Lithium battery recycling method based on separation of intrinsic photo-generated electron-hole pairs of positive electrode sheet

Abstract

This invention provides a method for recycling waste lithium batteries based on the intrinsic photogenerated electron-hole pair separation of the cathode sheet. The method involves: whole-body crushing of the waste cathode sheet containing the positive electrode active material and aluminum foil current collector to form a mixture; placing the mixture in an acid leaching solution, and then applying an external light field matching the light absorption band of the cathode material. Under illumination, the cathode material is excited to generate electron-hole pairs, where the photogenerated holes are efficiently captured and consumed by the aluminum foil. This allows the photogenerated electrons to efficiently and specifically reduce high-valence metals in the cathode material, achieving enhanced leaching of valuable metals. This invention is the first to utilize the inherent aluminum foil in the waste to construct an "intrinsic hole consumption channel," improving light energy utilization and valuable metal leaching efficiency without the need for external photocatalysts or hole-consuming agents. It achieves efficient and green recycling of valuable metals such as lithium, cobalt, nickel, and manganese under lower acid consumption and milder conditions.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery resource recycling technology, and relates to a lithium battery recycling method based on the separation of intrinsic photogenerated electron-hole pairs in the positive electrode sheet. Specifically, it relates to a method that leverages the intrinsic photoresponse characteristics of the positive electrode material and uses aluminum foil, the current collector of the positive electrode sheet, as a hole consuming agent, to enhance the leaching of valuable metals in the positive electrode material of waste lithium batteries through an external light field. Background Technology

[0002] Since their commercialization in the 1990s, lithium-ion batteries have become the mainstream rechargeable energy storage device in portable electronic devices, widely used in consumer electronics and gradually expanding into key areas such as electric vehicles, large-scale energy storage, aerospace, and military equipment. With the continuous increase in consumption, the scale of waste lithium-ion batteries has also expanded dramatically. Improper disposal of these waste batteries poses a serious threat to the environment due to the heavy metals and electrolytes they contain; simultaneously, the valuable metals in the cathode materials, such as cobalt, lithium, nickel, and manganese, especially strategic cobalt and lithium resources, will be wasted. Therefore, developing efficient and green recycling technologies to achieve the circular utilization of these key metal resources has become a research hotspot and urgent need in the field of resources and environment.

[0003] Currently, the resource recycling technologies for waste lithium-ion batteries are mainly divided into three categories: physical methods, chemical methods, and biological methods. Among them, chemical recycling technology, represented by hydrometallurgy, has become the mainstream process due to its high metal recovery rate and good product purity. This technology typically involves first leaching the waste cathode material with acid and a reducing agent to transfer metal ions into the solution, and then separating and enriching them through methods such as precipitation and extraction. In the leaching stage, elements such as cobalt, nickel, and manganese in mainstream cathode materials (such as LiCoO2 and ternary materials) are usually in a high oxidation state (Co). 3+ Ni 3+ Mn 4+ High-valence metals exist and are chemically stable, making them difficult to dissolve directly by acids. Therefore, current processes generally rely on adding external chemical reducing agents such as hydrogen peroxide and sodium sulfite to reduce high-valence metals to low-valence states, thereby promoting their leaching.

[0004] However, this traditional "acid leaching + external reducing agent" model has inherent drawbacks: reducing agents (such as H2O2) are unstable and easily decompose under acidic conditions, leading to low utilization and increased costs; the reaction process may be violently exothermic, posing safety risks; and the addition of excessive reducing agent can introduce impurity ions, increasing the difficulty and cost of subsequent solution purification and wastewater treatment. Existing technologies, such as CN107326181A, a one-step recycling method for stripping and leaching waste lithium-ion batteries, and CN120384193A, a method for separating and recovering metal elements in the leachate of waste ternary lithium-ion batteries, provide specific leaching solutions, but none of them have been able to completely eliminate the dependence on external reducing agents, and economic and environmental issues remain prominent. Therefore, developing a new method that can reduce or even avoid the use of external strong chemical reducing agents and achieve green and efficient leaching from the source is of great significance for promoting the upgrading of waste lithium-ion battery recycling technology.

[0005] Some studies have attempted to introduce photocatalysis to treat pollutants or decompose water, but research on its application in complex solid waste systems such as the leaching of spent batteries is still limited. More importantly, the inventive team of this application has discovered for the first time that many spent cathode materials possess intrinsic photoresponsive characteristics, which can be excited under appropriate wavelengths of light to generate photoelectrons. If this characteristic can be utilized, supplementing the acid leaching process with natural light irradiation, and using photoelectrons to directly reduce high-valence metals in the cathode material's crystal lattice, theoretically, leaching could be significantly accelerated, eliminating the need for external reducing agents. Currently, there are no reported methods for systematically utilizing the intrinsic photoresponsive characteristics of spent cathode materials to achieve efficient leaching in inorganic acid systems.

[0006] Furthermore, in exploring ways to utilize light energy, effectively separating and utilizing photogenerated carriers (electron-hole pairs) is key to improving efficiency. If holes are not consumed in time, they will rapidly recombine with electrons, leading to a sharp decline in light energy utilization. In the scenario of waste battery recycling, the positive electrode itself contains a highly conductive aluminum foil current collector. This invention is the first to discover and utilize this unique structural advantage: after the positive electrode is completely crushed, the aluminum foil can act as a highly efficient hole capture and consumption medium in the photoleaching system, reducing the load on photogenerated electrons. Thus, the electrons will be directed to reduce the metal, achieving "waste-to-waste" treatment and doubling the leaching efficiency of valuable metals. Currently, there are no reports of methods that systematically utilize the photoresponse of waste positive electrode materials themselves and synergize with aluminum foil to enhance leaching. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a valuable metal enhanced leaching and recycling method based on the synergistic effect of the intrinsic photoresponse of the cathode material and the hole consumption of the aluminum foil. This method abandons the traditional approach of adding an external reducing agent and utilizes the residual semiconductor properties of the waste cathode material to generate strongly reducing photogenerated electrons in situ in the acid leaching system under the excitation of an external light field. Furthermore, it utilizes the current collector of the aluminum foil in the waste cathode sheet to consume the photogenerated holes, thereby providing a more efficient, greener, and more cost-effective valuable metal enhanced leaching and recycling method.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for enhanced leaching and recovery of valuable metals based on the synergistic effect of the intrinsic photoresponse of the cathode material and the hole consumption of aluminum foil, comprising the following steps: S1. The waste lithium battery positive electrode sheet is crushed as a whole to obtain a mixture containing positive electrode active material and aluminum foil current collector; S2. The mixture obtained in S1 is placed in an acid leaching solution, and then an external light field matching the intrinsic photoresponse of the cathode material is applied. Under the irradiation of the external light field, the cathode material is excited to generate electron-hole pairs; among which, photogenerated holes (h + The electrons are captured and consumed by the aluminum foil, thereby inhibiting electron-hole recombination and enriching photogenerated electrons (e.g., electrons that are trapped and consumed by the aluminum foil). - It directly reduces the high-valence valuable metals in the cathode material, enabling them to dissolve more effectively in ionic form.

[0009] Preferably, the overall crushing mentioned in S1 refers to mechanically crushing the waste positive electrode sheet without pre-separating the aluminum foil, so that the aluminum foil and the positive electrode active material form a physically tightly bonded mixture, wherein the particle size of the mixture is less than 2 mm. The mass ratio of the positive electrode active material to the aluminum foil in the mixture is maintained at the same level as in the original positive electrode sheet, with the positive electrode active material accounting for 88%~92% and the aluminum foil accounting for 8%~12%.

[0010] Preferably, the acid leaching solution in S2 is an inorganic acid solution, including sulfuric acid, hydrochloric acid or nitric acid, and the concentration of the acid leaching solution is 0.5 mol / L to 2.0 mol / L.

[0011] Preferably, the ratio of the mixture to the acid leachate in S2 is 1g:(15 mL~25 mL).

[0012] Preferably, the light source for the external light field in S2 is selected from a xenon lamp, a mercury lamp, or a white LED lamp, wherein the wavelength of the xenon lamp is 200 nm to 2500 nm, the mercury lamp is 200 nm to 800 nm, and the white LED lamp is 400 nm to 700 nm; the light intensity is 100 mW / cm². 2 ~300 mW / cm2 .

[0013] Preferably, the reaction temperature for the dissolution of valuable metals in S2 is 40℃~60℃, the stirring rate is 300 rpm~800 rpm, and the reaction time is 2~6h.

[0014] This invention also provides an application of the valuable metal enhanced leaching and recovery method based on the synergistic effect of intrinsic photoresponse of cathode material and hole consumption of aluminum foil in the resource recycling of cathode materials of retired power batteries or lithium batteries of consumer electronics products.

[0015] The basic principle of this invention is that layered lithium transition metal oxide cathode materials (such as NCM and LCO) still possess semiconductor properties after discharge cycling, and can generate electron-hole pairs (e-hole pairs) under matched illumination. - -h + This invention involves breaking the positive electrode sheet (active material + aluminum foil) into a single piece, ensuring close contact between the highly conductive aluminum foil and the active material particles; under illumination, photogenerated holes (h...) + It can rapidly migrate to the surface of aluminum foil, and in an acidic environment, the aluminum foil itself can be dissolved by oxidative oxidation (Al-3e). - →Al 3+ Alternatively, holes can be consumed by oxidizing reducing components (such as water or organic acids) in the solution using aluminum foil. This process efficiently removes holes and greatly inhibits electron-hole recombination, thus enabling photogenerated electrons (e... - It can highly enrich and focus on reducing high-valence metal ions (such as Co) in the crystal lattice. 3+ Ni 3+ Mn 4+ This resulted in a significant improvement in leaching rate and efficiency.

[0016] Compared with the prior art, the present invention has the following significant technical effects: 1. Mechanism Synergistic Innovation: This invention not only utilizes the intrinsic photoresponse of the cathode material, but also creatively transforms waste aluminum foil in the waste into a beneficial component that improves photochemical efficiency. It establishes a highly efficient synergistic mechanism for photogenerated electrons to reduce metal and aluminum foil to consume holes, which is novel in principle.

[0017] 2. Increased Leaching Efficiency: The high efficiency of aluminum foil in consuming holes significantly improves the utilization rate of photogenerated electrons. Compared to photoleaving using only pure positive electrode active material powder, the metal leaching rate and final leaching rate can be significantly improved. Furthermore, this invention can precisely adjust the wavelength of the applied light field to selectively excite specific material components, thereby controlling the leaching rate of different valuable metals (such as Co, Ni, and Mn), providing a new technical path for achieving selective leaching.

[0018] 3. Simplified Process and Reduced Costs: This invention eliminates the cumbersome aluminum foil separation steps (such as heat treatment and organic solvent dissolution) during pretreatment in traditional processes, simplifying the process and reducing energy consumption and costs. Simultaneously, the aluminum foil dissolution product Al... 3+ It is easy to remove in subsequent neutralization and precipitation steps without introducing new separation problems.

[0019] 4. Higher level of greenness: Through the built-in "hole consumption-electron utilization" cycle, the dependence on any form of external reagents (including reducing agents and additional hole trapping agents) is further reduced, making the process more self-consistent and environmentally friendly.

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of the valuable metal enhanced leaching process based on the synergistic effect of intrinsic photoresponse of positive electrode material and hole consumption of aluminum foil according to the present invention.

[0022] Figure 2 The diagram shows the photoresponse performance of the photoexcited cathode material of the present invention: (a) Comparison of the impedance of the active material under light and no light conditions; (b) Photoresponse current density of the active material under light and no light conditions; (c) Change in open-circuit voltage of the active material.

[0023] Figure 3 This is a schematic diagram of the enhanced leaching mechanism of aluminum foil synergistically consuming holes and electrons to reduce metal under light field excitation according to the present invention. Detailed Implementation

[0024] Figure 1 This is a flowchart of the valuable metal enhanced leaching process based on the synergistic effect of intrinsic photoresponse of positive electrode material and hole consumption of aluminum foil according to the present invention.

[0025] Figure 2Figure 1 shows the photoresponse performance of the photo-excited cathode material of this invention. (a) Comparison of active material impedance with and without illumination; (b) Photoresponse current density of the active material with and without illumination; (c) Change in open-circuit voltage of the active material. In Figure (a), the black curve (eis) represents the condition without illumination, and the red curve (eis-light) represents the condition with illumination. After illumination, the charge transfer impedance decreases significantly, indicating that the applied light field can effectively promote charge transfer inside the cathode material, improve the interface charge transport capability, and reduce the interface impedance. As can be seen from Figure (b), the current rises rapidly and forms a peak each time illumination is applied; after illumination stops, the current quickly falls back to the baseline level, exhibiting typical transient photoresponse behavior. The current peak can be repeated under multiple switching cycles, indicating that the photoresponse of this cathode material has good stability and reversibility. Figure (c) shows that the open-circuit voltage rises rapidly at the moment of illumination and then remains stable at a higher potential. These results demonstrate that an applied light field can significantly excite the intrinsic photoresponse performance of the cathode material, providing direct electrochemical evidence for subsequent enhanced leaching of valuable metals based on the synergistic effect of the intrinsic photoresponse of the cathode material and the hole consumption of the aluminum foil. Example 1

[0026] This embodiment describes a photo-enhanced leaching method using a sulfuric acid system based on waste NCM523 cathode sheets containing aluminum foil, including the following steps: S1. The waste NCM523 cathode sheet obtained from dismantling retired power batteries (active material areal density approximately 20 mg / cm³) 2 The material is directly mechanically crushed into fragments with a particle size of less than 2 mm to obtain a mixture containing positive electrode active material and aluminum foil current collector (the aluminum foil accounts for about 10% of the mass). S2. Weigh 15.0 g of the mixture obtained in S1 and place it in a 500 mL photochemical reactor. Add 300 mL of 1.5 mol / L H2SO4 solution (liquid-to-solid ratio of 20 mL / g) to form a solid-liquid mixture. Maintain the system temperature at 60℃ and mechanically stir at 400 rpm. Irradiate the reaction system vertically with a 300W xenon lamp light source (spectral range 200-2500nm) equipped with an AM1.5 filter. The average light intensity inside the reactor is 300 mW / cm². 2 After continuous irradiation for 4 hours, the residue (mainly aluminum foil and a small amount of undissolved matter remaining after the reaction) was separated by filtration to obtain the leachate.

[0027] Under illumination, NCM523 material is excited to generate electron-hole pairs (e-hole pairs). - -h + The coexisting aluminum foil, as an excellent electron donor, rapidly captures and consumes photogenerated holes (Al→Al). 3+ +3e -This effectively suppresses electron-hole pair recombination; the enriched photogenerated electrons (e - Ni in the lattice of the cathode material 3+ Co 3+ Mn 4+ The in-situ reduction of high-valence metal ions to low-valence states severely disrupts lattice stability, allowing them to dissolve rapidly in sulfuric acid, thus achieving photo-enhanced leaching. The metal concentrations in the leachate of this example were determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that after 4 hours of illumination, the leaching rates of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) reached 98.7%, 99.0%, 98.8%, and 95.5%, respectively.

[0028] In addition, this embodiment also investigated the effects of different light sources and low acid concentration conditions on the photo-enhanced selective leaching of waste NCM523 cathode sheets containing aluminum foil using a sulfuric acid system, as detailed below: 1. The influence of different light sources Includes the following steps: S1, Same as above NCM523 mixture (containing positive electrode active material and aluminum foil, with aluminum foil accounting for approximately 10% by mass). S2. Weigh four portions of the mixture from S1, each 10.0 g, and add 200 mL of 1.0 mol / L H2SO4 solution to each portion (liquid-to-solid ratio 20 mL / g). Irradiate each portion with different light sources at 50℃ and 600 rpm, with the light intensity controlled at 200 mW / cm². 2 .

[0029] Light source A: Mercury lamp (200-800nm) Light source B: Xenon lamp (200-2500nm) Light source C: White LED light (400-700nm) Light source D: Dark conditions (control) Samples were taken at 30, 60, and 120 min to analyze the changes in Ni and Mn concentrations in the leachate.

[0030] The results showed that under mercury lamp irradiation, the leaching rates of Ni and Mn both exceeded 90% after 120 min, with similar leaching rates. Under xenon lamp irradiation, the leaching rates of Ni and Mn both reached 95% after 120 min. However, under white LED lamp irradiation, the leaching rate of Ni reached 90% after 120 min, but the leaching rate of Mn was only 75%, exhibiting a certain degree of selectivity. Under dark conditions, the leaching rates of both were below 40%. This is because the different dd transition energy levels of different metal ions lead to differences in the absorption and charge excitation efficiency of the cathode material for different wavelengths of light. By controlling the wavelength of the applied light field, charge separation at specific metal sites can be preferentially excited, thereby controlling their reduction and leaching rates. This provides the possibility for selective leaching or enrichment of specific metals.

[0031] 2. Effects of low acid concentration Includes the following steps: S1, Same as above NCM523 mixture (containing positive electrode active material and aluminum foil, with aluminum foil accounting for approximately 10% by mass). S2. Weigh 10.0 g of the mixture from S1 and place it in a reactor. Add 200 mL of 0.5 mol / L H2SO4 solution (liquid-to-solid ratio 20 mL / g). Irradiate the mixture with a xenon lamp (200-2500 nm, 200 mW / cm²) at 40℃ and 800 rpm. 2 The reaction was carried out for 6 hours, and a control experiment was set up under dark conditions.

[0032] The results showed that after 6 hours of illumination, the leaching rates of Li, Ni, Co, and Mn reached 95.2%, 94.8%, 93.1%, and 90.5%, respectively; while under the same acid concentration and temperature but without illumination in the dark, the leaching rates of all metals were less than 20% after 6 hours. These results demonstrate that even with significantly reduced acid concentration (0.5 mol / L) and lower temperature (40℃), efficient leaching can still be achieved through the photo-enhanced mechanism of this invention. This greatly reduces reagent consumption and the burden of subsequent neutralization treatment, highlighting the advantages of this invention in green and low-carbon applications. Example 2

[0033] This embodiment describes a photo-enhanced leaching method using hydrochloric acid based on waste NCM811 cathode sheets containing aluminum foil, including the following steps: S1. The waste NCM811 positive electrode sheet obtained from the dismantling of retired power batteries is directly mechanically crushed into fragments with a particle size of less than 2 mm to obtain a mixture containing positive electrode active material and aluminum foil current collector (aluminum foil accounts for about 10%). S2. Weigh 10.0 g of the mixture obtained in S1 and place it in a 250 mL quartz photocatalytic reaction flask. Add 200 mL of 1.0 mol / L hydrochloric acid solution (liquid-to-solid ratio 20 mL / g). Incubate the mixture at 50℃ and 500 rpm using a xenon lamp (wavelength 200-2500 nm, light intensity 100 mW / cm²). 2 Irradiate for 3 hours, and then filter to obtain the leachate after the reaction.

[0034] This embodiment verifies the universality of using aluminum foil to capture holes and enhance photoleaching in a hydrochloric acid system. The aluminum foil itself oxidizes and dissolves in hydrochloric acid (2Al + 6H₂O). + →2Al 3+ + 3H2↑), this oxidation process and the consumption of photogenerated holes are thermodynamically synergistic, further promoting the transfer and consumption efficiency of holes and accelerating the overall leaching process. A schematic diagram of its leaching mechanism can be found in [reference needed]. Figure 3 ICP-OES analysis showed that after 3 hours, the leaching rates of Li, Ni, Co, and Mn were 99.1%, 98.8%, 98.5%, and 96.2%, respectively.

[0035] In addition, this embodiment also studied the photo-enhanced selective leaching effect of waste NCM811 positive electrode sheets containing aluminum foil in hydrochloric acid systems under different solid-liquid ratios, including the following steps: S1, Same as above NCM811 mixture (containing positive electrode active material and aluminum foil, with aluminum foil accounting for approximately 10% by mass). S2. Weigh 40g, 20g, 16g, 10g, and 8g of the mixture from S1, respectively, and place them in a 250mL quartz photocatalytic reaction flask. Add 200mL of 1.0mol / L hydrochloric acid solution to obtain sample solutions with liquid-to-solid ratios of 5mL / g, 10mL / g, 12.5mL / g, 20mL / g, and 25mL / g, respectively. Under conditions of 50℃ and 500rpm, use a xenon lamp (wavelength 200-2500nm, light intensity 150 mW / cm²). 2 Irradiate for 3 hours, and then filter to obtain the leachate after the reaction.

[0036] The results are shown in Table 1: Table 1 Leaching Rate The results show that the leaching rate of elements initially increases and then stabilizes as the liquid-to-solid ratio increases. This is because when the liquid-to-solid ratio is low, the amount of acid used is insufficient to completely leach the elements from the mixture. As the acid content in the solution decreases, the leaching reaction is hindered, resulting in a low leaching rate. Therefore, in the initial stage, the leaching rate increases with the increase of the liquid-to-solid ratio. Once the liquid-to-solid ratio reaches a certain level, the acid content in the solution is sufficient to completely leach the elements from the material. At this point, the leaching rate tends to stabilize and no longer increases with the increase of the solid-liquid ratio. Example 3

[0037] This embodiment describes a photo-enhanced leaching method using a nitric acid system based on waste NCM622 cathode sheets containing aluminum foil, including the following steps: S1. The waste NCM622 positive electrode sheet obtained from the dismantling of retired power batteries is directly mechanically crushed into fragments with a particle size of less than 2 mm to obtain a mixture containing positive electrode active material and aluminum foil current collector (aluminum foil accounts for about 10%). S2. Take 10 g of the mixture obtained in S1 and place it in a photochemical reactor. Add 200 mL of 1.2 mol / L nitric acid solution (liquid-to-solid ratio 20 mL / g). Irradiate the mixture with a xenon lamp at 50℃ and 800 rpm, with a wavelength of 200-2500 nm and a light intensity of 300 mW / cm². 2 The reaction was carried out for 3 hours to obtain the leachate.

[0038] The concentrations of Li, Ni, Co, and Mn in the leachate were analyzed, and the leaching rates were calculated. The results showed that after 3 hours, the leaching rates of Li, Ni, Co, and Mn were 97.6%, 98.4%, 97.3%, and 95.4%, respectively. This demonstrates that aluminum foil can also be used to capture holes in a nitric acid system to enhance the photoleaching efficiency of NCM. Example 4

[0039] This embodiment describes a photo-enhanced leaching method using a sulfuric acid system based on waste lithium cobalt oxide (LCO) cathode sheets containing aluminum foil, including the following steps: S1. The waste LCO positive electrode sheet obtained from the dismantling of retired power batteries is directly mechanically crushed into fragments with a particle size of less than 2 mm to obtain a mixture containing positive electrode active material and aluminum foil current collector (aluminum foil accounts for about 10%). S2. Weigh 12.0 g of the mixture obtained in S1 and place it in a 500 mL photoreactor. Add 240 mL of 1.0 mol / L sulfuric acid solution (liquid-to-solid ratio 20 mL / g). Heat the mixture at 60℃ and 300 rpm using a xenon lamp (wavelength 200-2500 nm, light intensity 300 mW / cm²). 2 Irradiate for 2.5 hours to obtain leachate.

[0040] After leaching, the leaching rates of lithium (Li) and cobalt (Co) in the leachate were measured to be 99.3% and 98.9%, respectively. This embodiment applies the method of the present invention to layered lithium cobalt oxide materials, demonstrating that the core mechanism of "photoresponse of cathode material - hole consumption of aluminum foil" is universal for cathode materials with different crystal structures (such as layered oxides). Co in LCO 3+ The reduction of the aluminum foil is key to the leaching process, and the efficient consumption of photogenerated holes by the aluminum foil greatly promotes the photogenerated electrons on Co. 3+ The restoration. Example 5

[0041] This embodiment presents a photo-enhanced leaching method using sulfuric acid based on waste NCM811 cathode sheets, and compares it with traditional photo-assisted methods and traditional high-temperature strong acid chemical reduction methods.

[0042] Raw materials: Waste NCM811 positive electrode sheets from the same source are used and processed into two groups: Group I is a mixture of whole crushed materials (containing NCM811 positive electrode active material powder and aluminum foil); Group II is pure NCM811 positive electrode active material powder after stripping.

[0043] Leaching: Group A (Method of this invention): Weigh 10.0 g of the mixture (containing NCM811 positive electrode active material powder and aluminum foil), add 200 mL of 2 mol / L H2SO4 solution, and irradiate with a xenon lamp (200-2500 nm, 200 mW / cm²) at 60℃ and 400 rpm. 2 The reaction was carried out for 3 hours without the addition of any chemical reducing agent.

[0044] Group B (Traditional Illumination-Assisted Method): Weigh 10.0 g of pure NCM811 positive electrode active material powder, add 200 mL of 2 mol / L H2SO4 solution, and irradiate with a xenon lamp (200-2500 nm, 200 mW / cm²) at 60℃ and 400 rpm. 2 The reaction was carried out for 3 hours under the same conditions, without the addition of a reducing agent.

[0045] Group C (Traditional High-Temperature Strong Acid Chemical Reduction Method): Weigh 10.0 g of pure NCM811 positive electrode active material powder, add 200 mL of 2 mol / L H2SO4 solution, and add 3% (v / v) 30% hydrogen peroxide (H2O2) as a reducing agent. React at 80℃, 400 rpm, and in the dark for 2 h.

[0046] The results are shown in Table 2: Table 2 Leaching Results The results show that, compared with group B, group A has a significantly higher leaching rate, fully demonstrating that in the absence of aluminum foil as an efficient hole trapping agent, the electron-hole pairs generated by photoexcitation of the cathode material recombine rapidly, resulting in a severe shortage of photogenerated electrons that can be used to reduce the metal, leading to low photoleaching efficiency. Therefore, the presence of aluminum foil is a necessary condition for achieving efficient photo-enhancing in this invention. Compared with the method in group C, this invention (group A) achieves a leaching efficiency comparable to that of group C (requiring the addition of 3% H2O2 at 80°C) without using any external strong chemical reducing agent and with a 20°C reduction in reaction temperature. If a small amount of reducing agent (e.g., <1% H2O2) still needs to be added to the system of this invention to cope with more demanding raw materials, the amount added can be reduced by more than 65% compared with traditional processes, while the temperature requirement is lower. This fully demonstrates the significant advantages of this invention in terms of safety, economy, and environmental friendliness.

[0047] Comparative Example 1 The leaching effect of waste NCM523 cathode sheets in an organic acid system includes the following steps: S1. The same NCM523 mixture as in Example 1 (containing positive electrode active material and aluminum foil, with aluminum foil accounting for approximately 10% by mass). S2. Weigh 15.0 g of the mixture from S1 and add 300 mL of 1.5 mol / L oxalic acid solution (liquid-to-solid ratio of 20 mL / g). Under the same reaction conditions as in Example 1 (60°C, 400 rpm), vertically irradiate the reaction system using a 300W xenon lamp (spectral range 200-2500 nm). The average light intensity inside the reactor is 300 mW / cm². 2 Continuous irradiation for 4 hours The leaching rates were: Li 39.2%, Ni 40.5%, Co 38.8%, and Mn 39.1%. This result, compared with Example 1 (>95% under light), indicates that organic acids, due to their weak acidity and limited reducing power, have poor leaching ability for materials. Furthermore, oxalic acid leaching often produces in-situ precipitates such as cobalt oxalate and nickel oxalate, which form a passivation layer on the material surface, hindering further dissolution of the internal metals. Therefore, the leaching rate of organic acids for the mixture is significantly lower than that of inorganic acids.

[0048] Comparative Example 2 The leaching effect of using other metals (iron filings) instead of aluminum foil as a hole-consuming agent in waste NCM523 cathode sheets includes the following steps: Weigh 13.5 g of pure NCM523 positive electrode active material powder and add 1.5 g of reduced iron powder (equivalent to the mass of aluminum foil), and mix thoroughly. Add 300 mL of 1.5 mol / L H2SO4 solution and mix under the same light, temperature, and stirring conditions as in Example 1 (300W xenon lamp, wavelength 200-2500 nm, light intensity 200 mW / cm²). 2 The reaction was carried out at 60℃ and 400 rpm for 4 hours.

[0049] The leaching rates were: Li 85.3%, Ni 82.1%, Co 80.5%, and Mn 78.9%. Compared with Example 1 (aluminum foil, >96%), it can be seen that adding exogenous reducing metal (iron) can indeed partially consume holes, proving the universality of the "metal-consuming hole" mechanism, but its effect is lower than using the original aluminum foil. Possible reasons include: in this invention, the positive electrode sheet is directly mechanically crushed to obtain a mixture of positive electrode active material and aluminum foil. The aluminum foil and positive electrode active material are in a mixed state that is not completely dissociated but still fully exposed. In contrast, the contact between iron powder and the positive electrode material in this comparative example is not as tight as that of the originally bonded aluminum foil, resulting in lower hole transfer efficiency; the morphology of iron oxide products may affect light transmission or interfacial reactions. This comparative example highlights the ingenuity and efficiency of this invention in directly utilizing the aluminum foil inherent in the waste material and tightly bound to the active material as a hole trapping agent.

[0050] Comparative Example 3 The leaching effect of waste NCM523 cathode material under different mass ratios of aluminum foil and cathode active material was investigated, including the following steps: S1. After peeling off the waste NCM523 positive electrode sheets from the same batch, positive electrode active material powder and pure aluminum foil were obtained. The positive electrode active material was 10.0 g in mass. The positive electrode active material powder and aluminum foil were physically mixed according to the mass ratio of aluminum foil to positive electrode active material of 0:1 (no aluminum foil), 1:19, 1:9 (close to the original ratio), 3:7, and 1:4 to simulate different aluminum foil ratios and obtain mixed materials.

[0051] S2. Take the mixtures of different aluminum foil ratios obtained in S1 and place them in 500 mL photochemical reactors respectively. Add 250 mL of 1.5 mol / L H2SO4 solution (liquid-to-solid ratio of 25 mL / g) to form a solid-liquid mixture. Maintain the system temperature at 60℃ and mechanically stir at 400 rpm. Irradiate the reaction system vertically with a 300W xenon lamp light source (spectral range 200-2500 nm) equipped with an AM1.5 filter. The average light intensity in the reactor is 200 mW / cm². 2 After continuous irradiation for 4 hours, the residue (mainly aluminum foil and a small amount of undissolved matter remaining after the reaction) was separated by filtration to obtain the leachate.

[0052] The concentrations of each element in the leachate were measured, and the following calculations were performed: When the mass ratio of aluminum foil to positive electrode active material was 0:1, the leaching rates were: Li 93.2%, Ni 90.8%, Co 88.4%, Mn 88.7%; when the mass ratio was 1:19, the leaching rates were: Li 96.4%, Ni 95.8%, Co 95.2%, Mn 94.7%; when the mass ratio was 1:9, the leaching rates were: Li 99.1%, Ni 98.8%, Co 98.2%, Mn 97.7%; when the mass ratio was 3:7, the leaching rates were: Li 98.1%, Ni 98.4%, Co 97.9%, Mn 97.2%; when the mass ratio was 1:4, the leaching rates were: Li 95.4%, Ni 96.1%, Co 96.1%, Co 97.2%, Ni 98.4%, Co 98.9%, Mn 97.2%; when the mass ratio was 1:4, the leaching rates were: Li 95.4%, Ni 96.1%, Co 98.9%, Co 98.4%, Ni 98.8%, Co 98.9%, Mn 98.9%, Co ... The leaching concentration was 95.8%, and the Mn concentration was 94.9%. Experimental results showed that the leaching rate initially increased and then decreased with increasing aluminum foil content. This is because when the aluminum foil content is low, its presence enhances the leaching of the material under illumination, thus increasing the leaching rate. However, when the aluminum foil content exceeds a critical amount, excessive aluminum foil fragments severely block light in the system, affecting the effective irradiation of the cathode material particles. Simultaneously, the oxidation of a large amount of aluminum foil consumes more acid, leading to a slower pH decrease in the system (or a decrease in the actual effective acid concentration), which may affect the leaching kinetics.

[0053] In summary, this invention provides a lithium battery recycling method based on the intrinsic photogenerated electron-hole pair separation of the cathode sheet. The method involves crushing the waste cathode sheet containing the positive electrode active material and aluminum foil current collector to form a mixture. This mixture is then placed in an acid leaching solution, and an external light field matching the light absorption band of the cathode material is applied. Under illumination, the cathode material is excited to generate electron-hole pairs, where the photogenerated holes are efficiently captured and consumed by the aluminum foil. This allows the photogenerated electrons to efficiently and specifically reduce high-valence metals in the cathode material, achieving enhanced leaching of valuable metals. This invention is the first to utilize the inherent aluminum foil in the waste to construct an "intrinsic hole consumption channel," improving light energy utilization and valuable metal leaching efficiency without the need for external photocatalysts or hole-consuming agents. This achieves efficient and green recycling of valuable metals such as lithium, cobalt, nickel, and manganese under lower acid consumption and milder conditions.

[0054] This invention is the first to utilize the aluminum foil inherent in waste to construct an "intrinsic hole consumption channel," which improves light energy utilization and leaching efficiency of valuable metals without the need for external photocatalysts and hole-consuming agents. It achieves efficient and green recycling of valuable metals such as lithium, cobalt, nickel, and manganese under conditions of lower acid consumption and milder conditions.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for enhanced leaching and recovery of valuable metals based on the synergistic effect of intrinsic photoresponse of cathode materials and hole consumption of aluminum foil, characterized in that, Includes the following steps: S1. The waste lithium battery positive electrode sheet is crushed as a whole to obtain a mixture containing positive electrode active material and aluminum foil current collector; S2. The mixture obtained in S1 is placed in an acid leaching solution, and then an external light field matching the intrinsic photoresponse of the cathode material is applied. Under the irradiation of the external light field, the cathode material is excited to generate electron-hole pairs; among which, photogenerated holes (h + The electrons are captured and consumed by the aluminum foil, thereby inhibiting electron-hole recombination and enriching photogenerated electrons (e.g., electrons that are trapped and consumed by the aluminum foil). - It directly reduces the high-valence valuable metals in the cathode material, enabling them to dissolve more effectively in ionic form.

2. The method according to claim 1, characterized in that, The overall crushing mentioned in S1 refers to the mechanical crushing of waste positive electrode sheets without pre-separating the aluminum foil, so that the aluminum foil and the positive electrode active material form a physically tightly bonded mixture, wherein the particle size of the mixture is less than 2 mm.

3. The method according to claim 1, characterized in that, In the mixture described in S1, the mass ratio of the positive electrode active material to the aluminum foil is maintained as it is in the original positive electrode sheet, with the positive electrode active material accounting for 88%~92% and the aluminum foil accounting for 8%~12%.

4. The method according to claim 1, characterized in that, The acid leaching solution mentioned in S2 is an inorganic acid solution with a concentration of 0.5 mol / L to 2.0 mol / L.

5. The method according to claim 4, characterized in that, The inorganic acid is sulfuric acid, hydrochloric acid, or nitric acid.

6. The method according to claim 1, characterized in that, The ratio of the mixture to the acid leachate in S2 is 1g:(15 mL~25 mL).

7. The method according to claim 1, characterized in that, The light source for the external light field described in S2 is selected from xenon lamps, mercury lamps, or white LED lamps, wherein the wavelength of the illumination light from xenon lamps is 200 nm to 2500 nm, from mercury lamps it is 200 nm to 800 nm, and from white LED lamps it is 400 nm to 700 nm; the light intensity is 100 mW / cm². 2 ~300 mW / cm 2 .

8. The method according to claim 1, characterized in that, The reaction temperature for the dissolution of valuable metals in S2 is 40℃~60℃, the stirring rate is 300 rpm~800 rpm, and the reaction time is 2~6h.

9. The application of the valuable metal enhanced leaching and recovery method based on the synergistic effect of intrinsic photoresponse of cathode material and hole consumption of aluminum foil as described in any one of claims 1 to 8 in the resource recovery of cathode materials of retired power batteries or lithium batteries of consumer electronics products.

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