A method for recycling valuable metals from lithium manganese oxide materials and a cathode material

Abstract

This invention belongs to the field of waste battery resource recycling technology, specifically relating to a method for recycling and reusing valuable metals in lithium manganese oxide materials and a cathode material. The method for recycling and reusing valuable metals in lithium manganese oxide materials of this invention includes the following steps: (1) ball milling; (2) low-temperature calcination; (3) lithium dissolution; (4) filtration to obtain crude lithium solution and a first filter residue; (5) impurity removal from the lithium solution and the first filter residue; (6) preparation of a mixed solution; (7) fine-tuning of the element ratio; (8) LiNi 0.5 Mn 1.5 O4 precursor preparation; (9) LiNi 0.5 Mn 1.5 The O4 precursor was dried, ball-milled, and sintered to obtain the high-voltage cathode material LiNi. 0.5 Mn 1.5 O4. The method for recycling and reusing valuable metals from lithium manganese oxide materials according to the present invention is simple, low-cost, and environmentally friendly, and helps to achieve green closed-loop recycling and reuse of valuable metals from waste lithium manganese oxide materials.

Description

Technical Field

[0001] This invention belongs to the field of waste battery resource recycling technology, specifically relating to a method for recycling and reusing valuable metals in lithium manganese oxide materials and a cathode material. Background Technology

[0002] With the rapid development of the new energy industry, the output of new energy batteries is increasing year by year. Simultaneously, a large number of lithium batteries will be retired each year. How to economically and environmentally recycle and reuse these used lithium batteries is crucial for the healthy development of the new energy industry. Lithium manganese oxide batteries are among the most widely used batteries due to their low cost and excellent cycle and safety performance. However, since lithium manganese oxide materials contain only lithium and manganese metals, with a relatively low lithium content, the recycling value generated under the same energy consumption is far less than that of ternary materials if the recycling route is followed. Therefore, low-energy, high-efficiency recycling and reuse is another breakthrough point for lithium manganese oxide material recycling.

[0003] Some literature discloses the use of a mixture of positive and negative electrode powders dissolved and soaked in acidic solution, followed by filtration to obtain an acidic solution containing lithium and manganese. The pH is then adjusted to 5–7 with NaOH or ammonia to remove impurities, and to 10–12 with NaOH to obtain solid manganese hydroxide and a lithium-containing solution. The lithium-containing solution is then precipitated with sodium carbonate. This method is a typical wet recovery process, which not only uses large quantities of reagents and has a complex process flow, but also requires a large area and easily generates large amounts of high-concentration acid and alkaline wastewater.

[0004] Another literature discloses a method of mixing treated lithium manganese oxide cathode material with an appropriate amount of carbon powder, reducing and roasting it at 800–1300℃, then dissolving lithium in dilute acid, adjusting the pH to 7–10, filtering to obtain a purified lithium-containing solution, and then precipitating lithium carbonate using carbonates. This method involves high reduction and roasting temperatures, high energy consumption, unpurified manganese oxides, and the generation of a large amount of salt solution. None of the above-mentioned lithium manganese oxide recovery schemes achieve a closed-loop recovery and utilization of all metal ions during the lithium manganese oxide recovery process.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a method for recycling and reusing valuable metals in lithium manganese oxide materials and a cathode material, so as to solve or improve at least one of the problems of current methods for recycling and reusing valuable metals in lithium manganese oxide materials, such as difficulty in achieving green closed-loop recycling and utilization of valuable metals, poor environmental performance, and low efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for recycling and reusing valuable metals from lithium manganese oxide materials, comprising the following steps: (1) ball milling: mixing waste lithium manganese oxide material powder with graphite, lithium hydroxide and nickel hydroxide in proportion to obtain a mixture; (2) low-temperature calcination: placing the mixture in an inert atmosphere for reduction calcination to obtain a calcined material; (3) lithium dissolution: mixing the calcined material with water in proportion to dissolve lithium to obtain a lithium-containing solution; (4) filtration: filtering the lithium-containing solution to obtain a crude lithium liquid and a first filter residue, wherein the main components of the first filter residue are manganese oxide, nickel oxide and graphite; (5) Lithium liquid and first filter residue impurity removal: The pH of the crude lithium liquid is adjusted to pH=7-8 using organic acid, and aluminum is removed by filtration to obtain pure lithium liquid; the first filter residue is dissolved in organic acid solution at 60-70℃ and filtered to obtain nickel-manganese mixture; (6) Preparation of mixed solution: The pure lithium liquid and nickel-manganese mixture obtained in step (5) are mixed and stirred, and fluoride is added to precipitate calcium ions and / or magnesium ions, and filtered to obtain pure mixed solution; (7) Fine adjustment of element ratio: The content of lithium, nickel and manganese elements in the pure mixed solution is detected, and the element ratio is finely adjusted using acetate to make Li:Ni:Mn=1:0.5:1.5; (8) LiNi 0.5 Mn 1.5 O4 precursor preparation: Adjust the pH of the mixture obtained after step (7), evaporate and concentrate to a gel state, to obtain LiNi 0.5 Mn 1.5 O4 precursor; (9) for the LiNi 0.5 Mn 1.5 The O4 precursor was dried, ball-milled, and sintered to obtain the high-voltage cathode material LiNi. 0.5 Mn 1.5 O4; In step (2), the calcination temperature is 500-600℃ and the calcination time is 4-8h; In step (9), the sintering temperature is 820℃ and the sintering time is 12h.

[0008] Preferably, in step (1), the mass ratio of the waste lithium manganese oxide material powder to graphite is 10:(1-5); the molar ratio of the waste lithium manganese oxide material powder to lithium hydroxide and nickel hydroxide is 3:1:2.

[0009] Preferably, in step (2), the inert atmosphere is nitrogen and / or argon.

[0010] Preferably, in step (3), the mass ratio of the roasting material to water is 1:(5-10).

[0011] Preferably, in step (5), the organic acid is citric acid, the concentration of the citric acid solution is 50 wt%, and the mass ratio of lemon to waste lithium manganese oxide powder in the citric acid solution is 6:1.

[0012] Preferably, in step (6), the fluoride is at least one of manganese fluoride, nickel fluoride and lithium fluoride; the number of moles of fluorine in the fluoride is twice the total number of moles of calcium and magnesium.

[0013] Preferably, in step (8), ammonia is used to adjust the pH of the mixture obtained in step (7) to 6.5-7, and the mixture is evaporated and concentrated to a gel state at 75-80°C.

[0014] This invention also provides a cathode material, which adopts the following technical solution: a cathode material, wherein the cathode material is prepared by the method described above; the cathode material is LiNi. 0.5 Mn 1.5 O4.

[0015] Beneficial effects:

[0016] This invention uses waste lithium manganese oxide battery cathode material as raw material. A mixture of waste lithium manganese oxide, graphite, lithium hydroxide, and nickel hydroxide is calcined at low temperature under an inert atmosphere to form a mixture of lithium oxide, nickel oxide, and manganese oxide. The lithium liquid and metal oxides are then separated using pure water. The lithium liquid is treated with organic acid to adjust pH and remove aluminum impurities, while the metal oxides dissolve in the organic acid solution. The lithium liquid is then mixed and stirred with nickel and manganese liquids. Calcium and magnesium impurities are removed using fluoride, and the metal element ratio is finely adjusted. The pH is then adjusted, and the mixture is evaporated to form a gel. After drying, grinding, and sintering, the high-voltage cathode material LiNi is obtained. 0.5 Mn 1.5 O4.

[0017] The method for recycling and reusing valuable metals in lithium manganese oxide materials according to the present invention is simple, low-cost, and environmentally friendly, realizing a green closed-loop recycling and utilization of valuable metals in waste lithium manganese oxide materials. In addition, the method of the present invention avoids the generation of waste acid and alkali during the treatment of waste lithium manganese oxide materials, making it more environmentally friendly. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0019] Figure 1 This is a process flow diagram of a method for recycling and reusing valuable metals from lithium manganese oxide materials according to an embodiment of the present invention.

[0020] Figure 2 The cathode material (LiNi) prepared according to one embodiment of the present invention 0.5 Mn 1.5 The XRD test results of O4) are shown in the figure. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0022] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0023] This invention addresses at least one of the following problems in the current process of recycling and reusing valuable metals in lithium manganese oxide materials: difficulty in achieving green closed-loop recycling of valuable metals, poor environmental performance, and low efficiency. It provides a method for recycling and reusing valuable metals in lithium manganese oxide materials, comprising the following steps:

[0024] (1) Ball milling: The waste lithium manganese oxide material powder is ball milled and mixed evenly with graphite, lithium hydroxide and nickel hydroxide in proportion to obtain a mixture;

[0025] (2) Low-temperature roasting: The mixture is placed in an inert atmosphere for reduction roasting, and the high-valent manganese (Mn) is reduced and roasted. 3+ Mn 4+ The manganese ions are reduced to divalent manganese ions to obtain the calcined material;

[0026] (3) Lithium dissolution: The calcined material and water are mixed and stirred in a certain proportion to dissolve lithium, resulting in a lithium-containing solution.

[0027] (4) Filtration: The lithium-containing solution is filtered to obtain crude lithium liquid and first filter residue. The main components of the first filter residue are manganese oxide, nickel oxide and graphite.

[0028] (5) Lithium liquid and first filter residue removal: Adjust the pH of the crude lithium liquid to pH = 7-8 using organic acids (e.g., pH = 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9 or 8; wherein, Al 3+ The precipitation pH range is 5.5–8. When the pH is greater than 8, Al… 3+ The first filter residue is dissolved in an organic acid solution at a temperature of 60–70°C (e.g., 60°C, 62°C, 64°C, 66°C, 68°C, or 70°C) (the first filter residue is dissolved at an elevated temperature to accelerate the dissolution reaction; 60–70°C is a suitable temperature, as higher temperatures will increase reaction costs). The resulting solution is filtered to obtain a nickel-manganese mixture. The organic acid is readily decomposed by heat, making it suitable for the LiNi process in this invention. 0.5 Mn1.5 The preparation of O4 using organic acids is not only green and environmentally friendly, but also does not introduce other impurities; specifically, the organic acid can be at least one of citric acid, acetic acid or tartaric acid.

[0029] (6) Preparation of mixed solution: The pure lithium liquid and nickel-manganese mixed solution obtained in step (5) are mixed and stirred, and fluoride is added to precipitate calcium ions and / or magnesium ions. The pure mixed solution is then filtered.

[0030] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixed solution was detected, and the element ratio was fine-tuned using acetate so that the molar ratio of Li:Ni:Mn was 1:0.5:1.5;

[0031] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: Adjust the pH of the mixture obtained after step (7), evaporate and concentrate to a gel state, to obtain LiNi 0.5 Mn 1.5 O4 precursor;

[0032] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried, ball-milled, and sintered to obtain the high-voltage cathode material LiNi. 0.5 Mn 1.5 O4;

[0033] In step (2), the roasting temperature is 500-600℃ (e.g., 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃), and the roasting time is 4-8h (e.g., 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h or 8h);

[0034] In step (9), the sintering temperature is 820℃ (the target material cannot be synthesized if the temperature exceeds this range), and the sintering time is 12h.

[0035] In step (2), the present invention reduces waste lithium manganese oxide by simultaneously using graphite, lithium hydroxide, and nickel hydroxide. Compared with using graphite alone, the reduction of waste lithium manganese oxide can be achieved at a significantly lower temperature, thereby removing Mn from the waste lithium manganese oxide. 3+ and Mn 4+ Restored to Mn 2+ Furthermore, lithium hydroxide and nickel hydroxide can also adjust the elemental ratio of manganese, nickel, and lithium in the mixture, facilitating the preparation of high-voltage cathode material LiNi through subsequent processing steps. 0.5 Mn 1.5 O4.

[0036] The method for recycling valuable metals from lithium manganese oxide materials of the present invention involves low-temperature calcination of waste lithium manganese oxide powder, graphite, lithium hydroxide, and nickel hydroxide to form a mixture of lithium oxide, nickel oxide, and manganese oxide. The lithium oxide and metal oxides are then separated using pure water. The lithium oxide solution is pH-adjusted with organic acids to remove aluminum impurities, while the metal oxides are dissolved in the organic acid solution and calcium and magnesium impurities are removed using fluorides. Subsequently, the lithium oxide solution is mixed and stirred with nickel and manganese oxide solutions, and the metal element ratio is finely adjusted. The pH is then adjusted to evaporate and form a gel, which is then dried, ground, and sintered (during which a high-voltage cathode material, LiNi, is generated). 0.5 Mn 1.5 Through processes such as O4, high-voltage cathode material LiNi can be obtained. 0.5 Mn 1.5 O4.

[0037] In a preferred embodiment of the present invention, in step (1), the mass ratio of waste lithium manganese oxide material powder to graphite is 10:(1-5) (for example, 10:1, 10:2, 10:3, 10:4 or 10:5; if the amount of graphite is too small, the lithium manganese oxide material cannot be fully reduced, and if too much is used, it will be wasteful); the molar ratio of waste lithium manganese oxide material powder to lithium hydroxide and nickel hydroxide is 3:1:2.

[0038] In calculating the molar amount of waste lithium manganese oxide, lithium manganese oxide is treated as pure lithium manganese oxide, and its mass is converted into molar amounts. The amounts of lithium hydroxide and nickel hydroxide are then calculated based on the molar amounts of lithium manganese oxide. Lithium hydroxide and nickel hydroxide also play a role in reducing waste lithium manganese oxide in this invention. If the amount of lithium hydroxide and / or nickel hydroxide is too small, the reduction of manganese will be incomplete, leading to a decline in the final high-voltage cathode material LiNi. 0.5 Mn 1.5 The reduction of O4 and the presence of a large amount of valuable metals in the filter residue hinder efficient recovery of these metals. Furthermore, by maintaining a molar ratio of waste lithium manganese oxide powder to lithium hydroxide and nickel hydroxide of 3:1:2, not only is it beneficial to lower the calcination temperature of the mixture, but it also helps ensure that subsequent high-voltage material synthesis requires only minor adjustments or no adjustment of elemental content. Graphite is mainly used in this invention to reduce lithium manganese oxide; insufficient graphite will not adequately reduce lithium manganese oxide, while excessive graphite will result in waste.

[0039] In a preferred embodiment of the present invention, in step (2), the inert atmosphere is nitrogen and / or argon.

[0040] In a preferred embodiment of the present invention, in step (3), the mass ratio of the calcining material to water is 1:(5-10). The amount of water used is appropriate to ensure sufficient dissolution of lithium hydroxide in the calcining material (the solubility of lithium hydroxide is 12.8 g / 100 g H2O) and to facilitate mixing and stirring of the calcining material and water. Excessive water usage will negatively impact the subsequent LiNi...0.5 Mn 1.5 The preparation of O4 precursors is burdensome and increases energy consumption.

[0041] In a preferred embodiment of the present invention, in step (5), the organic acid is citric acid; the concentration of the citric acid solution is 50 wt%, and the mass ratio of citric acid in the citric acid solution to waste lithium manganese oxide powder is 6:1. The citric acid is in excess, which can not only completely dissolve nickel oxide and manganese oxide, but also the excess citric acid can act as a chelating agent (citric acid can form stable complexes of metal ions, which is beneficial for the uniform dispersion of ions).

[0042] In a preferred embodiment of the present invention, in step (6), the fluoride is at least one of manganese fluoride, nickel fluoride and lithium fluoride; the number of moles of fluorine in the fluoride is twice the total number of moles of calcium and magnesium.

[0043] In a preferred embodiment of the present invention, in step (8), ammonia is used to adjust the pH of the mixture obtained after treatment in step (7) to 6.5–7.5 (e.g., 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, or 7.5), and the mixture is evaporated and concentrated to a gel state at 75–80°C (e.g., 75°C, 76°C, 77°C, 78°C, 79°C, or 80°C). If the evaporation and concentration temperature is too low, the time required for gel formation will be longer; if the temperature is too high, the formation of a wet gel state is difficult to control (if the evaporation and concentration temperature is too high, the liquid evaporates too quickly, easily drying out and failing to form a gel, and the pH value will be difficult to control within a stable range, resulting in uneven ion distribution from the complexation reaction, leading to poor synthesis of LiNi). 0.5 Mn 1.5 The structure of O4 will be affected.

[0044] This invention also proposes a cathode material, which is prepared using the method described above; the cathode material is LiNi. 0.5 Mn 1.5 O4.

[0045] The following detailed description of the method for recycling and reusing valuable metals in lithium manganese oxide materials and the cathode material of the present invention is provided through specific embodiments.

[0046] In the following examples: the waste lithium manganese oxide material used is lithium manganese oxide waste generated during the production process of Jiaozuo Banlv Nanomaterials Engineering Co., Ltd.

[0047] The recovery rate of manganese or lithium is calculated according to the following formula:

[0048] Recycling rate = (Total molar amount of metal elements in the synthesized high-voltage material - Molar amount of metal elements added for fine-tuning) ÷ Total molar amount of the element in the waste lithium manganese oxide material × 100%.

[0049] The number of moles of waste lithium manganese oxide material is calculated according to the following formula:

[0050] The number of moles of waste lithium manganese oxide material = the mass of waste lithium manganese oxide material ÷ the relative molecular mass of lithium manganese oxide.

[0051] Example 1

[0052] Reference Figure 1 The method for recycling and reusing valuable metals from lithium manganese oxide materials in this embodiment includes the following steps:

[0053] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 4.52g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0054] (2) Low-temperature calcination: The mixture was reduced and calcined at 550℃ for 6 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0055] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:5, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0056] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=7.5, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0057] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 60°C for 2 h, and filter to obtain nickel-manganese mixed solution;

[0058] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0059] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0060] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi.0.5 Mn 1.5 O4 precursor;

[0061] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 22.7 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0062] Tests showed that the lithium recovery rate in lithium manganese oxide was 93.1%, and the manganese recovery rate was 91.8%.

[0063] The cathode material in this embodiment is prepared using steps (1)-(9) as described above. The cathode material in this embodiment is a high-voltage cathode material, LiNi. 0.5 Mn 1.5 O4 was subjected to XRD testing, and the test results are as follows: Figure 2 As shown, this is a standard LiNi 0.5 Mn 1.5 O4 XRD pattern; LiNi high-voltage cathode material prepared in this embodiment. 0.5 Mn 1.5 O4 has high purity and is virtually free of impurities.

[0064] Example 2

[0065] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 1.81g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0066] (2) Low-temperature calcination: The mixture was reduced and calcined at 500℃ for 4 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0067] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:5, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0068] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=8, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0069] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 60°C for 2 h, and filter to obtain nickel-manganese mixed solution;

[0070] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0071] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0072] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi. 0.5 Mn 1.5 O4 precursor;

[0073] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 19.2 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0074] Tests showed that the lithium recovery rate in lithium manganese oxide was 78.9%, and the manganese recovery rate was 76.1%.

[0075] Example 3

[0076] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 9.05g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0077] (2) Low-temperature calcination: The mixture was reduced and calcined at 500℃ for 4 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0078] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:10, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0079] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=8, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0080] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 60°C for 2 h, and filter to obtain nickel-manganese mixed solution;

[0081] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0082] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0083] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi. 0.5 Mn 1.5 O4 precursor;

[0084] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 21.0 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0085] Tests showed that the lithium recovery rate in lithium manganese oxide was 86.5%, and the manganese recovery rate was 85.1%.

[0086] Example 4

[0087] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 9.05g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0088] (2) Low-temperature calcination: The mixture was reduced and calcined at 550℃ for 6 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0089] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:5, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0090] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=8, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0091] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 70°C for 1 h, and filter to obtain nickel-manganese mixed solution;

[0092] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0093] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0094] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi0. .5 Mn 1.5 O4 precursor;

[0095] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 22.8 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0096] Tests showed that the lithium recovery rate in lithium manganese oxide was 93.8%, and the manganese recovery rate was 92.0%.

[0097] Example 5

[0098] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 1.81g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0099] (2) Low-temperature calcination: The mixture was reduced and calcined at 550℃ for 6 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0100] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:5, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0101] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=8, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0102] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 70°C for 1 h, and filter to obtain nickel-manganese mixed solution;

[0103] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0104] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0105] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi. 0.5 Mn 1.5 O4 precursor;

[0106] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 20.5 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0107] Tests showed that the lithium recovery rate in lithium manganese oxide was 84.1%, and the manganese recovery rate was 82.5%.

[0108] Comparative Example 1

[0109] The method for recycling and reusing valuable metals from lithium manganese oxide materials in this comparative example includes the following steps:

[0110] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder was mixed with 4.52g of graphite, 5.99g of lithium hydroxide and 6.18g of nickel hydroxide and ball milled evenly to obtain a mixture;

[0111] (2) Low-temperature calcination: The mixture was reduced and calcined at 450℃ for 6 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0112] (3) Lithium dissolution: The roasted material and water are mixed and stirred at a solid-liquid ratio of 1:5, and filtered to obtain crude lithium liquid (lithium hydroxide solution) and first filter residue. The first filter residue is mainly composed of manganese oxide, nickel oxide and unreacted graphite.

[0113] (4) Lithium liquid impurity removal: Slowly add citric acid to crude lithium liquid to make pH=8, react at room temperature for 30 min, and filter to obtain pure lithium liquid and aluminum-containing slag;

[0114] (5) First filter residue removal: Add 217.2 mL of 50% citric acid solution to the first filter residue (mixed filter residue of manganese oxide, nickel oxide and graphite), dissolve it completely at 70°C for 1 h, and filter to obtain nickel-manganese mixed solution;

[0115] (6) Preparation of mixed solution: The pure lithium solution obtained in step (4) is mixed and stirred with the nickel-manganese mixed solution obtained in step (5). The total calcium and magnesium content in the mixed solution is tested by ICP, and the same amount of manganese fluoride is added to it. Stir at 70°C for 30 min (precipitate calcium and magnesium), filter, and a pure mixed solution (lithium, nickel and manganese mixed solution) is obtained.

[0116] (7) Fine-tuning the element ratio: The content of lithium, nickel and manganese in the pure mixture was detected, and the element ratio was fine-tuned using acetate so that Li:Ni:Mn=1:0.5:1.5;

[0117] (8)LiNi 0.5 Mn 1.5 O4 precursor preparation: The pH of the mixture obtained in step (7) was adjusted to 6.5-7 using ammonia water, and then heated to 80℃ to evaporate and concentrate it into a gel to obtain LiNi. 0.5 Mn 1.5 O4 precursor;

[0118] (9) For LiNi 0.5 Mn 1.5 The O4 precursor was dried (in an oven at 120°C for 12 hours), ball-milled, and sintered (at 820°C for 12 hours in an air atmosphere) to obtain 8.59 g of high-voltage cathode material LiNi. 0.5 Mn 1.5 O4.

[0119] Calculations show that the lithium recovery rate in lithium manganese oxide is 35.3%, and the manganese recovery rate is 29.8%.

[0120] Comparative Example 2

[0121] The method for recycling and reusing valuable metals from lithium manganese oxide materials in this comparative example includes the following steps:

[0122] (1) Mixing and ball milling: 18.1g of waste lithium manganese oxide material powder and 4.52g of graphite were mixed and ball milled evenly to obtain a mixture;

[0123] (2) Low-temperature calcination: The mixture was reduced and calcined at 550℃ for 6 hours under argon atmosphere protection, with a heating rate of 5℃ / min, to obtain the calcined material;

[0124] (3) Lithium dissolution: The calcined material and water were mixed and stirred at a solid-liquid ratio of 1:5, filtered, and the filtrate was subjected to ICP detection. The lithium content was 0.103 mg / L, which showed that the lithium in the waste lithium manganese oxide material powder was not extracted.

[0125] Therefore, we believe that when only graphite is added, low-temperature calcination cannot reduce lithium manganese oxide waste to produce water-soluble lithium oxide.

[0126] In summary: when the reduction roasting temperature in step (2) drops below a reasonable range, the reduction effect decreases rapidly; simultaneously, appropriately increasing the amount of graphite and the roasting temperature and time within a suitable roasting temperature range can effectively improve the recovery rate of lithium and manganese in waste lithium manganese oxide, but the recovery rate tends to stabilize when the increase reaches a certain value. Therefore, only appropriate material ratios and roasting temperatures and times can ensure efficient, environmentally friendly, and low-energy-consumption recycling of waste lithium manganese oxide to obtain high-voltage material LiN i0.5 Mn 1.5 O4.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recycling valuable metals from a lithium manganate material, characterized in that, The method comprises the following steps: (1) mixing ball milling: waste lithium manganate material powder is mixed with graphite, lithium hydroxide and nickel hydroxide in a certain proportion by ball milling to obtain a mixture; (2) low-temperature roasting: the mixture is reduced and roasted in an inert atmosphere to obtain a roasted material; (3) lithium dissolution: the roasted material is mixed with water in a certain proportion to dissolve lithium to obtain a lithium-containing solution (4) filtration: the lithium-containing solution is filtered to obtain a crude lithium liquid and a first filter residue, and the main components of the first filter residue are manganese oxide, nickel oxide and graphite; (5) lithium liquid and first filter residue impurity removal: an organic acid is used to adjust the pH of the crude lithium liquid to pH=7-8, and aluminum is removed by filtration to obtain a pure lithium liquid; The first filter residue is dissolved in an organic acid solution at a temperature of 60-70°C, and a nickel-manganese mixed solution is obtained by filtration; (6) preparation of mixed solution: the pure lithium liquid and the nickel-manganese mixed solution obtained by step (5) are mixed and stirred, and fluoride is added to precipitate calcium ions and / or magnesium ions, and the pure mixed solution is obtained by filtration; (7) fine-tuning of element ratio: the contents of lithium, nickel and manganese elements in the pure mixed solution are detected, and the element ratio is fine-tuned using acetate to make Li:Ni:Mn=1:0.5:1.

5. (8) LiNi 0.5 Mn 1.5 O4 precursor preparation: adjust the pH of the mixture obtained from step (7), evaporate and concentrate to a gel, to obtain LiNi 0.5 Mn 1.5 O4 precursor; (9) drying, ball milling and sintering the LiNi 0.5 Mn 1.5 O4 precursor to obtain a high-voltage positive electrode material LiNi 0.5 Mn 1.5 O4; In step (1), the mass ratio of the waste lithium manganate material powder to graphite is 10:(1-5); In step (2), the roasting temperature is 500-600°C, and the roasting time is 4-8h; In step (9), the sintering temperature is 820°C, and the sintering time is 12h.

2. The method for recycling and reusing valuable metals from lithium manganese oxide materials as described in claim 1, characterized in that, In step (1), the molar ratio of the waste lithium manganate material powder to lithium hydroxide and nickel hydroxide is 3:1:

2.

3. The method for recycling and reusing valuable metals from lithium manganese oxide materials as described in claim 1, characterized in that, In step (2), the inert atmosphere is nitrogen and / or argon.

4. The method for recycling and reusing valuable metals from lithium manganese oxide materials as described in claim 1, characterized in that, In step (3), the mass ratio of the roasted material to water is 1:(5-10).

5. The method for recycling and reusing valuable metals from lithium manganese oxide materials as described in claim 1, characterized in that, In step (5), the organic acid is citric acid, the concentration of the citric acid solution is 50wt%, and the mass ratio of citric acid in the citric acid solution to waste lithium manganate material powder is 6:

1.

6. The method of recovering and reusing valuable metals from a lithium manganate material according to claim 1, wherein In step (6), the fluoride is at least one of manganese fluoride, nickel fluoride and lithium fluoride; The number of moles of fluorine in the fluoride is 2 times the total number of moles of calcium and magnesium.

7. The method of recovering and reusing valuable metals from a lithium manganate material according to claim 1, characterized by, In step (8), the pH of the mixed solution obtained by step (7) is adjusted to 6.5-7 using ammonia water, and is evaporated and concentrated to a gel at 75-80°C.

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