CN117855400A - Low-gas-yield long-cycle monocrystal ternary cathode material and preparation method thereof - Google Patents

Low-gas-yield long-cycle monocrystal ternary cathode material and preparation method thereof Download PDF

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CN117855400A
CN117855400A CN202211210504.7A CN202211210504A CN117855400A CN 117855400 A CN117855400 A CN 117855400A CN 202211210504 A CN202211210504 A CN 202211210504A CN 117855400 A CN117855400 A CN 117855400A
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coating
positive electrode
single crystal
sintering
mixing
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李德祥
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Ningxia Zhonghua Lithium Battery Material Co ltd
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Ningxia Zhonghua Lithium Battery Material Co ltd
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Priority to TW112137104A priority patent/TW202415623A/en
Priority to PCT/CN2023/121966 priority patent/WO2024067685A1/en
Publication of CN117855400A publication Critical patent/CN117855400A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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Abstract

The invention provides a monocrystal ternary positive electrode material, which is a nickel cobalt lithium manganate positive electrode material doped with doping elements A and B and coated with coating elements on the surface; the doped element A is Nb element, the doped element B is one or more elements selected from Al, mg, zr, ti, Y, cr, sn and W, and the cladding element is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, B, W and Nb. The monocrystal ternary positive electrode material provided by the invention has the characteristics of good primary particle size consistency, continuous and uniform coating layer, higher specific capacity, good gas production performance in high-temperature storage and good cycle stability, and the preparation method is simple and easy to operate and can be industrialized.

Description

Low-gas-yield long-cycle monocrystal ternary cathode material and preparation method thereof
Technical Field
The invention belongs to the field of lithium ion battery anode materials, and relates to a low-gas-yield long-cycle monocrystal ternary anode material and a preparation method thereof.
Background
Compared with the traditional chemical energy storage battery, the lithium ion battery has obvious advantages in energy density and cycle life, but the lithium ion battery has a great difference in temperature adaptability, and side reactions between the anode and the cathode of the lithium ion battery and electrolyte are increased at high temperature, so that the problems of battery failure caused by increase of internal resistance, gas production bulge, rapid reduction of cycle performance at high voltage and the like are solved.
There have been studies in the prior art to overcome the above problems by coating. For example, chinese patent document CN202110514188.1 discloses a coated ternary cathode material, a method for preparing the same, and a lithium ion battery. The coated ternary positive electrode material comprises an aluminum, zirconium and fluorine co-doped ternary positive electrode active material inner core and a coating layer coated on the surface of the inner core, wherein the coating layer comprises zirconium hydrogen phosphate and a boron compound. The main drawbacks of this type of prior art are: the prepared monocrystal material has the advantages that the morphology consistency of primary particles is poor, the proportion of primary particles with smaller particle sizes is high, the specific surface area of the material is large, the side reaction between the material and electrolyte is increased, and the high-temperature storage gas production and the circulation performance of the material are further reduced; conventional coating processes often fail to provide a coating of uniform thickness, and individually nucleated coating material particles and excessively thick coatings can reduce the kinetics of lithium ion deintercalation, impeding the capacity expression of the active material.
Disclosure of Invention
The invention aims to provide a low-gas-yield long-cycle monocrystal ternary cathode material and a preparation method thereof. The monocrystal ternary positive electrode material provided by the invention has the characteristics of good primary particle size consistency, continuous and uniform coating layer, higher specific capacity, good gas production performance in high-temperature storage and good cycle stability, and the preparation method is simple and easy to operate and can be industrialized.
Specifically, one aspect of the invention provides a single crystal ternary positive electrode material, which is a nickel cobalt lithium manganate positive electrode material doped with doping elements A and B and coated with coating elements on the surface;
the doped element A is Nb element, the doped element B is one or more elements selected from Al, mg, zr, ti, Y, cr, sn and W, and the cladding element is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, B, W and Nb.
In one or more embodiments, the doping element a is added in an amount of 0.01wt% to 0.15wt%.
In one or more embodiments, the doping element B is added in an amount of 0.05wt% to 0.5wt%.
In one or more embodiments, the single crystal ternary cathode material includes a first coating layer and a second coating layer located inside and on a surface of the single crystal ternary cathode material, respectively, the coating elements including a coating element C and a coating element D, the coating element C being present in the first coating layer, the coating element D being present in the second coating layer;
wherein the coating element C is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, and the coating element D is B.
In one or more embodiments, the coating element C is added in an amount of 0.05wt% to 0.25wt%.
In one or more embodiments, the coating element D is added in an amount of 0.02wt% to 0.25wt%.
In one or more embodiments, the primary particles of the single crystal ternary cathode material have an average particle size of between 1.5 and 2.5 μm, preferably between 1.8 and 2.3 μm.
In one or more embodiments, the number of primary particles in the single crystal ternary cathode material having a particle size of less than 1.0 μm is no greater than 2%.
In one or more embodiments, the primary particles of the single crystal ternary cathode material having a particle size greater than 1.0 μm have an average particle size of no greater than 2.2 μm.
In one or more embodiments, the absolute value of the distribution bias of particle sizes of more than 500 primary particles counted in the single crystal ternary positive electrode material is less than 0.6.
In one or more embodiments, the surface hydroxyl content of the single crystal ternary cathode material is < 0.06wt%.
Another aspect of the present invention provides a method of preparing a single crystal ternary cathode material as described in any one of the embodiments herein, the method comprising the steps of:
(1) Mixing a nickel cobalt manganese hydroxide precursor, a lithium source, a doping agent A containing a doping element A and a doping agent B containing a doping element B to obtain uniformly mixed solid powder;
(2) Sintering the solid powder obtained in the step (1) to obtain a monocrystal ternary anode material to be coated;
(3) Crushing the single crystal ternary cathode material to be coated obtained in the step (2) to obtain a crushed ternary cathode material;
(4) Mixing the crushed ternary cathode material obtained in the step (3) with a coating agent containing a coating element to obtain a coating material;
(5) And (3) sintering the coating material obtained in the step (4) to obtain the coated monocrystal ternary anode material.
In one or more embodiments, the method comprises the steps of:
(1) Mixing a nickel cobalt manganese hydroxide precursor, a lithium source, a doping agent A containing a doping element A and a doping agent B containing a doping element B to obtain uniformly mixed solid powder;
(2) Sintering the solid powder obtained in the step (1) to obtain a monocrystal ternary anode material to be coated;
(3) Crushing the single crystal ternary cathode material to be coated obtained in the step (2) to obtain a crushed ternary cathode material;
(4') mixing the crushed ternary cathode material obtained in the step (3) with a coating agent C containing a coating element C to obtain a first coating material;
(5 ') sintering the first coating material obtained in the step (4') to obtain a primary coated single crystal ternary anode material;
(6 ') mixing the primary coated ternary cathode material obtained in the step (5') with a coating agent D containing a coating element D to obtain a second coating material;
and (7 ') sintering the second coating material obtained in the step (6') to obtain the secondary coated single crystal ternary anode material.
In one or more embodiments, in step (1), the material is mixed in a dry high speed mixing process, preferably by: mixing at 200-300r/min for 3-8min, and then mixing at 600-800r/min for 20-30min at high speed.
In one or more embodiments, in step (1), the dopant a is Nb 2 O 5 And/or the dopant B is an oxide and/or hydroxide of the doping element B.
In one or more embodiments, in step (2), the sintering procedure comprises a step of sintering at 900 ℃ to 980 ℃ for 8 to 16 hours.
In one or more embodiments, in step (2), the volume fraction of oxygen in the sintering atmosphere is greater than or equal to 70%.
In one or more embodiments, in step (4) or step (4 ') or step (6'), the high speed mixing is performed by dry coating, preferably by: mixing at 200-300r/min for 1-5min, and then mixing at 600-800r/min for 10-20min.
In one or more embodiments, in step (4'), the coating agent C is an oxide and/or hydroxide of the coating element C.
In one or more embodiments, in step (5), the sintering time is from 5 to 12 hours and the sintering temperature is from 150 to 650 ℃.
In one or more embodiments, in step (5'), the sintering time is from 5 to 12 hours and the sintering temperature is from 500 to 650 ℃.
In one or more embodiments, in step (6'), the coating agent D is a boron-containing compound other than boric acid and boron oxide, preferably B 2 Co 3 H 6 、B 2 Co 3 O 6 And/or AlB 4 。
In one or more embodiments, in step (7'), the sintering time is from 5 to 12 hours and the sintering temperature is from 150 to 500 ℃.
The invention also provides a single crystal ternary positive electrode material prepared by adopting the method of any embodiment.
The invention also provides a positive electrode sheet comprising the single crystal ternary positive electrode material described in any one of the embodiments herein.
The invention also provides a lithium ion battery or a lithium ion battery cell comprising the positive electrode sheet according to any of the embodiments herein.
Drawings
FIG. 1 is a schematic structural diagram of a single crystal ternary cathode material of the present invention.
FIG. 2 is a Scanning Electron Microscope (SEM) photograph of the final product of the positive electrode material in example 1.
Fig. 3 is an SEM photograph of the end product of the cathode material in comparative example 1.
Fig. 4 is a histogram of the primary particle size distribution of the final product of the positive electrode material of example 1, in which the abscissa indicates the particle diameter (unit μm) and the ordinate indicates the number of particles.
Fig. 5 is a histogram of the primary particle size distribution of the final product of the positive electrode material of comparative example 1, in which the abscissa indicates the particle diameter (unit μm) and the ordinate indicates the number of particles.
Fig. 6 is an SEM photograph of the cathode material before coating in example 1.
Fig. 7 is an SEM photograph of the positive electrode material after the double coating in example 1.
Fig. 8 is an SEM photograph of the positive electrode material after primary coating in example 1.
Fig. 9 is an SEM photograph of the positive electrode material after one coating in comparative example 4.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. 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 invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
Herein, "comprising," "including," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., "a consisting essentially of B and C" and "a consisting of B and C" should be considered to have been disclosed herein when "a comprises B and C" is disclosed herein.
All features such as values, amounts, and concentrations that are defined herein in the numerical or percent ranges are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
Herein, unless otherwise specified, percentages refer to mass percentages, and proportions refer to mass ratios.
Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.
Single crystal ternary positive electrode material
The monocrystal ternary positive electrode material is a nickel cobalt lithium manganate positive electrode material doped with doping elements A and B and coated with coating elements.
The single crystal ternary positive electrode material of the inventionCan be represented by the chemical formula Li n Ni x Co y Mn 1-x-y O 2 ·A a B b Z z O 2 Wherein n is more than or equal to 1 and less than or equal to 1.1,0.5, x is more than or equal to 0.8, y is more than or equal to 0 and less than or equal to 0.15, and a, B and Z can be determined according to the addition amount and valence state of the doping element A, the doping element B and the cladding element Z. In some embodiments, coating element Z comprises coating element C and coating element D, optionally also coating element E, and the chemical formula of the single crystal ternary positive electrode material may be represented as Li n Ni x Co y Mn 1-x-y O 2 ·A a B b C c D d E e O 2 C, D, E can be determined according to the addition amounts and valence states of the coating elements C, D, E. In some embodiments, 1.03.ltoreq.n.ltoreq.1.07. In some embodiments, 0.55.ltoreq.x.ltoreq.0.7. In some embodiments, 0.05.ltoreq.y.ltoreq.0.12. The monocrystal ternary anode material is preferably a low-cobalt material, and y is preferably more than 0 and less than or equal to 0.1. In the invention, the effect of improving the gas production performance and the circulation stability is more outstanding on the low cobalt material. In some embodiments, 0.6.ltoreq.x.ltoreq.0.7, 0.05.ltoreq.y.ltoreq.0.1, e.g., x=0.65, y=0.07.
In the invention, the doping element A is Nb element. Nb can be used 2 O 5 Nb element is introduced as dopant a into the positive electrode material. The added amount of Nb is 0.01wt% to 0.15wt%, for example, 0.02wt%, 0.05wt%, 0.1wt%. In the invention, the addition amount of the doping element or the coating element refers to the mass fraction of the doping element or the coating element in the total mass of the final positive electrode material. The doping element A improves the internal structure of the crystal, improves the particle consistency of primary particles, and improves the thermal stability of the material under the high-temperature condition. The doping element A diffuses into the lattice, so that the primary particle form of the nickel cobalt lithium manganate (NCM) ternary material is changed, the nickel cobalt lithium manganate (NCM) ternary material is more round, and the proportion of particles with smaller particle size is greatly reduced. In addition, nb doping forms a structure that effectively eliminates abrupt internal strain caused by the h2→h3 phase transition. The elimination of internal strain can significantly improve the long-cycling stability of Nb-doped NCM positive electrodes, while the presence of Nb ions can hinderAlong the grain boundary impurity phase formation, which is beneficial for the structural stability under its heat load conditions.
In the present invention, the doping element B is one or more elements selected from Al, mg, zr, ti, Y, cr, sn and W. The doping element B is added in an amount of 0.05wt% to 0.5wt%, for example, 0.1wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%. The doping element B may be introduced into the positive electrode material using an oxide or hydroxide of the doping element B as the doping agent B. In some embodiments, doping element B is selected from one or more of Ti, mg, Y and Zr, and accordingly TiO may be used 2 、MgO 2 、Y 2 O 5 And ZrO(s) 2 As dopant B. The doping agent B can effectively prevent lithium and nickel from being mixed, inhibit harmful phase change, reduce internal stress and alleviate microcrack generation.
In the present invention, the cladding element may contain one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, B, W and Nb.
In the present invention, the single crystal ternary cathode material preferably includes a first coating layer and a second coating layer respectively located inside and on the surface of the single crystal ternary cathode material, the first coating layer and the second coating layer being in contact with each other. The cladding elements preferably include a cladding element C and a cladding element D, wherein the cladding element C is present in the first cladding layer and the cladding element D is present in the second cladding layer.
In the present invention, the coating element C is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co. The coating element C may be introduced into the positive electrode material from an oxide or hydroxide of the coating element C as the coating agent C. Coating agent C is nanoscale. The amount of the coating element C added is 0.05wt% to 0.25wt%, for example, 0.1wt% and 0.2wt%. Preferably, the coating element C is one or two selected from Zn, V, sn and Ce, wherein the addition amount of each of Zn, V, sn and Ce is preferably 0.05wt% to 0.2wt%, for example 0.1wt%, 0.15wt%. For example, in some embodiments, the coating element C is V and Ce. In some embodiments, coating element C is Ce. In other embodiments, the coating element C is Zn and Sn. The coating element C forms a grid-shaped structure through combination and sharing with metal ions, and the formed coating layer is difficult for oxygen atoms to pass through, so that oxygen can be effectively prevented from passing through, and further, the high-temperature storage gas production performance of the material is improved.
In the invention, the cladding element D is the element B. The invention introduces B element into the positive electrode material by using a boron-containing compound which is not boric acid or boric oxide as a coating agent D. Examples of coating agents D include B 2 Co 3 H 6 、B 2 Co 3 O 6 And AlB 4 . The ternary positive electrode material is characterized in that the outermost layer is coated with the coating element D, and the mass fraction of hydroxyl on the surface of the ternary positive electrode material is less than 0.06%. Hydroxyl is used as one of the main existence forms of residual lithium on the surface of the positive electrode material, and the excessive content of the hydroxyl can lead to higher viscosity when the battery core is pulped, and cause higher rate of increase of direct current impedance (DCR) and higher gas production of the battery core in a long cycle process. The amount of the coating element D added is 0.02wt% to 0.25wt%, preferably 0.02wt% to 0.08wt%, for example 0.06wt%. The coating agent D and the NCM have strong reactivity with oxygen on the surface, and the formed coating layer has excellent oxidation resistance, so that the coating layer can not only dynamically inhibit oxygen from penetrating or flowing through the coating to cause loss, but also combine with Li alkali metal to become a good mixed conductor of ions and electrons, thereby improving the cycle performance and gas production performance of the product. The main boron source of the boron coating is boric acid or boron oxide, and the two boron-containing compounds are preferentially combined with residual alkali on the surface of the positive electrode material, so that the mass fraction of hydroxyl on the surface is usually more than 1000 ppm.
In the present invention, the second coating layer of the ternary cathode material optionally further contains a coating element E. The coating element E may be one or more elements selected from Al, ti, mg, zn, W. In some embodiments, the cladding element E is one or more elements selected from Al, mg, zn. AlH can be used separately 6 P 3 O 12 、ZnO、Mg(OH) 2 As a bagThe coating agent E introduces Al, mg and Zn as coating elements E into the positive electrode material. In the present invention, when the ternary positive electrode material contains the coating element E, the additive amount of the coating element E may be 0.05wt% to 0.25wt%, for example, 0.1wt%, 0.15wt%, 0.2wt%. Coating element E can improve the material cycle performance and thermal stability, but can increase the material DCR by a small amount.
Preparation method of monocrystal ternary positive electrode material
The monocrystal ternary positive electrode material is formed by sintering lithium salt, a precursor, a dopant (dopant A and dopant B) and a coating agent (coating agent C and coating agent D).
The lithium source may be one or more selected from lithium hydroxide, lithium carbonate, lithium acetate, lithium oxalate, and the like. The lithium source may be a hydrated lithium source such as LiOH H 2 O。
The precursor suitable for the invention is nickel cobalt manganese hydroxide precursor, and the chemical formula is Ni x Co y Mn 1-x-y (OH) 2 Wherein x is more than or equal to 0.5 and less than or equal to 0.8, and y is more than 0 and less than or equal to 0.15. In some embodiments, 0.55.ltoreq.x.ltoreq.0.7. In some embodiments, 0.05.ltoreq.y.ltoreq.0.12. The single crystal ternary positive electrode material of the invention is preferably a low cobalt material, so that y is preferably more than 0 and less than or equal to 0.1. In some embodiments, 0.6.ltoreq.x.ltoreq.0.7, 0.05.ltoreq.y.ltoreq.0.1, e.g., x=0.65, y=0.07. Precursors suitable for use in the present invention may be prepared using methods known in the art or provided by the present invention, for example, comprising the steps of: respectively dissolving Ni acid salt, co acid salt and Mn acid salt in deionized water, mixing the aqueous solution with ammonia water, controlling pH value to be 9-12, reacting at the constant temperature of 60-80 ℃ for 5-12h, cooling to 25-30 ℃ after the reaction is finished, filtering and drying to obtain a precursor.
The molar ratio of the metal element (i.e., the sum of nickel, cobalt, manganese) in the nickel cobalt manganese hydroxide precursor to lithium in the lithium source may be 1 (1-1.1), preferably 1 (1.03-1.07), for example 1:1.04.
The preparation method of the monocrystal ternary positive electrode material comprises the following steps:
(1) Mixing a nickel cobalt manganese hydroxide precursor, a lithium source, a doping agent A and a doping agent B to obtain uniformly mixed solid powder;
(2) Sintering the solid powder obtained in the step (1) to obtain a monocrystal ternary anode material to be coated;
(3) Crushing the single crystal ternary cathode material to be coated obtained in the step (2) to obtain a crushed ternary cathode material;
(4) Mixing the crushed ternary cathode material obtained in the step (3) with a coating agent containing a coating element to obtain a coating material;
(5) And (3) sintering the coating material obtained in the step (4) to obtain the coated monocrystal ternary anode material.
In some preferred embodiments, the method for preparing a single crystal ternary cathode material of the invention comprises a two-step coating, i.e. after the aforementioned step (3), further comprises the steps of:
(4') mixing the crushed ternary cathode material obtained in the step (3) with a coating agent C to obtain a first coating material;
(5 ') sintering the first coating material obtained in the step (4') to obtain a primary coated single crystal ternary anode material;
(6 ') mixing the primary coated ternary cathode material obtained in the step (5') with a coating agent D to obtain a second coating material;
and (7 ') sintering the second coating material obtained in the step (6') to obtain the secondary coated single crystal ternary anode material.
In the step (1), the materials are mixed in a dry high-speed mixing mode, and the mixing process is preferably as follows: mixing at 200-300r/min for 3-8min, and then mixing at 600-800r/min for 20-30min at high speed. Mixing can be performed using a high speed mixer. In the present invention, high-speed mixing means a mixing method in which a mixing process includes a step of mixing at a rotation speed of 600r/min or more; the dry mixing (coating) is a mixing (coating) method in which a liquid dispersing agent such as water is not added during the mixing. In step (1), the dopant A is preferably Nb 2 O 5 . The dopant B may be an oxide and/or hydroxide of the doping element B.
In the step (2), the solid powder is sintered for the first time to obtain the doped modified monocrystal ternary anode material. The sintering procedure is preferably sintering at 900-980 ℃ for 8-16 hours. The temperature rising rate can be 1.5-3 ℃/min. Sintering may be performed in an oxygen or oxygen-air mixed atmosphere. Preferably, the volume fraction of oxygen in the sintering atmosphere is not less than 70%, for example not less than 80%, notless than 90%, notless than 95%.
In some embodiments, the single crystal ternary cathode material obtained in step (2) is a single particle single crystal having a primary particle average particle size of between 1.5 and 2.5 μm, preferably between 1.8 and 2.3 μm. It will be appreciated that the coating and sintering process after step (2) does not have a substantial effect on the grain size and distribution characteristics of the single crystals, and therefore it is believed that the grain size and distribution of the single crystals obtained after step (2) doped sintering are consistent with the grain size and distribution of the single crystals of the final positive electrode material product. In some embodiments, the number of primary particles having a particle size of less than 1.0 μm in the single crystal ternary cathode material obtained in step (2) is not more than 2%, while the average particle size of the primary particles having a particle size of more than 1.0 μm is not more than 2.2 μm, and the absolute value of the distribution bias of the particle sizes of 500 or more primary particles is counted to be less than 0.6. Herein, the distribution Skewness (Shewness) is a measure of the Skew direction and degree of the distribution of statistical data commonly used in statistics, and is a numerical feature of the degree of asymmetry of the distribution of statistical data, and its calculation formula is Shew (X) =E [ (X- μ) 3 /σ) 3 ]. The present invention controls the particle diameter of single crystal particles within the above range by adding the dopant a and controlling the sintering conditions. The particle size of the monocrystalline particles meets the requirements, so that the uniformity of the primary particles is high, and the thermal stability and long-cycle stability of the material under the high-temperature condition are improved.
In the step (2), the sintering process may be performed at a relatively low temperature for several hours, for example, the sintering temperature may be 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, or any value between the above temperature values, the sintering time may be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any value between the above time values, and then sintering is performed at 900 ℃ to 980 ℃ for 10 to 16 hours.
In the step (3), crushing can be performed by adopting jaw crushing, double-roller coarse crushing, fine crushing and sieving.
In the step (4), the step (4 ') and the step (6'), high-speed mixing is performed by adopting a dry coating method, and the surface of the positive electrode material is coated with the coating agent while mixing. The mixing (cladding) process is preferably: mixing at 200-300r/min for 1-5min, and then mixing at 600-800r/min for 10-20min. Mixing can be performed using a high speed mixer. In step (4'), a coating agent C containing a coating element C is added. The coating agent C may be an oxide and/or hydroxide of the coating element C. In step (6'), a coating agent D containing a coating element D is added. The coating agent D is a boron-containing compound other than boric acid and boron oxide, preferably selected from B 2 Co 3 H 6 、B 2 Co 3 O 6 And AlB 4 One or more of the following. In step (6'), a coating agent E containing a coating element E may optionally be added.
In the step (5), the coating material is sintered for the second time to obtain the anode material with the coating layer. The conditions for the second sintering are preferably: the sintering time is 5-12 h, and the sintering temperature is 150-650 ℃. The temperature rising rate can be 1.5-3 ℃/min.
In the step (5'), the first coating material is sintered for the second time to obtain the primary coated positive electrode material with the first coating layer. The conditions for the second sintering are preferably: the sintering time is 5-12 h, and the sintering temperature is 500-650 ℃. The temperature rising rate can be 1.5-3 ℃/min.
In the step (7'), the second coating material is subjected to third sintering to obtain a secondary coated positive electrode material having a first coating layer and a second coating layer. The conditions for the third sintering are preferably: the sintering time is 5-12 h, and the sintering temperature is 150-500 ℃. The temperature rising rate can be 1.5-3 ℃/min.
And (5) sieving after sintering to obtain a final product.
In the invention, the first coating layer and the second coating layer are continuously and lamellar coated by a dry high-speed mixing coating process. The invention adopts double-layer cladding, the first layer and the second layer are continuous lamellar cladding, so that a compact cladding layer can be more effectively formed, and side reaction of electrolyte and materials is reduced.
The invention also comprises a positive plate containing the monocrystal ternary positive electrode material, a lithium ion battery containing the positive plate and a lithium ion battery cell.
The lithium ion battery comprises an electric core and electrode liquid. The lithium ion battery cell comprises a positive pole piece, a negative pole piece and a diaphragm. And laminating or winding (such as Z-shaped lamination or winding lamination) the positive plate, the negative plate and the diaphragm according to design requirements to obtain the battery core of the lithium ion battery.
The positive plate comprises a positive current collector and a positive material layer formed on the surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode material layer is obtained by coating positive electrode slurry containing positive electrode active material, conductive agent, binder and solvent on a positive electrode current collector, rolling and baking. The positive electrode current collector may be copper foil, aluminum foil, titanium foil, nickel foil, iron foil, zinc foil, or the like. The solvent of the positive electrode slurry may be N-methylpyrrolidone (NMP). In the positive electrode sheet of the present invention, the positive electrode active material contains the single crystal ternary positive electrode material of the present invention. The conductive agent of the positive electrode may be one or more selected from conductive carbon black (SP), carbon Fiber (CF), acetylene black, conductive graphite, graphene, carbon nanotube, and carbon microsphere. The binder of the positive electrode may be one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyvinyl alcohol, polyolefin, styrene-butadiene rubber, fluorinated rubber, polyurethane, and sodium alginate. In some embodiments, the conductive agent in the positive electrode material layer is SP and the binder is PVDF. The content ratio of each component in the positive electrode material layer may be conventional, for example, the mass fraction of the positive electrode active material may be 90% -98%, for example 92%, 94%, 96%, 96.7%, 97%, the mass fraction of the conductive agent may be 1% -5%, for example 1.2%, 1.5%, 2%, 3%, 3.5%, 4%, and the mass fraction of the binder may be 1% -5%, for example 1.5%, 1.8%, 2%, 2.5%, 3%, 4%.
The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer formed on a surface of the negative electrode current collector. The negative electrode current collector may be copper foil. The anode material layer includes an anode active material, a conductive agent, and a binder. The negative electrode material layer is obtained by coating a negative electrode slurry containing a negative electrode active material, a conductive agent, a binder and a solvent on a positive electrode current collector, and then rolling and baking the positive electrode current collector. The solvent of the anode slurry may be water. The anode active material may be one or more selected from a carbon material (e.g., graphite), silicon, a compound of silicon, lithium titanate, tin, and a compound of tin. The negative electrode conductive agent may be one or more selected from conductive carbon black (SP), acetylene black, carbon nanotubes, carbon nanowires, carbon microspheres, carbon fibers, and graphene. The negative electrode binder may be one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, acrylonitrile copolymer, polybutyl acrylate, polyacrylonitrile, and Styrene Butadiene Rubber (SBR). The anode material layer and the anode slurry may further contain a thickener such as sodium carboxymethyl cellulose (CMC). In some embodiments, the negative electrode active material in the negative electrode material layer is graphite, the conductive agent is conductive carbon black, the binder is styrene-butadiene rubber, and the thickener is sodium carboxymethyl cellulose. The mass ratio of each component in the anode material layer may be conventional, for example, the mass fraction of the anode active material may be 90% to 98%, for example 93%, 95%, 95.7%, 96%, 97%, the mass fraction of the conductive agent may be 0.5% to 5%, for example 1%, 1.5%, 2%, the mass fraction of the binder may be 0.5% to 5%, for example 1%, 1.5%, 2%, 3%, and the mass fraction of the thickener may be 0 to 5%, for example 1%, 1.5%, 1.8%, 2%, 3%.
The separator may be a polymer porous separator, an inorganic porous separator, or a polymer-inorganic composite porous separator. The polymeric porous separator includes a single layer polymeric porous separator and a multi-layer polymeric porous separator. The polymer membrane may be PE, PP, etc.
And after the battery cell is obtained, packaging the battery cell in a shell, and drying, injecting liquid (injecting electrolyte), packaging, standing, forming and sorting to obtain the lithium ion battery. The form of the lithium ion battery of the present invention is not particularly limited, and may be a cylindrical lithium ion battery, a soft pack lithium ion battery, an aluminum case lithium ion battery, or the like.
The lithium ion battery electrolyte comprises an organic solvent and a lithium salt. Commonly usedThe organic solvent in the electrolyte is carbonate solvent. Suitable carbonate solvents include, but are not limited to, one or more, preferably two or more, selected from the group consisting of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC). Preferably, the carbonate-based solvent comprises at least one cyclic carbonate and at least one chain carbonate. Examples of cyclic carbonates include EC, PC and butylene carbonate. The lithium salt in the electrolyte of the present invention may be a lithium salt commonly used in the art, including but not limited to lithium hexafluorophosphate (LiPF) 6 ) Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiLiFSI), lithium bis (oxalato) borate (LiBOB), lithium difluorooxalato borate (LiODFB), lithium tetrafluoroborate (LiBF) 4 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium perchlorate (LiClO) 4 ) Lithium fluoride (LiF), lithium triflate (LiCF) 3 SO 3 ) Etc. In some embodiments, the lithium salt is LiPF 6 . The concentration of the lithium salt in the electrolyte may be 0.5 to 2mol/L, for example 1mol/L.
Compared with the prior art, the invention has the following beneficial effects:
1. the preparation method is friendly to industrial production;
2. the invention uses the doping element Nb to improve the internal structure of the crystal, improve the particle consistency of primary particles and improve the thermal stability and the cycle performance of the material under the high-temperature condition;
3. the coating adopts double-layer coating, the first layer and the second layer are continuous lamellar coating, a compact coating layer is formed, and side reaction of electrolyte and materials is reduced.
The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods, reagents and materials used in the examples are those conventional in the art unless otherwise indicated. The starting compounds in the examples are all commercially available.
Example 1
The preparation method of the high-performance ternary positive electrode material comprises the following steps:
(1) Accurately weighing lithium salt, a precursor, a doping agent A and a doping agent B respectively, wherein the molar ratio (Li/Me) =1.04:1 of lithium element (Li) to metal element (Me) in the precursor, and the lithium salt is LiOH.H 2 O, the precursor is Ni 0.65 Co 0.07 Mn 0.28 (OH) 2 Dopant A is Nb 2 O 5 The dosage of the doping agent A is controlled to be 1000ppm of Nb element, and the doping agent B is Y 2 O 5 The dosage of the doping agent B is controlled to 2500ppm, all the lithium salt, the precursor, the doping agent A and the doping agent B are added into a mixer, mixed for 5min at 300r/min, and then mixed for 30min at high speed 800r/min, so as to obtain uniformly mixed solid powder;
(2) Calcining solid powder at 970 ℃ for 12 hours at a temperature rising rate of 3 ℃/min in a calcining stage, sintering by using pure oxygen, wherein the oxygen concentration in the sintering atmosphere is more than 95%, and cooling to obtain a monocrystal ternary anode material;
(3) Crushing the sintered material, crushing the material by a pair of rollers, crushing the material by fine powder, and sieving the crushed material to obtain a crushed ternary anode material;
(4) Adding the crushed material and the coating agent C into a high-speed mixer at the same time, and mixing at high speed in a dry coating mode to obtain a coating material containing a plurality of coating agents, wherein the coating agent C is V 2 O 5 And CeO 2 The addition amount of V element is 1000ppm, and the addition amount of Ce element is 1000ppm;
(5) The coated material is subjected to secondary sintering at 580 ℃ for 8 hours, the heating rate is set to be 3 ℃/min, and the single crystal ternary anode material is obtained after cooling;
(6) Simultaneously adding the material obtained in the step (5), the coating agent D and the coating agent E into a high-speed mixer, carrying out high-speed mixing and secondary coating in a dry coating mode, wherein the coating process is that 300r/min is mixed for 5min, then 800r/min is mixed for 15min, and the coating agent D is B 2 Co 3 H 6 Wherein the coating amount of the element B is 600ppm, and the coating agent E is AlH 6 P 3 O 12 Elemental AlThe coating amount of (2) was 1500ppm;
(7) And (3) carrying out heat preservation on the materials for 6 hours at 400 ℃ under the sintering condition for three times, setting the heating rate to 3 ℃/min, and sieving to obtain the final product.
Example 2
The method for preparing the high-performance ternary cathode material comprises the following steps of:
(1) Accurately weighing lithium salt, a precursor, a doping agent A and a doping agent B respectively, wherein the molar ratio (Li/Me) =1.06:1 of lithium element (Li) to metal element (Me) in the precursor, and the lithium salt is LiOH.H 2 O, the precursor is Ni 0.65 Co 0.07 Mn 0.28 (OH) 2 Dopant A is Nb 2 O 5 The dosage of the doping agent A is controlled to be 1500ppm, and the doping agent B is ZrO 2 The dosage of the doping agent B is 2200ppm of the adding amount of Zr element, all the lithium salt, the precursor, the doping agent A and the doping agent B are added into a mixer, mixed for 5min at 300r/min, and then mixed for 30min at high speed 800r/min, so as to obtain uniformly mixed solid powder;
(2) Calcining the solid powder at 965 ℃ for 12 hours at a temperature rising rate of 3 ℃/min in a calcining stage, sintering by using pure oxygen, wherein the oxygen concentration in the sintering atmosphere is more than 95%, and cooling to obtain the monocrystal ternary anode material;
(3) Crushing the sintered material, crushing the material by a pair of rollers, crushing the material by fine powder, and sieving the crushed material to obtain a crushed ternary anode material;
(4) The crushed materials and the coating agent C are simultaneously added into a high-speed mixer, and are mixed at high speed in a dry coating mode to obtain a coating material containing a plurality of coating agents, wherein the coating agent C is CeO 2 The addition amount of Ce element is 1500ppm;
(5) The coated material is subjected to secondary sintering at 550 ℃ for 8 hours, the heating rate is set to be 3 ℃/min, and the single crystal ternary anode material is obtained after cooling;
(6) The material obtained in the step (5), the coating agent D and the coating agent E are simultaneously added into a high-speed mixer, high-speed mixing and secondary coating are carried out by adopting a dry coating mode, The coating process comprises mixing at 300r/min for 5min, and mixing at high speed of 800r/min for 15min, wherein the coating agent D is B 2 Co 3 O 6 Wherein the coating amount of the element B is 800ppm, the coating agent E is ZnO, and the coating amount of the element Zn is 500ppm;
(7) And (3) carrying out heat preservation on the materials for 6 hours under the sintering condition at 420 ℃ for three times, setting the heating rate to be 3 ℃/min, and sieving to obtain a final product.
Example 3
The preparation method of the high-performance ternary positive electrode material comprises the following steps:
(1) Accurately weighing lithium salt, a precursor, a doping agent A and a doping agent B respectively, wherein the molar ratio (Li/Me) =1.04:1 of lithium element (Li) to metal element (Me) in the precursor, and the lithium salt is LiOH.H 2 O, the precursor is Ni 0.65 Co 0.07 Mn 0.28 (OH) 2 Dopant A is Nb 2 O 5 The dosage of the doping agent A is controlled to be 1000ppm of Nb element, and the doping agent B is Y 2 O 5 The dosage of the doping agent B is controlled to 2500ppm, all the lithium salt, the precursor, the doping agent A and the doping agent B are added into a mixer, mixed for 5min at 300r/min, and then mixed for 30min at high speed 800r/min, so as to obtain uniformly mixed solid powder;
(2) Calcining solid powder at 970 ℃ for 12 hours at a temperature rising rate of 3 ℃/min in a calcining stage, sintering by using pure oxygen, wherein the oxygen concentration in the sintering atmosphere is more than 95%, and cooling to obtain a monocrystal ternary anode material;
(3) Crushing the sintered material, crushing the material by a pair of rollers, crushing the material by fine powder, and sieving the crushed material to obtain a crushed ternary anode material;
(4) The crushed materials and the coating agent C are simultaneously added into a high-speed mixer, and are mixed at high speed in a dry coating mode to obtain a coating material containing a plurality of coating agents, wherein the coating agent C is ZnO and SnO 2 The amount of Zn element added is 500ppm, and the amount of Sn element added is 2000ppm;
(5) The coated material is subjected to secondary sintering at 580 ℃ for 6.5 hours, the heating rate is set to be 3 ℃/min, and the single crystal ternary anode material is obtained after cooling;
(6) Adding the material obtained in the step (5), the coating agent D and the coating agent E into a high-speed mixer at the same time, carrying out high-speed mixing and secondary coating in a dry coating mode, wherein the coating process is that 300r/min is mixed for 5min, then 800r/min is mixed for 15min, and the coating agent D is AlB 4 Wherein the coating amount of the element B is 1000ppm, and the coating agent E is Mg (OH) 2 The amount of elemental Mg is 1000ppm;
(7) And (3) carrying out heat preservation on the materials for 8 hours at 360 ℃ under the sintering condition for three times, setting the heating rate to 3 ℃/min, and sieving to obtain the final product.
Example 4
The preparation method of the high-performance ternary positive electrode material comprises the following steps:
(1) Accurately weighing lithium salt, a precursor, a doping agent A and a doping agent B respectively, wherein the molar ratio (Li/Me) =1.04:1 of lithium element (Li) to metal element (Me) in the precursor, and the lithium salt is LiOH.H 2 O, the precursor is Ni 0.65 Co 0.07 Mn 0.28 (OH) 2 Dopant A is Nb 2 O 5 The dosage of the doping agent A is controlled to be 1000ppm of Nb element, and the doping agent B is Y 2 O 5 The dosage of the doping agent B is controlled to 2500ppm, all the lithium salt, the precursor, the doping agent A and the doping agent B are added into a mixer, mixed for 5min at 300r/min, and then mixed for 30min at high speed 800r/min, so as to obtain uniformly mixed solid powder;
(2) Calcining solid powder at 970 ℃ for 12 hours at a temperature rising rate of 3 ℃/min in a calcining stage, sintering by using pure oxygen, wherein the oxygen concentration in the sintering atmosphere is more than 95%, and cooling to obtain a monocrystal ternary anode material;
(3) Crushing the sintered material, crushing the material by a pair of rollers, crushing the material by fine powder, and sieving the crushed material to obtain a crushed ternary anode material;
(4) Adding the crushed material and the coating agent C into a high-speed mixer at the same time, and mixing at high speed in a dry coating mode to obtain a coating material containing a plurality of coating agents, wherein the coating agent C is V 2 O 5 And CeO 2 The addition amount of V element is 1000ppm, and the addition amount of Ce element is 1000ppm;
(5) The coated material is subjected to secondary sintering at 580 ℃ for 8 hours, the heating rate is set to be 3 ℃/min, and the single crystal ternary anode material is obtained after cooling;
(6) Simultaneously adding the material obtained in the step (5) and a coating agent D into a high-speed mixer, carrying out high-speed mixing and secondary coating in a dry coating mode, wherein the coating process is that 300r/min is mixed for 5min, then the high-speed 800r/min is mixed for 15min, and the coating agent D is B 2 Co 3 H 6 Wherein the coating amount of the element B is 600ppm;
(7) And (3) carrying out heat preservation on the materials for 6 hours at 400 ℃ under the sintering condition for three times, setting the heating rate to 3 ℃/min, and sieving to obtain the final product.
Example 5
The preparation method of the high-performance ternary positive electrode material comprises the following steps:
(1) Accurately weighing lithium salt, a precursor, a doping agent A and a doping agent B respectively, wherein the molar ratio (Li/Me) =1.04:1 of lithium element (Li) to metal element (Me) in the precursor, and the lithium salt is LiOH.H 2 O, the precursor is Ni 0.65 Co 0.07 Mn 0.28 (OH) 2 Dopant A is Nb 2 O 5 The dosage of the doping agent A is controlled to be 1000ppm of Nb element, and the doping agent B is TiO 2 And MgO (MgO) 2 The dosage of the doping agent B is that the adding amount of Ti element is controlled to be 2000ppm, the adding amount of Mg element is controlled to be 1500ppm, all lithium salt, precursor, doping agent A and doping agent B are added into a mixer, mixed for 5min at 300r/min, and then mixed for 30min at high speed of 800r/min, so as to obtain uniformly mixed solid powder;
(2) Calcining solid powder at 970 ℃ for 12 hours at a temperature rising rate of 3 ℃/min in a calcining stage, sintering by using pure oxygen, wherein the oxygen concentration in the sintering atmosphere is more than 95%, and cooling to obtain a monocrystal ternary anode material;
(3) Crushing the sintered material, crushing the material by a pair of rollers, crushing the material by fine powder, and sieving the crushed material to obtain a crushed ternary anode material;
(4) Adding the crushed material and the coating agent C into a high-speed mixer at the same time, and mixing at high speed in a dry coating mode to obtain a coating material containing a plurality of coating agents, wherein the coating agent C is V 2 O 5 And CeO 2 The addition amount of V element is 1000ppm, and the addition amount of Ce element is 1000ppm;
(5) The coated material is subjected to secondary sintering at 580 ℃ for 8 hours, the heating rate is set to be 3 ℃/min, and the single crystal ternary anode material is obtained after cooling;
(6) Simultaneously adding the material obtained in the step (5), the coating agent D and the coating agent E into a high-speed mixer, carrying out high-speed mixing and secondary coating in a dry coating mode, wherein the coating process is that 300r/min is mixed for 5min, then 800r/min is mixed for 15min, and the coating agent D is B 2 Co 3 H 6 Wherein the coating amount of the element B is 600ppm, and the coating agent E is AlH 6 P 3 O 12 The coating amount of the element Al is 1500ppm;
(7) And (3) carrying out heat preservation on the materials for 6 hours at 400 ℃ under the sintering condition for three times, setting the heating rate to 3 ℃/min, and sieving to obtain the final product.
Comparative example 1
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: no dopant a was added.
Comparative example 2
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: the addition of dopant A controls the mass fraction of Nb element to 3000ppm.
Comparative example 3
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: in the primary sintering of the step (2), the oxygen concentration in the sintering atmosphere is 21.5%.
Comparative example 4
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: the coating agent C is Nb 2 O 5 The mass fraction of the element Nb was 2500ppm, and secondary coating was not performed subsequently.
Comparative example 5
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: in the secondary sintering in the step (5), the constant temperature time is 3h.
Comparative example 6
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: the coating agent D is B 2 O 3 。
Comparative example 7
This comparative example produces a ternary positive electrode material that differs from example 1 only in that: in the three-time sintering in the step (7), the constant temperature is 600 ℃.
Test example 1
The morphology of the positive electrode material obtained in example 1 and comparative example 1 was observed using SEM, and the results are shown in fig. 2 and 3, and statistics of the SEM next particle size thereof are shown in table 1, fig. 4 and fig. 5.
As can be seen from fig. 4 and 5, the primary particle size of the positive electrode material obtained in example 1 is nearly normally distributed, whereas the primary particle size deviation of the positive electrode material obtained in comparative example 1 is relatively large.
As can be seen from fig. 2-5 and table 1: the use of the doping agent A can effectively improve the uniformity and roundness of the primary particle size, further reduce the contact area with electrolyte, and improve the high-temperature storage gas production performance and the increase of the Direct Current Resistance (DCR) in the circulation process.
Table 1: example 1 and comparative example 1 particle size statistics of cathode materials
Test example 2
Examples 1-5 and comparative example 6 were tested to obtain surface hydroxyl groups of the positive electrode material, and the results are shown in Table 3.
In the invention, the following general method in the industry is adopted to measure the surface hydroxyl of the positive electrode material: and titrating the solution of the ternary positive electrode material by using hydrochloric acid, and judging the contents of carbonate and hydroxide in the solution through two inflection points of a pH curve.
As can be seen from table 3: through screening the coating agent containing B element, the boron-containing compound other than boric acid or boric oxide is used as the coating agent D, so that the content of lithium hydroxide on the surface of the positive electrode material can be effectively reduced, and the processing performance and the gas production performance of the positive electrode material are improved.
Table 2: surface hydroxyl content of the cathode materials of examples 1 to 4 and comparative example 6
Project Surface hydroxyl content
Example 1 0.0456wt％
Example 2 0.0478wt％
Example 3 0.0502wt％
Example 4 0.0499wt％
Example 5 0.0512wt％
Comparative example 6 0.1250wt％
Test example 3
The morphology of the cathode material before coating in example 1, the cathode material after coating and sintering twice in example 1, the cathode material after coating and sintering once in example 1, and comparative example 4 was observed using SEM, and the results are shown in fig. 6, 7, 8, and 9, respectively.
As can be seen from fig. 6-9: the coating layer of the positive electrode material after the primary coating of comparative example 4 was island-shaped, which indicates that Nb was used 2 O 5 Continuous lamellar coating cannot be achieved as a coating agent; the surface of the positive electrode material after the primary coating and the secondary coating of example 1 showed a relatively uniform continuous layer, which indicates that the first coating layer and the second coating layer of the positive electrode material of example 1 were both continuous layer coatings. The anode material of the embodiment 1 can effectively improve the problems of interface side reaction, transition metal ion dissolution and the like through continuous lamellar coating of two layers, thereby improving the cycle performance and the thermal stability of the material.
Test example 4
Preparation of CR2032 coin cell using positive electrode material for charge and discharge testing and cycle performance testing:
At 95:2.5:2.5 the single crystal ternary cathode materials obtained in the examples 1 to 5 or the comparative examples 1 to 7, the conductive agent Super P and the binder PVDF are respectively weighed according to the mass ratio, placed in a stirrer, dropwise added with a proper amount of NMP, stirred until slurry is uniform, then uniformly coated on aluminum foil, placed in a vacuum oven, dried at 130 ℃ for 5 hours, and filled into 14mm round cathode plates for standby. And assembling the positive plate, the lithium plate and 1mol/L LiPF6 electrolyte (the solvent is a mixed solution of diethyl carbonate and ethyl cellulose in a volume ratio of 1:1) into a CR2032 button cell in a diaphragm glove box, and performing charge and discharge and cycle test by using a LAND test system after standing for 10 hours. The primary discharge specific capacity, primary coulombic efficiency, charge-discharge rate during cycling of each CR2032 type button cell at 25℃and a voltage interval of 2.8 to 4.35V and a charge-discharge rate of 0.1C/0.1C were measured for a 50-cycle retention rate, a 50% SOC DCR, and a thickness increase in the hot state at 1C/1C, and the measurement results are shown in Table 3.
Table 3: results of charge-discharge and cycle performance test
It can be seen from example 1 and comparative example 1 that the doping of Nb element can effectively improve the cycle and gas production properties of the material.
As can be seen from example 1 and comparative example 2, the doping amount of Nb element needs to be controlled within a reasonable range, and excessive doping generates rock salt-like substances on the crystal surface, thereby drastically deteriorating the DCR performance of the cathode material.
As can be seen from example 1 and comparative example 3, the primary sintering of the positive electrode material needs to be performed under an oxygen atmosphere with a certain concentration, and for example, the air process is selected to cause degradation of various properties of the positive electrode material.
It can be seen from example 1 and comparative examples 4 and 5 that the primary coating requires the selection of appropriate elements and sintering time, which would otherwise have a large negative impact on the recycling and gas production properties of the cathode material.
As can be seen from example 1 and comparative example 6, the secondary coating requires more caution in selecting the B element-containing compound, and there are adverse effects of deterioration in DCR and gas production, etc., compared with the B element-containing compound of the examples, coating with boric acid or boron oxide.
It can be seen from example 1 and comparative example 7 that sintering temperatures too high after secondary coating result in a decrease in energy density.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The single crystal ternary positive electrode material is characterized in that the single crystal ternary positive electrode material is a nickel cobalt lithium manganate positive electrode material doped with doping elements A and B and coated with coating elements on the surface;
the doped element A is Nb element, the doped element B is one or more elements selected from Al, mg, zr, ti, Y, cr, sn and W, and the cladding element is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, B, W and Nb.
2. The single crystal ternary cathode material of claim 1, wherein the doping element a is added in an amount of 0.01wt% to 0.15wt%, and/or the doping element B is added in an amount of 0.05wt% to 0.5wt%.
3. The single crystal ternary cathode material of claim 1, wherein the single crystal ternary cathode material comprises a first cladding layer and a second cladding layer located within and on the surface of the single crystal ternary cathode material, respectively, the cladding elements comprising cladding element C and cladding element D, the cladding element C being present in the first cladding layer and the cladding element D being present in the second cladding layer;
wherein the coating element C is one or more elements selected from Mg, ti, al, Y, zn, sn, fe, ce, V, co, and the coating element D is B.
4. The single crystal ternary cathode material of claim 3, wherein,
the addition amount of the coating element C is 0.05-0.25 wt%; and/or
The addition amount of the coating element D is 0.02-0.25 wt%.
5. The single crystal ternary cathode material of claim 1, wherein the single crystal ternary cathode material comprises,
the primary particles of the single crystal ternary positive electrode material have an average particle diameter of 1.5-2.5 mu m, preferably 1.8-2.3 mu m; and/or
The number of primary particles with the particle size smaller than 1.0 mu m in the single crystal ternary positive electrode material is not more than 2%; and/or
The average particle diameter of primary particles with the particle diameter of more than 1.0 mu m in the single crystal ternary positive electrode material is not more than 2.2 mu m; and/or
Counting the absolute value of the distribution deviation of the particle sizes of more than 500 primary particles in the monocrystal ternary positive electrode material to be less than 0.6; and/or
The surface hydroxyl content of the monocrystal ternary anode material is less than 0.06wt%.
6. A method of preparing the single crystal ternary cathode material of any one of claims 1-5, comprising the steps of:
(1) Mixing a nickel cobalt manganese hydroxide precursor, a lithium source, a doping agent A containing a doping element A and a doping agent B containing a doping element B to obtain uniformly mixed solid powder;
(2) Sintering the solid powder obtained in the step (1) to obtain a monocrystal ternary anode material to be coated;
(3) Crushing the single crystal ternary cathode material to be coated obtained in the step (2) to obtain a crushed ternary cathode material;
(4) Mixing the crushed ternary cathode material obtained in the step (3) with a coating agent containing a coating element to obtain a coating material;
(5) And (3) sintering the coating material obtained in the step (4) to obtain the coated monocrystal ternary anode material.
7. The method according to claim 6, characterized in that the method comprises the steps of:
(1) Mixing a nickel cobalt manganese hydroxide precursor, a lithium source, a doping agent A containing a doping element A and a doping agent B containing a doping element B to obtain uniformly mixed solid powder;
(2) Sintering the solid powder obtained in the step (1) to obtain a monocrystal ternary anode material to be coated;
(3) Crushing the single crystal ternary cathode material to be coated obtained in the step (2) to obtain a crushed ternary cathode material;
(4') mixing the crushed ternary cathode material obtained in the step (3) with a coating agent C containing a coating element C to obtain a first coating material;
(5 ') sintering the first coating material obtained in the step (4') to obtain a primary coated single crystal ternary anode material;
(6 ') mixing the primary coated ternary cathode material obtained in the step (5') with a coating agent D containing a coating element D to obtain a second coating material;
and (7 ') sintering the second coating material obtained in the step (6') to obtain the secondary coated single crystal ternary anode material.
8. The method of claim 6 or 7, wherein the method has one or more of the following features:
in the step (1), the materials are mixed in a dry high-speed mixing mode, and the mixing process is preferably as follows: firstly mixing for 3-8min at 200-300r/min, and then mixing for 20-30min at 600-800r/min at high speed;
in step (1), the dopant A is Nb 2 O 5 And/or the dopant B is an oxide and/or hydroxide of the doping element B;
in the step (2), the sintering procedure comprises the step of sintering at 900-980 ℃ for 8-16 hours;
in the step (2), the volume fraction of oxygen in the sintering atmosphere is more than or equal to 70%;
in the step (4) or the step (4 ') or the step (6'), the high-speed mixing is performed by adopting a dry coating mode, and the mixing process is preferably as follows: firstly mixing for 1-5min at 200-300r/min, and then mixing for 10-20min at 600-800r/min at high speed;
in the step (4'), the coating agent C is an oxide and/or hydroxide of the coating element C;
In the step (5), the sintering time is 5-12 h, and the sintering temperature is 150-650 ℃;
in the step (5'), the sintering time is 5-12 h, and the sintering temperature is 500-650 ℃;
in step (6'), the coating agent D is a boron-containing compound other than boric acid and boron oxide, preferably B 2 Co 3 H 6 、B 2 Co 3 O 6 And/or AlB 4 ；
In the step (7'), the sintering time is 5-12 h, and the sintering temperature is 150-500 ℃.
9. A positive electrode sheet comprising the single crystal ternary positive electrode material according to any one of claims 1 to 5 or the single crystal ternary positive electrode material produced by the method according to any one of claims 6 to 8.
10. A lithium ion battery or lithium ion battery cell comprising the positive electrode sheet of claim 9.
CN202211210504.7A 2022-09-30 2022-09-30 Low-gas-yield long-cycle monocrystal ternary cathode material and preparation method thereof Pending CN117855400A (en)

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