CN107528059B - Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof - Google Patents

Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof Download PDF

Info

Publication number
CN107528059B
CN107528059B CN201710778059.7A CN201710778059A CN107528059B CN 107528059 B CN107528059 B CN 107528059B CN 201710778059 A CN201710778059 A CN 201710778059A CN 107528059 B CN107528059 B CN 107528059B
Authority
CN
China
Prior art keywords
active material
positive electrode
lithium
electrode active
material according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201710778059.7A
Other languages
Chinese (zh)
Other versions
CN107528059A (en
Inventor
武怿达
起文斌
黄学杰
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Institute of Physics of CAS
Original Assignee
Institute of Physics of CAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Institute of Physics of CAS filed Critical Institute of Physics of CAS
Priority to CN201710778059.7A priority Critical patent/CN107528059B/en
Publication of CN107528059A publication Critical patent/CN107528059A/en
Application granted granted Critical
Publication of CN107528059B publication Critical patent/CN107528059B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • 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
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 present invention provides a phosphate-coated spinel-structured positive electrode active material, wherein the positive electrode active material comprises a spinel-structured positive electrode having a chemical formula of L iMn2‑xAxOyAnd a phosphate coating layer coated on the surface thereof, formula L iMn2‑xAxOyWherein A is selected from one or more of Ni, Fe, Co, Ti, Y, Sc, Ru, Cu, Mo, Ge, W, Zr, Ca and Sr, x is more than or equal to 0 and less than or equal to 0.7, and Y is more than or equal to 3.8 and less than or equal to 4.2; and wherein the lithium-containing compound particles have a transition layer containing a diffusion element that diffuses into the lithium-containing compound particles by cladding and thereafter optional calcining. The invention also provides a preparation method of the positive active material and application of the positive active material in a lithium ion secondary battery. The positive active material has improved cycling stability and coulombic efficiency when used in a lithium ion secondary battery.

Description

Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof
Technical Field
The invention relates to a phosphate-coated spinel-structured positive electrode active material, and a preparation method and application thereof.
Background
In recent years, electric vehicles have been rapidly developed under the push of governments and automobile manufacturers in view of environmental protection, and lithium ion secondary batteries have become an ideal power source for a new generation of electric vehicles due to their excellent performance2) A layered material represented by lithium iron phosphate (L iFePO)4) Olivine-type material typified by lithium manganate (L iMn)2O4) Among these materials, spinel-structured materials have been widely studied because of their advantages of environmentally friendly raw materials, low cost, simple process, high safety, and good rate capability, and in particular, lithium nickel manganese oxide (L iNi) having a spinel structure0.5Mn1.5O4) The theoretical specific capacity is 146.7mAh/g, the working voltage is 4.7Vvs. L i/L i+The theoretical capacity density can reach 695Wh/kg, and the lithium ion secondary battery material is an ideal material for the lithium ion secondary battery for the electric vehicle in the future.
However, with current spinel structure materials, H can be generated at high pressure due to conventional carbonate based electrolytes2O (even fresh electrolyte inevitably contains trace amount of H2O)，H2O and L iPF in electrolyte6The reaction generates HF, which can further corrode the surface of the anode material to dissolve the surface of the anode material, and finally lead to the reduction of active substances, and meanwhile, for the lithium nickel manganese oxide (L iNi)0.5Mn1.5O4) The Mn ions dissolved in the positive electrode can migrate to the negative electrode and deposit on the negative electrode, so that a solid electrolyte interface film (SEI film) on the surface of the negative electrode is continuously decomposed, active lithium in a battery system is consumed, and capacity is attenuated.
In order to solve the above problems, various coating schemes have been proposed, and among them, lithium phosphate is typically used for coating because lithium phosphate is resistant to high pressure, can absorb hydrofluoric acid, and does not contain transition metal ions, and has no side effect on the battery. Among them, the coating method generally used in the art includes: (1) mixing a positive electrode material to be coated with lithium phosphate in a solid phase and calcining the mixture to coat the positive electrode material; and (2) coating the positive electrode material to be coated with lithium phosphate by using a sol-gel method. However, with these methods, it is difficult to uniformly distribute lithium phosphate on the surface of the positive electrode material due to mismatch between crystal lattices.
Disclosure of Invention
Therefore, the present invention is directed to provide a phosphate-coated spinel cathode active material, a method for preparing the same, and applications thereof, which solve the problems and disadvantages of the prior art.
The above object of the present invention is achieved by the following means.
In one aspect, the present invention provides a phosphate-coated spinel-structured positive electrode active material, wherein the positive electrode active material comprises a spinel-structured positive electrode having a chemical formula of L iMn2-xAxOyAnd a phosphate coating layer coated on the surface thereof, formula L iMn2-xAxOyWherein A is selected from one or more of Ni, Fe, Co, Ti, Y, Sc, Ru, Cu, Mo, Ge, W, Zr, Ca and Sr, x is more than or equal to 0 and less than or equal to 0.7, and Y is more than or equal to 3.8 and less than or equal to 4.2; and wherein the lithium-containing compound particles have a transition layer containing a diffusion element that diffuses into the lithium-containing compound particles by coating, such as hydrothermal coating, and thereafter, optionally calcining.
The inventors of the present invention have unexpectedly found that, when spinel-structured particles (lithium-containing compound particles) are coated with a phosphate by a hydrothermal method, the phosphate or a precursor thereof and a transition metal element (diffusion element) such as Fe, Co or Mn contained in the coating solution are diffused into the interior of the particles at high temperature and high pressure, thereby forming a transition layer in the spinel-structured particles. Such a transition layer facilitates the formation of a robust structure between the coating layer and the active substance within the spinel-structured particle.
Further, the inventors of the present invention have also found that, when the positive electrode activity of the present invention is subjected to calcination (heat treatment) under certain conditions, at least part of the transition metal element in the transition metal element-containing phosphate is able to diffuse into the spinel-structured particles, while at least part of the coating becomes transition metal-free, uniformly dense lithium phosphate.
The positive electrode active material according to the present invention, wherein the chemical formula is L iMn2-xAxOyIn the present invention, the dopant element is used to replace the transition metal element Mn.. in some embodiments, the dopant element A can be represented by the formula ∑ wiAiDenotes wiIs AiAtomic percent in the entire doping element A, ∑ w i1, wherein 1 ≦ i ≦ 16, preferably 1 ≦ i ≦ 5, and more preferably 1 ≦ i ≦ 3.
In some embodiments, formula L iMn2-xAxOyWherein A is selected from Co and Ni.
The positive electrode active material according to the present invention, wherein the chemical formula is L iMn2-xAxOyIn the formula, x is more than or equal to 0 and less than or equal to 0.5. In some embodiments x is 0, and in some embodiments 0.1. ltoreq. x.ltoreq.0.5.
In some preferred embodiments, the chemical formula L iMn may be used2OyIn some embodiments, the lithium-containing compound particles have the formula L iMn2O4。
According to the positive electrode active material provided by the invention, the lithium-containing compound particle has a chemical formula of L iMn2- xAxO40.1. ltoreq. x. ltoreq.0.5. in some embodiments, the lithium-containing compound particles have a chemical formula of L iNi0.5Mn1.5O4。
The positive electrode active material according to the present invention, wherein the lithium-containing compound particles have a particle size ranging from a lower end value of 0.1 μm (200nm), 0.2 μm (200nm), or 0.5 μm (500nm) to an upper end value of 0.5 μm (500nm), 10 μm, 20 μm, or 30 μm. In some embodiments, the lithium-containing compound particles have a particle size of 0.1 to 30 μm. In some preferred embodiments, the lithium-containing compound particles have a particle size of 0.1 to 10 μm, in some preferred embodiments 0.2 to 10 μm, and in some preferred embodiments 0.2 to 0.5 μm.
In some embodiments, the phosphate is selected from L iCoPO4、LiFePO4、LiMnPO4And L i3PO4One or more of (a).
According to the positive electrode active material provided by the invention, the thickness of the phosphate coating layer is 1-50 nm, and preferably 5-15 nm.
According to the positive electrode active material provided by the invention, the coverage degree of the phosphate coating layer on the surface of the lithium-containing compound particles is 1-100%. In some embodiments, the phosphate coating has a coverage on the surface of the lithium-containing compound particles from a low endpoint value of 10%, 20%, 30%, 40%, 50%, or 60% to a high endpoint value of 50%, 60%, 70%, 80%, or 90%. For example, in some preferred embodiments, the phosphate coating layer has a coverage of 20 to 90%, and in some preferred embodiments, 60 to 80% on the surface of the lithium-containing compound particles.
According to the positive electrode active material provided by the present invention, the phosphate coating layer may be composed of a single layer of phosphate particles. In some embodiments, the phosphate particles have a particle size of 1 to 50nm, and in some embodiments 5 to 20 nm.
According to the cathode active material provided by the present invention, the diffusion element may be represented by formula L iMn2-xAxOyWherein the metal elements other than lithium are the same or different. As described above, in some embodiments, the diffusing element is selected from one or more of Fe, Co, and Mn.
In some preferred embodiments, the diffusion element is selected from one or more of Fe, Co and Mn, and the lithium-containing compound particles have a chemical formula of L iMn2Oy. In this case, the lithium-containing compound particles do not contain a doping element.
In other preferred embodiments, the diffusing element is Fe and/or Co, and the diffusing element is related to formula L iMn2-xAxOyDifferent from the metal element (doping element a) other than lithium, and in other preferred embodiments, the diffusion element is selected from one or more of Fe, Co and Mn, and the diffusion element is of the formula L iMn2-xAxOyThe metal elements other than lithium in the composition are the same.
In some embodiments, the phosphate salt is substantially L i3PO4The diffusing element is selected from one or more of Fe, Co and Mn, and in other embodiments the phosphate is substantially L iFePO4Or L iMnPO4And the diffusion element is a corresponding transition metal element Fe or Mn in the phosphate.
According to the positive electrode active material provided by the invention, the thickness of the transition layer is 0-15 μm.
In some embodiments, the transition layer has a thickness of 0.1 to 5 μm, and in some embodiments 100 to 250 nm. In still other embodiments, the transition layer is distributed between 0 and 10nm from the surface of the lithium-containing compound particles, and in some embodiments, the transition layer is distributed between 0 and 5nm from the surface of the lithium-containing compound particles.
According to the positive electrode active material provided by the present invention, the mass ratio of the diffusing element to the phosphate is greater than 0 to 1 or less. In some embodiments, the mass ratio of the diffusing element to the phosphate is 0.5 to 1.
According to the positive electrode active material provided in the present invention, the phosphate coating layer and the transition layer may be measured by any method known in the art. For example, the type of the phosphate coating layer can be determined by X-ray diffraction spectrum and X-ray photoelectron spectrum, and the distribution and content of each element in the transition layer can be measured by X-ray energy spectrum line scanning of a spherical aberration correction transmission electron microscope.
In another aspect, the present invention provides a method for preparing the above-described positive electrode active material, the method comprising:
(1) dripping phosphoric acid or an ammonium salt solution thereof, a precursor salt solution of a diffusion element and a lithium precursor solution into a dispersion system containing lithium compound particles, and stirring and mixing to obtain a mixture;
(2) transferring the mixture obtained in the step (1) into a closed reaction kettle, and carrying out hydrothermal reaction at 120-250 ℃ for 0.1-20 hours;
(3) cooling the material obtained by the hydrothermal reaction in the step (2) to room temperature, and respectively carrying out centrifugal cleaning by using water and ethanol; and
(4) and (4) drying the cleaned material obtained in the step (3) at 80-150 ℃ for 3-6 hours to obtain the positive active material.
According to the preparation method provided by the invention, the ammonium salt of the phosphoric acid in the step (1) can be ammonium dihydrogen phosphate and/or diammonium hydrogen phosphate.
According to the preparation method provided by the invention, the precursor salt of the diffusion element in the step (1) is selected from one or more of ferrous sulfate, cobalt sulfate, manganese sulfate, cobalt nitrate, manganese chloride, cobalt chloride and ferrous chloride.
According to the preparation method provided by the invention, the lithium precursor in the step (1) is lithium hydroxide.
According to the preparation method provided by the invention, the solvent in the step (1) is water and/or ethanol.
According to the preparation method provided by the invention, the solvent of the dispersion system of the lithium-containing compound particles is water and/or ethanol.
According to the preparation method provided by the invention, in the step (1), phosphoric acid or ammonium salt thereof, precursor salt of a diffusion element and a lithium precursor are added according to the following proportion: the molar ratio of phosphorus, diffusion element and lithium is 1: 0.5-2: 0.5 to 6. In some embodiments, the phosphoric acid or ammonium salt thereof, the precursor salt of the diffusing element, and the lithium precursor in step (1) are added in the following proportions: the molar ratio of phosphorus, diffusion element and lithium is 1: 0.5-1: 3 to 6.
According to the preparation method provided by the invention, the concentration of the solution of phosphoric acid or ammonium salt thereof in the step (1) is 0.1 mol/L-0.3 mol/L.
According to the preparation method provided by the invention, the concentration of the precursor salt solution of the diffusion element in the step (1) is 0.1 mol/L-0.3 mol/L.
According to the preparation method provided by the invention, the concentration of the lithium precursor solution in the step (1) is 0.3 mol/L-1.8 mol/L, preferably 0.3 mol/L-0.9 mol/L.
According to the production method provided by the present invention, the mass fraction of the lithium-containing compound particles in the dispersion system of the lithium-containing compound particles in step (1) is 30 to 50 wt%.
According to the preparation method provided by the invention, the dropping sequence of the phosphoric acid or the ammonium salt thereof, the precursor salt of the diffusion element and the lithium precursor in the step (1) can be adjusted at will.
According to the preparation method provided by the invention, the temperature of the hydrothermal reaction in the step (2) is 150-200 ℃, and preferably 180 ℃.
According to the preparation method provided by the invention, the hydrothermal reaction time in the step (2) is 5-15 hours, preferably 10 hours.
The preparation method provided by the invention further comprises the following steps:
(5) and (4) calcining the positive electrode active material obtained in the step (4) at 350-900 ℃ for 0.1-10 hours to obtain the sintered positive electrode active material.
According to the preparation method provided by the invention, the calcining temperature in the step (5) is 450-700 ℃.
According to the preparation method provided by the invention, the calcining time in the step (5) is 1-5 hours, preferably 3 hours.
According to the production method provided by the present invention, the calcination in the step (5) is carried out under oxygen, air, an atmosphere containing a reducing gas such as hydrogen, or an inert atmosphere such as nitrogen or argon.
In still another aspect, the present invention provides a positive active material prepared by the above preparation method.
In still another aspect, the present invention provides use of the positive active material in a lithium ion secondary battery.
Further, the invention provides a lithium ion secondary battery positive electrode, which comprises a current collector and a positive active material loaded on the current collector, wherein the positive active material is the positive active material provided by the invention or the positive active material prepared by the method.
According to the positive electrode of the lithium ion secondary battery provided by the invention, the positive electrode further comprises a conductive additive and a binder.
According to the positive electrode for a lithium ion secondary battery provided by the present invention, wherein the conductive additive may be an electrical additive that is conventional in the art, the present invention is not particularly limited thereto. In some embodiments, the conductive additive is carbon black.
The positive electrode for a lithium ion secondary battery according to the present invention may be one that is conventional in the art, and the present invention is not particularly limited thereto. In some embodiments, the binder is polyvinylidene fluoride (PVDF).
The invention further provides a lithium ion secondary battery which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the positive electrode is the positive electrode provided by the invention.
According to the present invention, there is provided a lithium ion secondary battery, wherein the battery further comprises a case, and wherein a positive electrode, a negative electrode, a separator (collectively referred to as an electrode group), and an electrolyte are sealed in the case.
The lithium metal secondary battery according to the present invention may employ a negative electrode, a separator and an electrolyte, which are conventional in the art, and the present invention is not particularly limited thereto, and in some embodiments, the negative electrode is lithium metal, in some embodiments, the separator is a three-layer film of PP/PE/PP coated with alumina on both sides, and in some embodiments, the electrolyte is L iPF6The non-aqueous electrolyte of Ethylene Carbonate (EC)/dimethyl carbonate (DMC) with a concentration of 1 mol/L, wherein the volume ratio of EC to DMC is 1: 1.
The positive active material provided by the invention obviously reduces the reactivity between the positive material with the spinel structure and the electrolyte through coating, stabilizes the surface structure of the positive active material with the spinel structure, and inhibits the manganese dissolution on the surface of the positive active material with the spinel structure in the circulating process under the conditions of high temperature and high pressure, thereby improving the capacity retention rate and the charging and discharging coulombic efficiency.
The positive electrode active material provided by the invention can be used as a positive electrode active material of a lithium ion secondary battery, and the battery made of the material has excellent cycle performance.
The preparation method of the positive active material provided by the invention obviously improves the cycling stability and the coulombic efficiency of the positive active material. Without wishing to be bound by theory, it is believed that by the method provided by the present invention, a transition layer is formed within the lithium-containing compound particles having a spinel structure below the phosphate coating layer, thereby making the coating more robust, uniform and dense. This coating at least partially inhibits corrosion of the positive electrode active material by the electrolyte, thereby reducing capacity fade of the material. The lithium ion secondary battery including the positive electrode active material of the present invention may be used as an energy source for electric tools, electric bicycles, hybrid electric vehicles, pure electric vehicles, and the like.
Drawings
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
l iMn in FIG. 12O4And an XRD fast-scan pattern of the positive active material prepared in the embodiment 1 at 10-80 degrees;
l iMn in FIG. 22O4And an XRD slow-scanning spectrum of the cathode active material prepared in the embodiment 1 at 20-35 degrees;
FIG. 3 is a graph showing the distribution of Mn, P, Fe and O elements on the surface of the positive electrode active material prepared in example 1 at different depths;
l i in FIG. 43PO4And XPS spectra of phosphorus elements on the surfaces of the positive electrode active materials prepared in examples 1 and 3;
l iMn in FIG. 52O4And XPS spectra of iron elements on the surfaces of the positive electrode active materials prepared in examples 1 and 3;
fig. 6 is an SEM image of the positive electrode active material prepared in example 1;
fig. 7 is an SEM image of the positive electrode active material prepared in example 2;
fig. 8 is an SEM image of the positive electrode active material prepared in example 5;
fig. 9 is an SEM image of the positive electrode active material prepared in example 6;
FIG. 10 shows L iMn2O4And the charge-discharge cycle curve of the lithium ion secondary battery of the positive electrode active material of example 3;
FIG. 11 shows L iMn2O4And the coulombic efficiency curve of the lithium ion secondary battery of the positive electrode active material of example 3;
FIG. 12 shows L iNi0.5Mn1.5O4And the charge-discharge cycle curve of the lithium ion secondary battery of the positive electrode active material of example 6;
FIG. 13 shows L iNi0.5Mn1.5O4And the coulombic efficiency curve of the lithium-ion secondary battery of the positive electrode active material of example 6.
Detailed Description
The present invention is described in further detail below with reference to specific embodiments, which are given for the purpose of illustration only and are not intended to limit the scope of the invention.
X-ray diffraction (XRD)
The material was analyzed using a D8X X-ray diffractometer manufactured by Bruker, Germany, equipped with a L YNXEYE-XE detector, the voltage and operating current of the X-ray tube being 40kV and 40mA, respectively, and the X-rays radiated were Cu KαRadiation (wavelength)
Figure BDA0001396308110000081
Figure BDA0001396308110000082
) Wherein the scanning step length is 0.02 degrees, the fast-scanning spectrogram speed is 0.3 seconds per step, and the slow-scanning spectrogram speed is 3 seconds per step.
Scanning Electron Microscope (SEM)
The microscopic morphology of the samples was studied using a field emission scanning electron microscope model S4800, manufactured by Hitachi (Hitachi corporation) in japan.
Spherical aberration correction electron microscope (STEM)
The atomic scale microscopic morphology and the content distribution of surface elements of the sample were investigated using a 2100F spherical aberration correction-scanning transmission electron microscope manufactured by japan JEO L corporation.
X-ray photoelectron spectroscopy (XPS)
The type and chemical environment of the surface elements of the powder samples were studied using an X-ray photoelectron spectrometer model ESCA L AB 250 manufactured by Thermo Fisher corporation, wherein the source of X-ray radiation was Mg K α.
Inductively coupled plasma-atomic emission spectroscopy (ICP)
The iCAP manufactured by Thermo Fisher corporation is adoptedTM7200 ICP-OES plasma spectrometer to determine the content of different elements in the powder samples.
Example 1
10.52g of L iMn2O4The material (particle size 200nm) was added to 20ml of water with constant stirring, giving L iMn2O4Dispersion 10ml of 0.2 mol/L FeSO4Aqueous solution, 10ml NH with a concentration of 0.2 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.6 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a resultant after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, and drying the powder for 3 hours at 80 ℃ to obtain the cathode active material.
FIG. 1 shows L iMn2O4And an XRD fast-scan pattern of the cathode active material prepared in the embodiment 1 at 10-80 degrees, as can be seen from figure 1, L iMn2O4There was little difference from the XRD patterns of the positive electrode active material of example 1, both having a cubic spinel structure.
FIG. 2 shows L iMn2O4And an XRD slow-scanning spectrum of the cathode active material prepared in the embodiment 1 at 20-35 degrees. As can be seen from FIG. 2, the positive electrode active material prepared in example 1 has a lithium phosphate peak at 20-35 deg.
FIGS. 1 and 2 show L iMn after hydrothermal coating2O4The host crystal structure of the material is unchanged, but lithium phosphate is formed.
Fig. 3 is a line scan of a positive electrode active material prepared in example 1 with respect to the surface spherical aberration correction electron microscope. As can be seen from FIG. 3, for example 1, P is distributed in the 0-5 nm layer on the outermost surface of the material, and the closer to the surface, the higher the content is, iron is distributed in the 5-15 nm layer on the subsurface, and the closer to the surface, the higher the content is.
Fig. 4 shows XPS spectra of lithium phosphate and phosphorus element on the surface of the positive electrode active material obtained in example 1. Referring to fig. 1, 2 and 4, it is shown that lithium phosphate is formed on the surface of the positive electrode active material after coating by the hydrothermal method.
FIG. 5 shows L iMn2O4The XPS spectrum of the surface iron element of the positive active material obtained in example 1 showed that the signal of Fe was observed on the surface after hydrothermal reaction, L iMn2O4The iron element in the iron-based coating comes from FeSO added in the coating process4。
Fig. 6 shows a representative SEM image of the cathode active material prepared in example 1. SEM characterization results show that by adding FeSO4At L iMn2O4The surface of the material was uniformly covered with a layer of particles of about 5nm, with a coverage of about 80%. Meanwhile, the information of the figures 1-6 shows that the particles with the thickness of about 5nm are lithium phosphate.
Thus, the surface of the positive electrode active material prepared in example 1 had a lithium phosphate coating layer, L iMn2O4A transition layer containing iron element (i.e. diffusion element) at 0-10 nm below the surface of the particles, and L iMn2O4The particles still have a cubic spinel structure.
Example 2
10.52g of L iMn2O4The material (particle size 200nm) was added to 20ml of water with constant stirring, giving L iMn2O4Dispersion 10ml of NH each having a concentration of 0.2 mol/L4H2PO4The aqueous solution and 10ml of a L iOH aqueous solution having a concentration of 0.6 mol/L were added to the dispersion, with constant stirring, and the resulting mixture was transferredPlacing into 100ml polytetrafluoroethylene reaction kettle, keeping temperature at 180 deg.C for 10 hr, collecting powder of resultant after reaction, centrifuging and cleaning with water for 3 times, centrifuging and cleaning with anhydrous ethanol for one time, drying at 80 deg.C for 3 hr to obtain lithium phosphate and L iMn2O4A mixture of (a).
Fig. 7 shows a representative SEM image of the cathode material prepared in example 2. As can be seen from FIG. 7, in the absence of FeSO4In the case of (2), L iMn2O4The material surface was smooth, but combined with the XRD fast and slow scan tests, at L iMn2O4Lithium phosphate particles of about 50nm were observed from particle to particle, and the distribution of lithium phosphate was not uniform. By comparison with example 1, it can be seen that FeSO is added to the hydrothermal cladding4L iMn below the lithium phosphate coating layer2O4A transition layer is formed within the particle and facilitates the coating of lithium phosphate at L iMn2O4The surface of the particles is uniformly coated.
Example 3
10.52g of L iMn2O4The material (particle size 200nm) was added to 20ml of water with constant stirring, giving L iMn2O4Dispersion 10ml of 0.2 mol/L FeSO4Aqueous solution, 10ml NH with a concentration of 0.2 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.6 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, drying the powder for 3 hours at 80 ℃, and calcining the dried powder for 3 hours at 450 ℃ in the air to obtain the cathode active material.
The XRD fast-and slow-scan patterns of example 3 show L iMn after hydrothermal cladding and calcination in air2O4The host crystal structure of the particles was not changed, but lithium phosphate was formed.
FIG. 4 also shows the positive electrode activity obtained in example 3XPS spectrum of phosphorus on material surface FIG. 4 illustrates L iMn after hydrothermal coating2O4Lithium phosphate is formed on the surface of the material.
FIG. 5 also shows an XPS spectrum of the surface iron element of the positive active material obtained in example 3. the results show that, after hydrothermal reaction, Fe signal is observed on the surface, L iMn2O4The iron element in the material comes from FeSO added in the coating process4。
Referring to fig. 5, it can be seen by comparing example 1 with example 3 that the surface iron element of the material measured by XPS is weakened by the post-calcination at 450 ℃, but the content of the iron element measured by ICP in example 1 and example 3 is not changed. This indicates that the iron element in the transition layer diffuses into the interior of the particles during calcination, and it can be concluded that the longitudinal distribution of the diffusing element in the transition layer produced during cladding is affected by the post-calcination temperature.
SEM image of the cathode material prepared in example 3 shows L iMn2O4The surface was uniformly covered with a layer of particles around 5nm, coverage was about 80%.
The surface of the positive electrode active material prepared in example 3, which had a lithium phosphate coating layer thereon, was L iMn2O4The particles have a transition layer comprising iron below the surface, and L iMn2O4The particles still have a cubic spinel structure.
Example 4
10.52g of L iMn2O4The material (particle size 200nm) was added to 20ml of water with constant stirring, giving L iMn2O4Dispersing system 10ml of MnSO with the concentration of 0.2 mol/L are respectively added in sequence4Aqueous solution, 10ml NH with a concentration of 0.2 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.6 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a resultant after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, and drying the powder for 3 hours at 80 DEG CAnd obtaining the positive electrode active material.
The XRD fast-scan and slow-scan patterns of example 4 show L iMn after hydrothermal cladding2O4The host crystal structure of the particles did not change, but lithium manganese phosphate was formed on the surface.
The scanning line of the electron microscope for correcting the spherical aberration on the surface of the cathode active material in the embodiment 4 shows that P is distributed in a 0-5 nm layer on the outermost surface of the material, and the content of P is higher when the P is closer to the surface. In the 5-10 nm layer of the subsurface, the content of manganese is obviously higher than that in other areas, and the content is higher closer to the surface.
SEM image of the positive active material prepared in example 4 shows L iMn2O4The surface of the material was uniformly covered with a layer of particles of about 5nm, with a coverage of about 70%.
The surface of the positive electrode active material prepared in example 4 had a coating layer of lithium manganese phosphate at L iMn2O4A transition layer rich in Mn element is arranged at 0-5 nm below the particle surface, and L iMn2O4The particles still have a cubic spinel structure.
Example 5
9.14g of L iNi0.5Mn1.5O4The material (particle size 500nm) was added to 20ml of water with constant stirring, giving L iNi0.5Mn1.5O4Dispersion 10ml of 0.1 mol/L CoSO4Aqueous solution, 10ml NH with a concentration of 0.1 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.3 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, and drying the powder for 3 hours at 80 ℃ to obtain the cathode active material.
Fig. 8 is a representative SEM image of the cathode active material prepared in example 5. As can be seen from SEM characteristics, the surface of the prepared cathode active material is uniformly covered with a layer of particles with the size of about 10nm, and the coverage degree is 70%.
Further, the surface of the positive electrode active material prepared in example 5 was coated with lithium phosphate at L iNi0.5Mn1.5O4A transition layer containing cobalt element at 0-10 nm below the particle surface, and L iNi0.5Mn1.5O4The particles still have a cubic spinel structure.
Example 6
9.14g of L iNi0.5Mn1.5O4The material (particle size 500nm) was added to 20ml of water with constant stirring, giving L iNi0.5Mn1.5O4Dispersion 10ml of 0.1 mol/L CoSO4Aqueous solution, 10ml NH with a concentration of 0.1 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.3 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, drying the powder for 3 hours at 80 ℃, and heating the dried powder for 3 hours at 550 ℃ in air to obtain the cathode active material.
FIG. 9 is a representative SEM image of the cathode material prepared in example 6 from SEM characterization, L iNi0.5Mn1.5O4The surface of the material is uniformly covered with a layer of lithium phosphate particles with the size of about 12nm, and the coverage degree is about 60 percent
Further characterization was performed by the same characterization means as example 1, and the results showed that the positive active material prepared in example 6 had a lithium phosphate coating layer on the surface thereof at L iNi0.5Mn1.5O4A transition layer comprising cobalt below the surface of the particles, and L iNi0.5Mn1.5O4The particles still have a cubic spinel structure. In particular, after the subsequent calcination at 550 ℃, the cobalt element on the surface of the material measured by XPS was reduced, but the content of the cobalt element in examples 5 and 6 was not changed by ICP measurement.This indicates that the cobalt element in the transition layer diffuses into the inside of the particles during calcination, and it can be concluded that the longitudinal distribution of the diffusion element in the transition layer generated during cladding is affected by the post-calcination temperature.
Example 7
9.14g of L iNi0.5Mn1.5O4The material (particle size 500nm) was added to 20ml of water with constant stirring, giving L iNi0.5Mn1.5O4Dispersion 10ml of 0.1 mol/L CoSO4Aqueous solution, 10ml NH with a concentration of 0.1 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.3 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, drying the powder for 3 hours at 80 ℃, and heating the dried powder for 3 hours at 700 ℃ in the air to obtain the cathode active material.
The same characterization as in example 1 was performed, and the results showed that the surface of the positive electrode active material prepared in example 7 was uniformly covered with a layer of lithium phosphate particles having a size of about 15nm at a coverage of 30% at L iNi0.5Mn1.5O4A transition layer comprising cobalt below the surface of the particles, and L iNi0.5Mn1.5O4The particles still have a cubic spinel structure. In particular, after the subsequent calcination at 700 ℃, the cobalt element on the surface of the material measured by XPS was reduced, but the content of the cobalt element in examples 5 and 7 was not changed by ICP measurement. This indicates that the cobalt element in the transition layer diffuses into the interior of the particles during heating, and it can be concluded that the longitudinal distribution of the diffusion element in the transition layer produced during cladding is affected by the post-calcination temperature.
Example 8
16.085g of L iNi0.5Mn1.5O4The material (particle size 500nm) was added to 20ml of water with constant stirring, giving L iNi0.5Mn1.5O4Dispersion 10ml of 0.15 mol/L CoSO4Aqueous solution, 10ml NH with a concentration of 0.3 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 0.9 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, and drying the powder for 3 hours at 80 ℃.
The surface of the positive electrode active material prepared in example 8 was uniformly covered with a layer of lithium phosphate particles having a size of about 5nm at a coverage of 70% at L iNi0.5Mn1.5O4A transition layer containing cobalt element at 0-10 nm below the particle surface, and L iNi0.5Mn1.5O4The particles still have a cubic spinel structure.
Example 9
16.085g of L iNi0.5Mn1.5O4The material (particle size 500nm) was added to 20ml of water with constant stirring, giving L iNi0.5Mn1.5O410ml of CoSO with a concentration of 0.3 mol/L were added in succession4Aqueous solution, 10ml NH with a concentration of 0.3 mol/L4H2PO4Adding the aqueous solution and 10ml of L iOH aqueous solution with the concentration of 1.8 mol/L into the dispersion system, continuously stirring, transferring the obtained mixture into a 100ml polytetrafluoroethylene reaction kettle, preserving the temperature for 10 hours at 180 ℃, collecting powder in a product after the reaction is finished, centrifugally cleaning the powder for 3 times by using water, centrifugally cleaning the powder for one time by using absolute ethyl alcohol, and drying the powder for 3 hours at 80 ℃.
The same characterization as in example 1 was performed, and the results showed that the surface of the positive active material prepared in example 9 was uniformly covered with a layer of lithium phosphate particles having a size of about 5nm at a coverage of 73% at L iNi0.5Mn1.5O4A transition layer containing cobalt element at 0-10 nm below the particle surface, and L iNi0.5Mn1.5O4The particles still have a cubic spinel structure.
Performance testing
The positive active materials prepared in the examples were assembled into a button cell according to the following procedure.
(1) Preparation of Positive electrode sheet
Dispersing the positive active material prepared in the embodiment, carbon black as a conductive additive and polyvinylidene fluoride (PVDF) as a binder in N-methyl pyrrolidone (NMP) according to the weight ratio of 80:10:10, uniformly mixing to prepare uniform positive slurry, uniformly coating the uniform positive slurry on an aluminum foil current collector with the thickness of 15 mu m, drying at 55 ℃ to form a pole piece with the thickness of 100 mu m, and rolling the pole piece under a roller press (the pressure is about 1MPa × 1.5.5 cm)2) Cut into the diameter of
Figure BDA0001396308110000141
Figure BDA0001396308110000142
Then the round piece is placed in a vacuum oven to be dried for 6 hours at the temperature of 120 ℃, and after natural cooling, the round piece is taken out and placed in a glove box to be used as a positive pole piece.
(2) Assembling lithium ion secondary battery
In a glove box filled with inert atmosphere, metallic lithium is taken as the negative electrode of the battery, a PP/PE/PP three-layer film with two sides coated with alumina is taken as a diaphragm and is placed between the positive electrode and the negative electrode, and 1M L iPF is dripped6And (3) dissolving the nonaqueous electrolyte in EC/DMC (volume ratio of 1: 1), and taking the positive pole piece prepared in the step (1) as a positive pole to assemble the button cell with the model number of CR 2032.
Test of examples 1 to 5
(1) High-temperature circulation:
and (3) standing the prepared button cell for 10 hours at room temperature (25 ℃), and then carrying out charge-discharge cycle test on the prepared button cell by using a blue cell charge-discharge tester. The method comprises the steps of firstly cycling at a rate of 0.1C for 1 week under the condition of room temperature (25 ℃), and then continuing cycling at a rate of 0.2C for 4 weeks, wherein the charging and discharging voltage range of the battery is controlled to be 3V-4.3V. Then, the button cell is transferred to a high-temperature environment of 55 ℃, the circulation is continued for 50 weeks at the multiplying power of 0.2C, and the charging and discharging voltage range of the cell is controlled to be still 3V-4.3V.
(2) And (3) room temperature circulation:
and (3) standing the prepared button cell for 10 hours at room temperature (25 ℃), and then carrying out charge-discharge cycle test on the prepared button cell by using a blue cell charge-discharge tester. The method comprises the steps of firstly cycling at a rate of 0.1C for 1 week under the condition of room temperature (25 ℃), and then continuing cycling at a rate of 0.2C for 49 weeks, wherein the charging and discharging voltage range of the battery is controlled to be 3V-4.3V.
Test of examples 6 to 9
(1) High-temperature circulation:
and (3) standing the prepared button cell for 10 hours at room temperature (25 ℃), and then carrying out charge-discharge cycle test on the prepared button cell by using a blue cell charge-discharge tester. The method comprises the steps of firstly cycling at a rate of 0.1C for 1 week under the condition of room temperature (25 ℃), and then continuing cycling at a rate of 0.2C for 4 weeks, wherein the charging and discharging voltage range of the battery is controlled to be 3.5V-4.9V. Then, the button cell is transferred to a high-temperature environment of 55 ℃, the circulation is continued for 50 weeks at the multiplying power of 0.2C, and the charging and discharging voltage range of the cell is still controlled to be 3.5V-4.9V.
(2) And (3) room temperature circulation:
and (3) standing the prepared button cell for 10 hours at room temperature (25 ℃), and then carrying out charge-discharge cycle test on the prepared button cell by using a blue cell charge-discharge tester. The method comprises the steps of firstly cycling at a rate of 0.1C for 1 week under the condition of room temperature (25 ℃), and then continuing cycling at a rate of 0.2C for 49 weeks, wherein the charging and discharging voltage range of the battery is controlled to be 3.5V-4.9V.
Some of the example data measured are shown in table 1, in comparison to the material itself prior to coating with the inventive examples.
TABLE 1 electrochemical Properties of the cathode materials of the examples of the present invention
Figure BDA0001396308110000151
Figure BDA0001396308110000161
In particular, FIG. 10 shows the use of L iMn2O4And the charge-discharge cycle curve of the lithium ion secondary battery of the positive electrode active material of example 3, the results show that L iMn was not coated2O4The capacity of the battery assembled by the material is 98.9mAh/g after 50 weeks under a high-temperature test environment at the temperature of 55 ℃, the retention rate is about 91.5%, and the capacity is quickly attenuated due to the fact that under the high-temperature test environment, electrolyte is decomposed, Mn is dissolved more rapidly, and the capacity of the material is quickly attenuated, and the coating L iMn2O4The capacity of the material after 50 weeks under the high-temperature test environment at 55 ℃ is 104mAh/g, and the retention rate is about 93.1%, which is because L iMn is hindered by lithium phosphate coating2O4Direct contact between the material and the electrolyte, decomposition of the electrolyte and dissolution of Mn are suppressed, resulting in improved cycle stability of the battery.
FIG. 11 shows L iMn2O4And the coulombic efficiency curve of the lithium ion secondary battery of the positive active material of example 3, the result showed L iMn without coating2O4The average coulombic efficiency of the assembled battery after 50 weeks under a high-temperature test environment at 55 ℃ is about 98.9 percent, and the assembled battery is L iMn percent after being coated with lithium phosphate2O4The average coulombic efficiency after 50 weeks in the high temperature test environment of 55 c was about 99.4%. the difference in coulombic efficiency was probably due to inhibition of L iMn by lithium phosphate coating2O4The direct contact between the material and the electrolyte inhibits the decomposition of the electrolyte, thereby improving the cycle stability of the battery.
FIG. 12 shows L iNi0.5Mn1.5O4And example 6, shows the charge-discharge cycle curve of the lithium ion secondary battery with the positive electrode active material of uncoated L iNi0.5Mn1.5O4The capacity of the assembled battery is 109.6mAh/g after 50 weeks under a high-temperature test environment at the temperature of 55 ℃, the retention rate is about 83.98 percent, and the capacity fading is rapid, which is caused by that the capacity fading of the material is rapid due to the fact that the electrolyte is decomposed and Mn is dissolved rapidly under the high-temperature test environment, and L iNi coated with lithium phosphate0.5Mn1.5O4The capacity after 50 weeks under the high temperature test environment of 55 ℃ was 124mAh/g, and the retention rate was about 95.38%, because L iNi was hindered after lithium phosphate coating0.5Mn1.5O4The direct contact with the electrolyte, the decomposition of the electrolyte and the dissolution of Mn are suppressed, thereby improving the cycle stability of the battery.
FIG. 13 shows L iNi0.5Mn1.5O4And the coulombic efficiency curve of the positive active material of example 6 the result showed L iNi without coating0.5Mn1.5O4The average coulombic efficiency of the assembled battery after 50 weeks under a high temperature test environment at 55 ℃ is about 96.5%, and L iNi% after coating lithium phosphate0.5Mn1.5O4The mean coulombic efficiency after 50 weeks in the high temperature test environment of 55 c was about 97.9%. the difference in coulombic efficiency was probably due to inhibition of L iNi by lithium phosphate coating0.5Mn1.5O4The direct contact with the electrolyte suppresses the decomposition of the electrolyte and improves the cycle stability of the battery.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (46)

1. Phosphate-coated spinel structureA positive electrode active material, wherein the positive electrode active material comprises L iMn having a spinel structure2-xAxOyAnd a phosphate coating layer coated on the surface thereof, formula L iMn2-xAxOyWherein A is selected from one or more of Ni, Fe, Co, Ti, Y, Sc, Ru, Cu, Mo, Ge, W, Zr, Ca and Sr, x is more than or equal to 0 and less than or equal to 0.7, and Y is more than or equal to 3.8 and less than or equal to 4.2; and wherein the lithium-containing compound particles have a transition layer containing a diffusion element that diffuses into the lithium-containing compound particles by cladding and thereafter optional calcining;
the phosphate is L i3PO4；
The diffusion element is selected from Fe and/or Co.
2. The positive electrode active material according to claim 1, wherein the chemical formula L iMn2-xAxOyWherein A is selected from Co and Ni.
3. The positive electrode active material according to claim 1, wherein the chemical formula L iMn2-xAxOyIn the formula, x is more than or equal to 0 and less than or equal to 0.5.
4. The positive electrode active material according to claim 3, wherein the chemical formula is L iMn2-xAxOyIn the formula, x is more than or equal to 0.1 and less than or equal to 0.5.
5. The positive electrode active material according to claim 1, wherein the lithium-containing compound particles have a chemical formula of L iMn2O4Or L iNi0.5Mn1.5O4。
6. The positive electrode active material according to claim 1, wherein the lithium-containing compound particles have a particle size of 0.1 to 30 μm.
7. The positive electrode active material according to claim 6, wherein the lithium-containing compound particles have a particle size of 0.2 to 10 μm.
8. The positive electrode active material according to claim 7, wherein the lithium-containing compound particles have a particle size of 0.2 to 0.5 μm.
9. The positive electrode active material according to claim 1, wherein the phosphate coating layer has a thickness of 1 to 50 nm.
10. The positive electrode active material according to claim 9, wherein the phosphate coating layer has a thickness of 5 to 15 nm.
11. The positive electrode active material according to claim 1, wherein the coverage of the phosphate coating layer on the surface of the lithium-containing compound particles is 1 to 100%.
12. The positive electrode active material according to claim 11, wherein the coverage of the phosphate coating layer on the surface of the lithium-containing compound particles is 20 to 90%.
13. The positive electrode active material according to claim 12, wherein the coverage of the phosphate coating layer on the surface of the lithium-containing compound particles is 60 to 80%.
14. The positive electrode active material according to claim 1, wherein the transition layer has a thickness of 0 to 15 μm.
15. The positive electrode active material according to claim 14, wherein the transition layer has a thickness of preferably 0.1 to 5 μm.
16. The positive electrode active material according to claim 15, wherein the transition layer has a thickness of 100 to 250 nm.
17. The positive electrode active material according to claim 1, wherein the transition layer is distributed at a distance of 0 to 10nm from the surface of the lithium-containing compound particle.
18. The positive electrode active material according to claim 17, wherein the transition layer is distributed 0 to 5nm from the surface of the lithium-containing compound particle.
19. The positive electrode active material according to claim 1, wherein a mass ratio of the diffusing element to the phosphate is greater than 0 to 1 or less.
20. The positive electrode active material according to claim 1, wherein the mass ratio of the diffusing element to the phosphate is 0.5 to 1.
21. A method for producing the positive electrode active material according to any one of claims 1 to 20, the method comprising:
(1) dripping phosphoric acid or an ammonium salt solution thereof, a precursor salt solution of a diffusion element and a lithium precursor solution into a dispersion system containing lithium compound particles, and stirring and mixing to obtain a mixture;
(2) transferring the mixture obtained in the step (1) into a closed reaction kettle, and carrying out hydrothermal reaction at 120-250 ℃ for 0.1-20 hours;
(3) cooling the material obtained by the hydrothermal reaction in the step (2) to room temperature, and respectively carrying out centrifugal cleaning by using water and ethanol; and
(4) and (4) drying the cleaned material obtained in the step (3) at 80-150 ℃ for 3-6 hours to obtain the positive active material.
22. The method according to claim 21, wherein the ammonium salt of phosphoric acid in step (1) is monoammonium phosphate and/or diammonium phosphate.
23. The preparation method according to claim 21, wherein the precursor salt of the diffusion element in step (1) is selected from one or more of ferrous sulfate, cobalt nitrate, cobalt chloride and ferrous chloride.
24. The production method according to claim 21, wherein the lithium precursor in step (1) is lithium hydroxide.
25. The production method according to claim 21, wherein the solvent in the solution of phosphoric acid or an ammonium salt thereof, the precursor salt solution of a diffusing element, and the lithium precursor solution in step (1) is water and/or ethanol.
26. The production method according to claim 21, wherein the solvent of the dispersion system of the lithium-containing compound particles is water and/or ethanol.
27. The production method according to claim 21, wherein the phosphoric acid or the ammonium salt thereof, the precursor salt of the diffusing element and the lithium precursor in step (1) are added in the following proportions: the molar ratio of phosphorus, diffusion element and lithium is 1: 0.5-2: 0.5 to 6.
28. The production method according to claim 27, wherein the phosphoric acid or the ammonium salt thereof, the precursor salt of the diffusing element and the lithium precursor in step (1) are added in the following proportions: the molar ratio of phosphorus, diffusion element and lithium is 1: 0.5-1: 3 to 6.
29. The method according to claim 21, wherein the concentration of the phosphoric acid or its ammonium salt solution in the step (1) is 0.1 mol/L to 0.3 mol/L.
30. The production method according to claim 21, wherein the concentration of the precursor salt solution of the diffusing element in the step (1) is 0.1 mol/L to 0.3 mol/L.
31. The preparation method of claim 21, wherein the concentration of the lithium precursor solution in the step (1) is 0.3 mol/L-1.8 mol/L.
32. The method according to claim 31, wherein the concentration of the lithium precursor solution in the step (1) is 0.3 mol/L-0.9 mol/L.
33. The production method according to claim 21, wherein the mass fraction of the lithium-containing compound particles in the dispersion of lithium-containing compound particles in step (1) is 30 to 50 wt%.
34. The method according to claim 21, wherein the hydrothermal reaction in the step (2) is carried out at a temperature of 150 to 200 ℃.
35. The method according to claim 34, wherein the temperature of the hydrothermal reaction in the step (2) is 180 ℃.
36. The method according to claim 21, wherein the hydrothermal reaction time in the step (2) is 5 to 15 hours.
37. The production method according to claim 36, wherein the hydrothermal reaction time in the step (2) is 10 hours.
38. The method of manufacturing of claim 21, wherein the method of manufacturing further comprises:
(5) and (4) calcining the positive electrode active material obtained in the step (4) at 350-900 ℃ for 0.1-10 hours to obtain the sintered positive electrode active material.
39. The method according to claim 38, wherein the calcination temperature in the step (5) is 450 to 700 ℃.
40. The method according to claim 38, wherein the calcination in the step (5) is carried out for 1 to 5 hours.
41. The production method according to claim 39, wherein the calcination in the step (5) is carried out for 3 hours.
42. The production method according to claim 38, wherein the calcination in step (5) is carried out under oxygen, air, an atmosphere containing a reducing gas, or an inert atmosphere.
43. Use of the positive electrode active material according to any one of claims 1 to 20 in a lithium ion secondary battery.
44. A positive electrode for a lithium ion secondary battery, comprising a current collector and a positive electrode active material according to any one of claims 1 to 20 supported on the current collector.
45. A lithium ion secondary battery comprising the positive electrode of claim 44, a negative electrode, a separator and an electrolyte.
46. The lithium ion secondary battery of claim 45, wherein the battery further comprises a casing, wherein the positive electrode, the negative electrode, the separator, and the electrolyte are sealed within the casing.
CN201710778059.7A 2017-09-01 2017-09-01 Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof Active CN107528059B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201710778059.7A CN107528059B (en) 2017-09-01 2017-09-01 Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201710778059.7A CN107528059B (en) 2017-09-01 2017-09-01 Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof

Publications (2)

Publication Number Publication Date
CN107528059A CN107528059A (en) 2017-12-29
CN107528059B true CN107528059B (en) 2020-08-04

Family

ID=60683231

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201710778059.7A Active CN107528059B (en) 2017-09-01 2017-09-01 Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof

Country Status (1)

Country Link
CN (1) CN107528059B (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019215083A1 (en) * 2018-05-09 2019-11-14 Haldor Topsøe A/S Doped lithium positive electrode active material and process for manufacture thereof
CN109659538B (en) * 2018-12-19 2022-04-05 上海纳米技术及应用国家工程研究中心有限公司 Preparation of rich lithium manganese-based oxide material based on coating of dopamine and lithium phosphate, product and application thereof
CN109904424B (en) * 2019-02-28 2020-09-11 河南大学 Method for one-step surface coating and gradient doping integrated double-modification of LNMO (Low noise Metal oxide) positive electrode material
CN112151773B (en) * 2019-06-26 2022-05-24 中国科学院物理研究所 Positive active material, preparation method thereof and lithium battery
CN112038609A (en) * 2020-09-11 2020-12-04 广西师范大学 Lithium iron phosphate surface-modified spinel type lithium nickel manganese oxide positive electrode material and preparation method thereof
CN114506830B (en) * 2020-11-17 2023-07-14 松山湖材料实验室 Preparation method of phosphate coated positive electrode active material

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103928664A (en) * 2014-04-29 2014-07-16 哈尔滨工业大学 Lithium-enriched manganese-based anode material with fast ion conductor coating layer and surface heterostructure and preparation method of lithium-enriched manganese-based anode material
CN105261740A (en) * 2015-11-24 2016-01-20 宁德新能源科技有限公司 Lithium battery cathode material, preparation method thereof and lithium battery including same
CN105932250A (en) * 2016-06-03 2016-09-07 中南大学 Preparation method and application of metal doped spinel structured and fast ionic conductor coated nickel-containing cathode material
CN106099082A (en) * 2016-08-31 2016-11-09 四川剑兴锂电池有限公司 The surface cladding type nickel ion doped material of a kind of hydro-thermal method modification, lithium battery and preparation method thereof
CN106299339A (en) * 2016-09-27 2017-01-04 中国科学院大学 A kind of preparation method of lithium ion conductor coating spinelle manganate cathode material for lithium

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1595687A (en) * 2003-09-08 2005-03-16 中国科学院物理研究所 A positive electrode material for lithium secondary cell, and preparation and usage thereof
US8187746B2 (en) * 2008-05-16 2012-05-29 Uchicago Argonne, Llc Surface modification agents for lithium batteries
CN103022485A (en) * 2012-12-19 2013-04-03 苏州大学 Lithium manganese phosphate-clad lithium manganate lithium secondary battery anode material and preparation method thereof
CN103594683B (en) * 2013-11-13 2015-08-05 北京理工大学 A kind of coating modification method preparing high temp. lithium ion battery manganate cathode material for lithium
CN106099083A (en) * 2016-08-31 2016-11-09 四川剑兴锂电池有限公司 The cladded type nickel ion doped material of a kind of hydro-thermal method surface modification, lithium battery and preparation method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103928664A (en) * 2014-04-29 2014-07-16 哈尔滨工业大学 Lithium-enriched manganese-based anode material with fast ion conductor coating layer and surface heterostructure and preparation method of lithium-enriched manganese-based anode material
CN105261740A (en) * 2015-11-24 2016-01-20 宁德新能源科技有限公司 Lithium battery cathode material, preparation method thereof and lithium battery including same
CN105932250A (en) * 2016-06-03 2016-09-07 中南大学 Preparation method and application of metal doped spinel structured and fast ionic conductor coated nickel-containing cathode material
CN106099082A (en) * 2016-08-31 2016-11-09 四川剑兴锂电池有限公司 The surface cladding type nickel ion doped material of a kind of hydro-thermal method modification, lithium battery and preparation method thereof
CN106299339A (en) * 2016-09-27 2017-01-04 中国科学院大学 A kind of preparation method of lithium ion conductor coating spinelle manganate cathode material for lithium

Also Published As

Publication number Publication date
CN107528059A (en) 2017-12-29

Similar Documents

Publication Publication Date Title
US11742482B2 (en) Nickel-based active material for lithium secondary battery, method of preparing the same, and lithium secondary battery including positive electrode including the nickel-based active material
CN107528059B (en) Phosphate-coated spinel-structured positive electrode active material and preparation method and application thereof
US9831497B2 (en) Method of manufacturing active material particles
EP3331069B1 (en) Nonaqueous electrolyte secondary battery positive electrode active material and nonaqueous electrolyte secondary battery
US11355745B2 (en) Nickel active material precursor for lithium secondary battery, method for producing nickel active material precursor, nickel active material for lithium secondary battery produced by method, and lithium secondary battery having cathode containing nickel active material
US20220376245A1 (en) Nickel-based active material precursor for lithium secondary battery, method of preparing the same, nickel-based active material for lithium secondary battery formed therefrom, and lithium secondary battery including positive electrode including nickel-based active material
KR101920484B1 (en) Positive active material precursor and preparation method thereof, positive active material and lithium secondary battery comprising the same
Zhang et al. Significant improvement on electrochemical performance of LiMn2O4 at elevated temperature by atomic layer deposition of TiO2 nanocoating
KR20200106043A (en) Anode material for rechargeable lithium-ion batteries
US20010031397A1 (en) Positive active material for rechargeable lithium battery and method of preparing same
CN112151773B (en) Positive active material, preparation method thereof and lithium battery
JP5731276B2 (en) Positive electrode active material for lithium secondary battery, method for producing the same, and lithium secondary battery
EP3267517A1 (en) Positive electrode active substance for non-aqueous electrolyte secondary battery, and method for producing same
KR20020077555A (en) Positive electrode for lithium secondary battery and method of preparing same
CN111193018B (en) Lithium battery positive active material and preparation method and application thereof
Wu et al. Surface modification of a cobalt-free layered Li [Li 0.2 Fe 0.1 Ni 0.15 Mn 0.55] O 2 oxide with the FePO 4/Li 3 PO 4 composite as the cathode for lithium-ion batteries
KR20180065385A (en) Negative electrode for rechargeable battery and method for manufacturing the same
KR101844631B1 (en) Positive electrode material and method for preparing the same
KR20160134317A (en) Positive active material and manufacturing method thereof, positive electrode and lithium battery containing the material
CN116022771B (en) Hard carbon material, negative electrode plate and electrochemical device
CN110556531A (en) Anode material, preparation method thereof and lithium ion battery containing anode material
CN115084505A (en) Positive electrode active material and electrochemical device
CN114512660B (en) Positive active material precursor, preparation method thereof and positive active material
CN114899371B (en) Low-water-content positive electrode material, preparation method thereof and lithium ion battery
CN109817968B (en) Surface-coated lithium nickel manganese oxide particles and method for producing same

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant