WO2023050833A1 - Matériau d'électrode positive et son procédé de préparation, batterie secondaire, module de batterie, bloc-batterie et dispositif électrique - Google Patents

Matériau d'électrode positive et son procédé de préparation, batterie secondaire, module de batterie, bloc-batterie et dispositif électrique Download PDF

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WO2023050833A1
WO2023050833A1 PCT/CN2022/094202 CN2022094202W WO2023050833A1 WO 2023050833 A1 WO2023050833 A1 WO 2023050833A1 CN 2022094202 W CN2022094202 W CN 2022094202W WO 2023050833 A1 WO2023050833 A1 WO 2023050833A1
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positive electrode
electrode material
inner core
polymer
mass percentage
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PCT/CN2022/094202
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Chinese (zh)
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马晴岩
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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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • 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
    • 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 technical field of lithium batteries, in particular to a positive electrode material and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries have been widely used in energy storage power systems such as water power, fire power, wind power, and solar power stations, as well as in power tools, vehicles, military equipment, aerospace, etc. field.
  • Lithium-ion batteries provide great opportunities for the development of clean energy, but at the same time they also face enormous technical challenges.
  • people have higher and higher requirements for the energy density and stable performance of lithium-ion batteries.
  • Lithium manganate material is a type of manganese-based lithium metal oxide with a spinel structure. Because it is suitable for high-voltage systems and has a higher capacity, it has become a key development direction for lithium-ion battery cathode materials. However, a large number of experiments have found that when lithium manganese oxide is used as the positive electrode material in lithium-ion batteries, although the energy density of the battery can be improved, its storage performance and cycle performance are poor.
  • the present application is carried out in view of the above-mentioned problems, and its purpose is to provide a positive electrode material and a manufacturing method thereof, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device, by performing a lithium manganate positive electrode material Double-layer coating to alleviate the Mn dissolution problem in the lithium manganese oxide battery system, so that the secondary battery containing the material has good storage performance and cycle performance.
  • the present application provides a positive electrode material and a manufacturing method thereof, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device.
  • the first aspect of the present application provides a kind of cathode material, it comprises:
  • the inner core includes a compound of formula I having a spinel structure:
  • M is selected from Al, Mg, Ga, Ti, Fe, Nb, Zn, Go , one or more of Ni, Sn, Cr, A is selected from one or more of F, S, Cl;
  • the first coating layer includes a first polymer containing electron-withdrawing groups, and the electron-withdrawing groups are selected from at least one of ester groups or nitrile groups; the second coating layer contains polysaccharides.
  • the present application arranges the first cladding layer containing the first polymer on the surface of the lithium manganese oxide core with a spinel structure, because the electron-withdrawing group in the first polymer transfers the electrons of Mn 3+ to the electron-withdrawing group
  • the deviation increases the average valence of manganese, which can effectively stabilize the Mn 3+ on the surface of lithium manganese oxide, and at the same time ensure that the inner lithium manganate material has good electronic conductivity.
  • a second coating layer containing polysaccharides is further provided to combine with Lewis acids such as phosphorus pentafluoride (PF5) by utilizing the characteristics of the surface of polysaccharides rich in oxygen elements.
  • HF hydrofluoric acid
  • the -CO ether bond in polysaccharides can chelate with the manganese ions dissolved from the inner core, it helps to further inhibit the lithium manganate inner core.
  • Dissolution of manganese ions in the medium by setting the above-mentioned double-layer coating structure on the core of lithium manganate, while realizing the physical isolation between the electrolyte and the core of lithium manganate, the generation of HF in the electrolyte is greatly reduced, and the lithium manganate core is effectively suppressed.
  • the dissolution of Mn ions in the medium can also ensure that the positive electrode material has both good electron conductivity and ion conductivity, which helps to improve the cycle performance and storage performance of lithium manganate batteries.
  • the mass percentage of electron-withdrawing groups in the first polymer is 20%-65%. In some embodiments, the mass percentage of electron-withdrawing groups in the first polymer is 33%-65%.
  • the first polymer with the mass percentage of electron-withdrawing groups within the above range as the first cladding layer of the inner core it is beneficial to stabilize the Mn 3+ on the surface of lithium manganate in the inner core and relieve the Mn 3+ of the lithium manganate material. Dissolution problem, which is beneficial to improve the storage performance and cycle performance of the battery.
  • the first cladding layer and/or the second cladding layer are continuously distributed on the surface of the inner core.
  • the covering ratio of the second covering layer is not lower than that of the first covering layer.
  • the coating rate of the second cladding layer When the coating rate is higher, The better the isolation effect, the higher the coverage rate of the second cladding layer can be selected; at the same time, the electron-withdrawing group of the first cladding layer also gathers a large number of electrons when stabilizing the manganese ions in the inner core, which strengthens the interaction between the inner core and the second cladding layer.
  • the electron transmission between the two coating layers improves the cycle performance of the battery, but when the coating rate of the first coating layer is too high, it will increase the conduction path of lithium ions, resulting in an increase in the ionic impedance of the battery, which will instead make the battery The cycle performance and storage performance are reduced. Therefore, in this application, the covering ratio of the optional second coating layer is not lower than that of the first coating layer.
  • the mass percentage of the first cladding layer is 0.15%-2.5%. In some embodiments, the mass percentage of the first cladding layer is 0.4%-2%. Further optionally, the mass percentage of the first cladding layer is 0.4%-1.6%. And/or, based on the mass of the inner core, the mass percentage of the second cladding layer is 0.1%-2%. Optionally, the mass percentage of the second cladding layer is 0.3%-1.8%. Further, in some embodiments, the mass percentage of the second cladding layer is 0.3%-1.5%.
  • the mass percentage of the first cladding layer and the second cladding layer in an appropriate range, it is beneficial to stabilize the Mn 3+ on the surface of the lithium manganese oxide material, and at the same time combine with Lewis acids such as PF5 in the electrolyte, Mn dissolution can be alleviated, and at the same time, it can ensure that the positive electrode material has both good lithium ion conductivity and electron conductivity.
  • the total mass percentage of the first polymer and the polysaccharide is ⁇ 3.8%. In some embodiments, the total mass percentage of the first polymer and the polysaccharide is ⁇ 3.5%. Further, in some embodiments, the total mass percentage of the first polymer and the polysaccharide is ⁇ 3%.
  • the total mass percentage of the first polymer and the polysaccharide is ⁇ 3%.
  • the first polymer is selected from polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethylene terephthalate, polybutyl methacrylate, polymethacrylic acid One or more of ethyl ester, polyacrylonitrile, polynitrile acrylate, nitrile rubber, acrylonitrile copolymer.
  • a polymer containing an electron-withdrawing group as the first polymer, the Mn 3+ on the surface of lithium manganate can be stabilized, and the problem of Mn dissolution in the lithium manganate battery system can be alleviated.
  • the molecular structure of the polysaccharide is composed of multiple repeating units containing oxygen atoms, and in the repeating units, the mass proportion of oxygen element is not less than 25%.
  • the present application selects polysaccharides whose oxygen content is within the above range. Due to its high oxygen content, it can effectively combine with the Lewis acid in the electrolyte, reduce the generation of HF in the electrolyte, and effectively relieve the lithium manganate positive electrode. The dissolution of Mn ions in the material can further improve the storage performance and cycle performance of the battery.
  • the weight average molecular weight of the polysaccharide ranges from 20,000 to 270,000. In some embodiments, the weight average molecular weight of the polysaccharide ranges from 30,000 to 220,000. In the present application, if polysaccharides within the range of the above-mentioned weight average molecular weight are used, it can ensure that the polysaccharides have a high oxygen content, and by complexing Lewis acids such as PF5 in the electrolyte, the generation of HF in the electrolyte can be reduced, thereby alleviating the manganese in the positive electrode material. Dissolution problem, thus playing a role in improving battery cycle performance.
  • the polysaccharide is selected from one or more of sodium alginate, potassium alginate, guar gum, kale gum, carrageenan, and agar.
  • the above-mentioned substances are polysaccharides rich in oxygen atoms, which can be combined with Lewis acids such as PF5 in the electrolyte to reduce the generation of HF in the electrolyte and alleviate the Mn dissolution problem of the lithium manganate cathode material, thereby further improving the performance of the battery. storage and cycling properties.
  • the positive electrode material has a specific surface area of 0.15 m 2 /g to 1.5 m 2 /g. In some embodiments, the positive electrode material has a specific surface area of 0.2m 2 /g ⁇ 0.8m 2 /g. In the present application, by controlling the specific surface area of the positive electrode material within a reasonable range, the contact area between the electrolyte solution and the positive electrode material can be reduced, which is beneficial to reduce interface side reactions and ensure the improvement effect of Mn dissolution.
  • the second aspect of the present application provides a method for preparing a positive electrode material, at least including the following steps:
  • core comprises formula I compound with spinel structure:
  • M is selected from Al, Mg, Ga, Ti, Fe, Nb, Zn, Go , one or more elements in Ni, Sn, Cr;
  • A is selected from one or more elements in F, S, Cl;
  • the first coating solution containing the first polymer contains electron-withdrawing groups, the electron-withdrawing groups are selected from at least one of ester groups or nitrile groups; the inner core is placed in the first coating In the covering liquid, the first polymer is attached to the surface of the inner core to obtain the primary product;
  • a second coating solution containing polysaccharide is provided, and the primary product is placed in the second coating solution, so that at least a part of the surface of the primary product has a second coating layer attached to obtain a positive electrode material.
  • the positive electrode material can be prepared simply and easily, which has the advantages of low energy consumption, low cost, and high synthesis efficiency, and is conducive to large-scale production; in addition, the positive electrode material prepared by the above-mentioned method is available in The binding force between the two cladding layers and between the first cladding layer and the inner core is good, and the coverage of the first cladding layer and the second cladding layer on the surface of the material can be flexibly adjusted.
  • the mass percentage of the first polymer in the first coating liquid, is 0.05%-20%. In some embodiments, the mass percentage of the first polymer is 0.1%-12%. And/or, the mass percentage of the inner core and the first coating liquid is 0.05%-70%. In some embodiments, the mass percentage of the inner core and the first coating liquid is 0.1% ⁇ 60%. In the present application, if the mass percentage of the first polymer in the first coating liquid, or the mass percentage of the inner core and the first coating liquid is too high, the inner core is prone to agglomeration in the coating liquid. Therefore, by controlling the first The mass percentage of the first polymer in the coating liquid, or the mass percentage of the inner core and the first coating liquid, is in an appropriate range, which is conducive to achieving uniform coating of the first coating layer on the surface of the inner core.
  • the mass percentage of polysaccharide in the second coating solution is 0.05%-12%. In some embodiments, the mass percentage of polysaccharide is 0.1%-8%. The mass percentage of the primary product and the second coating solution is 0.05%-70%. In some embodiments, the mass percentage of the primary product and the second coating solution is 0.1%-60%. In the present application, if the mass percentage of the polysaccharide in the second coating liquid, or the mass percentage of the primary product and the second coating liquid is too high, the primary product is prone to agglomeration in the second coating liquid. Therefore, by controlling the The mass percentage of the polysaccharide in the second coating solution, or the mass percentage of the primary product and the second coating solution is in an appropriate range, which is beneficial to realize the uniform coating of the second coating layer on the surface of the inner core.
  • the third aspect of the present application provides a positive electrode sheet, which includes the positive electrode material of the first aspect of the present application or the positive electrode material obtained according to the preparation method of the second aspect of the present application.
  • a fourth aspect of the present application provides a secondary battery, including the positive electrode sheet of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery module including the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, including the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electric device, including at least one of the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application.
  • the present application arranges the first cladding layer containing the first polymer on the surface of the lithium manganate core having a spinel structure, due to the first polymer
  • the electron-withdrawing group in the Mn 3+ deviates the electrons of Mn 3+ to the electron-withdrawing group, so that the average valence of manganese increases, which can effectively stabilize the Mn 3+ on the surface of lithium manganate, and at the same time ensure the electron-conducting ability of the inner lithium manganate material good.
  • a second coating layer containing polysaccharides is further provided, and the surface of the polysaccharides is rich in oxygen to make it react with Lewis acids such as phosphorus pentafluoride (PF 5 )
  • Lewis acids such as phosphorus pentafluoride (PF 5 )
  • PF 5 phosphorus pentafluoride
  • HF hydrofluoric acid
  • the -CO ether bond in polysaccharides can chelate with the manganese ions dissolved from the inner core, it helps to further inhibit lithium manganate Dissolution of manganese ions in the core.
  • the generation of HF in the electrolyte is greatly reduced, and the lithium manganate core is effectively suppressed.
  • the dissolution of Mn ions in the medium can also ensure that the positive electrode material has both good electron conductivity and ion conductivity, which helps to improve the cycle performance and storage performance of lithium manganate batteries.
  • FIG. 1 is a schematic structural view of a positive electrode material according to an embodiment of the present application.
  • FIG. 2 is the 45° C. cycle performance test results of the secondary batteries made of positive electrode materials obtained in Example 1 and Comparative Examples 1-4.
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and 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 and may be combined arbitrarily, ie 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, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, 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" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • a method comprising steps (a) and (b) means that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially.
  • the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), and may also include step (a) , (c) and (b), may also include steps (c), (a) and (b) and the like.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: 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).
  • Lithium manganese oxide is an important type of positive electrode material. Due to its high relative content of Mn element, there is a problem of high Mn dissolution, which leads to a certain degree of attenuation in the cycle performance of the battery system. In order to improve the Mn dissolution problem of lithium manganese oxide materials, it is more effective to coat, dope, or add HF scavenger on the surface of the material. However, how to coat and modify the ionic conductivity of the lithium manganate material without reducing the ionic conductivity of the lithium manganate material, and at the same time avoid the increase of the polarization degree of the lithium manganate material and the decrease of the available capacity still needs further improvement and exploration.
  • the application proposes a positive electrode material comprising:
  • the inner core includes a compound of formula I having a spinel structure:
  • M is selected from Al, Mg, Ga, Ti, Fe, Nb, Zn, Go , one or more of Ni, Sn, Cr, A is selected from one or more of F, S, Cl;
  • the first coating layer includes a first polymer containing electron-withdrawing groups, and the electron-withdrawing groups are selected from at least one of ester groups or nitrile groups; the second coating layer contains polysaccharides.
  • the first cladding layer containing the first polymer is arranged on the surface of the lithium manganese oxide core with a spinel structure, because the electron-withdrawing group in the first polymer transfers the electrons of Mn 3+ to the electron-withdrawing group.
  • the group deviation increases the average valence of manganese, which can effectively stabilize the Mn 3+ on the surface of lithium manganese oxide, and at the same time ensure that the inner lithium manganate material has good electron conductivity.
  • a second coating layer containing polysaccharides is further provided to combine with Lewis acids such as phosphorus pentafluoride (PF5) by utilizing the characteristics of the surface of polysaccharides rich in oxygen elements.
  • HF hydrofluoric acid
  • the -CO ether bond in polysaccharides can chelate with the manganese ions dissolved from the inner core, it helps to further inhibit the lithium manganate inner core.
  • Dissolution of manganese ions in the medium by setting the above-mentioned double-layer coating structure on the core of lithium manganate, while realizing the physical isolation between the electrolyte and the core of lithium manganate, the generation of HF in the electrolyte is greatly reduced, and the lithium manganate core is effectively suppressed.
  • the dissolution of Mn ions in the medium can also ensure that the positive electrode material has both good electron conductivity and ion conductivity, which helps to improve the cycle performance and storage performance of lithium manganate batteries.
  • the mass percentage of electron-withdrawing groups in the first polymer is 20%-65%. In some embodiments, the mass percentage of electron-withdrawing groups in the first polymer is 33%-65%. In the present application, when the mass percentage of the electron-withdrawing group in the first polymer is within the above range, the stabilization effect of the first polymer on the Mn ions in the inner core is more significant, which can further alleviate the Mn 3+ dissolution problem, thereby having It helps to improve the cycle performance and storage performance of the battery.
  • the first cladding layer and/or the second cladding layer are continuously distributed on the surface of the inner core.
  • the covering ratio of the second covering layer is not lower than that of the first covering layer.
  • the coating rate of the second cladding layer When the coating rate is higher, The better the isolation effect, the higher the coverage rate of the second cladding layer can be selected; at the same time, the electron-withdrawing group of the first cladding layer also gathers a large number of electrons when stabilizing the manganese ions in the inner core, which strengthens the interaction between the inner core and the second cladding layer.
  • the electron transmission between the two coating layers improves the cycle performance of the battery, but when the coating rate of the first coating layer is too high, it will increase the conduction path of lithium ions, resulting in an increase in the ionic impedance of the battery, which will instead make the battery The cycle performance and storage performance are reduced. Therefore, in the present application, the coverage rate of the second coating layer is not lower than that of the first coating layer.
  • the mass percentage of the first cladding layer is 0.15%-2.5%. In some embodiments, the mass percentage of the first cladding layer is 0.4%-2%. Further, in some embodiments, the mass percentage of the first cladding layer is 0.4%-1.6%. And/or, based on the mass of the inner core, the mass percentage of the second cladding layer is 0.1%-2%. In some embodiments, the mass percentage of the second cladding layer is 0.3% ⁇ 1.8%. Further, in some embodiments, the mass percentage of the second cladding layer is 0.3%-1.5%.
  • the mass percentage of the first coating layer is within the above range, it is beneficial to stabilize the Mn 3+ on the surface of the lithium manganese oxide material, alleviate the dissolution of Mn, and at the same time ensure the transmission of lithium ions.
  • the mass percentage of the second coating layer is within the above range, it is beneficial to combine with Lewis acid such as PF5 in the electrolyte to alleviate the dissolution of Mn, and at the same time, it can ensure that the positive electrode material has both good lithium ion conductivity and electron conductivity characteristics.
  • the total mass percentage of the first polymer and the polysaccharide is ⁇ 3.8%. In some embodiments, the total mass percentage of the first polymer and the polysaccharide is ⁇ 3.5%. Further, in some embodiments, the total mass percentage of the first polymer and the polysaccharide is ⁇ 3%.
  • the total mass percentage of the first polymer and the polysaccharide is ⁇ 3%.
  • the first polymer is selected from polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethylene terephthalate, polybutyl methacrylate, polymethacrylic acid One or more of ethyl ester, polyacrylonitrile, polynitrile acrylate, nitrile rubber, and acrylonitrile copolymer.
  • the molecular structure of the polysaccharide is composed of multiple repeating units containing oxygen atoms, and in the repeating units, the mass proportion of oxygen element is not less than 25%.
  • the present application selects polysaccharides whose oxygen content is within the above range. Due to its high oxygen content, it can effectively combine with the Lewis acid in the electrolyte, reduce the generation of HF in the electrolyte, and effectively relieve the lithium manganate positive electrode. The dissolution of Mn ions in the material can further improve the storage performance and cycle performance of the battery.
  • the mass proportion of oxygen in the repeating unit of the polysaccharide molecular structure can be tested by methods known in the art.
  • an organic elemental analysis method can be used, for example, a Vario EL III elemental analyzer from German Elementar Company can be used for testing.
  • the weight average molecular weight of the polysaccharide ranges from 20,000 to 270,000. In some embodiments, the weight average molecular weight of the polysaccharide ranges from 30,000 to 220,000.
  • the present application can ensure that the polysaccharides have a high oxygen content, and reduce the generation of HF in the electrolyte by complexing Lewis acids such as PF5 in the electrolyte, thereby alleviating the dissolution of manganese in the positive electrode material. , so as to improve the battery cycle performance.
  • the weight average molecular weight of polysaccharides can be tested by methods known in the art.
  • gel permeation chromatography can be used for determination, such as Agilent's PL-GPC50, PL-GPC220 and other instruments.
  • the polysaccharide is selected from one or more of sodium alginate, potassium alginate, guar gum, kale gum, carrageenan, and agar.
  • the polysaccharide is composed of one or more of uronic acid, mannose and galactose.
  • the positive electrode material has a specific surface area of 0.15 square meters per gram (m 2 /g) to 1.5 m 2 /g. In some embodiments, the positive electrode material has a specific surface area of 0.2m 2 /g ⁇ 0.8m 2 /g. When the specific surface area of the positive electrode material is too large, the contact area between the electrolyte and the positive electrode material may be excessively increased, resulting in a poor effect on the improvement of Mn dissolution; the positive electrode material within the above specific surface area can effectively alleviate the Mn dissolution problem, thereby It is beneficial to improve the cycle performance and storage performance of the positive electrode material.
  • the specific surface area of the positive electrode material can be tested by methods known in the art.
  • the nitrogen adsorption specific surface area analysis test method can be used to test, and the gas adsorption method (BET method) can be used to calculate, wherein the nitrogen adsorption specific surface area analysis test can be carried out by the Tri Star ii3020 type specific surface area and pore analyzer of the Micromeritics company in the United States.
  • the present application also provides a method for preparing a positive electrode material, at least including the following steps:
  • core comprises formula I compound with spinel structure:
  • M is selected from Al, Mg, Ga, Ti, Fe, Nb, Zn, Go , one or more elements in Ni, Sn, Cr;
  • A is selected from one or more elements in F, S, Cl;
  • the first coating solution containing the first polymer contains electron-withdrawing groups, the electron-withdrawing groups are selected from at least one of ester groups or nitrile groups; the inner core is placed in the first coating In the covering liquid, the first polymer is attached to the surface of the inner core to obtain the primary product;
  • a second coating solution containing polysaccharide is provided, and the primary product is placed in the second coating solution, so that at least a part of the surface of the primary product is attached with a second coating layer to obtain a positive electrode material; wherein, the second coating The coating contains polysaccharides.
  • the preparation of the positive electrode material can be carried out simply and easily, and has the advantages of low energy consumption, low cost, and high synthesis efficiency, which is conducive to large-scale production; in addition, through the above
  • the positive electrode material prepared by the method has good bonding force between the two cladding layers and between the first cladding layer and the inner core, and can flexibly control the coverage of the first cladding layer and the second cladding layer on the surface of the material .
  • the mass percentage of the first polymer in step (2), in the first coating solution, is 0.05%-20%. In some embodiments, the mass percentage of the first polymer is 0.1%-12%. And/or, the mass percentage of the inner core and the first coating liquid is 0.05%-70%. In some embodiments, the mass percentage of the inner core and the first coating liquid is 0.1% ⁇ 60%. In the present application, if the mass percentage of the first polymer in the first coating liquid, or the mass percentage of the inner core and the first coating liquid is too high, the inner core is prone to agglomeration in the coating liquid. Therefore, by controlling the first The mass percentage of the first polymer in the coating liquid, or the mass percentage of the inner core and the first coating liquid, is in an appropriate range, which is conducive to achieving uniform coating of the first coating layer on the surface of the inner core.
  • the first coating solution contains an organic solvent, and the organic solvent is selected from acetone, tetrahydrofuran, dimethylacetamide, dimethyl sulfoxide, dichloromethane, and chloroform, One or more of dichloroethane, trifluoroacetic acid, N,N-dimethylformamide. Selecting a suitable organic solvent as the solvent of the first coating solution can better dissolve the first polymer and achieve a better coating effect.
  • the mass percentage of the polysaccharide in the second coating solution is 0.05%-12%. In some embodiments, the mass percentage of polysaccharide is 0.1%-8%. And/or, the mass percentage of the primary product and the second coating liquid is 0.05%-70%. In some embodiments, the mass percentage of the primary product and the second coating solution is 0.1%-60%. In the present application, if the mass percentage of the polysaccharide in the second coating liquid, or the mass percentage of the primary product and the second coating liquid is too high, the primary product is prone to agglomeration in the second coating liquid. Therefore, by controlling the The mass percentage of the polysaccharide in the second coating solution, or the mass percentage of the primary product and the second coating solution is in an appropriate range, which is beneficial to realize the uniform coating of the second coating layer on the surface of the inner core.
  • the stirring temperature is optionally 25° C. (Celsius) to 100° C.
  • the stirring time is optionally 4 h (hours) to 24 h.
  • the drying temperature is optionally 8°C-150°C, and the drying time is optionally 6h-24h.
  • the gaseous atmosphere is an inert non-oxidizing gas, optionally nitrogen or argon.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode material according to the first aspect of the application or the positive electrode material obtained according to the preparation method of the second aspect of the application.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • a metal foil or a composite current collector can be used as the positive electrode current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode material is a double-layer coated positive electrode material obtained by the preparation method of the present application.
  • positive electrode materials for batteries known in the art can be used for mixed use.
  • the positive electrode material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as battery cathode materials can also be used. These positive electrode materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium cobalt manganese oxides, lithium nickel cobalt oxides, lithium nickel cobalt manganese oxides (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 for short), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM 523 for short), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 for short), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also called NCM 622 for short), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also called NCM 811 for short), lithium-rich oxides and their modified compounds, etc.
  • lithium manganese oxides such as LiMnO 2 , LiMn 2 O 4
  • lithium cobalt manganese oxides such as LiNi 1/3 Co 1/3 Mn 1/3 O 2
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP for short)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate ( For example, at least one of LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of meta-copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the positive electrode sheet, such as positive electrode material, conductive agent, binding agent and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can adopt metal foil or composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • negative electrode active materials known in the art for batteries can be used as the negative electrode active material.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from at least one of simple tin, tin oxide and tin alloy.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may also optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl At least one of acrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binding agent and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • an electrolytic solution is used as the electrolyte.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the electrolyte salt can be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonyl imide, At least one of lithium fluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent can be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene propylene carbonate ester, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, butyl At least one of ethyl acetate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • Secondary batteries using an electrolyte and some secondary batteries using a solid electrolyte, also include a separator.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation.
  • the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, and the like.
  • 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 case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a case 51 and a cover plate 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 5 is a 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 may be fixed by fasteners.
  • the battery module 4 may further include a case 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 one or more, and the specific number can be selected by those skilled in the art 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 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 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 also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • a secondary battery, a battery module, or a battery pack can be used as a power source of a power consumption device, and can also be used as an energy storage unit of the power consumption device.
  • Electric devices can include 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, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • secondary batteries, battery modules, or battery packs can be selected according to their usage requirements.
  • FIG. 8 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is usually required to be light and thin, and a secondary battery can be used as a power source
  • the above solid powder and the above second coating liquid were placed in a wet packer, dried at 100°C while stirring in an air atmosphere, and then ground, crushed and sieved to obtain both the first coating layer and the second coating layer. It is a positive electrode material with continuous distribution and a specific surface area of 0.336m 2 /g.
  • Example 2 Except that the nitrile rubber is replaced by polymethyl methacrylate, and the solvent is replaced by N,N-dimethylformamide, other conditions are the same as in Example 1, thus obtaining the first coating layer, the second coating layer Both are continuously distributed, and the specific surface area is a positive electrode material of 0.245m 2 /g.
  • Example 2 Except that the nitrile rubber is replaced by polyethylene terephthalate, and the solvent is replaced by a mixed solvent of trifluoroacetic acid and dichloromethane, other conditions are the same as in Example 1, thus obtaining the first cladding layer, the second The two coating layers are continuously distributed, and the specific surface area is a positive electrode material of 0.273m 2 /g.
  • Example 2 Except that the nitrile rubber is replaced by polyacrylonitrile, and the solvent is replaced by N, N-dimethylformamide, other conditions are the same as in Example 1, so that the first coating layer and the second coating layer are continuous Distribution, a positive electrode material with a specific surface area of 0.261m 2 /g.
  • the positive electrode material is 0.253m 2 /g.
  • Example 1 Except that the nitrile rubber is replaced by polyacrylonitrile-based acrylate, and the solvent is replaced by acetone, other conditions are the same as in Example 1, so that the first coating layer and the second coating layer are continuously distributed, and the specific surface area is 0.490 m 2 /g of positive electrode material.
  • Example 4 Except that the amount of polyacrylonitrile used was adjusted to 0.10 g, other conditions were the same as in Example 4, thus obtaining a positive electrode with a continuous distribution of the first coating layer and the second coating layer and a specific surface area of 0.255 m 2 /g Material.
  • Example 4 Except that the amount of polyacrylonitrile used was adjusted to 2.50 g, the other conditions were the same as in Example 4, thus obtaining a positive electrode with a specific surface area of 0.310 m 2 /g in which both the first coating layer and the second coating layer were continuously distributed. Material.
  • Example 4 Except that the amount of polyacrylonitrile used was adjusted to 3.00 g, the other conditions were the same as in Example 4, thus obtaining a positive electrode with a specific surface area of 0.309 m 2 /g in which both the first coating layer and the second coating layer were continuously distributed. Material.
  • Example 4 Except that sodium alginate was replaced by carrageenan, the other conditions were the same as in Example 4, thereby obtaining a positive electrode material with a specific surface area of 0.283 m 2 /g, in which both the first coating layer and the second coating layer were continuously distributed.
  • Example 4 Except that sodium alginate was replaced by agar, the other conditions were the same as in Example 4, thereby obtaining a positive electrode material with a specific surface area of 0.291 m 2 /g in which both the first coating layer and the second coating layer were continuously distributed.
  • Example 4 Except that sodium alginate was replaced by guar gum, other conditions were the same as in Example 4, thus obtaining a positive electrode material with a continuous distribution of the first coating layer and the second coating layer and a specific surface area of 0.279 m 2 /g .
  • Example 4 Except that the amount of sodium alginate used was adjusted to 0.30 g, other conditions were the same as in Example 4, thereby obtaining a positive electrode with a continuous distribution of the first coating layer and the second coating layer and a specific surface area of 0.297 m 2 /g Material.
  • Example 4 Except that the amount of sodium alginate used was adjusted to 1.50 g, other conditions were the same as in Example 4, thus obtaining a positive electrode with a continuous distribution of the first coating layer and the second coating layer and a specific surface area of 0.428 m 2 /g Material.
  • Example 4 Except that the amount of sodium alginate used was adjusted to 1.80 g, other conditions were the same as in Example 4, thereby obtaining a positive electrode with a continuous distribution of the first coating layer and the second coating layer and a specific surface area of 0.537 m 2 /g Material.
  • Example 4 Except that sodium alginate with a weight average molecular weight of 12,000 is replaced by sodium alginate with a weight average molecular weight of 20,000, other conditions are the same as in Example 4, so that the first coating layer and the second coating layer are continuously distributed. , a positive electrode material with a specific surface area of 0.319m 2 /g.
  • Example 4 Except that sodium alginate with a weight average molecular weight of 12,000 is replaced by sodium alginate with a weight average molecular weight of 30,000, other conditions are the same as in Example 4, thus obtaining the continuous distribution of the first coating layer and the second coating layer , a positive electrode material with a specific surface area of 0.307m 2 /g.
  • Example 4 Except that sodium alginate with a weight-average molecular weight of 12,000 is replaced by sodium alginate with a weight-average molecular weight of 270,000, other conditions are the same as in Example 4, so that both the first coating layer and the second coating layer are continuously distributed. , a positive electrode material with a specific surface area of 0.729m 2 /g.
  • Example 4 Except that sodium alginate with a weight average molecular weight of 12,000 is replaced by sodium alginate with a weight average molecular weight of 300,000, the other conditions are the same as in Example 4, thus obtaining the continuous distribution of the first coating layer and the second coating layer , a positive electrode material with a specific surface area of 1.520m 2 /g.
  • LiMn 2 O 4 with a specific surface area of 0.267m 2 /g was put into the test.
  • LiMn 2 O 4 and the above-mentioned first polymer coating solution in a wet packer, and dry them while stirring in a nitrogen atmosphere at 120°C to obtain only the first polymer coating with a specific surface area of 0.229m 2 /g of cathode material.
  • LiMn 2 O 4 and the above-mentioned second coating solution in a wet packer, and dry them while stirring in an air atmosphere at 100°C to obtain a solid material with a specific surface area of 0.275m 2 /g coated only with polysaccharides .
  • the finished positive electrode material in each of the above examples and comparative examples is used as the positive electrode material, and the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are mixed in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3 After being fully stirred and mixed evenly in the medium, it is coated on an aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet.
  • PVDF polyvinylidene fluoride
  • a porous polymer film made of polyethylene (PE) is used as the separator.
  • the positive electrode sheet, the separator and the negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrodes to play the role of isolation, and the bare cell is obtained by winding.
  • the electrolyte is 1mol/L (mole per liter) LiPF 6 /(ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC)) (volume ratio 1:1:1). Putting the bare cell in the outer package, injecting the above-mentioned electrolyte solution and packaging to obtain a secondary battery.
  • Each secondary battery prepared above was charged to 4.3V at 0.33C, then charged at a constant voltage at 4.3V to a current ⁇ 0.05C, and finally discharged to 3.82V at 0.33C, and stored at a constant temperature of 60°C. Then the capacity was measured every 15 days. When the capacity decayed to 80%, the secondary battery was disassembled, and the amount of Mn dissolved on the negative pole piece was measured using a thermo ICAP 7000 plasma emission spectrometer and inductively coupled plasma emission spectrometry.
  • the positive electrode materials obtained in Examples 1-27 adopt a double coating layer structure on the surface of the inner core, and further select polymers containing electron-withdrawing groups and polysaccharides with high oxygen content as coatings in turn.
  • the material alleviates the Mn dissolution problem in the lithium manganese oxide battery system, and also improves the cycle performance of the battery.
  • the positive electrode material obtained in Comparative Example 1 was not coated, and its Mn dissolution amount was large, and its cycle performance was poor.
  • the positive electrode material obtained in Comparative Example 2 was only coated with the first coating layer containing the first polymer, and the positive electrode material obtained in Comparative Example 3 was only coated with the second coating layer containing polysaccharide.
  • Comparative Example 1 there is a slight improvement in cycle performance and Mn dissolution, but the improvement in cycle performance and Mn dissolution is not as good as that of double-layer coating due to the failure to achieve the synergistic effect exhibited by double-layer coating (Example 4) is obviously improved.
  • the positive electrode material obtained in Comparative Example 4 adopts a double coating layer structure, the sequence of the inner and outer coating layers is opposite to that of Example 4. Therefore, the electron-withdrawing groups in the first polymer cannot play the role of Mn 3+ charge transfer on the surface of the positive electrode material, and the polysaccharide rich in oxygen in the second coating layer cannot play the role of reducing HF generation, so Neither the amount of manganese dissolution nor the cycle performance has been effectively improved.
  • Example 4 polyacrylonitrile is used as the first polymer, and sodium alginate is used as the selected polysaccharide.
  • polyacrylonitrile has a certain ion conductivity, which has little effect on the transmission of lithium ions; on the other hand, the nitrile group in polyacrylonitrile has strong electron-withdrawing properties, which can better stabilize the surface of lithium manganate.
  • the trivalent manganese ions on the surface can alleviate the problem of Mn dissolution.
  • sodium alginate has higher oxygen content and -COONa group, which is beneficial to combine with Lewis acid. Therefore, in terms of manganese dissolution and cycle performance, Example 4 has achieved good improvement.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

L'invention concerne un matériau d'électrode positive et son procédé de préparation. Le matériau d'électrode positive comprend un noyau interne (11) ainsi qu'une première couche de revêtement (12) et une seconde couche de revêtement (13) qui sont disposées consécutivement sur la surface du noyau interne (11). Le noyau interne (11) comprend un composé de formule I ayant une structure de spinelle comme suit : Li1+xMn2-yMyO4-zAz (formule I), dans laquelle 0≤x≤1, 0≤y≤0,5, 0≤z≤0,5, x, y et z ne sont pas nuls en même temps, M est choisi parmi un ou plusieurs éléments parmi Al, Mg, Ga, Ti, Fe, Nb, Zn, Ni, Sn et Cr, et A est choisi parmi un ou plusieurs éléments parmi F, S et Cl. La première couche de revêtement (12) comprend un premier polymère contenant un groupe attracteur d'électrons, le groupe attracteur d'électrons étant choisi parmi un groupe ester et/ou un groupe nitrile, et la seconde couche de revêtement (13) contenant un polysaccharide.
PCT/CN2022/094202 2021-09-29 2022-05-20 Matériau d'électrode positive et son procédé de préparation, batterie secondaire, module de batterie, bloc-batterie et dispositif électrique WO2023050833A1 (fr)

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