CN111668476A - Polycrystalline ternary positive electrode material and preparation method and application thereof - Google Patents

Polycrystalline ternary positive electrode material and preparation method and application thereof Download PDF

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CN111668476A
CN111668476A CN202010518269.4A CN202010518269A CN111668476A CN 111668476 A CN111668476 A CN 111668476A CN 202010518269 A CN202010518269 A CN 202010518269A CN 111668476 A CN111668476 A CN 111668476A
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cathode material
source
polycrystalline
ternary cathode
lithium
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宋鹏元
林文佳
曾汉民
何巍
刘金成
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Eve Energy Co Ltd
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Eve Energy Co Ltd
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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
    • 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
    • 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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • 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
    • H01M4/52—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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a polycrystalline ternary cathode material and a preparation method and application thereof. The polycrystalline ternary cathode material comprises secondary particles formed by stacking single crystal primary particles, wherein the single crystal primary particles are mutually contacted to form a crystal boundary, and boron elements are distributed on the crystal boundary. The boron element and the nickel element have high-strength B-O-Ni chemical bonds, so that the acting force between single crystal primary particles is strong, the damage of contact between the single crystal primary particles caused by anisotropic volume change is relieved, and the structural stability is good. The polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, has the advantages of reducing the cracking phenomenon and having excellent cycle performance in the use process.

Description

Polycrystalline ternary positive electrode material and preparation method and application thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a polycrystalline ternary cathode material and a preparation method and application thereof.
Background
The lithium ion battery has the characteristics of high energy density and power density, long cycle life and low pollution, and is widely applied to electronic equipment and new energy automobiles. The positive electrode material, which is a key component of a lithium ion battery, receives a great deal of attention because the quality of its performance directly affects the capacity, service life and safety of the lithium ion battery.
Compared with other anode materials, the ternary anode material has the characteristics of good cycle performance, high capacity, good overcharge resistance, easiness in synthesis, high cost performance and the like, and becomes a preferred anode material of the lithium ion battery, particularly a high-nickel ternary anode material. However, these materials also suffer from a number of disadvantages. For example, during charging, anisotropic volume changes can generate internal stress, which is prone to cracking and breaking, and further causes the problems of rapid increase of direct current discharge resistance (DCR) and severe gas generation during the cycle. In addition, the increase of the Ni content deteriorates the thermal stability of the material, which poses a great risk to the safety of the lithium ion battery.
The particles of the prior ternary cathode material are secondary particle balls formed by agglomeration of primary particles, and the method for improving the cracking and thermal stability of the ternary cathode material mainly comprises precursor synthesis optimization, coating and doping. The optimization of precursor synthesis mainly reduces the internal stress in the charging and discharging process by directionally growing primary particles of the material in a radial shape, thereby improving the crushing of the material. Furthermore, radial particle fragmentation generally occurs along the radial direction of the particle, and fragmentation does not occur perpendicular to the radial direction of the particle, thereby preventing some parts of the material from being unusable within the particle.
CN108269995A discloses a ternary precursor with adjustable crystal structure, a positive electrode material and a preparation method thereof, which specifically comprises the following steps: respectively preparing a nickel-cobalt-manganese soluble salt, NaOH, concentrated ammonia water and a growth-oriented surfactant into solutions, and then carrying out coprecipitation reaction to obtain a ternary precursor with a structure oriented growth; the precursor is mixed with a lithium sourceMixing, and calcining at high temperature to obtain the directionally-grown ternary layered cathode material with a precursor-like structure. The invention obtains the crystal structure along [003 ] by regulating and controlling the growth of the precursor]The anode material with directional growth improves the order degree and stability of the growth of the internal structure, reduces the mixed discharge of cations and reduces Li+Diffusion resistance, increased Li+The diffusion coefficient.
However, the above method has its limitations, and above all, similar materials are difficult to synthesize and have high cost; in addition, such materials do not avoid cracking of the material later in the test. The safety and reliability of the lithium ion battery in the later period still have great potential safety hazard.
The improvement of the coating is mainly performed by coating alumina or boron element. The aluminum oxide and boron coating can prevent the side reaction of the electrolyte and the material, and effectively improve the circulation and storage performance of the material. CN110729466A discloses a simple and efficient boron oxide coated high-nickel ternary cathode material and a preparation method thereof, wherein liquid pentaborane is added in the preparation process, the pentaborane is easily and directly and fully mixed with the material, the problem that wet coating needs solvent treatment is not considered, meanwhile, the pentaborane can be rapidly hydrolyzed to release heat when meeting water on the surface of the material, and an oxide coating layer can be formed in a very short time. However, the coating is only an improvement in the surface of the material and does not inhibit the crushing of the material. Once the material is broken, the electrolyte penetrates inside the particles and side reactions are inevitable.
The doping improvement is mainly carried out by doping the zirconium element. CN105098158A discloses a zirconium-doped lithium-rich cathode material for lithium ion batteries, the chemical formula of which is Li, and a preparation method thereof1.2(Mn0.54Ni0.13Co0.13)1-xZrxO2Wherein x is more than 0 and less than 1. The preparation method comprises the following steps: (1) dissolving lithium salt, manganese salt, nickel salt, cobalt salt and zirconium salt with stoichiometric ratio shown in chemical formula of zirconium-doped lithium ion battery lithium-rich cathode material in deionized water, adding complexing agent solution, transferring to a hydrothermal kettle for hydrothermal reaction after reaction, drying the solution, and obtaining solid powderAnd after high-temperature calcination, cooling to room temperature along with the furnace to obtain the zirconium-doped lithium-rich cathode material of the lithium ion battery. The zirconium element can improve the lattice stability of the material and inhibit the phase change of the material in the charge and discharge processes. However, the material cracks are because the contact between the particles is broken due to the anisotropic volume change between the primary particles of the single crystal, and the improvement of the stability inside the crystal lattice has no inhibiting effect on the cracking of the material.
Based on the research of the prior art, how to effectively inhibit the cracking phenomenon of the polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, in the using process becomes a technical problem to be solved urgently at present.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a polycrystalline ternary cathode material and a preparation method and application thereof. In the polycrystalline ternary cathode material, the acting force between single crystal primary particles is strong, the mutual contact damage caused by anisotropic volume change between the single crystal primary particles is slowed down, the structural stability is good, and the cycle performance is excellent.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a polycrystalline ternary cathode material, which comprises secondary particles formed by stacking single crystal primary particles, wherein the single crystal primary particles are mutually contacted to form a grain boundary, and boron is distributed in the grain boundary.
The polycrystalline ternary cathode material provided by the invention comprises secondary particles formed by stacking single crystal primary particles, boron elements are distributed on grain boundaries among the single crystal primary particles, a B-O-Ni chemical bond is formed between the boron elements and the nickel elements, the strength of the B-O-Ni chemical bond is high, the acting force among the single crystal primary particles is strong, the damage of the single crystal primary particles due to mutual contact caused by anisotropic volume change among the single crystal primary particles is effectively relieved, and the structural stability is good. The polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, effectively slows down the cracking phenomenon in the use process, and has excellent cycle performance.
Preferably, the single crystal primary particles have a particle size of 300 to 1000nm, and may be, for example, 300nm, 320nm, 350nm, 400nm, 450nm, 500nm, 600nm, 700nm, 800nm, 850nm, 900nm, 950nm, 1000nm, or the like, but are not limited to the above-mentioned values, and other values not listed in the above-mentioned range of values are also applicable, and preferably 400 to 800 nm. The preferred particle size can well give consideration to various electrical properties of the material. If the particle size is too small, the gram volume of the material is high, but the specific surface area of the material is increased, resulting in increased side reactions; if the particle size is too large, the gram volume of the material is exerted to a low extent, and the impedance of the material is increased accordingly.
Preferably, the content of boron element in percentage by mass is 0.02 to 0.5%, for example, 0.02%, 0.03%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, and preferably 0.05 to 0.25%, based on 100% by mass of the polycrystalline ternary positive electrode material.
Preferably, the lattice of the single crystal primary particles includes M element including any one of titanium element, zirconium element, aluminum element or magnesium element or a combination of at least two thereof, wherein a typical but non-limiting combination is: titanium and magnesium, zirconium and aluminum, and the like. The M element enters into crystal lattices, so that the crystal lattice stability of the polycrystalline ternary cathode material can be improved, the phase change of the polycrystalline ternary cathode material in the charge and discharge process is inhibited, and the polycrystalline ternary cathode material is preferably a zirconium element. The zirconium element is doped at a Li position to play a role of a supporting structure, and is doped at a transition metal position, so that the size of a Li layer can be increased due to a smaller ion radius, and the lithium can be removed/inserted easily; in addition, the zirconium element can inhibit Li/Ni mixed discharge.
Preferably, the content of the M element is 0.02 to 0.5% by mass, for example, 0.02%, 0.03%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5% by mass, and preferably 0.05 to 0.3% by mass, based on 100% by mass of the polycrystalline ternary positive electrode material. Preferably, the polycrystalline ternary cathode material comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate, and preferably the lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate with the nickel molar content of more than 70%. The nickel molar content is more than 70 percent, and the expression that: the molar content of nickel is more than 70 percent based on the sum of the moles of the elements in the nickel cobalt lithium manganate or the nickel cobalt lithium aluminate being 100 percent.
Preferably, the mass percentage content of the nickel element is 40-60% based on 100% of the mass of the polycrystalline ternary cathode material, for example, 40%, 42%, 45%, 50%, 55%, or 59%, and preferably 47-58%.
Preferably, the mass ratio of the nickel element to the boron element in the polycrystalline ternary cathode material is (82-2950): 1, and may be, for example, 82:1, 85:1, 100:1, 120:1, 140:1, 160:1, 165:1, 175:1, 190:1, 200:1, 250:1, 300:1, 400:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, 3000:1, 3500:1, 4000:1, and the like, and preferably is (188-1160): 1.
Preferably, the mass ratio of the nickel element to the M element in the polycrystalline ternary cathode material is (84-2950): 1, and may be, for example, 84:1, 86:1, 90:1, 100:1, 150:1, 200:1, 300:1, 400:1, 500:1, 600:1, 800:1, 1000:1, 1200:1, 1500:1, 1800:1, 2000:1, 2200:1, 2500:1 or 2950:1, and is preferably (156-1160): 1.
As a preferred embodiment of the present invention, the polycrystalline ternary positive electrode material further comprises a coating layer located on the surface of the polycrystalline ternary positive electrode material, wherein the coating layer preferably comprises any one or a combination of at least two of titania, zirconia, alumina, or magnesia, preferably alumina and/or zirconia.
According to the composite cathode material provided by the invention, the coating layer on the surface can inhibit the irreversible phase change and the dissolution of transition metal ions of the polycrystalline ternary cathode material in the charging and discharging processes. Meanwhile, the direct contact between the polycrystalline ternary positive electrode material and electrolyte can be reduced, the occurrence of side reactions is reduced, and the cycle performance of the composite material is further improved.
Preferably, typical but non-limiting combinations of said coating are: alumina and zirconia.
The thickness of the coating layer is preferably 10 to 200nm, and may be, for example, 10nm, 15nm, 20nm, 30nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm or 200nm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 30 to 100 nm.
In a second aspect, the present invention provides a method for preparing a polycrystalline ternary positive electrode material as described in the first aspect above, the method comprising the steps of:
(1) mixing a boron source and a ternary precursor, and sintering for the first time to obtain a polycrystalline ternary cathode material precursor;
(2) and (2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with a lithium source, and performing secondary sintering to obtain the polycrystalline ternary cathode material.
According to the preparation method provided by the invention, the ternary precursor comprises secondary particles consisting of primary particles, corresponding hole structures can exist among the primary particles, after the ternary precursor is mixed with a boron source, in the primary sintering process, the ternary precursor is subjected to a dehydration decomposition reaction, and meanwhile, the boron source permeates into the ternary precursor along the hole structures, so that boron elements are distributed among primary single-crystal particles in the obtained polycrystalline ternary anode material precursor; in addition, the boron source and the precursor are mixed for primary sintering, so that precursor particles are effectively prevented from growing in the subsequent secondary sintering process, and the particle size of primary particles in secondary particles in the ternary cathode material is uniform.
In the secondary sintering process, the boron element and the nickel element in the precursor of the polycrystalline ternary cathode material generate B-O-Ni chemical bonds which are distributed in grain boundaries among primary single-crystal grains of the polycrystalline ternary cathode material, the B-O-Ni chemical bonds have strong acting force, the acting force among the primary single-crystal grains is improved, the phenomenon that the primary single-crystal grains are damaged due to mutual contact and contact caused by anisotropic volume change among the primary single-crystal grains is inhibited, the structural stability of the polycrystalline ternary cathode material in the subsequent charging and discharging processes is maintained, the cracking phenomenon of the polycrystalline ternary cathode material, particularly the polycrystalline high-nickel ternary cathode material, in the using process is effectively inhibited, and the cycle performance of the polycrystalline ternary cathode material is improved. The preparation method is simple to operate, low in cost and suitable for industrial production.
Preferably, the boron source of step (1) comprises H3BO3、C5H6B(OH)2、C3H9B3O6、(C3H7O)3B、(C6H5O)3B or B2O3Any one or a combination of at least two of the following, typical but not limiting combinations are: h3BO3And B2O3，C5H6B(OH)2And C3H9B3O6，(C3H7O)3B and (C)6H5O)3B, etc., preferably H3BO3And/or B2O3More preferably H3BO3. Said H3BO3The particles are smaller, and the uniform dispersion is facilitated.
Preferably, the ternary precursor of step (1) comprises nickel cobalt manganese hydroxide and/or nickel cobalt aluminium hydroxide. The "and/or" means: the ternary precursor can be nickel-cobalt-manganese hydroxide, nickel-cobalt-aluminum hydroxide, or a mixture of nickel-cobalt-manganese hydroxide and nickel-cobalt-aluminum hydroxide.
Preferably, the molar content of nickel in the ternary precursor in step (1) is 70% or more, for example, 70%, 72%, 75%, 80%, 85%, 90%, or 95%, but not limited to the recited values, and other values not recited in the above-mentioned range of values are also applicable. The ternary precursor has high nickel molar content and can be used for synthesizing a polycrystalline high-nickel ternary cathode material.
Preferably, the mass ratio of the boron source to the ternary precursor in step (1) is (0.02-0.5): 100, and may be, for example, 0.02:100, 0.03:100, 0.05:100, 0.08:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.4:100, 0.45:100, or 0.5:100, but is not limited to the recited values, and other values not recited within the range of values may be equally applicable. If the mass ratio is too large, the gram volume of the material will decrease; if the mass ratio is too small, sufficient B is not present between the grain boundaries of the primary particles to stabilize the structure of the material, and preferably (0.05 to 0.25):100, and the preferred mass ratio can satisfy both the gram volume and the structural stability of the material.
In a preferred embodiment of the present invention, the temperature increase rate of the primary sintering in step (1) is 1 to 10 ℃/min, for example, 1 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min, or 10 ℃/min, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 2 to 7 ℃/min.
Preferably, the temperature of the primary sintering in step (1) is 150 to 500 ℃, and may be, for example, 150 ℃, 180 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃ or 500 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable. If the temperature is lower than 250 ℃, the precursor cannot be decomposed and dehydrated; when the temperature is higher than 500 ℃, the material is subjected to structural change, the reaction activity is reduced, the material performance is influenced, the preferable temperature range is 250-450 ℃, and the material with excellent performance can be obtained.
Preferably, the time for the primary sintering in step (1) is 2 to 30 hours, such as 2 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 20 hours, 25 hours or 30 hours, but not limited to the recited values, and other values not recited in the range of the values are also applicable. If the time is shorter than 2h, the boron element cannot uniformly permeate into the primary particles; the time is longer than 30h, the energy consumption is wasted, the cost is increased, the preferable time is 3-15 h, and the preferable once sintering time can enable the boron element to be distributed more uniformly among once particles.
Preferably, the lithium source in step (2) comprises any one of lithium nitrate, lithium oxalate or lithium hydroxide or a combination of at least two of them, wherein a typical but non-limiting combination is: lithium hydroxide and lithium oxalate, lithium nitrate and lithium oxalate, etc., preferably lithium hydroxide.
Preferably, the molar ratio of the lithium element in the lithium source in the step (2) to the total metal elements in the ternary precursor is (1-1.1): 100, for example, 1:100, 1.01:100, 1.03:100, 1.05:100, 1.08:100, or 1.1:100, but not limited to the recited values, and other non-recited values in the range of the recited values are also applicable, and if the molar ratio is less than 1:100, a non-stoichiometric material is easily produced, and the material properties are poor; if the molar ratio is more than 1.1:100, the sintering residual alkali is too much, and the processing performance and the gas production performance of the material are influenced, and the ratio is preferably (1.02-1.05): 100.
In the invention, the "total metal elements in the ternary precursor" refers to: the sum of metal elements in the ternary precursor. For example, the ternary precursor is nickel-cobalt-manganese-aluminum hydroxide, and the total metal element refers to the sum of nickel, cobalt, manganese and aluminum.
As a preferable technical solution of the present invention, an M source is further added to the mixture of the polycrystalline ternary positive electrode material precursor in step (2) and the lithium source, and the M source includes: any one or a combination of at least two of a zirconium source, a titanium source, an aluminum source, or a magnesium source, among which typical but non-limiting combinations are: zirconium and magnesium sources, titanium and aluminum sources, and the like, preferably a zirconium source.
According to the preparation method provided by the invention, at least one of a zirconium source, a titanium source, an aluminum source or a magnesium source is introduced, and a metal element enters the crystal lattice of the polycrystalline ternary cathode material, so that the crystal lattice stability of the material can be further improved, and the phase change of the material in the charge and discharge processes can be inhibited.
Preferably, the zirconium source comprises any one of, or a combination of at least two of, zirconium oxide, zirconium nitrate, zirconium sulfate, zirconium chloride, or zirconium carbonate, typically but not limited to, in combination: zirconia and zirconium chloride, zirconium nitrate and sulfate, zirconia and zirconium carbonate, and the like.
Preferably, the titanium source comprises any one of titanium dioxide, titanium nitrate or titanium sulphate, or a combination of at least two thereof, typically but not limited to: titanium dioxide and titanium nitrate, titanium dioxide and titanium sulfate, and the like.
Preferably, the aluminium source comprises any one of, or a combination of at least two of, aluminium oxide, aluminium nitrate, aluminium sulphate, aluminium chloride or aluminium carbonate, wherein typical but non-limiting combinations are: alumina and aluminum carbonate, alumina and aluminum nitrate, aluminum sulfate and aluminum chloride, and the like.
Preferably, the magnesium source comprises any one of magnesium oxide, magnesium nitrate, magnesium sulphate, magnesium chloride or magnesium carbonate, or a combination of at least two thereof, typically but not limited to a combination of: magnesium oxide and carbonic acid, magnesium oxide and magnesium chloride, magnesium nitrate and magnesium sulfate, and the like.
In a preferred embodiment of the present invention, the mass ratio of the M source to the polycrystalline ternary positive electrode material is (0.02 to 0.5):100, and may be, for example, 0.02:100, 0.03:100, 0.05:100, 0.08:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, 0.4:100, 0.45:100, or 0.5:100, but not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable. If the mass is less than 0.02:100, the effect of improving the material performance cannot be achieved; when the mass ratio is more than 0.5:100, the gram volume of the material is reduced, preferably (0.05-0.3): 100, and the preferable mass ratio can improve the structural stability of the material and simultaneously does not reduce the gram volume.
Preferably, the temperature increase rate of the secondary sintering in the step (2) is 1 to 10 ℃/min, for example, 1 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min, or 10 ℃/min, but not limited to the above-mentioned values, and other values within the above-mentioned range are also applicable, and preferably 2 to 7 ℃/min.
Preferably, the temperature of the secondary sintering in step (2) is 700 to 900 ℃, for example 700 ℃, 750 ℃, 800 ℃, 850 ℃ or 900 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable. If the temperature is lower than 700 ℃, the sintering reaction of the material is incomplete, and the performance of the material is influenced; when the temperature is higher than 900 ℃, serious lithium-nickel mixed discharging and side reactions can occur to the material, the performance of the material is seriously influenced, and the preferable temperature is 720-770 ℃.
Preferably, the time of the secondary sintering in the step (2) is 4 to 48 hours, for example, 4 hours, 6 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, etc., but not limited to the recited values, and other values not recited in the range of the values are also applicable, if the time is shorter than 4 hours, the material is completely sintered, the material performance is affected, and if the time is longer than 48 hours, the material is excessively sintered, the performance is reduced, and the production efficiency is affected, preferably 10 to 30 hours, and the preferable time can take both the material performance and the production efficiency into consideration.
Preferably, the secondary sintering of step (2) is performed in an air and/or oxygen atmosphere.
As a preferred technical solution of the present invention, the method further comprises: and (3) after the step (2), crushing, removing residual lithium and coating the polycrystalline ternary cathode material, so as to form a coating layer on the surface of the polycrystalline ternary cathode material.
According to the preferable technical scheme provided by the invention, the polycrystalline ternary cathode material is crushed through crushing to obtain particles with uniform particle size, and the requirements of actual production are met. The performance of the polycrystalline ternary cathode material is improved by coating, and irreversible phase change and dissolution of transition metal ions in the charge and discharge processes are inhibited. In addition, the direct contact between the polycrystalline ternary cathode material and electrolyte can be reduced, the occurrence of side reactions is reduced, and the cycle performance of the composite cathode material is further improved.
In the present invention, the crushing method of the polycrystalline ternary positive electrode material is not particularly limited, and mechanical crushing such as a double roll crusher may be used, or manual crushing may be used, and any method commonly used by those skilled in the art may be applied to the present invention.
In the present invention, the method for removing residual lithium is not particularly limited, and any method commonly used by those skilled in the art can be applied to the present invention.
Preferably, the method of removing residual lithium comprises water washing.
Preferably, the water-material ratio of the water washing is (1-3): 1, that is, the mass ratio of water to the polycrystalline ternary cathode material in the water washing process is (1-3): 1, and for example, the mass ratio may be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, but the water washing is not limited to the recited values, and other values in the numerical range are also applicable.
Preferably, the time of the water washing is 5 to 60min, for example, 5min, 10min, 15min, 20min, 30min, 40min, 50min, 55min or 60min, but not limited to the above-mentioned values, and other values not shown in the above-mentioned value range are also applicable, preferably 7 to 30 min.
In the present invention, the coating method of the polycrystalline ternary positive electrode material is not particularly limited, and may be an organic coating or an inorganic coating, and any method commonly used by those skilled in the art is applicable to the present invention.
Preferably, the temperature of the coating is 100 to 700 ℃, for example, 100 ℃, 150 ℃, 200 ℃, 300 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, or 700 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 200 to 500 ℃.
Preferably, the coating time is 3 to 24 hours, for example, 3 hours, 5 hours, 10 hours, 15 hours, 20 hours, 24 hours, etc., but the coating time is not limited to the recited values, and other values not recited in the range of the values are also applicable, and 3 to 15 hours are preferable.
As a further preferred embodiment of the present invention, the method comprises the steps of:
(1) mixing a boron source and a ternary precursor according to a mass ratio of (0.05-0.25): 100, heating to 250-450 ℃ at a speed of 2-7 ℃/min, and sintering for 3-15 h to obtain a polycrystalline ternary cathode material precursor;
the boron source comprises H3BO3、C5H6B(OH)2、C3H9B3O6、(C3H7O)3B、(C6H5O)3B or B2O3Any one or a combination of at least two of;
the ternary precursor comprises nickel cobalt manganese hydroxide and/or nickel cobalt aluminum hydroxide;
(2) mixing the polycrystalline ternary cathode material precursor obtained in the step (1) with a lithium source and an M source, heating to 720-770 ℃ at the speed of 2-7 ℃/min, and sintering for 10-30 h to obtain the polycrystalline ternary cathode material;
controlling the molar ratio of lithium elements in the lithium source to total metal elements in the ternary precursor to be (1.02-1.05): 100, and controlling the mass ratio of M elements in the M source to the polycrystalline ternary cathode material to be (0.05-0.3): 100;
the lithium source comprises any one or a combination of at least two of lithium nitrate, lithium oxalate or lithium hydroxide;
the M source comprises any one or a combination of at least two of a zirconium source, a titanium source, an aluminum source or a magnesium source;
(3) and (3) crushing the polycrystalline ternary cathode material obtained in the step (2), washing for 7-30 min at a water-material ratio of (1-3): 1, and then keeping for 3-15 h at 200-500 ℃ for coating.
In a third aspect, the present invention provides a positive electrode sheet comprising a polycrystalline ternary positive electrode material as described in the first aspect above.
In a fourth aspect, the present invention also provides a lithium ion battery, which includes the positive electrode sheet according to the fifth aspect.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) according to the polycrystalline ternary cathode material provided by the invention, boron elements are distributed in the crystal boundary between single crystal primary particles, and a high-strength B-O-Ni chemical bond is formed between the boron elements and the nickel elements, so that the acting force between the single crystal primary particles is stronger, the single crystal primary particles cannot be damaged due to mutual contact caused by anisotropic volume change between the single crystal primary particles, the structural stability is good, the cycle performance is excellent, and the capacity retention rate of a battery assembled by the cathode material is more than 76% after 1000 cycles; furthermore, the single crystal primary particles also contain an M element, and the M element enters the crystal lattice, so that the crystal lattice stability of the material can be improved, the phase change of the material in the charge and discharge process is inhibited, and the cycle performance of the polycrystalline ternary cathode material is further improved;
(2) according to the polycrystalline ternary cathode material provided by the invention, the coating layer is prepared on the surface of the polycrystalline ternary cathode material, and the coating layer can inhibit irreversible phase change and dissolution of transition metal ions of the polycrystalline ternary cathode material in the charging and discharging processes; meanwhile, the direct contact between the polycrystalline ternary positive electrode material and the electrolyte can be reduced, the occurrence of side reactions is reduced, and the cycle performance is further improved;
(3) according to the preparation method of the polycrystalline ternary cathode material, provided by the invention, the ternary precursor is subjected to a dehydration decomposition reaction, and meanwhile, a boron source permeates into the interior of the ternary precursor along a pore structure, so that boron elements are distributed among primary single-crystal particles in the polycrystalline ternary cathode material precursor; in the secondary sintering process, the boron element and the nickel element form a strong B-O-Ni chemical bond, so that the acting force between single crystal primary particles of the polycrystalline ternary cathode material is enhanced, the phenomenon that the contact is damaged due to anisotropic volume change between the single crystal primary particles is effectively inhibited, and the cracking phenomenon of the polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, in the using process is further inhibited;
(4) according to the preparation method of the polycrystalline ternary cathode material, at least one of a zirconium source, a titanium source, an aluminum source or a magnesium source is introduced, and a metal element enters the crystal lattice of the polycrystalline ternary cathode material, so that the crystal lattice stability of the material can be further improved, and the phase change of the material in the charge and discharge processes can be inhibited.
Detailed Description
The technical solution of the present invention will be further described with reference to the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
(1) according to the mass ratio of 0.05:100, adding H3BO3And Ni0.83Co0.12Mn0.05(OH)2Mixing, heating to 150 ℃ at the speed of 1 ℃/min in nitrogen, and sintering for 48h to obtain a precursor of the polycrystalline ternary cathode material;
(2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with lithium hydroxide, heating to 700 ℃ at the speed of 1 ℃/min, and sintering for 48 hours to obtain the polycrystalline ternary cathode material;
the ratio of the mole of the lithium element in the lithium hydroxide to the sum of the moles of the nickel element, the cobalt element and the manganese element in the nickel-cobalt-manganese hydroxide is controlled to be 1.01: 100.
The polycrystalline ternary cathode material obtained in this example has a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 50%, and a mass fraction of boron element of 0.02%.
Example 2
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
(1) according to the mass ratio of 0.3:100, adding B2O3And Ni0.83Co0.12Mn0.05(OH)2Mixing, heating to 380 ℃ at the speed of 5 ℃/min in argon, and sintering for 30h to obtain a precursor of the polycrystalline ternary cathode material;
(2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with lithium hydroxide and aluminum oxide, heating to 800 ℃ at the speed of 5 ℃/min, and sintering for 26h to obtain the polycrystalline ternary cathode material;
the ratio of the mole of the lithium element in the lithium hydroxide to the mole sum of the nickel element, the cobalt element and the manganese element in the nickel-cobalt-manganese hydroxide is controlled to be 1.04:100, and the mass ratio of the aluminum element to the polycrystalline ternary cathode material is controlled to be 0.25: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 700nm, a mass fraction of nickel element of 50%, a mass fraction of boron element of 0.25%, and a mass fraction of aluminum element of 0.15%.
Example 3
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
(1) according to the mass ratio of 0.5:100, (C) is added3H7O)3B and Ni0.83Co0.12Mn0.05(OH)2Mixing, heating to 500 ℃ at the speed of 10 ℃/min in argon, and sintering for 12h to obtain a precursor of the polycrystalline ternary cathode material;
(2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with lithium nitrate and titanium dioxide, heating to 900 ℃ at the speed of 10 ℃/min, and sintering for 4h to obtain the polycrystalline ternary cathode material;
the ratio of the mole of the lithium element in the lithium nitrate to the sum of the mole of the nickel element, the cobalt element and the aluminum element in the nickel-cobalt-manganese hydroxide is controlled to be 1.08:100, and the mass ratio of the titanium element to the polycrystalline ternary cathode material is controlled to be 0.5: 100.
The polycrystalline ternary cathode material obtained in this example had a primary single crystal particle size of 750nm, a nickel element mass fraction of 50%, a boron element mass fraction of 0.5%, and a titanium element mass fraction of 0.15%.
Example 4
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
(1) according to the mass ratio of 0.05:100, (C) is added6H5O)3B and Ni0.83Co0.12Mn0.05(OH)2Mixing, heating to 250 ℃ at the speed of 2 ℃/min in helium, and sintering for 15h to obtain a precursor of the polycrystalline ternary cathode material;
(2) mixing the polycrystalline ternary cathode material precursor obtained in the step (1) with lithium oxalate and magnesium oxide, heating to 720 ℃ at the speed of 2 ℃/min, and sintering for 30h to obtain the polycrystalline ternary cathode material;
the ratio of the mole of the lithium element in the lithium oxalate to the sum of the mole of the nickel element, the cobalt element and the aluminum element in the nickel-cobalt-manganese hydroxide is controlled to be 1.02:100, and the mass ratio of the magnesium element to the polycrystalline ternary cathode material is controlled to be 0.05: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of 550nm for the primary single crystal particles, a mass fraction of nickel element of 50%, a mass fraction of boron element of 0.05%, and a mass fraction of magnesium element of 0.15%.
Example 5
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
(1) according to the mass ratio of 0.25:100, adding C5H6B(OH)2And C3H9B3O6Mixed boron source of (2) with Ni0.83Co0.12Mn0.05(OH)2Mixing, heating to 450 ℃ at the speed of 7 ℃/min in the air, and sintering for 3h to obtain a precursor of the polycrystalline ternary cathode material;
(2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with lithium hydroxide and zirconium oxide, heating to 770 ℃ at the speed of 7 ℃/min, and sintering for 10h to obtain the polycrystalline ternary cathode material;
the ratio of the mol of the lithium element in the lithium hydroxide to the mol sum of the nickel element, the cobalt element and the manganese element in the nickel-cobalt-manganese hydroxide is controlled to be 1.05:100, and the mass ratio of the sum of the zirconium element to the polycrystalline ternary cathode material is controlled to be 0.3: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of 560nm of single crystal primary particles, a mass fraction of nickel element of 57.2%, a mass fraction of boron element of 0.25%, and a mass fraction of zirconium element of 0.3%.
Example 6
Compared with example 1, the only difference is that H in step (1)3BO3And Ni0.83Co0.12Mn0.05(OH)2The mass ratio of (a) to (b) is replaced with 0.05: 100.
The polycrystalline ternary cathode material obtained in this example has a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 50%, and a mass fraction of boron element of 0.05%.
Example 7
Compared with example 1, the only difference is that H in step (1)3BO3And Ni0.83Co0.12Mn0.05(OH)2The mass ratio of (a) to (b) is replaced with 0.25: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 50%, and a mass fraction of boron element of 0.25%.
Example 8
In comparison with the example 1, the method of the present invention,except that the boron source in step (1) was replaced with B2O3。
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 9
Compared with example 1, the only difference is that the boron source in step (1) is replaced by C5H6B(OH)2。
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 10
The only difference compared to example 1 is that the boron source in step (1) is replaced by (C)3H7O)3B。
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 11
Compared with example 1, the difference is only that Ni is added in step (1)0.83Co0.12Mn0.05(OH)2Replacement by Ni0.75Co0.15Mn0.1(OH)2。
The polycrystalline ternary cathode material obtained in this example has a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 45.2%, and a mass fraction of boron element of 0.02%.
Example 12
Compared with example 1, the difference is only that Ni is added in step (1)0.83Co0.12Mn0.05(OH)2Replacement by Ni0.92Co0.04Mn0.04(OH)2。
The polycrystalline ternary cathode material obtained in this example has a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 55.4%, and a mass fraction of boron element of 0.02%.
Example 13
Compared with example 1, the difference is only that Ni is added in step (1)0.83Co0.12Mn0.05(OH)2Replacement by Ni0.92Co0.04Al0.04(OH)2。
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 56.0%, and a mass fraction of boron element of 0.1%.
Example 14
The only difference compared to example 1 is that the sintering temperature in step (1) was replaced by 250 ℃.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 15
The only difference compared to example 1 is that the sintering temperature in step (1) was replaced with 450 ℃.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 16
Compared with the embodiment 1, the mass ratio of the zirconium element to the polycrystalline ternary cathode material in the step (2) is replaced by 0.05: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 17
Compared with the embodiment 1, the mass ratio of the zirconium element to the polycrystalline ternary cathode material in the step (2) is replaced by 0.3: 100.
The polycrystalline ternary cathode material obtained in this example had a grain size of single crystal primary particles of 600nm, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 18
Compared to example 1, the sintering temperature in step (2) was replaced with 900 ℃.
The polycrystalline ternary cathode material obtained in this example had a grain size of 900nm for the primary single crystal particles, a mass fraction of nickel element of 42.4%, and a mass fraction of boron element of 0.1%.
Example 19
Compared with example 1, the sintering temperature in step (2) was replaced with 770 ℃.
The polycrystalline ternary cathode material obtained in this example had a single crystal primary particle size of 800nm, a nickel element mass fraction of 42.4%, and a boron element mass fraction of 0.1%.
Example 20
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
the polycrystalline ternary positive electrode material prepared in example 1 was crushed using a double roll crusher, washed with water at a water-to-material ratio of 1:1, and then Al was controlled at 250 deg.C2O3The mass ratio of the polycrystalline ternary positive electrode material to the polycrystalline ternary positive electrode material is 0.05%, and the time is kept for 24 hours;
the thickness of the coating layer of the polycrystalline ternary cathode material obtained in the embodiment is 20nm, and the content of the coating is 0.05%.
Example 21
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
crushing the polycrystalline ternary cathode material prepared in the example 2 by using a mechanical crusher, washing with water at a water-material ratio of 1:2, controlling the mass ratio of the zirconium oxide to the polycrystalline ternary cathode material to be 0.15% at 500 ℃, and keeping for 13 hours;
the thickness of the coating layer of the polycrystalline ternary cathode material obtained in the embodiment is 60nm, and the content of the coating is 0.15%.
Example 22
The embodiment provides a preparation method of a polycrystalline ternary cathode material, which comprises the following steps:
the polycrystalline ternary positive electrode material prepared in example 3 was crushed using a double roll crusher and washed with waterThe water-material ratio is 1:3, and then Al is controlled at 700 DEG C2O3The mass ratio of the polycrystalline ternary positive electrode material to the polycrystalline ternary positive electrode material is 0.3 percent, and the time is kept for 3 hours;
the polycrystalline ternary cathode material obtained in the embodiment has a coating layer thickness of 100nm and a coating content of 0.3%.
Example 23
Compared with example 20, the difference is only that Al is added2O3The mass ratio to the polycrystalline ternary positive electrode material was replaced with 0.05%.
The thickness of the coating layer of the polycrystalline ternary cathode material obtained in the embodiment is 20nm, and the content of the coating is 0.05%.
Example 24
Compared with example 20, the difference is only that Al is added2O3The mass ratio to the polycrystalline ternary positive electrode material was replaced with 0.3%.
The polycrystalline ternary cathode material obtained in the embodiment has a coating layer thickness of 100nm and a coating content of 0.3%.
Example 25
The only difference compared to example 20 is that the coating temperature ratio was replaced with 100 ℃.
The polycrystalline ternary cathode material obtained in the embodiment has a coating layer thickness of 100nm and a coating content of 0.3%.
Example 26
The only difference compared to example 20 is that the coating temperature ratio was replaced with 700 ℃.
The polycrystalline ternary cathode material obtained in the embodiment has a coating layer thickness of 100nm and a coating content of 0.3%.
Comparative example 1
The only difference compared to example 5 is that no boron source was added in step (1).
Comparative example 2
The only difference compared to example 5 is that no zirconia was added in step (2).
Comparative example 3
The only difference compared to example 5 is that step (1) does not add a boron source, while step (2) does not add zirconia.
Comparative example 4
Compared with example 1, the difference is only that the method disclosed in example 1 in CN110729466A is adopted in the comparative example to prepare the boron oxide coated nickel cobalt manganese polycrystalline ternary cathode material.
Evaluation of the properties of the positive electrode materials:
the positive electrode materials provided in examples 1-26 and comparative examples 1-4 were mixed with acetylene black and PVDF at a mass ratio of 8:1:1 to prepare a positive electrode sheet, the positive electrode sheet and a negative electrode sheet were assembled into a battery, and graphite, acetylene black, CMC and SBR were mixed at a mass ratio of 8:1:0.5:0.5 in the negative electrode sheet. And (3) carrying out cycle performance test on the battery, wherein the test method comprises the following steps:
testing of cycle performance: charging to 4.2V at constant current of 0.5C, maintaining at constant voltage of 4.2V until the current is less than or equal to 0.05C, standing for 10min, and discharging to 2.8V at constant current of 0.5C.
The test results are shown in table 1.
TABLE 1
Figure BDA0002530938330000211
Figure BDA0002530938330000221
Figure BDA0002530938330000231
The following points can be seen from table 1:
(1) compared with example 1, the polycrystalline ternary cathode materials prepared in examples 6 and 7 have better cycle performance, because the optimized addition amount of B has the best effect;
(2) compared with example 1, the cycle performance of the polycrystalline ternary cathode materials prepared in examples 8-10 is slightly poor, because H3BO3The effect of (2) is best;
(3) compared with example 1, the cycle performance of the polycrystalline ternary cathode materials prepared in examples 14 and 15 is slightly higher, because the optimized primary sintering temperature can obtain a material with a more stable structure;
(4) compared with the embodiment 1, the cycle performance of the polycrystalline ternary cathode materials prepared in the embodiments 16 and 17 is slightly higher, because the optimized doping amount is adopted, the obtained material has good lattice stability, and the phase change of the polycrystalline ternary cathode material in the charge and discharge process is effectively inhibited;
(5) compared with example 1, the cycle performance of the polycrystalline ternary cathode materials prepared in examples 18 and 19 is consistent, because the optimized sintering temperature interval has the best performance;
(6) compared with the embodiments 1 to 3, the polycrystalline ternary cathode materials prepared in the embodiments 20 to 22 have better cycle performance effect, because the coating layer is prepared on the surface of the polycrystalline ternary cathode material, the polycrystalline ternary cathode material can be effectively inhibited from irreversible phase change and dissolving of transition metal ions in the charging and discharging processes; meanwhile, the direct contact between the polycrystalline ternary positive electrode material and electrolyte can be reduced, the occurrence of side reactions is reduced, and the cycle performance of the composite material is further improved;
(7) compared with example 20, the cycle performance of the polycrystalline ternary cathode material prepared in example 23 is lower, because the coating amount is small, the material cannot be effectively prevented from contacting with the electrolyte, and the side reaction cannot be effectively reduced;
(8) compared with example 20, the cycle performance of the polycrystalline ternary cathode materials prepared in examples 25 and 26 is basically equivalent, because the coating temperatures of the three are in a preferred range;
(9) compared with the embodiment 5, the polycrystalline ternary cathode material prepared in the comparative example 1 has poor cycle performance, because the interaction force among primary particles of the material cannot be effectively enhanced without adding the element B, and the material is easy to crack and break in the cycle process, so that the cycle capacity attenuation is accelerated;
(10) compared with example 5, the polycrystalline ternary cathode material prepared in comparative example 2 has poor cycle performance, because the zirconium element has the functions of stabilizing the material structure and inhibiting the phase change of the material in the ternary material;
(11) compared with example 5, the polycrystalline ternary cathode material prepared in comparative example 3 has poor ring performance because the material structure is unstable and primary particles are easily separated from each other;
(12) the polycrystalline ternary positive electrode material prepared in comparative example 4 was slightly inferior to that of example 1, because there was no B element between primary particles of the polycrystalline ternary positive electrode material prepared in comparative example, so that the interaction between primary particles was small, and the cracking phenomenon of the material during the cycle could not be suppressed.
In conclusion, according to the polycrystalline ternary cathode material provided by the invention, boron elements are distributed in the crystal boundary between primary single-crystal particles, the boron elements and nickel elements generate B-O-Ni chemical bonds, the B-O-Ni chemical bonds have strong acting force and good structural stability, and the polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, does not generate a cracking phenomenon in the use process and has excellent cycle performance; furthermore, the single crystal primary particles contain M element, so that the lattice stability of the polycrystalline ternary cathode material is improved, and the phase change of the polycrystalline ternary cathode material in the charge and discharge process is inhibited.
According to the preparation method of the polycrystalline ternary cathode material, in the primary sintering process, a boron source permeates into the interior of the ternary precursor along the pore structure of the ternary precursor, so that boron elements are distributed among primary single-crystal particles in the obtained polycrystalline ternary cathode material precursor. In the secondary sintering process, the boron element and the nickel element in the precursor of the polycrystalline ternary cathode material generate high-strength B-O-Ni chemical bonds, and the high-strength B-O-Ni chemical bonds are distributed in grain boundaries among primary monocrystalline particles of the polycrystalline ternary cathode material, so that the acting force among the primary monocrystalline particles is improved, and the cracking phenomenon of the polycrystalline ternary cathode material, especially the polycrystalline high-nickel ternary cathode material, in the using process is effectively inhibited; the preparation method is simple to operate, low in cost and suitable for industrial production.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. The polycrystalline ternary cathode material is characterized by comprising secondary particles formed by stacking single crystal primary particles, wherein the single crystal primary particles are mutually contacted to form a crystal boundary, and boron elements are distributed on the crystal boundary.
2. The polycrystalline ternary positive electrode material according to claim 1, wherein the single crystal primary particles have a particle size of 300 to 1000nm, preferably 400 to 800 nm;
preferably, the mass percentage of the boron element is 0.02-0.5%, preferably 0.05-0.25%, based on 100% of the polycrystalline ternary cathode material;
preferably, the crystal lattice of the single crystal primary particles comprises an M element, wherein the M element comprises any one or a combination of at least two of a titanium element, a zirconium element, an aluminum element or a magnesium element, and is preferably a zirconium element;
preferably, the mass percentage of the M element is 0.02-0.5%, preferably 0.05-0.3%, based on 100% of the mass of the polycrystalline ternary cathode material;
preferably, the polycrystalline ternary cathode material comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate, preferably lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate with the nickel molar content of more than 70%;
preferably, the mass percentage of the nickel element is 40-60%, preferably 47-58%, based on 100% of the mass of the polycrystalline ternary cathode material;
preferably, the mass ratio of the nickel element to the boron element in the polycrystalline ternary cathode material is (82-2950): 1, preferably (188-1160): 1;
preferably, the mass ratio of the nickel element to the M element in the polycrystalline ternary cathode material is (84-2950): 1, and preferably (156-1160): 1.
3. The polycrystalline ternary positive electrode material according to claim 1 or 2, further comprising a coating layer on the surface of the polycrystalline ternary positive electrode material, wherein the coating layer preferably comprises any one or a combination of at least two of titania, zirconia, alumina or magnesia, preferably alumina and/or zirconia;
preferably, the thickness of the coating layer is 10-200 nm, preferably 30-100 nm.
4. A method for preparing a polycrystalline ternary positive electrode material according to any of claims 1 to 3, characterized in that the method comprises the following steps:
(1) mixing a boron source and a ternary precursor, and sintering for the first time to obtain a polycrystalline ternary cathode material precursor;
(2) and (2) mixing the precursor of the polycrystalline ternary cathode material obtained in the step (1) with a lithium source, and performing secondary sintering to obtain the polycrystalline ternary cathode material.
5. The method of claim 4, wherein the boron source of step (1) comprises H3BO3、C5H6B(OH)2、C3H9B3O6、(C3H7O)3B、(C6H5O)3B or B2O3Any one or a combination of at least two of them, preferably H3BO3And/or B2O3More preferably H3BO3；
Preferably, the ternary precursor in step (1) comprises nickel cobalt manganese hydroxide or nickel cobalt aluminum hydroxide;
preferably, the molar content of nickel in the ternary precursor in the step (1) is more than 70%;
preferably, the mass ratio of the boron source to the ternary precursor in the step (1) is (0.02-0.5): 100, preferably (0.05-0.25): 100.
Preferably, the temperature rise rate of the primary sintering in the step (1) is 1-10 ℃/min, and preferably 2-7 ℃/min;
preferably, the temperature of the primary sintering in the step (1) is 150-500 ℃, and preferably 250-450 ℃;
preferably, the time of the primary sintering in the step (1) is 2-30 h, and preferably 3-15 h.
6. The method of claim 4 or 5, wherein the lithium source of step (2) comprises any one or a combination of at least two of lithium nitrate, lithium oxalate or lithium hydroxide, preferably lithium hydroxide;
preferably, the molar ratio of the lithium element in the lithium source in the step (2) to the total metal elements in the ternary precursor is (1-1.1): 100, preferably (1.02-1.05): 100;
preferably, an M source is further added to the mixing of the polycrystalline ternary cathode material precursor and the lithium source in the step (2), wherein the M source comprises any one or a combination of at least two of a zirconium source, a titanium source, an aluminum source or a magnesium source, and is preferably a zirconium source;
preferably, the zirconium source comprises any one of, or a combination of at least two of, zirconium oxide, zirconium nitrate, zirconium sulfate, zirconium chloride, or zirconium carbonate;
preferably, the titanium source comprises any one of titanium dioxide, titanium nitrate or titanium sulfate or a combination of at least two thereof;
preferably, the aluminium source comprises any one of, or a combination of at least two of, aluminium oxide, aluminium nitrate, aluminium sulphate, aluminium chloride or aluminium carbonate;
preferably, the magnesium source comprises any one of magnesium oxide, magnesium nitrate, magnesium sulfate, magnesium chloride or magnesium carbonate or a combination of at least two of the same;
preferably, the mass ratio of the M source to the polycrystalline ternary cathode material is (0.02-0.5): 100, preferably (0.05-0.3): 100;
preferably, the temperature rise rate of the secondary sintering in the step (2) is 1-10 ℃/min, preferably 2-7 ℃/min;
preferably, the temperature of the secondary sintering in the step (2) is 700-900 ℃, and preferably 720-770 ℃;
preferably, the time for the secondary sintering in the step (2) is 4-48 h, preferably 10-30 h;
preferably, the secondary sintering of step (2) is performed in an air and/or oxygen atmosphere.
7. The method according to any one of claims 4 to 6, further comprising: after the step (2), crushing, removing residual lithium and coating the polycrystalline ternary cathode material, thereby forming a coating layer on the surface of the polycrystalline ternary cathode material;
preferably, the method of removing residual lithium comprises water washing;
preferably, the water-material ratio of the water washing is (1-3): 1;
preferably, the time for washing is 5-60 min, preferably 7-30 min;
preferably, the coating temperature is 100-700 ℃, and preferably 200-500 ℃;
preferably, the coating time is 3-24 hours, and preferably 3-15 hours.
8. A method according to any of claims 4 to 7, characterized in that the method comprises the steps of:
(1) mixing a boron source and a ternary precursor according to a mass ratio of (0.05-0.25): 100, heating to 250-450 ℃ at a speed of 2-7 ℃/min, and sintering for 3-15 h to obtain a polycrystalline ternary cathode material precursor;
the boron source comprises H3BO3、C5H6B(OH)2、C3H9B3O6、(C3H7O)3B、(C6H5O)3B or B2O3Any one or a combination of at least two of;
the ternary precursor comprises nickel cobalt manganese hydroxide and/or nickel cobalt aluminum hydroxide;
(2) mixing the polycrystalline ternary cathode material precursor obtained in the step (1) with a lithium source and an M source, heating to 720-770 ℃ at the speed of 2-7 ℃/min, and sintering for 10-30 h to obtain the polycrystalline ternary cathode material;
controlling the molar ratio of lithium elements in the lithium source to total metal elements in the ternary precursor to be (1.02-1.05): 100, and controlling the mass ratio of M elements in the M source to the polycrystalline ternary cathode material to be (0.05-0.3): 100;
the lithium source comprises any one or a combination of at least two of lithium nitrate, lithium oxalate or lithium hydroxide;
the M source comprises any one or a combination of at least two of a zirconium source, a titanium source, an aluminum source or a magnesium source;
(3) and (3) crushing the polycrystalline ternary cathode material obtained in the step (2), washing for 7-30 min at a water-material ratio of (1-3): 1, and then keeping for 3-15 h at 300-500 ℃ for coating.
9. A positive electrode sheet, characterized by comprising the polycrystalline ternary positive electrode material according to any one of claims 1 to 3.
10. A lithium ion battery, characterized in that it comprises the positive electrode sheet according to claim 9.
CN202010518269.4A 2020-06-09 2020-06-09 Polycrystalline ternary positive electrode material and preparation method and application thereof Pending CN111668476A (en)

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