WO2021068448A1

WO2021068448A1 - Quaternary positive electrode material for lithium ion battery and preparation method therefor, and lithium ion battery

Info

Publication number: WO2021068448A1
Application number: PCT/CN2020/076593
Authority: WO
Inventors: 白艳; 张树涛; 潘海龙
Original assignee: 蜂巢能源科技有限公司
Priority date: 2019-10-10
Filing date: 2020-02-25
Publication date: 2021-04-15
Also published as: CN111430700A; CN111430700B

Abstract

Provided are a quaternary positive electrode material for a lithium ion battery and a preparation method therefor, and a lithium ion battery. The quaternary positive electrode material comprises an inner core and a coating layer, wherein the coating layer is formed on at least part of a surface of the inner core. The quaternary positive electrode material has a composition as represented by formula (I), Li_xNi_aCo_bMn_cAl_dM_yO₂ (I) where 1.00 ≤ x ≤ 1.05, 0.00 ≤ y ≤ 0.05, 0.3 ≤ a ≤ 0.92, 0.03 ≤ b ≤ 0.06, 0.01 ≤ c ≤ 0.03, 0.01 ≤ d ≤ 0.03, and a+b+c+d = 1; and M is selected from at least one of elements of a second main group, elements of a third main group, elements of a fourth main group, elements of a fifth main group, elements of a fourth subgroup and elements of a fifth subgroup. For the quaternary positive electrode material, by introducing a doping element into the inner core and forming the coating layer, the heat stability and cycle performance of the material can be improved while the material maintains a high nickel capacity.

Description

Quaternary positive electrode material for lithium ion battery and preparation method thereof and lithium ion battery

Technical field

The present invention relates to the field of electrochemistry. Specifically, the present invention relates to a quaternary positive electrode material for lithium ion batteries, a preparation method thereof, and lithium ion batteries.

Background technique

Lithium-ion batteries are widely used in electric vehicles, hybrid vehicles and energy storage systems due to their high capacity and high energy density. As one of the core components of lithium-ion batteries, cathode materials have a significant impact on the performance of lithium-ion batteries.

Researchers have found that high-nickel cathode materials are gradually replacing LiCoO ₂ cathode materials because of their high capacity and low price. However, high-nickel cathode materials have poor cycle performance. In order to improve the performance of the battery, it is necessary to reduce the residual alkali content on the surface of the positive electrode material, otherwise it will cause the positive electrode material to gel in the homogenization process and hinder its industrial application. In addition, the positive electrode material in the battery is in contact with the electrolyte, and the positive electrode material is easily chemically reacted with the electrolyte, which causes the transition metal in the positive electrode material to dissolve into the electrolyte, thereby increasing the interface impedance of the positive electrode material and reducing the capacity and cycle of the battery. performance. It can be seen that the existing cathode materials for lithium-ion batteries still need to be improved.

Summary of the invention

In view of this, the present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an object of the present invention is to provide a quaternary positive electrode material for lithium ion batteries, a preparation method thereof, and lithium ion batteries. The quaternary cathode material introduces doping elements into the core and forms a coating layer, which can improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

In one aspect of the present invention, the present invention proposes a quaternary cathode material for lithium ion batteries. According to an embodiment of the present invention, the quaternary positive electrode material includes an inner core and a coating layer, the coating layer is formed on at least part of the surface of the core, and the quaternary positive electrode material has the formula (I) composition,

Li _x Ni _a Co _b Mn _c Al _d M _y O ₂ (I)

In formula (I), 1.00≤x≤1.05, 0.00≤y≤0.05, 0.3≤a≤0.92, 0.03≤b≤0.06, 0.01≤c≤0.03, 0.01≤d≤0.03, a+b+c+d= 1. M is at least one selected from the group consisting of the second main group element, the third main group element, the fourth main group element, the fifth main group element, the fourth subgroup element, and the fifth subgroup element.

The quaternary cathode material for a lithium ion battery according to an embodiment of the present invention has a core-shell structure including an inner core and a coating layer. The inner core can be obtained by doping nickel, cobalt, manganese, aluminum and quaternary material (NCMA material) with M element, and simultaneously With a coating layer, the quaternary positive electrode material as a whole has the composition shown in formula (I). The quaternary cathode material introduces doping elements into the core and forms a coating layer, which can improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

In addition, the quaternary cathode material according to the foregoing embodiment of the present invention may also have the following additional technical features:

In some embodiments of the present invention, M is at least one selected from Mg, Ba, B, Al, Si, P, Ti, Zr, and Nb.

In some embodiments of the present invention, M is Al, Zr, or B.

In some embodiments of the present invention, M is Al, Ti, Nb.

In some embodiments of the present invention, M is Al, Mg, Ti.

In another aspect of the present invention, the present invention provides a method for preparing the quaternary cathode material of the foregoing embodiment. According to an embodiment of the present invention, the method includes: (1) mixing a quaternary cathode material precursor, a lithium source, and a dopant to obtain a first mixture; (2) performing a first sintering on the first mixture Processing to obtain a quaternary positive electrode material core; (3) mixing the quaternary positive electrode material core with the first coating agent to obtain a second mixture; (4) performing a second sintering treatment on the second mixture, Obtain a primary coated product; (5) mix the primary coated product with a second coating agent to obtain a third mixture; and (6) perform a calcination treatment on the third mixture to obtain the quaternary Cathode material. The method is simple and convenient to operate and easy to industrially implement, and the prepared quaternary positive electrode material can improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

In addition, the method for preparing a quaternary cathode material according to the foregoing embodiment of the present invention may also have the following additional technical features:

In some embodiments of the present invention, the quaternary cathode material precursor has a composition represented by formula (II), Ni _a Co _b Mn _c Al _d (OH) ₂ (II). In formula (II), 0.3≤a≤0.92, 0.03≤b≤0.06, 0.01≤c≤0.03, 0.01≤d≤0.03, a+b+c+d=1;

In some embodiments of the present invention, the lithium source includes at least one selected from the group consisting of lithium nitrate, lithium carbonate, and lithium hydroxide monohydrate.

In some embodiments of the present invention, the dopant is selected from the group consisting of zirconium hydroxide, zirconium oxide, titanium oxide, magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium nitrate, barium hydroxide, aluminum oxide, aluminum hydroxide , At least one of aluminum oxyhydroxide, zinc oxide, niobium pentoxide, etc.;

In some embodiments of the present invention, the first coating agent includes at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum oxyhydroxide, etc.;

In some embodiments of the present invention, the second coating agent includes at least one selected from boric acid, boron oxide, lithium phosphate, lithium niobate, and the like.

In some embodiments of the present invention, in step (1), the molar ratio of the quaternary cathode material precursor to the lithium element in the lithium source is 1: (1.00 to 1.05); the quaternary cathode material precursor The mass ratio of the doping element in the body to the dopant is 1: (0.001 to 0.003).

In some embodiments of the present invention, in step (3), the mass ratio of the core of the quaternary positive electrode material to the coating element in the first coating agent is 1: (0.0005-0.001).

In some embodiments of the present invention, in step (5), the mass ratio of the coating elements in the primary coating product and the second coating agent is 1:(0.001-0.01).

In some embodiments of the present invention, the first sintering treatment is completed at 700-820° C. for 8-20 hours.

In some embodiments of the present invention, the second sintering treatment is completed at 600-700°C for 6-15 hours.

In some embodiments of the present invention, the calcination treatment is completed at 300-600°C for 8-18 hours.

In some embodiments of the present invention, before step (5), it further comprises: performing water washing treatment and drying treatment on the primary coated product.

In some embodiments of the present invention, in the water washing treatment, the mass ratio of the primary coated product to water is (1-2):1, and the water washing treatment is performed at a stirring rate of 500-800 rpm for 30- Completed in 600s.

In some embodiments of the present invention, the drying treatment is performed at 100 to 180° C. for 3 to 20 hours to complete.

In another aspect of the present invention, the present invention provides a lithium ion battery. According to an embodiment of the present invention, the lithium ion battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte; wherein, the positive electrode includes: a positive electrode current collector and a positive electrode material supported on the positive electrode current collector, and the positive electrode material includes : A positive electrode active material, a positive electrode conductive agent and a positive electrode binder; wherein the positive electrode active material is the quaternary positive electrode material described in the above embodiment. The negative electrode includes a negative electrode current collector and a negative electrode material supported on the negative electrode current collector, and the negative electrode material includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

The lithium ion battery according to the embodiment of the present invention adopts the quaternary positive electrode material of the foregoing embodiment as the positive electrode active material, and has all the features and advantages described above for the quaternary positive electrode material, and will not be repeated here. In general, the lithium-ion battery has a higher capacity and better cycle stability.

Description of the drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is a schematic flow chart of a method for preparing a quaternary cathode material according to an embodiment of the present invention;

2 is a graph of the first charge and discharge of a battery made of the quaternary positive electrode material prepared in Example 1 of the present invention;

3 is a graph showing the first charge and discharge curve of a battery made of the quaternary positive electrode material prepared in Comparative Example 1 of the present invention;

4 is a graph showing the first charge and discharge curve of a battery made of the quaternary positive electrode material prepared in Comparative Example 2 of the present invention;

5 is a graph showing the first charge and discharge curve of a battery made of the quaternary positive electrode material prepared in Comparative Example 3 of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. The embodiments described below are exemplary, and are only used to explain the present invention, but should not be construed as limiting the present invention. Where specific techniques or conditions are not indicated in the examples, it shall be carried out in accordance with the techniques or conditions described in the literature in the field or in accordance with the product specification. The reagents or instruments used without the manufacturer's indication are all conventional products that can be purchased on the market.

In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

Li _x Ni _a Co _b Mn _c Al _d M _y O ₂ (I)

Specifically, in formula (I), x can be 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, etc., y can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, etc., and a can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.92, etc., b can be 0.03, 0.04, 0.05, 0.06, etc., c can be 0.01, 0.02, 0.03, etc., d can be 0.01, 0.02, 0.03, etc., and a, b, c, d satisfies a+b+c+d=1.

Specifically, M is the doping element and/or coating element of the NCMA material, which can exist in the core of the quaternary positive electrode material, or in the coating layer of the quaternary positive electrode material, or in the coating at the same time. In the layer. As a result, it is possible to improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

According to an embodiment of the present invention, M may be at least one selected from Mg, Ba, B, Al, Si, P, Ti, Zr, and Nb. By using the above elements to dope and/or coat the NCMA material, the thermal stability and cycle performance of the material can be improved while maintaining the high nickel capacity of the material.

According to a preferred embodiment of the present invention, M is Zr, Al, B. Among them, Zr is the doping element in the core of the NCMA material, which can maintain the material with a higher capacity, and Al and B as the coating elements of the core of the NCMA material can play a role in shielding the surface active sites of the core of the NCMA material, effectively reducing the positive electrode The occurrence of side reactions between the material and the electrolyte is further conducive to improving the cycle performance and thermal stability of the material.

According to a preferred embodiment of the present invention, M is Al, Ti, Nb. Among them, Ti is the doping element in the core of the NCMA material, which can maintain the material with a high capacity, and Al and Nb as the coating elements of the core of the NCMA material can play a role in shielding the surface active sites of the core of the NCMA material and effectively reduce the positive electrode. The occurrence of side reactions between the material and the electrolyte is further conducive to improving the cycle performance and thermal stability of the material.

According to a preferred embodiment of the present invention, M is Al, Mg, Ti. Among them, Mg and Ti are the doping elements in the core of NCMA material, which can maintain the material with a high capacity, and Al, as the coating element of the core of NCMA material, can play a role in shielding the surface active sites of the core of NCMA material and effectively reduce the positive electrode. The occurrence of side reactions between the material and the electrolyte is further conducive to improving the cycle performance and thermal stability of the material.

The inventor found in the research that the doping of Al, Mg, Zr, Ti and other elements can stabilize the structure of the material, improve the electronic conductivity and ionic conductivity, increase the capacity of the material, and improve the cycle stability of the material. The role of thermal stability. In addition, the coating can resist the corrosion of the electrolyte to the positive electrode material, prevent the dissolution of metal ions in the positive electrode material, reduce the surface impedance, and improve the cycle stability and thermal stability.

In another aspect of the present invention, the present invention provides a method for preparing the quaternary cathode material of the foregoing embodiment. According to an embodiment of the present invention, the method includes: (1) mixing a quaternary cathode material precursor, a lithium source, and a dopant to obtain a first mixture; (2) performing a first sintering treatment on the first mixture; Obtain the quaternary positive electrode material core; (3) Mix the quaternary positive electrode material core with the first coating agent to obtain the second mixture; (4) Perform the second sintering treatment on the second mixture to obtain the primary coated product; (5) Mixing the primary coating product with the second coating agent to obtain a third mixture; and (6) calcining the third mixture to obtain a secondary coated quaternary cathode material. The method is simple and convenient to operate and easy to industrially implement, and the prepared quaternary positive electrode material can improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

The method for preparing a quaternary cathode material according to an embodiment of the present invention will be further described in detail below. According to an embodiment of the present invention, referring to FIG. 1, the method includes:

S100: Obtain the first mixture

In this step, the quaternary cathode material precursor, the lithium source, and the dopant are mixed to obtain the first mixture.

According to the embodiment of the present invention, the specific type of the quaternary cathode material precursor is not particularly limited, and those skilled in the art can choose according to actual needs, for example, nickel-cobalt-manganese-aluminum hydroxide is used. The method provided by the present invention can dope conventional commercially available quaternary positive electrode material precursors by using dopants, and through subsequent coating, the prepared quaternary positive electrode material has a higher nickel capacity while maintaining high nickel capacity. Good thermal stability and cycle performance. In some embodiments of the present invention, the quaternary cathode material precursor has a composition as shown in formula (II),

Ni _a Co _b Mn _c Al _d (OH) ₂ (II).

In formula (II), 0.3≤a≤0.92, 0.03≤b≤0.06, 0.01≤c≤0.03, 0.01≤d≤0.03, and a+b+c+d=1. In formula (II), a can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.92, etc., b can be 0.03, 0.04, 0.05, 0.06, etc., c can be 0.01, 0.02, 0.03, etc., and d can be It is 0.01, 0.02, 0.03, etc., and a, b, c, and d satisfy a+b+c+d=1.

According to the embodiment of the present invention, the specific type of the above-mentioned lithium source is not particularly limited, and a lithium source commonly used in the art for preparing a positive electrode active material of a lithium battery can be used. According to a specific example of the present invention, the above-mentioned lithium source may include at least one selected from lithium nitrate, lithium carbonate, and lithium hydroxide monohydrate. This type of lithium source has a wide range of sources, is cheap and easy to obtain, and has good compatibility with nickel, cobalt, manganese, aluminum and doping elements (ie, M element).

According to an embodiment of the present invention, the doping element may be provided in the form of M oxide, hydroxide, chloride, or the like. In other words, the above-mentioned dopants include those selected from the group consisting of zirconium hydroxide (Zr(OH) ₄ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), magnesium hydroxide (Mg(OH) ₂ ), magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ), magnesium nitrate (Mg(NO ₃ ) ₂ ), barium hydroxide (Ba(OH) ₂ ), aluminum oxide (Al ₂ O ₃ ), aluminum hydroxide (Al(OH) ₃ ) At least one of aluminum oxyhydroxide (AlOOH), zinc oxide (ZnO), niobium pentoxide (Nb ₂ O ₅ ), and the like. By using the above dopants, the required doping elements can be introduced into the core of the quaternary positive electrode material, so as to improve the thermal stability and cycle performance of the material while maintaining the high nickel capacity of the material.

According to an embodiment of the present invention, the quaternary cathode material precursor, the lithium source and the doping element may be mixed in the following ratio: the molar ratio of the lithium element in the quaternary cathode material precursor to the lithium source is 1: (1.00 ~ 1.05), For example, 1:1.00, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, etc.; the mass ratio of the precursor of the quaternary cathode material to the doping element (ie M element) in the dopant is 1 : (0.001～0.003), such as 1:0.001, 1:0.002, 1:0.003, etc. As a result, the capacity, thermal stability and cycle performance of the prepared quaternary cathode material can be further improved.

S200: First sintering treatment

In this step, the first sintering process is performed on the first mixture to obtain the core of the quaternary cathode material. Specifically, the first sintering treatment may be performed in an oxygen atmosphere, so as to introduce doping elements into the NCMA material and form the core of the quaternary cathode material.

According to an embodiment of the present invention, the first sintering treatment can be completed at 700-820° C. for 8-20 hours. Specifically, the sintering temperature may be 700°C, 720°C, 750°C, 790°C, 820°C, etc., and the sintering time may be 8h, 12h, 15h, 18h, 20h, etc. By performing the first sintering treatment under the above conditions, the quality of the quaternary cathode material core obtained by sintering can be further improved.

According to an embodiment of the present invention, after the first sintering process is completed, the core of the quaternary positive electrode material can be cooled and then crushed and sieved to obtain a material with an average particle size of 5-20μm for subsequent processes. The specific particle size can be based on the material used. The particle size of the precursor of the quaternary cathode material is determined.

S300: Obtain the second mixture

In this step, the quaternary positive electrode material core is mixed with the first coating agent, so that the first coating agent uniformly coats the surface of the quaternary positive electrode material core to obtain the second mixture.

According to an embodiment of the present invention, the first coating element may be provided in the form of an oxide, hydroxide, etc. of element M, that is to say, the first coating agent may be selected from alumina (Al ₂ O ₃ ) , Aluminum hydroxide (Al(OH) ₃ ), at least one of... By using the above-mentioned first coating agent to introduce a coating layer containing M element to the surface of the quaternary positive electrode material core, the active sites on the surface of the NCMA material can be effectively shielded, and the occurrence of side reactions between the quaternary positive electrode material core and the electrolyte can be reduced. Improve the thermal stability and cycle performance of the material.

According to an embodiment of the present invention, the quaternary positive electrode material can be mixed with the first coating agent in the following ratio: the mass ratio of the core of the quaternary positive electrode material to the coating element (ie, the M element) in the first coating agent is 1:( 0.0005～0.001), such as 1:0.0005, 1:0.0006, 1:0.0007, 1:0.0008, 1:0.001, etc. As a result, the capacity, thermal stability and cycle performance of the prepared quaternary cathode material can be further improved.

S400: Second sintering treatment

In this step, the second sintering process is performed on the second mixture to obtain a primary coated product. Specifically, the second sintering treatment may be performed in an oxygen atmosphere, so that a stable coating layer is formed on the surface of the core of the quaternary positive electrode material.

According to the embodiment of the present invention, the second sintering treatment can be completed at 600-700°C for 6-15 hours. Specifically, the sintering temperature may be 600°C, 620°C, 680°C, 700°C, etc., and the sintering time may be 6h, 8h, 10h, 12h, 15h, etc. By performing the second sintering treatment under the above conditions, the quality of the primary-coated quaternary cathode material obtained by sintering can be further improved.

According to an embodiment of the present invention, after the second sintering process is completed, the core of the quaternary positive electrode material can be cooled and crushed and sieved to obtain a material with an average particle size of 5-20μm for subsequent processes. The specific particle size can be based on the The particle size of the precursor of the quaternary cathode material is determined.

S500: Obtain the third mixture

In this step, the primary coating product is mixed with the second coating agent, so that the second coating agent is evenly coated on the surface of the primary coated quaternary positive electrode material to obtain the third mixture.

According to an embodiment of the present invention, the second coating element may be provided in the form of an oxide, hydroxide, etc. of element M, that is, the above-mentioned second coating agent may include boric acid (H ₃ BO ₃ ), At least one of boron oxide (B ₂ O _{3) and...} By using the above-mentioned second coating agent to introduce the second coating element to the surface of the quaternary positive electrode material once coated, the active sites on the surface of the NCMA material can be further effectively shielded, and the side reactions between the core of the quaternary positive electrode material and the electrolyte can be further reduced. Occurrence, further improve the thermal stability and cycle performance of the material.

According to an embodiment of the present invention, the quaternary positive electrode material coated once can be mixed with the second coating agent in the following ratio: the mass ratio of the coated element (ie M element) in the first coating product and the second coating agent is 1: (0.001 to 0.01), for example, 1:0.001, 1:0.003, 1:0.005, 1:0.008, 1:0.01, etc. As a result, the capacity, thermal stability and cycle performance of the prepared quaternary cathode material can be further improved.

S600: Calcining treatment

In this step, the third mixture is calcined to obtain a secondary coated quaternary positive electrode material. Specifically, the calcination treatment may be performed in an oxygen atmosphere, so as to stably introduce the second coating element into the quaternary cathode material once coated.

According to the embodiment of the present invention, the calcination treatment can be completed at 300-600°C for 8-18h. Specifically, the calcination temperature may be 300°C, 350°C, 400°C, 450°C, 500°C, 600°C, etc., and the sintering time may be 8h, 12h, 14h, 16h, 18h, etc. By performing the calcination treatment under the above conditions, the quality of the secondary coated quaternary positive electrode material obtained by sintering can be further improved.

According to an embodiment of the present invention, after the calcination process is completed, the quaternary positive electrode material can be cooled and crushed and sieved to obtain a product with an average particle size of 5-20 μm. The specific particle size can be based on the precursor of the quaternary positive electrode material used. The particle size is determined.

In order to further improve the quality of the prepared quaternary positive electrode material, according to an embodiment of the present invention, before S500, the primary coated product may be washed with water and dried. As a result, impurities contained in the primary coated product can be effectively removed. The inventor found in research that the primary coating product contains some residual alkali impurities such as _{Li 2} CO ₃ , LiOH, Li _{2 O, etc.} If the impurities are not removed, the viscosity of the battery slurry will increase or even appear gel-like or jelly-like in the process of making the battery, and the material will not be able to enter the next process.

According to an embodiment of the present invention, in the above-mentioned water washing treatment, the mass ratio of the primary coated product to water may be (1-2):1, and the water washing treatment may be completed at a stirring rate of 500-800 rpm for 30-600 s.

According to an embodiment of the present invention, the above-mentioned drying treatment is completed at 100-180°C for 3-20 hours. Specifically, the drying temperature may be 100°C, 120°C, 140°C, 180°C, etc., and the drying time may be 3h, 5h, 12h, 15h, 18h, 20h, etc. As a result, it is possible to effectively remove the moisture in the material while ensuring that the material deteriorates due to excessive drying temperature or drying time.

In another aspect of the present invention, the present invention provides a lithium ion battery. According to an embodiment of the present invention, the lithium ion battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte; wherein the positive electrode includes: a positive electrode current collector and a positive electrode material supported on the positive current collector, and the positive electrode material includes: a positive electrode active material, a positive electrode Conductive agent and positive electrode binder; wherein, the positive electrode active material is the quaternary positive electrode material of the above-mentioned embodiment. The negative electrode includes a negative electrode current collector and a negative electrode material supported on the negative electrode current collector. The negative electrode material includes: a negative electrode active material, a negative electrode conductive agent and a negative electrode binder.

According to some embodiments of the present invention, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder is not particularly limited, and can be selected according to actual needs. . The positive electrode active material is the quaternary positive electrode material of the above-mentioned embodiment. The specific types of the positive electrode conductive agent and the positive electrode binder are not particularly limited. For example, the positive electrode conductive agent can be conductive carbon black SP or ECP, carbon nanotubes (CNT or WCNT), graphene and other common positive electrode binders. At least one; the positive electrode binder can be at least one of the common positive electrode binders such as polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyacrylic acid (PAA), etc. one. In addition, the positive electrode material can also include common solvents (such as NMP, etc.) for mixing positive electrode materials. The ratio of the solvent to the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is not particularly limited, and those skilled in the art can Choose according to actual needs.

According to some embodiments of the present invention, the negative electrode material includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder; the mass ratio of the negative electrode active material, the negative electrode conductive agent, the negative electrode binder, and the thickening stabilizer is not particularly limited, and can be Choose according to actual needs. The specific types of negative electrode active material, negative electrode conductive agent and negative electrode binder are not particularly limited. The negative electrode activity can be selected from common negative electrode active materials such as natural graphite, artificial graphite, mesophase microspheres, soft carbon and hard carbon. At least one; the negative electrode conductive agent can be at least one of the common negative electrode conductive agents such as conductive carbon black SP or ECP, carbon nanotubes (CNT or WCNT), graphene; the negative electrode binder can be polyvinylidene fluoride ( PVDF), sodium carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyacrylic acid (PAA) and other common negative electrode binders. In addition, the negative electrode material may also include common solvents used for mixing negative electrode materials (such as NMP, deionized water, etc.). The solvent and the negative electrode active material, the negative electrode conductive agent and the negative electrode binder are not particularly limited. Those skilled in the art You can choose according to actual needs.

The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are only descriptive and do not limit the present invention in any way.

Example 1

(1) The cathode material quaternary precursor Ni _a Co _b Mn _c Al _d (OH) ₂ (a=0.88, b=0.06, c=0.03, d=0.03), lithium source and dopant are carried out in the following proportions Dry mixing: the quaternary precursor of the cathode material (nickel-cobalt-manganese-aluminum hydroxide) and the Li element in the lithium source (LiOH) are mixed at a molar ratio of 1:1.035, and the dopant (Zr(OH) ₄ ) is mixed The mass ratio of Zr element and quaternary precursor is 0.003:1. The dry-mixed material is sintered once at 740° C. in an oxygen atmosphere for 10 hours, cooled, pulverized, and sieved to obtain a sintered quaternary positive electrode material (first product).

(2) The above-mentioned first product and the first coating agent (Al ₂ O ₃ ) are mixed uniformly according to the mass ratio of the first product to Al element of 1:0.0005 by the dry method, so that the first coating agent is evenly coated on the first product On the surface, the dry-mixed material is sintered once at 600° C. in an oxygen atmosphere for 6 hours, cooled, pulverized and sieved to obtain a coated quaternary positive electrode material (second product).

(3) Mix the above-mentioned second product with deionized water at a mass ratio of 2:1, and stir at 600 rpm at room temperature for 60 seconds. After filtration, vacuum dry at 150°C for 8 hours to obtain a washed and dried one-time coated four. Yuan cathode material (the third product).

(4) Dry the third product and the second coating agent (B ₂ O ₃ ) according to the mass ratio of the third product to the element B of 0.001:1, and mix uniformly, so that the second coating agent is evenly coated on On the surface of the third product, the dry-mixed material is calcined at a certain temperature of 400° C. under an oxygen atmosphere for 10 hours, cooled, crushed and sieved to obtain a secondary coated quaternary cathode material.

Comparative example 1

(1) The cathode material quaternary precursor Ni _a Co _b Mn _c Al _d (OH) ₂ (a=0.88, b=0.06, c=0.03, d=0.03), lithium source and dopant are carried out in the following proportions Dry mixing: the quaternary precursor of the cathode material (nickel-cobalt-manganese-aluminum hydroxide) and the Li element in the lithium source (LiOH) are mixed at a molar ratio of 1:1.035, and the dopant (Zr(OH) ₄ ) is mixed The mass ratio of Zr element and quaternary precursor is 0.003:1. The dry-mixed material is sintered once in an oxygen atmosphere at 735° C. for 10 hours, cooled, crushed and sieved to obtain a quaternary cathode material product.

Comparative example 2

(2) The above-mentioned first product and the first coating agent (Al ₂ O ₃ ) are mixed uniformly according to the mass ratio of the first product to Al element of 1:0.0005 by the dry method, so that the first coating agent is evenly coated on the first product On the surface, the dry-mixed material is sintered at 600° C. in an oxygen atmosphere for 6 hours, cooled, crushed and sieved to obtain a coated quaternary cathode material product.

Comparative example 3

(2) The above-mentioned first product and the first coating agent (Al ₂ O ₃ ) are mixed uniformly according to the mass ratio of the first product to Al element of 1:0.0005 by the dry method, so that the first coating agent is evenly coated on the first product On the surface, the dry-mixed material is sintered once at 600° C. in an oxygen atmosphere for 6 hours, cooled, pulverized and sieved to obtain a coated quaternary positive electrode material product (second product).

(3) Mix the above-mentioned second product with deionized water at a mass ratio of 2:1, and stir at 600 rpm at room temperature for 60 seconds. After filtration, vacuum dry at 150°C for 8 hours to obtain a washed and dried one-time coated four. Yuan cathode material products.

Test case

(1) The quaternary cathode materials prepared in Example 1 and Comparative Examples 1 to 3 were used to make button batteries for testing, and the first charge-discharge curve was obtained by the test, and the capacity retention after 50 weeks of cycling was tested at room temperature. The results are shown in Figures 2 to 5 and Table 1.

(2) The quaternary cathode materials prepared in Example 1 and Comparative Examples 1 to 3 were respectively subjected to differential scanning calorimetry (DSC test), and the results are shown in Table 2.

Table 1 Cycle performance test results

Table 2 DSC test results

To	实施例1Example 1	对比例1Comparative example 1	对比例2Comparative example 2	对比例3Comparative example 3
DSC温度DSC temperature	230℃230°C	199.32℃199.32℃	203.33℃203.33°C	209.44℃209.44°C

The test results show that the battery made of the secondary-coated quaternary positive electrode material proposed by the present invention has higher capacity and cycle performance than the battery made of the comparative material, and the material has better thermal stability. It can be seen from Comparative Example 1 that the non-coated NCMA quaternary cathode material has low thermal stability, and the cycle performance of the battery produced is significantly reduced. It can be seen from Comparative Examples 2 and 3 that the performance of the NCMA quaternary cathode material coated once has improved compared with the material of Comparative Example 1, but it is still inferior to the material of Example 1. In addition, the material in Comparative Example 2 was not washed and dried before being applied to the battery, and its performance was inferior to Comparative Example 3. This indicates that the impurity generated during a coating process will adversely affect the product performance if it is not removed.

In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean specific features described in conjunction with the embodiment or example , Structure, materials or features are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples and the features of the different embodiments or examples described in this specification without contradicting each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. A person of ordinary skill in the art can comment on the above-mentioned embodiments within the scope of the present invention. The embodiment undergoes changes, modifications, substitutions, and modifications.

Claims

A quaternary positive electrode material for a lithium ion battery, wherein the quaternary positive electrode material comprises a core and a coating layer, the coating layer is formed on at least part of the surface of the core, and the quaternary positive electrode The material has the composition shown in formula (I),

Li x Ni a Co b Mn c Al d M y O 2 (I)

In formula (I), 1.00≤x≤1.05, 0.00≤y≤0.05, 0.3≤a≤0.92, 0.03≤b≤0.06, 0.01≤c≤0.03, 0.01≤d≤0.03, a+b+c+d= 1. M is at least one selected from the group consisting of the second main group element, the third main group element, the fourth main group element, the fifth main group element, the fourth subgroup element, and the fifth subgroup element.
The quaternary cathode material of claim 1, wherein M is at least one selected from Mg, Ba, B, Al, Si, P, Ti, Zr, and Nb.
The quaternary cathode material according to claim 2, wherein M is Al, Zr, B, or M is Al, Ti, Nb, or M is Al, Mg, Ti.
A method for preparing the quaternary positive electrode material according to any one of claims 1 to 3, characterized in that it comprises:

(1) Mixing the precursor of the quaternary cathode material, the lithium source and the dopant to obtain the first mixture;

(2) Perform a first sintering treatment on the first mixture to obtain a quaternary cathode material core;

(3) Mixing the core of the quaternary positive electrode material with the first coating agent to obtain a second mixture;

(4) Perform a second sintering treatment on the second mixture to obtain a primary coated product;

(5) Mixing the primary coating product with the second coating agent to obtain a third mixture;

(6) calcining the third mixture to obtain the quaternary cathode material.
The method according to claim 4, wherein the quaternary cathode material precursor has a composition as shown in formula (II),

Ni a Co b Mn c Al d (OH) 2 (II)

In formula (II), 0.3≤a≤0.92, 0.03≤b≤0.06, 0.01≤c≤0.03, 0.01≤d≤0.03, a+b+c+d=1;

Optionally, the lithium source includes at least one selected from the group consisting of lithium nitrate, lithium carbonate, and lithium hydroxide monohydrate;

Optionally, the dopant includes selected from the group consisting of zirconium hydroxide, zirconium oxide, titanium oxide, magnesium hydroxide, magnesium oxide, magnesium carbonate, magnesium nitrate, barium hydroxide, aluminum oxide, aluminum hydroxide, aluminum hydroxide, At least one of zinc oxide and niobium pentoxide;

Optionally, the first coating agent includes at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, aluminum nitrate, and aluminum oxyhydroxide;

Optionally, the second coating agent includes at least one selected from boric acid, boron oxide, lithium phosphate, and lithium niobate.
The method according to claim 4, wherein in step (1), the molar ratio of the quaternary cathode material precursor to the lithium element in the lithium source is 1: (1.00 to 1.05); The mass ratio of the precursor of the primary cathode material to the doping element in the dopant is 1: (0.001 to 0.003);

Optionally, in step (3), the mass ratio of the core of the quaternary positive electrode material to the coating element in the first coating agent is 1: (0.0005-0.001);

Optionally, in step (5), the mass ratio of the coating elements in the primary coating product and the second coating agent is 1:(0.001-0.01).
The method according to claim 4, wherein the first sintering treatment is completed at 700-820°C for 8-20 hours;

Optionally, the second sintering treatment is completed at 600-700°C for 6-15 hours;

Optionally, the calcination treatment is completed at 300-600°C for 8-18h.
The method according to claim 4, characterized in that, before step (5), it further comprises: washing and drying the primary coated product.
The method according to claim 8, characterized in that, in the water washing treatment, the mass ratio of the primary coated product to water is (1-2):1, and the water washing treatment is performed at a stirring rate of 500-800 rpm Carry on for 30～600s to complete;

Optionally, the drying treatment is completed at 100-180°C for 3-20 hours.
A lithium ion battery, which is characterized by comprising: a positive electrode, a negative electrode, a separator and an electrolyte; wherein,

The positive electrode includes: a positive electrode current collector and a positive electrode material supported on the positive electrode current collector, and the positive electrode material includes: a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; wherein, the positive electrode active material is claimed The quaternary cathode material described in any one of 1 to 3.

The negative electrode includes a negative electrode current collector and a negative electrode material supported on the negative electrode current collector, and the negative electrode material includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.