A method for electrolytic recovery and reuse of waste lithium-rich manganese-based positive electrode materials

Abstract

The present invention belongs to the field of metal recovery by electrolysis and discloses a method for the electrolytic recovery and reuse of waste lithium-rich manganese-based positive electrode materials. The method comprises the following steps: first, delithiation of the lithium-rich manganese-based positive electrode materials of waste lithium-ion batteries is performed by electrolysis driven by an electric field, followed by annealing the delithiation-induced lithium-rich manganese-based positive electrode materials to obtain a manganese-based composite oxide that can be used as a positive electrode material for aqueous zinc-ion batteries; and finally, the delithiation-induced lithium ions are precipitated and recovered by adding a precipitant. The method of the present invention effectively recovers lithium while obtaining a manganese-based composite oxide that can be used as a positive electrode material for aqueous zinc-ion batteries. The method is simple in process and easy to implement, making it suitable for widespread application.

Description

Technical Field

[0001] The present invention belongs to the field of metal recovery by electrolysis, and specifically relates to a method for electrolytic recovery and reuse of waste lithium-rich manganese-based positive electrode materials. Background Art

[0002] Lithium-ion batteries have become the most promising high-efficiency secondary batteries and the fastest-growing chemical energy storage power sources due to their high specific energy, long cycle life, no memory effect and light weight. The electrode materials of used lithium-ion batteries contain a large amount of valuable elements and are known as the "mobile mines" in cities. If not processed, they will not only waste resources, but also cause environmental pollution due to the toxic substances in the batteries. Among the many lithium-ion battery positive electrode materials, lithium-rich manganese-based positive electrode materials (such as Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 materials) are expected to achieve industrialization and large-scale application due to their high cost-effectiveness. Currently, the recycling of lithium-ion battery electrode materials primarily relies on two extraction methods: pyrometallurgy and hydrometallurgy. However, due to the high Mn content in lithium-rich manganese-based cathode materials, which is relatively inexpensive compared to metals such as Li and Co, recycling waste lithium-rich manganese-based cathode materials using traditional extraction methods is not only unprofitable, but also energy-intensive and highly polluting. Furthermore, the complex structure of lithium-rich manganese-based cathode materials makes direct recycling quite challenging.

[0003] Aqueous zinc-ion batteries not only exhibit high safety but also offer significant advantages over commercial lithium-ion batteries in terms of energy storage cost. With a high theoretical capacity of 820 mAh / g and a low negative electrode redox potential (-0.76V vs. standard hydrogen electrode), aqueous zinc-ion batteries can achieve higher energy density than other aqueous batteries. Pure manganese oxides have been a popular cathode material for zinc-ion batteries due to their abundance, low cost, and low toxicity.

[0004] Exploring effective recycling methods and technologies for waste lithium-rich manganese-based positive electrode materials is of great significance in providing an effective and reasonable way to solve the environmental pollution and resource waste problems caused by waste lithium-ion batteries. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention provides a method for the electrolytic recovery and reuse of waste lithium-rich manganese-based positive electrode materials, aiming to use the lithium-rich manganese-based positive electrode materials to recover the Li element while utilizing the rich Mn element to prepare high-efficiency aqueous manganese-based zinc-ion battery positive electrode materials on a large scale.

[0006] To achieve the purpose, the present invention adopts the following technical solutions:

[0007] A method for electrolytically recovering and reusing waste lithium-rich manganese-based cathode materials is characterized by firstly removing lithium from waste lithium-ion battery lithium-rich manganese-based cathode materials through an electrolytic method driven by an electric field, then annealing the delithiated lithium-rich manganese-based cathode materials to obtain manganese-based composite oxides; and recovering the released lithium ions by precipitation by adding a precipitant. Specifically, the method comprises the following steps:

[0008] Step 1: dismantle waste lithium-ion batteries to obtain lithium-rich manganese-based positive electrode plates, peel off the lithium-rich manganese-based positive electrode material and the current collector in the plates, clean and dry them, and then grind them into powder; dissolve an organic binder in a solvent, add the ground lithium-rich manganese-based positive electrode material, and make a slurry by ultrasonication and / or stirring; then evenly apply the slurry on a titanium mesh and dry it to obtain an anode plate.

[0009] Step 2: Place the anode sheet prepared in step 1 and the blank electrode in an electrolyte, and connect them to the positive and negative electrodes of an adjustable DC regulated power supply, respectively, to perform electric field-driven electrolysis, so that lithium ions in the lithium-rich manganese-based positive electrode material on the anode sheet are released and enter the electrolyte;

[0010] Step 3: Place the delithiated anode sheet in N-methylpyrrolidone for ultrasonic treatment, collect the material separated from the anode sheet, wash it with distilled water to remove residual salt ions (mainly salt in the electrolyte), and obtain the delithiated lithium-rich manganese-based positive electrode material after drying.

[0011] Step 4: annealing the obtained lithium-rich manganese-based positive electrode material after delithiation to obtain a manganese-based composite oxide.

[0012] The manganese-based composite oxide obtained by the present invention can be used as a positive electrode material for aqueous zinc-ion batteries. In addition to manganese, the manganese-based composite oxide also contains nickel and cobalt. By controlling the electrolysis conditions in step 2 to control the amount of lithium ions released, the resulting manganese-based composite oxide can also contain a small amount of lithium. The incorporation of nickel, cobalt, and lithium can further improve the performance of aqueous zinc-ion batteries using the manganese-based composite oxide as a positive electrode material.

[0013] Preferably, in step 2, the lithium ions that escape and enter the electrolyte can be recovered by precipitation by adding phosphoric acid H3PO4 or sodium carbonate Na2CO3 as a precipitant.

[0014] Preferably, in step 1, the content of lithium-rich manganese-based positive electrode material in the powder of waste lithium-rich manganese-based positive electrode material obtained after pretreatment such as stripping, washing, drying, and grinding is not less than 95 wt%. The lithium-rich manganese-based positive electrode plates of waste lithium-ion batteries contain carbon, and Al impurities may be introduced during the stripping process between the plates and the Al current collector. Multiple washings with water or NaOH solution can effectively remove impurities such as carbon and aluminum, thereby increasing the content of lithium-rich manganese-based positive electrode material in the powder, such that the carbon content in the powder is within the range of 0-3 wt% and the aluminum impurity content is within the range of 0-2 wt%.

[0015] Preferably, in step 1, the organic binder is at least one of polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex (SBR), carboxymethyl cellulose (CMC), polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and Nafion solution, and the solvent is at least one of N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

[0016] Preferably, in the slurry of step 1, the mass ratio of the organic binder to the lithium-rich manganese-based positive electrode material is 1:10-100.

[0017] Preferably, the loading amount of the lithium-rich manganese-based positive electrode material in the anode sheet obtained in step 1 is 0.01-0.1 g / cm 2 .

[0018] Preferably, in step 2, the blank electrode is a metal electrode (such as one of metals such as platinum, titanium, gold, iridium and palladium, or an alloy electrode) or a carbon electrode (such as a graphite electrode or a carbon cloth electrode).

[0019] Preferably, in step 2: the electrolyte is a solution of at least one salt selected from sodium chloride (NaCl), potassium sulfate (K2SO4), potassium carbonate (K2CO3), potassium hydroxide (KOH), sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), sodium hydroxide (NaOH) and sodium dodecyl sulfate (SDS); the concentration of the electrolyte is controlled between 0.1 and 2 M, and the pH value is controlled between 4.5 and 13 (the pH value of the electrolyte can be regulated by adding acid or alkali), and the temperature range of the electrolyte during the electric field driven electrolysis is 20 to 80 ° C.

[0020] Preferably, in step 2, the electric field driven electrolysis is performed by applying a constant current of 10-400 mA or a constant voltage of 2-5 V to the two electrodes, and the time of the electric field driven electrolysis is 3-24 h.

[0021] Preferably, in step 4, the annealing temperature is 300-600° C., the annealing time is 4-20 h, and the annealing atmosphere can be air or an inert gas.

[0022] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0023] 1. The present invention realizes the recovery of Li from lithium-rich manganese-based cathode materials of waste lithium-ion batteries through electrochemical reaction delithiation and annealing treatment, and innovatively applies the obtained manganese-based composite oxide to the cathode of aqueous zinc-ion batteries. The reaction conditions are mild and easy to implement, the operability is strong, the process is green and environmentally friendly, and the recycling process is simple. It provides an effective way for the high-value recovery and reuse of waste lithium-ion battery cathode materials and the preparation of manganese-based cathode materials for aqueous zinc-ion batteries, and has good application prospects.

[0024] 2. The present invention removes lithium through an electrochemical reaction. The lithium-rich manganese-based positive electrode material is gradually peeled off during the delithiation process, and obvious peeling cracks can gradually be seen on the surface of the particles. However, the product after delithiation is not peeled into a flaky form and still maintains a layered structure. This shows that the peeling process does not completely rely on the phase change induced by the delithiation process, thereby enhancing the capacity and cyclability of the manganese-based composite oxide when used as a positive electrode material for zinc-ion batteries.

[0025] 3. The manganese-based composite oxide obtained after delithiation and annealing in the present invention is doped with elements such as Ni and Co, so that it has higher specific capacity and stability when used as a positive electrode material for aqueous zinc ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope (SEM) image of the lithium-rich manganese-based positive electrode powder (ie, sample 1) obtained through pretreatment in Example 1 of the present invention.

[0027] Figure 2 This is a scanning electron microscope (SEM) image of the lithium-rich manganese-based positive electrode material (ie, sample 3) after delithiation and annealing in Example 1 of the present invention.

[0028] Figure 3 1 is the XRD pattern of samples 1 to 3 in Example 1 of the present invention.

[0029] Figure 4 This is a constant current charge and discharge curve diagram of the zinc ion button battery assembled with samples 1 to 3 as the positive electrode material at a rate of 2 A / g in Example 1 of the present invention.

[0030] Figure 5 This is a graph showing the cycling performance of zinc ion button cells assembled with samples 1 to 3 as positive electrode materials at a rate of 2 A / g in Example 1 of the present invention.

[0031] Figure 6 This is the XRD pattern of lithium phosphate recovered by adding phosphoric acid for precipitation in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings and examples. The following is merely an example and illustration of the concept of the present invention. Those skilled in the art may make various modifications, supplements, or replace the specific embodiments described in the description with similar methods. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides waste lithium-rich manganese-based positive electrode materials (sLi 1.2 Mn 0.54 Ni 0.13 Co 0.13 The electrolytic recovery and reuse method of O2 comprises the following steps:

[0035] Step 1: Dismantle the waste lithium-ion battery to obtain the lithium-rich manganese-based positive electrode plate, peel off the lithium-rich manganese-based positive electrode material and the aluminum current collector in the plate, then wash it with deionized water for multiple times, dry it at room temperature, and grind it into powder to obtain the lithium-rich manganese-based positive electrode powder (sLi 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, recorded as sample 1). 0.01 g of PVDF was added to a stirring flask, and an appropriate amount of NMP solvent was added dropwise and stirred for 12 h until it became transparent. Then, 0.5 g of lithium-rich manganese-based positive electrode powder was added and stirred at room temperature for 12 h to obtain a slurry. The slurry was then evenly coated on a titanium mesh (70 mm × 50 mm) with a coating area of ​​50 mm × 40 mm. The mesh was then dried in an oven at 80°C to obtain a titanium mesh coated with a lithium-rich manganese-based positive electrode material, which was used as the anode sheet in step 2. The loading amount of lithium-rich manganese-based positive electrode material in the anode sheet was 0.025 g / cm 2 .

[0036] Step 2: Add 100 mL of 0.5 M K₂SO₄ solution as the electrolyte to the electrolytic cell at 25°C. Place the anode sheet prepared in Step 1 in the electrolyte and connect it to the positive terminal of an adjustable DC regulated power supply. Place a graphite plate (5 mm × 60 mm × 80 mm) in the electrolyte as the cathode and connect it to the negative terminal of the power supply. Apply a constant voltage of 3 V for 3 hours to desorb most of the lithium ions from the lithium-rich manganese-based cathode material. Heat the delithiated electrolyte to 90°C and add phosphoric acid dropwise to recover the lithium ions in the electrolyte as Li₃PO₄ precipitate.

[0037] Step 3: Place the delithiation anode sheet in NMP for ultrasonication, collect the material separated from the anode sheet, wash it with distilled water to remove the residual salt ions, and dry it in an oven at 80°C to obtain the delithiation lithium-rich manganese-based positive electrode material (sLi 1.2-x Mn 0.54 Ni 0.13 Co 0.13 O2, 0.4<x≤1.2, recorded as sample 2).

[0038] Step 4: anneal the lithium-rich manganese-based cathode material after delithiation at 400°C in an air atmosphere in a muffle furnace for 10 hours to obtain a manganese-based composite oxide (sLi 1.2-x Mn 0.54 Ni 0.13 Co 0.13 O2-A, recorded as sample 3).

[0039] Figure 1 is a scanning electron microscope (SEM) image of the lithium-rich manganese-based positive electrode powder (i.e., sample 1) obtained by pretreatment in this embodiment. Figure 2 This is a scanning electron microscope (SEM) image of the lithium-rich manganese-based cathode material (Sample 3) after delithiation and annealing. It can be seen that the cathode material originally has a polycrystalline, large particle morphology. As the electrolysis time increases, obvious delamination can be seen on the surface of the material particles. However, the delithiation product does not delaminate into a flaky morphology and still maintains a layered structure, indicating that the delamination process is not entirely dependent on the phase transformation induced by the delithiation process.

[0040] Figure 3 The following are XRD patterns for samples 1 to 3. The results show that compared to sample 1, some characteristic peaks in sample 2 have weakened, while some characteristic peaks in sample 3 have completely disappeared. Furthermore, the full width at half maximum of the strongest characteristic peak has increased significantly. According to the Scherrer equation, this is due to the smaller particles. Therefore, as the voltage is driven, most of the lithium ions are released, and the characteristic peaks become weaker. As time passes and the voltage and current increase, the lithium ions are completely released.

[0041] Each sample was used as the positive electrode material to assemble aqueous zinc-ion batteries: Sample 2, Sample 3, or Sample 1 annealed according to the conditions of Step 4 was ground and mixed with graphite and PVDF in a mass ratio of 7:2:1. The mixture was then dissolved in NMP to prepare a positive electrode slurry. The slurry was cast onto a carbon paper current collector to a thickness of 75 μm and dried in an 80°C oven for 6 h. The slurry was then assembled into button cells using zinc foil (>99.99%) as the negative electrode and 2 M zinc sulfate + 0.5 M manganese sulfate as the electrolyte. The electrochemical performance of the resulting aqueous zinc-ion batteries was tested using a BTS-5V 10mA tester (Shenzhen Xinweier Electronics Co., Ltd.).

[0042] Figure 4 and Figure 5 The cycle performance diagram and constant current charge and discharge curve of the zinc ion button battery assembled by each sample at a rate of 2 A / g are shown respectively. Figure 4 It can be seen that sample 1 (i.e., lithium-rich manganese-based positive electrode material that has not been delithiated and annealed) has an extremely low specific capacity, almost no performance, and extremely poor stability as a positive electrode material for zinc-ion batteries. Sample 2 (i.e., lithium-rich manganese-based positive electrode material that has not been annealed after delithiation) also has poor performance, with an extremely low specific capacity and almost no performance. However, sample 3, which has been delithiated and annealed, exhibits a specific capacity of more than 200 mAh / g at a rate of 2 A / g, showing a relatively high capacity performance. At the same time, Figure 5 It was confirmed that sample 3 still had stable performance after 250 cycles and had good cycle stability, while samples 1 and 2 almost lost their electrochemical activity after 20 cycles.

[0043] Figure 6 This is the XRD diagram of Li3PO4 recovered in the form of precipitation by adding phosphoric acid to the delithiation electrolyte. It can be seen that the recovered Li3PO4 has high purity and commercial value.

[0044] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for electrolytic recovery and reuse of waste lithium-rich manganese-based cathode materials, characterized by: First, the lithium-rich manganese-based cathode material of the waste lithium-ion battery is subjected to electric field-driven delithiation by electrolysis, and then the delithiation-removed lithium-rich manganese-based cathode material is annealed to obtain a manganese-based composite oxide, which is used as a cathode material for aqueous zinc-ion batteries; the delithiation-removed Li ions are precipitated and recovered by adding a precipitant; the method specifically comprises the following steps: Step 1: Take the lithium-rich manganese-based positive electrode plate of the waste lithium-ion battery, peel off the lithium-rich manganese-based positive electrode material and the current collector in the plate, clean and dry it, and grind it into powder to obtain lithium-rich manganese-based positive electrode powder sLi 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2; dissolving an organic binder in a solvent, adding the ground lithium-rich manganese-based positive electrode material, and preparing a slurry by ultrasonication and / or stirring; then uniformly coating the slurry on a titanium mesh and drying it to obtain an anode sheet, wherein the loading amount of the lithium-rich manganese-based positive electrode material in the obtained anode sheet is 0.025 g / cm 2 ; Step 2: The anode sheet prepared in step 1 and the blank electrode graphite plate are placed in the electrolyte with a gap, and are respectively connected to the positive and negative electrodes of an adjustable DC regulated power supply to perform electric field-driven electrolysis, so that the lithium ions in the lithium-rich manganese-based positive electrode material on the anode sheet are released and enter the electrolyte; the electric field-driven electrolysis is performed by applying a constant voltage of 3 V to the two electrodes, and the electric field-driven electrolysis time is 3 hours; Step 3: Place the delithiation anode sheet in N-methylpyrrolidone for ultrasonication, collect the material separated from the anode sheet, wash it with distilled water to remove the residual salt ions, and dry it to obtain the delithiation lithium-rich manganese-based positive electrode material sLi 1.2-x Mn 0.54 Ni 0.13 Co 0.13 O2, 0.4<x≤1.2; Step 4: annealing the obtained lithium-rich manganese-based positive electrode material after delithiation at 400° C. in an air atmosphere in a muffle furnace for 10 hours to obtain a manganese-based composite oxide.

2. The electrolytic recovery and reuse method of waste lithium-rich manganese-based positive electrode materials according to claim 1, characterized in that: In step 2, the lithium ions that have escaped and entered the electrolyte are precipitated and recovered by adding phosphoric acid H3PO4 or sodium carbonate Na2CO3 as a precipitant.

3. The electrolytic recovery and reuse method of waste lithium-rich manganese-based positive electrode materials according to claim 1, characterized in that: In step 1, the organic binder is selected from at least one of polyvinylidene fluoride, styrene-butadiene rubber emulsion, carboxymethyl cellulose, polyethylene oxide, polymethyl methacrylate and Nafion solution, and the solvent is at least one of N,N-dimethylformamide and N-methylpyrrolidone; in the slurry of step 1, the mass ratio of the organic binder to the lithium-rich manganese-based positive electrode material is 1:10-100.

4. The electrolytic recovery and reuse method of waste lithium-rich manganese-based positive electrode materials according to claim 1, characterized in that: In step 2: the electrolyte is a solution of at least one salt selected from sodium chloride, potassium sulfate, potassium carbonate, potassium hydroxide, sodium sulfate, sodium carbonate, sodium bicarbonate, sodium hydroxide, and sodium lauryl sulfate; the concentration of the electrolyte is controlled between 0.1 and 2 M, the pH value is controlled between 4.5 and 13, and the temperature range of the electrolyte during the electric field-driven electrolysis is 20 to 80°C.

Images