Method for preparing cobalt-free nickel-rich based lithium ion battery positive electrode material by microemulsion method

Abstract

The invention provides a method for preparing a cobalt-free nickel-rich based lithium ion battery positive electrode material by using a microemulsion method. The preparation method comprises the following steps: firstly, uniformly mixing and stirring a reaction raw material sodium carbonate solution with a solvent, a surfactant and a cosurfactant; slowly adding a reaction raw material nickel manganese sulfate solution, and reacting under the condition of high-speed stirring; filtering to obtain a nanoscale precursor; the precursor and excessive lithium hydroxide are mixed and ground, and then the positive electrode material is synthesized by adopting sectional type high-temperature calcination. Compared with a micron-sized positive electrode material obtained by a traditional method, the positive electrode material prepared by the preparation method disclosed by the invention is in a nanoscale size and has excellent electrochemical performance.

Description

Technical field:

[0001] The invention relates to the field of preparation of positive electrode materials for lithium ion batteries, and in particular to preparation of positive electrode materials for lithium ion batteries by a microemulsion method. Background technology:

[0002] Nowadays, fossil energy such as coal and oil is becoming increasingly scarce. Grasping the development and utilization of new energy will help lead the trend of the times. Among many new energy sources, rechargeable lithium-ion intercalation power batteries have undisputedly occupied a dominant position in the electrochemical energy storage market. Due to its advantages such as high energy density, long cycle life, light weight and green environmental protection, it is widely used in portable electronic devices, new energy vehicles, power grid energy storage systems and aerospace. In order to achieve the goal of "carbon peak and carbon neutrality" from the energy consumption end, the country has successively introduced a number of policies on the development of the new energy vehicle industry. With this support, new energy powered vehicles are gradually replacing traditional fossil energy vehicles, and the new energy vehicle market is rising rapidly. Due to the rapid growth of demand for high-performance batteries, improving their energy density and safety performance is the key to the commercial application of lithium-ion batteries, and these performances depend to a large extent on electrode active materials, especially positive electrode materials.

[0003] At present, nickel-rich cobalt-free cathode materials are mainly synthesized by coprecipitation, high-temperature solid-phase synthesis, solvent (water) thermal method, sol-gel method and other methods. Different preparation methods will have a great impact on the particle morphology, particle size, particle size distribution, tap density and the like of the materials. The particle size of the materials prepared by the above methods is mostly micrometer-level, while the microemulsion method can accurately control the particle size of the material, thereby preparing nanometer-level materials. Microemulsions are usually composed of surfactants, cosurfactants, solvents and water. In this system, two immiscible continuous media are divided into tiny spaces by surfactant amphiphilic molecules to form microreactors, the size of which can be controlled in the nanometer range. Under high-speed stirring, small droplets wrapped with two reactants collide and blend with each other, and the reactants react in the small droplets to form solid phase particles. Since the surface of the droplets is coated with surfactants, the surface of the generated solid phase is also coated with a layer of surfactant. It can effectively limit the nucleation, growth, aggregation, agglomeration and other processes of nanoparticles, thereby obtaining solid phase particles of precise size and having a certain condensed structure.

[0004] The preparation of lithium-ion battery positive electrode materials based on the microemulsion method is a new idea to improve material performance. Summary of the invention:

[0005] In view of the above technical problems and needs, the present invention provides a method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method. The positive electrode material prepared by the method can be nanoscale in size and has excellent electrochemical properties.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] (1) dissolving a certain proportion of sodium carbonate in water to obtain a sodium carbonate solution, and adding nickel sulfate and manganese sulfate to a certain concentration to prepare a nickel manganese sulfate solution;

[0008] (2) mixing the sodium carbonate solution, the solvent, the surfactant, and the co-surfactant in a container and stirring them uniformly;

[0009] (3) adding the nickel manganese sulfate solution dropwise into the reactor at a certain speed under argon protection, and maintaining continuous stirring;

[0010] (4) filtering the mixed solution after sufficient reaction, and washing it alternately with water and anhydrous ethanol repeatedly until it is clean, and drying the obtained precursor in a vacuum drying oven;

[0011] (5) Take out the fully dried precursor, weigh it, calculate the yield, add lithium hydroxide monohydrate in a certain proportion, grind it in a mortar and mix it thoroughly;

[0012] (6) The ground and mixed product is placed in a crucible and sent into a tubular furnace, where it is calcined in stages under sufficient oxygen flow to obtain a positive electrode material.

[0013] In the above technical solution, the concentration of the sodium carbonate solution in step (1) is 0.5-2 mol / L and the volume is 5 ml.

[0014] As a preferred embodiment, the concentration of the nickel manganese sulfate solution in step (1) is consistent with the concentration of the sodium carbonate solution, the nickel manganese ratio is X: (1-X) (1>X>0.5), and the volume is 5 ml.

[0015] As a preferred embodiment, the solvent in step (2) is cyclohexane, and the volume is 100 ml.

[0016] As a preferred embodiment, the surfactant in step (2) is cetyltrimethylammonium bromide (CTAB) with a mass of 2-6 g.

[0017] As a preferred embodiment, the co-surfactant in step (2) is n-butanol and the volume is 5 ml.

[0018] As a preferred embodiment, the dropping speed of the nickel manganese sulfate solution in step (3) is 0.1-0.5 ml / min.

[0019] As a preferred embodiment, in step (3), stirring is continued for 1-4 hours after the dropwise addition is completed, and the stirring speed is 400-1000 rpm.

[0020] As a preferred embodiment, the temperature of the vacuum drying oven in step (4) is 70-100°C.

[0021] As a preferred embodiment, the drying time in step (4) is 8-24 hours.

[0022] As a preferred embodiment, the excess ratio of lithium hydroxide monohydrate in step (5) is 3-5%.

[0023] As a preferred embodiment, an appropriate amount of anhydrous ethanol can be added during the grinding process in step (5) to make the grinding more complete.

[0024] As a preferred embodiment, in step (6), the calcination specifically comprises: first calcining at 500-600°C for 2-6h, and then calcining at 700-800°C for 10-15h.

[0025] This technical solution can effectively prepare high-nickel, cobalt-free, nickel-rich lithium-ion battery positive electrode materials through a microemulsion method, and make the materials reach nanoscale size at the microscopic level, thereby obtaining excellent electrochemical properties. Description of the drawings:

[0026] Figure 1 LiNi is the positive electrode material 0.9 Mn 0.1 Scanning electron microscope (SEM) image of O2 powder;

[0027] Figure 2 LiNi is the positive electrode material 0.8 Mn 0.2 Scanning electron microscope (SEM) image of O2 powder;

[0028] Figure 3 LiNi is the positive electrode material 0.7 Mn 0.3 Scanning electron microscope (SEM) image of O2 powder. Specific implementation method:

[0029] The present invention provides a method for preparing a high-nickel, cobalt-free, nickel-rich, lithium-ion battery positive electrode material by a microemulsion method. The method is further described below in conjunction with the accompanying drawings and specific examples of the specification.

[0030] In the following specific embodiments, the precursor is Ni X Mn (1-X) CO3, positive electrode material is LiNi X Mn (1-X) O2(1>X>0.5).

[0031] Example 1

[0032] 1) dissolving sodium carbonate in 5 ml of water at a concentration of 2 mol / L to prepare a sodium carbonate solution, and dissolving nickel sulfate and manganese sulfate in 5 ml of water at a nickel-manganese ratio of 9:1 and a total concentration of 2 mol / L to prepare a nickel-manganese sulfate solution;

[0033] 2) Mix the sodium carbonate solution, 100 ml of cyclohexane solvent, 2 g of CTAB surfactant, and 5 ml of n-butanol co-surfactant in a three-necked flask and stir evenly;

[0034] 3) Add the nickel manganese sulfate solution dropwise into the reactor at 0.1 ml / min under argon protection and keep stirring for 1 hour;

[0035] 4) Filter the mixed solution after sufficient reaction, and wash it alternately with water and anhydrous ethanol repeatedly until it is clean, and dry the obtained precursor in a vacuum drying oven at 70°C;

[0036] 5) Take out the fully dried precursor, weigh it, calculate the yield, and add lithium hydroxide monohydrate in an excess of 3%, grind and mix it evenly in a mortar, and add an appropriate amount of anhydrous ethanol to make the grinding more complete;

[0037] 6) The ground and mixed product is placed in a crucible into a tubular furnace and calcined in stages under sufficient oxygen conditions at a heating rate of 5°C / min. The product is first calcined at 500°C for 2 hours and then at 700°C for 10 hours. The product is cooled naturally to obtain the positive electrode material. Figure 1 This is a SEM image, from which it can be seen that the microstructure is at the nanoscale.

[0038] Example 2

[0039] 1) dissolving sodium carbonate in 5 ml of water at a concentration of 1 mol / L to obtain a sodium carbonate solution, and dissolving nickel sulfate and manganese sulfate in 5 ml of water at a nickel-manganese ratio of 8:2 at a concentration of 1 mol / L to obtain a nickel-manganese sulfate solution;

[0040] 2) Mix the sodium carbonate solution, 100 ml of cyclohexane solvent, 4 g of CTAB surfactant, and 5 ml of n-butanol co-surfactant in a three-necked flask and stir evenly;

[0041] 3) Add the nickel manganese sulfate solution dropwise into the reactor at 0.2 ml / min under argon protection and keep stirring for 2 h;

[0042] 4) Filter the mixed solution after sufficient reaction, and wash it alternately with water and anhydrous ethanol repeatedly until it is clean, and dry the obtained precursor in a vacuum drying oven at 80°C;

[0043] 5) Take out the fully dried precursor, weigh it, calculate the yield, add lithium hydroxide monohydrate in an excess of 4%, grind and mix it evenly in a mortar, and add an appropriate amount of anhydrous ethanol to make the grinding more complete;

[0044] 6) The ground and mixed product is placed in a crucible into a tubular furnace and calcined in stages under sufficient oxygen conditions at a heating rate of 5°C / min. The product is first calcined at 550°C for 4 hours and then at 750°C for 12 hours. The product is cooled naturally to obtain the positive electrode material. Figure 2 This is a SEM image, from which it can be seen that the microstructure is at the nanoscale.

[0045] Example 3

[0046] 1) dissolving sodium carbonate in 5 ml of water at a concentration of 0.5 mol / L to prepare a sodium carbonate solution, and dissolving nickel sulfate and manganese sulfate in 5 ml of water at a nickel-manganese ratio of 7:3 and a total concentration of 0.5 mol / L to prepare a nickel-manganese sulfate solution;

[0047] 2) Mix the sodium carbonate solution, 100 ml of cyclohexane solvent, 6 g of CTAB surfactant, and 5 ml of n-butanol co-surfactant in a three-necked flask and stir evenly;

[0048] 3) Add the nickel manganese sulfate solution dropwise into the reactor at 0.5 ml / min under argon protection and keep stirring for 4 hours;

[0049] 4) Filter the mixed solution after sufficient reaction, and wash it alternately with water and anhydrous ethanol repeatedly until it is clean, and dry the obtained precursor in a vacuum drying oven at 100° C.;

[0050] 5) Take out the fully dried precursor, weigh it, calculate the yield, and add lithium hydroxide monohydrate in an excess of 5%, grind and mix it evenly in a mortar, and add an appropriate amount of anhydrous ethanol to make the grinding more complete;

[0051] 6) The ground and mixed product is placed in a crucible into a tubular furnace and calcined in stages under sufficient oxygen conditions at a heating rate of 5°C / min. The product is first calcined at 600°C for 6 hours and then at 800°C for 15 hours. The product is then cooled naturally to obtain the positive electrode material.

Claims

1. A method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method, characterized in that: The following steps are involved: 1) dissolving a certain proportion of sodium carbonate in water to obtain a sodium carbonate solution, and adding nickel sulfate and manganese sulfate to prepare a nickel manganese sulfate solution at a certain concentration; 2) mixing the sodium carbonate solution, the solvent, the surfactant and the co-surfactant in a container and stirring them uniformly; 3) adding the nickel manganese sulfate solution dropwise into the reactor at a certain speed under argon protection, and maintaining continuous stirring; 4) Filter the mixed solution after sufficient reaction, and wash it alternately with water and anhydrous ethanol repeatedly until it is clean, and dry the obtained precursor in a vacuum drying oven; 5) Take out the fully dried precursor, weigh it, calculate the yield, add lithium hydroxide monohydrate in a certain proportion, grind it in a mortar and mix it evenly; 6) The ground and mixed product is placed in a crucible and sent to a tube furnace, where it is calcined in stages under sufficient oxygen flow to obtain a positive electrode material.

2. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In the step 1), the concentration of the sodium carbonate solution is 0.5-2 mol / L, and the volume is 5 ml; the concentration of the nickel manganese sulfate solution is consistent with the concentration of the sodium carbonate solution, the nickel manganese ratio is X: (1-X) (1>X>0.5), and the volume is 5 ml.

3. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In the step 2), the solvent is cyclohexane with a volume of 100 ml; the surfactant is cetyltrimethylammonium bromide (CTAB) with a mass of 2-6 g; and the co-surfactant is n-butanol with a volume of 5 ml.

4. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In the step 3), the nickel manganese sulfate solution is added at a rate of 0.1-0.5 ml / min, and after the addition is completed, stirring is continued for 1-4 hours at a rate of 400-1000 rpm.

5. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In the step 4), the temperature of the vacuum drying oven is 70-100° C., and the drying time is 8-24 hours.

6. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In step 5), the excess ratio of lithium hydroxide monohydrate is 3-5%. During the grinding process, an appropriate amount of anhydrous ethanol can be added to make the grinding more complete.

7. The method for preparing a cobalt-free nickel-rich lithium-ion battery positive electrode material by a microemulsion method according to claim 1, characterized in that In the step 6), the calcination specifically includes: first calcining at 500-600° C. for 2-6 hours, and then calcining at 700-800° C. for 10-15 hours.

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