Lithium nickelate material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium nickelate material and a preparation method and application thereof. The preparation method of the lithium nickelate material comprises the following steps: weighing a lithium source and a nickel source according to the stoichiometric ratio of lithium nickelate, and uniformly mixing to obtain a mixture; and sintering the mixture for at least one time, and cooling, wherein at least one time of sintering treatment is carried out in an air atmosphere with the relative pressure larger than or equal to 1 MPa. According to the method, high-temperature sintering is carried out by taking air as a reaction atmosphere and increasing the air pressure in the synthesis process, so that the effect of inhibiting decomposition of LiNiO2 is remarkably improved, the content of LiNiO2 in the material is increased, impure phases are reduced, the electrochemical performance of the lithium nickelate material is remarkably improved, sintering or adding of excessive lithium sources in a pure oxygen atmosphere is not needed, and the cost is reduced. And the problems of high preparation cost caused by pure oxygen sintering and high residual alkali content on the surface of the material caused by excessive addition of the lithium source are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium nickelate material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have been widely used in all aspects of our lives due to their high energy and long life performance advantages. Lithium-ion batteries can be divided into three categories according to usage scenarios and energy size: lithium power batteries, lithium consumer batteries and lithium energy storage batteries.

[0003] At present, lithium-powered batteries mainly use lithium iron phosphate and nickel-cobalt-manganese ternary materials as positive electrode materials. Among them, nickel-cobalt-manganese (NCM) ternary materials can be used for more lithium ions to be deintercalated and have the advantages of high energy density and good cycle performance. The large-scale mass-produced NCM ternary material is developed from lithium nickel oxide, that is, Co and Mn elements are added to lithium nickel oxide to prepare a ternary material with relatively stable chemical properties. The reason why the precious metal Co is chosen to replace part of the Ni in lithium nickel oxide is that during the synthesis of lithium nickel oxide, Ni 3+ Thermodynamically very unstable, easily reduced to Ni 2+ , and then decomposes to produce: Li2O (remains on the surface to form residual alkali), NiO (impurity phase) and O2 (waste of resources), which makes it difficult to synthesize LiNiO2 with a stoichiometric ratio.

[0004] At present, in order to overcome the problem that it is difficult to synthesize stoichiometric LiNiO2 in the above-mentioned lithium nickelate synthesis process, technical personnel in this field generally adopt the following two methods to inhibit the decomposition of LiNiO2: 1) sintering in a pure oxygen atmosphere to inhibit the decomposition of LiNiO2, but pure oxygen needs to be continuously introduced for sintering, which requires a large amount of oxygen, consumes a lot of resources, and has a high synthesis cost; 2) adding excess LiOH as a reactant, in the hope of synthesizing stoichiometric LiNiO2 by sintering with excess LiOH to generate Li2O to inhibit the decomposition reaction of LiNiO2, but this will cause Li2O to remain on the surface of the material to form residual alkali, which will lead to poor electrochemical performance of the material and affect the subsequent use of the material at the battery cell end. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing method for synthesizing stoichiometric LiNiO2, such as high cost and high residual alkali on the surface of the material, thereby providing a lithium nickelate material and its preparation method and application to solve the above problems.

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

[0007] A preparation method of a lithium nickelate material comprises: weighing a lithium source and a nickel source according to the stoichiometric ratio of lithium nickelate and mixing them to obtain a mixture; sintering the mixture at least once and cooling it to obtain the mixture; wherein the at least one sintering treatment is carried out in an air atmosphere with a relative pressure of ≥1MPa.

[0008] Preferably, the lithium source is lithium hydroxide and / or lithium carbonate.

[0009] Preferably, the nickel source is nickel hydroxide and / or nickel oxyhydroxide.

[0010] Preferably, the sintering temperature is 600-700°C;

[0011] And / or, the sintering treatment duration is 5-10 hours.

[0012] Preferably, the sintering process is a double sintering process.

[0013] Preferably, the relative pressure is 1-10 MPa.

[0014] Preferably, the cooling treatment is a gas quenching treatment.

[0015] Preferably, the process of the gas quenching treatment is: replacing the high-temperature air in the furnace with air at room temperature, so that the temperature in the furnace drops to room temperature within 0.1-1h.

[0016] The present invention also provides a lithium nickelate material, which is prepared by the above-mentioned method for preparing the lithium nickelate material.

[0017] The present invention also provides application of the above-mentioned lithium nickel oxide material in lithium ion batteries.

[0018] In the present invention, the relative pressure is the pressure of the pressure gauge, that is, the actual internal pressure-the atmospheric pressure=the relative pressure.

[0019] The technical solution of the present invention has the following advantages:

[0020] 1. A method for preparing a lithium nickelate material, comprising: weighing a lithium source and a nickel source according to the stoichiometric ratio of lithium nickelate and mixing them to obtain a mixture; sintering the mixture at least once and cooling it; wherein at least one sintering process is performed in an air atmosphere with a relative pressure of ≥1MPa. In order to solve the problems of high cost and high residual alkali on the surface of the material in the existing method for synthesizing stoichiometric ratio LiNiO2, the present invention uses air as the reaction atmosphere and increases the air pressure during the synthesis process for high-temperature sintering, thereby achieving a significant improvement in the effect of inhibiting the decomposition of LiNiO2, increasing the content of LiNiO2 in the material, reducing impurities, and significantly improving the electrochemical performance of the lithium nickelate material. In addition, there is no need to sinter in a pure oxygen atmosphere or add an excessive amount of lithium source, thereby avoiding the high preparation cost caused by pure oxygen sintering and the problem of high residual alkali on the surface of the material caused by excessive lithium source addition.

[0021] 2. In the preparation method of the lithium nickelate material of the present invention, the prior art adopts the method of natural cooling with the furnace to reduce the sintered material to room temperature after the lithium nickelate material is sintered. However, the present invention finds that LiNiO2 has a problem of gradually decomposing as the cooling time is prolonged due to the removal of the driving force of the high temperature reaction during the long-term natural cooling process after high-temperature sintering. In addition, the LiNiO2 material is a secondary particle sphere formed by the agglomeration of primary particles. The material has strong brittleness and low hardness, and is easy to pulverize. After pulverization, the contact area between the LiNiO2 material and the electrolyte will be increased, resulting in poor cycle performance. Based on this, the present invention is to introduce room temperature air immediately after the sintering process is completed to replace the high-temperature air in the sintering furnace, thereby shortening the cooling time, achieving the purpose of rapid cooling of the material, inhibiting the decomposition of LiNiO2, and greatly improving the hardness of the material, eliminating the orientation stress between the primary particles, and reducing the brittleness of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 is a scanning electron microscope image of the lithium nickel oxide material prepared in Example 1 of the present invention;

[0024] Figure 2 Graph showing the compressive performance of lithium nickel oxide materials prepared in the embodiments of the present invention and the comparative examples;

[0025] Figure 3 It is a cycle performance diagram of the lithium nickel oxide material prepared in the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0026] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0027] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0028] Example 1

[0029] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0030] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0031] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing high-pressure air, adjusting the relative pressure to 5 MPa (pressure expressed with atmospheric pressure as the reference, pressure indicated by the pressure gauge, and all the following pressures are pressure gauge pressures), sintering at 600° C. for 10 h, then stopping heating, releasing the pressure, replacing the high-temperature air in the furnace with air at normal temperature, and lowering the temperature in the furnace from 600° C. to room temperature in 0.5 h to obtain a sintered product;

[0032] 3) The sintered product of step 2) is further heated in a high pressure gas quenching furnace and the relative pressure is adjusted to 5 MPa. After sintering at 600°C for 5 hours, the heating is stopped, the pressure is released, and the high temperature air in the furnace is replaced by normal temperature air. The temperature in the furnace is lowered from 600°C to room temperature in 0.5 hours. The product is taken out and crushed to obtain LiNiO2 material, whose microstructure is as follows: Figure 1 shown.

[0033] Example 2

[0034] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0035] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0036] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing high-pressure air, adjusting the relative pressure to 1 MPa, sintering at 700° C. for 5 h, then stopping heating, releasing the pressure and replacing the high-temperature air in the furnace with air at room temperature, and lowering the temperature in the furnace from 700° C. to room temperature within 1 h to obtain a sintered product;

[0037] 3) The sintered product of step 2) is continuously heated in a high-pressure gas quenching furnace and the relative pressure is adjusted to 1 MPa. After sintering at 700°C for 5 hours, the heating is stopped, the pressure is released, and the high-temperature air in the furnace is replaced with normal-temperature air. The temperature in the furnace is lowered from 700°C to room temperature within 1 hour. The product is taken out and crushed to obtain LiNiO2 material.

[0038] Example 3

[0039] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0040] 1) 5 mol Li2CO3 and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0041] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing high-pressure air, adjusting the relative pressure to 10 MPa, sintering at 600° C. for 10 h, stopping heating, releasing the pressure and replacing the high-temperature air in the furnace with air at room temperature, and reducing the temperature in the furnace from 600° C. to room temperature in 0.1 h to obtain a sintered product;

[0042] 3) The sintered product of step 2) is continuously heated in a high-pressure gas quenching furnace and the relative pressure is adjusted to 10 MPa. After sintering at 600°C for 10 h, the heating is stopped, the pressure is released, and the high-temperature air in the furnace is replaced with normal-temperature air. The temperature in the furnace is lowered from 600°C to room temperature in 0.1 h. The product is taken out and crushed to obtain LiNiO2 material.

[0043] Example 4

[0044] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0045] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0046] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing high-pressure air, adjusting the relative pressure to 5 MPa (pressure expressed with atmospheric pressure as the reference, pressure indicated by the pressure gauge, and all the following pressures are pressure gauge pressures), sintering at 600° C. for 10 h, then stopping heating, and then naturally cooling to room temperature to obtain a sintered product;

[0047] 3) The sintered product of step 2) is continuously heated in a high-pressure gas quenching furnace and the relative pressure is adjusted to 5 MPa. After sintering at 600° C. for 5 h, the heating is stopped, and the product is then naturally cooled to room temperature. The product is taken out and crushed to obtain LiNiO2 material.

[0048] Example 5

[0049] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0050] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0051] 2) The mixture of step 1) is placed in a high-pressure gas quenching furnace and introduced with high-pressure air, the relative pressure is adjusted to 5 MPa, and the heating is stopped after sintering at 600° C. for 10 hours, followed by natural cooling to room temperature, and the mixture is taken out and crushed to obtain LiNiO2 material.

[0052] Example 6

[0053] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0054] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0055] 2) The mixed material of step 1) is placed in a high-pressure gas quenching furnace and introduced with high-pressure air, and the relative pressure is adjusted to 5 MPa. After sintering at 600°C for 10 hours, the heating is stopped, the pressure is released, and the high-temperature air in the furnace is replaced with normal temperature air. The temperature in the furnace is lowered from 600°C to room temperature in 0.5 hours, and the LiNiO2 material is taken out and crushed to obtain the LiNiO2 material.

[0056] Example 7

[0057] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0058] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0059] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing high-pressure air, adjusting the relative pressure to 5 MPa, sintering at 600° C. for 10 h, stopping heating, releasing the pressure and replacing the high-temperature air in the furnace with air at room temperature, and reducing the temperature in the furnace from 600° C. to room temperature in 0.5 h to obtain a sintered product;

[0060] 3) The sintered product of step 2) is continuously heated in a high-pressure gas quenching furnace and the relative pressure is adjusted to 5 Pa. After sintering at 600°C for 5 hours, heating is stopped, and the high-temperature air in the furnace is replaced by normal temperature air. The temperature in the furnace is lowered from 600°C to room temperature in 0.5 hours. The LiNiO2 material is taken out and crushed to obtain the LiNiO2 material.

[0061] Example 8

[0062] This embodiment provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0063] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0064] 2) placing the mixed material of step 1) into a high-pressure gas quenching furnace and introducing air, adjusting the relative pressure to 5 Pa, sintering at 600° C. for 10 h, stopping heating, releasing the pressure and replacing the high-temperature air in the furnace with air at room temperature, and lowering the temperature in the furnace from 600° C. to room temperature in 0.5 h to obtain a sintered product;

[0065] 3) The sintered product of step 2) is continuously heated in a high-pressure gas quenching furnace and the relative pressure is adjusted to 5 MPa. After sintering at 600°C for 5 hours, the heating is stopped, the pressure is released, and the high-temperature air in the furnace is replaced with normal temperature air. The temperature in the furnace is lowered from 600°C to room temperature in 0.5 hours. The product is taken out and crushed to obtain LiNiO2 material.

[0066] Comparative Example 1

[0067] This comparative example provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0068] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0069] 2) putting the mixed material of step 1) into a roller kiln commonly used for sintering (it can only be sintered under normal atmospheric pressure. If the relative pressure is to be increased, the amount of gas must be increased. After the amount of gas is increased, the temperature cannot be kept constant at 600° C. and its structure cannot support a relative pressure of 1 MPa) and introducing air to adjust the relative pressure to 5 Pa (similarly, the pressure on the pressure gauge). After sintering at 600° C. for 10 hours, stop heating, and then naturally cool to room temperature to obtain a sintered product;

[0070] 3) The sintered product of step 2) is continuously heated in a sintering furnace and the relative pressure is adjusted to 5 Pa. After sintering at 600° C. for 5 h, the heating is stopped, and the product is then naturally cooled to room temperature. The product is taken out and crushed to obtain LiNiO2 material.

[0071] Comparative Example 2

[0072] This comparative example provides a lithium nickel oxide material and a preparation method thereof, and the specific steps are as follows:

[0073] 1) 10 mol LiOH and 10.0 mol Ni(OH)2 were uniformly mixed in a high-speed mixer to obtain a mixture;

[0074] 2) The mixed material of step 1) is placed into a roller kiln commonly used for sintering (it can only be sintered under normal atmospheric pressure. If the relative pressure needs to be increased, the amount of gas must be increased. After the amount of gas is increased, the temperature cannot be maintained at a constant temperature of 600°C. Moreover, its structure cannot support a relative pressure of 1Mpa) and air is introduced. The relative pressure is adjusted to 5Pa (similarly, the pressure on the pressure gauge). After sintering at 600°C for 10 hours, heating is stopped, and then naturally cooled to room temperature to obtain LiNiO2 material.

[0075] Test Example 1

[0076] The compressive and electrochemical properties of the LiNiO2 materials prepared in the examples and comparative examples were tested.

[0077] The compression test method steps are as follows: weigh 5.00g of the sample with weighing paper, put the sample into the sample holder, and then use a compactor to perform gradient pressure (5\7\9\11\13\15\17KN) and obtain a compaction density-pressure test graph, where the turning point of the slope of the straight line indicates that the material is pulverized under this pressure, that is, the pressure at the turning point of the slope of the straight line is the compressive capacity of the material. The test results are shown in Tables 1 and Figure 2 shown.

[0078] Electrochemical performance test: lithium nickel oxide material, conductive carbon black and PVDF were weighed and mixed in a mass ratio of 90:5:5, and the positive electrode slurry was prepared after adding solvent NMP. The slurry was evenly coated on the aluminum foil and baked at 105°C for 1h. The baked electrode was cut and placed in a tablet press for compaction at 25Mpa. Small discs were cut out and assembled under a nitrogen atmosphere. The small discs were placed on the positive side of the button battery housing with the fluorine-coated side facing the positive electrode. 50μL of 1mol / L electrolyte (EC, EMC and DMC in a volume ratio of 1:1:1) was dripped in, a diaphragm was placed in and 50μL of electrolyte was dripped in, a pure lithium sheet, a gasket, and a spring were placed in the button battery negative electrode housing, and the battery was packaged into a CR2032 button battery for battery testing. Charge and discharge system: the charge cut-off voltage is 4.3V, the discharge cut-off voltage is 3.0V; the first cycle is 0.1C charge, 0.1C discharge; the second cycle is 0.5C charge, 0.5C discharge; the third cycle is 1.0C charge, 1.0C discharge; then 1C charge and 1C discharge are cycled 200 times to test the cycle retention rate. The test results are shown in Table 1 and Figure 3 shown.

[0079] Table 1

[0080]

[0081] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium nickel oxide material, characterized in that: include: The lithium source and the nickel source are weighed and mixed according to the stoichiometric ratio of lithium nickelate to obtain a mixture; the mixture is sintered at least once and cooled to obtain the mixture; wherein the at least one sintering treatment is carried out in an air atmosphere with a relative pressure ≥1MPa.

2. The preparation method according to claim 1, characterized in that: The lithium source is lithium hydroxide and / or lithium carbonate.

3. The preparation method according to claim 1 or 2, characterized in that: The nickel source is nickel hydroxide and / or nickel oxyhydroxide.

4. The preparation method according to any one of claims 1 to 3, characterized in that The sintering temperature is 600-700°C; And / or, the sintering treatment duration is 5-10 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The sintering process is a double sintering process.

6. The preparation method according to claim 5, characterized in that: The relative pressure is 1-10Mpa.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The cooling treatment is a gas quenching treatment.

8. The preparation method according to claim 7, characterized in that: The process of gas quenching treatment is: using normal temperature air to replace the high temperature air in the furnace, so that the temperature in the furnace drops to room temperature within 0.1-1h.

9. A lithium nickel oxide material, characterized in that: The lithium nickelate material is prepared by the preparation method of the lithium nickelate material according to any one of claims 1 to 8.

10. Use of the lithium nickel oxide material according to claim 9 in lithium ion batteries.

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