Preparation method of lithium supplement additive for positive electrode of lithium ion battery and lithium ion battery

Abstract

The invention provides a preparation method of a lithium ion battery positive electrode lithium supplement additive and a lithium ion battery, and relates to the technical field of lithium ion batteries. The preparation method of the lithium supplement additive for the positive electrode of the lithium ion battery comprises the following steps: step 1, carrying out vapor deposition reaction on a mixture containing a gaseous carbon source and a metal catalyst in a reducing atmosphere to prepare powder; and 2, mixing the powder prepared in the step 1 with a lithium source, and carrying out heat treatment to obtain the lithium supplement additive for the positive electrode of the lithium ion battery. According to the preparation method provided by the invention, the reaction products of the metal catalyst and the lithium source, such as LNO and LFO, are synthesized in the carbon nanotube in situ, so that the lithium supplement additive for the positive electrode of the lithium ion battery, which can stably exist in the air and can complement the electronic conductivity, is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a preparation method of a lithium supplement additive for a lithium-ion battery cathode and a lithium-ion battery. Background Art

[0002] A lithium-ion battery is a secondary battery system using two different lithium intercalation compounds capable of reversibly deintercalating and intercalating lithium ions as the positive and negative electrodes. With its advantages such as high specific capacity, long cycle life, and low self-discharge, it is widely used in mobile phones, portable computers, cameras, camcorders, electric vehicles, energy storage, and other fields. Lithium iron phosphate is applied in pure electric buses, energy storage, and other fields due to its high safety performance, good cycle life, and environmental friendliness.

[0003] During the first charge of a lithium-ion battery, a solid electrolyte interphase membrane (SEI membrane) will form on the surface of the negative electrode, consuming active lithium and reducing the first efficiency of the lithium-ion battery. Moreover, the loss of active lithium is irreversible. To reduce the impact caused by the loss of active lithium, an additive is currently considered to be added to the positive electrode of the lithium-ion battery. This additive has a high lithium supplement capacity, and after releasing active lithium, it has high chemical stability and can reversibly deintercalate and intercalate active lithium as an active substance without affecting the overall cycle performance of the battery. Currently, the commonly used positive electrode lithium supplement agents are lithium-rich compounds, binary lithium compounds, etc. Lithium nickelate (LNO) and lithium ferrite (LFO), as lithium-rich compounds, have good application prospects as lithium supplement agents, but they are prone to react with carbon dioxide and water in the air to form lithium carbonate and lithium hydroxide, and are unstable. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a preparation method of a lithium supplement additive for a lithium-ion battery cathode and a lithium-ion battery, and to prepare a lithium supplement additive for a lithium-ion battery cathode that can stably exist in the air and can supplement the electronic conductivity.

[0005] The object of the present invention is mainly achieved through the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a lithium supplement additive for a lithium-ion battery cathode, including the following steps:

[0007] Step 1: Performing a chemical vapor deposition reaction on a mixture containing a gaseous carbon source and a metal catalyst in a reducing atmosphere to obtain a powder;

[0008] Step 2: Mixing the powder obtained in Step 1 with a lithium source and performing heat treatment to obtain the lithium supplement additive for the lithium-ion battery cathode.

[0009] Preferably, in Step 1, the carbon source includes at least one of methane, propane, and ethylene.

[0010] Preferably, in step 1, the reducing atmosphere is a hydrogen atmosphere.

[0011] Preferably, in step 1, the metal catalyst includes at least one of nickel and iron.

[0012] Preferably, in step 1, the mass ratio of the carbon source to the metal catalyst is (10 - 80):(20 - 90), preferably (40 - 70):(20 - 30).

[0013] Preferably, in step 1, the reaction temperature is 650 - 780 °C, preferably 720 - 750 °C.

[0014] Preferably, in step 2, the lithium source includes lithium carbonate.

[0015] Preferably, the mass ratio of the metal catalyst to the lithium source is (10 - 80):(20 - 90), preferably (10 - 20):(30 - 50).

[0016] Preferably, in step 2, the heat treatment temperature is 500 - 800 °C.

[0017] Preferably, in step 2, after mixing the powder obtained in step 1 with the lithium source, a sanding step is further included.

[0018] Preferably, the median particle size D50 of the sanded particles is 0.2 - 0.8 μm.

[0019] In a second aspect, the present invention provides a lithium-ion battery cathode lithium supplement additive prepared by the above preparation method.

[0020] In a third aspect, the present invention provides a lithium-ion battery, including a positive electrode plate, the positive electrode plate includes a positive electrode material layer and a current collector, the positive electrode material layer is disposed on the surface of the current collector, and the positive electrode material layer includes the lithium-ion battery cathode lithium supplement additive.

[0021] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0022] A) The preparation method provided by the present invention in-situ synthesizes reaction products of a metal catalyst and a lithium source, such as LNO and LFO, in carbon nanotubes to obtain a lithium-ion battery cathode lithium supplement additive that can stably exist in air and can supplement the electronic conductivity.

[0023] B) The lithium-ion battery provided by the present invention, by adding this lithium supplement additive to the positive electrode side of lithium iron phosphate, enables the lithium-ion battery to have a higher initial efficiency, enables the lithium iron phosphate electrode sheet to have a lower sheet resistance, and the lithium-ion battery to have more excellent electrical performance. Description of the Drawings

[0024] Figure 1 Curves of normal temperature cycle capacity retention rate for Examples 1-2 and Comparative Example 1 provided by the present invention. Detailed implementation manners

[0025] The preferred embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings. The accompanying drawings form a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention.

[0026] In order to improve the stability of LNO and LFO in air, the present invention provides a preparation method of a lithium supplement additive for the positive electrode of a lithium-ion battery with high specific capacity stability. This preparation method combines the high-temperature solid-phase method and the chemical vapor deposition method to coat LNO and LFO on carbon nanotubes, so as to isolate LNO and LFO from direct contact with air, thereby obtaining a lithium supplement additive for the positive electrode of a lithium-ion battery that can stably exist in air and can supplement the electronic conductivity. Another object of the present invention is to provide a lithium-ion secondary battery, which has a high initial efficiency and more excellent electrical performance.

[0027] Hereinafter, the present invention will be specifically described.

[0028] In a first aspect, the present invention provides a preparation method of a lithium supplement additive for the positive electrode of a lithium-ion battery, including the following steps:

[0029] Step 1: Perform a chemical vapor deposition reaction on a mixture containing a gaseous carbon source and a metal catalyst in a reducing atmosphere to obtain a carbon nanotube powder with a metal catalyst coated inside the carbon nanotubes;

[0030] Step 2: Mix the carbon nanotube powder obtained in Step 1 with a lithium source and perform heat treatment to obtain the lithium supplement additive for the positive electrode of the lithium-ion battery.

[0031] In the preparation method provided by the present invention, in Step 1, the chemical vapor deposition method is used to deposit carbon on the surface of the metal catalyst to form carbon nanotubes, and a carbon nanotube powder with a metal catalyst coated inside is obtained; then in Step 2, the high-temperature solid-phase method is used to react the lithium source with the metal catalyst inside the carbon nanotubes, so that the reaction product of the lithium source and the metal catalyst continues to coat the carbon nanotubes.

[0032] In the preparation method provided by the present invention, the chemical vapor deposition method and the high-temperature solid-phase method are combined to coat the reaction product of the metal catalyst and the lithium source on the carbon nanotubes, so as to isolate the reaction product from direct contact with air. There may be one or more reaction product particles inside a carbon tube, thereby obtaining a lithium supplement additive for the positive electrode of a lithium-ion battery that can stably exist in air and can supplement the electronic conductivity.

[0033] In a specific embodiment of the present invention, in step 1, the gaseous carbon source is one or more of methane, propane, and ethylene.

[0034] In a specific embodiment of the present invention, in step 1, the reducing atmosphere is a hydrogen atmosphere.

[0035] In a specific embodiment of the present invention, in step 1, the metal catalyst is at least one of nickel and iron.

[0036] In a specific embodiment of the present invention, in step 1, the mass ratio of the carbon source to the metal catalyst is (10 - 80):(20 - 90). For example, the values within the range of 10 - 80 can be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, etc., and the values within the range of 20 - 90 can be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, etc. Preferably, it is (40 - 70):(20 - 30).

[0037] In a specific embodiment of the present invention, in step 1, the reaction temperature is 650 - 780 °C, such as 650, 660, 670, 680, 690, 710, 750, 730, 740, 750, 760, 770, 780 °C, etc. Preferably, it is 720 - 750 °C, and the reaction time is 0.5 - 1 h.

[0038] In a specific embodiment of the present invention, in step 2, the lithium source is lithium carbonate.

[0039] In a specific embodiment of the present invention, the mass ratio of the metal catalyst to the lithium source is (10 - 80):(20 - 90). For example, the values within the range of 10 - 80 can be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, etc., and the values within the range of 20 - 90 can be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, etc. Preferably, it is (10 - 20):(30 - 50).

[0040] In a specific embodiment of the present invention, in step 2, the heat treatment temperature is 500 - 800 °C, the heating rate is 1 - 5 °C / min, and the treatment time is 10 - 15 h.

[0041] In a specific embodiment of the present invention, in step 2, the heat treatment is carried out under the protection of an inert atmosphere, and the inert atmosphere is one or a mixture of nitrogen and argon.

[0042] In a specific embodiment of the present invention, in step 2, after the carbon nanotube powder is mixed with the lithium source, the steps of sand milling and drying are further included in sequence, and heat treatment is carried out after drying.

[0043] In a specific embodiment of the present invention, in step 2, the median particle size D50 of the particles after sand milling is 0.2 - 0.8 μm, and D90 < 3 μm.

[0044] In a specific embodiment of the present invention, in step 2, after heat treatment, the steps of crushing, sieving, and removing magnetism are further included.

[0045] In a specific embodiment of the present invention, the specific steps of the preparation method of the lithium supplement additive for the positive electrode of the lithium ion battery are as follows:

[0046] Step 1: After introducing an inert gas into the fluidized bed, raise the temperature of the fluidized bed to 600 - 800 °C. After introducing a reducing gas (such as hydrogen) into the fluidized bed, add a carbon source and a metal catalyst into the fluidized bed. Among them, the carbon source is one or more of methane and propane, the metal catalyst is one of nickel or iron, and the mass percentage of the carbon source to the active metal is 10 - 80:90 - 20. During the reaction, control the temperature of the fluidized bed to remain at 650 - 780 °C, and collect the carbon nanotube powder at the outlet of the reaction furnace.

[0047] Step 2: Mix the carbon nanotube powder obtained in step 1 with lithium carbonate according to the ratio of the metal catalyst in step (1), then disperse and mix evenly through a sand mill classifier. The slurry is spray-dried in a spray drying device. The inlet temperature of the spray drying device is controlled at 190 - 280 °C, and the outlet temperature is controlled at 90 - 110 °C; the mixed powder obtained after spray drying is subjected to high-temperature heat treatment under the protection of an inert atmosphere. Among them, the mass percentage of the metal catalyst to lithium carbonate is 10 - 80:90 - 20. After the reaction, it is crushed, sieved, and magnetism is removed to obtain LNO or LFO coated on the carbon nanotubes.

[0048] In the second aspect, the present invention provides a lithium supplement additive for the positive electrode of a lithium ion battery, which is prepared by the above preparation method.

[0049] The preparation method provided by the present invention can prepare a lithium supplement additive for the positive electrode of a lithium ion battery that can stably exist in air and can supplement the electronic conductivity, increasing the initial efficiency of the lithium ion battery by 4% - 7%.

[0050] In the third aspect, the present invention provides a lithium ion battery, including a positive electrode plate, and the positive electrode plate includes a positive electrode material layer and a current collector. The positive electrode material layer includes the above-mentioned lithium supplement additive for the positive electrode of a lithium ion battery, lithium iron phosphate, and polyvinylidene fluoride.

[0051] Currently, in the prior art, the electronic conductivity of lithium iron phosphate materials is low, and the electronic conductivity at room temperature is about 10-9 ~10 -10 S / cm. Currently, the electronic conductivity of lithium iron phosphate materials is mainly enhanced by carbon coating. On the other hand, adding a certain amount of carbon nanotubes to the preparation of the positive electrode sheet can also supplement the electronic conductivity on the positive electrode side.

[0052] The lithium-ion battery provided by the present invention includes the above-mentioned lithium supplement additive for the positive electrode of the lithium-ion battery. This lithium supplement additive can also act as a conductive agent, eliminating the need to additionally add a conductive agent and the need to additionally coat carbon on the surface of the lithium iron phosphate positive electrode material, and can also supplement the conductivity.

[0053] The following specifically describes the preferred embodiments of the present invention to illustrate the principle of the present invention, which is not used to limit the scope of the present invention.

[0054] Unless otherwise specified, all reagents used in the present invention are commercially available products.

[0055] Example 1

[0056] (1) A preparation method of a lithium supplement additive for the positive electrode of a lithium-ion battery that can stably exist in air and can supplement the electronic conductivity, including the following steps:

[0057] Step 1: After introducing the inert gas nitrogen into the fluidized bed, the temperature is raised to 750 °C at a heating rate of 3 °C / min, and then the reducing gas hydrogen is introduced. Weigh 12 g of metal nickel powder and divide it equally into 6 parts. Introduce methane gas into the fluidized bed and add the metal nickel powder in 6 portions. Collect the carbon nanotube powder with a dust removal bag at the outlet of the fluidized bed. Among them, the mass ratio of methane to the metal nickel powder is 4:2.

[0058] Step 2: Weigh 10 g of the carbon nanotube powder obtained in Step 1 and 12.54 g of lithium carbonate powder (the mass ratio of the metal catalyst to lithium carbonate is 1:3.77). The two are sand-milled and mixed evenly. The sand-milling particle size is controlled at D50 of 0.4 - 0.45 microns. The slurry is dried in a spray drying tower. The inlet temperature of the spray drying equipment is controlled at 200 - 240 °C, and the outlet temperature is controlled at 90 - 110 °C to obtain the dried mixed powder. Under nitrogen protection, the precursor powder obtained after spray drying is heated to 750 °C at a heating rate of 3 °C / min and heat-treated for 10 h. The reaction product is pulverized and sieved to obtain the lithium supplement additive for the positive electrode of the lithium-ion battery that can stably exist in air and can supplement the electronic conductivity, LNO / CNT.

[0059] (2) Preparation of lithium-ion battery: The LNO / CNT obtained in this example was mixed with lithium iron phosphate and PVDF (polyvinylidene fluoride) in a mass ratio of 1:97:2 to prepare a positive electrode slurry. The obtained positive electrode slurry was coated on an aluminum foil current collector, dried at 105 °C, and then roll-pressed to obtain a positive electrode sheet. The prepared positive electrode sheet was wound with a negative electrode sheet, a separator, and a core was obtained. The core was placed in a case, electrolyte was injected into the battery case, and then it was encapsulated, formed, and capacity-divided to obtain a secondary lithium-ion battery.

[0060] Example 2

[0061] (1) A preparation method of a lithium-ion battery positive electrode lithium supplement additive that can stably exist in air and can supplement electronic conductivity includes the following steps:

[0062] Step 1: After introducing an inert atmosphere of nitrogen into the fluidized bed, the temperature was raised to 750 °C at a heating rate of 3 °C / min, and a reducing gas of hydrogen was introduced. Weigh 12 g of metallic iron powder and divide it into 6 equal parts. Propane gas was introduced into the fluidized bed, and the metallic iron powder was added in 6 times. The carbon nanotube powder was collected by a dust removal bag at the outlet of the fluidized bed. The mass ratio of propane to metallic iron was 4:2.

[0063] Step 2: Weigh 10 g of the carbon nanotube powder obtained in Step 1 and 13.21 g of lithium carbonate powder (the mass ratio of the metal catalyst to lithium carbonate is 3.97). The two were sand-milled and mixed evenly. The sand-milling particle size was controlled at D50 of 0.4 - 0.45 microns. The slurry was dried in a spray drying tower. The inlet temperature of the spray drying equipment was controlled at 200 - 240 °C, and the outlet temperature was controlled at 90 - 110 °C to obtain a dried mixed powder. The precursor powder obtained after spray drying was heat-treated at 750 °C for 10 h at a heating rate of 3 °C / min under nitrogen protection. The reaction product was crushed, sieved, and demagnetized to obtain a lithium-ion battery positive electrode lithium supplement additive, LFO / CNT, that can stably exist in air and can supplement electronic conductivity.

[0064] (2) Preparation of lithium-ion battery: The LFO / CNT obtained in this example was mixed with lithium iron phosphate and PVDF (polyvinylidene fluoride) in a mass ratio of 1:97:2 to prepare a positive electrode slurry. The obtained positive electrode slurry was coated on an aluminum foil current collector, dried at 105 °C, and then roll-pressed to obtain a positive electrode sheet. The prepared positive electrode sheet was wound with a negative electrode sheet, a separator, and a core was obtained. The core was placed in a case, electrolyte was injected into the battery case, and then it was encapsulated, formed, and capacity-divided to obtain a secondary lithium-ion battery.

[0065] Example 3

[0066] This embodiment is basically the same as Embodiment 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, in Step 1, the mass ratio of methane to metallic nickel powder is 3.5:2.5, and in Step 2, 10 g of the carbon nanotube powder obtained in Step 1 and 15.71 g of lithium carbonate powder (the mass ratio of the metal catalyst to lithium carbonate is 1:3.77) are weighed.

[0067] Example 4

[0068] This embodiment is basically the same as Embodiment 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, in Step 1, the mass ratio of methane to metallic nickel powder is 7:3, and in Step 2, 10 g of the carbon nanotube powder obtained in Step 1 and 11.31 g of lithium carbonate powder (the mass ratio of the metal catalyst to lithium carbonate is 1:3.77) are weighed.

[0069] Example 5

[0070] This embodiment is basically the same as Embodiment 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, in Step 1, the fluidized bed temperature is 740 °C.

[0071] Example 6

[0072] This embodiment is basically the same as Embodiment 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, in Step 2, the mass of the lithium carbonate powder is 14.06 g (the mass ratio of the metal catalyst to lithium carbonate is 1:4.22).

[0073] Comparative Example 1

[0074] A preparation method of a lithium iron phosphate material lithium-ion battery includes the following steps:

[0075] Preparation of the lithium-ion battery: Lithium iron phosphate, PVDF, and a conductive agent (carbon black) are mixed uniformly in a mass ratio of 97:2:1 to prepare a positive electrode paste. The obtained positive electrode paste is coated on an aluminum foil current collector, dried at 105 °C, and then roll-pressed to obtain a positive electrode sheet. The prepared positive electrode sheet, negative electrode sheet, separator, and winding are used to obtain an electric core. The electric core is placed in a shell, electrolyte is injected into the battery shell, packaged, formed, and sorted to obtain a lithium-ion secondary battery.

[0076] Comparative Example 2

[0077] This comparative example is basically the same as Embodiment 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, lithium nickelate is prepared first in Step 1, and then carbon nanotubes are coated on the outside in Step 2:

[0078] Step 1: Weigh 3.33 g of metallic nickel powder and 12.54 g of lithium carbonate powder (the mass ratio of the metal catalyst to lithium carbonate is 1:3.77). Grind and mix the two evenly. Control the grinding particle size so that D50 is 0.4 - 0.45 microns. Dry the slurry in a spray drying tower. Control the inlet temperature of the spray drying equipment at 200 - 240 °C and the outlet temperature at 90 - 110 °C to obtain the dried mixed powder. Under nitrogen protection, heat the precursor powder obtained after spray drying to 750 °C at a heating rate of 3 °C / min for 10 h. Crush and screen the reaction product;

[0079] Step 2: After introducing the inert gas nitrogen into the fluidized bed, heat it to 750 °C at a heating rate of 3 °C / min, and then introduce the reducing gas hydrogen. Add the lithium nickelate powder prepared in Step 1, and introduce methane gas into the fluidized bed. The mass ratio of methane to the metallic nickel powder is 4:2.

[0080] Comparative Example 3

[0081] This comparative example is basically the same as Example 1, except that in the preparation method of the lithium supplement additive for the positive electrode of the lithium-ion battery, carbon nanotubes are not used to coat the lithium nickelate:

[0082] Step 1: Weigh 3.33 g of metallic nickel powder and 12.54 g of lithium carbonate powder. Grind and mix the two evenly. Control the grinding particle size so that D50 is 0.4 - 0.45 microns. Dry the slurry in a spray drying tower. Control the inlet temperature of the spray drying equipment at 200 - 240 °C and the outlet temperature at 90 - 110 °C to obtain the dried mixed powder. Under nitrogen protection, heat the precursor powder obtained after spray drying to 750 °C at a heating rate of 3 °C / min for 10 h. Crush and screen the reaction product.

[0083] Step 2: Mix the lithium nickelate prepared in Step 1 with conventional carbon nanotubes (the length of the carbon nanotubes is 0.4 - 0.45 microns) to prepare the lithium supplement additive. The mass ratio of the carbon nanotubes to the metallic nickel powder is 4:2.

[0084] Test Example

[0085] (1) Resistivity test method - powder resistivity tester;

[0086] (2) Test method for the discharge specific capacity at 0.1C of the coin cell - making slurry, coating, punching, assembling, charge and discharge testing (0.1C CC - CV to 3.65V, 0.1C DC to 2.5V);

[0087] (3) Test method for the cycle test - soft - package battery cell cycles at 25 °C with 1C / 1C at 2.5V / 3.65V.

[0088] Table 1 Performance Tests of Examples and Comparative Examples

[0089]

[0090] As can be seen from Table 1, compared with Comparative Examples 1-3, the lithium supplement additives prepared in Examples 1-6 provided by the present invention have lower resistivity, meet the use requirements (lower than 38 Ω·cm), and have high specific capacity and cycle retention rate, with excellent performance.

[0091] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A preparation method of a lithium supplement additive for a lithium-ion battery cathode, characterized in that, It includes the following steps: Step 1: Carry out a chemical vapor deposition reaction on a mixture containing a gaseous carbon source and a metal catalyst in a reducing atmosphere to obtain a powder. Step 2: Mix the powder obtained in Step 1 with a lithium source and perform heat treatment to obtain the lithium supplement additive for the positive electrode of the lithium-ion battery.

2. The preparation method according to claim 1, characterized in that, In Step 1, the carbon source includes at least one of methane, propane, and ethylene. And / or, the reducing atmosphere is a hydrogen atmosphere.

3. The preparation method according to claim 1 or 2, characterized in that, In Step 1, the metal catalyst includes at least one of nickel and iron.

4. The preparation method according to claim 1 or 2, characterized in that In Step 1, the mass ratio of the carbon source to the metal catalyst is (10 - 80):(20 - 90), preferably (40 - 70):(20 - 30).

5. The preparation method according to claim 1 or 2, characterized in that In Step 1, the reaction temperature is 650 - 780 °C, preferably 720 - 750 °C.

6. The preparation method according to claim 1 or 2, characterized in that In Step 2, the lithium source includes lithium carbonate. And / or, the mass ratio of the metal catalyst to the lithium source is (10 - 80):(20 - 90), preferably (10 - 20):(30 - 50).

7. The preparation method according to claim 1 or 2, characterized in that, In Step 2, the heat treatment temperature is 500 - 800 °C.

8. The preparation method according to claim 1 or 2, characterized in that, In Step 2, after mixing the powder obtained in Step 1 with the lithium source, it further includes a sanding step. Preferably, the median particle size D50 of the particles after sanding is 0.2 - 0.8 μm.

9. A lithium supplement additive for the positive electrode of a lithium-ion battery prepared by the preparation method according to any one of claims 1 - 8.

10. A lithium-ion battery, characterized in that, It includes a positive electrode tab, the positive electrode tab includes a positive electrode material layer and a current collector, the positive electrode material layer is provided on the surface of the current collector, and the positive electrode material layer includes the lithium supplement additive for the positive electrode of the lithium-ion battery according to claim 9.

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