WO2024011602A1 - 锰酸锂复合材料及其制备方法、二次电池和用电装置 - Google Patents

锰酸锂复合材料及其制备方法、二次电池和用电装置 Download PDF

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WO2024011602A1
WO2024011602A1 PCT/CN2022/106039 CN2022106039W WO2024011602A1 WO 2024011602 A1 WO2024011602 A1 WO 2024011602A1 CN 2022106039 W CN2022106039 W CN 2022106039W WO 2024011602 A1 WO2024011602 A1 WO 2024011602A1
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Prior art keywords
lithium manganate
composite material
manganate composite
core particles
coating
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PCT/CN2022/106039
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English (en)
French (fr)
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秦猛
赵玉珍
官英杰
温严
黄起森
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/106039 priority Critical patent/WO2024011602A1/zh
Priority to CN202280063068.7A priority patent/CN118043996A/zh
Publication of WO2024011602A1 publication Critical patent/WO2024011602A1/zh

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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
    • H01M4/50—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
    • 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

Definitions

  • the present application relates to the field of batteries, specifically to a lithium manganate composite material and its preparation method, secondary batteries and electrical devices.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide a lithium manganate composite material and a preparation method thereof, a secondary battery, and an electrical device.
  • the first aspect of the present application provides a lithium manganate composite material for secondary batteries.
  • the lithium manganate composite material includes core particles and a coating layer; the molecular formula of the core particles is Li 1+x Mn 2-y M y O 4-Z A z , in the molecular formula, -0.2 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 0.1, 0 ⁇ Z ⁇ 0.1, M includes Mg, Al, Ge, Fe, Zn, Co, Ni, Cr, Mo , one or more of Nb and Sn, A includes one or more of F, Cl and S; the coating layer covers at least part of the outer surface of the core particles, and the coating layer includes organic phosphoric acid or its salt kind.
  • the coating layer containing organic phosphoric acid or its salts in the present application is disposed on the outer surface of the core particles, which can isolate at least part of the core particles from the electrolyte, thereby reducing the risk of side reactions caused by the contact between the electrolyte and the core particles. , thereby reducing the risk of nuclear particle damage caused by electrolyte corrosion, thereby providing a good protective effect on the nuclear particles and ensuring the structural stability of the nuclear particles.
  • Organophosphoric acid or its salts easily react with hydrofluoric acid HF in the electrolyte, reducing the corrosive effect of hydrofluoric acid HF on the core particles, thus reducing the dissolution of transition metals such as manganese in the core particles.
  • the SEI film can play a good protective role on the negative active material and ensure the cycle stability of the negative active material, which can further improve the secondary Battery capacity performance, storage performance and cycle performance.
  • the organophosphoric acid or salt thereof includes a phosphonic acid group, and the number of phosphonic acid groups is denoted as n, 2 ⁇ n ⁇ 4; optionally, 2 ⁇ n ⁇ 3.
  • the organic phosphoric acid or its salts of the present application contain the above number of phosphoric acid groups, the ability to stabilize the manganese element can be further improved; and the acidity of the organic phosphoric acid or its salts will not be too high and will not cause damage to the core particles. destroy.
  • the organic phosphoric acid or salt thereof includes aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hydroxyethylene diphosphonic acid, aminoethylene diphosphonic acid, methylamine dimethylene Phosphonic acid, hexamethylene diamine tetramethylene phosphonic acid, hydroxypropylidene diphosphonic acid, aminopropyl phosphonic acid, hexamethylene diamine tetramethylene phosphonic acid potassium salt, hydroxyethylene diphosphonic acid sodium salt, hydroxyl One or more of ethylene diphosphonic acid potassium salt, nitroso trimethylene phosphonic acid and imino dimethylene phosphonic acid.
  • the coating layer coats the outer surface of the core particles in a continuous layered form.
  • the coating layer can fully protect the nuclear particles, isolate the nuclear particles from the electrolyte, reduce the risk of the electrolyte corroding the nuclear particles, thereby ensuring the cycle stability of the nuclear particles.
  • the cladding layer includes a first region portion and a second region portion connected to each other; the average thickness of the first region portion is denoted H 1 nm, the average thickness of the second region portion is denoted H 2 nm, and the manganese Lithium acid composite materials satisfy: 1 ⁇ H 1 /H 2 ⁇ 3.
  • the average thickness of the first region part and the second region part of the present application is different, which is reflected in the fact that the average thickness of the first region part is greater than the average thickness of the second region part; the average thickness of different regions of the coating layer is different, which can be On the basis of ensuring the protection of nuclear particles, the impedance of the coating layer can be reduced, thereby improving the dynamic performance of the secondary battery; and this structure of the coating layer can also reduce the hydrogen fluoride in the nuclear particles and the electrolyte The risk of acid HF reaction further improves the kinetic performance of secondary batteries.
  • the coating rate of the coating layer is recorded as S%, and the coating rate is the percentage of the total area of the coating layer occupying the outer surface area of the core particles; the lithium manganate composite material satisfies: 50 ⁇ S ⁇ 95; Optionally, 50 ⁇ S ⁇ 80.
  • the coating layer can cover most of the outer surface of the core particles, thereby fully protecting the core particles; and the impedance of the coating layer is relatively low. Small.
  • the resistance of the process of lithium ions migrating from the core particles to the negative active material is small, and the resistance of the process of lithium ions migrating from the negative active material to the core particles is small, which can improve the secondary battery. Battery kinetic properties.
  • the mass percentage of the coating layer is recorded as P%, and the lithium manganate composite material satisfies: 0.01 ⁇ P ⁇ 5; optionally, 0.1 ⁇ P ⁇ 2.
  • the coating layer can fully protect the core particles and ensure the smooth migration of lithium ions, thereby ensuring the dynamic performance of the secondary battery. .
  • the core particles satisfy: -0.1 ⁇ x ⁇ 1.5, 0.001 ⁇ y ⁇ 0.06, 0.001 ⁇ Z ⁇ 0.05; and/or M includes one or more of Mg, Al and Sn, and A includes F and/or S.
  • the core particles of the above molecular formula and the coating layer cooperate with each other.
  • the coating layer can fully protect the core particles, and the core particles can provide a higher specific capacity for the secondary battery to improve the capacity of the secondary battery.
  • the pH value of the lithium manganate composite material satisfies: 6 ⁇ pH ⁇ 8; optionally, 6.5 ⁇ pH ⁇ 7.5.
  • the pH value of the lithium manganate composite material is within the above range, on the one hand, the pH value will not be too high, which can reduce the risk of gel formation on the surface of the lithium manganate composite material, thus ensuring the smooth migration of lithium ions, thus improving the secondary The kinetic performance of the battery; on the other hand, the pH value will not be too low, which can reduce the damage to the core particles and ensure the cycle stability of the core particles, thus improving the cycle stability of the secondary battery.
  • the specific surface area of the lithium manganate composite material is recorded as BET g/cm 3 , and BET ⁇ 1.
  • the contact area between the lithium manganate composite material and the electrolyte is relatively small, and the contact interface between the lithium manganate composite material and the electrolyte can be reduced, thereby Reduce the risk of side reactions at the interface between the two.
  • the manganese in the core particles is not easy to dissolve, which can ensure the overall structural stability of the lithium manganate composite material, thereby improving the kinetic performance and cycle performance of the secondary battery.
  • the second aspect of the application also provides a method for preparing lithium manganate composite materials.
  • the method includes: S100, providing a solvent and a coating material containing organic phosphoric acid or its salts, and mixing the solvent and the coating material to form a coating.
  • the preparation method of the present application has a simple preparation process, and the prepared coating layer can fully protect the core particles and reduce the dissolution of transition metals in the core particles, so that the prepared lithium manganate composite material can be used in When used in secondary batteries, it can improve the capacity performance, cycle performance and storage performance of secondary batteries.
  • the solvent includes one or more of water, ethanol, and methanol.
  • this application can control the morphology of the coating layer formed by selecting the solvent.
  • the morphology of the coating layer can include the thickness of the coating layer, for example, films of different thicknesses can be formed in different areas of the coating layer. layer.
  • the mass ratio of the solvent and the coating material is denoted by Q, 0 ⁇ Q ⁇ 0.1; and/or the mass ratio of the solvent and the core particles is denoted by N, 0 ⁇ N ⁇ 0.7.
  • Q mass ratio between the solvent and the coating material
  • N mass ratio of the solvent and the core particles
  • the solvent can fully dissolve the coating material, which is more conducive to coating the surface of the core particles with the coating material.
  • N of the solvent to the core particles meets the above range
  • the amount of solvent used can fully dissolve the coating material and coat the surface of the core particles with the coating material, and the solvent evaporation process is conducive to forming a non-thickness coating on the surface of the core particles.
  • a uniform coating layer is conducive to further improving the dynamic performance of secondary batteries.
  • the curing temperature is 80°C to 120°C.
  • the curing temperature of this application is lower, and while the solvent is volatilizing, it will not cause damage to the coating layer and core particles, thereby ensuring the stability of the overall structure of the lithium manganate composite material, thereby ensuring that the lithium manganate composite material Cycling stability when applied to secondary batteries.
  • the third aspect of the application also provides a secondary battery.
  • the secondary battery includes a positive electrode sheet, and the positive electrode sheet includes a lithium manganate composite material according to any embodiment of the first aspect of the application or any embodiment of the second aspect. Lithium manganate composite material obtained by this method.
  • the fourth aspect of the present application also provides an electrical device, including the secondary battery according to the embodiment of the third aspect of the present application.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the positive electrode active material is the one that intercalates lithium compounds and provides active lithium ions.
  • the stability of its material structure has a direct impact on the overall performance of the lithium-ion battery.
  • the trace amount of moisture present in the electrolyte easily reacts with the lithium salts in the electrolyte such as LiPF 6 to form hydrofluoric acid HF.
  • the presence of HF makes the positive electrode active material prone to side reactions, causing the transition metals in the positive electrode active material to dissolve into the electrolyte.
  • the dissolution of transition metals will cause damage to the positive active material.
  • the transition metal migrates to the negative active material it may cause damage to the Solid Electrolyte Interface (SEI) film on the surface of the negative active material.
  • SEI Solid Electrolyte Interface
  • Destruction may cause the structure of the negative active material to be damaged, deteriorating the capacity performance, storage performance and cycle performance of the secondary battery.
  • the positive active material as lithium manganate as an example
  • HF in the electrolyte causes a disproportionation reaction of lithium manganate to generate Mn 2+ .
  • the disproportionation reaction causes the crystal lattice of lithium manganate to change
  • Mn 2+ It is reduced to metal Mn on the surface of the negative electrode active material, catalytically decomposes the SEI film and destroys the interface of the negative electrode active material, and Mn may also block the lithium insertion channel of the negative electrode active material, and Mn may even be deposited at the interface between the negative electrode current collector and the negative electrode active material.
  • the various factors mentioned above may cause the capacity of the secondary battery to attenuate, and the storage performance and cycle performance of the secondary battery to deteriorate.
  • the inventor considered protecting the positive electrode active material such as lithium manganate material and ensuring the structural stability of the positive electrode active material.
  • the inventor provided a coating layer on the surface of the positive electrode active material such as lithium manganate material.
  • the coating layer contains organic phosphoric acid or its salts, thereby providing good protection for the positive electrode active material, and is conducive to the formation of a good positive electrode solid electrolyte interface film (Cathode Electrolyte Interface, CEI film), which can further protect the positive electrode active material. Protective effect, thereby improving the capacity performance, storage performance and cycle performance of secondary batteries.
  • CEI film Cathode Electrolyte Interface
  • this application proposes a lithium manganate composite material.
  • the lithium manganate composite material includes core particles and a coating layer.
  • the molecular formula of the core particles is Li 1+x Mn 2-y My O 4-Z.
  • a z in the molecular formula, -0.2 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 0.1, 0 ⁇ Z ⁇ 0.1, M includes Mg, Al, Ge, Fe, Zn, Co, Ni, Cr, Mo, Nb and Sn
  • A includes one or more of F, Cl and S
  • the coating layer covers at least part of the outer surface of the core particles, and the coating layer includes organic phosphoric acid or its salts.
  • Organophosphoric acid refers to a compound in which two or more phosphorus atoms in the phosphonic acid group are directly connected to carbon atoms.
  • Organophosphates refer to compounds in which the hydrogen atoms in the phosphonic acid group of organophosphates are replaced by metal cations.
  • the lithium manganate composite material of the present application can improve the capacity performance, storage performance and cycle performance of the secondary battery when used in secondary batteries; the inventor speculates that the reasons may be as follows:
  • the coating layer containing organic phosphoric acid or its salt is disposed on the outer surface of the core particles, which can isolate at least part of the core particles from the electrolyte, thereby reducing the risk of side reactions occurring in contact between the electrolyte and the core particles, thereby reducing the electrolyte Corrosion of nuclear particles causes the risk of nuclear particle damage, thereby providing a good protective effect on nuclear particles and ensuring the structural stability of nuclear particles.
  • the inventor speculates that the coating layer containing organic phosphoric acid or its salts may also promote the formation of a CEI film on the surface of the lithium manganate composite material.
  • the CEI film can further protect the overall lithium manganate composite material.
  • the CEI film always maintains a dense and stable state, which can continuously protect the lithium manganate composite material, thereby further ensuring the structural stability of the lithium manganate composite material.
  • the material When the material is used in secondary batteries, it can improve the capacity performance, storage performance and cycle performance of the secondary battery.
  • Organophosphoric acid or its salts easily react with hydrofluoric acid HF in the electrolyte, reducing the corrosive effect of hydrofluoric acid HF on the core particles, thus reducing the dissolution of transition metals such as manganese in the core particles.
  • Manganese in the electrolyte moves to The content of negative active material migration is significantly reduced, and the SEI film on the surface of the negative active material is not easily damaged.
  • the SEI film can play a good protective role on the negative active material and ensure the cycle stability of the negative active material, which can further improve the secondary Battery capacity performance, storage performance and cycle performance.
  • Organophosphoric acid or its salts may undergo a complex reaction with transition metals such as manganese, thereby stabilizing manganese on core particles and reducing the risk of manganese dissolving into the electrolyte, thereby further improving the capacity performance and storage performance of secondary batteries and Cycle performance.
  • the organic phosphoric acid or salts thereof include phosphonic acid groups, and the number of phosphonic acid groups is denoted as n, 2 ⁇ n ⁇ 4.
  • organic phosphoric acid or its salts contain the above number of phosphate groups, the ability to stabilize manganese element can be further improved; and the acidity of organic phosphoric acid or its salts will not be too high and will not cause damage to the core particles.
  • organic phosphoric acids or salts thereof may include aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hydroxyethylenediphosphonic acid, aminoethylenediphosphonic acid, methylaminedimethylenephosphine Acid, hexamethylenediaminetetramethylenephosphonic acid, hydroxypropylidene diphosphonic acid, aminopropylphosphonic acid, hexamethylenediaminetetramethylenephosphonic acid potassium salt, hydroxyethylene diphosphonic acid sodium salt, hydroxyethylene One or more of potassium diphosphonic acid, nitroso trimethylene phosphonic acid and imino dimethylene phosphonic acid.
  • the above-mentioned organic phosphoric acid or its salts can play a good protective role on the core particles, thereby ensuring the cycle stability of the lithium manganate composite material.
  • the coating layer coating the core particles has various structural forms.
  • the coating layer coats the outer surface of the core particles in a continuous layered form.
  • the coating layer can fully protect the nuclear particles, isolate the nuclear particles from the electrolyte, reduce the risk of the electrolyte corroding the nuclear particles, thereby ensuring the cycle stability of the nuclear particles.
  • the coating layer can also be coated on the outer surface of the core particles in a discretely distributed layered form.
  • the organic phosphoric acid or its salts in the coating layer can stabilize the manganese in the core particles and reduce the dissolution of manganese. into the electrolyte to ensure the circulation stability of the core particles.
  • the cladding layer includes a first region portion and a second region portion connected to each other, the average thickness of the first region portion is denoted as H 1 nm, the average thickness of the second region portion is denoted as H 2 nm, and the manganese
  • the lithium acid composite material satisfies 1 ⁇ H 1 /H 2 ⁇ 3.
  • the average thickness of the first region and the second region are different, which is reflected in the fact that the average thickness of the first region is greater than the average thickness of the second region; the average thickness of different regions of the coating layer is different, which can ensure the protection of the core particles.
  • the impedance of the coating layer can be reduced, thereby improving the dynamic performance of the secondary battery; and the structure of the coating layer can also reduce the risk of reaction between nuclear particles and hydrofluoric acid HF in the electrolyte. Further improve the kinetic performance of secondary batteries.
  • the first area part and the second area part are both components of the cladding layer, but there is no obvious boundary between the first area part and the second area part. They form a continuous structure.
  • the average thickness of the first zone portion and the second zone portion can be adjusted by adjusting process parameters such as the type or concentration of solvent.
  • the average thickness of the first region can be measured using testing methods and testing instruments known in the art, specifically as follows: a transmission electron microscope can be used to obtain a Transmission Electron Microscope (TEM) picture of the first region. , and then measure the average thickness at multiple (for example, more than 30) different locations on the TEM image, and take the average value as the average thickness H 1 of the first region.
  • TEM Transmission Electron Microscope
  • the average thickness of the second region can be measured using testing methods and testing instruments known in the art, specifically as follows: a transmission electron microscope can be used to obtain a TEM picture of the second region, and then the thickness of the second region can be measured on the TEM picture. The average thickness of several (for example, more than 30) different locations is taken as the average thickness H 2 of the second region.
  • the coating rate of the coating layer is recorded as S%; the lithium manganate composite material satisfies: 50 ⁇ S ⁇ 95.
  • the coating layer can cover most of the outer surface of the core particles, thereby fully protecting the core particles; and the impedance of the coating layer is relatively small.
  • the resistance during the migration of lithium ions from the core particles to the negative active material is small, and the resistance during the migration of lithium ions from the negative active material to the core particles is small, which can improve the power of the secondary battery. academic performance.
  • 50 ⁇ S ⁇ 80 for example, the coating rate S% of the coating layer can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90 % or 95%; or a range consisting of any two of the above values.
  • the coating rate refers to the percentage of the total area of the coating layer to the outer surface area of the core particle; it can be detected using test methods and test instruments known in the art, such as a scanning electron microscope (scanning electron microscope). , SEM) to observe the micromorphology of the lithium manganate composite material and core particles to calculate the coating rate.
  • the mass percentage of the coating layer is recorded as P%, and the lithium manganate composite material satisfies: 0.01 ⁇ P ⁇ 5.
  • the coating layer can fully protect the nuclear particles and ensure the smooth migration of lithium ions, thereby ensuring the dynamic performance of the secondary battery.
  • the mass percentage P% of the coating layer can be 0.01%, 0.02%, 0.05%, 0.08%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.50%, 0.80%, 1 %, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%; or a range consisting of any two of the above numerical ranges.
  • the molecular formula of the core particle is Li 1+x Mn 2-y M y O 4-Z Az , -0.1 ⁇ x ⁇ 1.5, 0.001 ⁇ y ⁇ 0.06, 0.001 ⁇ Z ⁇ 0.05; and/or M includes one or more of Mg, Al and Sn, and A includes F and/or S.
  • the core particles of the above molecular formula and the coating layer cooperate with each other.
  • the coating layer can fully protect the core particles, and the core particles can provide a higher specific capacity for the secondary battery to improve the capacity of the secondary battery.
  • the pH value of the lithium manganate composite material satisfies: 6 ⁇ pH ⁇ 8.
  • the pH value of the lithium manganate composite material When the pH value of the lithium manganate composite material is within the above range, on the one hand, the pH value will not be too high, which can reduce the risk of gel formation on the surface of the lithium manganate composite material, thus ensuring the smooth migration of lithium ions, thus improving the secondary The kinetic performance of the battery; on the other hand, the pH value will not be too low, which can reduce the damage to the core particles and ensure the cycle stability of the core particles, thus improving the cycle stability of the secondary battery.
  • 6.5 ⁇ pH ⁇ 7.5 For example, the pH value of the lithium manganate composite material can be 6, 6.5, 7, 7.5 or 8; or within the range of any two of the above values.
  • the pH value of the material is a well-known meaning in the art, and can be tested using instruments and methods well-known in the art.
  • the material and solvent are added into an Erlenmeyer flask at a ratio of 1:9, and magnetic force is used to measure the pH value. Stir with a stirrer for 30 minutes. After stirring, let it stand for 1.5 hours. Test with a magnetic acidity meter at 15-28°C and humidity ⁇ 80%. The average of the three tests is taken as the pH value of the material.
  • the specific surface area of the lithium manganate composite material is expressed as BET g/cm 3 , and BET ⁇ 1.
  • the contact area between the lithium manganate composite material and the electrolyte is relatively small, which can reduce the contact interface between the lithium manganate composite material and the electrolyte, thereby reducing the occurrence of the two at the interface.
  • the risk of side reactions is that the manganese in the core particles is not easily eluted, which can ensure the overall structural stability of the lithium manganate composite material, thereby improving the kinetic performance and cycle performance of the secondary battery.
  • BET can be 1g/cm 3 , 0.8g/cm 3 , 0.6g/cm 3 , 0.5g/cm 3 , 0.4g/ cm 3 , 0.2g/cm 3 or 0.1g/cm 3 ; or A range consisting of any two of the above values.
  • the specific surface area of a material has a well-known meaning in the art, and can be tested using instruments and methods well-known in the art.
  • the nitrogen adsorption specific surface area analysis test can pass the Tri-Star 3020 type specific surface area of the American Micromeritics company. Pore size analysis tester.
  • lithium manganate composite materials can be used as positive electrode active materials in secondary batteries.
  • the above various parameter tests for lithium manganate composite materials can be done by sampling and testing before coating, or from the positive electrode after cold pressing. Sample testing from the film layer.
  • the sampling can be carried out as follows: randomly select a cold-pressed positive electrode film layer and sample the lithium manganate composite material (For example, you can use a blade scraper for powder sampling); place the lithium manganate composite powder collected above in deionized water, then filter and dry it, and then put the dried lithium manganate composite material at a certain temperature and After sintering for a certain time (for example, 400°C, 2 hours), the binder and conductive agent are removed, and a test sample of the lithium manganate composite material is obtained.
  • a certain time for example, 400°C, 2 hours
  • this application proposes a method for preparing lithium manganate composite materials.
  • Methods include:
  • S100 provides a solvent and a coating material containing organic phosphoric acid or its salts, and mixes the solvent and the coating material into a coating slurry;
  • the molecular formula of the core particle is Li 1+x Mn 2-y M y O 4-Z A z .
  • M includes Mg, One or more of Al, Ge, Fe, Zn, Co, Ni, Cr and Sn, and A includes one or more of F, Cl and S.
  • the preparation method of the present application has a simple preparation process, and the prepared coating layer can fully protect the core particles and reduce the dissolution of transition metals in the core particles, so that the prepared lithium manganate composite material can be used in secondary applications. When used as a battery, it can improve the capacity performance, cycle performance and storage performance of secondary batteries.
  • the preparation method of the present application can be used to prepare the lithium manganate composite material of any embodiment of the first aspect of the present application.
  • the solvent includes one or more of water, ethanol, and methanol.
  • the morphology of the formed coating layer can be controlled by selecting the solvent.
  • the morphology of the coating layer can include the thickness of the coating layer, for example, film layers of different thicknesses are formed in different areas of the coating layer. Taking water as the solvent as an example, the coating material is dissolved in water and mixed, and then dried by suction filtration, press filtration or centrifugation, so that coating layers with different thicknesses in different areas can be obtained.
  • the coating layer includes a first layer. The thickness of the first region part is greater than the thickness of the second region part.
  • the solvation structure of the coating material in water, or the dissolution state of the coating material in water causes the solvent to coat the material during the evaporation process.
  • the aggregation state on the surface of the core particle may be different, so that different areas on the surface of the core particle are coated with coating layers of different thicknesses.
  • this application uses suction filtration, pressure or centrifugation to dry the solvent, so that the content of residual solvent on the surface of the core particles is less.
  • the coating material may not migrate in time on the surface of the core particles. That is, the coating material is unevenly distributed on the surface of the core particles, so that the coating layer on the surface of the core particles is thicker in some areas and thinner in some areas, which is beneficial to improving the dynamic performance of the secondary battery.
  • the solvent drying process of this application can also use direct heat treatment to volatilize the solvent; for example, the coating slurry is placed in a wet wrapping machine, and the solvent and coating material are stirred at 80 to 100°C under an inert non-oxidizing gas atmosphere. , so that the coating material is dissolved in the solvent and coated on the core particles, and at the same time, the solvent can be volatilized, thereby forming a coating layer on the surface of the core particles.
  • the mass ratio of the solvent and the coating material is denoted as Q, 0 ⁇ Q ⁇ 0.1.
  • the solvent can fully dissolve the coating material, which is more conducive to coating the surface of the core particles with the coating material.
  • the mass ratio Q of the solvent and the coating material can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1; or a range consisting of any two of the above values.
  • the ratio of the mass percentage of the solvent to the mass percentage of the coating material is Q.
  • the mass ratio of the solvent to the coating material can be considered as the ratio of the mass percentage of the solvent to the mass percentage of the coating material based on the total mass of the coating material.
  • the mass ratio of solvent and core particles is denoted as N, 0 ⁇ N ⁇ 0.7.
  • the mass ratio N of the solvent to the core particles meets the above range, the amount of solvent used can fully dissolve the coating material and coat the surface of the core particles with the coating material, and the solvent evaporation process is conducive to forming a non-thickness coating on the surface of the core particles.
  • a uniform coating layer is conducive to further improving the dynamic performance of secondary batteries.
  • the mass ratio N of the solvent and the core particles can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 or 0.07; or a range consisting of any two of the above values.
  • the ratio of the mass percentage of the solvent to the mass percentage of the core particles is N.
  • the curing temperature is 80°C to 120°C.
  • the curing temperature of this application is low, and while evaporating the solvent, it will not cause damage to the coating layer and core particles, thereby ensuring the stability of the overall structure of the lithium manganate composite material, thereby ensuring that the lithium manganate composite material is used in secondary applications. Cycling stability in secondary batteries.
  • the curing temperature may be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C; or a range consisting of any two of the above values.
  • this application proposes a secondary battery.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • the secondary battery includes a positive electrode plate, a negative electrode plate and a separator.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows metal ions to pass through.
  • the electrolyte plays a role in conducting metal ions between the positive electrode piece and the negative electrode piece.
  • the secondary battery of the present application may be a lithium secondary battery, a sodium-ion battery, or the like, and in particular, may be a lithium-ion secondary battery.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material adopts the lithium manganate composite material according to any embodiment of the first aspect of the application or the manganate prepared by the method of any embodiment of the second aspect of the application.
  • Cathode active materials can significantly improve the performance of secondary batteries.
  • the cathode active material may also be a cathode active material known in the art for secondary batteries.
  • the cathode active material may include at least one of a lithium transition metal oxide, an olivine-structured lithium-containing phosphate, and their respective modified compounds.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium At least one of nickel cobalt aluminum oxides and their respective modified compounds.
  • lithium-containing phosphates with an olivine structure may include lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon. At least one of the composite materials and their respective modifying compounds.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • the positive active material may be a layered material, such as a ternary material, a lithium/sodium nickelate material, a lithium cobaltate/sodium material, a lithium/sodium manganate material, a rich lithium/sodium layered material, or a rock salt phase layered material.
  • a layered material such as a ternary material, a lithium/sodium nickelate material, a lithium cobaltate/sodium material, a lithium/sodium manganate material, a rich lithium/sodium layered material, or a rock salt phase layered material.
  • Li x A y Ni a Co b Mn c M (1-abc) Y z where 0 ⁇ x ⁇ 2.1, 0 ⁇ y ⁇ 2.1, and 0.9 ⁇ x+y ⁇ 2.1 ; 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, and 0.1 ⁇ a+b+c ⁇ 1; 1.8 ⁇ z ⁇ 3.5;
  • A is selected from one or more of Na, K and Mg Species;
  • M is selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te , Ba, Ta, W, Yb, La, Ce, one or more;
  • Y is selected from one or more of O, F.
  • the positive active material may be an olivine-type phosphate active material, the general formula of which is: Li x A y Me a M b P 1- c X c Y z , where 0 ⁇ x ⁇ 1.3, 0 ⁇ y ⁇ 1.3, and 0.9 ⁇ x+y ⁇ 1.3; 0.9 ⁇ a ⁇ 1.5, 0 ⁇ b ⁇ 0.5, and 0.9 ⁇ a+b ⁇ 1.5; 0 ⁇ c ⁇ 0.5; 3 ⁇ z ⁇ 5; A is selected from Na, K, Mg One or more; Me is selected from one or more of Mn, Fe, Co, and Ni; M is selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, One or more of Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X is selected from S, Si, Cl, One or more of B, C, N; Y is selected from one or more of O, F
  • the cathode active material may be a spinel structure cathode active material such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate and lithium nickel manganate, etc.
  • the general formula is: Li x A y Mn a M 2-a Y z , where 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, and 0.9 ⁇ x+y ⁇ 2; 0.5 ⁇ a ⁇ 2; 3 ⁇ z ⁇ 5; choose A One or more of Na, K, Mg; M is selected from Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr , Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y is selected from one or more of O and F.
  • the positive electrode film layer optionally further includes a positive electrode conductive agent.
  • a positive electrode conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon. One or a combination of nanofibers.
  • the mass percentage of the positive electrode conductive agent is less than 5% based on the total mass of the positive electrode film layer.
  • the positive electrode film layer optionally further includes a positive electrode binder.
  • the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene One or more combinations of terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the mass percentage of the cathode binder is less than 5% based on the total mass of the cathode film layer.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil or aluminum alloy foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver. and a combination of one or more silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate ( One or a combination of one or more of PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, lithium aluminum alloy, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a negative electrode binder.
  • the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • acrylic resin for example, polyacrylic acid.
  • PAA poly(methacrylate PMAA), poly(sodium acrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). combination of species.
  • the mass percentage of the negative electrode binder is less than 5% based on the total mass of the negative electrode film layer.
  • the negative electrode film layer optionally further includes a negative electrode conductive agent.
  • a negative electrode conductive agent can include selected from the group consisting of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and One or a combination of carbon nanofibers.
  • the mass percentage of the negative electrode conductive agent is less than 5%.
  • the negative electrode film layer optionally further includes other additives.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • CMC-Na sodium carboxymethylcellulose
  • PTC thermistor materials such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • the mass percentage of other additives is less than 2%.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil or copper alloy foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver. and a combination of one or more silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate ( One or a combination of one or more of PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer.
  • the negative electrode sheet further includes a protective layer covering the surface of the negative electrode film layer.
  • the secondary battery also includes an electrolyte, which conducts ions between the positive and negative electrodes.
  • an electrolyte which conducts ions between the positive and negative electrodes.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, and Through processes such as formation and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application provides an electrical device.
  • the electrical device includes at least one of a secondary battery, a battery module and a battery pack of the present application.
  • Secondary batteries, battery modules and battery packs can be used as power sources for power-consuming devices, and can also be used as energy storage units for power-consuming devices.
  • Electric devices can be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf balls). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device can select secondary batteries, battery modules or battery packs according to its usage requirements.
  • FIG. 6 is a schematic diagram of an electrical device as an example.
  • the electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack 1 or a battery module can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • a solvent and a coating material containing organic phosphoric acid or a salt thereof mix the solvent and the coating material into a coating slurry; mix the coating slurry and core particles LiMn 2 O 4 , and perform a filter press process at 100 Dry at °C to form a coating layer on the surface of the core particles, and prepare a lithium manganate composite material.
  • An aluminum foil with a thickness of 13 ⁇ m was used as the positive electrode current collector.
  • a copper foil with a thickness of 8 ⁇ m was used as the negative electrode current collector.
  • a porous polyethylene (PE) film is used as the isolation membrane.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the above-mentioned positive electrode piece, isolation film and negative electrode piece in order so that the isolation film is between the positive electrode piece and the negative electrode piece to play an isolation role, and then wind it to obtain the electrode assembly; place the electrode assembly in the outer packaging shell After drying, the electrolyte is injected, and through processes such as vacuum packaging, standing, formation, and shaping, a lithium-ion battery is obtained.
  • the secondary battery was prepared in a similar manner to Example 1, except that the type of “coating material” was adjusted.
  • the specific parameters are shown in Table 1 and Table 2.
  • the secondary battery was prepared in a similar manner to Example 1, except that the type of “coating material” was adjusted.
  • the specific parameters are shown in Table 1 and Table 2.
  • the secondary battery was prepared in a similar manner to Example 1, except that no coating material was provided.
  • the specific parameters are shown in Table 1 and Table 2; the preparation process of the positive electrode sheet is as follows:
  • An aluminum foil with a thickness of 13 ⁇ m was used as the positive electrode current collector.
  • the secondary battery was prepared in a similar manner to Example 1, except that the type of "solvent” was adjusted to make the thickness of the coating layer non-uniform. See Table 1 and Table 2 for specific parameters.
  • the secondary battery was prepared in a similar manner to Example 1, except that the content of the “coating material” was adjusted.
  • the specific parameters are shown in Table 1 and Table 2.
  • the secondary battery was prepared in a similar manner to Example 1, except that the type of "core particles” was adjusted.
  • the specific parameters are shown in Table 1 and Table 2.
  • the mass percentage content a1% of the core particles refers to the mass percentage content of the core particles relative to the total mass of the lithium manganate composite material composed of the coating material and the core particles;
  • the mass percentage content P% of the coating material refers to the mass percentage content of the coating material relative to the total mass of the lithium manganate composite material composed of the coating material and core particles;
  • the mass percentage a2% of the solvent refers to the mass percentage of the solvent relative to the total mass of the solvent system.
  • a transmission electron microscope is used to obtain a TEM image of the first region, and then the average thickness of multiple (for example, more than 30) different positions is measured on the TEM image, and the average value is taken as the average thickness H 1 of the second region.
  • SEM scanning electron microscope
  • the content of carbon element/metal/other non-metal elements is obtained by using Agilent ICP-OES730 to obtain the inductively coupled plasma emission spectrum (ICP), and then the ICP results are used to calculate the carbon element/metal/other non-metal element.
  • Agilent ICP-OES730 to obtain the inductively coupled plasma emission spectrum (ICP)
  • ICP results are used to calculate the carbon element/metal/other non-metal element.
  • Test using well-known instruments and methods in this field. For example, add the material and solvent to the Erlenmeyer flask at a ratio of 1:9, stir for 30 minutes using a magnetic stirrer, and let it stand for 1.5 hours after stirring. °C, humidity ⁇ 80% environment, use a magnetic acidity meter to test, take the average of three tests as the pH value of the material.
  • Example 1 150 836 Example 2-1 135 830
  • Example 2-2 130 Example 2-3 120 776 Comparative example 1 105 513 Comparative example 2 90 500
  • Example 3-1 150 820 Example 3-2 135 815
  • Example 3-3 150 828 Example 4-1 144 819
  • Example 4-2 134 825
  • Example 4-3 142 801
  • Example 4-4 131 810
  • Example 5-1 135 818 Example 5-2 131 810
  • Comparative Example 1 uses inorganic phosphate to coat LiMn 2 O 4 , which can alleviate the dissolution of manganese ions to a certain extent, but the effect is relatively insignificant.
  • organic phosphoric acid or its salts are used to coat LiMn 2 O 4 , which can significantly reduce the dissolution of manganese ions, thereby stabilizing manganese on the core particles, reducing the risk of manganese dissolving into the electrolyte, thereby further improving Storage performance and cycle performance of secondary batteries.
  • the improvement effect is better.
  • the thickness of the coating material formed on the surface of the core particles can be adjusted by adjusting the type of solvent, and the thickness is non-uniform, which is beneficial to improving the dynamic performance of the secondary battery.
  • the coating effect on the core particles can be adjusted by adjusting the mass percentage content P of the coating layer.
  • the electrochemical performance of the positive electrode sheet can be adjusted by adjusting the type of core particles.

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Abstract

本申请提供了一种一种锰酸锂复合材料及其制备方法、二次电池和用电装置。所述锰酸锂复合材料包括核颗粒和包覆层；核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr、Mo、Nb和Sn中的一种或多种，A包括F、Cl和S中的一种或多种；包覆层包覆于核颗粒的至少部分外表面，包覆层包括有机磷酸或其盐类。本申请能够保证核颗粒的结构稳定性，并保证负极活性材料的循环稳定性，由此可以进一步改善二次电池的容量性能和存储性能以及循环性能。

Description

锰酸锂复合材料及其制备方法、二次电池和用电装置 技术领域
本申请涉及电池领域，具体涉及一种锰酸锂复合材料及其制备方法、二次电池和用电装置。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。
随着电池应用范围越来越广泛，对二次电池性能的要求也逐渐严苛。为了提高二次电池的性能，通常对二次电池内的材料例如正极活性材料进行优化改善。
然而，目前改进后的正极活性材料在应用于二次电池时，二次电池在使用过程中仍无法同时兼顾改善循环性能和存储性能。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种锰酸锂复合材料及其制备方法、二次电池和用电装置。
本申请的第一方面提供了一种用于二次电池的锰酸锂复合材料，所述锰酸锂复合材料包括核颗粒和包覆层；核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr、Mo、Nb和Sn中的一种或多种，A包括F、Cl和S中的一种或多种；包覆层包覆于核颗粒的至少部分外表面，包覆层包括有机磷酸或其盐类。
由此，本申请的包含有机磷酸或其盐类的包覆层设置于核颗粒的外表面，能够将核颗粒的至少部分和电解液隔绝，从而降低电解液和核颗粒接触发生副反应的风险，由此降低电解液腐蚀核颗粒造成核颗粒破坏的风险，从而能够对核颗粒起到良好的防护作用，保证核颗粒的结构稳定性。有机磷酸或其盐类容易和电解液中的氢氟酸HF发生反应，降低氢氟酸HF对核颗粒的腐蚀作用，从而降低核颗粒中的过渡金属例如锰的溶出，电解液中的锰向负极活性材料迁移的含量显著减少，负极活性材料表面的SEI膜不易被破坏，SEI膜能够对负极活性材料起到良好的防护作用，保证负极活性材料的循环稳定性，由此可以进一步改善二次电池的容量性能和存储性能以及循环性能。
在任意实施方式中，有机磷酸或其盐类包括膦酸基团，膦酸基团的数量记为n， 2≤n≤4；可选地，2≤n≤3。
由此，本申请的有机磷酸或其盐类包含上述数量的磷酸基团时，能够进一步提高稳定锰元素的能力；并且有机磷酸或其盐类的酸度不会过高，不会对核颗粒造成破坏。
在任意实施方式中，有机磷酸或其盐类包括氨基三亚甲基膦酸、乙二胺四甲叉膦酸、羟基亚乙基二膦酸、氨基亚乙基二膦酸、甲胺二亚甲基膦酸、己二胺四亚甲基膦酸、羟基丙叉二膦酸、氨基丙基膦酸、己二胺四亚甲基膦酸钾盐、羟基亚乙基二膦酸钠盐、羟基亚乙基二膦酸钾盐、亚硝基三亚甲基膦酸和亚氨基二甲叉膦酸中的一种或多种。
在任意实施方式中，包覆层以连续的层状形态包覆在核颗粒的外表面。包覆层能够对核颗粒进行充分的防护，将核颗粒与电解液隔绝，降低电解液腐蚀核颗粒的风险，从而保证核颗粒的循环稳定性。
在任意实施方式中，包覆层包括彼此连接的第一区域部分和第二区域部分；第一区域部分的平均厚度记为H 1nm，第二区域部分的平均厚度记为H 2nm，锰酸锂复合材料满足：1＜H 1/H 2≤3。
由此，本申请的第一区域部分和第二区域部分的平均厚度不同，体现在第一区域部分的平均厚度大于第二区域部分的平均厚度；包覆层的不同区域的平均厚度不同，可以在保证对核颗粒的防护的基础上，可以降低包覆层的阻抗，从而能够改善二次电池的动力学性能；并且包覆层的该种结构还能够降低核颗粒与电解液中的氢氟酸HF反应的风险，进一步改善二次电池的动力学性能。
在任意实施方式中，包覆层的包覆率记为S％，包覆率为包覆层的总面积占据核颗粒的外表面积的百分比；锰酸锂复合材料满足：50≤S≤95；可选地，50≤S≤80。
由此，包覆层的包覆率S％在上述范围时，包覆层可以覆盖核颗粒的大部分外表面，从而能够对核颗粒起到充分的防护作用；并且包覆层的阻抗相对较小，在二次电池充放电过程中，锂离子由核颗粒向负极活性材料迁移的过程的阻抗较小，锂离子由负极活性材料向核颗粒迁移的过程的阻抗较小，从而能够改善二次电池的动力学性能。
在任意实施方式中，基于锰酸锂复合材料的总质量计，包覆层的质量百分含量记为P％，锰酸锂复合材料满足：0.01≤P≤5；可选地，0.1≤P≤2。
由此，本申请的锰酸锂复合材料满足上述范围时，包覆层能够对核颗粒起到充分的防护作用，并且能够保证锂离子等的顺利迁移，从而能够保证二次电池的动力学性能。
在任意实施方式中，核颗粒满足：-0.1≤x≤1.5，0.001≤y≤0.06，0.001≤Z≤0.05；和/或M包括Mg、Al和Sn中的一种或多种，A包括F和/或S。上述分子式的核颗粒和包覆层相互配合，包覆层能够充分防护核颗粒，并且核颗粒能够为二次电池提供较高的比容量，以改善二次电池的容量发挥。
在任意实施方式中，锰酸锂复合材料的pH值满足：6≤pH≤8；可选地，6.5≤ pH≤7.5。
锰酸锂复合材料的pH值在上述范围时，一方面pH值不会过高，能够降低在锰酸锂复合材料表面形成凝胶的风险，由此保证锂离子的顺利迁移，从而改善二次电池的动力学性能；另一方面pH值不会过低，能够降低对核颗粒的破坏，保证核颗粒的循环稳定性，从而改善二次电池的循环稳定性。
在任意实施方式中，锰酸锂复合材料的比表面积记为BET g/cm 3，BET≤1。
由此，本申请的锰酸锂复合材料的比表面积满足上述范围时，锰酸锂复合材料与电解液的接触面积相对较小，能够减小锰酸锂复合材料与电解液的接触界面，从而降低二者在界面发生副反应的风险，核颗粒中的锰不易溶出，能够保证锰酸锂复合材料整体的结构稳定性，从而改善二次电池的动力学性能和循环性能。
本申请的第二方面还提供了一种制备锰酸锂复合材料的方法，方法包括：S100，提供溶剂和包含有机磷酸或其盐类的包覆材料，将溶剂和包覆材料混合为包覆浆料；S200，将包覆浆料供应至核颗粒，以使包覆浆料在核颗粒的至少部分外表面固化形成包覆层，制备得到锰酸锂复合材料，其中，核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr和Sn中的一种或多种，A包括F、Cl和S中的一种或多种。
由此，本申请的制备方法制备工艺简单，且制备得到的包覆层能够对核颗粒进行充分防护，并能够减少核颗粒中的过渡金属的溶出，从而使得制备得到的锰酸锂复合材料应用于二次电池时，能够改善二次电池的容量性能、循环性能和存储性能。
在任意实施方式中，溶剂包括水、乙醇和甲醇中的一种或多种。
由此，本申请可以通过对溶剂的选取，调控所形成的包覆层的形貌，包覆层的形貌可以包括包覆层的厚度，例如在包覆层的不同区域形成不同厚度的膜层。
在任意实施方式中，溶剂和包覆材料的质量比记为Q，0＜Q≤0.1；和/或溶剂和核颗粒的质量比记为N，0＜N≤0.7。溶剂和包覆材料的质量比Q满足上述范围时，溶剂能够充分溶解包覆材料，更有利于包覆材料包覆于核颗粒的表面。溶剂和核颗粒的质量比N满足上述范围时，溶剂的使用量能够充分溶解包覆材料，将包覆材料包覆于核颗粒表面，且溶剂挥发过程中有利于在核颗粒的表面形成厚度不均一的包覆层，有利于进一步改善二次电池的动力学性能。
在任意实施方式中，固化的温度为80℃～120℃。
由此，本申请固化温度较低，在挥发溶剂的同时，不会对包覆层和核颗粒造成破坏，从而能够保证锰酸锂复合材料整体结构的稳定性，由此保证锰酸锂复合材料应用于二次电池时的循环稳定性。
本申请的第三方面还提供了一种二次电池，二次电池包括正极极片，正极极片包括如本申请第一方面任一实施方式的锰酸锂复合材料或第二方面任一实施方式的方法得到的锰酸锂复合材料。
本申请第四方面还提供了一种用电装置，包括如本申请第三方面实施方式的二次电池。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
附图未必按照实际的比例绘制。
附图标记说明如下：
1、电池包；2、上箱体；3、下箱体；4、电池模块；
5、二次电池；51、壳体；52、电极组件；
53、盖板；
6、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的正极活性材料、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合 形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
正极活性材料作为嵌锂化合物和提供活性锂离子的一方，其材料结构的稳定性对锂离子电池的整体性能有直接影响。电解液中存在的微量水分容易和电解液中的锂盐如LiPF 6反应生成氢氟酸HF，HF的存在使得正极活性材料易于发生副反应，导致正极活性材料中的过渡金属溶出至电解液中，过渡金属的溶出一方面会造成正极活性材料的破坏，另一方面当过渡金属迁移至负极活性材料处时，可能会对负极活性材料表面的固体电解质界面膜(Solid Electrolyte Interface，SEI膜)造成破坏，从而使得负极活性材料的结构存在被破坏的风险，恶化二次电池的容量性能、存储性能和循环性能。以正极活性材料为锰酸锂为例进行说明，电解液中的HF导致锰酸锂发生歧化反应生成Mn 2+，一方面歧化反应导致锰酸锂的晶格发生变化，另一方面Mn 2+在负极活性材料表面被还原成金属Mn，催化分解SEI膜破坏负极活性材料的界面，并且Mn还可能堵塞负极活性材料的嵌锂通道，甚至Mn还可能沉积于负极集流体和负极活性材料的界面上，而造成各层之间剥离；上述各种因素都可能导致二次电池的容量衰减，且二次电池的存储性能和循环性能变差。
鉴于上述问题，发明人考虑从防护正极活性材料例如锰酸锂材料的角度出发，保证正极活性材料的结构稳定性，发明人在正极活性材料例如锰酸锂材料的表面设置了包覆层，该包覆层包含有有机磷酸或其盐类，从而对正极活性材料进行良好的防护，且有利于形成良好的正极固态电解质界面膜(Cathode Electrolyte Interface，CEI膜)，能够对正极活性材料起到进一步的防护作用，从而改善二次电池的容量性能、存储性能和循环性能。接下来对正极活性材料的技术方案进行详细说明。
锰酸锂复合材料
第一方面，本申请提出了一种锰酸锂复合材料，所述锰酸锂复合材料包括核颗粒和包覆层，核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤ 0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr、Mo、Nb和Sn中的一种或多种，A包括F、Cl和S中的一种或多种；包覆层包覆于所述核颗粒的至少部分外表面，包覆层包括有机磷酸或其盐类。
有机磷酸是指分子中有两个以上的膦酸基团中的磷原子直接与碳原子相连的化合物。有机磷酸盐类是指有机磷酸的膦酸基团中的氢原子被金属阳离子所取代的化合物。
虽然机理不甚明确，但是本申请的锰酸锂复合材料在应用于二次电池时，可以改善二次电池的容量性能、存储性能和循环性能；发明人推测原因可能如下：
包含有机磷酸或其盐类的包覆层设置于核颗粒的外表面，能够将核颗粒的至少部分和电解液隔绝，从而降低电解液和核颗粒接触发生副反应的风险，由此降低电解液腐蚀核颗粒造成核颗粒破坏的风险，从而能够对核颗粒起到良好的防护作用，保证核颗粒的结构稳定性。发明人推测，包含有机磷酸或其盐类的包覆层还可能具有促进锰酸锂复合材料表面形成CEI膜的作用，CEI膜能够对锰酸锂复合材料整体起到进一步的防护作用，在二次电池充放电过程中，CEI膜始终保持致密且稳定的状态，从而能够对锰酸锂复合材料起到持续的防护作用，从而进一步保证锰酸锂复合材料的结构稳定性，在锰酸锂复合材料应用于二次电池时，可以提高二次电池的容量性能、存储性能和循环性能。
有机磷酸或其盐类容易和电解液中的氢氟酸HF发生反应，降低氢氟酸HF对核颗粒的腐蚀作用，从而降低核颗粒中的过渡金属例如锰的溶出，电解液中的锰向负极活性材料迁移的含量显著减少，负极活性材料表面的SEI膜不易被破坏，SEI膜能够对负极活性材料起到良好的防护作用，保证负极活性材料的循环稳定性，由此可以进一步改善二次电池的容量性能和存储性能以及循环性能。
有机磷酸或其盐类可能会与过渡金属例如锰发生络合反应，从而将锰稳定在核颗粒上，降低锰溶出至电解液的风险，由此进一步改善二次电池的容量性能和存储性能以及循环性能。
在一些实施方式中，有机磷酸或其盐类包括膦酸基团，膦酸基团的数量记为n，2≤n≤4。
发明人推测，有机磷酸或其盐类包含上述数量的磷酸基团时，能够进一步提高稳定锰元素的能力；并且有机磷酸或其盐类的酸度不会过高，不会对核颗粒造成破坏。可选地，2≤n≤3；示例性地，n可以为2、3或4。
作为示例，有机磷酸或其盐类可以包括氨基三亚甲基膦酸、乙二胺四甲叉膦酸、羟基亚乙基二膦酸、氨基亚乙基二膦酸、甲胺二亚甲基膦酸、己二胺四亚甲基膦酸、羟基丙叉二膦酸、氨基丙基膦酸、己二胺四亚甲基膦酸钾盐、羟基亚乙基二膦酸钠盐、羟基亚乙基二膦酸钾盐、亚硝基三亚甲基膦酸和亚氨基二甲叉膦酸中的一种或多种。
上述有机磷酸或其盐类能够对核颗粒起到良好的防护作用，从而能够保证锰酸锂复合材料的循环稳定性。
包覆层包覆核颗粒具有多种结构形式，在一些实施方式中，包覆层以连续的层 状形态包覆在核颗粒的外表面。包覆层能够对核颗粒进行充分的防护，将核颗粒与电解液隔绝，降低电解液腐蚀核颗粒的风险，从而保证核颗粒的循环稳定性。在另一些实施方式中，包覆层也可以以离散分布的层状形态包覆在核颗粒的外表面，包覆层中的有机磷酸或其盐类能够稳定核颗粒中的锰，降低锰溶出至电解液中，从而保证核颗粒的循环稳定性。
在一些实施方式中，包覆层包括彼此连接的第一区域部分和第二区域部分，第一区域部分的平均厚度记为H 1nm，第二区域部分的平均厚度记为H 2nm，锰酸锂复合材料满足1＜H 1/H 2≤3。
第一区域部分和第二区域部分的平均厚度不同，体现在第一区域部分的平均厚度大于第二区域部分的平均厚度；包覆层的不同区域的平均厚度不同，可以在保证对核颗粒的防护的基础上，可以降低包覆层的阻抗，从而能够改善二次电池的动力学性能；并且包覆层的该种结构还能够降低核颗粒与电解液中的氢氟酸HF反应的风险，进一步改善二次电池的动力学性能。可选地，1.5≤H 1/H 2≤2.5；示例性地，H 1/H 2可以为1、1.1、1.5、1.6、1.8、2、2.5、2.8或3；或者是上述任意两个数值组成的范围。
第一区域部分和第二区域部分均为包覆层的组成部分，但是第一区域部分和第二区域部分之间没有明显的界限，二者构成连续的结构，在制备包覆层的过程中可以通过调节工艺参数例如溶剂的种类或浓度调节第一区域部分和第二区域部分的平均厚度。
在一些实施方式中，5≤H 1≤45。
在本申请中，第一区域部分的平均厚度可以采用本领域公知的测试方法和测试仪器进行，具体如下：可以采用透射电子显微镜得到第一区域部分的透射电子显微镜(Transmission Electron Microscope，TEM)图片，然后在TEM图片上量取多个(例如30个以上)不同位置的平均厚度，并取其平均值作为第一区域部分的平均厚度H 1。
在一些实施方式中，5＜H 2≤15。
在本申请中，第二区域部分的平均厚度可以采用本领域公知的测试方法和测试仪器进行，具体如下：可以采用透射电子显微镜得到第二区域部分的TEM图片，然后在TEM图片上量取多个(例如30个以上)不同位置的平均厚度，并取其平均值作为第二区域部分的平均厚度H 2。
在一些实施方式中，包覆层的包覆率记为S％；锰酸锂复合材料满足：50≤S≤95。
包覆层的包覆率S％在上述范围时，包覆层可以覆盖核颗粒的大部分外表面，从而能够对核颗粒起到充分的防护作用；并且包覆层的阻抗相对较小，在二次电池充放电过程中，锂离子由核颗粒向负极活性材料迁移的过程的阻抗较小，锂离子由负极活性材料向核颗粒迁移的过程的阻抗较小，从而能够改善二次电池的动力学性能。可选地，50≤S≤80；示例性地，包覆层的包覆率S％可以为50％、55％、60％、65％、70％、75％、80％、85％、90％或95％；或者是上述任意两个数值组成的范围。
在本申请中，包覆率是指包覆层的总面积占据核颗粒的外表面积的百分比；其 可以采用本领域公知的测试方法和测试仪器进行检测，例如可以采用扫描电子显微镜(scanning electron microscope，SEM)观察锰酸锂复合材料和核颗粒的微观形貌，从而计算包覆率。
在一些实施方式中，基于锰酸锂复合材料的总质量计，包覆层的质量百分含量记为P％，锰酸锂复合材料满足：0.01≤P≤5。
锰酸锂复合材料满足上述范围时，包覆层能够对核颗粒起到充分的防护作用，并且能够保证锂离子等的顺利迁移，从而能够保证二次电池的动力学性能。可选地，0.1≤P≤2。示例性地，包覆层的质量百分含量P％可以为0.01％、0.02％、0.05％、0.08％、0.10％、0.15％、0.20％、0.25％、0.30％、0.50％、0.80％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％或5％；或者是上述任意两个数值范围组成的范围。
在一些实施方式中，核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，-0.1≤x≤1.5，0.001≤y≤0.06，0.001≤Z≤0.05；和/或M包括Mg、Al和Sn中的一种或多种，A包括F和/或S。
上述分子式的核颗粒和包覆层相互配合，包覆层能够充分防护核颗粒，并且核颗粒能够为二次电池提供较高的比容量，以改善二次电池的容量发挥。
在一些实施方式中，锰酸锂复合材料的pH值满足：6≤pH≤8。
锰酸锂复合材料的pH值在上述范围时，一方面pH值不会过高，能够降低在锰酸锂复合材料表面形成凝胶的风险，由此保证锂离子的顺利迁移，从而改善二次电池的动力学性能；另一方面pH值不会过低，能够降低对核颗粒的破坏，保证核颗粒的循环稳定性，从而改善二次电池的循环稳定性。可选地，6.5≤pH≤7.5。示例性地，锰酸锂复合材料的pH值可以为6、6.5、7、7.5或8；或者在上述任意两个数值组成的范围内。
在本申请中，材料的pH值为本领域公知的含义，可以采用本领域公知的仪器及方法进行测试，例如将材料和溶剂按照1：9的的比例加入加入至锥形瓶中，利用磁力搅拌器搅拌30min，搅拌结束后静置1.5h，在15-28℃，湿度≤80％的环境下，利用雷磁酸度计进行测试，取3次测试的平均值作为材料的pH值。
在一些实施方式中，锰酸锂复合材料的比表面积记为BET g/cm 3，BET≤1。
锰酸锂复合材料的比表面积满足上述范围时，锰酸锂复合材料与电解液的接触面积相对较小，能够减小锰酸锂复合材料与电解液的接触界面，从而降低二者在界面发生副反应的风险，核颗粒中的锰不易溶出，能够保证锰酸锂复合材料整体的结构稳定性，从而改善二次电池的动力学性能和循环性能。示例性地，BET可以为1g/cm 3、0.8g/cm 3、0.6g/cm 3、0.5g/cm 3、0.4g/cm 3、0.2g/cm 3或0.1g/cm 3；或者是上述任意两个数值组成的范围。
在本申请中，材料的比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测试。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(BrunauerEmmett Teller)法计算得出，氮气吸附比表面积分析测试 可以通过美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪进行。
需要说明的是，锰酸锂复合材料可以作为正极活性材料应用于二次电池，上述针对锰酸锂复合材料的各种参数测试，可以在涂布前取样测试，也可以从冷压后的正极膜层中取样测试。当锰酸锂复合材料测试样品是从经冷压后的正极膜层中取样时，作为示例，可以按如下步骤进行取样：任意选取一冷压后的正极膜层，对锰酸锂复合材料取样(例如可以选用刀片刮粉取样)；将上述收集到的锰酸锂复合材料粉末置于去离子水中，之后进行抽滤、烘干，再将烘干后的锰酸锂复合材料在一定温度及时间下烧结(例如400℃，2h)，去除粘结剂和导电剂，即得到锰酸锂复合材料的测试样品。
制备锰酸锂复合材料的方法
第二方面，本申请提出了一种制备锰酸锂复合材料的方法。方法包括：
S100，提供溶剂和包含有机磷酸或其盐类的包覆材料，将溶剂和包覆材料混合为包覆浆料；
S200，将包覆浆料供应至核颗粒，以使包覆浆料在核颗粒的至少部分外表面固化形成包覆层，制备得到锰酸锂复合材料，
其中，核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr和Sn中的一种或多种，A包括F、Cl和S中的一种或多种。
本申请的制备方法制备工艺简单，且制备得到的包覆层能够对核颗粒进行充分防护，并能够减少核颗粒中的过渡金属的溶出，从而使得制备得到的锰酸锂复合材料应用于二次电池时，能够改善二次电池的容量性能、循环性能和存储性能。
本申请的制备方法可以用于制备本申请第一方面任一实施方式的锰酸锂复合材料
在一些实施方式中，溶剂包括水、乙醇和甲醇中的一种或多种。
可以通过对溶剂的选取，调控所形成的包覆层的形貌，包覆层的形貌可以包括包覆层的厚度，例如在包覆层的不同区域形成不同厚度的膜层。以采用水为溶剂举例说明，将包覆材料溶于水中混合，然后采用抽滤、压滤或离心等的方式干燥，从而能够得到不同区域厚度不同的包覆层，例如包覆层包括第一区域部分和第二区域部分，第一区域部分的厚度大于第二区域部分的厚度。发明人猜测能够在包覆层中形成不同厚度的区域的原因如下：包覆材料在水中所具有的溶剂化结构，或者说包覆材料在水中的溶解状态，使得溶剂在挥发过程中包覆材料在核颗粒表面上的聚集状态可能会不同，从而使得核颗粒表面的不同区域包覆有不同厚度的包覆层。并且本申请采用抽滤、压力或离心等的方式干燥溶剂，使得核颗粒表面的残余溶剂的含量较少，由此导致在溶剂挥发的过程中，包覆材料在核颗粒表面可能不及时迁移，即包覆材料在核颗粒的表面分布不均匀，从而使得核颗粒表面的部分区域的包覆层较厚，部分区域的包覆层较薄，有利于改善二次电池的动力学性能。
当然，本申请干燥溶剂过程也可以采用直接热处理的形式挥发溶剂；例如将包覆浆料置于湿包机中，在惰性非氧化气体氛围下，并在80～100℃下搅拌溶剂和包覆材 料，使得包覆材料溶解于溶剂且包覆于核颗粒的同时，可以挥发溶剂，从而在核颗粒的表面形成包覆层。
在一些实施方式中，溶剂和包覆材料的质量比记为Q，0＜Q≤0.1。
溶剂和包覆材料的质量比Q满足上述范围时，溶剂能够充分溶解包覆材料，更有利于包覆材料包覆于核颗粒的表面。示例性地，溶剂和包覆材料的质量比Q可以为0.01、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.09或0.1；或者是上述任意两个数值组成的范围。在本申请中，可以基于溶剂、包覆材料和核颗粒所组成的整体体系的总质量计，溶剂的质量百分含量与包覆材料的质量百分含量的比值为Q。
溶剂和包覆材料的质量比，可以认为是基于包覆材料的总质量计，溶剂的质量百分含量与包覆材料的质量百分含量的比值。
在一些实施方式中，溶剂和核颗粒的质量比记为N，0＜N≤0.7。
溶剂和核颗粒的质量比N满足上述范围时，溶剂的使用量能够充分溶解包覆材料，将包覆材料包覆于核颗粒表面，且溶剂挥发过程中有利于在核颗粒的表面形成厚度不均一的包覆层，有利于进一步改善二次电池的动力学性能。示例性地，溶剂和核颗粒的质量比N可以为0.01、0.02、0.03、0.04、0.05、0.06或0.07；或者是上述任意两个数值组成的范围。在本申请中，可以基于溶剂、包覆材料和核颗粒所组成的整体体系的总质量计，溶剂的质量百分含量与核颗粒的质量百分含量的比值为N。
在一些实施方式中，固化的温度为80℃～120℃。
本申请固化温度较低，在挥发溶剂的同时，不会对包覆层和核颗粒造成破坏，从而能够保证锰酸锂复合材料整体结构的稳定性，由此保证锰酸锂复合材料应用于二次电池时的循环稳定性。示例性地，固化的温度可以为80℃、85℃、90℃、95℃、100℃、105℃、110℃、115℃或120℃；或者是上述任意两个数值组成的范围。
二次电池
第三方面，本申请提出了一种二次电池。
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。二次电池包括正极极片、负极极片和隔离膜。隔离膜设置在正极极片和负极极片之间，主要起到防止正极和负极短路的作用，同时可以使金属离子通过。电解液在正极极片和负极极片之间起到传导金属离子的作用。本申请的二次电池可为锂二次电池、钠离子电池等，特别地，可为锂离子二次电池。
[正极极片]
在一些实施方式中，正极极片包括正极集流体以及设置在正极集流体至少一个表面上的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
在一些实施方式中，正极膜层包括正极活性材料，正极活性材料采用本申请第一方面任一实施方式的锰酸锂复合材料或本申请第二方面任一实施方式的方法制备得到的锰酸锂复合材料。正极活性材料能够显著改善二次电池的性能。
在一些实施方式中，正极活性材料还可以采用本领域公知的用于二次电池的正 极活性材料。例如，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的至少一种。锂过渡金属氧化物的示例可包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的至少一种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
具体地，正极活性材料可以为层状材料，例如三元材料、镍酸锂/钠材料、钴酸锂/钠材料、锰酸锂/钠材料、富锂/钠层状材料、岩盐相层状材料；上述材料的通式为：Li xA yNi aCo bMn cM (1-a-b-c)Y z，其中，0≤x≤2.1，0≤y≤2.1，且0.9≤x+y≤2.1；0≤a≤1，0≤b≤1，0≤c≤1，且0.1≤a+b+c≤1；1.8≤z≤3.5；A选自Na、K、Mg中的一种或几种；M选自B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Fe、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；Y选自O、F中的一种或几种。
正极活性材料可以为橄榄石型磷酸盐活性材料，其通式为：Li xA yMe aM bP 1- cX cY z，其中，0≤x≤1.3，0≤y≤1.3，且0.9≤x+y≤1.3；0.9≤a≤1.5，0≤b≤0.5，且0.9≤a+b≤1.5；0≤c≤0.5；3≤z≤5；A选自Na、K、Mg中的一种或几种；Me选自Mn、Fe、Co、Ni中的一种或几种；M选自B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；X选自S、Si、Cl、B、C、N中的一种或几种；Y选自O、F中的一种或几种。
正极活性材料可以为尖晶石结构的正极活性材料例如尖晶石锰酸锂、尖晶石镍锰酸锂、富锂的尖晶石锰酸锂和镍锰酸锂等，其通式为：Li xA yMn aM 2-aY z，其中，0≤x≤2，0≤y≤1，且0.9≤x+y≤2；0.5≤a≤2；3≤z≤5；A选自Na、K、Mg中的一种或几种；M选自Ni、Co、B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Fe、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；Y选自O、F中的一种或几种。
在一些实施方式中中，正极膜层还可选地包括正极导电剂。本申请对正极导电剂的种类没有特别的限制，作为示例，正极导电剂包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种的组合。在一些实施方式中中，基于正极膜层的总质量，正极导电剂的质量百分含量在5％以下。
在一些实施方式中中，正极膜层还可选地包括正极粘结剂。本申请对正极粘结剂的种类没有特别的限制，作为示例，正极粘结剂可包括选自聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物和含氟丙烯酸酯类树脂中的一种或多种的组合。在一些实施方式中中，基于正极膜层的总质量，正极粘结剂的质量百分含量在5％ 以下。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔或铝合金箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层，作为示例，金属材料可包括选自铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种的组合，高分子材料基层可包括选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种的组合。
正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂和锂铝合金等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中中，负极膜层还可选地包括负极粘结剂。本申请对负极粘结剂的种类没有特别的限制，作为示例，负极粘结剂可包括选自丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或多种的组合。在一些实施方式中中，基于负极膜层的总质量，负极粘结剂的质量百分含量在5％以下。
在一些实施方式中中，负极膜层还可选地包括负极导电剂。本申请对负极导电剂的种类没有特别的限制，作为示例，负极导电剂可包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种的组合。在一些实施方式中中，基于负极膜层的总质量，负极导电剂的质量百分含量在5％以下。
在一些实施方式中中，负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC-Na)、PTC热敏电阻材料等。在一些实施方式中中，基于负极膜层的总质量，其他助剂的质量百分含量在2％以下。
在一些实施方式中中，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔或铜合金箔。复合集流体可包括高分子材料基层以及形成于高 分子材料基层至少一个表面上的金属材料层，作为示例，金属材料可包括选自铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种的组合，高分子材料基层可包括选自聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种的组合。
负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
负极极片并不排除除了负极膜层之外的其他附加功能层。例如在某些实施例中，负极极片还包括覆盖在负极膜层表面的保护层。
[电解质]
二次电池还包括电解质，电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组 件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图1和图2所示，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
第四方面，本申请提供一种用电装置，用电装置包括本申请的二次电池、电池模块和电池包中的至少一种。二次电池、电池模块和电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置的示意图。该用电装置6为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包1或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
1、正极极片的制备
1.1锰酸锂复合材料的制备
提供溶剂和包含有机磷酸或其盐类的包覆材料，将溶剂和包覆材料混合为包覆浆料；将包覆浆料和核颗粒LiMn 2O 4混合，并在压滤工序下于100℃下干燥，以使在核颗粒的表面形成包覆层，并制备得到锰酸锂复合材料。
1.2正极极片的制备
采用厚度为13μm的铝箔作为正极集流体。
将锰酸锂复合材料、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比97.5:1.4:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。
2、负极极片的制备
采用厚度为8μm的铜箔作为负极集流体。
将负极活性材料石墨、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)、导电剂炭黑(Super P)按重量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
3、隔离膜
采用多孔聚乙烯(PE)膜作为隔离膜。
4、电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的LiPF 6溶解于上述有机溶剂中，配制成浓度为1mol/L的电解液。
5、二次电池的制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离作用，然后卷绕得到电极组件；将电极组件置于外包装壳中，干 燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
实施例2
实施例2-1至实施例2-3
二次电池按照与实施例1类似的方法相似制备，不同之处在于调整了“包覆材料”的种类，具体参数详见表1和表2。
对比例
对比例1
二次电池按照与实施例1类似的方法相似制备，不同之处在于调整了“包覆材料”的种类，具体参数详见表1和表2。
对比例2
二次电池按照与实施例1类似的方法相似制备，不同之处在于未设置包覆材料，具体参数详见表1和表2；其正极极片的制备过程如下：
采用厚度为13μm的铝箔作为正极集流体。
将核颗粒、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比97.5:1.4:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。
实施例3
实施例3-1至实施例3-3
二次电池按照与实施例1类似的方法相似制备，不同之处在于调整了“溶剂”的种类，从而使得包覆层的厚度不均一，具体参数详见表1和表2。
实施例4
实施例4-1至实施例4-4
二次电池按照与实施例1类似的方法相似制备，不同之处在于调整了“包覆材料”的含量，具体参数详见表1和表2。
实施例5
实施例5-1和实施例5-2
二次电池按照与实施例1类似的方法相似制备，不同之处在于调整了“核颗粒”的种类，具体参数详见表1和表2。
表1
Figure PCTCN2022106039-appb-000001
Figure PCTCN2022106039-appb-000002
表1中，核颗粒的质量百分含量a1％是指核颗粒相对于包覆材料和核颗粒所组成的锰酸锂复合材料的总质量的质量百分含量；
包覆材料的质量百分含量P％是指包覆材料相对于包覆材料和核颗粒所组成的锰酸锂复合材料的总质量的质量百分含量；
溶剂的质量百分含量a2％是指溶剂相对于溶剂体系的总质量的质量百分含量。
表2
Figure PCTCN2022106039-appb-000003
Figure PCTCN2022106039-appb-000004
测试部分
1、锰酸锂复合材料的性能测试
1.1锰酸锂复合材料的平均厚度测试
采用透射电子显微镜得到第一区域部分的TEM图片，然后在TEM图片上量取多个(例如30个以上)不同位置的平均厚度，并取其平均值作为第二区域部分的平均厚度H 1。
采用透射电子显微镜得到第二区域部分的TEM图片，然后在TEM图片上量取多个(例如30个以上)不同位置的平均厚度，并取其平均值作为第一区域部分的平均厚度H 2。
1.2包覆层的包覆率S％的测试
采用扫描电子显微镜(scanning electron microscope，SEM)，德国卡尔蔡司公司EVO MA 25，观察锰酸锂复合材料和核颗粒的微观形貌，定性判断。
1.3锰酸锂复合材料的元素测试
碳元素/金属/其他非金属元素含量采用Agilent ICP-OES730得到电感耦合等离子体发射光谱(ICP)，然后ICP结果计算碳元素/金属/其他非金属元素。
取一定量上述制备的负极活性材料样品，加入到德国Bruker AXS D8-focus X射线衍射仪，获得样品的X射线衍射图谱，再与标准物质的X射线衍射图谱比对，可以定性获得样品的物相组成。测试标准参考JIS K0131-1996。
1.4锰酸锂复合材料的pH值测试
采用本领域公知的仪器及方法进行测试，例如将材料和溶剂按照1：9的的比例加入加入至锥形瓶中，利用磁力搅拌器搅拌30min，搅拌结束后静置1.5h，在15-28℃，湿度≤80％的环境下，利用雷磁酸度计进行测试，取3次测试的平均值作为材料的pH值。
1.5锰酸锂复合材料的比表面积测试
取一定量上述制备的负极活性材料样品，通过美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪测试比表面积。比表面积的计算方法为BET(BrunauerEmmett Teller)法。测试标准依据GB/T 19587-2017。
2、二次电池的性能测试
2.1二次电池于45℃下的存储性能测试
在常温条件下，将二次电池按照0.33C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5分钟，然后按照0.33C放电至3V，记录此时的容量M0；2.将全电池按照0.33C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，最后45℃恒温条件下进行存储；3.每隔15天重复上述过程，直至容量降低至M0的80％，记录此时的存储天数。
2.2二次电池于45℃下的循环性能测试
在45℃的恒温环境下，将二次电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5分钟，然后按照1C放电至3V，记录此时的放电容量为E0。重复前述充放电循环，直至放电容量降低到E0的80％。记录此时二次电池经过的循环圈数。
测试结果
本申请在改善二次电池的循环性能、存储性能和容量发挥的作用如表3所示。
表3
项目 存储性能/天 循环性能/圈
实施例1 150 836
实施例2-1 135 830
实施例2-2 130 826
实施例2-3 120 776
对比例1 105 513
对比例2 90 500
实施例3-1 150 820
实施例3-2 135 815
实施例3-3 150 828
实施例4-1 144 819
实施例4-2 134 825
实施例4-3 142 801
实施例4-4 131 810
实施例5-1 135 818
实施例5-2 131 810
由表3可知，对比例2未对LiMn 2O 4进行包覆，LiMn 2O 4进行容易发生锰离子的溶出，从而使得正极活性材料被破坏，且有可能造成负极活性材料表面的SEI膜的破坏，由此导致二次电池的循环性能和存储性能较差。对比例1采用了无机磷酸盐对LiMn 2O 4进行了包覆，可以在一定程度缓解锰离子的溶出，但是其效果相对不明显。本申请实施例采用有机磷酸或其盐类对LiMn 2O 4进行包覆，可以显著降低锰离子的溶出，从而将锰稳定在核颗粒上，降低锰溶出至电解液的风险，由此进一步改善二次电池的存储性能以及循环性能。尤其是有机磷酸或其盐类的膦酸基团的数量n满足2≤n≤4，特别满足2≤n≤3时，其改善的效果较佳。
实施例3-1至实施例3-3可以通过调节溶剂的种类，调控包覆材料在核颗粒表面形成的厚度，且厚度不均一，从而有利于改善二次电池的动力学性能。
实施例4-1至实施例4-4可以通过调节包覆层的质量百分含量P，调节对核颗粒的包覆效果。
实施例5-1至实施例5-2可以通过调节核颗粒的种类，调节正极极片的电化学 性能。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种锰酸锂复合材料，包括：
    核颗粒，其分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr、Mo、Nb和Sn中的一种或多种，A包括F、Cl和S中的一种或多种；以及
    包覆层，其包覆于所述核颗粒的至少部分外表面，所述包覆层包括有机磷酸或其盐类。
  2. 根据权利要求1所述的锰酸锂复合材料，其中，所述有机磷酸或其盐类包括膦酸基团，所述膦酸基团的数量记为n，2≤n≤4；可选地，2≤n≤3。
  3. 根据权利要求1或2所述的锰酸锂复合材料，其中，所述有机磷酸或其盐类包括氨基三亚甲基膦酸、乙二胺四甲叉膦酸、羟基亚乙基二膦酸、氨基亚乙基二膦酸、甲胺二亚甲基膦酸、己二胺四亚甲基膦酸、羟基丙叉二膦酸、氨基丙基膦酸、己二胺四亚甲基膦酸钾盐、羟基亚乙基二膦酸钠盐、羟基亚乙基二膦酸钾盐、亚硝基三亚甲基膦酸和亚氨基二甲叉膦酸中的一种或多种。
  4. 根据权利要求1至3中任一项所述的锰酸锂复合材料，其中，
    所述包覆层以连续的层状形态包覆在所述核颗粒的外表面。
  5. 根据权利要求1至4中任一项所述的锰酸锂复合材料，其中，
    所述包覆层包括彼此连接的第一区域部分和第二区域部分；
    所述第一区域部分的平均厚度记为H 1 nm，所述第二区域部分的平均厚度记为H 2 nm，
    所述锰酸锂复合材料满足：1＜H 1/H 2≤3。
  6. 根据权利要求1至5中任一项所述的锰酸锂复合材料，其中，
    所述包覆层的包覆率记为S％，所述包覆率为所述包覆层的总面积占据所述核颗粒的外表面积的百分比；
    所述锰酸锂复合材料满足：50≤S≤95；可选地，50≤S≤80。
  7. 根据权利要求1至6中任一项所述的锰酸锂复合材料，其中，
    基于所述锰酸锂复合材料的总质量计，所述包覆层的质量百分含量记为P％，
    所述锰酸锂复合材料满足：0.01≤P≤5；可选地，0.1≤P≤2。
  8. 根据权利要求1至7中任一项所述的锰酸锂复合材料，其中，所述核颗粒满足：
    -0.1≤x≤1.5，0.001≤y≤0.06，0.001≤Z≤0.05；和/或
    M包括Mg、Al和Sn中的一种或多种，A包括F和/或S。
  9. 根据权利要求1至8中任一项所述的锰酸锂复合材料，其中，所述锰酸锂复合材料的pH值满足：6≤pH≤8；可选地，6.5≤pH≤7.5。
  10. 根据权利要求1至9中任一项所述的锰酸锂复合材料，其中，所述锰酸锂复合材料的比表面积记为BET g/cm 3，BET≤1。
  11. 一种制备锰酸锂复合材料的方法，包括：
    S100，提供溶剂和包含有机磷酸或其盐类的包覆材料，将所述溶剂和所述包覆材料混合为包覆浆料；
    S200，将所述包覆浆料供应至核颗粒，以使所述包覆浆料在所述核颗粒的至少部分外表面固化形成包覆层，制备得到锰酸锂复合材料，
    其中，所述核颗粒的分子式为Li 1+xMn 2-yM yO 4-ZA z，分子式中，-0.2≤x≤0.2，0≤y≤0.1，0≤Z≤0.1，M包括Mg、Al、Ge、Fe、Zn、Co、Ni、Cr和Sn中的一种或多种，A包括F、Cl和S中的一种或多种。
  12. 根据权利要求11所述的方法，其中，所述溶剂包括水、乙醇和甲醇中的一种或多种。
  13. 根据权利要求11或12所述的方法，其中，
    所述溶剂和所述包覆材料的质量比记为Q，0＜Q≤0.1；和/或
    所述溶剂和所述核颗粒的质量比记为N，0＜N≤0.7。
  14. 根据权利要求11中13中任一项所述的方法，其中，所述固化的温度为80℃～120℃。
  15. 一种二次电池，包括：正极极片，所述正极极片包括如权利要求1至10中任一项所述的锰酸锂复合材料或如权利要求11至14中任一项所述方法制备得到的锰酸锂复合材料。
  16. 一种用电装置，包括如权利要求15所述的二次电池。
PCT/CN2022/106039 2022-07-15 2022-07-15 锰酸锂复合材料及其制备方法、二次电池和用电装置 WO2024011602A1 (zh)

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