Method for improving micro powder on surface of lithium-rich manganese-based binary precursor and obtained precursor

Abstract

The invention discloses a method for improving micro powder on the surface of a lithium-rich manganese-based binary precursor and the obtained precursor. The method for improving the micro powder on the surface of the lithium-rich manganese-based binary precursor comprises the following steps: preparing a precipitant solution, a complexing agent solution, a nickel-manganese mixed salt solution containing hydrogen peroxide and a reaction base solution containing a precipitant and a complexing agent; and injecting the precipitant solution, the complexing agent solution and the nickel-manganese mixed salt solution containing hydrogen peroxide into a reaction base solution containing a precipitant and a complexing agent in a parallel flow manner, carrying out a co-precipitation reaction, stopping feeding after the particle size reaches a target particle size, and washing and drying to obtain the lithium-rich manganese-based binary precursor. The hydrogen peroxide is uniformly mixed with the nickel-manganese mixed salt solution in advance based on a coprecipitation method, so that the hydrogen peroxide can be in full contact with the nickel-manganese mixed salt solution in a reaction system, the oxidation is full, the reaction stability is ensured, and finally the lithium-rich manganese-based binary precursor with high specific surface area and less micro powder is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for improving surface micropowder of a lithium-rich manganese-based binary precursor and the obtained precursor. Background Art

[0002] Lithium-ion batteries are widely used in mobile phones, laptops, and some storage products due to their high specific energy, pollution-free, and long cycle life. They are also the power source for electric vehicles and power supply equipment. A series of studies on lithium-ion batteries have become a hot topic in the new energy industry in recent years. The control of micropowder in products is a process that needs to be strictly controlled in the production process of lithium-ion batteries. It can not only come from the raw materials that make up lithium-ion batteries, but also from foreign dust in the environment and mechanical dust introduced by equipment friction in the process. The content of micropowder directly determines the storage life of the battery. What is more serious is that the presence of micropowder may cause internal short circuits in the battery, causing the battery to heat up during charging and discharging, and eventually cause serious safety accidents such as battery explosions and spontaneous combustion of electric vehicles. The presence of micropowder affects the self-discharge of the battery in two ways: first, it increases the side reactions and micro-short circuits inside the battery, and as the amount of micropowder increases, the impact becomes more serious; second, it causes the battery capacity to decay and the internal resistance to increase during storage, accompanied by phenomena such as flatulence. Therefore, in actual production, the generation of micropowder in each process needs to be strictly controlled.

[0003] As one of the four core materials of the battery, the positive electrode material restricts the comprehensive performance of the battery. The positive electrode material can inherit the morphology and structural characteristics of the precursor, so the structure and preparation process of the precursor have a crucial influence on the performance of the positive electrode material. Due to the high manganese content in the lithium-rich manganese-based binary precursor, the oxide formed after the oxidation of manganese during the precursor reaction will precipitate on the surface of the precursor, and then form micropowder on the surface after washing, drying and other processes. By controlling the oxidation degree of the slurry during the precursor reaction, the micropowder situation on the surface of the precursor can be improved. Most of the existing lithium-rich manganese-based binary precursors are prepared by introducing air or nitrogen into the reactor to control the oxidation of the slurry during the reaction, but the degree of oxidation is difficult to control. If the oxidation is severe, it will lead to an increase in micropowder on the surface of the precursor, and insufficient oxidation will lead to a low BET of the precursor.

[0004] Therefore, how to improve the micropowder on the surface of high specific surface area lithium-rich manganese-based binary precursor is currently a more difficult problem. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies, propose a method for improving the surface powder of a lithium-rich manganese-based binary precursor and the obtained precursor, and solve the technical problem in the prior art that the degree of oxidation is difficult to control during the preparation of the lithium-rich manganese-based binary precursor, resulting in a large amount of powder often existing on the surface of the lithium-rich manganese-based binary precursor with a high specific surface area.

[0006] In a first aspect, the present invention provides a method for improving the surface powder of a lithium-rich manganese-based binary precursor, comprising the following steps: Preparing a precipitant solution, a complexing agent solution, a nickel-manganese mixed salt solution containing hydrogen peroxide, and a reaction base solution containing a precipitant and a complexing agent; The precipitant solution, the complexing agent solution and the nickel-manganese mixed salt solution containing hydrogen peroxide are injected into the reaction base liquid containing the precipitant and the complexing agent in parallel to carry out a co-precipitation reaction. When the particle size reaches the target particle size, the feeding is stopped, and a lithium-rich manganese-based binary precursor is obtained after washing and drying.

[0007] In a second aspect, the present invention provides a lithium-rich manganese-based binary precursor, which is obtained by the method for improving the surface powder of the lithium-rich manganese-based binary precursor provided by the first aspect of the present invention.

[0008] In a third aspect, the present invention provides an application of a lithium-rich manganese-based binary precursor, which is used to prepare a lithium-rich manganese-based binary positive electrode material.

[0009] Compared with the prior art, the beneficial effects of the present invention include: The present invention is based on a coprecipitation method, by pre-mixing hydrogen peroxide with a nickel-manganese mixed salt solution, so that the hydrogen peroxide can fully contact with the nickel-manganese mixed salt solution in the reaction system, fully oxidize, ensure the stability of the reaction, and finally obtain a lithium-rich manganese-based binary precursor with a high specific surface area and less fine powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 1 is a SEM image of the lithium-rich manganese-based binary precursor in Example 1 of the present invention; wherein (a) is a low-magnification image, and (b) is a high-magnification image; Figure 2 is a cross-sectional SEM image of the lithium-rich manganese-based binary precursor in Example 1 of the present invention; Figure 3 is a cross-sectional SEM image of the lithium-rich manganese-based binary precursor in Comparative Example 1 of the present invention; Figure 4 1 is a SEM image of the lithium-rich manganese-based binary precursor in Comparative Example 2 of the present invention; wherein (a) is a low-magnification image, and (b) is a high-magnification image. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0012] In a first aspect, the present invention provides a method for improving the surface powder of a lithium-rich manganese-based binary precursor, comprising the following steps: S1, preparing a precipitant solution, a complexing agent solution, a nickel-manganese mixed salt solution containing hydrogen peroxide, and a reaction base solution containing a precipitant and a complexing agent; S2. Inject the precipitant solution, the complexing agent solution and the nickel-manganese mixed salt solution containing hydrogen peroxide into the reaction base liquid containing the precipitant and the complexing agent in parallel to carry out a co-precipitation reaction. When the particle size reaches the target particle size, stop feeding. After washing and drying, obtain a lithium-rich manganese-based binary precursor.

[0013] The conventional method of controlling the degree of oxidation by passing gas into the reactor has the problem that the degree of oxidation is difficult to control and the gas entering the reactor cannot ensure that the slurry can fully contact with the gas. Different from the conventional method, the present invention is based on the coprecipitation method by pre-mixing hydrogen peroxide with the nickel-manganese mixed salt solution, so that the hydrogen peroxide can fully contact with the nickel-manganese mixed salt solution in the reaction system, fully oxidize, ensure the stability of the reaction, and finally obtain a lithium-rich manganese-based binary precursor with a high specific surface area and less micropowder.

[0014] In this embodiment, the nickel-manganese mixed salt solution containing hydrogen peroxide is obtained by mixing the nickel-manganese mixed salt solution and hydrogen peroxide.

[0015] Preferably, in the nickel-manganese mixed salt solution, the nickel salt is at least one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate.

[0016] Preferably, in the nickel-manganese mixed salt solution, the manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate.

[0017] Preferably, in the nickel-manganese mixed salt solution, the molar ratio of nickel to manganese is 1:(1.5-4).

[0018] Preferably, in the nickel-manganese mixed salt solution, the concentration of the nickel-manganese mixed salt is 85-125 g / L.

[0019] Preferably, the mass fraction of hydrogen peroxide is 25%-30%, further 27.5%.

[0020] Preferably, the volume ratio of the nickel-manganese mixed salt solution to hydrogen peroxide is 1:(0.0015-0.005).

[0021] Preferably, the mixing temperature is room temperature and the mixing time is 2-4 hours.

[0022] In this embodiment, the mass fraction of the precipitant solution is 28%-32%, including but not limited to 28%, 29%, 30%, 31%, 32%, etc.

[0023] In this embodiment, the mass fraction of the complexing agent solution is 16%-20%, including but not limited to 16%, 17%, 18%, 19%, 20%, etc.

[0024] In this embodiment, in the reaction base solution containing the precipitant and the complexing agent, the concentration of the precipitant is 0.04%-0.08%, and the concentration of the complexing agent is 1-1.5 g / L.

[0025] In this embodiment, the preparation process of the reaction base solution containing the precipitant and the complexing agent includes: adding 4m 3 Pure water, 6-10L of precipitant solution with a mass fraction of 28%-32% and 4-6kg of complexing agent are mixed evenly to obtain the reaction base liquid.

[0026] In this embodiment, before preparing the reaction base liquid containing the precipitant and the complexing agent, a protective gas is introduced into the reactor in advance. The present invention does not limit the type of protective gas, and those skilled in the art can select it according to actual conditions. In some specific embodiments of the present invention, the protective atmosphere is at least one of nitrogen, helium, argon, neon, and krypton.

[0027] In this embodiment, the precipitant is sodium hydroxide and the complexing agent is oxalic acid.

[0028] In this embodiment, during the coprecipitation reaction, every 4-5m 3 The reaction base liquid meter has a flow rate of 280-320 L / h of nickel-manganese mixed salt solution containing hydrogen peroxide, a flow rate of 100-120 L / h of precipitant solution, and a flow rate of 15-25 L / h of complexing agent solution.

[0029] In this embodiment, during the coprecipitation reaction, the pH is controlled at 9.9-10.2, and the concentration of the complexing agent is controlled at 1-3 g / L.

[0030] In this embodiment, during the coprecipitation reaction, the reaction temperature is 60-70°C.

[0031] In this embodiment, during the coprecipitation reaction, the stirring rate is 200-320 r / min.

[0032] In this embodiment, during the coprecipitation reaction, protective gas is continuously introduced into the reactor.

[0033] The present invention does not limit the type of protective gas, and those skilled in the art can select it according to actual conditions. In some specific embodiments of the present invention, the protective atmosphere is at least one of nitrogen, helium, argon, neon, and krypton.

[0034] Preferably, 2-6 m 3 A protective atmosphere was introduced into the reactor at a flow rate of / h.

[0035] In this embodiment, the target particle size D50 is 10-11 μm, including but not limited to 10 μm, 10.5 μm, 11 μm, etc.

[0036] In a second aspect, the present invention provides a lithium-rich manganese-based binary precursor, which is obtained by the method for improving the surface powder of the lithium-rich manganese-based binary precursor provided by the first aspect of the present invention.

[0037] In a third aspect, the present invention provides an application of a lithium-rich manganese-based binary precursor, which is used to prepare a lithium-rich manganese-based binary positive electrode material.

[0038] Example 1 (1) Mix nickel sulfate, manganese sulfate and water, stir thoroughly for 3 hours to obtain a nickel-manganese mixed salt solution (the molar ratio of nickel to manganese is 3:7, and the concentration of the nickel-manganese mixed salt is 110 g / L); add 27.5% hydrogen peroxide by volume at a volume ratio of 1:0.003 to the nickel-manganese mixed salt solution, stir thoroughly for 3 hours to obtain a hydrogen peroxide-nickel-manganese mixed salt solution; disperse sodium hydroxide in water to prepare a precipitant solution with a mass fraction of 30%; disperse oxalic acid in water to prepare a complexing agent solution with a mass fraction of 18%; introduce nitrogen into the reactor in advance for 2 hours, and add 4m 3 Pure water, 8L of base alkali (sodium hydroxide solution with a mass fraction of 30%) and 5kg of oxalic acid were added into the reactor to prepare the reaction base liquid.

[0039] (2) The hydrogen peroxide-nickel manganese mixed salt solution, the precipitant solution, and the complexing agent solution were added into the reactor with the prepared reaction base solution at flow rates of 300 L / h, 100-120 L / h, and 15-25 L / h, respectively, to carry out a co-precipitation reaction. The pH was controlled at 9.9-10.2 and the oxalate concentration was controlled at 1-3 g / L by adjusting the flow rates of the precipitant solution and the complexing agent solution. During the reaction, the precipitant solution was continuously heated at 3 m / s. 3 Nitrogen was introduced into the reactor at a flow rate of / h, the reaction temperature was 65°C, the stirring rate was 280r / min, and the feeding was stopped when the D50 grew to 10.5μm. Finally, a lithium-rich manganese-based binary precursor was obtained after washing and drying.

[0040] Example 2 (1) Nickel sulfate, manganese sulfate and water were mixed and stirred for 3 hours to obtain a nickel-manganese mixed salt solution (the molar ratio of nickel to manganese was 4:6, and the concentration of the nickel-manganese mixed salt was 110 g / L); hydrogen peroxide with a mass fraction of 27.5% was added to the nickel-manganese mixed salt solution at a volume ratio of 1:0.005, and stirred for 3 hours to obtain a hydrogen peroxide-nickel-manganese mixed salt solution; sodium hydroxide was dispersed in water to prepare a precipitant solution with a mass fraction of 28%; oxalic acid was dispersed in water to prepare a complexing agent solution with a mass fraction of 16%; nitrogen was introduced into the reactor in advance for 2 hours, and 4m 3 Pure water, 10L of base alkali (sodium hydroxide solution with a mass fraction of 28%) and 6kg of oxalic acid were added into the reactor to prepare the reaction base liquid.

[0041] (2) The hydrogen peroxide-nickel manganese mixed salt solution, the precipitant solution, and the complexing agent solution were added into the reactor with the prepared reaction base solution at flow rates of 280 L / h, 100-120 L / h, and 15-25 L / h, respectively, to perform a co-precipitation reaction. The pH was controlled at 9.9-10.2 and the oxalate concentration was controlled at 1-3 g / L by adjusting the flow rates of the precipitant solution and the complexing agent solution. During the reaction, the precipitant solution was continuously stirred at 2 m / s for 1 h. 3 Nitrogen was introduced into the reactor at a flow rate of / h, the reaction temperature was 60°C, the stirring rate was 320r / min, and the feeding was stopped when the D50 grew to 10μm. Finally, the lithium-rich manganese-based binary precursor was obtained after washing and drying.

[0042] Example 3 (1) Nickel sulfate, manganese sulfate and water were mixed and stirred for 3 hours to obtain a nickel-manganese mixed salt solution (the molar ratio of nickel to manganese was 2:8, and the concentration of the nickel-manganese mixed salt was 110 g / L); hydrogen peroxide with a mass fraction of 27.5% was added to the nickel-manganese mixed salt solution at a volume ratio of 1:0.0015, and stirred for 3 hours to obtain a hydrogen peroxide-nickel-manganese mixed salt solution; sodium hydroxide was dispersed in water to prepare a precipitant solution with a mass fraction of 32%; oxalic acid was dispersed in water to prepare a complexing agent solution with a mass fraction of 20%; nitrogen was introduced into the reactor in advance for 2 hours, and 4 m 3 Pure water, 6L of base alkali (sodium hydroxide solution with a mass fraction of 32%) and 4kg of oxalic acid were added into the reactor to prepare the reaction base liquid.

[0043] (2) The hydrogen peroxide-nickel manganese mixed salt solution, the precipitant solution, and the complexing agent solution were added into the reactor with the prepared reaction base solution at flow rates of 320 L / h, 100-120 L / h, and 15-25 L / h, respectively, to carry out a co-precipitation reaction. The pH was controlled at 9.9-10.2 and the oxalate concentration was controlled at 1-3 g / L by adjusting the flow rates of the precipitant solution and the complexing agent solution. During the reaction, the precipitant solution was continuously stirred at 6 m / s for 1 h. 3Nitrogen was introduced into the reactor at a flow rate of / h, the reaction temperature was 70°C, the stirring rate was 200r / min, and the feeding was stopped when the D50 grew to 11μm. Finally, a lithium-rich manganese-based binary precursor was obtained after washing and drying.

[0044] Comparative Example 1 Compared with Example 1, the only difference is that hydrogen peroxide is not used, and the nickel-manganese mixed salt solution, the precipitant solution, and the complexing agent solution are directly added to the reactor prepared with the reaction base liquid to carry out a co-precipitation reaction.

[0045] Comparative Example 2 Compared with Example 1, the only difference is that the volume ratio of the nickel-manganese mixed salt solution to the hydrogen peroxide is 1:0.01.

[0046] Performance Testing The performance of the lithium-rich manganese-based binary precursors obtained in the above Examples 1-3 and Comparative Examples 1-2 was tested. The test results are shown in Tables 1 and Figure 1-4 .

[0047] Table 1

[0048] Please refer to Table 1 and Figure 1-2 , through Table 1 and Figure 1-2 It can be seen that the lithium-rich manganese-based binary precursor prepared in the embodiment of the present invention has a high specific surface area and almost no micro-powder and small particle blocks are precipitated on the surface.

[0049] See also Figure 3 As shown in Table 1, compared with Example 1, no hydrogen peroxide was added to the nickel-manganese mixed salt solution of Comparative Example 1, no oxidation occurred during the reaction, the interior was relatively dense, and the specific surface area was relatively low.

[0050] See also Figure 4 As shown in Table 1, compared with Example 1, in the nickel-manganese mixed salt solution of Comparative Example 2, excessive amount of hydrogen peroxide was added, the reaction process was overoxidation, and a large amount of small particle powder was precipitated.

[0051] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for improving the surface powder of a lithium-rich manganese-based binary precursor, characterized in that: The following steps are involved: Preparing a precipitant solution, a complexing agent solution, a nickel-manganese mixed salt solution containing hydrogen peroxide, and a reaction base solution containing a precipitant and a complexing agent; The precipitant solution, the complexing agent solution and the nickel-manganese mixed salt solution containing hydrogen peroxide are injected into the reaction base liquid containing the precipitant and the complexing agent in parallel to carry out a co-precipitation reaction. When the particle size reaches the target particle size, the feeding is stopped, and a lithium-rich manganese-based binary precursor is obtained after washing and drying.

2. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: The nickel-manganese mixed salt solution containing hydrogen peroxide is obtained by mixing the nickel-manganese mixed salt solution and hydrogen peroxide; wherein, In the nickel-manganese mixed salt solution, the nickel salt is at least one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the manganese salt is at least one of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate; the molar ratio of nickel to manganese is 1:(1.5-4); the concentration of the nickel-manganese mixed salt is 85-125 g / L; and / or, The mass fraction of the hydrogen peroxide is 25%-30%; and / or, The volume ratio of the nickel-manganese mixed salt solution to hydrogen peroxide is 1:(0.0015-0.005); and / or, The mixing temperature is room temperature, and the mixing time is 2-4 hours.

3. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: The mass fraction of the precipitant solution is 28%-32%; and / or, The mass fraction of the complexing agent solution is 16%-20%; and / or, In the reaction base liquid containing the precipitant and the complexing agent, the concentration of the precipitant is 0.04%-0.08%, and the concentration of the complexing agent is 1-1.5 g / L.

4. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: The precipitant is sodium hydroxide; and / or, The complexing agent is oxalic acid.

5. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: During the coprecipitation reaction, every 4-5 m 3 The reaction base liquid meter has a flow rate of 280-320 L / h of nickel-manganese mixed salt solution containing hydrogen peroxide, a flow rate of 100-120 L / h of precipitant solution, and a flow rate of 15-25 L / h of complexing agent solution.

6. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: During the coprecipitation reaction, the pH is controlled at 9.9-10.2, and the concentration of the complexing agent is controlled at 1-3 g / L.

7. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: During the coprecipitation reaction, the reaction temperature is 60-70°C, the stirring rate is 200-320r / min, and the stirring speed is 2-6m 3 A protective atmosphere was introduced into the reactor at a flow rate of / h.

8. The method for improving the surface powder of lithium-rich manganese-based binary precursor according to claim 1, characterized in that: The target particle size D50 is 10-11 μm.

9. A lithium-rich manganese-based binary precursor, characterized in that: The lithium-rich manganese-based binary precursor is obtained by the method for improving the surface powder of the lithium-rich manganese-based binary precursor according to any one of claims 1 to 8.

10. An application of the lithium-rich manganese-based binary precursor as claimed in claim 9, characterized in that: The lithium-rich manganese-based binary precursor is used to prepare a lithium-rich manganese-based binary positive electrode material.

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