

[0003] Furthermore, used lithium batteries contain significant amounts of heavy metals (such as cobalt, nickel, and manganese) and toxic substances. Improper disposal can cause serious environmental pollution. For example, leaked electrolyte from lithium batteries can contaminate soil and groundwater, and heavy metal ions can enter the food chain, causing irreversible damage to ecosystems and human health. With the rapid increase in the number of used lithium batteries, the lack of a comprehensive recycling system will create significant environmental pressure. Conversely, heavy metals such as nickel, cobalt, and manganese, due to their rarity, have high market value, and their recycling can bring significant economic benefits. In response to this, an increasing number of countries and regions are introducing policies and regulations to encourage and regulate the development of the lithium battery recycling industry. These policies not only provide financial support and technical guidance, but also strengthen oversight of battery manufacturers and recycling companies, promoting the sustainable development of the industry as a whole. Therefore, developing efficient and environmentally friendly lithium battery recycling technologies is urgently needed to protect the environment and achieve sustainable development.

[0004] The current mainstream lithium battery recycling process is primarily wet-process recycling. For example, the recycled batteries typically undergo electrolyte solution discharge, drum crushing, screening, drying, grinding into powder, high-temperature pyrolysis, and airflow separation to produce positive and negative electrode black powder. Generally speaking, the presence of rare metals such as nickel, cobalt, and manganese in the positive electrode black powder of ternary batteries provides extremely high added economic value. Acid leaching is then used to extract a large amount of lithium, nickel, and cobalt from the black powder, along with a smaller amount of manganese. The effectiveness of the acid leaching process is directly correlated with the recovery efficiency. Acid leaching is considered the most critical step in black powder treatment. Therefore, improving leaching efficiency is a key factor in this recovery process. Typically, methods such as stirring and heating the acid leaching process or applying pressure are used to increase the metal ion leaching rate. However, these methods inevitably increase energy consumption and processing costs. Furthermore, the currently used strong acids, such as sulfuric acid and hydrochloric acid, are highly corrosive and tend to produce sulfur-chlorine-containing solutions, which are not environmentally friendly. Therefore, adopting an environmentally friendly, low-energy consumption and high-leaching efficiency recycling method is undoubtedly of great significance for lithium battery recycling.

[0005] The closest approach is the application titled "Method for Recycling Waste Lithium Batteries to Produce Cobalt Oxide and Reuse Mother Liquor During the Production Process" (Application Publication No.: CN119409237A). This approach utilizes citric acid and hydrogen peroxide as valuable metal leaching agents, achieving efficient leaching of valuable metals such as lithium and cobalt, reducing reliance on strong acids and minimizing safety risks and environmental pollution during the recovery process. This approach is primarily based on a wet lithium battery recovery process, using citric acid to leach target element ions while minimizing environmental pollution. Hydrogen peroxide is then used for acid-base neutralization to precipitate target element compounds, and the heat generated by this neutralization reduces heating energy consumption during the leaching process. Summary of the Invention

[0006] In response to the many problems existing in the traditional lithium battery wet recycling process, such as dependence on strong acid (using highly corrosive reagents such as sulfuric acid and hydrochloric acid, generating sulfur / chlorine-containing wastewater with high treatment costs), high oxidant consumption (oxidants such as hydrogen peroxide have low utilization rates and need to be added in excess), high energy consumption (leaching reaction requires high temperature (>80°C) or long-term stirring, which consumes significant energy), and poor metal selectivity (impurity metals (Fe, Al) and target metals (Co, Ni, Li) are co-dissolved, making separation difficult), this patent focuses on the perspective of photocatalytic assisted recovery of lithium batteries, which effectively improves the above problems to a certain extent.

[0007] Photocatalysis has been used in wastewater treatment in the prior art, but has not yet been effectively integrated into lithium battery metal recovery. This invention achieves efficient metal leaching and selective separation by designing a novel photocatalytic reaction system.

[0008] Although the existing technical solutions take environmental protection and leaching efficiency into consideration, they still need to use additional ball milling operations to promote the leaching process. It should be pointed out that the ball milling process is likely to cause impurity elements to enter the leachate, which is not conducive to the essential purpose of leaching and purification, and the ball milling process itself is also a high-energy consumption operation. Based on this, the present invention designs a method and system for photocatalytically assisted recovery of lithium batteries. Titanium dioxide / graphene composite photocatalyst (TiO2@rGO) is introduced into the malic acid-hydrogen peroxide leaching system, and hydroxyl radicals (·OH) and holes (h + ) to accelerate metal oxidation and complexation reactions. Furthermore, a multi-stage photocatalytic reaction tank is set up in the leachate. By adjusting the light intensity and wavelength in each zone, different metal ions are precipitated step by step. This enables the application of photocatalysis in lithium metal recovery.

[0009] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0010] A method for photocatalytically assisting the recovery of lithium battery materials comprises the following steps:

[0011] (1) Mixing lithium battery black powder with malic acid and hydrogen peroxide, and adding titanium dioxide / graphene composite photocatalyst;

[0012] (2) Leaching reaction occurs under ultraviolet light, releasing metal ions through photocatalytic-chemical synergistic effects;

[0013] (3) A multi-stage light-controlled gradient precipitation method was used to separate Fe / Al, Co / Ni, and Li components step by step.

[0014] Preferably, the mass ratio of the lithium battery black powder to malic acid and hydrogen peroxide in step (1) is 1:1:1.

[0015] Preferably, the composite photocatalyst in step (1) is a composite material of TiO2 nanotubes and reduced graphene oxide, wherein the TiO2 loading amount is 50-70 wt%.

[0016] Preferably, the added amount of the composite photocatalyst is 1 wt%.

[0017] Preferably, the conditions for the leaching reaction under ultraviolet light irradiation in step (2) are: wavelength of 254-365nm, power density of 50-100W / m 3 .

[0018] Preferably, the multi-stage light-controlled gradient precipitation in step (3) comprises:

[0019] 1) Precipitation of Fe / Al hydroxides under primary UV-A irradiation;

[0020] 2) Precipitating Co / Ni sulfides by introducing H2S gas under secondary UV-C illumination;

[0021] 3) Li2CO3 precipitation under three-level visible light.

[0022] Preferably, the wavelength of the primary UV-A light in step 1) is 365 nm, and the pH is adjusted to 3-4 in this step.

[0023] Preferably, the wavelength of the secondary UV-C light in step 2) is 254 nm, and the pH is adjusted to 6-7 in this step.

[0024] Preferably, the wavelength of the tertiary visible light in step 3) is 450 nm, and the pH is adjusted to 10-11 in this step.

[0025] The present invention also provides a system for photocatalytically assisting the recovery of lithium battery materials, comprising: a sorting module, a leaching module, a precipitation module, and a recovery module.

[0026] Compared with the prior art, the present invention has the following technical advantages:

[0027] (1) The main method to improve the efficiency of acid leaching at present is to pressurize or heat during the acid leaching process. A small number of studies have also proposed sulfuric acid aging (that is, before acid leaching, the positive and negative electrode black powders are mixed with a small amount of low-concentration acid in advance and left to stand at high temperature for pretreatment, and then leached with high-concentration acid). In the "Method for Recycling Waste Lithium Batteries to Produce Cobalt Oxide and Reusing Mother Liquor in the Production Process", it mainly considers environmental protection and reduces energy consumption by acid-base mixing. However, in the leaching process, in order to improve the leaching rate of metal ions in the acid leaching process, it still needs to improve the leaching rate through the process of ball milling mixing. Therefore, the present invention better combines environmental protection, low energy consumption and leaching efficiency, selects malic acid and hydrogen peroxide as leaching agents, and then introduces a photocatalyst to promote the rapid leaching of metal ions with the help of ultraviolet light, reducing the reaction time and the amount of chemical reagents used, and completing the recovery process at close to room temperature, further reducing the recovery cost, and ensuring the leaching efficiency of metal ions. In general, the present invention combines the requirements of environmental protection, low energy consumption and high efficiency by introducing the photocatalytic effect into the lithium battery recycling process, and provides a new possibility for the process optimization of waste lithium battery recycling.

[0028] (2) The method of the present invention is green and efficient, reducing the amount of strong acid and oxidant used, and the photocatalyst can be recycled, resulting in no secondary pollution. Furthermore, the method achieves metal selective precipitation by controlling light intensity and wavelength, resulting in a high purity precipitate. Finally, the method utilizes ultraviolet light catalysis to enhance leaching efficiency and promote effective precipitation of metal ions, significantly reducing energy consumption during the recovery process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1It is the system module diagram;

[0030] Figure 2 This is the experimental flow chart. DETAILED DESCRIPTION

[0031] Lithium battery recycling: After thousands of charge and discharge cycles, lithium batteries reach their end of life, experiencing performance degradation and ultimately becoming scrapped. At this point, for environmental and resource reasons, some of the internal resources are recycled and reused. The main lithium batteries currently used are lithium iron phosphate, lithium cobalt oxide, and ternary (nickel, cobalt, manganese) batteries.

[0032] Crushing and sorting: The lithium battery is directly crushed by physical means such as roller crushing and grinder grinding, and then the positive and negative electrode black powders are obtained through high-temperature pyrolysis drying, airflow screening and other steps. The means here vary according to the specific method, and the negative electrode black powder here contains binders, lithium, iron, copper, aluminum and other single or compound impurities, while the positive electrode black powder often includes nickel, cobalt, manganese, lithium and other compounds.

[0033] Lithium battery wet recycling process: The lithium battery electrode materials to be recycled (mostly positive electrode materials in terms of economic value) are crushed, ground, and airflow sorted to obtain black powder. Strong acids and strong bases are then used to leach high-value elemental products from the black powder and remove impurity elements as much as possible. This process is often accompanied by auxiliary methods such as high temperature and high pressure to leach the target element products as much as possible and remove impurity elements. Chemical reagents are then added to precipitate the target element products. After a series of steps such as washing and impurity removal, the high-value products of lithium batteries are recovered.

[0034] In the present invention, Figure 1 As shown, a system for photocatalytically assisted recovery of lithium battery materials includes a sorting module, a leaching module, a precipitation module, and a recovery module.

[0035] The leaching module includes a photocatalytic leaching reactor (including an ultraviolet light source and a stirring device).

[0036] The precipitation module includes a three-stage gradient light-controlled precipitation tank (equipped with light sources of different wavelengths and a pH control module).

[0037] The recovery module includes a magnetic catalyst recovery device.

[0038] Experimental process: Set up one group of experimental samples and two groups of control samples. The specific implementation process is as follows Figure 2 .

[0039] Experimental samples (photocatalysis and gradient precipitation):

[0040] like Figure 2As shown, the fully discharged waste lithium batteries are processed into black powder containing impurities and target elements (lithium, nickel, cobalt, manganese, etc.) through the sorting module. The waste lithium batteries here are mainly ternary lithium batteries, and the positive electrode black powder is mainly processed based on its economic value.

[0041] (1) Dry the sorted black powder at 150°C for more than 2 hours to remove as much moisture or other organic binders as possible.

[0042] (2) The black powder cooled to room temperature was mixed with 1 mol / L malic acid and hydrogen peroxide (H2O2 1 vol%) (mass ratio of 1:1:1), and 1 wt% TiO2@rGO was added as a photocatalyst. The temperature was kept at room temperature and stirred for 1 h. The leaching module was irradiated with ultraviolet light (254-365 nm, power density 50-100 W / m 2 ) are excited to generate hydroxyl radicals (·OH) and holes (h + ), accelerating metal oxidation and complexation reaction. (Reaction formula: Co3O4+H2O2+hν→3Co 2+ +4H2O+O2↑)

[0043] (3) The leachate is subjected to a multi-stage photocatalytic reaction in the precipitation module. By adjusting the light intensity and wavelength in each area, different metals are precipitated step by step:

[0044] 1) Low-intensity UV-A (365 nm): adjust the pH to 3-4 and precipitate Fe(OH)3 / Al(OH)3;

[0045] 2) High-intensity UV-C (254 nm): Adjust the pH to 6-7 and introduce H2S gas (0.1-0.3 vol%) to selectively precipitate CoS / NiS;

[0046] 3) Visible light region (450nm): Adjust the pH to 10-11, add NaCO3, and precipitate Li2CO3.

[0047] (4) During the step-by-step precipitation process, the corresponding precipitates were washed with deionized water and dried for recovery in combination with a recovery module. In addition, the catalyst was recovered by magnetic separation (TiO2@rGO loaded with magnetic Fe2O3 nanoparticles) and recycled for ≥10 times after ultrasonic cleaning.

[0048] Control sample 1 (malic acid and hydrogen peroxide treated at room temperature):

[0049] (1) Dry the sorted black powder at 150°C for more than 2 hours to remove as much moisture or other organic binders as possible.

[0050] (2) The black powder cooled to room temperature was mixed with 1 mol / L malic acid and hydrogen peroxide (H2O2 1 vol%) (mass ratio of 1:2:2), and the temperature was kept at room temperature and stirred for 2 h.

[0051] (3) The pH value of the leachate is further adjusted by hydrogen peroxide to generate a precipitate, which is then washed and dried for recovery.

[0052] Control sample 2: (treated with sulfuric acid and hydrogen peroxide)

[0053] (1) Dry the sorted black powder at 150°C for more than 2 hours to remove as much moisture or other organic binders as possible.

[0054] (2) The black powder cooled to room temperature was mixed with 1 mol / L sulfuric acid (mass ratio of 1:1), the temperature was kept at room temperature and stirred for 2 h.

[0055] (3) Further adjusting the pH value of the leachate with hydrogen peroxide to generate a precipitate, washing and drying the precipitate for recovery (mixing hydrogen peroxide with concentrated sulfuric acid will release a large amount of heat in a short time, posing a safety hazard such as splashing, and the reaction is prone to generate sulfur-containing wastewater).

[0056] The element leaching rates and precipitation purities of the experimental group, control group 1, and control group 2 are shown in Table 1.

[0057] Table 1 Element leaching rate and precipitation purity

[0058]

[0059] Based on the above experimental process and the element leaching rate and precipitation purity in Table 1, a conclusion can be drawn. In the experimental group using photocatalysis and assisted light gradient precipitation, the nickel and cobalt leaching rate was >99.5% under the conditions of shortening the leaching time and halving the amount of hydrogen peroxide, and the overall performance was the best. It reflects that the scheme of the present invention combines the characteristics of high efficiency and low energy consumption. At the same time, the leaching effect of the control group two is better than that of the control group one, but the mixture of strong sulfuric acid and strong alkaline hydrogen peroxide has safety hazards, and the control group two finally generates difficult-to-treat sulfur-containing wastewater, which is not conducive to environmental protection. In addition, it is worth mentioning that the photocatalyst carbon dioxide and graphene composite material in the experimental group can be recovered by magnetic separation (magnetic Fe2O3 is attached during the acid leaching process) and can be used again after ultrasound.

Claims

1. A method for photocatalytically assisted recovery of lithium battery materials, characterized in that: The following steps are involved: (1) Mixing lithium battery black powder with malic acid and hydrogen peroxide, and adding titanium dioxide / graphene composite photocatalyst; (2) Leaching reaction occurs under ultraviolet light, releasing metal ions through photocatalytic-chemical synergistic effects; (3) A multi-stage light-controlled gradient precipitation method was used to separate Fe / Al, Co / Ni, and Li components step by step.

2. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: The mass ratio of the lithium battery black powder to malic acid and hydrogen peroxide in step (1) is 1:1:

1.

3. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: The composite photocatalyst in step (1) is a composite material of TiO2 nanotubes and reduced graphene oxide, wherein the TiO2 loading amount is 50-70wt%.

4. The method for photocatalytically assisted recovery of lithium battery materials according to claim 3, wherein: The added amount of the composite photocatalyst is 1 wt %.

5. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: The conditions for the leaching reaction under ultraviolet light irradiation in step (2) are: wavelength 254-365nm, power density 50-100W / m 3 .

6. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: The multi-stage light-controlled gradient precipitation in step (3) includes: 1) Precipitation of Fe / Al hydroxides under primary UV-A irradiation; 2) Precipitating Co / Ni sulfides by introducing H2S gas under secondary UV-C illumination; 3) Li2CO3 precipitation under three-level visible light.

7. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: In step 1), the wavelength of the primary UV-A light is 365 nm, and the pH is adjusted to 3-4 in this step.

8. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: The wavelength of the secondary UV-C light in step 2) is 254 nm, and the pH is adjusted to 6-7 in this step.

9. The method for photocatalytically assisted recovery of lithium battery materials according to claim 1, wherein: In step 3), the wavelength of the tertiary visible light is 450 nm, and the pH is adjusted to 10-11 in this step.

10. A system for implementing the method according to any one of claims 1 to 9, characterized in that: include: Sorting module, leaching module, sedimentation module, and recovery module.

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