Lithium-rich manganese-based positive electrode material, preparation method therefor, and use thereof

Abstract

Provided in the present application are a lithium-rich manganese-based positive electrode material, a preparation method therefor, and the use thereof. The preparation method comprises the following steps: (1) injecting in parallel flows a solution of soluble mixed salts, a precipitant, a complexing agent and an organic buffer solution into a base solution and performing a co-precipitation reaction, so as to obtain a precursor; and (2) mixing the precursor with a lithium source, and carrying out sintering treatment to obtain the lithium-rich manganese-based positive electrode material. The present application uses the co-precipitation process to avoid introduction of impurities; in addition, adding a proper organic buffer solution and a low-concentration complexing agent as an auxiliary during the reaction process enables the preparation of various types of lithium-rich manganese-based positive electrode materials having high capacity and excellent cycle performance.

Description

A lithium-rich manganese-based cathode material, its preparation method and application Technical Field

[0001] This application belongs to the technical field of lithium-ion batteries, for example, a lithium-rich manganese-based cathode material, its preparation method and application. Background Art

[0002] Under the dual impacts of the limited reserves of traditional energy sources such as oil and coal and carbon emissions on the global ecological environment, humans have gradually realized the importance of finding clean energy; currently, photovoltaic power generation and wind power generation have a relatively large impact on the power grid load due to weather and terrain. Lithium-ion batteries are widely used in fields such as 3C mobile intelligent terminals, power tools, electric vehicles, and energy storage due to their comprehensive advantages such as high working voltage, small volume, long cycle life, high energy density, and low self-discharge, and can play an important role in peak shaving and valley filling of the power grid. Therefore, the research on high-capacity lithium batteries has become a current hot topic.

[0003] The cathode material is an important factor determining a series of key indicators such as the energy density, cycle performance, and cost of lithium batteries, and the precursor is the main raw material for preparing the cathode material of the battery. Currently, the discharge capacity of commercial lithium batteries is mostly lower than 200 mAh / g, and the working voltage generally does not exceed 4.3V.

[0004] CN112342605A discloses a low-cost and low-cobalt single-crystal nickel cobalt manganese ternary cathode material and its preparation method. A certain stoichiometric ratio of nickel source, cobalt oxide, manganese oxide, lithium source, and M dopant are added to a grinder for wet grinding until the slurry with the particle size of insoluble matter ≤ 0.5 μm is obtained, and then spray drying is carried out to obtain an energy-saving, low-cost and low-cobalt lithium-containing ternary precursor A. A is sintered at high temperature under rich oxygen, and after pulverization treatment, a highly dispersed single-crystal ternary material matrix B is obtained; X is dry-coated on B, and then solid-phase sintering and pulverization treatment are carried out in a low-temperature air atmosphere to obtain a low-cost and low-cobalt single-crystal cathode material.

[0005] CN103943844A discloses a lithium-rich manganese-based binary cathode material, its preparation method and application. The chemical formula of the cathode material is Li 1+x Ni y Mn 0.8-y O2(0 < x < y < 0.8). Its preparation process is to use the sol-gel method to prepare the precursor in an ethanol or deionized water solvent, and after low-temperature pre-sintering and ball milling, the prepared cathode material is obtained by high-temperature solid-phase sintering.

[0006] The cathode materials prepared by the methods described in the above solutions will introduce problems such as magnetic foreign matters and uneven element distribution, which have a greater impact on the battery performance.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a lithium-rich manganese-based positive electrode material and its preparation method and application. This application avoids the introduction of impurities through the co-precipitation method. By adding a suitable organic buffer solution supplemented by a low-concentration chelating agent during the reaction process, various types of lithium-rich manganese-based positive electrode materials with high capacity and excellent cycle performance can be prepared.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, an embodiment of the present application provides a method for preparing a lithium-rich manganese-based positive electrode material, the preparation method comprising the following steps:

[0012] (1) injecting a soluble mixed salt solution, a precipitant, a complexing agent, and an organic buffer solution into the bottom liquid in parallel to perform a co-precipitation reaction to obtain a precursor;

[0013] (2) The precursor is mixed with a lithium source and sintered to obtain the lithium-rich manganese-based positive electrode material.

[0014] The embodiment of the present application prepares a homogeneous lithium-rich manganese-based ternary precursor or a cobalt-free lithium-rich manganese-based precursor by a co-precipitation method, and adds an organic buffer solution during the co-precipitation process. While assisting the use of a low-concentration chelating agent, the use of the chelating agent is reduced, thereby avoiding the generation of toxic gases such as ammonia by the use of common chelating agents. At the same time, the buffer solution can avoid drastic changes in pH in the system, and prepare a precursor with uniform morphology. The present application can regulate lithium-rich manganese-based ternary positive electrode materials or lithium-rich manganese-based binary positive electrode materials with different physical and chemical indicators through process adjustment and equipment type, thereby solving the current problem of power battery life anxiety.

[0015] In one embodiment, the solute of the soluble mixed salt solution in step (1) includes any one of nickel salt, cobalt salt or manganese salt, or a combination of at least two of them.

[0016] In one embodiment, when the lithium-rich manganese-based positive electrode material is a lithium-rich manganese-based ternary positive electrode material, the solute of the soluble mixed salt solution includes nickel salt, cobalt salt and manganese salt.

[0017] In one embodiment, when the lithium-rich manganese-based positive electrode material is a lithium-rich manganese-based binary positive electrode material, the solute of the soluble mixed salt solution includes nickel salt and manganese salt.

[0018] In one embodiment, the total molar concentration of metal ions in the mixed salt solution in step (1) is 1.5 to 3 mol / L, for example, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L.

[0019] In one embodiment, the precipitant in step (1) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0020] In one embodiment, the molar concentration of the precipitant is 8 to 12 mol / L, for example, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L.

[0021] In one embodiment, the complexing agent includes any one or a combination of at least two of ammonia water, acetic acid, sodium citrate, ethylenediamine, EDTA, oxalic acid or citric acid.

[0022] In one embodiment, the molar concentration of the complexing agent is 1 to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L.

[0023] In one embodiment, the organic buffer solution includes any one of tris(hydroxymethylaminomethane), 4-hydroxyethylpiperazineethanesulfonic acid or 2-(diethanolamino)ethanesulfonic acid chloride, 2-(diethanolamino)ethanesulfonic acid or N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, or a combination of at least two thereof.

[0024] In one embodiment, the molar concentration of the organic buffer solution is 0.1-0.3 mol / L, for example, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L.

[0025] In one embodiment, the base solution includes a precipitant, a complexing agent, and a solvent.

[0026] In one embodiment, the mass concentration of the complexing agent in the base solution is 0.1-0.5 g / L, for example, 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L or 0.5 g / L.

[0027] In one embodiment, the pH of the base solution is 9-12, for example, 9, 9.5, 10, 11 or 12.

[0028] In one embodiment, nitrogen is introduced during the coprecipitation reaction in step (1) and stirring is performed.

[0029] In one embodiment, the stirring speed is 100-1000 rpm, for example, 100 rpm, 200 rpm, 500 rpm, 800 rpm or 1000 rpm.

[0030] In one embodiment, the coprecipitation reaction temperature is 30-100°C, for example, 30°C, 50°C, 70°C, 80°C or 100°C.

[0031] In one embodiment, the endpoint of the coprecipitation reaction is that the particle size of the system particles is 2 to 20 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm or 20 μm.

[0032] In one embodiment, the lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

[0033] In one embodiment, the ratio of the total molar amount of the metal elements in the precursor to the lithium element in the lithium source is 1.02 to 1.2:1, for example, 1.02:1, 1.05:1, 1.1:1, 1.15:1 or 1.2:1.

[0034] In one embodiment, the temperature of the sintering treatment in step (2) is 600-900°C, for example, 600°C, 650°C, 700°C, 800°C or 900°C.

[0035] In one embodiment, the sintering treatment time is 10 to 15 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0036] In a second aspect, an embodiment of the present application provides a lithium-rich manganese-based positive electrode material, which is prepared by the method described in the first aspect.

[0037] In a third aspect, an embodiment of the present application provides a positive electrode plate, which comprises the lithium-rich manganese-based positive electrode material as described in the second aspect.

[0038] In a fourth aspect, an embodiment of the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet as described in the third aspect.

[0039] Compared with the prior art, this application has the following beneficial effects:

[0040] The method described in the present application is applicable to the preparation of lithium-rich manganese-based ternary positive electrode materials and lithium-rich manganese-based binary positive electrode materials in different proportions. While reducing the use of complexing agents, it avoids the generation of waste gas. At the same time, the reaction conditions are stable, and the uniformity and stability of the obtained materials are greatly improved.

[0041] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0043] FIG1 is an SEM image of the lithium-rich manganese-based ternary positive electrode material described in Example 1 of the present application.

[0044] FIG2 is an SEM image of the lithium-rich manganese-based binary positive electrode material described in Example 2 of the present application. DETAILED DESCRIPTION

[0045] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0046] Example 1

[0047] This embodiment provides a lithium-rich manganese-based ternary positive electrode material, and the preparation method of the lithium-rich manganese-based ternary positive electrode material is as follows:

[0048] (1) A sulfate solution B containing nickel ions, cobalt ions, and manganese ions with a total ion concentration of 2 mol / L is prepared, wherein the molar ratio of nickel ions, cobalt ions, and manganese ions is 38:2:60, an industrial liquid alkali with a concentration of 10 mol / L is used as a precipitant solution C, a 2 mol / L ammonia water is used as a complexing agent solution D, and a tris (hydroxymethyl)aminomethane buffer solution with a concentration of 0.2 mol / L is used as a solution E. A base solution A containing a certain amount of precipitant solution and complexing agent solution is prepared in a reactor. The pH of A is controlled at 11, the ammonia concentration of A is 0.3 g / L, the temperature of A is 50° C., and nitrogen is introduced as a protective gas. The mixed salt solution B, the precipitant solution C, the complexing agent solution D, and the solution E are added concurrently to the above-mentioned reactor. A coprecipitation reaction is carried out with a stirring blade at a speed of 350 rpm to obtain precursor particles with a target particle size D50 of 12 μm. The obtained nickel-cobalt-manganese precursor is washed, dried, and subjected to treatments such as removing magnetic foreign matter to obtain post-treated precursor particles.

[0049] (2) The precursor and Li2CO3 powder were uniformly mixed according to the element ratio, and calcined at 800°C in air atmosphere for 12 hours to obtain a lithium-rich manganese-based ternary positive electrode material. The SEM image of the lithium-rich manganese-based ternary positive electrode material is shown in Figure 1.

[0050] Example 2

[0051] This embodiment provides a lithium-rich manganese-based binary positive electrode material, and the preparation method of the lithium-rich manganese-based positive electrode material is as follows:

[0052] (1) A sulfate solution B containing nickel ions and manganese ions with a total ion concentration of 2 mol / L was prepared, wherein the molar ratio of nickel ions to manganese ions was 35:65, an industrial liquid alkali with a concentration of 10 mol / L was used as a precipitant solution C, a 2.5 mol / L ammonia solution was used as a complexing agent solution D, and the concentration of the 2-(diethanolamino)ethanesulfonic acid buffer solution was 0.25 mol / L. A base solution A containing a certain amount of precipitant solution and complexing agent solution was prepared in a reactor, the pH of A was controlled at 11.3, the ammonia concentration of A was 0.35 g / L, and the solution E was prepared. The temperature of A was 40°C, and nitrogen was introduced as a protective gas. The mixed salt solution B, the precipitant solution C, the complexing agent solution D, and the solution E are added to the above-mentioned reactor in parallel, and a co-precipitation reaction is carried out at a stirring blade speed of 420 rpm to obtain precursor particles with a particle size of 10 μm and a target particle size D50. The obtained spherical nickel-manganese precursor is washed, dried, and subjected to treatments such as removing magnetic foreign matter to obtain spherical precursor particles;

[0053] (2) The precursor and Li2CO3 powder were uniformly mixed according to the element ratio, and calcined at 800°C in air atmosphere for 12 hours to obtain a lithium-rich manganese-based binary positive electrode material. The SEM image of the lithium-rich manganese-based binary positive electrode material is shown in Figure 2.

[0054] Example 3

[0055] The only difference between this embodiment and embodiment 1 is that the molar ratio of nickel ions, cobalt ions and manganese ions is 8:1:1, and other conditions and parameters are exactly the same as those in embodiment 1.

[0056] Example 4

[0057] The only difference between this embodiment and embodiment 2 is that the molar ratio of nickel ions to manganese ions is 30:70, and other conditions and parameters are exactly the same as those in embodiment 1.

[0058] Example 5

[0059] The only difference between this embodiment and embodiment 1 is that the concentration of the organic buffer solution is 0.05 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0060] Example 6

[0061] The only difference between this embodiment and embodiment 1 is that the concentration of the organic buffer solution is 0.5 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0062] Comparative Example 1

[0063] In this comparative example, a solid phase sintering method was used to prepare a lithium-rich manganese-based ternary positive electrode material. The preparation method is as follows:

[0064] (1) Lithium oxide and three oxides of nickel, cobalt, and manganese are mixed and ball-milled in proportion; wherein the mass ratio of Li:Ni:Co:Mn is 1.2:0.304:0.016:0.48. The nickel oxide is NiO, the cobalt oxide is Co3O4, and the manganese oxide is MnO. During the implementation process, the ball-to-material mass ratio used in the ball milling is 2:1, the ball mill speed is 200 rpm, and the ball milling time is 3 hours. The appropriate ball milling conditions ensure that the four oxides used to prepare the positive electrode material can be fully mixed and uniform. The particle size of the ball-milled material is 2 μm, which is more likely to form a new single crystal structure. The ball-milled material is sintered for the first time at 500°C. The product after the first sintering is sintered for the second time at 720°C. Finally, the product after the second sintering is naturally cooled to room temperature, thereby obtaining the lithium-rich manganese-based ternary positive electrode material.

[0065] Comparative Example 2

[0066] The only difference between this comparative example and Example 1 is that no organic buffer solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0067] Performance testing:

[0068] The electrode materials, acetylene black, and polyvinylidene fluoride prepared in the Examples and Comparative Examples were added dropwise to N-methyl-2-pyridine to prepare a solution. The solution was then evenly applied to aluminum foil, dried, and punched into thin sheets. Coin cells were assembled in an Ar glove box with the battery electrode, elemental lithium sheet, glass fiber separator, electrolyte (LiClO4) gasket, spring, and battery casing. The cells were tested, and the test results are shown in Table 1.

[0069] Table 1

[0070] As can be seen from Table 1, from Examples 1-4, the method described in the present application is applicable to the preparation of lithium-rich manganese-based ternary positive electrode materials and lithium-rich manganese-based binary positive electrode materials in different proportions, and the cycle performance of the obtained lithium-rich manganese-based positive electrode materials is greatly improved.

[0071] By comparison between Example 1 and Examples 5-6, it can be seen that in the preparation process of the lithium-rich manganese-based positive electrode material described in the present application, the concentration of the buffer solution will affect the performance of the obtained material. The molar concentration of the organic buffer solution is controlled at 0.1-0.3 mol / L, and the performance of the lithium-rich manganese-based positive electrode material obtained is better. If the molar concentration of the organic buffer solution is too low, the buffering effect is not ideal, and the pH of the system cannot be well controlled, resulting in a decrease in the quality of the precursor. If the molar concentration of the organic buffer solution is too high, the buffer solution will react with the chelating agent, the chelating agent effect will decrease, and the by-products will increase, resulting in a decrease in material performance.

[0072] From the comparison between Example 1 and Comparative Example 1, it can be seen that the co-precipitation method used in the present application to prepare the lithium-rich manganese-based positive electrode material can produce a lithium-rich manganese-based positive electrode material with better uniform morphology and better stability than the traditional solid-phase sintering method.

[0073] By comparing Example 1 and Comparative Example 1, it can be seen that the present application adds an organic buffer solution during the co-precipitation process, which not only assists the use of a low-concentration complexing agent, but also reduces the use of the complexing agent, thereby avoiding the generation of toxic gases such as ammonia by common complexing agents. At the same time, the buffer solution can avoid drastic changes in pH in the system, thereby preparing a precursor with uniform morphology.

[0074] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a lithium-rich manganese-based positive electrode material, the preparation method comprising the following steps: (1) injecting a soluble mixed salt solution, a precipitant, a complexing agent and an organic buffer solution into the bottom liquid in parallel to perform a co-precipitation reaction to obtain a precursor; (2) The precursor is mixed with a lithium source and subjected to sintering treatment to obtain the lithium-rich manganese-based positive electrode material.

2. The preparation method according to claim 1, wherein The solute of the soluble mixed salt solution in step (1) includes any one of nickel salt, cobalt salt or manganese salt, or a combination of at least two of them.

3. The preparation method according to claim 1 or 2, wherein: When the lithium-rich manganese-based positive electrode material is a lithium-rich manganese-based ternary positive electrode material, the solute of the soluble mixed salt solution includes nickel salt, cobalt salt and manganese salt.

4. The preparation method according to claim 1 or 2, wherein When the lithium-rich manganese-based positive electrode material is a lithium-rich manganese-based binary positive electrode material, the solute of the soluble mixed salt solution includes nickel salt and manganese salt.

5. The preparation method according to any one of claims 1 to 4, wherein: The total molar concentration of metal ions in the soluble mixed salt solution in step (1) is 1.5 to 3 mol / L.

6. The preparation method according to any one of claims 1 to 5, wherein: The precipitant in step (1) comprises sodium hydroxide solution and / or potassium hydroxide solution; Optionally, the molar concentration of the precipitant is 8 to 12 mol / L; Optionally, the complexing agent includes any one or a combination of at least two of ammonia water, acetic acid, sodium citrate, ethylenediamine, EDTA, oxalic acid or citric acid; Optionally, the molar concentration of the complexing agent is 1 to 3 mol / L; Optionally, the organic buffer solution includes any one or a combination of at least two of tris(hydroxymethyl)aminomethane, 4-hydroxyethylpiperazineethanesulfonic acid, 2-(diethanolamino)ethanesulfonic acid chloride or 2-(diethanolamino)ethanesulfonic acid or N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid; Optionally, the molar concentration of the organic buffer solution is 0.1 to 0.3 mol / L; Optionally, the base solution includes a precipitant, a complexing agent and a solvent; Optionally, the mass concentration of the complexing agent in the base solution is 0.1 to 0.5 g / L; Optionally, the pH of the base solution is 9-12.

7. The preparation method according to any one of claims 1 to 6, wherein: During the coprecipitation reaction in step (1), nitrogen is introduced and stirring is performed; Optionally, the stirring speed is 100 to 1000 rpm; Optionally, the coprecipitation reaction temperature is 30 to 100°C; Optionally, the endpoint of the coprecipitation reaction is that the particle size of the system particles is 2 to 20 μm.

8. The preparation method according to any one of claims 1 to 7, wherein: The lithium source in step (2) includes lithium hydroxide and / or lithium carbonate; Optionally, the ratio of the total molar amount of metal elements in the precursor to the lithium element in the lithium source is 1.02 to 1.2:

1.

9. The preparation method according to any one of claims 1 to 8, wherein: The sintering temperature in step (2) is 600-900° C. Optionally, the sintering treatment time is 10 to 15 hours.

10. A lithium-rich manganese-based positive electrode material, wherein the lithium-rich manganese-based positive electrode material is prepared by the method according to any one of claims 1 to 9. 11 . A positive electrode plate, comprising the lithium-rich manganese-based positive electrode material according to claim 10 . 12 . A lithium ion battery, comprising the positive electrode sheet according to claim 11 .

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