A method for recycling waste lithium batteries

Abstract

The present invention discloses a regeneration method for waste lithium batteries. The regeneration method comprises the following steps: (1) configuring a lithium source into a lithium source solution, and then adding an oxidant to the lithium source solution to obtain a mixed solution; (2) mixing the powder of the waste lithium battery and the mixed solution in step (1), heating and reacting at 80-120°C, and drying after the reaction to obtain a regeneration precursor; (3) mixing the regeneration precursor with lithium carbonate and calcining to obtain a regenerated lithium battery. In the regeneration method for waste lithium batteries provided by the present invention, the temperature required for the hydrothermal reaction is significantly reduced by adding an oxidant, realizing the low-temperature direct regeneration of waste lithium batteries, and solving the disadvantage of high energy consumption in traditional hydrothermal regeneration.

Description

Technical Field

[0001] The present invention relates to the field of recycling and reuse of waste lithium-ion batteries, and particularly to a regeneration method for waste lithium batteries. Background Art

[0002] Due to the advantages of high voltage platform and strong adaptability to high and low temperatures, lithium-ion batteries have become the core force supporting the transformation of clean energy and the development of energy storage technologies. Taking the new energy vehicle industry as an example, according to the early estimated scrapping cycle of power batteries of 6-8 years, the first wave of power battery retirements is currently underway. From an environmental perspective, if waste lithium batteries are not properly disposed of, serious environmental pollution problems will exist. Substances such as lithium, nickel, cobalt, manganese, and fluorine in lithium battery cathode materials have high biological toxicity and the fatal defect of being extremely difficult to decompose naturally. If not properly disposed of, it will bring major environmental pollution problems. From an economic perspective, China's global share of lithium ore, cobalt ore, and nickel ore resources is less than 5% (only 1% and 1.95% for lithium ore and cobalt ore, and 4.39% for nickel ore), and non-ferrous metal resources are severely scarce, relying entirely on overseas imports. The content of rare metals and non-ferrous metals in waste lithium batteries is much higher than that of primary ores. If waste batteries are not recycled and regenerated, serious resource waste will occur. Therefore, the recycling and regeneration of waste lithium batteries is of great significance.

[0003] Currently, the main recycling and regeneration technologies in industry are pyrometallurgy and hydrometallurgy. Pyrometallurgy generally uses vacuum calcination or calcination with a reducing agent (graphite obtained from the negative electrode) on the disassembled and pulverized waste cathode material at temperatures above 1200°C to recover valuable metals in the waste powder in the form of oxides or alloys; hydrometallurgy is to leach the target metals in the waste cathode material with acid or alkali, and then through steps such as precipitation, extraction, and purification to achieve the extraction of the target metals, thereby obtaining oxides of the target metals. The two recycling methods have obvious disadvantages such as high energy consumption, long recycling cycle, high environmental toxicity, and poor economy. For example, in the Chinese patent with the publication number CN117352889A, after acid leaching the waste lithium iron phosphate cathode material, a displacement reaction occurs with ferric chloride solution, the generated ferric chloride precipitate is calcined to generate chlorine gas which is introduced into water to produce acid solution, the generated lithium phosphate solution reacts with the cathode, and it is soaked and calcined with an organic solution. The whole process involves multiple calcination processes, with extremely high energy consumption and the generation of chlorine gas, making it prone to safety accidents.

[0004] Compared with the above two methods, the direct regeneration method is more in line with the principle of energy conservation and emission reduction. Direct regeneration refers to directly repairing the damaged electrode material without destroying the electrode material, making it a new electrode material that can be used normally. The most industrially promising direct regeneration method is the hydrothermal method, which involves mixing the waste cathode material with a lithium source solution of a certain concentration, loading it into a high-pressure reaction kettle, heating it at a certain temperature and pressure, and then obtaining the regenerated cathode material after annealing.

[0005] The traditional hydrothermal method requires a high temperature above 200 °C and needs to be carried out in a high-pressure reaction kettle, which greatly increases the industrial cost and risk. For example, in the Chinese patent with the publication number CN117286574A, the waste lithium manganese oxide cathode material is dispersed in a high-boiling organic solvent, and then a hydrothermal reaction is carried out with a lithium source and a reducing agent. The relithiated lithium manganese oxide powder is ball-milled with a lithium source and ethanol and then dried, and the dried material is calcined in an air atmosphere to obtain regenerated lithium manganese oxide powder. Among them, the hydrothermal process requires a high temperature of 130-180 °C, and 10-20 mL of organic solvent is required for the regeneration of each gram of waste lithium manganese oxide, and the economic benefit is not obvious. For another example, Yang Shi et al. used 4M lithium hydroxide solution to regenerate waste layered cathode materials lithium cobalt oxide and lithium nickel cobalt manganese oxide in a high-pressure reaction kettle at a temperature of 220 °C. The maximum pressure during the heating process can reach 25 bar, and the capacity and cycle stability of the regenerated material are improved. At present, there is no method that can effectively carry out hydrothermal regeneration at low temperature and normal pressure.

[0006] There are mainly three reasons for the damage of the lithium battery cathode material, namely the loss of lithium ions, the mixing of other metal ions and lithium ions, and oxygen loss. Taking the ternary lithium cathode material as an example, during the charging and discharging process of the battery, some lithium ions will enter the electrolyte and the negative electrode, and because the divalent nickel ions and lithium ions have similar volumes, the lithium ions will be mixed with the divalent nickel ions in the positive electrode during insertion and extraction, resulting in the collapse of the layered structure of the ternary lithium material, hindering the movement of lithium ions between the positive and negative electrodes, and causing the attenuation of the battery capacity. The general hydrothermal method is to use a high-concentration lithium source and a high-temperature environment to supplement some lithium ions into the waste ternary lithium, and then repair the collapsed layered structure and supplement lithium again through the annealing process. This process has high energy consumption and low lithium supplementation efficiency.

[0007] Therefore, how to reduce the energy consumption in the lithium battery regeneration process and improve the lithium supplementation efficiency is a research hotspot in this field at present. Summary of the Invention

[0008] The purpose of the present invention is to provide a regeneration method for waste lithium batteries. In the regeneration method provided by the present invention, the addition of an oxidant greatly reduces the temperature required for the hydrothermal reaction, realizes the low-temperature direct regeneration of waste lithium batteries, and solves the disadvantage of high energy consumption in traditional hydrothermal regeneration.

[0009] The present invention provides the following technical solutions:

[0010] A regeneration method for waste lithium batteries, the regeneration method comprising the following steps:

[0011] (1) Prepare a lithium source solution with a lithium source, and then add an oxidant to the lithium source solution to obtain a mixed solution;

[0012] (2) Mix the powder of the waste lithium battery and the mixed solution in step (1), heat and react at 60 - 100 °C, and obtain the regenerated precursor after drying the reaction.

[0013] (3) Mix the regenerated precursor with lithium carbonate and then calcine to obtain the regenerated lithium battery.

[0014] In the present invention, by adding different oxidants to the lithium source solution and uniformly mixing with the waste cathode / anode materials, and through steps such as co-hydrothermal treatment, drying, and annealing, the low-temperature direct regeneration of the waste cathode / anode materials of the lithium battery is realized.

[0015] The technical concept of the present invention is as follows: Firstly, obtain pure waste lithium battery cathode / anode through pretreatment, then use low-temperature hydrothermal treatment with added oxidant to supplement lithium for it, and finally perform structure repair on it through short-term annealing to obtain the regenerated cathode / anode materials with high capacity and high cycle stability. The present invention regenerates and utilizes waste lithium batteries, which not only avoids waste of resources, but also basically does not produce waste liquid during the regeneration process, being green and environmentally friendly. At the same time, the addition of the oxidant greatly reduces the temperature required for the hydrothermal reaction, solves the disadvantage of high energy consumption in traditional hydrothermal regeneration, effectively reduces the regeneration cost, and has good economic benefits.

[0016] Further, in step (1), the oxidant is selected from one or a combination of at least two of nitric acid, hypochlorous acid, peracetic acid, or potassium permanganate.

[0017] The technical principle of the present invention using the oxidant is as follows: Taking other metal ions as nickel ions as an example, through the lithium source plus the oxidant, divalent nickel is oxidized to trivalent nickel during the hydrothermal process, avoiding the mixed arrangement of divalent nickel ions and lithium ions, and leaving oxygen vacancies. Since the lithium content of the ternary lithium material cannot be completely restored during the hydrothermal process, the presence of trivalent nickel can also keep the potential balanced. In this way, during the subsequent annealing process, while continuing to supplement lithium ions, oxygen ions are also supplemented, further repairing the layered structure. This method can not only be applied to ternary lithium materials, but also has a similar repair effect on materials such as lithium iron phosphate, lithium manganate, and lithium cobaltate.

[0018] Further preferably, the oxidant is peracetic acid, and heat and react at 80 - 100 °C, and the regenerated lithium battery has better capacity and cycle stability.

[0019] Further, in step (1), the addition amount of the oxidant is 1 - 5% of the lithium source solution, and the percentage is by volume. In the present invention, the concentration of lithium ions in the lithium source solution is flexibly adjusted according to actual needs and the type of lithium source, so it is not limited.

[0020] Further, in step (1), the lithium source is selected from one or a combination of at least two of anhydrous lithium acetate, lithium nitrate, lithium chloride, or lithium permanganate.

[0021] Further, in step (2), the heating reaction time is 6 - 10 h.

[0022] Further, in step (3), the calcination temperature is 750 - 950 °C, and the calcination time is 2 - 6 h.

[0023] Further, in step (3), the calcination is carried out in an oxygen atmosphere.

[0024] In the present invention, the used lithium - ion batteries are discharged, disassembled, rinsed, soaked, centrifuged, and dried to obtain used powders.

[0025] Further, the used lithium - ion batteries are ternary lithium, lithium iron phosphate, lithium manganate, or lithium cobaltate.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The regeneration method provided by the present invention can promote the replenishment of lithium ions by directly changing the valence of other metals except lithium in the cathode material of lithium - ion batteries, and this process is carried out simultaneously with the lithium - replenishing process without the need to add additional equipment. Compared with the current regeneration methods that offset the adverse effects brought by the change of metal ion valence by increasing the lithium source concentration or raising the reaction temperature or time, the present invention is more targeted.

[0028] (2) The regeneration method provided by the present invention can significantly reduce the hydrothermal reaction temperature, enabling it to be carried out at a temperature of 60 - 100 °C without the need for additional pressure to prevent solution evaporation. Compared with the temperature above 200 °C in the current regeneration methods, it has a significant effect of reducing energy consumption.

[0029] (3) The solution used in the regeneration process of the regeneration method provided by the present invention can be recycled, and the utilization rate of used lithium - ion batteries can reach 100%. Compared with the current situation of the recycling process being in deficit, it has significant economic advantages.

[0030] (4) The regenerated lithium - ion batteries prepared by the regeneration method provided by the present invention have more excellent electrochemical performance. Description of the Drawings

[0031] Figure 1 It is the specific flowchart of the regeneration method of the used lithium - ion batteries provided for the examples;

[0032] Figure 2 It is the cycle performance diagram of the regenerated ternary lithium and the used ternary lithium obtained in Example 1 at a current of 1 C, where the charge - discharge voltage range is 2.8 V - 4.3 V;

[0033] Figure 3To obtain the cycling performance graph of recycled ternary lithium and waste ternary lithium at a current of 1C in Example 2, where the charge-discharge voltage range is 2.8V - 4.3V;

[0034] Figure 4 To obtain the cycling performance graph of recycled ternary lithium and waste ternary lithium at a current of 1C in Example 3, where the charge-discharge voltage range is 2.8V - 4.3V;

[0035] Figure 5 To obtain the cycling performance graph of recycled ternary lithium and waste ternary lithium at a current of 1C in Example 4, where the charge-discharge voltage range is 2.8V - 4.3V;

[0036] Figure 6 To obtain the specific capacity-voltage graph of recycled ternary lithium and waste ternary lithium at a current of 0.1C in Example 1, where the charge-discharge voltage range is 2.8V - 4.3V;

[0037] Figure 7 To obtain the X-ray diffraction pattern of recycled ternary lithium in Example 1. Detailed implementation mode

[0038] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] As Figure 1 shown, the recycling method of waste lithium batteries provided in this embodiment specifically includes the following steps:

[0041] (1) Pretreatment: Immerse the waste lithium battery in a 5wt% sodium chloride aqueous solution for discharging, and the discharging time is 12h until the voltage drops to about 2V. Then disassemble the glass to take out the positive electrode plate, and thoroughly rinse it with dimethyl carbonate (>99%). Immerse it in N-methylpyrrolidone at 50°C for 30 min, and remove the active material, binder, and carbon black from the aluminum substrate by ultrasonic treatment and scraping. After centrifuging the suspension at 3500 rpm for 5 min, the active material is precipitated. The precipitate is washed several times with N-methylpyrrolidone, and then the active material is collected and vacuum dried at 80°C for 12h to obtain waste positive electrode powder.

[0042] (2) Prepare the solution: First, add equal amounts of peracetic acid solution A and B to a container, mix them evenly, and then let them stand at 15 - 25°C for 24 - 48h to activate and generate peracetic acid solution. Then, weigh anhydrous lithium acetate (>99%) according to the standard of 4mol / L lithium ion content, and pour it into ultrapure water to prepare 24ml lithium acetate solution. Finally, add 1ml peracetic acid solution to the lithium acetate solution according to a volume fraction of 4%, and the solution required for the hydrothermal reaction can be obtained.

[0043] (3) Hydrothermal reaction: Weigh 1 g of the waste powder obtained in step (1) and pour it into the solution prepared in step (2). Oscillate it with a vortex mixer for 5 min and then sonicate it for 10 min to obtain a uniformly mixed liquid. Pour the mixed liquid into a reaction kettle and heat it in an oven at 80 °C with sealing for 8 h. After cooling to room temperature, centrifuge the solution at 8500 rpm for 5 min and dry it at 120 °C for 12 h to obtain a regenerated precursor.

[0044] (4) Annealing: Weigh the mass of the regenerated precursor and weigh lithium carbonate (>99%) solid in an excess proportion of 5%. Pour the two into an agate mortar and grind them evenly. Then pour them into a corundum boat and heat them in a tube furnace at 850 °C for 4 h. After cooling, the regenerated cathode powder is obtained.

[0045] (5) Testing: Characterize the regenerated cathode material, including XRD and SEM. At the same time, assemble the regenerated cathode material into a coin-type half-cell and conduct charge-discharge tests. The charge-discharge voltage range is 2.8 V - 4.3 V, and the test current densities are 0.1 C and 1 C.

[0046] Example 2

[0047] (1) Pretreatment: Immerse the waste lithium battery in a 5 wt% sodium chloride aqueous solution for discharging. The discharging time is 12 h until the voltage drops to about 2 V. Then disassemble the glass to take out the cathode plate, thoroughly rinse it with dimethyl carbonate (>99%), soak it in N-methylpyrrolidone at 50 °C for 30 min, and remove the active material, binder, and carbon black from the aluminum substrate by ultrasonic treatment and scraping. After centrifuging the suspension at 3500 rpm for 5 min, precipitate the active material. Wash the precipitate with N-methylpyrrolidone several times, and then collect the active material and vacuum-dry it at 80 °C for 12 h to obtain waste cathode powder.

[0048] (2) Solution preparation: Weigh lithium nitrate (>99%) according to the standard of a lithium ion content of 4 mol / L and pour it into ultrapure water to prepare 24.5 ml of lithium nitrate solution. Finally, add 0.5 ml of nitric acid solution (25%) to the lithium nitrate solution according to a volume fraction of 2% to obtain the solution required for the hydrothermal reaction.

[0049] (3) Hydrothermal reaction: Weigh 1 g of the waste powder obtained in step (1) and pour it into the solution prepared in step (2). Oscillate it with a vortex mixer for 5 min and then sonicate it for 10 min to obtain a uniformly mixed liquid. Pour the mixed liquid into a reaction kettle and heat it in an oven at 60 °C with sealing for 10 h. After cooling to room temperature, centrifuge the solution at 8500 rpm for 5 min and dry it at 120 °C for 12 h to obtain a regenerated precursor.

[0050] (4) Annealing: Weigh the mass of the regenerated precursor, weigh lithium carbonate (>99%) solid in an excess of 5%, pour the two into an agate mortar and grind them evenly, then pour them into a corundum boat and heat them in a tube furnace at 850 °C for 6 h. After cooling, the regenerated cathode powder is obtained.

[0051] (5) Testing: Characterize the regenerated cathode material, including XRD and SEM. At the same time, assemble the regenerated cathode material into a coin-type half-cell and conduct charge-discharge tests. The charge-discharge voltage range is 2.8 V - 4.3 V, and the test current densities are 0.1 C and 1 C.

[0052] Example 3

[0053] (1) Pretreatment: Immerse the used lithium battery in a 5 wt% aqueous sodium chloride solution for discharging. The discharging time is 12 h until the voltage drops to about 2 V. Then disassemble the glass to take out the cathode plate, thoroughly rinse it with dimethyl carbonate (>99%), soak it in N-methylpyrrolidone at 50 °C for 30 min, and remove the active material, binder, and carbon black from the aluminum substrate by ultrasonic treatment and scraping. After centrifuging the suspension at 3500 rpm for 5 min, the active material precipitates. The precipitate is washed several times with N-methylpyrrolidone, and then the active material is collected and vacuum-dried at 80 °C for 12 h to obtain the used cathode powder.

[0054] (2) Solution preparation: First, add equal amounts of peracetic acid solution A and B to a container, mix them evenly, and then let them stand at 15 - 25 °C for 24 - 48 h to activate and generate peracetic acid solution. Then, weigh lithium chloride (>99%) according to the standard of 4 mol / L lithium ion content, pour it into ultrapure water to prepare 24 ml of lithium chloride solution. Finally, add 1 ml of peracetic acid solution dropwise to the lithium acetate solution according to a volume fraction of 4% to obtain the solution required for the hydrothermal reaction.

[0055] (3) Hydrothermal reaction: Weigh 1 g of the used powder obtained in step (1), pour it into the solution prepared in step (2), oscillate it with a vortex mixer for 5 min, and then ultrasonicate it for 10 min to obtain a uniformly mixed liquid. Pour the mixed liquid into a reaction kettle, heat it in an oven at 100 °C with the lid closed and maintain it for 6 h. After cooling to room temperature, centrifuge the solution at 8500 rpm for 5 min and dry it at 100 °C for 12 h to obtain the regenerated precursor.

[0056] (4) Annealing: Weigh the mass of the regenerated precursor, weigh lithium carbonate (>99%) solid in an excess of 5%, pour the two into an agate mortar and grind them evenly, then pour them into a corundum boat and heat them in a tube furnace at 850 °C for 4 h. After cooling, the regenerated cathode powder is obtained.

[0057] (5) Testing: Characterize the recycled cathode material, including XRD and SEM. At the same time, assemble the recycled cathode material into a coin-type half-cell and conduct charge-discharge tests. The charge-discharge voltage range is 2.8V - 4.3V, and the test current densities are 0.1C and 1C.

[0058] Example 4

[0059] (1) Pretreatment: Immerse the used lithium battery in a 5wt% aqueous sodium chloride solution for discharging. The discharging time is 12h until the voltage drops to about 2V. Then disassemble the glass to take out the cathode plate, thoroughly rinse it with dimethyl carbonate (>99%), soak it in N-methylpyrrolidone at 50°C for 30min, and remove the active material, binder, and carbon black from the aluminum substrate by ultrasonic treatment and scraping. After centrifuging the suspension at 3500 rpm for 5 min, precipitate the active material. Wash the precipitate with N-methylpyrrolidone several times, and then collect the active material and vacuum dry it at 80°C for 12h to obtain the used cathode powder.

[0060] (2) Prepare the solution: Weigh lithium manganate (>99%) according to the standard of a lithium ion content of 4mol / L and pour it into ultrapure water to prepare 24.5ml of lithium manganate solution. Finally, add 0.5ml of potassium permanganate solution (5%) dropwise to the lithium manganate solution according to a volume fraction of 2% to obtain the solution required for the hydrothermal reaction.

[0061] (3) Hydrothermal reaction: Weigh 1g of the used powder obtained in step (1) and pour it into the solution prepared in step (2). Oscillate it with a vortex mixer for 5min and then ultrasonicate it for 10min to obtain a uniformly mixed liquid. Pour the mixed liquid into a reaction kettle, heat it in an oven at 100°C with the lid closed and maintain for 8h. After cooling to room temperature, centrifuge the solution at 8500rpm for 5min and dry it at 80°C for 12h to obtain the recycled precursor.

[0062] (4) Annealing: Weigh the mass of the recycled precursor, weigh lithium carbonate (>99%) solid in an excess of 5%, pour the two into an agate mortar and grind them evenly, then pour them into a corundum boat and heat them in a tubular furnace at 850°C for 4h. After cooling, the recycled cathode powder is obtained.

[0063] (5) Testing: Characterize the recycled cathode material, including XRD and SEM. At the same time, assemble the recycled cathode material into a coin-type half-cell and conduct charge-discharge tests. The charge-discharge voltage range is 2.8V - 4.3V, and the test current densities are 0.1C and 1C.

[0064] In the above examples, the selection of the lithium source, oxidant, and reaction temperature and duration has a great influence on the specific capacity of the recycled ternary lithium and the material morphology.

[0065] Figure 7The X-ray diffraction pattern of the regenerated ternary lithium material prepared in Example 1 can reflect that the prepared composite material has a high crystallinity.

[0066] Figures 2 - 5 They are the cycling performance diagrams of the regenerated ternary lithium and the waste ternary lithium obtained in Examples 1-4 under a current of 1C, where the charge-discharge voltage range is 2.8V-4.3V; it can be seen that compared with the waste lithium battery, the discharge specific capacity of the regenerated ternary lithium has been greatly improved, and it basically does not decay after cycling, indicating that the regeneration process has realized lithium compensation and structure repair of the waste lithium battery to a certain extent.

[0067] Figure 6 It is the specific capacity-voltage diagram of the regenerated ternary lithium and the waste ternary lithium obtained in Example 1 under a current of 0.1C, where the charge-discharge voltage range is 2.8V-4.3V; it can be seen that the regenerated ternary lithium can continuously discharge for a long time at a voltage of 3.7V, which is basically the same as that of the commercial-grade ternary lithium.

[0068] In summary, the regeneration method provided by the present invention has a simple and feasible regeneration strategy for the cathode material of waste lithium batteries and is applicable to the regeneration of various cathode or anode materials. The regeneration method provided by the present invention has both repair effect and economic effect during the regeneration process and has broad application prospects.

Claims

1. A method for recycling waste lithium batteries, characterized in that, The regeneration method includes the following steps: (1) Configure the lithium source into a lithium source solution, and then add peracetic acid as an oxidant to the lithium source solution to obtain a mixed solution; (2) Mix the positive electrode powder of the used ternary lithium battery with the mixed solution in step (1), heat and react at 80 - 100 °C, and dry after the reaction to obtain a regenerated precursor; (3) Mix the regenerated precursor with lithium carbonate and calcine to obtain a regenerated lithium battery; In step (1), the addition amount of the oxidant is 1 - 5% of the volume fraction of the lithium source solution.

2. The regeneration method of waste lithium batteries according to claim 1, characterized in that, In step (1), the lithium source is selected from one or a combination of at least two of lithium acetate anhydrous, lithium nitrate, lithium chloride, or lithium permanganate.

3. The regeneration method of waste lithium batteries according to claim 1, characterized in that, In step (2), the heating reaction time is 6 - 10 h.

4. The regeneration method of waste lithium batteries according to claim 1, characterized in that, In step (3), the calcination temperature is 750 - 950 °C, and the calcination time is 2 - 6 h.

5. The regeneration method of waste lithium batteries according to claim 1, wherein, After the used lithium battery is discharged, disassembled, rinsed, soaked, centrifuged, and dried, the positive electrode powder of the used ternary lithium battery is obtained.

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