CN118841551A - Positive electrode material, preparation method thereof, positive electrode plate, secondary battery and power utilization device - Google Patents

Abstract

The present application relates to the field of battery technology, and provides a positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery and an electric device. The positive electrode material includes a material with a chemical formula of Li _{1- a} Ni _x Co _y Mn _z X _a Q _b Z _c O _2-c , wherein 0.80≤x＜0.96, y＞0, z＞0, 0.0005≤a≤0.05, 0.0005≤b≤0.05, 0.0005≤c≤0.05, x+y+z+b＝1, the X element includes at least one of Na and K, the Q element includes at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element includes at least one of F, Cl and S. The present application can improve the cycle stability of the ultra-high nickel single crystal positive electrode material while maintaining the high capacity of the material by co-doping the X element, the Q element and the Z element.

Description

Positive electrode material and preparation method thereof, positive electrode sheet, secondary battery and electric device

Technical Field

The present application relates to the field of battery technology, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet, a secondary battery and an electrical device.

Background Art

High nickel layered oxides have high specific capacity and excellent kinetic properties, making them the preferred cathode materials for the development of high specific energy density (≥300 Wh/Kg) lithium-ion batteries. Among them, single crystal high nickel layered cathode materials have a unique integrated single crystal structure, which eliminates the randomly oriented primary grain boundaries inside the particles, has high mechanical strength and a small specific surface area, and can significantly inhibit particle crack formation and surface/interface side reactions, further alleviating irreversible surface degradation. In addition, the non-porous and integrated structure of the single crystal also makes the single crystal high nickel layered cathode material have high mechanical strength, which can further increase its compaction density, thereby improving energy density. However, the primary particle size of single-crystal high-nickel layered positive electrode materials is large, and the Li ⁺ diffusion path is long, which will lead to uneven lithium concentration distribution during the cycle process. Moreover, with the increase of Ni content and current density in high-nickel positive electrode materials, this trend will be further aggravated, leading to the coexistence of H2 and H3 phases in a single particle. The resulting non-uniform strain and stress will lead to structural defects, limit Li ⁺ diffusion kinetics, and cause rapid capacity decay during long-term cycling, resulting in poor cycle stability of high-nickel single-crystal positive electrode materials.

Summary of the invention

Based on this, the present application provides a positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery and an electrical device. The positive electrode material can improve its cycle stability while maintaining the high capacity of a high-nickel single crystal positive electrode material.

In a first aspect, the present application provides a positive electrode material, comprising a material with a chemical formula of Li1 _{- aNixCoyMnzXaQbZcO2 -c ,} wherein 0.80≤x＜0.96, y＞0, z＞ ₀ , 0.0005≤a≤0.05, 0.0005≤b≤0.05, 0.0005≤c≤0.05, _x +y+z+b＝1, the X element comprises at least one of Na and K, _the Q _{element comprises} at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element comprises at least one of F, Cl and S.

In some embodiments, the Q element includes Al, Zr, and Sr.

Optionally, the molar ratio of Al, Zr and Sr in the Q element is (0.25~0.5):(0.5~1.0):(0.25~0.5).

In some embodiments, the cathode material comprises a single crystal cathode material.

In a second aspect, the present application provides a method for preparing a positive electrode material, the method for preparing a positive electrode material comprising:

Mixing a lithium source, a nickel-cobalt-manganese precursor, a first additive containing an X element, a second additive containing an Q element, and a third additive containing an Z element to obtain a mixed material;

The mixed material is sintered to obtain the positive electrode material, wherein the positive electrode material includes a material with a chemical formula _{of Li1 - aNixCoyMnzXaQbZcO2 -c ,} wherein 0.80≤x＜0.96, y＞0, z＞0, 0.0005≤a≤0.05, 0.0005≤b≤0.05, 0.0005≤c≤0.05, x+y+z+b＝1, the X element includes at least one of Na and K, _{the Q} element includes at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element includes at least one of F, Cl and S.

In some embodiments, the nickel-cobalt-manganese precursor includes a material having a chemical formula of Ni _m Co _n Mn _1-mn (OH) ₂ , wherein 0.80≤m＜0.98, n＞0, and m+n＜1.

In some embodiments, the first additive includes at least one of an oxide containing element X, a carbonate containing element X, a hydroxide containing element X, and an acetate containing element X.

In some embodiments, the second additive includes at least one of an oxide containing the Q element, a carbonate containing the Q element, a hydroxide containing the Q element, and an acetate containing the Q element.

In some embodiments, the third additive containing the Z element includes a salt compound containing the Z element.

In some embodiments, the ratio of the molar number of lithium element in the lithium source to the molar number of the nickel-cobalt-manganese precursor is (1.01-1.06):1.

In some embodiments, the ratio of the molar number of the X element in the first additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1.

In some embodiments, the ratio of the molar number of the Q element in the second additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1.

In some embodiments, the ratio of the molar number of the Z element in the third additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1.

In some embodiments, the sintering process includes: sequentially performing a first sintering and a second sintering on the mixed material.

Optionally, the first sintering is performed at a temperature of 450° C. to 650° C., for a time of 2 h to 10 h, in an oxygen-containing atmosphere.

Optionally, the second sintering is performed at a temperature of 650° C. to 900° C., for a time of 10 h to 20 h, in an oxygen-containing atmosphere.

In a third aspect, the present application provides a positive electrode plate, comprising at least one of the positive electrode material as described in the first aspect and the positive electrode material prepared by the preparation method as described in the second aspect.

In a fourth aspect, the present application provides a secondary battery, comprising the positive electrode plate as described in the third aspect.

In a fifth aspect, the present application provides an electrical device comprising the secondary battery as described in the fourth aspect.

Compared with the traditional technology, this application has at least the following beneficial effects:

This application utilizes X element, Q element and Z element co-doping, wherein X element occupies Li position after bulk phase doping, Q element occupies transition metal position after bulk phase doping, and Z element occupies O position after bulk phase doping, and a stable doping structure is formed by synergistic doping at different sites. It not only increases the lithium interlayer spacing of high nickel positive electrode materials, helps lithium deintercalation and weakens Li ⁺ /Ni ²⁺ mixing and phase transition, but also reduces the interaction force between the lithium layer and the oxygen layer, increases the spacing between the lithium layer and the oxygen layer, accelerates the transmission of Li ⁺ , and ultimately improves its cycle stability while maintaining the high capacity of high nickel single crystal positive electrode materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of the positive electrode material prepared in Example 1 of the present application;

FIG2 is a SEM image of the positive electrode material prepared in Comparative Example 1 of the present application;

FIG3 is a comparison chart of the cycle retention rates of Example 1 and Comparative Example 1 of the present application.

DETAILED DESCRIPTION

Below in conjunction with the embodiments and examples, the present application is further described in detail. These embodiments and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms, and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent form obtained also falls within the protection scope of the present application. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

In this application, the terms "first", "second", etc. in "the first aspect", "the second aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the application purpose and/or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

In traditional technology, "high nickel" means that the molar content of Ni in the single crystal lithium nickel cobalt manganese oxide matrix accounts for more than 80% of the total molar amount of Ni, Co and Mn. The material is doped with a dopant that is close to the radius of the transition metal ions in the high nickel ternary positive electrode material, such as Al. Although it can stabilize the crystal structure of lithium ions during the deintercalation process and reduce the stress changes of the material during the charge and discharge process, it can improve the cycle stability of the high nickel ternary positive electrode material. However, most of these doping elements are electrochemically inert, which will cause the capacity performance of the high nickel ternary positive electrode material to decrease.

In a first aspect, the present application provides a positive _electrode material, comprising a material with a chemical formula of Li1 _{- aNixCoyMnzXaQbZcO2 -c ,} wherein 0.80≤x＜0.96, y＞0, z＞ ₀ , 0.0005≤a≤0.05, 0.0005≤b≤0.05 _, 0.0005≤c≤0.05, x+y+z+b＝1, the X element comprises at least one of Na and K, the Q _{element comprises} at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element comprises at least one of F, Cl and S.

This application utilizes X element, Q element and Z element co-doping, wherein X element occupies Li position after bulk phase doping, Q element occupies transition metal position after bulk phase doping, and Z element occupies O position after bulk phase doping, and a stable doping structure is formed by synergistic doping at different sites. It not only increases the lithium interlayer spacing of high nickel positive electrode materials, helps lithium deintercalation and weakens Li ⁺ /Ni ²⁺ mixing and phase transition, but also reduces the interaction force between the lithium layer and the oxygen layer, increases the spacing between the lithium layer and the oxygen layer, accelerates the transmission of Li ⁺ , and ultimately improves its cycle stability while maintaining the high capacity of high nickel single crystal positive electrode materials.

Specifically, the atomic radius of the X element is larger than that of Li. When it is doped into the lithium layer of the ternary layered cathode material, it can play the role of a "pillar", inhibiting the collapse of the layered structure during deep lithium removal (high voltage), so the lithium-sodium composite material has good structural stability. At the same time, because the X element has a larger ionic radius, it can increase the distance between lithium layers, which is helpful for lithium deintercalation and improves the lithium diffusion coefficient and rate performance of the material. In addition, the huge electron cloud formed by the more extranuclear electrons of the X element can effectively inhibit the migration of transition metals through electrostatic repulsion and magnetic interaction, thereby weakening the Li ⁺ /Ni ²⁺ mixing and phase transition, which has a significant improvement effect on improving the capacity and rate performance of the ternary layered cathode material. Furthermore, the synergistic cooperation between the X element, the Q element and the Z element enhances the inter-ionic force and bond energy of the cathode material, inhibits the surface reconstruction during the cycle process, and can take into account the dual functionality of doping and surface coating, which can not only stabilize the bulk structure of the material, but also reduce the interaction between the lithium layer and the oxygen layer to increase the distance between the lithium layer and the oxygen layer, accelerate the transmission of Li ⁺ , and significantly improve the high-voltage performance of the cathode material. The present application can achieve a good synergistic improvement effect through the joint effect of anions and cations, and the anion and cation doping at different sites can exert a synergistic effect, which plays a positive role in the chemical and structural stability of high-nickel ternary single crystal materials.

Wherein, x includes but is not limited to: 0.80, 0.82, 0.85, 0.90, 0.93 or 0.95. y includes but is not limited to 0.005, 0.010, 0.015, 0.020, 0.025, 0.030 or 0.035. z includes but is not limited to 0.005, 0.010, 0.015, 0.020, 0.025, 0.030 or 0.035. a includes, but is not limited to, 0.0005, 0.0010, 0.0015, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, or 0.050. b includes, but is not limited to, 0.0005, 0.0010, 0.0015, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, or 0.050. c includes, but is not limited to, 0.0005, 0.0010, 0.0015, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, or 0.050.

In some embodiments, the Q element includes Al, Zr, and Sr.

Optionally, the molar ratio of Al, Zr and Sr in the Q element is (0.25~0.5):(0.5~1.0):(0.25~0.5), including but not limited to 0.25:0.5:0.25, 0.3:0.6:0.4, 0.4:0.6:0.5, 0.5:0.5:0.5, 0.4:1.0:0.5 or 0.3:0.8:0.4.

The Q element is selected as above in the present application, which can ensure the stability of the crystal structure of lithium ions during the insertion and extraction process, and can reduce the stress changes of the material during the charging and discharging process, so as to improve the cycle stability of the high-nickel ternary positive electrode material. Furthermore, it cooperates well with the X element and the Z element, and can effectively avoid the problem of decreased capacity performance of the high-nickel ternary positive electrode material caused by electrochemical inertness.

In some embodiments, the volume average particle size Dv50 of the positive electrode material is 2 μm to 4 μm, for example, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm or 4.0 μm. The volume average particle size Dv50 can be tested using a particle size tester.

In some embodiments, the specific surface area of the positive electrode material is 0.5 ^m 2 /g to 1.5 m ² /g, for example, 0.5 ^m 2 /g, 0.6 m ² /g, 0.7 m ² /g, 0.8 m ² /g, 0.9 m ² /g, 1.0 m ² /g, 1.1 m ² /g, 1.2 m ² /g, 1.3 m ² /g, 1.4 m ² /g or 1.5 m ² /g. The specific surface area can be tested using the BET method.

In the present application, after the positive electrode material is co-doped with X element, Q element and Z element, the size of the positive electrode material is similar to that of the undoped high-nickel ternary positive electrode material, and it not only has a higher discharge specific capacity, but also has excellent cycle stability.

In some embodiments, the positive electrode material comprises a single crystal positive electrode material. The positive electrode material of the present application has a single crystal structure, and has the advantages of eliminated primary grain boundaries, consistent and continuous lattice orientation, orderly crystal plane arrangement and low specific surface area.

In some embodiments, the mass proportion of Li ₂ CO ₃ in the positive electrode material is ≤0.15%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%. It can be selected from 0.05% to 0.15%.

In some embodiments, the mass proportion of LiOH in the positive electrode material is ≤0.40%, for example, it can be 0.04%, 0.08%, 0.12%, 0.16%, 0.20%, 0.24%, 0.28%, 0.32%, 0.36% or 0.40%. It can be selected from 0.20% to 0.40%.

The positive electrode material in the present application has low residual lithium content on the surface, excellent processing performance, good safety and low interface impedance, and effectively avoids problems such as slurry gelation, gas production and local overheating.

A second aspect of the present application provides a method for preparing a positive electrode material, the method for preparing a positive electrode material comprising:

Mixing a lithium source, a nickel-cobalt-manganese precursor, a first additive containing an X element, a second additive containing an Q element, and a third additive containing an Z element to obtain a mixed material;

The mixed material is sintered to obtain the positive electrode material, wherein the positive electrode material includes a material with a chemical formula _{of Li1 - aNixCoyMnzXaQbZcO2 -c ,} wherein 0.80≤x＜0.96, y＞0, z＞0, 0.0005≤a≤0.05, 0.0005≤b≤0.05, 0.0005≤c≤0.05, x+y+z+b＝1, the X element includes at least one of Na and K, _{the Q} element includes at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element includes at least one of F, Cl and S.

The present application prepares the positive electrode material as above, and adopts the solid phase method to dope the X element, Q element and Z element at different sites in the bulk phase. The preparation method is simple in process, the improvement effect is outstanding, the cost of raw materials is low, and it is suitable for large-scale industrial production. Among them, the X element occupies the Li position after bulk phase doping, the Q element occupies the transition metal position after bulk phase doping, and the Z element occupies the O position after bulk phase doping, and a stable doping structure is formed by synergistic doping at different sites. Not only does it increase the lithium interlayer spacing of the high-nickel positive electrode material, it helps to deintercalate lithium and weaken the Li ⁺ /Ni ²⁺ mixing and phase transition, but it also reduces the interaction force between the lithium layer and the oxygen layer, increases the spacing between the lithium layer and the oxygen layer, and accelerates the transmission of Li ⁺ , and finally improves its cycle stability while maintaining the high capacity of the high-nickel single crystal positive electrode material.

In some embodiments, the nickel-cobalt-manganese precursor includes a material with a chemical formula of Ni _m Co _n Mn _1-mn (OH) ₂ , wherein 0.80≤m＜0.98, n＞0, and m+n＜1. Wherein, m includes but is not limited to: 0.80, 0.83, 0.85, 0.90, 0.92, 0.95, 0.96 or 0.97. n includes but is not limited to: 0.002, 0.004, 0.006, 0.008, 0.010, 0.012, 0.014, 0.016, 0.018 or 0.020.

In some embodiments, the first additive includes at least one of an oxide containing element X, a carbonate containing element X, a hydroxide containing element X, and an acetate containing element X. For example, if element X is Na, the first additive may be NaOH.

In some embodiments, the second additive includes at least one of an oxide containing the Q element, a carbonate containing the Q element, a hydroxide containing the Q element, and an acetate containing the Q element. For example, if the Q element is Zr, the second additive may be ZrO ₂ . If the Q element is Sr, the second additive may be SrCO ₃ .

In some embodiments, the third additive containing the element Z includes a salt compound containing the element Z. For example, the element Z is F, and the third additive may be at least one of NH ₄ F and LiF.

In some embodiments, the ratio of the molar number of lithium element in the lithium source to the molar number of the nickel-cobalt-manganese precursor is (1.01-1.06):1, for example, it can be 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1 or 1.06:1.

In some embodiments, the ratio of the molar number of the X element in the first additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1, for example, it can be 0.001:1, 0.005:1, 0.010:1, 0.020:1, 0.030:1, 0.040:1, 0.050:1, 0.060:1, 0.070:1, 0.080:1, 0.090:1 or 0.100:1.

In some embodiments, the ratio of the molar number of the Q element in the second additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1, for example, it can be 0.001:1, 0.005:1, 0.010:1, 0.020:1, 0.030:1, 0.040:1, 0.050:1, 0.060:1, 0.070:1, 0.080:1, 0.090:1 or 0.100:1.

In some embodiments, the ratio of the molar number of the Z element in the third additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1, for example, it can be 0.001:1, 0.005:1, 0.010:1, 0.020:1, 0.030:1, 0.040:1, 0.050:1, 0.060:1, 0.070:1, 0.080:1, 0.090:1 or 0.100:1.

In some embodiments, the sintering process includes: sequentially performing a first sintering and a second sintering on the mixed material.

Optionally, the first sintering temperature is 450° C. to 650° C., for example, 450° C., 460° C., 480° C., 500° C., 520° C., 540° C., 560° C., 580° C., 600° C. or 650° C. The first sintering temperature selected in the present application has good lithiation reaction activity and effectively avoids problems such as lithium salt segregation and insufficient lithiation reaction.

Optionally, the first sintering time is 2 h to 10 h, for example, it can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h.

Optionally, the first sintering atmosphere is an oxygen-containing atmosphere. Optionally, the oxygen volume concentration in the oxygen-containing atmosphere is ≥97%.

Optionally, the second sintering temperature is 650°C to 900°C, for example, 650°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C or 900°C. The second sintering temperature selected in the present application as above can make the positive electrode material have higher crystallinity and good lattice order, and can avoid the problems of rock salt phase formation caused by severe cation mixing and decreased lattice order.

Optionally, the second sintering time is 10 h to 20 h, for example, it can be 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h.

Optionally, the second sintering atmosphere is an oxygen-containing atmosphere. Optionally, the volume concentration of oxygen in the oxygen-containing atmosphere is ≥97%.

In some embodiments, after the sintering process, the positive electrode material is subjected to cooling, crushing and screening. Optionally, the crushing process includes rolling crushing and ultracentrifugal grinding crushing performed in sequence. Optionally, the mesh number of the screening process is 200 mesh to 300 mesh.

Exemplarily, a method for preparing the above-mentioned positive electrode material is provided, comprising the following steps:

S1. Mix a nickel-cobalt-manganese precursor, a lithium source, a first additive containing an X element, a second additive containing an Q element, and a third additive containing an Z element in a molar ratio of 1: (1.01-1.06): (0.001-0.1): (0.001-0.1): (0.001-0.1) to obtain a mixed material, wherein the nickel-cobalt-manganese precursor includes a material with a chemical formula of Ni _m Co _n Mn _1-mn (OH) ₂ , wherein 0.80≤m＜0.98, n＞0, and m+n＜1;

S2. The mixed material in step S1 is first sintered at 450°C-650°C for 2h-10h in an oxygen-containing atmosphere; then sintered at 650°C-900°C for 10h-20h in an oxygen-containing atmosphere, and after cooling in the furnace, crushed and sieved to obtain the positive electrode material.

A third aspect of the present application provides a positive electrode plate, comprising at least one of the positive electrode material as described in the first aspect and the positive electrode material prepared by the preparation method as described in the second aspect.

The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder. The positive electrode active material comprises at least one of the positive electrode material or the positive electrode material prepared by the preparation method, and the conductive agent and the binder may be conductive agents and binders commonly used in the technical field.

A fourth aspect of the present application provides a secondary battery, comprising the positive electrode sheet as described in the third aspect.

The above-mentioned secondary battery may, for example, include the above-mentioned positive electrode sheet, negative electrode sheet, electrolyte and diaphragm of the present application. The diaphragm is arranged between the positive electrode sheet and the negative electrode sheet, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet. During the charging and discharging process of the secondary battery, the active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The present application has no special restrictions on the negative electrode sheet, electrolyte and diaphragm, and the negative electrode sheet, electrolyte and diaphragm prepared by the preparation method commonly used in the technical field, or the negative electrode sheet, electrolyte and diaphragm commonly used in the art can be used. Optionally, the above-mentioned secondary battery includes a lithium-ion battery.

The fifth aspect of the present application also provides an electrical device, comprising the secondary battery as described in the fourth aspect.

The above-mentioned electrical devices may include any equipment or devices that use secondary batteries as driving sources, such as mobile phones, laptop computers, electric vehicles, ships, satellites, energy storage devices, smart home appliances, etc., but are not limited thereto.

In order to further illustrate the present application, the technical scheme of the present application is described in detail below in conjunction with specific examples. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in the field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

Example 1

S1. Weigh raw materials according to the molar ratio of Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ : NH ₄ F = 1: 1.04: 0.001: 0.005: 0.005: 0.0025: 0.001, mix the above raw materials in an air flow mixer, the speed of the air flow mixer is 1200 rpm, the mixing time is 40 minutes, and the mixed material is obtained after being fully mixed;

S2. The mixed material is transferred to a box furnace for sintering in an oxygen atmosphere. First, the temperature is increased to 630°C at a heating rate of 2.5°C/min for the first sintering for 6 hours, and then the temperature is increased to 780°C at a heating rate of 2.5°C/min for the second sintering for 16 hours. The oxygen content in the sintering atmosphere is 99 vol%. As the furnace is cooled, the obtained material is successively subjected to jaw crushing, roller crushing, air flow crushing and 325 mesh sieving. As shown in FIG1 , a single crystal positive electrode material with a chemical formula of Li _0.999 Na _0.001 Ni _0.945 Co _0.03 Mn _0.01 Zr _0.005 Sr _0.005 Al _0.005 F _0.001 O _1.999 is obtained. The volume average particle size Dv50 is 2.6 μm, the specific surface area is 1.1 m ² /g, and the Li ₂ CO in the positive electrode material is 1.24 W/cm2. The mass proportion of ₃ is 0.1%, and the mass proportion of LiOH is 0.3%.

Example 2

A positive electrode material was prepared according to the method of Example 1, with the only difference that the raw material composition and molar ratio in step S1 were: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: KOH: ZrO ₂ : Sb ₂ O ₃ : LiF = 1: 1.04: 0.001: 0.005: 0.005: 0.001; and the second sintering temperature in step S2 was 785° C. to obtain a positive electrode material with a chemical formula of Li _0.999 K _0.001 Ni _0.945 Co _0.03 Mn _0.01 Zr _0.005 Sb _0.01 F _0.001 O _1.999 .

Example 3

A positive electrode material was prepared according to the method of Example 1, with the only difference that the raw material composition and molar ratio in step S1 were: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : NH ₄ Cl = 1: 1.04: 0.01: 0.02: 0.01; and the second sintering temperature in step S2 was 790° C. to obtain a positive electrode material with a chemical formula of Li _0.99 Na _0.01 Ni _0.94 Co _0.03 Mn _0.01 Zr _{0.0 2} Cl _0.01 O _1.99 .

Example 4

A positive electrode material was prepared according to the method of Example 1, with the only difference that the raw material composition and molar ratio in step S1 were: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: KOH: ZrO ₂ : SrCO ₃ : NH ₄ F = 1: 1.04: 0.0005: 0.0005: 0.005: 0.005: 0.001, and a positive electrode material was prepared with a chemical formula of Li _0.999 Na _0.0005 K _0.0005 Ni _0.95 Co _0.03 Mn _0.01 Zr _0.005 Sr _0.005 F _0.001 O _1.999 .

Example 5

A positive electrode material was prepared according to the method of Example 1, with the only difference that the raw material composition and molar ratio in step S1 were: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : NH ₄ F: NH ₄ Cl = 1: 1.04: 0.001: 0.005: 0.005: 0.0005: 0.0005, to obtain a positive electrode material with a chemical formula of Li _0.999 Na _0.001 Ni _0.95 Co _0.03 Mn _0.01 Zr _0.005 Sr _0.005 F _0.0005 Cl _0.0005 O _1.999 .

Example 6

A positive electrode material is prepared according to the method of Example 1, with the only difference that in step S1, the raw material composition and molar ratio are: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: KOH: ZrO ₂ : Nb ₂ O ₅ : NH ₄ F: NH ₄ Cl＝1: 1.04: 0.0005: 0.0005: 0.0005: 0.005: 0.0005: 0.0005, and a positive electrode material is prepared with a chemical formula of Li _0.999 Na _0.0005 K _0.0005 Ni _0.945 Co _0.03 Mn _0.01 Zr _0.005 Nb _0.01 F _0.0005 Cl _0.0005 O _1.999 .

Example 7

The positive electrode material was prepared according to the method of Example 1, except that the temperature of the first sintering in step S2 was 400°C.

Example 8

The positive electrode material was prepared according to the method of Example 1, except that the temperature of the first sintering in step S2 was 680°C.

Example 9

The positive electrode material was prepared according to the method of Example 1, except that the temperature of the second sintering in step S2 was 640°C.

Example 10

The positive electrode material was prepared according to the method of Example 1, except that the temperature of the second sintering in step S2 was 950°C.

Embodiment 11

The positive electrode material was prepared according to the method of Example 1, with the only difference being that the molar ratio of Al, Zr and Sr elements was changed. The raw materials were weighed according to the molar ratio: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ : NH ₄ F=1: 1.04: 0.001: 0.005: 0.005: 0.01: 0.001, and the chemical formula was Li _0.999 Na _0.001 Ni _0.93 Co _0.03 Mn _0.01 Zr _0.005 Sr _{0.00 5} Al _0.02 F _0.001 O _1.999 .

Example 12

The positive electrode material was prepared according to the method of Example 1, with the only difference being that the molar ratio of Al, Zr and Sr elements was changed. The raw materials were weighed according to the molar ratio: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ : NH ₄ F = 1: 1.04: 0.001: 0.01: 0.005: 0.005: 0.001, and the chemical formula was Li _0.999 Na _0.001 Ni _0.935 Co _0.03 Mn _0.01 Zr _0.01 Sr _{0.00 5} Al _0.01 F _0.001 O _1.999 .

Example 13

The positive electrode material was prepared according to the method of Example 1, with the only difference being that the molar ratio of Al, Zr and Sr elements was changed. The raw materials were weighed according to the molar ratio: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ : NH ₄ F=1: 1.04: 0.001: 0.005: 0.01: 0.005: 0.001, and the chemical formula was Li _0.999 Na _0.001 Ni _0.935 Co _0.03 Mn _0.01 Zr _0.005 Sr _{0.01 Al 0.01} F _0.001 O _1.999 .

Comparative Example 1

S1. Weigh the raw materials according to the molar ratio of Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O = 1:1.04, mix the raw materials in an air flow mixer, the speed of the air flow mixer is 1200 rpm, the mixing time is 40 minutes, and obtain a mixed material after sufficient mixing;

S2. The mixed material is transferred to an atmosphere furnace for sintering treatment in a sintering atmosphere. First, the temperature is increased to 630°C at a heating rate of 2.5°C/min, and the first sintering is performed for 6 hours. Then, the temperature is increased to 775°C at a heating rate of 2.5°C/min, and the second sintering is performed for 16 hours. The oxygen content in the sintering atmosphere is 99 vol%. As the furnace is cooled, the obtained material is successively subjected to roller crushing, air flow crushing, ultracentrifugal grinding and crushing, and 325 mesh sieving to obtain the positive electrode material as shown in Figure 2.

Comparative Example 2

The positive electrode material was prepared according to the method of Example 1, except that the raw material in step S1 did not include NaOH, that is, the raw material composition was: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O : ZrO ₂ : SrCO ₃ : Al ₂ O ₃ : NH ₄ F = 1: 1.04: 0.005: 0.005: 0.005: 0.001.

Comparative Example 3

The positive electrode material was prepared according to the method of Example 1, except that the raw material in step S1 did not include NH ₄ F, that is, the raw material composition was: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ = 1: 1.04: 0.001: 0.005: 0.005: 0.005.

Comparative Example 4

The positive electrode material was prepared according to the method of Example 1, except that the raw material in step S1 did not include NH ₄ F, ZrO ₂ , SrCO ₃ and Al ₂ O ₃ , that is, the raw material composition was: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NaOH=1:1.04:0.001.

Comparative Example 5

The positive electrode material was prepared according to the method of Example 1, except that the raw material in step S1 did not include NH ₄ F and NaOH, that is, the raw material composition was: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: ZrO ₂ : SrCO ₃ : Al ₂ O ₃ = 1: 1.04: 0.005: 0.005: 0.005.

Comparative Example 6

The positive electrode material was prepared according to the method of Example 1, except that the raw material in step S1 did not include ZrO ₂ , SrCO ₃ , Al ₂ O ₃ and NaOH, that is, the raw material composition was: Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ : LiOH·H ₂ O: NH ₄ F = 1: 1.04: 0.001.

The components of the positive electrode materials prepared in each embodiment and each comparative example were measured using an ICP-AES (inductively coupled plasma atomic emission spectrometer).

The positive electrode materials prepared in the above embodiments and comparative examples are used to assemble button-type lithium-ion half-cells, comprising:

The positive electrode materials prepared in each embodiment and comparative example were made into positive electrode sheets, and the positive electrode sheets were prepared according to the mass ratio of positive electrode material: conductive agent super carbon black: PVDF (polyvinylidene fluoride) = 96.5:2:1.5. The above positive electrode sheets were assembled into button batteries of model LR2032, and then the capacity performance and cycle performance were tested.

The capacity performance test adopts constant current and constant voltage charge and discharge mode, and the charge and discharge times are first 0.1C and then 1/3C. The cycle performance test adopts 45°C and 0.5C rate for charge and discharge cycle test. The charge and discharge voltage range of the capacity performance test and the cycle performance test are both set to 2.5~4.3V. The test results are shown in Table 1, among which the cycle retention rate comparison chart of Example 1 and Comparative Example 1 is shown in Figure 3.

Table 1

From the above table we can see that:

(1) Compared with Examples 4-6, Example 1 of the present application shows that the Q element of the present application uses Al, Zr and Sr, the bulk crystal structure is stable, and the cycle stability is improved.

(2) Compared with Examples 7-10, it can be seen that the present application controls the temperature during the sintering process, and the positive electrode material prepared has low residual alkali, high crystallinity, good ion mixing degree and high capacity, which can avoid the risk of gas production caused by residual alkali and the capacity reduction problem caused by excessive primary particle size.

(3) By comparing Example 1 of the present application with Examples 11-13, it can be seen that controlling the ratio of Al, Zr and Sr in the present application can improve the capacity of the positive electrode material.

(4) Example 1 of the present application is compared with Comparative Examples 1-6, in combination with Figures 1, 2 and 3. Among them, it can be seen from Figures 1 and 2 that the sample prepared in Example 1 is a single crystal sample, and the size of its primary particles is about 1.3μm. The positive electrode material prepared in Example 1 has no obvious change in microscopic morphology from the positive electrode material prepared in Comparative Example 1. In addition, due to agglomeration between the primary particles, the volume average particle size Dv50 of the positive electrode material prepared in Example 1 is 2.5μm. Further, as shown in Figure 3, the positive electrode material of Example 1 of the present application significantly improves the cycle stability compared with the positive electrode material of Comparative Example 1. Specifically, Comparative Example 4 only uses X element doping. Although it has a higher capacity, it has a poor stability of the bulk crystal structure, which leads to a decrease in cycle stability. Comparative Example 5 only uses Q element doping. Although it has good cycle stability, it lacks lithium site doping, resulting in a lower interlayer spacing and a decrease in capacity. Comparative Example 6 uses only anion doping, which will cause the Li ⁺ /Ni ²⁺ mixing in the positive electrode material to intensify, resulting in unstable long cycle performance. Further, compared with Example 1 of the present application and Comparative Examples 1-6, it can be seen that the joint effect of the X element, Q element and Z element in the present application can well play a synergistic improvement effect, and the anion and cation doping at different sites can play a synergistic effect, which plays a positive role in the chemical and structural stability of the ultra-high nickel ternary single crystal material.

In summary, the present application utilizes X element, Q element and Z element co-doping, wherein X element occupies Li position after bulk phase doping, Q element occupies transition metal position after bulk phase doping, and Z element occupies O position after bulk phase doping, and a stable doping structure is formed by synergistic doping at different sites. It not only increases the lithium interlayer spacing of the ultra-high nickel positive electrode material, helps lithium deintercalation and weakens Li ⁺ /Ni ²⁺ mixing and phase transition, but also reduces the interaction force between the lithium layer and the oxygen layer, increases the spacing between the lithium layer and the oxygen layer, accelerates the transmission of Li ⁺ , and ultimately improves its cycle stability while maintaining the high capacity of the ultra-high nickel single crystal positive electrode material.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the application. It should be noted that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims (10)

1. A positive electrode material, characterized in that the positive _electrode material comprises a material with a chemical formula of Li1 _{- aNixCoyMnzXaQbZcO2 - c} , wherein 0.80≤x＜0.96, y＞0, z＞0, 0.0005≤a≤0.05 _, 0.0005≤b≤0.05, 0.0005≤c≤0.05, x+y+z+b＝1, the X element comprises at least one of Na and _K , the Q element _comprises at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element comprises at least one of F, Cl and S. 2. The positive electrode material according to claim 1, characterized in that the Q element comprises Al, Zr and Sr; Optionally, the molar ratio of Al, Zr and Sr in the Q element is (0.25~0.5):(0.5~1.0):(0.25~0.5). 3. The positive electrode material according to claim 1, characterized in that the positive electrode material comprises a single crystal positive electrode material. 4. A method for preparing a positive electrode material, characterized in that the method for preparing the positive electrode material comprises: Mixing a lithium source, a nickel-cobalt-manganese precursor, a first additive containing an X element, a second additive containing an Q element, and a third additive containing an Z element to obtain a mixed material; The mixed material is sintered to obtain the positive electrode material, wherein the positive electrode material includes a material with a chemical formula of _{Li1 - aNixCoyMnzXaQbZcO2 -c ,} wherein 0.80≤x _＜ 0.96, y＞0, z＞0, 0.0005≤a≤0.05, 0.0005≤b≤0.05, 0.0005≤c≤0.05, x+y+z+b＝1, the X element includes at least one of Na and _K , _{the Q} element includes at least one of Al, Zr, Sr, Sn, Sb, Si, Ba, Y, W, Mo, Nb, La, Ta and Ce, and the Z element includes at least one of F, Cl and S. 5. The method for preparing a positive electrode material according to claim 4, wherein the method for preparing a positive electrode material satisfies at least one of the following conditions: (1) The nickel-cobalt-manganese precursor comprises a material having a chemical formula of Ni _m Co _n Mn _1-mn (OH) ₂ , wherein 0.80≤m＜0.98, n＞0, and m+n＜1; (2) the first additive includes at least one of an oxide containing element X, a carbonate containing element X, a hydroxide containing element X, and an acetate containing element X; (3) the second additive includes at least one of an oxide containing the Q element, a carbonate containing the Q element, a hydroxide containing the Q element, and an acetate containing the Q element; (4) The third additive includes a salt compound containing the Z element. 6. The method for preparing a positive electrode material according to claim 4, characterized in that the method for preparing a positive electrode material further satisfies at least one of the following conditions: (1) The ratio of the molar number of lithium element in the lithium source to the molar number of the nickel-cobalt-manganese precursor is (1.01-1.06):1; (2) The ratio of the molar number of the X element in the first additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1; (3) The ratio of the molar number of the Q element in the second additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1; (4) The ratio of the molar number of the Z element in the third additive to the molar number of the nickel-cobalt-manganese precursor is (0.001-0.1):1. 7. The method for preparing a positive electrode material according to any one of claims 4 to 6, characterized in that the sintering treatment comprises: sequentially performing a first sintering and a second sintering on the mixed material; Optionally, the first sintering is performed at a temperature of 450° C. to 650° C., for a time of 2 h to 10 h, in an oxygen-containing atmosphere; Optionally, the second sintering is performed at a temperature of 650° C. to 900° C., for a time of 10 h to 20 h, in an oxygen-containing atmosphere. 8. A positive electrode sheet, characterized in that it comprises at least one of the positive electrode material according to any one of claims 1 to 3 and the positive electrode material prepared by the preparation method according to any one of claims 4 to 7. 9. A secondary battery, comprising the positive electrode sheet according to claim 8. 10. An electrical device, comprising the secondary battery according to claim 9.