A method for stripping, leaching and self-precipitation recovery of waste lithium battery positive electrode based on multi-stage plasma synergistic activation

Abstract

This invention discloses a method for stripping, leaching, and self-precipitation recycling of waste lithium-ion battery cathodes based on multi-stage plasma synergistic activation: After discharging waste lithium-ion batteries, the cathode sheets are disassembled and stripped off; the cathode sheets are treated under a plasma jet, and activated waste cathode powder is scraped off the cathode sheets; ultrapure water is mixed with the waste cathode powder, a regulator is added to adjust to weakly acidic conditions, and plasma discharge treatment is performed to obtain a solid-liquid mixture, which is then filtered to obtain filter residue and filtrate; the filtrate is diluted and self-precipitated to obtain lithium salt; the lithium salt, filter residue, and reducing carbon source are mixed and calcined to obtain regenerated lithium-ion battery cathode material. The method provided by this invention utilizes plasma synergistic stripping and leaching technology to achieve highly efficient and selective leaching of lithium from waste lithium-ion battery cathodes, overcoming the need for large-scale use of acids and high-purity oxidants. Furthermore, by using a dilution precipitation method, lithium salt can be obtained without chemical precipitants, solving the problem of large-scale generation of sodium ammonium-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of recycling and regenerating retired lithium-ion batteries, specifically to a method for stripping, leaching, and self-precipitation recycling of waste lithium-ion battery cathodes based on multi-stage plasma synergistic activation. Background Technology

[0002] Against the backdrop of energy structure transformation, lithium-ion batteries, due to their high energy density, rapid response, long lifespan, and complete industrial support, have become a key technological pillar for power system peak shaving, industrial and residential energy storage, and new energy vehicles. As the world's largest lithium battery producer, China has maintained a leading global production capacity over the past decade. In 2024, my country's total lithium-ion battery production reached 1170 GWh, a year-on-year increase of 24%, with the total industry output value exceeding 1.2 trillion yuan.

[0003] Lithium-ion batteries are mainly classified into lithium iron phosphate (LFP), ternary materials (NCM / NCA), lithium cobalt oxide (LCO), and lithium manganese oxide (LMO) based on their cathode materials. Lithium iron phosphate crystals are composed of PO4 tetrahedra linked by strong covalent PO bonds, a structure that endows them with excellent thermal stability. Due to their high safety, long cycle life (approximately 3000-6000 cycles), and significantly lower manufacturing cost compared to ternary materials (approximately 20%-40% lower), lithium iron phosphate is widely used in applications such as new energy vehicle power batteries, power grid and photovoltaic energy storage, and electric two-wheelers. As of 2024, lithium iron phosphate accounted for approximately 65%-70% of installed power batteries in China and holds a dominant position in the energy storage market.

[0004] Although lithium iron phosphate (LFP) batteries offer good safety and a long cycle life, the electrode materials inevitably undergo structural degradation and activity decline during long-term repeated charge-discharge cycles, leading to battery performance degradation and eventual disposal. Generally, the lifespan of LFP batteries is 6-8 years. With the accelerating pace of electronic product and electric vehicle upgrades, the number of retired batteries is growing rapidly, resulting in a massive amount of urban electronic waste. According to data released by EVTank, in 2024, my country's actual recycling volume of waste lithium-ion batteries was approximately 654,000 tons, of which approximately 400,000 tons were LFP batteries, accounting for 61.2%. It is projected that by 2030, the scale of waste lithium-ion battery recycling in my country will increase to approximately 4.246 million tons.

[0005] The environmental and resource risks posed by large-scale battery retirement cannot be ignored. Waste lithium iron phosphate batteries contain various harmful organic and inorganic components, such as organic carbonates, lithium hexafluorophosphate, and phosphorus from the materials. Improper disposal can lead to combustion, explosions, and soil and water pollution. Therefore, standardized recycling and treatment are crucial for public safety and ecological protection. Meanwhile, recycling has significant resource and climate benefits: lithium iron phosphate batteries contain approximately 2% lithium, and the accumulated amount during the upcoming retirement wave is considerable. Related research shows that compared to extracting lithium from ore, recycling lithium from waste batteries can significantly reduce greenhouse gas emissions (approximately 58%-81%), water consumption (approximately 72%-88%), and energy consumption (approximately 77%-89%). Given that lithium is widely recognized as an important strategic metal, systematic battery recycling can not only prevent the loss of huge amounts of raw materials but also provide cost flexibility for new battery production and bring considerable economic returns.

[0006] Currently, the main methods for recycling and regenerating spent lithium iron phosphate (LFP) cathode materials include pyrometallurgy, hydrometallurgy, and direct regeneration. In direct regeneration, the spent LFP cathode material is calcined together with a lithium source at high temperatures to compensate for lost lithium, repair damaged crystal structures, and restore its original electrochemical performance. Although the regenerated capacity of LFP can be partially restored, its electrochemical performance still cannot be compared with that of original LFP due to the lack of strict impurity control. In particular, precise replenishment of the stoichiometric content of lithium is required to compensate for lithium loss during multiple cycles, and the variation in lithium content from different sources increases the difficulty of lithiation to some extent. Pyrometallurgical processes are rarely studied for LFP recycling, as their combined energy consumption and equipment costs hinder their further application. Compared with pyrometallurgical processes, hydrometallurgical technology has now become the main recycling method for spent LFP batteries. Hydrometallurgy primarily employs oxidative acid leaching, which can effectively dissolve lithium from lithium iron phosphate batteries. However, this method requires large amounts of acid and oxidants, resulting in complex systems, poor selectivity, heavy wastewater treatment burdens, and insufficient utilization of the added value of iron and phosphorus resources. These issues limit its economic viability and sustainability in large-scale recycling of lithium iron phosphate batteries. Therefore, exploring efficient and green recycling strategies is crucial for maximizing economic value and minimizing environmental impact.

[0007] Plasma technology, with its high energy density, non-thermal equilibrium characteristics, and strong material activation capabilities, can significantly enhance mass transfer and reaction kinetics in metallurgical processes, reduce reaction temperature and energy consumption, and improve the selectivity of element transformation and separation in complex systems. Its good adaptability to complex raw materials and secondary resources makes it a promising candidate for applications in green metallurgy and resource recycling. Currently, there are no patents for the integrated application of plasma pretreatment with in-situ oxidation leaching and dilution precipitation in battery recycling. Summary of the Invention

[0008] This invention aims to provide a method for stripping, leaching, and self-precipitation recovery of waste lithium-ion battery cathodes based on multi-stage plasma synergistic activation. This method utilizes plasma synergistic stripping and leaching technology to achieve efficient and selective leaching of lithium from waste lithium-ion battery cathodes, overcoming the high energy consumption problem caused by long-term high-temperature calcination in traditional pretreatment processes. It also avoids the large-scale use of high-concentration acid and high-purity oxidants in traditional acid leaching processes. At the same time, lithium salts can be obtained through dilution precipitation without the use of chemical precipitants during the recovery of lithium salts, avoiding the discharge of sodium- and ammonium-containing wastewater.

[0009] This invention provides the following technical solution: A method for stripping, leaching, and self-precipitation recycling of waste lithium-ion battery cathodes based on multi-stage plasma synergistic activation, the method comprising the following steps: (1) Discharge and dismantling: After the waste lithium-ion battery is fully discharged, it is dismantled and the positive electrode is stripped off; (2) Stripping and activation of positive electrode powder: The positive electrode sheet is placed under plasma jet for treatment, and the activated waste positive electrode powder is scraped off from the positive electrode sheet; (3) Leaching: Ultrapure water is mixed with activated waste positive electrode powder to obtain a mixture. A regulator is added to adjust the mixture to a weakly acidic condition, and plasma discharge treatment is performed to obtain a solid-liquid mixture. The mixture is then filtered to obtain filter residue and filtrate. (4) Lithium recovery: Lithium salts are obtained by self-precipitation after diluting the filtrate; (5) Regeneration: The lithium salt, filter residue and reducing carbon source are mixed and calcined to obtain the regenerated lithium battery cathode material.

[0010] The technical principle of the method provided by this invention is as follows: In the pretreatment stage, the high temperature, physical bombardment, and ultraviolet radiation generated by plasma not only achieve the separation of aluminum foil and positive electrode powder in a short time, but also activate the positive electrode powder; In the leaching stage, the strong oxidizing substances such as ROS and RNS generated in situ during the plasma activation of water, along with the coupling effects of cavitation, shock waves, and ultraviolet radiation, provide an acidic leaching environment with dilute sulfuric acid, while also enhancing the conductivity of the solution. This allows for the efficient leaching of lithium from waste lithium iron phosphate batteries in a short time without additional heat sources, while iron remains in the precipitate; Subsequently, lithium salt precipitate can be formed by simply diluting the filtrate, without the need for additional chemical precipitants.

[0011] In step (1), the waste lithium-ion battery is a lithium iron phosphate battery.

[0012] In step (2), the input power of the plasma jet is 500-1500 W, and the plasma jet treatment lasts for 60-120 min.

[0013] In step (3), the regulator is selected from one or more combinations of sulfuric acid, nitric acid, or hydrochloric acid.

[0014] Preferably, the regulator is sulfuric acid, and the concentration of sulfuric acid in the mixture is 0.01-0.1 M.

[0015] In step (3), the solid-liquid ratio of the mixture is 10-100 g / L.

[0016] Preferably, the solid-liquid ratio of the mixture is 10-20 g / L.

[0017] In step (3), the lithium iron content in the collected filtrate is measured using inductively coupled plasma optical emission spectroscopy (ICP-OES), and the leaching rate of each element is calculated.

[0018] Furthermore, the plasma discharge treatment described in step (3) is selected from various discharge forms such as arc discharge, dielectric barrier discharge, and glow discharge. The interaction between plasma and water includes direct discharge in the liquid phase, gas phase discharge on the liquid surface, and discharge in a multiphase environment, such as discharge in bubbles within the liquid or contact with liquid spray, foam discharge, etc.

[0019] Furthermore, the gas used in the plasma discharge process described in step (3) is selected from one or more combinations of nitrogen, argon, oxygen, and air. In step (4), the filtrate is diluted with water and then self-precipitated to obtain lithium salt.

[0020] In step (5), the calcination procedure is to first pre-calcine at 350-450 ℃ for 2-5 h, and then calcine at 600-700 ℃ for 8-12 h, with a heating rate of 2-5 ℃ / min. The calcination atmosphere is argon or an argon-hydrogen mixture; the reducing carbon source can be glucose, sucrose or starch.

[0021] This invention first utilizes the high temperature, physical bombardment, and ultraviolet radiation generated by plasma jet to achieve the separation of aluminum foil and positive electrode powder and the activation and oxidation of the positive electrode powder. Subsequently, under acidic conditions, the strong oxidizing substances (such as ROS and RNS) generated during the activation of water by plasma jet are utilized, along with cavitation, shock wave, and ultraviolet coupling effects, to achieve selective leaching of lithium elements in waste lithium-ion battery positive electrode materials.

[0022] The method provided by this invention combines plasma technology with the recycling of waste lithium battery cathodes, and designs a closed-loop wet recycling process. While reducing energy consumption in the pretreatment stage, it can also significantly reduce the amount of acid used in the leaching stage without the need for additional oxidants, thus reducing the cost of raw materials and reagents. In the subsequent lithium salt recycling process, no chemical precipitants are required, and sodium-free wastewater discharge is achieved. This further reduces the overall cost of lithium battery recycling and regeneration and the environmental burden, and is currently a research hotspot in this field.

[0023] Compared with the prior art, the present invention has the following advantages: This invention utilizes plasma jet treatment of the positive electrode sheet to achieve separation of aluminum foil and positive electrode powder in a short time, while also activating the positive electrode powder. This not only improves the high energy consumption problem of traditional pretreatment steps, but also reduces the amount of subsequent oxidative leaching acid used. By utilizing the strong oxidizing substances (such as ROS and RNS) induced in situ during plasma activation of water under acidic conditions, and combining the cavitation, shock wave, and ultraviolet radiation generated by the plasma discharge process, the crystal structure of the cathode material is disrupted. This achieves highly efficient and selective leaching of lithium from spent lithium-ion battery cathode materials, avoiding the use of high-purity solid oxidants (such as sodium persulfate) and liquid oxidants (such as hydrogen peroxide), and significantly reducing acid usage, thus lowering production costs, enhancing safety, and facilitating subsequent lithium separation and purification. Iron is retained in the solid, facilitating subsequent element separation and extraction, and also significantly reducing the discharge of soluble cation wastewater. The lithium precipitation process only requires dilution to obtain white lithium salt precipitate, without the need for chemical precipitants, which reduces the cost of the precipitation process. It also achieves zero discharge of wastewater containing sodium and ammonium ions during the precipitation process, thereby further reducing the cost of lithium iron phosphate material recycling and regeneration. It realizes a closed-loop process, avoids environmental pollution and resource waste, meets green environmental protection requirements, and reduces the overall energy consumption and cost of recycling and regeneration. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the specific process of stripping, leaching, and self-precipitation recovery method for waste lithium-ion battery cathodes based on multi-level plasma synergistic activation in the embodiments. Figure 2 A comparison of energy consumption between plasma jet impact exfoliation activation pretreatment and muffle furnace high-temperature calcination pretreatment; Figure 3 The diagram shows the effects of plasma jet impact stripping activation pretreatment and muffle furnace high-temperature calcination pretreatment. Figure 4 The leaching rate of lithium iron element under different solid-liquid ratios in Example 1; Figure 5This is a comparison of the lithium iron leaching rate after leaching with sulfuric acid (0.01 M dilute sulfuric acid) for 35 min under the solid-liquid ratio of 60 g / L in Example 1 and without plasma. Figure 6 The EPR spectrum of ROS, the main strong oxidizing agent, after 5 minutes of plasma leaching in Example 1 is shown below. Figure 7 This is an experimental result diagram of lithium precipitation by dilution method in Example 1; Figure 8 The electrochemical data are for the regenerated lithium iron phosphate in Example 1. Detailed Implementation

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1 like Figure 1 As shown, the waste lithium battery cathode stripping, leaching, and self-precipitation recycling method based on multi-stage plasma synergistic activation provided in this embodiment specifically includes the following steps: (1) Discharge and disassembly: Use a charge-discharge tester to discharge the waste lithium battery with a current of 1 A until the voltage drops to 2 V. Then, place the battery in a glove box for disassembly and peel off the positive electrode. (2) Stripping and activation of positive electrode powder: The positive electrode sheet was placed under a plasma jet for 90 min and the input power of the plasma was controlled at 1.5 kW. Then, the activated positive electrode powder was gently scraped off with a spatula. (3) Leaching: After uniformly mixing ultrapure water and positive electrode powder, sulfuric acid solution is added dropwise to ensure that the sulfuric acid concentration in the slurry is 0.01 M. Mix uniformly again and control the solid-liquid ratio to be 10 g / L, 20 g / L, 40 g / L, 60 g / L, 80 g / L and 100 g / L respectively. After placing the magnetic particle, transfer the beaker filled with slurry to the plasma reactor, connect the gas path, introduce oxygen into the reactor, and then start the plasma reactor. Set the rotation speed to 400 rpm and start timing. After the reaction time is 30 min, turn off the plasma device, filter and wash the solid-liquid mixture in the beaker to obtain dark filter residue and filtrate, and send samples for testing. (4) Lithium recovery: Dilute the obtained filtrate with water and a white precipitate will gradually form. After the precipitate is completely formed, filter it and wash the precipitate thoroughly to obtain clean lithium salt. (5) Regeneration of the positive electrode: The obtained white lithium salt and dark filter residue were dried completely in a vacuum oven at 60 °C. Then, the lithium salt, dark residue and 5 wt% glucose (Li / Fe=1.05) were mixed evenly and placed in a tube furnace filled with argon-hydrogen mixture (5% hydrogen) for pre-calcination at 350 °C for 5 h and then calcined at 650 °C for 10 h to obtain the regenerated lithium battery positive electrode material.

[0027] Testing and characterization: The lithium iron content in LiFePO4 and the leachate was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the test results are shown in Table 1 and Table 2.

[0028] Figure 2 This indicates that the energy consumption of plasma jet impact stripping activation pretreatment is significantly lower than that of traditional muffle furnace high-temperature calcination pretreatment (muffle furnace high-temperature calcination pretreatment is 500 ℃ for 4 h, muffle furnace power is 3.5 kW).

[0029] at the same time Figure 3 The images show the effects of plasma jet impact exfoliation activation pretreatment and muffle furnace high-temperature calcination pretreatment. Figure 3 It can be seen that neither method can achieve delamination if the power or temperature is too low, while excessively high power or temperature will cause the electrode to break easily. Figure 3 In the diagram, (a)-(c) represent the plasma jet impact ablation activation pretreatment. Figure 3 (d)-(f) in the figure represent the high-temperature calcination pretreatment in a muffle furnace (generally using an argon atmosphere, but the stripping effect is similar to that in this case, so it is placed in an air atmosphere). Figure 4 The leaching rate of lithium iron phosphate in Example 1 is shown, i.e., the leaching rate of each element as a function of the solid-liquid ratio under the same gas flow rate and leaching time conditions. During the experiment, the leaching time was set to 30 min, and the solid-liquid ratio of the waste cathode material to the dilute sulfuric acid solution ranged from 10 g / L to 100 g / L. Figure 4 As can be seen, with the increase of the solid-liquid ratio, the leaching rate of lithium shows a decreasing trend, while the leaching rate of iron remains basically unchanged, with both leaching rates ≤0.05%, which demonstrates that the method has extremely high selectivity.

[0030] Figure 5 The leaching effects of plasma-activated water method and sulfuric acid leaching method under the same working conditions were demonstrated. It can be seen that the leaching rate of lithium using plasma-activated water method is significantly higher than that of sulfuric acid leaching alone, while the leaching rate of iron is much lower than that of sulfuric acid leaching method. This shows that the leaching method used in this invention has selectivity and high efficiency.

[0031] Figure 6This indicates that after the plasma equipment is started, a large amount of highly oxidizing substances such as ROS are generated in the leaching liquid. Among them, (a) is hydroxyl radical, (b) is superoxide radical, and (c) is singlet oxygen.

[0032] Figure 7 A large amount of white precipitate was produced after diluting the filtrate with water.

[0033] like Figure 8 As shown, the 1C discharge specific capacity is 140.65 mAh g. -1 The capacity retention rate after 100 laps is 99.9%.

[0034] Table 1 shows the content (mass percentage) of lithium and iron in the lithium iron phosphate used in the examples.

[0035] Table 1. Lithium iron content of lithium iron phosphate used in the examples

[0036] Table 2 shows the inductively coupled plasma optical emission spectrometry (ICP-OES) characterization data of the leachate obtained in Example 1, demonstrating the content of lithium and iron in the leachate obtained by the waste lithium battery cathode stripping leaching and self-precipitation recovery method based on multi-level plasma synergistic activation.

[0037] Table 2. Lithium iron content in the leachate obtained in Example 1

[0038] Table 3 shows the leaching rates of lithium and iron under different operating conditions obtained by the waste lithium battery cathode stripping leaching and self-precipitation recovery method based on multi-stage plasma synergistic activation in Example 1.

[0039] Table 3. Lithium iron leaching rate in Example 1

[0040] The results show that this invention can achieve efficient leaching of lithium, a valuable metal element, from spent lithium-ion batteries while retaining iron in the precipitate, without introducing other impurity cations. This indicates that the waste lithium-ion battery cathode stripping, leaching, and self-precipitation recovery method based on multi-stage plasma synergistic activation can not only efficiently leach valuable lithium with extremely low acid consumption while retaining iron in the solid, but also achieve lithium dilution and precipitation without additional chemical precipitants, reducing purification costs and generating no soluble cationic wastewater. This provides a strong technical guarantee for the efficient, economical, and green recycling of waste cathode materials.

[0041] The core technical idea of ​​the above embodiment is as follows: First, the waste lithium-ion battery positive electrode sheet is obtained by dismantling the battery; then, the positive electrode powder is separated from the aluminum foil by activating the material with plasma jet and destroying the PVDF binder in the positive electrode sheet; then, the lithium element in the waste lithium iron phosphate is selectively leached by the strong oxidizing substance generated in situ during the plasma activation of water; then, the white lithium salt precipitate is obtained by adding excess water to the filtrate; the dried dark solid residue and white lithium salt are mixed with 5 wt% glucose in a certain proportion, and pre-calcined at 350°C for 5 h in a tube furnace filled with argon-hydrogen mixture, and then calcined at 650°C for 10 h to obtain regenerated lithium iron phosphate.

[0042] The method provided by this invention is energy-saving and environmentally friendly, reducing energy consumption and the use of chemical reagents, and decreasing wastewater generation and environmental impact. The method also improves economic efficiency and reduces resource waste.

[0043] The above embodiments are only used to explain the inventive concept of the present invention, and are not intended to limit the protection of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical and methodological essence of the present invention shall still fall within the scope of the technical and methodological solutions of the present invention.

Claims

1. A method for stripping, leaching, and self-precipitation recovery of waste lithium-ion battery cathodes based on multi-stage plasma synergistic activation, characterized in that, The method includes the following steps: (1) Discharge and dismantling: After the waste lithium-ion battery is fully discharged, it is dismantled and the positive electrode is stripped off; (2) Stripping and activation of positive electrode powder: The positive electrode sheet is placed under plasma jet for treatment, and the activated waste positive electrode powder is scraped off from the positive electrode sheet; (3) Leaching: Ultrapure water is mixed with activated waste positive electrode powder to obtain a mixture. A regulator is added to adjust the mixture to a weakly acidic condition, and plasma discharge treatment is performed to obtain a solid-liquid mixture. The mixture is then filtered to obtain filter residue and filtrate. (4) Lithium recovery: Lithium salts are obtained by self-precipitation after diluting the filtrate; (5) Regeneration: The lithium salt, filter residue and reducing carbon source are mixed and calcined to obtain the regenerated lithium battery cathode material.

2. The method according to claim 1, characterized in that, In step (1), the waste lithium-ion battery is a lithium iron phosphate battery.

3. The method according to claim 1, characterized in that, In step (2), the input power of the plasma jet is 500-1500 W, and the plasma jet treatment lasts for 60-120 min.

4. The method according to claim 1, characterized in that, In step (3), the regulator is selected from one or more combinations of sulfuric acid, nitric acid, or hydrochloric acid.

5. The method according to claim 4, characterized in that, The regulator is sulfuric acid, and the concentration of sulfuric acid in the mixture is 0.01-0.1 M.

6. The method according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the mixture is 10-100 g / L.

7. The method according to claim 1, characterized in that, The solid-liquid ratio of the mixture is 10-20 g / L.

8. The method according to claim 1, characterized in that, In step (4), the filtrate is diluted with water and then self-precipitated to obtain lithium salt.

9. The method according to claim 1, characterized in that, In step (5), the calcination procedure is to first precalcine at 350-450 ℃ for 2-5 h, and then calcine at 600-700 ℃ for 8-12 h, with a heating rate of 2-5 ℃ / min.

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