Single-crystal ternary positive electrode active material and preparation method and application thereof

Abstract

This application relates to the field of battery materials technology, and discloses a single-crystal ternary cathode active material, its preparation method, and its application. The chemical formula of the single-crystal ternary cathode active material is LiNi. a Co b Mn c X d Y e O2 and element X promote the growth of the (003) crystal plane, element Y promotes the growth of the (104) crystal plane, 0.5≤a<1, 0≤b≤0.2, 0≤c≤0.3, 0

Description

Technical Field

[0001] This application relates to the technical field of battery materials, and particularly to a single-crystal ternary cathode active material, its preparation method and application. Background Art

[0002] With the rapid development of the lithium-ion battery industry, the market demand for lithium-ion batteries with high energy density is increasing day by day. Ternary lithium batteries have attracted much attention in fields such as electric vehicles due to their high energy density.

[0003] The most crucial part of a ternary lithium battery is the ternary cathode active material, which directly affects the energy density, charge-discharge performance and safety of the battery. For ternary cathode active materials, there are mainly two ways to improve the energy density at present. One is to increase the specific capacity of the material, that is, to develop in the direction of high nickel by increasing the nickel content; the other is to increase the material voltage and make the material develop in the direction of single crystallization. However, in the crystal growth process of single-crystal ternary cathode active materials, there are problems such as inconsistent crystal plane growth directions and different crystal growth rates, which ultimately lead to deterioration of the battery's compaction, gas generation, long cycle performance, etc. Summary of the Invention

[0004] In view of this, this application provides a single-crystal ternary cathode active material with high particle roundness and uniform size, aiming to solve at least one of the above problems to a certain extent.

[0005] According to an embodiment of the present application, in a first aspect, a single-crystal ternary cathode active material is provided. The chemical general formula of the single-crystal ternary cathode active material is LiNi a Co b Mn c X d Y e O2, where the X element has the effect of promoting the growth tendency of the (003) crystal plane, the Y element has the effect of promoting the growth tendency of the (104) crystal plane, 0.5 ≤ a < 1, 0 ≤ b ≤ 0.2, 0 ≤ c ≤ 0.3, 0 < d ≤ 0.0012, 0 < e ≤ 0.0012, a + b + c + d + e = 1 and 0.2 ≤ d / e ≤ 4.

[0006] In some optional embodiments, the X element is selected from at least one of Sr, Zr, Ce, and Bi.

[0007] In some optional embodiments, the Y element is selected from at least one of Sb, Ta, W, and Nb.

[0008] In some optional embodiments, the particle roundness of the single-crystal ternary cathode active material is 0.8 - 1.0.

[0009] In some alternative embodiments, the particle size distribution of the single-crystal ternary cathode active material is Span ≤ 1.2.

[0010] According to embodiments of this application, in a second aspect, a method for preparing the single-crystal ternary cathode active material described in the first aspect is provided, comprising the following steps:

[0011] After uniformly mixing the nickel-cobalt-manganese hydroxide precursor with lithium salt, X source, and Y source, sintering is carried out in an oxygen-containing environment to obtain a single-crystal ternary cathode active material.

[0012] In some alternative embodiments, the X source includes at least one of an oxide, hydroxide, or carbonate of element X.

[0013] In some alternative embodiments, the Y source includes at least one of the following: an oxide, hydroxide, carbonate, or oxyacid of element Y.

[0014] In some alternative embodiments, the lithium salt includes at least one of lithium carbonate and lithium hydroxide.

[0015] In some optional embodiments, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn (1-x-y) (OH)2, 0.5≤x<1, 0≤y≤0.2.

[0016] In some optional embodiments, the median particle size D50 of the nickel-cobalt-manganese hydroxide precursor is 2 μm-5 μm.

[0017] In some optional embodiments, the heating rate of the sintering process is 5℃ / min-15℃ / min, the sintering temperature in the isothermal section is 750℃-980℃, and the sintering time in the isothermal section is 6h-15h.

[0018] According to an embodiment of this application, in a third aspect, a positive electrode sheet is provided, comprising:

[0019] A positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive active material layer includes the single-crystal ternary positive active material described in the first aspect of this application or the single-crystal ternary positive active material prepared by the preparation method described in the second aspect of this application.

[0020] In some alternative embodiments, the compaction density of the positive electrode sheet is 3.50 g / cm³. 3 -3.62g / cm 3 .

[0021] According to an embodiment of the present application, in a fourth aspect, a secondary battery is provided, including the positive electrode sheet described in the third aspect of the present application.

[0022] According to an embodiment of the present application, in a fifth aspect, an electrical device is provided, including the secondary battery described in the fourth aspect of the present application.

[0023] The technical solution of the present application has the following advantages:

[0024] The chemical general formula of the single-crystal ternary positive electrode active material provided by the present application is LiNi a Co b Mn c X d Y e O2, where the X element has the effect of promoting the growth tendency of the (003) crystal plane, the Y element has the effect of promoting the growth tendency of the (104) crystal plane, 0.5 ≤ a < 1, 0 ≤ b ≤ 0.2, 0 ≤ c ≤ 0.3, 0 < d ≤ 0.001, 0 < e ≤ 0.001, a + b + c + d + e = 1 and 0.2 ≤ d / e ≤ 4. By doping appropriate amounts of X and Y elements that can promote the growth tendencies of the (003) and (104) crystal planes of the ternary positive electrode active material and controlling the stoichiometric ratio of the X and Y elements within the range of 0.2 - 4, the directional synthesis of the crystal plane orientation and material morphology can be achieved, thereby preparing a single-crystal ternary positive electrode active material with high particle roundness and uniform size. Furthermore, the compaction density of the electrode sheet can be increased, making the secondary battery have the advantages of low gas generation and good cycling performance.

[0025] The additional aspects and advantages of the embodiments of the present application will be partially described and shown in the following description, or will be explained through the implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. [[ID=二十八]]

[0027] Figure 1 SEM image of the single-crystal ternary positive electrode active material prepared in Example 6 of the present application.

[0028] Figure 2 SEM image of the single-crystal ternary positive electrode active material prepared in Comparative Example 1 of the present application.

[0029] Figure 3 SEM image of the single-crystal ternary positive electrode active material prepared in Comparative Example 2 of the present application.

[0030] Figure 4 This is a SEM image of the single-crystal ternary cathode active material prepared in Comparative Example 3 of this application. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0033] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0037] It should be noted that, compared with polycrystalline materials, monocrystalline ternary cathode active materials have higher structural stability and thermal stability, which can improve the cycle performance and safety performance of batteries to a certain extent. However, this study found that during the sintering process of monocrystalline ternary cathode active materials, the surface energies of the (003) and (104) crystal plane orientations are significantly different, resulting in inconsistent crystal plane growth directions and different crystal growth rates during crystal growth. This leads to randomness and inhomogeneity of different particles in monocrystalline ternary cathode active materials, reducing the material's conductivity and ion diffusion performance, and also deteriorating the battery's compaction, gas generation, and long-cycle performance.

[0038] To address the problems existing in the aforementioned related technologies, according to the first aspect of this application, a single-crystal ternary cathode active material is provided, wherein the chemical formula of the single-crystal ternary cathode active material is LiNi. a Co b Mn c X d Y eO2, wherein the X element has the effect of promoting the growth tendency of the (003) crystal plane, the Y element has the effect of promoting the growth tendency of the (104) crystal plane, 0.5 ≤ a < 1, 0 ≤ b ≤ 0.2, 0 ≤ c ≤ 0.3, 0 < d ≤ 0.0012, 0 < e ≤ 0.0012, a + b + c + d + e = 1 and 0.2 ≤ d / e ≤ 4.

[0039] The applicant's research found that by doping appropriate amounts of X and Y elements that can promote the growth tendency of the (003) and (104) crystal planes of the ternary cathode active material and controlling the stoichiometric ratio of the X and Y elements within the range of 0.2 - 4, the directional synthesis of the crystal plane orientation and the material morphology can be achieved, thereby preparing a single-crystal ternary cathode active material with high particle roundness and uniform size. Furthermore, the compaction density of the electrode can be increased, and the secondary battery has the advantages of low gas generation and good cycling performance.

[0040] Exemplarily, the stoichiometric ratio of the X and Y elements can be 0.2, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, etc. or within the range composed of any of the above values. If the stoichiometric ratio of the X and Y elements is too large or too small, the particle roundness of the material will become worse and the size distribution will be more dispersed.

[0041] In this application, the "roundness" is obtained by using a scanning electron microscope to obtain the SEM image of the particles and calculating according to the formula f = 4πS / L 2 where S is the projected area of the particles in the SEM image and L is the perimeter of the particles in the SEM image. When the roundness f is 1, it means the figure is circular, and correspondingly the particles are spherical. The smaller f is, the more irregular the figure is and the greater the difference from the spherical shape. In some embodiments of this application, the particle roundness of the single-crystal ternary cathode active material is 0.8 - 1.0. Exemplarily, it can be 0.8, 0.85, 0.9, 0.95, 1.0, etc. or within the range composed of any of the above values.

[0042] The span of particle size distribution is a parameter describing the width of the particle size distribution. In particle size analysis, span is used to measure the breadth of particle size distribution, i.e., the range of particle sizes. Span is typically calculated using three parameters: D10, D50, and D90, representing the particle size corresponding to a cumulative particle size distribution percentage of 10%, 50%, and 90%, respectively. The formula for calculating span is: Span = (D90 - D10) / D50. Generally, the value of span ranges from 0 to 10. A smaller span value indicates a more concentrated particle size distribution, while a larger span value indicates a more dispersed particle size distribution. In some embodiments of this application, the particle size distribution span of the single-crystal ternary cathode active material is ≤1.2. Exemplarily, it can be 1.0, 1.05, 1.1, 1.15, 1.2, or any value within the range of these values.

[0043] In some embodiments, the X element is selected from at least one of Sr, Zr, Ce, and Bi. The applicant has found that doping the crystal structure of nickel-cobalt-manganese ternary materials with elements such as Sr, Zr, Ce, and Bi can promote the growth tendency of the (003) crystal plane, enabling the material to grow along the (003) crystal plane.

[0044] In some embodiments, the Y element is selected from at least one of Sb, Ta, W, and Nb. The applicant has found that doping the crystal structure of nickel-cobalt-manganese ternary materials with elements such as Sb, Ta, W, and Nb can promote the growth tendency of the (104) crystal plane, enabling the material to grow along the (104) crystal plane.

[0045] This application effectively controls the surface energy of each crystal plane orientation during crystal growth by doping the chemical structure of the ternary cathode active material with an appropriate proportion of X and Y elements, so that the growth rate of the material in the (003) and (104) crystal plane directions is controllable, thereby ensuring that the material particles have better roundness and more uniform size distribution.

[0046] It should be noted that although Bi and Sb belong to the same group VA, their roles in this application are completely different. The inventors cannot yet provide a satisfactory theoretical explanation, but experimental results demonstrate this. This shows that even elements from the same group can play different, or even completely opposite, roles in structural doping.

[0047] According to embodiments of this application, in a second aspect, a method for preparing the single-crystal ternary cathode active material described in the first aspect is provided, comprising the following steps:

[0048] After uniformly mixing the nickel-cobalt-manganese hydroxide precursor with lithium salt, X source, and Y source, the mixture is sintered in an oxygen-containing environment to obtain a single-crystal ternary cathode active material.

[0049] The preparation method provided in this application is simple in process, easy to control in operation, and suitable for large-scale production.

[0050] In some embodiments, the X source includes at least one of an oxide, hydroxide, or carbonate of element X. For example, the X source may be at least one of strontium oxide, zirconium dioxide, cerium dioxide, bismuth trioxide, strontium hydroxide, zirconium hydroxide, cerium hydroxide, bismuth hydroxide, strontium carbonate, zirconium carbonate, cerium carbonate, and bismuth carbonate.

[0051] In some embodiments, the Y source includes at least one of the following: oxides, hydroxides, carbonates, and oxyacids of element Y. For example, the Y source may be at least one of antimony trioxide, tantalum pentoxide, tungsten trioxide, niobium trioxide, antimony hydroxide, tantalum hydroxide, tungstic acid, niobium hydroxide, antimony carbonate, tantalum carbonate, tungsten carbonate, and niobium carbonate.

[0052] In some embodiments, the lithium salt includes at least one of lithium carbonate and lithium hydroxide.

[0053] In some embodiments, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn (1-x-y) (OH)2, 0.5≤x<1, 0≤y≤0.2.

[0054] In some embodiments, the median particle size D50 of the nickel-cobalt-manganese hydroxide precursor is 2μm-5μm, for example, it can be 2μm, 3μm, 4μm, 5μm, or within any two of the above values. This ensures sufficient reaction between the nickel-cobalt-manganese hydroxide precursor and the lithium salt, forming a single-crystal ternary cathode active material with controllable size, thereby guaranteeing the performance of electrochemical properties.

[0055] In some embodiments, the heating rate of the sintering process is 5℃ / min-15℃ / min, the isothermal sintering temperature is 750℃-980℃, and the isothermal sintering time is 6h-15h. For example, the heating rate can be 5℃ / min, 7.5℃ / min, 10℃ / min, 12.5℃ / min, 15℃ / min, or any two of the above values; the sintering temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 980℃, or any two of the above values; and the sintering time can be 6h, 8h, 10h, 12h, 15h, or any two of the above values.

[0056] This allows for control over the crystal structure and surface properties of the material, thereby achieving optimal electrochemical performance. This study found that excessively rapid heating rates lead to severe material agglomeration, while excessively slow heating rates negatively impact production capacity. Insufficient sintering temperature or time results in inadequate crystal growth, while excessively high sintering temperature or time leads to over-burning and exacerbated lithium-nickel mixing.

[0057] Specifically, in some embodiments, single-crystal ternary cathode active materials can be prepared using the following methods:

[0058] 1) Precursor preparation: Soluble nickel salt, soluble cobalt salt, and soluble manganese salt are dissolved in deionized water to obtain a salt solution, which is added to a reactor. Simultaneously, a precipitating agent and a chelating agent are added to the reactor, and the mixture is stirred to precipitate. After post-treatment, Ni is obtained. x Co y Mn (1-x-y) (OH)2 precursor;

[0059] The soluble nickel salt is selected from at least one of nickel sulfate, chloride, and acetate; the soluble cobalt salt is selected from at least one of cobalt sulfate, chloride, and acetate; and the soluble manganese salt is selected from at least one of manganese sulfate, chloride, and acetate. The molar ratio of nickel, cobalt, and manganese in the salt solution is 0.5-1:0-0.2:0-0.3. The precipitant is selected from at least one of sodium carbonate and sodium hydroxide; and the chelating agent is selected from at least one of ammonium bicarbonate, ammonium carbonate, and ammonia water. The molar ratio of the chelating agent to the metal element (total nickel, cobalt, and manganese) is 1-4:1.

[0060] 2) The nickel-cobalt-manganese hydroxide precursor obtained in step 1) is thoroughly mixed with lithium salt, X source and Y source, heated to 750℃-980℃ in air or oxygen environment at a rate of 5℃ / min-15℃ / min, calcined for 6h-15h, then cooled to room temperature and crushed to obtain single crystal ternary cathode active material.

[0061] The lithium salt includes at least one of lithium carbonate and lithium hydroxide, and the molar ratio of the lithium salt to the nickel cobalt manganese hydroxide precursor is 1.0-1.05:1; the X source includes at least one of the oxides, hydroxides, and carbonates of element X, such as strontium oxide, zirconium dioxide, cerium dioxide, bismuth trioxide, strontium hydroxide, zirconium hydroxide, cerium hydroxide, bismuth hydroxide, strontium carbonate, zirconium carbonate, cerium carbonate, and bismuth carbonate; the Y source includes at least one of the oxides, hydroxides, and carbonates of element Y, such as antimony trioxide, tantalum pentoxide, tungsten trioxide, niobium trioxide, antimony hydroxide, tantalum hydroxide, tungsten hydroxide, niobium hydroxide, antimony carbonate, tantalum carbonate, tungsten carbonate, and niobium carbonate.

[0062] According to a third aspect of this application, a positive electrode sheet is provided, comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive active material layer comprises a single-crystal ternary positive active material according to the first aspect of this application or a single-crystal ternary positive active material prepared by the preparation method described in the second aspect of this application.

[0063] Those skilled in the art will understand that the positive electrode sheet in this application has the advantage of high compaction density because it includes a single-crystal ternary positive electrode active material with high particle sphericity and uniform size.

[0064] In some embodiments, the compaction density of the positive electrode sheet can reach 3.50 g / cm³. 3 -3.62g / cm 3 For example, the compaction density of the positive electrode sheet can be 3.50 g / cm³. 3 3.52g / cm 3 3.54g / cm 3 3.56g / cm 3 3.58g / cm 3 3.60g / cm 3 3.62g / cm 3 It is equal to or falls within the range of any of the above values.

[0065] According to a fourth aspect of this application, a secondary battery is provided, including the positive electrode sheet described in the third aspect of this application.

[0066] Those skilled in the art will understand that the secondary battery of this application has the advantages of high specific capacity, good cycle performance and low gas production.

[0067] For example, the secondary battery can be a lithium-ion secondary battery. Typically, a lithium-ion secondary battery also includes a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0068] The following uses a lithium-ion secondary battery as an example to illustrate the secondary battery of this application.

[0069] [Positive electrode plate]

[0070] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0071] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector.

[0072] In some embodiments, the positive electrode active material layer does not exclude other positive electrode active materials other than the single crystal ternary positive electrode active material described in the first aspect of the present application. For example, other positive electrode active materials may adopt positive electrode active materials known in the art for lithium ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), iron pyrophosphate (Li2FeP2O7), lithium cobalt oxide (LiCoO2), spinel type lithium manganese oxide (LiMn2O4), spinel type lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), layered lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeO2), lithium manganate (LiMgO2), lithium calcium oxide (LiCaO2), lithium copper oxide (LiCuO2), lithium zinc oxide (LiZnO2), lithium molybdate (LiMoO2), lithium tantalate (LiTaO2), lithium tungstate (LiWO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.), lithium-rich materials (such as lithium-rich nickel cobalt manganese oxides), manganese dioxide (MnO2), vanadium oxides, sulfur oxides, silicate oxides, and at least one of their respective modified compounds. These materials can be used alone or in combination of two or more.

[0073] The modified compounds for the above-mentioned positive electrode active materials can be modified by doping, surface coating, or both doping and coating.

[0074] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0075] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0076] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0077] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0078] [Negative electrode plate]

[0079] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0080] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0081] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the specific type of the negative electrode active material is not specifically limited and can be selected according to needs. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0082] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0083] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0085] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0086] [Electrolytes]

[0087] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0088] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0089] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0090] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0091] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0092] In some embodiments, the electrolyte is a solid electrolyte, which can be various lithium-ion solid electrolytes commonly used in the art. Examples of lithium-ion solid electrolytes are provided below, including but not limited to:

[0093] LISICON type: such as γ-Li3PO4, etc.;

[0094] NASICON type; for example, Li (1+x1) Q x M (2-x1) (PO4)3, 0≤x1<1, Q includes at least one of Al, Cr, Ba, Fe, Sc, In, Lu, Y, and La;

[0095] Garnet type; for example, Li (7-x2) La3Zr (2-x2) M x2 O 12 Etc., 0≤x2<1, M includes at least one of Sb, Nb, Ta, Te, and W;

[0096] LIPON type: such as Li x3 PO y1 N z1 ; 0 < x3 ≤ 1, 0 < y1 ≤ 1, 0 < z1 ≤ 1;

[0097] Perovskite type: such as Li3 x 4Q (2 / 3-x4) MO3, etc., 0.04 < x4 < 0.17, Q includes at least one of La, Sr, Ba, Nd, and M includes at least one of Al, Ti, Ge;

[0098] Anti-Perovskite type: such as Li3OCl, etc.;

[0099] Thio-LiSICON type: such as Li (3+x5) My2A (1-y2) Q (4-z2) T z2 , where -1 < x5 < 2, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, and T includes at least one of F, Cl, Br, I;

[0100] Sulfide solid electrolyte, including: Thiophosphate type: Li3PS4, etc., Argyrodite type: Li6PS5Cl, Halide type: Li3InCl6, Hydride type: 0.7Li(CB9H 10 ) - 0.3Li(CB 11 H 12 ) at least one of; such as Li (10+x6) M (1+y3) A (2-y3) Q (12-z3) H z3Type: where -2 < x6 < 2, 0 ≤ y3 ≤ 2, 0 ≤ z3 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo; A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, H includes at least one of F, Cl, Br, I: (100 - x7)Li2S·x7M·y4Q type: where 20 ≤ x7 ≤ 30, 0 ≤ y4 ≤ 50, M includes at least one of B2S3, Al2S3, In2S3, SiS2, GeS2, SnS2, P2S5, As2S3, Sb2S5, Bi2S3, WS2, MoS2, Q includes at least one of B2O3, Al2O3, In2O3, SiO2, GeO2, SnO2, P2O5, Sb2O5, Bi2O3, WO2, WO3, MoO2, MoO3, Fe2O3, ZnO, MgO, CuO, CaO, LiN, Li2O, LiF, LiCl, LiBr, LiI; Argyrodite type: Li (6+x8) M y5 A (1-y5) Q (5-z5) T (1+z5) , where -1 ≤ x8 ≤ 1, 0 ≤ y5 ≤ 1, -1 < z5 ≤ 1, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, T includes at least one of F, Cl, Br, I; Halide type: Li3MJ or Li2Sc 2 / 3 J; M includes at least one of Y, Er, In, Sc, Ga, J includes at least one of F, Cl, Br, I.

[0101] When the above sulfide solid electrolyte is a sulfide-based solid electrolyte, it includes, but is not limited to: argyrodite electrolyte; binary sulfide-based solid systems such as Li2S-P2S5, Li2S-SiS2, Li2S-GeS, and Li2S-B2S3, and Li2S-Me-P2S5 ternary systems, where Me is selected from Si, Ge, Sn, or Al, etc.

[0102] Specifically, the above sulfide electrolyte is selected from at least one of Li2S-P2S5, Li2S-SiS2, Li2S-GeS, Li2S-B2S3, and Li2S-Me-P2S5.

[0103] [Separator membrane]

[0104] This application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0105] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0106] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0107] In some embodiments, the lithium-ion secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0108] In some implementations, the outer packaging of a lithium-ion secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0109] This application does not impose any particular restrictions on the shape of the lithium-ion secondary battery, which can be cylindrical, square, or any other arbitrary shape.

[0110] In some implementations, lithium-ion secondary batteries can be assembled into battery modules, and the number of lithium-ion secondary batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0112] According to a fifth aspect of this application, this application provides an electrical device including the secondary battery described in the fourth aspect of this application.

[0113] In some embodiments, the aforementioned electrical device may also include a battery module or battery pack assembled from the aforementioned secondary batteries. The secondary batteries, battery modules, or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0114] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements. An example electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0115] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a lithium-ion rechargeable battery as their power source.

[0116] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0117] Example 1

[0118] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0119] Take 5kg Ni 0.52 Co 0.2 Mn 0.28 After thoroughly mixing (OH)2 precursor (D50 of 4.8 μm), 2.02 kg of lithium carbonate, 842.44 g of strontium carbonate, and 715.24 g of niobium pentoxide, the mixture was sintered in air at a heating rate of 15 °C / min, a sintering temperature of 980 °C, and a sintering time of 6 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0120] Example 2

[0121] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0122] Take 5kg Ni 0.6 Co 0.1 Mn 0.3 After thoroughly mixing (OH)2 precursor (D50 of 2.1 μm), 2.12 kg of lithium carbonate, 92.12 g of cerium dioxide, and 203.86 g of tungstic acid, the mixture was sintered in air at a heating rate of 10 °C / min, a sintering temperature of 950 °C, and a isothermal period of 10 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0123] Example 3

[0124] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0125] Take 5kg Ni 0.95 Co 0.03 Mn 0.02After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 5.957 g of bismuth pentoxide, and 3.321 g of antimony pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material.

[0126] Example 4

[0127] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0128] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 2.085 g of bismuth pentoxide, and 6.643 g of antimony pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material.

[0129] Example 5

[0130] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0131] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 5.957 g of bismuth pentoxide, and 1.329 g of antimony pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material.

[0132] Example 6

[0133] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0134] Take 5kg Ni 0.95 Co 0.03 Mn 0.02A mixture of (OH)₂ precursor (D50 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 8.729 g of zirconium hydroxide, and 6.105 g of tantalum pentoxide was thoroughly mixed and sintered under oxygen conditions. The heating rate was 5 °C / min, the sintering temperature was 800 °C, and the isothermal period was 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material. See the SEM image below. Figure 1 .

[0135] from Figure 1 It can be seen that the single-crystal particles of the ternary cathode active material prepared in this embodiment have good sphericity and size consistency.

[0136] Example 7

[0137] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0138] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 8.729 g of zirconium hydroxide, and 3.053 g of tantalum pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0139] Example 8

[0140] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0141] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 4.365 g of zirconium hydroxide, 3.053 g of strontium carbonate, and 6.105 g of tantalum pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material.

[0142] Example 9

[0143] The preparation method of the single-crystal ternary cathode active material in this embodiment includes the following steps:

[0144] Take 5kg Ni 0.95 Co 0.03 Mn 0.02After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 8.729 g of zirconium hydroxide, 3.576 g of niobium pentoxide, and 3.053 g of tantalum pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0145] Comparative Example 1

[0146] The preparation method of the single-crystal ternary cathode active material in this comparative example includes the following steps:

[0147] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)₂ precursor (D50 of 3.5 μm) and 2.35 kg of lithium hydroxide monohydrate, sintering was carried out under oxygen conditions. The heating rate was 5 °C / min, the sintering temperature was 800 °C, and the isothermal period was 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material. See the SEM image below. Figure 2 .

[0148] contrast Figure 1 and Figure 2 It can be seen that the single crystal particles of the ternary cathode active material without dopants have poor sphericity and size uniformity.

[0149] Comparative Example 2

[0150] The preparation method of the single-crystal ternary cathode active material in this comparative example includes the following steps:

[0151] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 (OH)₂ precursor (D50 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, and 8.729 g of zirconium hydroxide were thoroughly mixed and sintered under oxygen conditions. The heating rate was 5 °C / min, the sintering temperature was 800 °C, and the isothermal period was 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material. See the SEM image below. Figure 3 .

[0152] contrast Figure 1 and Figure 3 It can be seen that single Zr doping increases particle size while reducing particle roundness and size uniformity.

[0153] Comparative Example 3

[0154] The preparation method of the single-crystal ternary cathode active material in this comparative example includes the following steps:

[0155] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 (OH)₂ precursor (D50 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, and 6.105 g of tantalum pentoxide were thoroughly mixed and sintered under oxygen conditions. The heating rate was 5 °C / min, the sintering temperature was 800 °C, and the isothermal period was 15 h. After natural cooling to room temperature, the mixture was crushed to obtain a single-crystal ternary cathode active material. See the SEM image below. Figure 4 .

[0156] contrast Figure 1 and Figure 4 It can be seen that single Ta doping reduces the roundness and size uniformity of the particles.

[0157] Comparative Example 4

[0158] The preparation method of the single-crystal ternary cathode active material in this comparative example includes the following steps:

[0159] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 10.475 g of zirconium hydroxide, and 3.053 g of tantalum pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0160] Comparative Example 5

[0161] The preparation method of the single-crystal ternary cathode active material in this comparative example includes the following steps:

[0162] Take 5kg Ni 0.95 Co 0.03 Mn 0.02 After thoroughly mixing (OH)2 precursor (D50 of 3.5 μm), 2.35 kg of lithium hydroxide monohydrate, 1.746 g of zirconium hydroxide, and 15.263 g of tantalum pentoxide, the mixture was sintered under oxygen conditions at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a isothermal period of 15 h. The mixture was then naturally cooled to room temperature and crushed to obtain a single-crystal ternary cathode active material.

[0163] Test case

[0164] 1. Metal element content test

[0165] Ni / Co / Mn / Sr / Ce / Bi / Zr / Nb / W / Sb / Ta elemental testing: Accurately weigh the sample to be tested, add concentrated HCl and concentrated HF to dissolve at low temperature, add concentrated HNO3 dropwise, and then transfer to a volumetric flask for final volume adjustment. Use an ICP-5000 inductively coupled plasma atomic emission spectrometer for bidirectional (horizontal) observation to test the mass fraction of each metal element in the material and calculate the corresponding molar ratio.

[0166] 2. Circularity test

[0167] SEM images were tested using a Phenom Pro desktop scanning electron microscope, and the sphericity f was obtained through image recognition and statistical analysis using ImageJ software.

[0168] 3. Particle size test

[0169] The D10, D50, and D90 tests can be performed using a laser particle size analyzer (Malvern Master Size 3000) in accordance with GB / T19077-2016 / ISO 13320:2009.

[0170] 4. Electrical performance testing

[0171] 4.1 Battery Assembly

[0172] Negative electrode homogenate: The above raw materials are dispersed in water and stirred evenly according to the mass ratio of artificial graphite (FSN-1, Shanshan Technology), conductive agent (Super P, French Yirui Stone), binder CMC (Japan Paper) and binder SBR (ZeonR) of 95:2:2:1, to prepare a negative electrode slurry with a solid content of 50wt%.

[0173] Negative electrode preparation: The above negative electrode slurry is coated onto the surface of the current collector using a coater, then placed in a vacuum oven and vacuum dried at 120°C for 12 hours, and finally rolled to obtain a compacted density of 1.48 g / cm³. 3 The negative electrode plate;

[0174] Positive electrode slurry: The single-crystal ternary positive electrode active material, conductive agent (Super P, French Yirui Stone), and binder (PVDF, Solvay) provided in each embodiment and comparative example are dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 and stirred evenly to prepare a positive electrode slurry with a solid content of 65wt%.

[0175] Positive electrode preparation: The above positive electrode slurry is coated on the surface of the current collector using a coater, and then placed in a vacuum oven to be vacuum dried at 120°C for 12 hours. Gradient compaction density electrode preparation is carried out, and the prepared positive electrode is folded three times. The maximum compaction density at which the electrode does not break easily and does not transmit light is taken as the usable electrode compaction.

[0176] Assembly: The positive electrode, negative electrode and separator are stacked in a certain order, then placed in an aluminum-plastic film package and sealed by a heat sealing machine to form a 5Ah soft pack battery;

[0177] Liquid injection: LiPF6 is dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DMC) (volume ratio EC:DMC = 1:1) to obtain a LiPF6 concentration of 1 mol / L solution, which is then injected into the above-mentioned pouch cell with an injection coefficient of 2.84 g / Ah. The cell is then sealed to obtain a pouch cell.

[0178] 4.2, 0.33C capacity

[0179] The process was conducted in a 25°C constant temperature chamber. The battery was charged and discharged at a constant current and constant voltage rate of 0.33C. The charging cutoff voltage was 4.25V and the discharging cutoff voltage was 2.75V. The discharge capacity obtained in this way was used as the standard capacity (0.33C capacity).

[0180] 4.3 High-temperature gas production

[0181] The volume of the battery before and after storage at 60°C for 28 days was tested using the water displacement method and labeled as v1 and v2, respectively. The gas production was calculated as v = (v2 - v1) / C, where C is the battery capacity.

[0182] 4.4 Cyclic Performance

[0183] After standing in the constant temperature chamber for 1 hour, perform 1C constant current and constant voltage charging to the charging cutoff voltage of 4.25V and the cutoff current of 0.065A. After charging is completed, stand for 1 hour and then discharge with constant current to the discharge cutoff voltage of 2.75V. Repeat the above steps.

[0184] Please see Tables 1-3 for the test results above, where “ / ” indicates that the item does not exist.

[0185] Table 1 Single-crystal ternary cathode active materials (LiNi) a Co b Mn c X d Y e Chemical composition of O2

[0186]

[0187] Table 2 Structural parameters of single-crystal ternary cathode active materials

[0188] Doping ratio d / e Particle roundness f Span Example 1 1.06 0.82 1.1 Example 2 0.66 0.84 1.13 Example 3 1.25 0.99 1.04 Example 4 0.25 0.93 1.18 Example 5 2.5 0.87 1.19 Example 6 1.83 0.96 1.09 Example 7 3.67 0.9 1.19 Example 8 3.67 0.95 1.13 Example 9 1.38 0.92 1.03 Comparative Example 1 / 0.61 1.31 Comparative Example 2 / 0.68 1.45 Comparative Example 3 / 0.67 1.29 Comparative Example 4 4.33 0.73 1.44 Comparative Example 5 0.14 0.71 1.38

[0189] Table 3 Electrode Compaction and Battery Performance

[0190]

[0191]

[0192] As can be seen from Tables 1-3, the doping ratio of X and Y elements in the single-crystal ternary cathode active materials prepared in Examples 1-9 is in the range of 0.2-4.0, which makes the single-crystal ternary cathode active materials of Examples 1-9 have the characteristics of high particle sphericity and uniform size. This results in the cathode sheet using the materials of Examples 1-9 having a higher compaction density, thereby improving the electrical performance and safety of the battery.

[0193] Compared to Example 6, Comparative Example 1 had no doped elements, Comparative Example 2 had only Zr doped, Comparative Example 3 had only Ta doped, Comparative Example 4 had a Zr / Ta doping ratio of 4.33, and Comparative Example 5 had a Zr / Ta doping ratio of 0.14. All of these factors would lead to a decrease in the roundness and size uniformity of the single-crystal ternary cathode active material particles, thereby affecting the compaction density of the cathode sheet and the cycle and safety performance of the battery.

[0194] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A single-crystal ternary cathode active material, characterized in that, The single-crystal ternary positive electrode active material has a chemical formula of LiNi a Co b Mn c X d Y e O2, wherein the X element has a role of promoting growth of a (003) crystal face, the Y element has a role of promoting growth of a (104) crystal face, 0.5≤a<1, 0≤b≤0.2, 0≤c≤0.3, 0<d≤0.0012, 0<e≤0.0012, a+b+c+d+e=1, and 0.2≤d / e≤4.

2. The single-crystal ternary cathode active material according to claim 1, characterized in that, The X element is selected from at least one of Sr, Zr, Ce, and Bi, and / or the Y element is selected from at least one of Sb, Ta, W, and Nb.

3. The single-crystal ternary cathode active material according to claim 1 or 2, characterized in that, The particle sphericity of the single-crystal ternary cathode active material is 0.8-1.

0.

4. The single-crystal ternary cathode active material according to claim 1 or 2, characterized in that, The particle size distribution of the single-crystal ternary cathode active material is Span≤1.

2.

5. The method for preparing the single-crystal ternary cathode active material according to any one of claims 1-4, characterized in that, Includes the following steps: After uniformly mixing the nickel-cobalt-manganese hydroxide precursor with lithium salt, X source, and Y source, sintering is carried out in an oxygen-containing environment to obtain a single-crystal ternary cathode active material.

6. The method for preparing the single-crystal ternary cathode active material according to claim 5, characterized in that, The X source includes at least one of the oxides, hydroxides, and carbonates of element X; And / or, the Y source includes at least one of the following: oxides, hydroxides, carbonates, and oxyacids of element Y; And / or, the lithium salt includes at least one of lithium carbonate and lithium hydroxide; and / or the nickel cobalt manganese hydroxide precursor has a chemical formula of Ni x Co y Mn (1-x-y) (OH)2, 0.5≤x<1, 0≤y≤0.2; And / or, the median particle size D50 of the nickel-cobalt-manganese hydroxide precursor is 2 μm-5 μm; And / or, the heating rate of the sintering process is 5℃ / min-15℃ / min, the sintering temperature in the isothermal section is 750℃-980℃, and the sintering time in the isothermal section is 6h-15h.

7. A positive electrode sheet, characterized in that, include: A positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector, wherein the positive active material layer comprises the single-crystal ternary positive active material according to any one of claims 1-4 or the single-crystal ternary positive active material prepared by the preparation method according to claim 5 or 6.

8. The positive electrode sheet according to claim 7, characterized in that, The compacted density of the positive electrode plate is 3.50 g / cm 3 - 3.62 g / cm 3 .

9. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 8 or 9.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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