WO2024021277A1 - Ternary positive electrode material and preparation method therefor, positive electrode sheet and battery - Google Patents

Abstract

A ternary positive electrode material and a preparation method therefor, a positive electrode sheet and a battery. The ternary positive electrode material comprises a lithium nickel cobalt manganate base material, a ferric phosphate coating layer and a boron coating layer; the outer circumferential side of the lithium nickel cobalt manganate base material is coated with the ferric phosphate coating layer; the outer circumferential side of the ferric phosphate coating layer is coated with the boron coating layer; and the boron coating layer penetrates through the pores of the ferric phosphate coating layer and then is bonded to the outer surface of the lithium nickel cobalt manganate base material. On one hand, the ferric phosphate coating layer can reduce direct contact between the lithium nickel cobalt manganate base material and an electrolyte, and improve the cycle performance of the lithium nickel cobalt manganate base material; the boron coating layer can be filled in the pores of the ferric phosphate coating layer, thereby further preventing the electrolyte from being in contact with the lithium nickel cobalt manganate base material, and improving the cycle performance of the lithium nickel cobalt manganate base material. Furthermore, the bonding of the boron coating layer and the lithium nickel cobalt manganate base material can improve the bonding strength of the ferric phosphate coating layer and the lithium nickel cobalt manganate base material, and moreover, boron has excellent conductivity, a conductive network can be formed after the pores are filled, and the stability of the ferric phosphate coating layer is fully improved.

Description

A ternary positive electrode material and its preparation method, positive electrode sheet and battery Technical field

The present invention relates to the field of battery technology, and specifically to a ternary positive electrode material and a preparation method thereof, a positive electrode sheet and a battery.

Background technique

Ternary cathode materials, especially high-nickel cathode materials, have poor cycle performance. Their surfaces are generally protected by surface coating to avoid direct contact between the electrolyte and cathode materials to improve cycle performance. However, some existing coatings, such as those prepared by co-precipitation method, have poor bonding properties and are prone to falling off during circulation. Therefore, there is currently a lack of a ternary cathode material that can ensure both cycle performance and the bonding strength of the coating layer.

In view of this, the present invention is proposed.

Contents of the invention

The purpose of the present invention is to provide a ternary cathode material that can ensure both cycle performance and coating layer bonding strength and a preparation method thereof.

The present invention also aims to provide a positive electrode sheet and battery, which include the above-mentioned ternary positive electrode material. Therefore, it has the advantage of excellent cycle performance.

The embodiment of the present invention is implemented as follows:

In a first aspect, the present invention provides a ternary cathode material, including:

Lithium nickel cobalt manganate substrate;

The iron phosphate coating layer is coated on the outer peripheral side of the lithium nickel cobalt manganate base material;

The boron coating layer is coated on the outer peripheral side of the iron phosphate coating layer, and part of the boron coating layer penetrates through the pores of the iron phosphate coating layer to bond with the outer surface of the lithium nickel cobalt manganate base material.

In an optional embodiment, the mass of the iron phosphate coating layer accounts for 0.5-5% of the total mass of the ternary cathode material.

In an optional embodiment, the mass of the boron coating layer accounts for 0.5-5% of the total mass of the ternary cathode material.

In a second aspect, the present invention provides a method for preparing the ternary cathode material of any one of the aforementioned embodiments, including:

Mix the suspension containing the lithium nickel cobalt manganate base material and the iron phosphorus solution, dry it and perform the first sintering to form an iron phosphate coating layer on the outer peripheral side of the lithium nickel cobalt manganate base material;

Mix the boron source and the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer, and perform secondary sintering to form a boron coating layer on the outer peripheral side of the iron phosphate coating layer, and make the boron Part of the coating layer penetrates through the pores of the iron phosphate coating layer to bond with the outer surface of the lithium nickel cobalt manganate substrate.

In an optional embodiment, the suspension is obtained by dispersing a lithium nickel cobalt manganate base material in a first solvent, and the first solvent includes an organic solvent or water;

The iron phosphorus solution is obtained by co-dispersing the iron source and the phosphorus source in a second solvent, and the second solvent includes water.

In an optional embodiment, the iron source includes a water-soluble iron salt; and/or the phosphorus source includes at least one of phosphoric acid and a water-soluble phosphorus salt; and/or the boron source includes boron oxide , at least one of boric acid and borate.

In an optional embodiment, in the iron phosphorus solution, the concentration of iron ions is 0.05-2.5 mol/L, and the concentration of phosphate is 0.05-2.5 mol/L.

In an optional embodiment, the drying temperature is 100-250°C, the drying time is 4-6h; and/or the sintering temperature of the first sintering is 400-800°C, the sintering time is 6-12h, the sintering environment It is a pure oxygen environment; and/or, the sintering temperature for the second sintering is 700-800°C, the sintering time is 4-8 hours, and the sintering environment is a pure oxygen environment.

In a third aspect, the present invention provides a positive electrode sheet, including:

positive current collector;

The cathode active material layer is obtained by coating at least one side of the cathode current collector with a cathode active slurry; the cathode active slurry includes the ternary cathode material of any one of the preceding embodiments.

In a fourth aspect, the present invention provides a battery including the positive electrode sheet of the aforementioned embodiment.

Embodiments of the present invention have at least the following advantages or beneficial effects:

Embodiments of the present invention provide a ternary cathode material, which includes a lithium nickel cobalt manganate base material, an iron phosphate coating layer and a boron coating layer; the iron phosphate coating layer is coated on the lithium nickel cobalt manganate base material The boron coating layer covers the outer peripheral side of the iron phosphate coating layer, and part of the boron coating layer penetrates through the pores of the iron phosphate coating layer to bond with the outer surface of the lithium nickel cobalt manganate base material.

On the one hand, through the setting of the iron phosphate coating layer, the direct contact between the substrate and the electrolyte can be reduced, and the cycle performance of the substrate can be improved; at the same time, through the setting of the boron coating layer, the pores of the iron phosphate coating layer can be filled, This can further prevent the electrolyte from contacting the substrate and further improve the cycle performance of the substrate; on the other hand, the boron coating penetrates through the pores of the iron phosphate coating and combines with the outer surface of the substrate, which can improve the performance of the iron phosphate coating. The bonding strength between the layer and the substrate can be improved, and the excellent conductivity of boron can be used to form a conductive network after filling the pores of the iron phosphate coating layer, fully improving the stability of the iron phosphate coating layer and fully ensuring the cycle performance of the substrate.

Embodiments of the present invention provide a method for preparing a ternary cathode material. This method can first coat the surface of a substrate to form an iron phosphate coating layer through a precipitation method, which can reduce direct contact between the substrate and the electrolyte, and can improve the base material. The cycle performance of the material; this method can also coat the outer circumference of the iron phosphate coating with a boron coating layer through a solid-phase method, and enable the part of the boron coating layer to fill the pores, and penetrate through the pores to connect with the outside of the substrate. Surface bonding, so it can not only further prevent the electrolyte from contacting the substrate, but also improve the bonding strength between the iron phosphate coating layer and the substrate based on the cycle performance of the substrate. It can also use the excellent conductivity of boron to fill the The pores of the iron phosphate coating layer form a conductive network, which fully improves the stability of the iron phosphate coating layer and fully ensures the cycle performance of the substrate.

Embodiments of the present invention also provide a cathode sheet and a battery, which include the above-mentioned ternary cathode material. Therefore, it has the advantage of excellent cycle performance.

Description of drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is an SEM image of the ternary cathode material provided in Embodiment 1 of the present invention.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the examples, the conditions should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

The features and performance of the present invention will be described in further detail below with reference to examples.

Embodiments of the present invention provide a ternary cathode material, which includes a lithium nickel cobalt manganate base material, an iron phosphate coating layer, and a boron coating layer. In detail, the iron phosphate coating layer coats the outer peripheral side of the lithium nickel cobalt manganate base material. The boron coating layer covers the outer peripheral side of the iron phosphate coating layer, and part of the boron coating layer penetrates through the pores of the iron phosphate coating layer to combine with the outer surface of the lithium nickel cobalt manganate base material.

On the one hand, through the setting of the iron phosphate coating layer, the direct contact between the substrate and the electrolyte can be reduced, and the cycle performance of the substrate can be improved; at the same time, through the setting of the boron coating layer, the pores of the iron phosphate coating layer can be filled, This can further prevent the electrolyte from contacting the substrate and further improve the cycle performance of the substrate; on the other hand, the boron coating penetrates through the pores of the iron phosphate coating and combines with the outer surface of the substrate, which can improve the performance of the iron phosphate coating. The bonding strength between the layer and the substrate can be improved, and the excellent conductivity of boron can be used to form a conductive network after filling the pores of the iron phosphate coating layer, fully improving the stability of the iron phosphate coating layer and fully ensuring the cycle performance of the substrate.

It should be noted that in the embodiment of the present invention, the mass of the iron phosphate coating layer accounts for 0.5-5% of the total mass of the ternary cathode material. That is, the coating amount of the iron phosphate coating layer is 0.5-5%. By limiting the coating amount of the iron phosphate coating, on the one hand, it can prevent the electrolyte from contacting the substrate to a certain extent and improve the cycle performance of the substrate; on the other hand, it also facilitates the part of the boron coating to fill the pores. , and penetrate into the pores to combine with the base material to improve the bonding strength between the iron phosphate coating layer and the base material, and fully improve the cycle performance of the base material.

It should also be noted that in this embodiment, the mass of the boron coating layer accounts for 0.5-5% of the total mass of the ternary cathode material. By limiting the coating amount of the iron phosphate coating layer and the coating amount of the boron coating layer, the cycle performance of the substrate can be guaranteed, and the bonding strength and stability between the iron phosphate coating layer and the substrate can be fully improved. The performance of the substrate to improve the performance of the battery.

Embodiments of the present invention also provide a method for preparing the ternary cathode material with the above structure, which includes:

S1: Mix the suspension containing the lithium nickel cobalt manganate base material and the iron phosphate solution, dry it and perform the first sintering to form an iron phosphate coating layer on the outer peripheral side of the lithium nickel cobalt manganate base material. ;

S2: Mix the boron source and the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer, and perform secondary sintering to form a boron coating layer on the outer peripheral side of the iron phosphate coating layer, and This allows part of the boron coating layer to fill the pores and penetrate through the pores to bond with the outer surface of the lithium nickel cobalt manganate substrate.

Specifically, in step S1, the suspension is obtained by dispersing the lithium nickel cobalt manganate substrate into a first solvent. The dispersion process can be performed in a stirrer, and the first solvent includes an organic solvent or water. The iron phosphorus solution is obtained by co-dispersing the iron source and the phosphorus source in a second solvent. The dispersion process can also be performed in a stirrer, and the second solvent includes water. At the same time, the iron source can be selected as a water-soluble iron salt, for example, ferric nitrate, ferric chloride, etc. can be selected. The phosphorus source includes at least one of phosphoric acid and water-soluble phosphorus salts. For example, either phosphoric acid or water-soluble phosphorus salts such as sodium phosphate and diammonium hydrogen phosphate can be selected. After mixing the suspension and the iron phosphate solution for the first sintering, the surface of the substrate can be coated with a precipitation method to form an iron phosphate coating layer, which can reduce the direct contact between the substrate and the electrolyte and improve the cycle performance of the substrate. . At the same time, an iron phosphate coating layer is formed through co-precipitation, making the iron phosphate coating layer porous.

As an optional solution, in the embodiment of the present invention, in the iron phosphorus solution, the concentration of iron ions is 0.05-2.5 mol/L, and the concentration of phosphate is 0.05-2.5 mol/L. By controlling the concentration of iron ions and phosphate ions, it can be ensured that the iron phosphate coating layer formed after the sintering operation can form multiple pores in the structure, so that the boron coating layer can penetrate through the pores to ensure the iron phosphate coating layer. The bonding strength between the layer and the base material can ensure the cycle performance of the base material.

Further, the drying temperature is 100-250°C, and the drying time is 4-6 hours. As the drying temperature increases, the drying time shortens and can be adjusted according to needs. At the same time, the sintering temperature for the first sintering is 400-800°C, the sintering time is 6-12 hours, and the sintering environment is a pure oxygen environment. As the sintering temperature increases, the sintering time also shortens. By selecting the temperature, time and environment of drying and sintering, on the one hand, the operating efficiency can be ensured, and the formation efficiency and quality of the iron phosphate coating layer can be ensured; on the other hand, the formation of pores in the iron phosphate coating layer can be ensured, so as to ensure the formation of pores in the iron phosphate coating layer. It can facilitate the thickness of the boron source coating process and facilitate the penetration of the boron source to further improve the bonding strength between the iron phosphate coating layer and the substrate, and at the same time improve the stability of the iron phosphate coating layer to improve the cycle performance of the substrate. .

In step S2, the boron source can be selected from boron oxide, boric acid or borate. The boron source and the lithium nickel cobalt manganate substrate coated with an iron phosphate coating are mixed by using a ball mill, which can improve Particle uniformity. After mixing and secondary sintering, the boron coating layer can be formed on the outer peripheral side of the iron phosphate coating layer by solid phase method, and the boron coating layer can fill the pores and penetrate into the nickel, cobalt and manganese through the pores. bonded to the outer surface of the lithium acid substrate. The boron coating layer is coated on the outer peripheral side of the iron phosphate coating layer through the solid phase method, so that part of the boron coating layer can fill the pores, penetrate through the pores and combine with the outer surface of the substrate, which can further prevent the electrolyte In contact with the substrate, the cycle performance of the substrate can also improve the bonding strength between the iron phosphate coating layer and the substrate. The excellent conductivity of boron can also be used to form a conductive network after filling the pores of the iron phosphate coating layer. Fully improve the stability of the iron phosphate coating layer and fully ensure the cycle performance of the substrate.

As an optional solution, in the embodiment of the present invention, the sintering temperature of the second sintering is 700-800°C, the sintering time is 4-8 hours, and the sintering environment is a pure oxygen environment. The purpose of the second sintering is to achieve coating of the boron source through the solid-phase method to obtain a ternary material coated with boron and ferrophosphate. At the same time, by limiting the temperature, time and environment of the second sintering, on the one hand, the coating quality of the boron coating layer can be ensured, and the part of the boron coating layer can penetrate through the pores and combine with the substrate, so as to be able to Fully improve the bonding strength between the iron phosphate coating layer and the base material, and improve the cycle performance of the entire ternary cathode material; on the other hand, it can also ensure the uniformity of the boron coating layer when it penetrates into multiple pores to ensure that it can be used in the iron phosphate A conductive network is formed in the coating layer to fully improve the stability of the iron phosphate coating layer to further improve the cycle performance of the ternary cathode material.

Embodiments of the present invention also provide a cathode sheet, which includes a cathode current collector and a cathode active material layer. The positive electrode current collector may be aluminum foil or a composite current collector. The embodiments of the present invention will be described using aluminum foil as an example. The positive active material layer is obtained by coating the positive active slurry on at least one side of the positive current collector and then drying. The positive electrode active slurry includes the above-mentioned ternary positive electrode material, and also includes a conductive agent, a binder and a solvent. For example, the conductive agent can be acetylene black, carbon black, etc., and the binder can be polyvinyl fluoride (PVDF). ), the solvent can be N-methylpyrrolidone. The mass ratio of the ternary cathode material, the conductive agent and the binder can be selected as (5-10): (0.1-1): (0.1-1). For example, the mass ratio can be selected as 9.2:0.5:0.3. The drying temperature can be selected from 80-120℃, and the drying time can be selected from 10-24h.

The positive electrode sheet is prepared from the above-mentioned ternary positive electrode material. Therefore, the positive electrode sheet also has the characteristics of excellent cycle performance.

An embodiment of the present invention also provides a battery, which includes the above-mentioned positive electrode sheet, a casing, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet, separator and negative electrode sheet are stacked in sequence and laminated or rolled to form an electrode core. After the electrode core is installed into the case and the electrolyte is injected, the battery can be obtained. The battery may be a rectangular lithium-ion battery, a cylindrical battery or a button battery. The embodiments of the present invention will be described using a button battery as an example.

As an optional solution, the negative electrode sheet can be selected as a metal lithium sheet, or it can be selected as a composite structure formed by a current collector and a negative electrode active layer, and the active particles in the negative electrode active layer can be selected as graphite, etc., the embodiments of the present invention are Let's take a metal lithium sheet as an example. The separator can be made of PP material, PE (polyethylene) material, or a composite structure obtained by combining PP (polypropylene) material and PE material. The embodiments of the present invention are all carried out using PP as an example. illustrate. The electrolyte can be a mixed solution of lithium hexafluorophosphate, and specifically the LiPF ₆ -EC/DMC system, where EC is ethylene carbonate and DMC is dimethyl carbonate.

The battery includes the above-mentioned positive electrode sheet. Therefore, the battery also has the advantage of high cycle performance.

The preparation process and cycle performance of the battery will be introduced in detail below in conjunction with the examples and comparative examples:

Example 1

This embodiment provides a battery, which is prepared by the following method:

S1: Prepare the ternary cathode material, and step S1 specifically includes:

S11: Take 5g of lithium nickel cobalt manganate base material (LiNi _0.8 Co _0.10 Mn _0.10 O ₂ ) and 20 mL of water and stir evenly in a stirrer to obtain a suspension containing lithium nickel cobalt manganate base material;

S12: Weigh 0.18g ferric chloride hexahydrate and 0.076g diammonium hydrogen phosphate and dissolve them in 5mL of water to obtain an iron-phosphorus solution, in which the solubility of iron ions is 0.88mol/L and the solubility of phosphate ions is 0.88mol/L;

S13: Slowly mix the iron phosphorus solution with the suspension, mix evenly, place it in an oven to dry at 160°C for 4 hours, and place it in a roller kiln to calcine for 8 hours at 700°C in a pure oxygen atmosphere. The outer peripheral side of the lithium nickel cobalt manganate base material is coated to form an iron phosphate coating layer;

S14: Mix the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer and 0.15g boron oxide, and place it in a roller kiln to calcine for 6 hours at 700°C in a pure oxygen atmosphere to coat the iron phosphate layer. The outer peripheral side of the layer is coated to form a boron coating layer, so that part of the boron coating layer can fill the pores and penetrate through the pores to combine with the outer surface of the lithium nickel cobalt manganate substrate. Its morphology is shown in Figure 1 , it can be seen that the surface of the secondary spherical ternary cathode material is wrapped with a uniform coating structure.

S2: Preparation of positive electrode sheet;

Step S2 specifically includes selecting aluminum foil as the cathode current collector, coating the cathode active slurry on both sides of the aluminum foil, air drying at 80°C for 8 hours, and then vacuum drying at 120°C for 12 hours; wherein, the cathode active slurry includes step S1 The prepared ternary cathode material also includes a conductive agent, a binder and a solvent. The conductive agent is acetylene black, the binder is PVDF, the solvent is N-methylpyrrolidone, the ternary cathode material, the conductive agent and the binder. The mass ratio of the three is 9.2:0.5:0.3.

S3: Preparing the battery

Use the metal lithium sheet as the negative electrode sheet, the structure prepared by S2 as the positive electrode sheet, PP as the separator, and 1M LiPF6-EC/DMC (1:1, v/v) as the electrolyte in an argon-protected glove box. The 2032 type button battery was obtained during the assembly.

Example 2

This embodiment provides a battery. The difference between the battery preparation method and the battery preparation method provided in Embodiment 1 is that in Embodiment 2, step S1 specifically includes:

S11: Take 5g of lithium nickel cobalt manganate base material (LiNi _0.8 Co _0.10 Mn _0.10 O ₂ ) and 20 mL of water and stir evenly in a stirrer to obtain a suspension containing lithium nickel cobalt manganate base material;

S12: Weigh 0.36g ferric chloride hexahydrate and 0.152g diammonium hydrogen phosphate and dissolve them in 5mL of water to obtain an iron-phosphorus solution, in which the solubility of iron ions is 0.22mol/L and the solubility of phosphate ions is 0.22mol/L;

S13: Slowly mix the iron phosphorus solution with the suspension, mix evenly, place it in an oven to dry at 160°C for 4 hours, and place it in a roller kiln to calcine for 8 hours at 700°C in a pure oxygen atmosphere. The outer peripheral side of the lithium nickel cobalt manganate base material is coated to form an iron phosphate coating layer;

S14: Mix the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer and 0.075g boron oxide, and place it in a roller kiln to calcine for 6 hours at 700°C in a pure oxygen atmosphere to coat the iron phosphate layer. The outer peripheral side of the layer is coated to form a boron coating layer, so that part of the boron coating layer can fill the pores and penetrate through the pores to be combined with the outer surface of the lithium nickel cobalt manganate base material.

Example 3

This embodiment provides a battery. The difference from the battery preparation method provided in Embodiment 1 is that in Embodiment 3, step S1 specifically includes:

S11: Take 5g of lithium nickel cobalt manganate base material (LiNi _0.8 Co _0.10 Mn _0.10 O ₂ ) and 20 mL of water and stir evenly in a stirrer to obtain a suspension containing lithium nickel cobalt manganate base material;

S12: Weigh 0.09g ferric chloride hexahydrate and 0.038g diammonium hydrogen phosphate and dissolve them in 5mL of water to obtain an iron-phosphorus solution, in which the solubility of iron ions is 0.44mol/L and the solubility of phosphate ions is 0.44mol/L;

S13: Slowly mix the iron phosphorus solution with the suspension, mix evenly, place it in an oven to dry at 160°C for 4 hours, and place it in a roller kiln to calcine for 8 hours at 700°C in a pure oxygen atmosphere. The outer peripheral side of the lithium nickel cobalt manganate base material is coated to form an iron phosphate coating layer;

S14: Mix the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer and 0.3g boron oxide, and place it in a roller kiln to calcine for 6 hours at 700°C in a pure oxygen atmosphere to coat the iron phosphate layer. The outer peripheral side of the layer is coated to form a boron coating layer, so that part of the boron coating layer can fill the pores and penetrate through the pores to be combined with the outer surface of the lithium nickel cobalt manganate base material.

Comparative example 1

Comparative Example 1 provides a battery, and its difference from the battery preparation method provided in Example 1 is that in Comparative Example 1, step S1 specifically includes:

S11: Take 5g of lithium nickel cobalt manganate base material (LiNi _0.8 Co _0.10 Mn _0.10 O ₂ ) and 20 mL of water and stir evenly in a stirrer to obtain a suspension containing lithium nickel cobalt manganate base material;

S12: Weigh 0.18g ferric chloride hexahydrate and 0.076g diammonium hydrogen phosphate and dissolve them in 5mL of water to obtain an iron-phosphorus solution, in which the solubility of iron ions is 0.88mol/L and the solubility of phosphate ions is 0.88mol/L;

S13: Slowly mix the iron phosphorus solution with the suspension, mix evenly, place it in an oven to dry at 160°C for 4 hours, and place it in a roller kiln to calcine for 8 hours at 700°C in a pure oxygen atmosphere. The outer peripheral side of the lithium nickel cobalt manganate base material is coated with an iron phosphate coating layer.

Comparative example 2

Comparative Example 2 provides a battery, and its difference from the battery preparation method provided in Example 1 is that in Comparative Example 2, step S1 specifically includes:

S11: Mix 5g of lithium nickel cobalt manganate substrate (LiNi _0.8 Co _0.10 Mn _0.10 O ₂ ) and 0.15g of boron oxide, place it in a roller kiln and calcine it for 6 hours at 700°C in a pure oxygen atmosphere to obtain boron coating. Lithium nickel cobalt manganate cathode material.

Experimental example

The batteries prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to electrochemical performance tests at 25°C and 3.0-4.5V. The results are shown in Table 1.

Table 1. Battery electrochemical performance test results

project	0.1C discharge capacity mAh/g	Discharge specific capacity mAh/g after 100 cycles	Cycle retention rate
Example 1	195.2	179.4	91.9%
Example 2	198.4	179.2	90.3%
Example 3	193.3	173.8	89.9%
Comparative example 1	199.7	169.1	84.7%
Comparative example 2	200.6	168.4	83.4%

According to the data shown in Table 1, compared with batteries prepared from cathode materials coated only with iron phosphate or only with boron, the batteries provided by Examples 1-3 of the present invention are coated with both iron phosphate and boron. The battery prepared from the cathode material has better cycle performance and excellent cycle stability. At the same time, comparing the performance test results of Example 1 and Example 2, it can be seen that when the coating amount of iron phosphate is increased and the coating amount of boron is reduced, the coating effect of iron phosphate decreases, making the cycle stability of the battery relatively low. Reduced somewhat. Comparing the performance test results of Example 1 and Example 3, it can be seen that when the coating amount of iron phosphate is reduced and the coating amount of boron is increased, the boron coating has uneven effects, making the cycle stability of the battery relatively low. .

In summary, embodiments of the present invention provide a ternary cathode material and a preparation method thereof that can ensure both cycle performance and coating layer bonding strength. Embodiments of the present invention also provide a cathode sheet and a battery, which include the above-mentioned ternary cathode material. Therefore, it has the advantage of excellent cycle performance.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A ternary cathode material, which is characterized by including:

   Lithium nickel cobalt manganate substrate;

   An iron phosphate coating layer is coated on the outer peripheral side of the lithium nickel cobalt manganate base material;

   A boron coating layer is coated on the outer peripheral side of the iron phosphate coating layer, and part of the boron coating layer penetrates into the lithium nickel cobalt manganate base material through the pores of the iron phosphate coating layer. The outer surface of the combination.
2. The ternary cathode material according to claim 1, characterized in that:

   The mass of the iron phosphate coating layer accounts for 0.5-5% of the total mass of the ternary cathode material.
3. The ternary cathode material according to claim 1, characterized in that:

   The mass of the boron coating layer accounts for 0.5-5% of the total mass of the ternary cathode material.
4. A method for preparing the ternary cathode material according to any one of claims 1 to 3, characterized in that it includes:

   Mix the suspension containing the lithium nickel cobalt manganate base material with the iron phosphorus solution, dry it and perform the first sintering to coat the outer peripheral side of the lithium nickel cobalt manganate base material to form the phosphoric acid iron cladding;

   Mix the boron source and the lithium nickel cobalt manganate substrate coated with the iron phosphate coating layer evenly, and perform secondary sintering to coat the outer peripheral side of the iron phosphate coating layer to form the A boron coating layer is formed, and part of the boron coating layer is penetrated through the pores of the iron phosphate coating layer to be combined with the outer surface of the lithium nickel cobalt manganate substrate.
5. The preparation method of ternary cathode material according to claim 4, characterized in that:

   The suspension is obtained by dispersing the lithium nickel cobalt manganate base material in a first solvent, and the first solvent includes an organic solvent or water;

   The iron phosphorus solution is obtained by co-dispersing an iron source and a phosphorus source in a second solvent, and the second solvent includes water.
6. The preparation method of ternary cathode material according to claim 5, characterized in that:

   The iron source includes water-soluble iron salts;

   and / or,

   The phosphorus source includes at least one of phosphoric acid and water-soluble phosphorus salts;

   and / or,

   The boron source includes at least one of boron oxide, boric acid and borate.
7. The preparation method of ternary cathode material according to claim 4, characterized in that:

   In the iron phosphorus solution, the concentration of iron ions is 0.05-2.5 mol/L, and the concentration of phosphate is 0.05-2.5 mol/L.
8. The preparation method of ternary cathode material according to claim 4, characterized in that:

   The drying temperature is 100-250℃, and the drying time is 4-6h;

   and / or;

   The sintering temperature for the first sintering is 400-800℃, the sintering time is 6-12h, and the sintering environment is pure oxygen environment;

   and / or,

   The sintering temperature for the second sintering is 700-800°C, the sintering time is 4-8h, and the sintering environment is a pure oxygen environment.
9. A positive electrode sheet is characterized by including:

   positive current collector;

   Positive active material layer, the positive active material layer is obtained by coating at least one side of the positive current collector with a positive active slurry; the positive active slurry includes any one of claims 1 to 3 Ternary cathode material.
10. A battery, characterized by comprising the positive electrode sheet according to claim 9.

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