Preparation method of sheet-shaped lithium ion battery positive electrode material precursor

Abstract

The invention discloses a preparation method of a sheet-shaped lithium ion battery positive electrode material precursor. The main component of the positive electrode material precursor is nickel manganese aluminum hydroxide, the chemical formula is (NixMnyAl (1-x-y)) OH2, x is 0.3-0.9, y is 0.1-0.7, and x + y is less than or equal to 1. The nickel-manganese-aluminum hydroxide precursor is in a uniform sheet shape, the length of a single primary particle can be controlled between 250 nm and 800 nm, and the primary particle forms a secondary sphere in a penetrating and stacking mode. Primary particles of the flaky nickel-manganese-aluminum hydroxide precursor are characterized in that the flaky nickel-manganese-aluminum hydroxide precursor is uniform in flaky morphology and controllable in flaky size; the sintered positive electrode material has the advantages of high capacity, low excess lithium and long cycle life.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a method for preparing a precursor of a lithium-ion battery cathode material with a flaky morphology. Background Art

[0002] Lithium-ion batteries are considered the best technology for sustainable transportation power batteries because they can provide high energy and power, making them lighter and smaller than other rechargeable batteries. As an upstream manufacturing link of lithium-ion batteries, since 80% of the physical and electrochemical properties of the cathode material are inherited from the ternary cathode precursor material, it is crucial to prepare high-quality cathode precursor materials.

[0003] Currently, the surfaces of the secondary spheres synthesized by the wet method of the precursor are all strip-shaped, but there are few reports on the secondary spheres with a flaky morphology. Compared with the strip-shaped ones, the secondary spheres with a flaky morphology have a higher specific surface area and tap density, and are also conducive to forming the precursor of the core-shell layer structure and the transition layer structure subsequently, providing diversity for the modification of the precursor. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a hydroxide precursor with a flaky morphology, the flaky morphology of the precursor is uniform, and the flaky size is controllable; after being sintered into a cathode material, it has the advantages of high capacity, low excess lithium, and high cycle life.

[0005] The present invention provides a precursor of a lithium-ion battery cathode material with a flaky morphology, characterized in that the chemical formula of the precursor is Ni x Mn y Al 1-x-y OH2, where 0.3 ≤ x ≤ 0.9, 0.1 ≤ y ≤ 0.7, and x + y ≤ 1.

[0006] Furthermore, the length of a single primary particle of the precursor is controlled between 250 nm and 800 nm, and the primary particles form secondary spheres in an interpenetrating and stacked manner, and the particle size of the precursor is 2.5 - 8 μm.

[0007] The present invention also provides a method for preparing the precursor of the lithium-ion battery cathode material with the above flaky morphology, including the following steps:

[0008] Continuously introduce a mixed solution containing a soluble nickel salt, a soluble manganese salt, a soluble cobalt salt or a soluble aluminum salt, a precipitant solution and a complexing agent solution into a reaction device for reaction; when the particle size of the solid particles in the reaction solution reaches 0.5 - 1.2 μm, start introducing a gas with an oxygen content concentration of 5% - 10%, and at the same time switch the flow rate of the concentration of the precipitant solution; when the particle size of the solid particles in the reaction solution reaches 2.0 - 3.0 μm, start introducing a gas with an oxygen content concentration of 1% - 5% to obtain the precursor.

[0009] Further, during the reaction process, the pH of the reaction solution is 9.5 - 11.5; the reaction temperature is 45 - 60 °C.

[0010] Further, the total concentration of the mixed solution containing soluble nickel salt, soluble cobalt salt and soluble manganese salt is 1.5 - 2.5 mol / L.

[0011] Further, the precipitating agent is sodium hydroxide solution, the complexing agent is ammonia water solution, the concentration of the precipitating agent is 5 - 10 mol / L, and the concentration of the complexing agent is 20 - 30 mol / L.

[0012] Beneficial effects

[0013] The present invention relates to a preparation method of a precursor of a cathode material with a flaky morphology, and its main component is a nickel manganese aluminum hydroxide precursor. The length of a single primary particle is controlled between 250 nm and 800 nm, and the primary particles form secondary spheres in an interpenetrating and stacked manner. The flaky nickel manganese aluminum hydroxide precursor of the present invention is characterized in that its primary particles have a uniform flaky morphology and controllable flaky size; after being sintered into a cathode material, it has the advantages of high capacity, low excess lithium, and high cycle life. In view of this, the present invention is specifically proposed.

[0014] The key point of the present invention is to adjust the reaction atmosphere during the reaction process by gases with different oxygen contents, and then adjust the oxygen content in the reaction atmosphere. Under reaction atmospheres with different oxygen contents, the oxidation degree of Mn element is different, and thus shows +2 valence state, +3 valence state and intermediate transition valence states. The crystal structures of hydroxides with different Mn valence states are different. When the Mn element is close to the +3 valence state, its hydroxide shows a flaky structure, and at the same time, Ni / Co hydroxides grow based on the structure of Mn element hydroxide. Therefore, by controlling the change of oxygen content in the reaction atmosphere, different valence states of Mn element and the shape of its hydroxide precipitation can be realized, and primary particle morphologies with various different flaky degrees can be formed. At the same time, the stacking manner of primary particles is controlled by temperature and rotation speed. Brief description of the drawings

[0015] Figure 1 Surface morphology of the flaky nickel manganese hydroxide precursor prepared in Example 1;

[0016] Figure 2 Surface morphology of the flaky nickel manganese hydroxide precursor prepared in Comparative Example 1;

[0017] Figure 3 Morphology after sintering in Comparative Example 1;

[0018] Figure 4 Morphology after sintering in Example 1;

[0019] Figure 5Long-cycle life trends of Example 1 and Comparative Example 1;

[0020] Figure 6 Rate charge-discharge performance of Example 1 and Comparative Example 1. Detailed implementation manners

[0021] The present invention will be described in detail below in conjunction with specific examples and comparative examples.

[0022] Example 1

[0023] 7.5 L of water, 350 ml of sodium hydroxide solution and 200 mL of ammonia water were added into a reaction kettle as the bottom liquid. Then, a mixed solution containing nickel sulfate and manganese sulfate (the mixing ratio of the mixed solution was Ni0.9Mn0.1, and the concentration of the mixed solution was 1.5 mol / L), an ammonia water solution (30 mol / L) and an aqueous sodium hydroxide (8 mol / L) solution were simultaneously introduced into the reaction kettle. The flow rate of the mixed solution was 500 mL / h, the flow rate of the sodium hydroxide solution was 400 mL / h, and the flow rate of the ammonia water solution was 100 mL / h. The system reacted under the conditions of 45 °C, a stirring rate of 1400 rpm, and a pH of 11.5. When the particle size of the solid particles in the reaction solution reached 1.2 μm, a gas with an oxygen content concentration of 10% was introduced, and at the same time, the sodium hydroxide solution (4 mol / L, flow rate 300 ml / min) was switched; when the particle size of the solid particles in the reaction solution reached 2.0 μm, a gas with an oxygen content concentration of 4% was introduced, and other conditions remained unchanged, obtaining the flaky nickel-manganese hydroxide precursor. Subsequently, the solid particles were washed, dried, sieved and demagnetized to obtain the flaky nickel-manganese hydroxide precursor, as Figure 1 shown.

[0024] Example 2

[0025] 7.5 L of water, 450 ml of sodium hydroxide solution and 235 mL of ammonia water were added to the reaction kettle as the bottom liquid. Then, a mixed solution containing nickel sulfate, manganese sulfate and aluminum sulfate (the mixing ratio of the mixed solution was Ni0.6Mn0.2Al0.2, and the concentration of the mixed solution was 1.8 mol / L), ammonia water solution (26 mol / L) and sodium hydroxide (8 mol / L) aqueous solution were simultaneously introduced into the reaction kettle. The flow rate of the mixed solution was 400 mL / h, the flow rate of the sodium hydroxide solution was 300 mL / h, and the flow rate of the ammonia water solution was 150 mL / h. The system reacted under the conditions of 55 °C, a stirring rate of 1600 rpm, and a pH of 11.8. When the particle size of the solid particles in the reaction solution reached 1.0 μm, a gas with an oxygen content concentration of 7% was introduced, and at the same time, the sodium hydroxide solution (4 mol / L, flow rate 300 ml / min) was switched; when the particle size of the solid particles in the reaction solution reached 2.8 μm, a gas with an oxygen content concentration of 5% was introduced, and other conditions remained unchanged, obtaining the flaky nickel-manganese-aluminum hydroxide precursor. Subsequently, the solid particles were washed, dried, sieved and demagnetized to obtain the flaky nickel-manganese-aluminum hydroxide precursor.

[0026] Comparative Example 1

[0027] 7.5 L of water, 350 ml of sodium hydroxide solution and 200 mL of ammonia water were added to the reaction kettle as the bottom liquid. Then, an aqueous solution containing nickel sulfate and manganese sulfate (the mixing ratio of the mixed solution was Ni0.9Mn0.1, and the concentration of the mixed solution was 1.5 mol / L), ammonia water solution (30 mol / L) and sodium hydroxide (8 mol / L) aqueous solution were simultaneously introduced into the reaction kettle. The flow rate of the mixed solution was 500 mL / h, the flow rate of the sodium hydroxide solution was 400 mL / h, and the flow rate of the ammonia water solution was 100 mL / h. The system reacted under the conditions of 45 °C, a stirring rate of 1400 rpm, a pH of 11.5, and a nitrogen flow rate of 20 L / min. When the particle size of the solid particles in the reaction solution reached 1.5 μm, the sodium hydroxide solution (4 mol / L, flow rate 120 - 200 ml / min) was switched; when the particle size of the solid particles in the reaction solution reached 2.0 μm, the sodium hydroxide solution (4 mol / L, flow rate 120 - 200 ml / min) was switched, and at the same time, the ammonia water solution (30 mol / L, flow rate 200 ml / h) was switched, obtaining the strip-shaped nickel-manganese hydroxide precursor. Subsequently, the solid particles were washed, dried, sieved and demagnetized to obtain the strip-shaped nickel-manganese hydroxide precursor, as Figure 2 shown.

[0028] Description of the implementation conditions of the comparative example: The main difference between the comparative example and the example is that the comparative example used nitrogen throughout to maintain an anaerobic reaction atmosphere and did not control the oxidation state of the Mn element.

[0029] Preparation methods of nickel-cobalt-manganese cathode materials for Comparative Example 1 and Example 1

[0030] Mix the precursor and lithium salt and sinter them. For the first sintering process, the temperature is 300 - 400 °C, the heating rate is 3 - 5 °C / min, and the sintering time is 6 - 10 h; for the secondary sintering, the temperature is 700 - 800 °C, the heating rate is 2 - 3 °C, and the sintering time is 6 - 10 h; then perform the cycle rate test.

[0031] After the above - mentioned preparation method of the positive electrode material, the primary particles of Example 1 are slightly larger than those of the comparative example as a whole. After performing the long - cycle life test and the rate charge - discharge test, Example 1 shows better cycle performance and rate performance.

Claims

1. A precursor of a cathode material for a lithium-ion battery in a flake morphology, characterized in that, The chemical formula of the precursor is Ni x Mn y Al 1-x-y OH2, where 0.3 ≤ x ≤ 0.9, 0.1 ≤ y ≤ 0.7, and x + y ≤ 1.

2. The precursor of the cathode material for a lithium-ion battery in a flaky morphology according to claim 1, characterized in that, The length of each primary particle of the precursor is controlled between 250 nm and 800 nm, and the primary particles form secondary spheres in an interpenetrating and stacked manner. The particle size of the precursor is 2.5 - 8 μm.

3. The preparation method of a lithium-ion battery cathode material precursor with a flaky morphology according to claim 1 or 2, characterized in that, It includes the following steps: continuously introducing a mixed solution containing a soluble nickel salt, a soluble manganese salt or a soluble aluminum salt, a precipitant solution and a complexing agent solution into a reaction device for reaction; when the particle size of the solid particles in the reaction solution reaches 0.5 - 1.2 μm, start introducing a gas with an oxygen content concentration of 5% - 10%, and at the same time switch the flow rate of the concentration of the precipitant solution; when the particle size of the solid particles in the reaction solution reaches 2.0 - 3.0 μm, start introducing a gas with an oxygen content concentration of 1% - 5% to obtain the precursor.

4. The preparation method of a lithium-ion battery cathode material precursor with a flaky morphology according to claim 3, wherein During the reaction process, the pH of the reaction solution is 9.5 - 11.5; the reaction temperature is 45 - 60 °C.

5. The preparation method of a lithium-ion battery cathode material precursor with a flaky morphology according to claim 3, characterized in that, The total concentration of the mixed solution containing the soluble nickel salt, the soluble cobalt salt and the soluble manganese salt is 1.5 - 2.5 mol / L.

6. The preparation method of a lithium-ion battery cathode material precursor with a flaky morphology according to claim 3, characterized in that The precipitant is a sodium hydroxide solution, the complexing agent is an ammonia water solution, the concentration of the precipitant is 5 - 10 mol / L, and the concentration of the complexing agent is 20 - 30 mol / L.

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