WO2022109886A1 - 复合正极材料、其制备方法、正极极片、二次电池及包含该二次电池的电池模块、电池包和装置 - Google Patents

复合正极材料、其制备方法、正极极片、二次电池及包含该二次电池的电池模块、电池包和装置 Download PDF

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WO2022109886A1
WO2022109886A1 PCT/CN2020/131578 CN2020131578W WO2022109886A1 WO 2022109886 A1 WO2022109886 A1 WO 2022109886A1 CN 2020131578 W CN2020131578 W CN 2020131578W WO 2022109886 A1 WO2022109886 A1 WO 2022109886A1
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positive electrode
lithium
optionally
active material
composite
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PCT/CN2020/131578
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English (en)
French (fr)
Inventor
王帮润
柳娜
梁成都
刘勇超
孙信
谢浩添
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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 CN202080102742.9A priority Critical patent/CN116114082A/zh
Priority to PCT/CN2020/131578 priority patent/WO2022109886A1/zh
Priority to EP20962777.7A priority patent/EP4071856A4/en
Publication of WO2022109886A1 publication Critical patent/WO2022109886A1/zh
Priority to US17/971,500 priority patent/US11855277B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of energy storage devices, and in particular relates to a composite positive electrode material, a preparation method thereof, a positive electrode pole piece, a secondary battery, and a battery module, battery pack and device comprising the secondary battery.
  • a first aspect of the present application provides a composite positive electrode material, which comprises a core and a coating layer covering at least a part of the surface of the core, wherein the core comprises a positive electrode lithium supplement material, and the positive electrode lithium supplement material comprises a lithium-rich metal oxide; the coating The layer includes a positive electrode active material.
  • the positive electrode active material coating layer is Good lithium ion conductor, which can greatly improve the efficiency of lithium replenishment. Therefore, the use of the composite cathode material of the present application can effectively make up for the active lithium lost during the first charge and discharge of the battery, and can improve the first charge and discharge capacity of the battery, thereby improving the energy density. Further, the use of the positive electrode active material to coat the positive electrode lithium-supplementing material may not introduce additional inactive substances, thereby facilitating the battery to obtain a higher energy density. Further, the use of the composite cathode material of the present application also significantly extends the cycle life of the battery.
  • the positive electrode active material is distributed on the surface of the core in the form of independent particles.
  • the composite cathode material satisfies the above conditions, and the battery using the composite cathode material can obtain higher energy density and cycle performance.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material is 1:2 to 1:35, optionally 1:5 to 1:30, and further optionally 1:10 ⁇ 1:20.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material is within the range, so that the battery can obtain higher energy density and cycle performance.
  • the median particle size D v 50 of the positive electrode lithium supplement material is 2 ⁇ m to 35 ⁇ m, optionally 5 ⁇ m to 30 ⁇ m, and further optionally 15 ⁇ m to 25 ⁇ m.
  • the D v 50 of the positive electrode lithium supplement material is in an appropriate range, which can improve the capacity utilization rate of the positive electrode lithium supplement material, and further improve the energy density and cycle performance of the battery.
  • the median particle size D v 50 of the positive electrode active material is 0.1 ⁇ m to 15 ⁇ m, optionally 0.2 ⁇ m to 10 ⁇ m, and further optionally 0.5 ⁇ m to 6 ⁇ m.
  • the Dv50 of the cathode active material is in an appropriate range, which can further improve the energy density and cycle performance of the battery.
  • the lithium-rich metal oxide may be selected from Li 2 M 1 O 2 , Li 2 M 2 O 3 , Li 3 M 3 O 4 , Li 5 M 4 O 4 , Li 6 M 5 O One or more of 4 , wherein M 1 includes one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, and M 2 includes Mn, Sn, Mo, Ru, Ir one or more of M3, M3 includes one or more of V, Nb, Cr, Mo, M4 includes one or more of Fe, Cr, V, Mo, M5 includes Co, V, One or more of Cr, Mo, and the average valence state of each metal element except Li in the lithium-rich metal oxide is lower than its own highest oxidation valence state.
  • the lithium-rich metal oxide may be selected from Li 3 VO 4 , Li 2 MnO 2 , Li 3 NbO 4 , Li 5 FeO 4 , Li 6 CoO 4 , Li 2 NiO 2 , Li 2 CuO 2 and one or more of Li 2 Cu x1 Ni 1-x1 M y1 O 2 , wherein 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, M is selected from one of Zn, Sn, Mg, Fe and Mn species or several. Optionally, 0.2 ⁇ x1 ⁇ 0.8. Further optionally, 0.5 ⁇ x1 ⁇ 0.7.
  • the positive electrode active material may be selected from one or more of layered lithium transition metal oxides, spinel-structured lithium metal oxides, and polyanionic positive electrode materials.
  • the lithium metal oxide with spinel structure is selected from one or more of LiMn 2 O 4 and LiNi 0.5 Mn 1.5 O 4 .
  • the polyanionic positive electrode material is selected from one of LiFePO 4 , LiMnPO 4 , LiCoPO 4 , LiNiPO 4 , Li 3 V 2 (PO 4 ) 3 , LiFe y Mn 1-y PO 4 and modified materials thereof one or more, wherein 0 ⁇ y ⁇ 1, optionally 0.2 ⁇ y ⁇ 0.8.
  • the positive electrode active material may be selected from one or more of LiFePO 4 , LiMnPO 4 , Li 3 V 2 (PO 4 ) 3 and modified materials thereof.
  • the charge cut-off voltage of the positive electrode active material is 4.2V-5.2V (vs. Li/Li + ), and the lithium-rich metal oxide can be selected from Li 6 CoO 4 , Li 5 FeO 4 , Li One or more of 2 NiO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , Li 3 VO 4 , and Li 3 NbO 4 , wherein 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, M is selected from one or more of Zn, Sn, Mg, Fe and Mn.
  • 0.2 ⁇ x1 ⁇ 0.8 is optionally, 0.2 ⁇ x1 ⁇ 0.8.
  • the median particle size D v 50 of the positive electrode active material is 1 ⁇ m ⁇ 15 ⁇ m, optionally 2 ⁇ m ⁇ 10 ⁇ m, and further optionally 4 ⁇ m ⁇ 6 ⁇ m.
  • the Dv50 of the cathode active material is in the above range, which can further improve the energy density and cycle performance of the battery.
  • the charge cut-off voltage of the positive electrode active material is 3.5V-4.2V (vs. Li/Li + ), and the lithium-rich metal oxide can be selected from Li 5 FeO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , one or more of Li 2 MnO 2 , wherein 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, M is selected from Zn, Sn, Mg, Fe and one or more of Mn.
  • 0.2 ⁇ x1 ⁇ 0.8 is selected from one or more of LiFePO 4 , Li 3 V 2 (PO 4 ) 3 and LiFe y Mn 1-y PO 4 , where 0 ⁇ y ⁇ 1.
  • the median particle size D v 50 of the positive electrode active material is 0.1 ⁇ m ⁇ 3.5 ⁇ m, optionally 0.2 ⁇ m ⁇ 2 ⁇ m, and further optionally 0.5 ⁇ m ⁇ 1.5 ⁇ m.
  • the Dv50 of the cathode active material is in the above range, which can further improve the energy density and cycle performance of the battery.
  • a second aspect of the present application provides a method for preparing a composite positive electrode material, comprising the following steps:
  • the core comprising a positive electrode lithium supplement material comprising a lithium rich metal oxide
  • the coating material comprising a positive electrode active material
  • a composite positive electrode material is obtained by covering at least a part of the surface of the core with the covering material.
  • the surface coating of the positive electrode active material on the positive electrode lithium supplement material can play the role of isolating the external environment, improve the stability of the material, ensure the purity of the material and the performance of lithium supplementation, and at the same time the positive electrode activity
  • the material coating layer is a good lithium ion conductor, which can greatly improve the efficiency of lithium replenishment. Therefore, the composite positive electrode material obtained by the preparation method of the present application can effectively make up for the active lithium lost during the first charge and discharge of the battery, improve the first charge and discharge capacity of the battery, and thereby improve the energy density. Further, by using the positive electrode active material to coat the positive electrode lithium supplement material, no additional inactive substances are introduced, so that the battery can obtain a higher energy density. Further, using the composite positive electrode material prepared by the present application also significantly prolongs the cycle life of the battery.
  • a third aspect of the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer comprising the composite positive electrode material of the first aspect of the present application, or according to the second aspect of the present application The composite cathode material obtained by the preparation method.
  • the secondary battery using the same can simultaneously take into account higher initial charge-discharge capacity, higher energy density and longer cycle performance.
  • the positive electrode film layer further comprises a conductive agent and a binder, wherein, based on the total weight of the positive electrode film layer, the positive electrode film layer contains 70% by weight to 97% by weight of the composite positive electrode material, 2% to 20% by weight of the conductive agent and 1% to 25% by weight of the binder.
  • the energy density and cycle life of the secondary battery can be further improved by adjusting the proportion of the composite cathode material in the cathode film layer.
  • a fourth aspect of the present application provides a secondary battery, which includes the positive electrode sheet of the third aspect of the present application.
  • the secondary battery of the present application adopts the positive electrode sheet of the present application, it can take into account higher initial charge-discharge capacity, higher energy density and longer cycle performance at the same time.
  • 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 a device comprising 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 battery module, battery pack and device of the present application include the secondary battery described in the present application, and thus have at least the same or similar technical effects as the secondary battery.
  • FIG. 1 is a scanning electron microscope (SEM) image of a composite cathode material provided in an embodiment of the present application.
  • FIG. 2 is a SEM image of a cross-section of a composite positive electrode material provided in an embodiment of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of a secondary battery.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a battery module.
  • FIG. 6 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 7 is an exploded view of FIG. 6 .
  • FIG. 8 is a schematic diagram of one embodiment of a device in which a secondary battery is used as a power source.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • every point or single value between the endpoints of a range is included within the range, even if not expressly recited.
  • each point or single value may serve as its own lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • the term "or” is inclusive. That is, 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 present) and B is false (or absent); A is false (or absent) and B is true (or present) ; or both A and B are true (or present).
  • lithium supplementation technology can be used to increase the active lithium ion content to compensate for the loss of active lithium during the first charge and discharge of the secondary battery.
  • the main and relatively mature technology is the negative electrode lithium supplementation process, for example, a lithium metal layer is covered on the negative electrode surface by lithium powder or lithium foil.
  • the chemical properties of metallic lithium are very active, and the requirements for the environment and equipment are high, and there will be high safety risks in the process of lithium replenishment.
  • the positive electrode lithium supplementation process has higher safety and reduces the requirements for environmental control.
  • the positive electrode lithium supplementation process may be to add a lithium-rich transition metal oxide to the positive electrode slurry to prepare a lithium-rich positive electrode. During battery formation or initial cycling, the lithium-rich material of the positive electrode releases lithium to compensate for the irreversible loss of active lithium caused by the formation of the SEI film on the negative electrode.
  • lithium-rich transition metal oxides still have the problem of high activity and easy to react with moisture and carbon dioxide in the environment, reducing the effect of lithium supplementation, and the impurities introduced by the reaction will also reduce the energy density of the battery.
  • the inventors further found that the use of carbon materials or metal oxides (such as Al 2 O 3 , TiO 2 , ZrO 2 , etc.) to coat the lithium-rich transition metal oxides can isolate the external environment and prevent the lithium-rich materials from interacting with water and air in the air. carbon dioxide exposure.
  • the preparation process of the surface coating layer is complicated, especially the introduction of the non-electrochemically active coating layer also reduces the energy density of the battery.
  • the conventional coating layer is not conducive to the extraction of lithium ions from the internal lithium-replenishing material, resulting in limited improvement in battery cycle life.
  • the inventor provides a composite positive electrode material that utilizes an electrochemically active coating layer to improve the stability of the positive electrode lithium supplement material.
  • the composite positive electrode material according to the present application comprises a core and a coating layer covering at least a part of the surface of the core, the core comprises a positive electrode lithium supplement material, the positive electrode lithium supplement material comprises a lithium-rich metal oxide, and the coating layer comprises a positive electrode active material .
  • the electrochemically active coating layer means that the coating layer has good ion conductivity, which can provide a good lithium ion deintercalation channel during the charging and discharging process of the battery. Therefore, during the charging process of the battery, the coating layer can provide a good lithium ion extraction channel for the coated positive electrode lithium supplement material.
  • the positive electrode active material refers to the material that participates in the insertion and extraction of active ions in the positive electrode sheet (the electrode sheet with higher potential in the battery) during the charging and discharging process of the battery.
  • the positive electrode lithium supplement material is usually arranged at the positive electrode and can provide additional active lithium during the first or initial charging of the battery.
  • the positive electrode lithium supplement material can be used to compensate for the irreversible loss of active lithium caused by the formation of the SEI film in the negative electrode.
  • Cathode active materials generally have good stability to moisture and carbon dioxide in the air.
  • the positive electrode active material by coating the positive electrode active material on the surface of the positive electrode lithium supplement material, it can play the role of isolating the external environment, avoid the direct contact between the positive electrode lithium supplement material and the moisture and carbon dioxide in the air, reduce surface side reactions, thereby improving the material's performance. Stability, to ensure the purity of the material and the performance of lithium supplementation.
  • the coating layer of the positive electrode active material is a good lithium ion conductor, which is beneficial to the delithiation process of the lithium-replenishing material and greatly improves the lithium-replenishing efficiency.
  • the use of the composite cathode material of the present application can effectively make up for the active lithium lost during the first charge and discharge of the battery, improve the first charge and discharge capacity of the battery, and thus enable the battery to obtain a higher energy density. Further, the use of the positive electrode active material to coat the positive electrode lithium supplement material may not introduce additional inactive substances, thereby helping the battery to obtain a higher energy density.
  • the use of the composite cathode material of the present application can also significantly improve the cycle life of the battery.
  • the composite cathode material improves the capacity utilization of the cathode lithium supplement material, allowing it to release more active lithium.
  • Excessive active lithium is embedded in the negative electrode, so that the negative electrode active material is in a certain state of lithium intercalation, which can alleviate the volume change of the negative electrode active material to a certain extent, thereby reducing the risk of rupture or powder drop of the negative electrode active material.
  • the sheet maintains good electrolyte wettability and liquid retention rate.
  • this part of active lithium can also be used to make up for the loss of active lithium during the battery cycle in the middle and late cycle. Therefore, the use of the composite cathode material of the present application can further prolong the cycle life.
  • the cathode active material is distributed on the surface of the core in the form of independent particles.
  • the morphology of the composite cathode material can be observed with a scanning electron microscope (eg SIGMA300).
  • FIG. 1 is an SEM picture of a composite positive electrode material as an example.
  • FIG. 2 is an SEM image of a cross-section of a composite positive electrode material as an example.
  • the cross section of the composite cathode material can be obtained by using an ion polishing apparatus (for example, an argon ion cross section polishing apparatus, such as IB-19500CP). It can be seen from the picture that the composite cathode material is coated with a large number of cathode active material particles on the surface of the core particles.
  • the positive electrode active material on the surface of the composite positive electrode material can form an effective physical barrier, avoid the direct contact between the positive electrode lithium supplement material and the electrolyte, and reduce side effects.
  • the reaction occurs, so that the electrochemical stability of the cathode lithium supplement material is further improved.
  • the cathode active material in particle form can also better exert its high capacity characteristics. Therefore, the battery using the composite cathode material can obtain higher energy density and cycle performance.
  • the core and the cladding layer can be bonded through physical bonding (eg, intermolecular force, etc.) or chemical bonding.
  • the bonding between the core and the cladding layer is achieved through the intermolecular force between the positive electrode lithium supplement material particles and the positive electrode active material.
  • the positive electrode lithium supplement material and the positive electrode active material are bonded by intermolecular force, so that the positive electrode active material particles are closely attached to the surface of the positive electrode lithium supplement material, so that the microstructure of the composite positive electrode material is stabilized high performance and electrochemical stability. Therefore, the battery using the composite cathode material can obtain good long-term cycle performance.
  • the coverage rate of the positive electrode active material particles on the surface of the positive electrode lithium supplement material is ⁇ 60%. Further optionally, it is > 70%, > 80%, > 90%, > 95%, or 100%.
  • the coverage ratio of the positive electrode active material particles on the surface of the positive electrode lithium supplement material is within the above range, the sensitivity of the composite positive electrode material to the external environment (especially humidity) can be further reduced, and the composite positive electrode material can be effectively improved in the positive electrode slurry.
  • the gel problem in the preparation process improves the processability of the composite cathode material in the battery application process.
  • the median particle size D v 50 of the positive electrode lithium supplement material may be 2 ⁇ m ⁇ 35 ⁇ m.
  • the D v 50 of the positive electrode lithium supplement material is 4 ⁇ m ⁇ 30 ⁇ m, further optionally 5 ⁇ m ⁇ 30 ⁇ m, 5 ⁇ m ⁇ 25 ⁇ m, 5 ⁇ m ⁇ 20 ⁇ m, 10 ⁇ m ⁇ 25 ⁇ m, 10 ⁇ m ⁇ 20 ⁇ m, 12 ⁇ m ⁇ 20 ⁇ m, 15 ⁇ m ⁇ 25 ⁇ m, Or 15 ⁇ m ⁇ 20 ⁇ m.
  • the D v 50 of the positive electrode lithium supplement material is in an appropriate range, which can improve the transport process of lithium ions inside the particles, reduce the ion migration resistance, and at the same time reduce the contact area between the material and the electrolyte, and reduce the adverse effects between the electrolyte and the material. Therefore, the utilization rate of the positive electrode lithium supplement material can be improved, and the energy density and cycle performance of the battery can be further improved.
  • the positive electrode active material has a median particle size D v 50 of 0.1 ⁇ m to 15 ⁇ m.
  • the Dv 50 of the positive electrode active material is 0.2 ⁇ m ⁇ 10 ⁇ m, further optionally 0.2 ⁇ m ⁇ 2 ⁇ m, 0.2 ⁇ m ⁇ 5 ⁇ m, 0.5 ⁇ m ⁇ 1.5 ⁇ m, 0.8 ⁇ m ⁇ 1.2 ⁇ m, 0.5 ⁇ m ⁇ 6 ⁇ m, 1 ⁇ m ⁇ 15 ⁇ m, 2 ⁇ m to 10 ⁇ m, 3 ⁇ m to 8 ⁇ m, 1 ⁇ m to 5 ⁇ m, or 1 ⁇ m to 1.5 ⁇ m.
  • the Dv 50 of the positive electrode active material is in an appropriate range, which can improve the dispersion uniformity of the positive electrode active material on the surface of the positive electrode lithium supplement material and reduce the agglomeration phenomenon.
  • the coating layer formed on the surface of the positive electrode lithium supplement material has a better insulating and protective effect, and further improves the stability of the material, thereby further improving the energy density of the battery.
  • the positive electrode active material is attached to the surface of the positive electrode lithium supplement material, which can also make the positive electrode lithium supplement material play the role of stabilizing the positive electrode active material, and greatly alleviate the problem that the positive electrode active material with smaller particle size is prone to agglomeration during the battery cycle. This can further improve the cycle performance of the battery.
  • the positive electrode active material is attached to the surface of the positive electrode lithium supplement material to form larger particles, which can also improve the processing performance of the positive electrode slurry and reduce the physical gel phenomenon, so that the positive electrode sheet with good overall consistency can be prepared, and the battery can be improved. overall performance.
  • the appropriate particle size of the positive electrode active material can also improve the transport performance of active ions in the active material particles, which is beneficial to further improve the cycle performance of the battery.
  • the median particle size D v 50 of the composite cathode material is 2 ⁇ m-40 ⁇ m, optionally 3 ⁇ m-38 ⁇ m, 3 ⁇ m-30 ⁇ m, 5 ⁇ m-25 ⁇ m, 8 ⁇ m-40 ⁇ m, 10 ⁇ m-35 ⁇ m, 10 ⁇ m ⁇ 25 ⁇ m, 15 ⁇ m to 30 ⁇ m, or 10 ⁇ m to 20 ⁇ m.
  • the median particle size D v 50 of the composite positive electrode material is within the above range, it is beneficial to improve the compaction density of the positive electrode sheet, thereby improving the energy density of the battery.
  • the particles in the positive electrode sheet can be in close contact with each other, and also form a pore structure that facilitates the infiltration of the electrolyte, so the battery can also obtain higher cycle performance.
  • the median particle size (also known as volume average particle size) D v 50 of the positive electrode active material, the positive electrode lithium supplement material, and the composite positive electrode material is the meaning known in the art, and can be determined using methods known in the art. For example, it can refer to GB/T 19077-2016 particle size distribution laser diffraction method, and use a laser particle size analyzer (eg, Malvern Mastersizer 2000E, UK) to measure.
  • D v 50 represents the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material may be 1:2 to 1:35.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material is within an appropriate range, which can not only form a positive electrode active material coating layer with a suitable thickness on the surface of the positive electrode lithium supplement material, effectively improve the stability of the material, but also ensure the positive electrode in the coating layer.
  • the lithium-replenishing material can fully remove lithium to ensure the efficient performance of its lithium-replenishing performance.
  • the composite positive electrode material contains sufficient positive electrode active materials, which enables the positive electrode to have more lithium sites for the reciprocating and deintercalating lithium ions, thereby improving the reversible capacity of the battery. Therefore, the battery using the composite cathode material can obtain higher energy density and cycle performance.
  • the mass ratio of the cathode lithium supplement material to the cathode active material in the composite cathode material is 1:5 to 1:30, further optionally 1:5 to 1:25, 1:10 to 1:20, 1 :12 ⁇ 1:18, or 1:15 ⁇ 1:20.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material is within the range, so that the battery can have higher energy density and longer cycle life.
  • the mass ratio of the positive electrode lithium supplement material to the positive electrode active material in the composite positive electrode material can be tested by using a testing method known in the art.
  • ICP Inductively Coupled Plasma
  • the test can be performed in an inductively coupled plasma atomic emission spectrometer (eg ICAP7400 from Thermo Fisher Scientific, USA).
  • An exemplary test method is as follows: add 2g of the composite cathode material to an acid solution (such as aqua regia) for digestion, the digestion can be carried out under stirring (such as mechanical stirring or microwave stirring, etc.), and the digestion time can be 30min; add the digested solution to the solution.
  • the chemical constituent elements in the composite cathode material were quantitatively analyzed. Through the quantification of each element, the mass of the compound containing the element is determined, and the mass ratio of the positive electrode active material and the positive electrode lithium supplementary material is finally calculated.
  • test sample can be directly taken from the composite positive electrode material, or sampled from the positive electrode piece of the secondary battery for testing.
  • an exemplary method of obtaining a composite positive electrode material from a secondary battery is as follows:
  • step (2) Bake the dried positive electrode piece in step (1) at a certain temperature and time (for example, 120° C., 6 h), and select a region in the baked positive electrode piece to sample the composite positive electrode material.
  • a blade scraping powder can be used for sampling.
  • step (3) The composite positive electrode material collected in step (2) is subjected to sieving treatment (for example, sieving with a 200-mesh sieve), and finally a composite positive electrode material sample that can be used to test the material parameters described in this application is obtained.
  • sieving treatment for example, sieving with a 200-mesh sieve
  • the lithium-rich metal oxide may be selected from the group consisting of Li 2 M 1 O 2 , Li 2 M 2 O 3 , Li 3 M 3 O 4 , Li 5 M 4 O 4 , Li 6 M 5 O 4 one or more.
  • the valence state of each metal element except Li in Li-rich metal oxides is lower than its own highest oxidation state.
  • M 1 may include one or more of Ni, Co, Fe, Mn, Zn, Mg, Ca, and Cu.
  • M 1 includes one or more of Ni, Co, Mn, and Cu.
  • M 1 includes one or more of Ni, Cu, and Mn.
  • Li 2 M 1 O 2 may include Li 2 NiO 2 , Li 2 MnO 2 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , Li 2 Co x2 Mn 1-x2 O one or more of 2 .
  • Li 2 M 1 O 2 includes one or more of Li 2 NiO 2 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 .
  • Li 2 M 1 O 2 includes Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 .
  • 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn.
  • M 2 may include one or more of Mn, Sn, Mo, Ru, and Ir.
  • M 2 includes one or more of Mn, Mo, and Sn.
  • Li 2 M 2 O 3 may include one or more of Li 2 MnO 3 and Li 2 MoO 3 .
  • M 3 may include one or more of V, Nb, Cr, and Mo.
  • M 3 includes one or more of V, Nb, and Mo.
  • Li 3 M 3 O 4 may include one or more of Li 3 VO 4 , Li 3 NbO 4 , and Li 3 MoO 4 .
  • Li 3 M 3 O 4 includes one or more of Li 3 VO 4 and Li 3 NbO 4 .
  • M 4 may include one or more of Fe, Cr, V, and Mo.
  • M 4 includes one or more of Fe, Cr, and V.
  • Li 5 M 4 O 4 may include one or more of Li 5 FeO 4 , Li 5 CrO 4 , and Li 5 VO 4 .
  • Li 5 M 4 O 4 includes Li 5 FeO 4 .
  • M 5 may include one or more of Co, V, Cr, and Mo.
  • M 5 includes one or more of Co, V, and Cr.
  • Li 6 M 5 O 4 may include one or more of Li 6 CoO 4 , Li 6 VO 4 , and Li 6 CrO 4 .
  • Li 6 M 5 O 4 includes Li 6 CoO 4 .
  • the lithium-rich metal oxide may include one or more of Li 2 M 1 O 2 , Li 2 M 2 O 3 , Li 5 M 4 O 4 , and Li 6 M 5 O 4 .
  • the lithium-rich metal oxide may include one or more of Li 2 M 1 O 2 , Li 5 M 4 O 4 , and Li 6 M 5 O 4 . wherein M 1 , M 2 , M 4 , and M 5 are respectively as defined herein.
  • the lithium-rich metal oxide may include Li 3 VO 4 , Li 2 MnO 2 , Li 3 NbO 4 , Li 5 FeO 4 , Li 6 CoO 4 , Li 2 NiO 2 , Li 2 CuO 2 , Li 2 One or more of Cu x1 Ni 1-x1-y1 M y1 O 2 .
  • the lithium-rich metal oxide includes one or more of Li 5 FeO 4 , Li 6 CoO 4 , Li 2 NiO 2 , Li 2 CuO 2 and Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 kind.
  • the lithium-rich metal oxide includes one or more of Li 5 FeO 4 , Li 6 CoO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1- x1-y1 M y1 O 2 .
  • 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn.
  • the positive electrode active material may be selected from one or more of layered lithium transition metal oxides, spinel-structured lithium metal oxides, and polyanionic positive electrode materials.
  • the cathode active material may include a layered lithium transition metal oxide.
  • the layered lithium transition metal oxide is selected from one of LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi a Co b Mn c O 2 , LiNi ⁇ Co ⁇ Al ⁇ O 2 , and modified materials thereof or several.
  • 0.5 ⁇ a ⁇ 0.9, or 0.6 ⁇ a ⁇ 0.85. 0 ⁇ 1, 0 ⁇ 1, 0 ⁇ 1, ⁇ + ⁇ + ⁇ 1.
  • the layered lithium transition metal oxide may include LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 One or more of (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), and LiNi 0.85 Co 0.15 Al 0.05 O 2 .
  • the modification in the modified material may be doping modification or coating modification.
  • the positive active material may include a spinel-structured lithium metal oxide, such as lithium manganese oxide, lithium nickel manganese oxide, and the like.
  • a specific example is one or more of LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , and their modified materials.
  • the modification in the modified material may be doping modification or coating modification.
  • the cathode active material may include a polyanionic cathode material.
  • Polyanionic cathode materials are compounds comprising lithium, transition metals and tetrahedral or octahedral anionic structural units (XO z ) t- , wherein X can be selected from P, S, As, Mo, W.
  • X is P.
  • (XO z ) t- may be (PO 4 ) ⁇ .
  • the crystal structure of the polyanionic cathode material may be olivine type or NASICON type.
  • the polyanionic cathode material may include LiFePO 4 (LFP), LiMnPO 4 , LiCoPO 4 , LiNiPO 4 , Li 3 V 2 (PO 4 ) 3 , LiFe y Mn 1-y PO 4 , and modifications thereof One or more of the materials, where 0 ⁇ y ⁇ 1.
  • the positive electrode active material may include one or more of LiFePO 4 , LiMnPO 4 , Li 3 V 2 (PO 4 ) 3 , and modified materials thereof.
  • the positive electrode active material includes LiFePO 4 .
  • the inventor found that when the positive electrode active material and the positive electrode lithium supplement material are reasonably matched, the capacity of the lithium supplement material can be maximized, so that the battery can obtain a higher energy density. Further, the battery can also have better cycle performance.
  • the charge cut-off voltage of the positive electrode active material is 4.2V-5.2V (vs. Li/Li + ), and the lithium-rich metal oxide may be selected from Li 6 CoO 4 , Li 5 FeO 4 , Li 2 NiO 2 One or more of Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , Li 3 VO 4 , and Li 3 NbO 4 .
  • the lithium-rich metal oxide may be selected from one of Li 5 FeO 4 , Li 6 CoO 4 , Li 2 NiO 2 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 or several.
  • the lithium-rich metal oxide may be selected from one or more of Li 6 CoO 4 , Li 5 FeO 4 , Li 2 NiO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 . Further optionally, the lithium-rich metal oxide can be selected from one or more of Li 6 CoO 4 , Li 2 NiO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 . In some embodiments, the lithium-rich metal oxide includes or is Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 . In the formula, 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, and M is selected from one or more of Zn, Sn, Mg, Fe and Mn. Optionally, 0.1 ⁇ x1 ⁇ 0.9. Further optionally, 0.2 ⁇ x1 ⁇ 0.8, 0.4 ⁇ x1 ⁇ 0.6, or 0.5 ⁇ x1 ⁇ 0.7.
  • the positive active material may be selected from LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi a Co b Mn c O 2 , LiNi ⁇ Co ⁇ Al ⁇ O 2 , LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiMnPO 4.
  • LiCoPO 4 , LiNiPO 4 and their modified materials wherein a, b, c, ⁇ , ⁇ , and ⁇ are respectively as defined herein.
  • the positive electrode active material may include one or more of LiNi a Co b Mn c O 2 , LiNi ⁇ Co ⁇ Al ⁇ O 2 , and modified materials thereof.
  • the positive active material may include one or more of LiNi a Co b Mn c O 2 and modified materials thereof.
  • the median particle diameter D v 50 of the positive electrode active material is 1 ⁇ m to 15 ⁇ m. Further optionally, the D v 50 of the positive active material is 2 ⁇ m ⁇ 10 ⁇ m, 2 ⁇ m ⁇ 8 ⁇ m, 3 ⁇ m ⁇ 7 ⁇ m, 4 ⁇ m ⁇ 6 ⁇ m, 3 ⁇ m ⁇ 5 ⁇ m, or 4 ⁇ m ⁇ 7 ⁇ m.
  • the D v 50 of the positive electrode active material is in an appropriate range, which can not only protect the positive electrode lithium supplement material, but also improve the transport performance of active ions in the particles, and at the same time reduce the side reaction of the electrolyte on the particle surface, thereby It can further improve the capacity and cycle performance of the battery.
  • the charge cut-off voltage of the positive electrode active material is 3.5V-4.2V (vs. Li/Li + ), and the lithium-rich metal oxide is selected from Li 6 CoO 4 , Li 5 FeO 4 , Li 2 NiO 2 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1- y1 M y1 O 2 , Li 2 MnO 2 , one or more of them, wherein 0 ⁇ x1 ⁇ 1, 0 ⁇ y1 ⁇ 0.1, M is selected from Zn , one or more of Sn, Mg, Fe and Mn.
  • 0.2 ⁇ x1 ⁇ 0.8 further optionally, 0.5 ⁇ x1 ⁇ 0.8, 0.4 ⁇ x1 ⁇ 0.6, or 0.5 ⁇ x1 ⁇ 0.7.
  • the lithium-rich metal oxide is selected from one or more of Li 5 FeO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1- x1-y1 M y1 O 2 , and Li 2 MnO 2 . Further optionally, the lithium-rich metal oxide may be selected from one or more of Li 5 FeO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 .
  • the positive electrode active material may be selected from one or more of LiFePO 4 , Li 3 V 2 (PO 4 ) 3 and LiFe y Mn 1-y PO 4 , where 0 ⁇ y ⁇ 1.
  • 0.2 ⁇ y ⁇ 0.8 the positive electrode active material can be selected from one or more of LiFePO 4 and LiFe y Mn 1-y PO 4 .
  • the median particle size D v 50 of the positive electrode active material is 0.1 ⁇ m to 3.5 ⁇ m. Further optionally, the D v 50 of the positive electrode active material is 0.2 ⁇ m ⁇ 3 ⁇ m, 0.2 ⁇ m ⁇ 2 ⁇ m, 0.5 ⁇ m ⁇ 1.5 ⁇ m, 0.8 ⁇ m ⁇ 1.2 ⁇ m, or 1 ⁇ m ⁇ 1.5 ⁇ m.
  • the Dv50 of the positive electrode active material is in an appropriate range, which can not only protect the positive electrode lithium supplementary material, but also improve the dispersion performance of the positive electrode active material and the processing performance of the positive electrode slurry, and at the same time make the composite active material have good activity.
  • the ion transport performance can further improve the capacity exertion and cycle performance of the battery.
  • the charge-discharge voltage range of the inner core lithium-rich metal oxide and the outer layer positive electrode active material is similar, so as to ensure that the capacity of the positive electrode active material and the lithium-rich metal oxide of the lithium supplement can be maximized .
  • the present application also provides a preparation method of a composite positive electrode material, through which any one of the above composite positive electrode materials can be obtained.
  • a method for preparing a composite positive electrode material includes the following steps: providing a core, the core comprising a positive electrode lithium supplement material, and the positive electrode lithium supplement material comprising a lithium-rich metal oxide; providing a coating material, the coating The material includes a positive electrode active material; at least a part of the surface of the core is covered by the coating material to obtain a composite positive electrode material.
  • the core can be selected from the lithium-rich metal oxides described herein, and the capping material can be selected from the cathode active materials described herein.
  • any means for enabling the coating material to stably coat the surface of the core can be used.
  • the mechanofusion coating can be performed by using a mechanical fusion machine, so that the coating material can be coated on the surface of the core.
  • the core is a positive electrode lithium supplement material
  • the cladding material is a positive electrode active material.
  • the intermolecular force can be used between the positive electrode active material and the positive electrode lithium supplement material to form a uniform and firm coating bond.
  • high-speed fusion can be performed at a rotational speed of 200 rpm (revolution per minute) to 1000 rpm for 1 h to 10 h, so that the positive electrode active material is coated on the surface of the positive electrode lithium supplement material to obtain a composite positive electrode material.
  • the rotational speed is 300rpm to 800rpm.
  • the fusion time is 2h-6h. Fusion can be performed at room temperature, eg 25°C.
  • the cathode lithium supplement material or the cathode active material also has the D v 50 described in this paper, the fusion coating process can also be improved, the agglomeration phenomenon of the cathode active material can be reduced, and a uniform and firm coating effect can be obtained.
  • the preparation method of the present application also has the advantages of simple process and simple operation.
  • the present application also provides a secondary battery, which includes a positive electrode plate, and the positive electrode plate includes any one or several composite positive electrode materials of the present application.
  • the secondary battery of the present application can simultaneously take into account higher initial charge-discharge capacity, higher energy density and longer cycle life.
  • the secondary battery also includes a negative electrode tab and an electrolyte.
  • 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 electrode and the negative electrode.
  • the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector, the positive electrode film layer includes an active material, and the active material includes any one or several composite positive electrode materials of the present application.
  • the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is laminated on either or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be made of a material with good electrical conductivity and mechanical strength.
  • the positive electrode current collector may use aluminum foil.
  • the positive electrode film layer usually contains an active material and optionally a binder and optionally a conductive agent, and is usually coated with a positive electrode slurry, dried and cold-pressed.
  • the positive electrode slurry is usually formed by dispersing the active material and optionally a conductive agent and optionally a binder and the like in a solvent and stirring uniformly.
  • the solvent may be N-methylpyrrolidone (NMP).
  • the active material may further include other active materials that can be used for the positive electrode of a secondary battery.
  • Other active materials may include, for example, layered lithium transition metal oxides, olivine-structured lithium-containing phosphates, and one or more of their modified compounds, and, for example, include lithium nickel cobalt manganese oxides, lithium nickel cobalt One or more of aluminum oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium iron vanadium phosphate, and their modified compounds .
  • the positive electrode film layer may contain 70 wt % to 97 wt % of the active material.
  • the weight ratio of the active material in the positive electrode film layer is 85%-97%, 90%-97%, or 95%-97%.
  • the energy density and cycle life of the secondary battery can be further improved by adjusting the proportion of active materials in the cathode film layer.
  • the binder can stably bind the positive electrode active material and optionally the conductive agent to the positive electrode current collector.
  • the positive electrode film layer may contain 1 wt % to 25 wt % of the binder.
  • the weight proportion of the binder in the positive electrode film layer is 1% to 10%, 1% to 5%, or 2% to 5%.
  • the binder of the positive electrode film layer may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoroethylene
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoroethylene
  • fluoropropylene-tetrafluoroethylene terpolymer tetrafluoroethylene-hexafluoropropylene copolymer, and modified polymers thereof.
  • the conductive agent can improve the electronic conductivity of the positive electrode film layer.
  • the positive electrode film layer may contain 2 wt % to 20 wt % of the conductive agent.
  • the weight proportion of the conductive agent in the positive electrode film layer is 2% to 10%, or 2% to 5%.
  • the conductive agent of the positive electrode film layer may include one or one of superconducting carbon, carbon black (such as Super P, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. several.
  • composition or parameters of each positive electrode film layer given in this application all refer to the composition or parameter range of the positive electrode current collector single film layer.
  • the composition or parameter of the positive electrode film layer on any one of the surfaces satisfies the present application, that is, it is considered to fall within the protection scope of the present application.
  • the negative electrode sheet of the present application 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 current collector has two surfaces opposite in its thickness direction, and the negative electrode film layer is laminated on either or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector can be made of materials with good electrical conductivity and mechanical strength, which can conduct electricity and collect current.
  • the negative electrode current collector may use copper foil.
  • the negative electrode film layer usually contains the negative electrode active material and optionally a binder, optionally a conductive agent and other optional auxiliary agents. It is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optionally a conductive agent, optionally a binder, optionally an auxiliary agent, etc. in a solvent and stirring uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the negative active material may include one or more of artificial graphite, natural graphite, silicon-based materials, and tin-based materials.
  • the negative electrode active material includes one or more of artificial graphite and natural graphite.
  • the negative active material includes artificial graphite.
  • the conductive agent may include one or more of superconducting carbon, carbon black (eg, Super P, acetylene black, Ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • carbon black eg, Super P, acetylene black, Ketjen black, etc.
  • carbon dots carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may include one or one of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). several.
  • SBR styrene-butadiene rubber
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • other optional adjuvants are, for example, thickeners (eg, sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the type of electrolyte in this application which can be selected according to requirements.
  • the electrolyte can be selected from electrolytes.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonate) Lithium Imide), LiTFSI (Lithium Bistrifluoromethanesulfonimide), LiTFS (Lithium Trifluoromethanesulfonate), LiDFOB (Lithium Difluorooxalate Borate), LiBOB (Lithium Dioxalate Borate), LiPO 2 F 2 (Lithium difluorophosphate), one or more of LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl s
  • EC
  • the electrolyte also optionally includes additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance of the battery, such as additives to improve battery overcharge performance, additives to improve battery high temperature performance, and additives to improve battery low temperature performance. additives, etc.
  • the separator is arranged between the positive pole piece and the negative pole piece, and plays the role of isolation.
  • the type of separator for the secondary battery of the present application is not particularly limited, and any well-known porous structure separator for secondary batteries can be selected.
  • the release film can be selected from a glass fiber film, a non-woven film, a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multilayer composite film comprising one or more of them. species or several.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly by a lamination process or a winding process, so that the separator is placed between the positive pole piece and the negative pole piece to isolate the electrode assembly; the electrode assembly is placed in the outer package , the electrolyte solution is injected and sealed to obtain a secondary battery.
  • the outer packaging of the secondary battery is used to encapsulate the electrode assembly and electrolyte.
  • the outer packaging 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 package of the secondary battery may also be a soft package, such as a pouch-type soft package.
  • the material of the soft bag may be plastic, for example, may include one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • FIG. 3 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a housing 51 and a cover 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 plate are enclosed to form a accommodating cavity.
  • the housing 51 has an opening that communicates with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity.
  • the electrode assembly 52 is packaged in the receiving cavity.
  • the electrolyte solution is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 may be one or several, and may be adjusted according to requirements.
  • the secondary batteries can be assembled into a battery module, and 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. 5 shows the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed with fasteners.
  • the battery module 4 may further include a housing having an accommodating space in which the 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 included 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 case and a plurality of battery modules 4 provided in the battery case.
  • 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 .
  • the plurality of battery modules 4 may be arranged in the battery case in any manner.
  • the present application also provides a device comprising at least one of the secondary batteries, battery modules, or battery packs described in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the device, or as an energy storage unit for the device.
  • the device may be, but is not limited to, mobile devices (eg, cell phones, laptops, etc.), electric vehicles (eg, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf balls) vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Figure 8 is an apparatus as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack or a battery module can be employed.
  • the device may be a mobile phone, a tablet computer, a laptop computer, and the like.
  • the device is generally required to be thin and light, and a secondary battery can be used as a power source.
  • the positive electrode lithium supplement material is Li 2 Cu 0.6 Ni 0.4 O 2 , and the median particle size D v 50 is 15 ⁇ m.
  • the positive active material was LiFePO 4 (lithium iron phosphate, LFP), and the median particle size D v 50 was 1 ⁇ m.
  • Use a mechanical fusion machine for high-speed mechanical fusion coating mix the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 and the positive electrode active material LFP at a mass ratio of 1:35, and fuse at a high speed at 400 rpm for 4 hours to coat the LFP.
  • a composite positive electrode material was obtained on the outer surface of Li 2 Cu 0.6 Ni 0.4 O 2 .
  • the composite positive electrode material prepared above, conductive agent carbon black (Super P), and binder PVDF were dispersed in solvent NMP according to a mass ratio of 97:2:1, fully stirred and uniformly mixed to obtain a positive electrode slurry.
  • the positive electrode slurry is coated on two opposite surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode pole piece is obtained.
  • the areal density of the positive electrode film layer was 17.5 mg/cm 2
  • the compaction density was 2.35 g/cm 3 .
  • the negative active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC-Na) were prepared in a mass ratio of 96:1.5:1.5:1.0 Disperse in solvent deionized water, stir and mix evenly to obtain negative electrode slurry.
  • the negative electrode slurry is coated on two opposite surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode pole piece is obtained.
  • the areal density of the negative electrode film layer was 8.0 mg/cm 2
  • the compaction density was 1.65 g/cm 3 .
  • Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are uniformly mixed in a mass ratio of 30:70 to obtain an organic solvent; then lithium salt LiPF 6 is dissolved in the above-mentioned organic solvent, and uniformly mixed to obtain an electrolyte, wherein The concentration of LiPF 6 was 1 mol/L.
  • the positive pole piece, the polyethylene (PE) porous separator, and the negative pole piece are stacked in sequence, and then wound to obtain an electrode assembly; the electrode assembly is put into an outer package, injected with an electrolyte, and packaged to obtain a secondary battery.
  • PE polyethylene
  • the preparation of the secondary battery was similar to that of Example 1, except that the relevant parameters in the preparation of the composite cathode material were adjusted, as shown in Table 1; and,
  • LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) was used as the positive electrode active material; the areal density of the positive electrode film layer was 19.5 mg/cm 2 , and the compaction density was 3.4 g/cm 3 ; the areal density of the negative electrode film layer is 10.8 mg/cm 2 , and the compaction density is 1.65 g/cm 3 ;
  • the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 was mixed with the positive electrode active material LFP in a mass ratio of 1:15, and the resulting mixed material was mixed with the conductive agent Super P and the binder PVDF in a mass ratio of 97:2.
  • 1 is dispersed in NMP to prepare positive electrode slurry;
  • Li 2 Cu 0.6 Ni 0.4 O 2 /Al 2 O 3 (wherein the Al 2 O 3 content is 2wt%) obtained by coating the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 with alumina particles,
  • the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 /Al 2 O 3 and the positive electrode active material LFP are mixed in a mass ratio of 1:15, and the resulting mixed material, the conductive agent Super P and the binder PVDF are in a mass ratio of 97: 2:1 is dispersed in NMP to prepare positive electrode slurry;
  • the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 was mixed with the positive electrode active material NCM811 in a mass ratio of 1:20, and the resulting mixed material was mixed with the conductive agent Super P and the binder PVDF in a mass ratio of 97:2. : 1 is dispersed in NMP to prepare positive electrode slurry;
  • Li 2 Cu 0.6 Ni 0.4 O 2 /Al 2 O 3 (wherein the Al 2 O 3 content is 2wt%) was used as the positive electrode lithium supplement material, and the positive electrode lithium supplement material Li 2 Cu 0.6 Ni 0.4 O 2 /Al 2 O3 and the positive active material NCM811 were mixed in a mass ratio of 1:20, and the resulting mixed material, the conductive agent Super P and the binder PVDF were dispersed in NMP in a mass ratio of 97:2:1 to prepare a positive electrode slurry.
  • the first charging capacity in grams (mAh/g) the first cycle charging capacity / the mass of the composite cathode material contained in the battery
  • the first discharge gram capacity (mAh/g) the first cycle discharge capacity / the mass of the composite cathode material contained in the battery
  • the capacity retention rate (%) of the secondary battery at the Nth cycle the discharge capacity of the Nth cycle/the discharge capacity of the first cycle ⁇ 100%
  • the charge-discharge voltage range of the secondary battery is 2.5V-3.65V; when the positive electrode active material is NCM811, the charge-discharge voltage range of the secondary battery is 2.8V-4.25V.
  • the mass ratio in Table 1 is the mass ratio of the positive electrode lithium supplement material to the positive electrode active material.
  • the composite positive electrode material of the present application can obtain higher initial charge-discharge capacity, energy density and cycle life of the secondary battery by coating the surface of the lithium-rich metal oxide with the positive electrode active material.

Abstract

本申请提供一种复合正极材料、其制备方法、正极极片、二次电池及包含该二次电池的电池模块、电池包和装置。复合正极材料包括核和覆盖在核的至少一部分表面的包覆层，所述核包括正极补锂材料，所述正极补锂材料包括富锂金属氧化物，所述包覆层包括正极活性材料。

Description

复合正极材料、其制备方法、正极极片、二次电池及包含该二次电池的电池模块、电池包和装置 技术领域
本申请属于储能装置技术领域，具体涉及一种复合正极材料、其制备方法、正极极片、二次电池及包含该二次电池的电池模块、电池包和装置。
背景技术
近年来，随着二次电池在各类电子产品和新能源汽车等产业的应用及推广，其能量密度受到越来越多的关注。但是，二次电池在首次充放电过程中，负极不可避免的形成SEI(solid electrolyte interface，固体电解质界面)膜，造成活性离子消耗，由此导致的不可逆容量损失难以消除，给二次电池能量密度的提升带来挑战。
发明内容
本申请第一方面提供一种复合正极材料，其包括核和覆盖在核的至少一部分表面的包覆层，其中，核包括正极补锂材料，正极补锂材料包括富锂金属氧化物；包覆层包括正极活性材料。
本申请通过将正极活性材料对正极补锂材料进行表面包覆，能起到隔绝外界环境的作用，提高材料的稳定性，保证材料的纯度和补锂性能发挥，同时正极活性材料包覆层是良好的锂离子导体，从而能大幅度提高补锂效率。因此，采用本申请的复合正极材料能有效弥补电池首次充放电过程中损失的活性锂，能提升电池的首次充放电容量，从而能提高能量密度。进一步地，采用正极活性材料包覆正极补锂材料的形式可以不额外引入非活性物质，从而有利于使电池获得更高的能量密度。进一步地，采用本申请的复合正极材料，还显著延长了电池的循环寿命。
在本申请的任意实施方式中，复合正极材料中，正极活性材料以独立的颗粒形态分布于核的表面。复合正极材料满足上述条件，采用其的电池能获得较高的能量密度和循环性能。
在本申请的任意实施方式中，复合正极材料中，正极补锂材料与正极活性材料的质量比为1:2～1:35，可选地为1:5～1:30，进一步可选地为1:10～1:20。正极补锂材料与正极活性材料的质量比在所述范围内，能使电池获得更高的能量密度和循环性能。
在本申请的任意实施方式中，正极补锂材料的中值粒径D v50为2μm～35μm，可选地为5μm～30μm，进一步可选地为15μm～25μm。正极补锂材料的D v50在适当范围内，能提升正极补锂材料的容量利用率，使电池的能量密度和循环性能进一步提高。
在本申请的任意实施方式中，正极活性材料的中值粒径D v50为0.1μm～15μm，可 选地为0.2μm～10μm，进一步可选地为0.5μm～6μm。正极活性材料的D v50在适当范围内，能进一步提高电池的能量密度和循环性能。
在本申请的任意实施方式中，富锂金属氧化物可选自Li 2M 1O 2、Li 2M 2O 3、Li 3M 3O 4、Li 5M 4O 4、Li 6M 5O 4中的一种或几种，其中，M 1包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu中的一种或几种，M 2包括Mn、Sn、Mo、Ru、Ir中的一种或几种，M 3包括V、Nb、Cr、Mo中的一种或几种，M 4包括Fe、Cr、V、Mo中的一种或几种，M 5包括Co、V、Cr、Mo中的一种或几种，并且富锂金属氧化物中除Li外的每种金属元素的平均价态均低于其自身的最高氧化价态。
在本申请的任意实施方式中，富锂金属氧化物可选自Li 3VO 4、Li 2MnO 2、Li 3NbO 4、Li 5FeO 4、Li 6CoO 4、Li 2NiO 2、Li 2CuO 2和Li 2Cu x1Ni 1-x1M y1O 2中的一种或几种，其中0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.2≤x1≤0.8。进一步可选地，0.5≤x1≤0.7。
在本申请的任意实施方式中，正极活性材料可选自层状锂过渡金属氧化物、尖晶石结构的锂金属氧化物和聚阴离子型正极材料中的一种或几种。可选地，层状锂过渡金属氧化物选自LiCoO 2、LiNiO 2、LiMnO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2以及它们的改性材料中的一种或几种，其中，0＜a＜1，0＜b＜1，0＜c＜1，a+b+c＝1，0＜α＜1，0＜β＜1，0＜γ＜1，α+β+γ＝1。可选地，尖晶石结构的锂金属氧化物选自LiMn 2O 4、LiNi 0.5Mn 1.5O 4中的一种或几种。可选地，聚阴离子型正极材料选自LiFePO 4、LiMnPO 4、LiCoPO 4、LiNiPO 4、Li 3V 2(PO 4) 3、LiFe yMn 1-yPO 4以及它们的改性材料中的一种或几种，其中0＜y＜1，可选地0.2≤y≤0.8。
在本申请的任意实施方式中，正极活性材料可选自LiFePO 4、LiMnPO 4、Li 3V 2(PO 4) 3以及它们的改性材料中的一种或几种。
在本申请的任意实施方式中，正极活性材料的充电截止电压为4.2V～5.2V(vs.Li/Li +)，富锂金属氧化物可选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 3VO 4、Li 3NbO 4中的一种或几种，其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.1≤x1≤0.9。进一步可选地，0.2≤x1≤0.8。可选地，正极活性材料选自LiCoO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、LiMn 2O 4、LiNi 0.5Mn 1.5O 4、LiCoPO 4、LiNiPO 4以及它们的改性材料中的一种或几种，其中，0＜a＜1，0＜b＜1，0＜c＜1，a+b+c＝1，0＜α＜1，0＜β＜1，0＜γ＜1，α+β+γ＝1。
可选地，正极活性材料的中值粒径D v50为1μm～15μm，可选为2μm～10μm，进一步可选地为4μm～6μm。正极活性材料的D v50在上述范围内，能进一步提高电池的能量密度和循环性能。
在本申请的任意实施方式中，正极活性材料的充电截止电压为3.5V～4.2V(vs.Li/Li +)，富锂金属氧化物可选自Li 5FeO 4、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 2MnO 2中的一种或几种，其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.1≤x1≤0.9。进一步可选地，0.2≤x1≤0.8。可选地，正极活性材料选自LiFePO 4、Li 3V 2(PO 4) 3和LiFe yMn 1-yPO 4中的一种或几种，其中0＜y＜1。可选地，0.2≤y≤0.8。
可选地，正极活性材料的中值粒径D v50为0.1μm～3.5μm，可选为0.2μm～2μm， 进一步可选地为0.5μm～1.5μm。正极活性材料的D v50在上述范围内，能进一步提高电池的能量密度和循环性能。
本申请第二方面提供一种复合正极材料的制备方法，其包括以下步骤：
提供核，所述核包括正极补锂材料，所述正极补锂材料包括富锂金属氧化物；
提供包覆材料，所述包覆材料包括正极活性材料；
使包覆材料包覆核的至少一部分表面，得到复合正极材料。
本申请提供的制备方法中，将正极活性材料对正极补锂材料进行表面包覆，能起到隔绝外界环境的作用，提高材料的稳定性，保证材料的纯度和补锂性能发挥，同时正极活性材料包覆层是良好的锂离子导体，从而能大幅度提高补锂效率。因此，采用本申请制备方法得到的复合正极材料能有效弥补电池首次充放电过程中损失的活性锂，提升电池的首次充放电容量，从而提高能量密度。进一步地，采用正极活性材料包覆正极补锂材料的形式可以不额外引入非活性物质，从而使电池获得更高的能量密度。进一步地，采用本申请制备方法的复合正极材料，还显著延长了电池的循环寿命。
本申请第三方面提供一种正极极片，其包括正极集流体以及设置于正极集流体上的正极膜层，正极膜层包含本申请第一方面的复合正极材料、或根据本申请第二方面的制备方法得到的复合正极材料。
本申请的正极极片由于采用本申请的复合正极材料，因而能使采用其的二次电池同时兼顾较高的首次充放电容量、较高的能量密度和较长的循环性能。
在本申请的任意实施方式中，所述正极膜层还包含导电剂和粘结剂，其中，基于正极膜层的总重量，正极膜层中包含70重量％～97重量％的复合正极材料，2重量％～20重量％的导电剂和1重量％～25重量％的粘结剂。通过调控正极膜层中的复合正极材料占比，能进一步改善二次电池的能量密度和循环寿命。
本申请第四方面提供一种二次电池，其包括本申请第三方面的正极极片。
本申请的二次电池由于采用本申请的正极极片，因而能同时兼顾较高的首次充放电容量、较高的能量密度和较长的循环性能。
本申请第五方面提供一种电池模块，其包括本申请第四方面的二次电池。
本申请第六方面提供一种电池包，其包括本申请第五方面的电池模块。
本申请第七方面提供一种装置，其包括本申请第四方面的二次电池、本申请第五方面的电池模块、或本申请第六方面的电池包中的至少一种。
本申请的电池模块、电池包和装置包括本申请所述二次电池，因而至少具有与所述二次电池相同或类似的技术效果。
附图说明
图1是本申请一个实施例提供的复合正极材料的扫描电镜(SEM)图。
图2是本申请一个实施例提供的复合正极材料的断面的SEM图。
图3是二次电池的一实施方式的示意图。
图4是图3的分解图。
图5是电池模块的一实施方式的示意图。
图6是电池包的一实施方式的示意图。
图7是图6的分解图。
图8是二次电池用作电源的装置的一实施方式的示意图。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合具体实施例对本申请进行详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种或两种以上。
在本文的描述中，除非另有说明，术语“或”是包括性的。也就是说，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)。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实施例中，列举仅作为代表性组，不应解释为穷举。
为了满足二次电池在高能量密度方面的需求，可采用补锂技术来增加活性锂离子含量，补偿二次电池首次充放电过程中的活性锂损失。目前主要的、且技术成熟度较高的是负极补锂工艺，例如通过锂粉或锂箔在负极表面覆盖一层锂金属层。然而，金属锂的化学性质非常活泼，对环境和设备的要求均较高，在补锂过程中还会存在较高的安全风险。相比于负极补锂，正极补锂工艺具有较高的安全性，降低了对环境控制的要求。正极补锂工艺可以是在正极浆料中加入富锂过渡金属氧化物，制备富锂正极。电池化成或初始循环过程中，正极的富锂材料释放出锂，来补偿负极因形成SEI膜造成的不可逆活性锂损失。
然而，富锂过渡金属氧化物仍然存在活性较高，容易与环境中的水分和二氧化碳发生反应的问题，降低补锂效果，而且反应引入的杂质还会降低电池的能量密度。发明人进一步发现，采用碳材料或金属氧化物(例如Al 2O 3、TiO 2、ZrO 2等)包覆富锂过渡金属氧化物，能隔绝外界环境，避免富锂材料与空气中的水和二氧化碳接触。但是，表面包覆层制备工艺复杂，尤其是引入非电化学活性的包覆层还降低了电池的能量密度。而且，常规包覆层由于不利于内部补锂材料的锂离子脱出，导致对电池循环寿命的改善有 限。
发明人经深入研究，提供一种利用具有电化学活性的包覆层，提高正极补锂材料稳定性的复合正极材料。基于此，根据本申请的复合正极材料包括核和覆盖在核的至少一部分表面的包覆层，核包括正极补锂材料，正极补锂材料包括富锂金属氧化物，包覆层包括正极活性材料。
具有电化学活性的包覆层是指包覆层具有良好的导离子性，其能在电池充放电过程中提供良好的锂离子脱嵌通道。因此，在电池充电过程中，包覆层能够为所包覆的正极补锂材料提供良好的锂离子脱出通道。正极活性材料是指在电池充放电过程中，正极极片(电池中电位较高的电极片)中参与活性离子嵌入和脱出的材料。正极补锂材料通常布置在正极，并且在电池首次或初始充电过程中能提供额外的活性锂。正极补锂材料可以用来补偿负极因形成SEI膜造成的不可逆活性锂损失。
正极活性材料通常对空气中的水分和二氧化碳具有良好的稳定性。本申请通过将正极活性材料对正极补锂材料进行表面包覆，能起到隔绝外界环境的作用，避免正极补锂材料与空气中的水分和二氧化碳直接接触，减少表面副反应，从而提高材料的稳定性，保证材料的纯度和补锂性能发挥。同时，正极活性材料包覆层是良好的锂离子导体，有利于补锂材料的脱锂过程，大幅度提高补锂效率。因此，采用本申请的复合正极材料有效地弥补了电池首次充放电过程中损失的活性锂，提升了电池的首次充放电容量，从而能使电池获得较高的能量密度。进一步地，采用正极活性材料包覆正极补锂材料的形式可以不额外引入非活性物质，从而有助于使电池获得更高的能量密度。
采用本申请的复合正极材料还可以显著提升电池的循环寿命。不期望受任何理论限制：复合正极材料提高了正极补锂材料的容量利用率，使其释放出更多的活性锂。过量的活性锂嵌入负极中，使负极活性材料处于一定的嵌锂状态，可一定程度上缓解负极活性材料的体积变化，由此能减小负极活性材料破裂或掉粉的风险，同时使负极极片保持良好的电解液浸润性和保液率。并且，这部分活性锂还能在循环的中后期用来弥补电池循环过程中的活性锂损失。因此，采用本申请的复合正极材料可具有进一步延长的循环寿命。
在一些实施方式中，复合正极材料中，正极活性材料以独立的颗粒形态分布于核的表面。可以采用扫描电镜(例如SIGMA300)观察复合正极材料的形貌。图1是作为一个示例的复合正极材料的SEM图片。图2是作为一个示例的复合正极材料的断面的SEM图片。复合正极材料的断面可采用离子抛光仪(例如氩离子截面抛光仪，如IB-19500CP)获得。由图片可以看出，复合正极材料为核颗粒表面包覆着大量的正极活性材料颗粒。
本申请中，正极补锂材料以独立的颗粒形态分布于正极活性材料表面时，复合正极材料表面的正极活性材料可以形成有效的物理阻隔，避免正极补锂材料与电解液的直接接触，减少副反应的发生，从而使正极补锂材料的电化学稳定性得到进一步地提升。同时，颗粒形态的正极活性材料还可以更好地发挥自身的高容量特性。因此，采用该复合正极材料的电池能获得较高的能量密度和循环性能。
可选地，核与包覆层之间可以通过物理键合(例如分子间作用力等)或化学键合实现结合。在一些实施例中，在复合正极材料中，通过正极补锂材料颗粒与正极活性材 料之间的分子间作用力，实现核与包覆层的键合结合。本申请中，正极补锂材料与正极活性材料之间通过分子间的作用力进行键合，从而使正极活性材料颗粒紧密地附着在正极补锂材料的表面，因此使得复合正极材料的微观结构稳定性以及电化学稳定性较高。因此，采用该复合正极材料的电池能获得良好的长期循环性能。
可选地，正极活性材料颗粒在正极补锂材料表面的包覆率≥60％。进一步可选地为≥70％、≥80％、≥90％、≥95％、或100％。本申请中，正极活性材料颗粒在正极补锂材料表面的包覆率在上述范围内时，可以进一步降低复合正极材料对外界环境(尤其湿度)的敏感度，有效改善复合正极材料在正极浆料制备过程中的凝胶问题，提高复合正极材料在电池应用过程的加工性。
在一些实施方式中，正极补锂材料的中值粒径D v50可以为2μm～35μm。可选地，正极补锂材料的D v50为4μm～30μm，进一步可选地为5μm～30μm，5μm～25μm，5μm～20μm，10μm～25μm，10μm～20μm，12μm～20μm，15μm～25μm，或15μm～20μm。正极补锂材料的D v50在适当范围内，能改善锂离子在颗粒内部的传输过程，降低离子迁移阻抗，同时能减小材料与电解液的接触面积，减少电解液与材料之间的副反应，从而能提升正极补锂材料的利用率，使电池的能量密度和循环性能进一步提高。
在一些实施方式中，所述正极活性材料的中值粒径D v50为0.1μm～15μm。可选地，正极活性材料的D v50为0.2μm～10μm，进一步可选地为0.2μm～2μm，0.2μm～5μm，0.5μm～1.5μm，0.8μm～1.2μm，0.5μm～6μm，1μm～15μm，2μm～10μm，3μm～8μm，1μm～5μm，或1μm～1.5μm。正极活性材料的D v50在适当范围内，能提高正极活性材料在正极补锂材料表面的分散均匀性，减少团聚现象。在正极补锂材料表面形成的包覆层具有更好的隔绝保护作用，进一步提高材料稳定性，从而进一步提高电池的能量密度。正极活性材料附着在正极补锂材料表面，还可以使正极补锂材料起到稳定正极活性材料的作用，大幅度缓解粒径较小的正极活性材料在电池循环过程中容易发生团聚的问题，由此能进一步提高电池的循环性能。使正极活性材料附着在正极补锂材料表面形成较大的颗粒，还能改善正极浆料的加工性能，减少物理凝胶现象，从而能制备得到整体一致性较好的正极极片，实现提升电池的整体性能。另外，正极活性材料的粒径适当，还能提高活性离子在活性材料颗粒中的传输性能，有利于进一步提高电池的循环性能。
在一些可选的实施方式中，复合正极材料的中值粒径D v50为2μm～40μm，可选地为3μm～38μm，3μm～30μm，5μm～25μm，8μm～40μm，10μm～35μm，10μm～25μm，15μm～30μm，或10μm～20μm。本申请中，当复合正极材料的中值粒径D v50在上述范围内时，有利于提高正极极片的压实密度，从而有利于提升电池的能量密度。另外，正极极片内颗粒间能够在紧密接触的同时，还形成便于电解液浸润的孔隙结构，因此还能使电池获得较高的循环性能。
在本申请中，正极活性材料、正极补锂材料、复合正极材料的中值粒径(又称体积平均粒径)D v50为本领域公知的含义，可使用本领域公知的方法测定。例如，可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)测定。其中，D v50表示材料累计体积分布百分数达到50％时所对应的粒径。
在一些实施方式中，复合正极材料中，正极补锂材料与正极活性材料的质量比可 以为1:2～1:35。正极补锂材料与正极活性材料的质量比在适当范围内，既可使正极补锂材料表面形成合适厚度的正极活性材料包覆层，有效提高材料的稳定性，又保证包覆层内的正极补锂材料能充分脱锂，确保其补锂性能的高效发挥。并且，复合正极材料中包含充足的正极活性材料，能使正极具有较多的锂位进行锂离子的往复脱嵌，提升电池的可逆容量。因此，采用该复合正极材料的电池能获得较高的能量密度和循环性能。
可选地，复合正极材料中正极补锂材料与正极活性材料的质量比为1:5～1:30，进一步可选地为1:5～1:25，1:10～1:20，1:12～1:18，或1:15～1:20。正极补锂材料与正极活性材料的质量比在所述范围内，能使电池具有更高的能量密度和更长的循环寿命。
在本申请中，复合正极材料中正极补锂材料与正极活性材料的质量比可以采用本领域公知的测试方法进行测试。例如，ICP(电感耦合等离子体)原子发射光谱法。测试可以在电感耦合等离子体原子发射光谱仪(例如美国Thermo Fisher Scientific公司的ICAP7400)中进行。示例性测试方法如下：取2g复合正极材料加入酸溶液(例如王水)中消解，消解可以在搅拌(例如机械搅拌或微波搅拌等)下进行，消解时间可以为30min；将消解后的溶液加入ICAP7400光谱仪中，定量分析复合正极材料中的化学组成元素。通过每种元素的定量从而确定含有该元素的化合物质量，最终计算正极活性材料和正极补锂材料的质量比。
需要说明的是，测试样品可直接取复合正极材料，或从二次电池的正极极片中取样进行测试。其中，从二次电池中获取复合正极材料的示例性方法如下：
(1)将二次电池做放电处理(为了安全起见，一般使电池处于满放状态)；将电池拆卸后取出正极极片，使用碳酸二甲酯(DMC)将正极极片浸泡一定时间(例如2小时)；然后将正极极片取出并在一定温度和时间下干燥处理(例如80℃，6h)，干燥后取出正极极片。
(2)将步骤(1)干燥后的正极极片在一定温度及时间下烘烤(例如120℃，6h)，在烘烤后的正极极片中任选一区域，对复合正极材料取样。例如可以选用刀片刮粉取样。
(3)将步骤(2)收集到的复合正极材料做过筛处理(例如用200目的筛网过筛)，最终得到可以用于测试本申请所述各材料参数的复合正极材料样品。
在一些实施方式中，富锂金属氧化物可选自Li 2M 1O 2、Li 2M 2O 3、Li 3M 3O 4、Li 5M 4O 4、Li 6M 5O 4中的一种或几种。富锂金属氧化物中除Li外的每种金属元素的价态均低于其自身的最高氧化价态。在Li 2M 1O 2中，M 1可包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu中的一种或几种。可选地，M 1包括Ni、Co、Mn、Cu中的一种或几种。可选地，M 1包括Ni、Cu、Mn中的一种或几种。作为示例，Li 2M 1O 2可包括Li 2NiO 2、Li 2MnO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 2Co x2Mn 1-x2O 2中的一种或几种。可选地，Li 2M 1O 2包括Li 2NiO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。可选地，Li 2M 1O 2包括Li 2Cu x1Ni 1-x1-y1M y1O 2。其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。0＜x2＜1。可选地，0.1≤x1≤0.9，0.2≤x1≤0.8，0.4≤x1≤0.6，或0.5≤x1≤0.7。可选地，0.5≤x2≤0.8。
在Li 2M 2O 3中，M 2可包括Mn、Sn、Mo、Ru、Ir中的一种或几种。可选地，M 2包括Mn、Mo、Sn中的一种或几种。作为示例，Li 2M 2O 3可包括Li 2MnO 3、Li 2MoO 3中的一 种或几种。
在Li 3M 3O 4中，M 3可包括V、Nb、Cr、Mo中的一种或几种。可选地，M 3包括V、Nb、Mo中的一种或几种。作为示例，Li 3M 3O 4可包括Li 3VO 4、Li 3NbO 4、Li 3MoO 4中的一种或几种。可选地，Li 3M 3O 4包括Li 3VO 4、Li 3NbO 4中的一种或几种。
在Li 5M 4O 4中，M 4可包括Fe、Cr、V、Mo中的一种或几种。可选地，M 4包括Fe、Cr、V中的一种或几种。作为示例，Li 5M 4O 4可包括Li 5FeO 4、Li 5CrO 4、Li 5VO 4中的一种或几种。可选地，Li 5M 4O 4包括Li 5FeO 4。
在Li 6M 5O 4中，M 5可包括Co、V、Cr、Mo中的一种或几种。可选地，M 5包括Co、V、Cr中的一种或几种。作为示例，Li 6M 5O 4可包括Li 6CoO 4、Li 6VO 4、Li 6CrO 4中的一种或几种。可选地，Li 6M 5O 4包括Li 6CoO 4。
在一些实施方式中，富锂金属氧化物可包括Li 2M 1O 2、Li 2M 2O 3、Li 5M 4O 4、Li 6M 5O 4中的一种或几种。可选地，富锂金属氧化物可包括Li 2M 1O 2、Li 5M 4O 4、Li 6M 5O 4中的一种或几种。其中，M 1、M 2、M 4、M 5分别如本文所定义。
在一些实施例中，富锂金属氧化物可包括Li 3VO 4、Li 2MnO 2、Li 3NbO 4、Li 5FeO 4、Li 6CoO 4、Li 2NiO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。可选地，富锂金属氧化物包括Li 5FeO 4、Li 6CoO 4、Li 2NiO 2、Li 2CuO 2和Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。进一步可选地，富锂金属氧化物包括Li 5FeO 4、Li 6CoO 4、Li 2CuO 2、Li 2Cu x1Ni 1- x1-y1M y1O 2中的一种或几种。其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.1≤x1≤0.9。进一步可选地，0.2≤x1≤0.8，0.4≤x1≤0.6，或0.5≤x1≤0.7。
在一些实施方式中，正极活性材料可选自层状锂过渡金属氧化物、尖晶石结构的锂金属氧化物和聚阴离子型正极材料中的一种或几种。
在一些实施例中，正极活性材料可包括层状锂过渡金属氧化物。可选地，层状锂过渡金属氧化物选自LiCoO 2、LiNiO 2、LiMnO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、以及它们的改性材料中的一种或几种。可选地，层状锂过渡金属氧化物包括LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、以及它们的改性材料中的一种或几种。其中，0＜a＜1，0＜b＜1，0＜c＜1，a+b+c＝1。可选地，0.5≤a≤0.9，或0.6≤a≤0.85。0＜α＜1，0＜β＜1，0＜γ＜1，α+β+γ＝1。可选地，0.5≤α≤0.9，或0.6≤α≤0.85。
作为示例，层状锂过渡金属氧化物可包括LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2中的一种或几种。
在本申请中，改性材料中的改性可以是掺杂改性或包覆改性。
在一些实施例中，正极活性材料可包括尖晶石结构的锂金属氧化物，例如锂锰氧化物、锂镍锰氧化物等。具体的示例如，LiMn 2O 4、LiNi 0.5Mn 1.5O 4、以及它们的改性材料中的一种或几种。所述改性材料中的改性可以是掺杂改性或包覆改性。
在一些实施例中，正极活性材料可包括聚阴离子型正极材料。聚阴离子型正极材料是包含锂、过渡金属和四面体或八面体阴离子结构单元(XO z) t-的化合物，其中X可选自P、S、As、Mo、W。例如，X是P。(XO z) t-可以是(PO 4) ﹣。聚阴离子型正极材料的晶体结构可以是橄榄石型或NASICON型。可选地，聚阴离子型正极材料可包括LiFePO 4 (LFP)、LiMnPO 4、LiCoPO 4、LiNiPO 4、Li 3V 2(PO 4) 3、LiFe yMn 1-yPO 4、以及它们的改性材料中的一种或几种，其中0＜y＜1。可选地，0.2≤y≤0.8。进一步可选地，正极活性材料可包括LiFePO 4、LiMnPO 4、Li 3V 2(PO 4) 3、以及它们的改性材料中的一种或几种。作为示例，正极活性材料包括LiFePO 4。
发明人经进一步研究发现，当正极活性材料和正极补锂材料进行合理匹配时，能更大限度地发挥补锂材料的容量，使电池获得更高的能量密度。进一步地，电池还能具有更好的循环性能。
在一些实施方式中，正极活性材料的充电截止电压为4.2V～5.2V(vs.Li/Li +)，富锂金属氧化物可选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 3VO 4、Li 3NbO 4中的一种或几种。可选地，富锂金属氧化物可选自Li 5FeO 4、Li 6CoO 4、Li 2NiO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。进一步可选地，富锂金属氧化物可选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。更进一步可选地，富锂金属氧化物可选自Li 6CoO 4、Li 2NiO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。在一些实施例中，富锂金属氧化物包括或是Li 2Cu x1Ni 1-x1-y1M y1O 2。式中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.1≤x1≤0.9。进一步可选地，0.2≤x1≤0.8，0.4≤x1≤0.6，或0.5≤x1≤0.7。
可选地，正极活性材料可选自LiCoO 2、LiNiO 2、LiMnO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、LiMn 2O 4、LiNi 0.5Mn 1.5O 4、LiMnPO 4、LiCoPO 4、LiNiPO 4以及它们的改性材料中的一种或几种，其中，a、b、c、α、β、γ分别如本文所定义。可选地，正极活性材料可包括LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、以及它们的改性材料中的一种或几种。可选地，正极活性材料可包括LiNi aCo bMn cO 2及其改性材料中的一种或几种。
在这些实施方式中，可选地，正极活性材料的中值粒径D v50为1μm～15μm。进一步可选地，正极活性材料的D v50为2μm～10μm，2μm～8μm，3μm～7μm，4μm～6μm，3μm～5μm，或4μm～7μm。正极活性材料的D v50在适当范围内，不仅能起到保护正极补锂材料的作用，而且能提高活性离子在颗粒中的传输性能，同时还能减少电解液在颗粒表面的副反应，从而能进一步提高电池的容量发挥和循环性能。
在另一些实施方式中，正极活性材料的充电截止电压为3.5V～4.2V(vs.Li/Li +)，富锂金属氧化物选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2CuO 2、Li 2Cu x1Ni 1-x1- y1M y1O 2、Li 2MnO 2中的一种或几种，其中0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种。可选地，0.2≤x1≤0.8；进一步可选地，0.5≤x1≤0.8，0.4≤x1≤0.6，或0.5≤x1≤0.7。可选地，富锂金属氧化物选自Li 5FeO 4、Li 2CuO 2、Li 2Cu x1Ni 1- x1-y1M y1O 2、Li 2MnO 2中的一种或几种。进一步可选地，富锂金属氧化物可选自Li 5FeO 4、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2中的一种或几种。
可选地，正极活性材料可选自LiFePO 4、Li 3V 2(PO 4) 3和LiFe yMn 1-yPO 4中的一种或几种，其中0＜y＜1。可选地，0.2≤y≤0.8。可选地，正极活性材料可选自LiFePO 4、LiFe yMn 1-yPO 4中的一种或几种。
在这些实施方式中，可选地，正极活性材料的中值粒径D v50为0.1μm～3.5μm。进一步可选地，正极活性材料的D v50为0.2μm～3μm，0.2μm～2μm，0.5μm～1.5μm，0.8μm～1.2μm，或1μm～1.5μm。正极活性材料的D v50在适当范围内，不仅能起到保护 正极补锂材料的作用，而且能改善正极活性材料的分散性能和正极浆料的加工性能，同时使得复合活性材料具有良好的活性离子传输性能，因此能进一步提高电池的容量发挥和循环性能。
本申请中，可选地，内核富锂金属氧化物与外层正极活性材料的充放电电压区间相近，这样可以保证正极活性材料和补锂剂富锂金属氧化物的容量均得到最大程度地发挥。
本申请还提供一种复合正极材料的制备方法，通过该制备方法能得到上述任意一种复合正极材料。
本申请提供的一种复合正极材料的制备方法包括以下步骤：提供核，所述核包括正极补锂材料，所述正极补锂材料包括富锂金属氧化物；提供包覆材料，所述包覆材料包括正极活性材料；使包覆材料包覆核的至少一部分表面，得到复合正极材料。
在制备方法中，核可选自本文所描述的富锂金属氧化物，并且包覆材料可选自本文所描述的正极活性材料。
在制备方法中，可采用任意能使包覆材料稳定地包覆在核表面的手段。作为示例，可采用机械融合机进行机械融合包覆，实现将包覆材料包覆在核表面。例如，核是正极补锂材料，包覆材料是正极活性材料。正极活性材料和正极补锂材料之间可通过分子间作用力，来形成均匀、牢固的包覆结合。
可选地，在机械融合包覆工序中，可以在200rpm(转每分)～1000rpm的转速下高速融合1h～10h，使正极活性材料包覆在正极补锂材料的表面，得到复合正极材料。可选地，转速为300rpm～800rpm。可选地，融合的时间为2h～6h。融合可以在室温下进行，例如25℃。
当正极补锂材料或正极活性材料还具有本文所述的D v50时，还能改善融合包覆过程，减少正极活性材料发生团聚现象，获得均匀牢固的包覆效果。
本申请的的制备方法还具有工艺简单，操作简便的优势。
可以理解的是，本申请的复合正极材料所描述的优选特征和优选方案，也适用于本申请的复合正极材料的制备方法中，并获得相应的有益效果。
本申请还提供一种二次电池，其包括正极极片，所述正极极片包括本申请任意一种或几种复合正极材料。本申请的二次电池能同时兼顾较高的首次充放电容量、较高的能量密度和较长的循环寿命。
二次电池还包括负极极片和电解质。在二次电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。
[正极极片]
本申请提供一种正极极片，其包括正极集流体以及设置于正极集流体上的正极膜层，正极膜层包含活性材料，活性材料包括本申请任意一种或几种复合正极材料。
作为示例，正极集流体具有在自身厚度方向相对的两个表面，正极膜层层合于正极集流体相对的两个表面的其中任意一者或两者上。
本申请的正极极片中，正极集流体可以采用具有良好导电性及机械强度的材质。作为示例，正极集流体可采用铝箔。
本申请的正极极片中，正极膜层通常包含活性材料以及可选地粘结剂和可选地导电剂，通常是由正极浆料涂布，并经干燥、冷压而成的。正极浆料通常是将活性材料以及可选地导电剂和可选地粘结剂等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)。
在本申请的正极极片中，除了本申请的复合正极材料，活性材料还可包含可用于二次电池正极的其它活性材料。其它活性材料例如可包括层状锂过渡金属氧化物、橄榄石结构的含锂磷酸盐、及它们的改性化合物中的一种或几种，再例如包括锂镍钴锰氧化物、锂镍钴铝氧化物、锂钴氧化物、锂镍氧化物、锂锰氧化物、磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒铁锂、及它们的改性化合物中的一种或几种。
在一些可选地实施方式中，基于正极膜层的总重量，正极膜层中可包含70重量％～97重量％的活性材料。可选地，活性材料在正极膜层中的重量占比为85％～97％，90％～97％，或95％～97％。通过调控正极膜层中的活性材料占比，能进一步改善二次电池的能量密度和循环寿命。
粘结剂能将正极活性材料及可选地导电剂稳定地粘结于正极集流体上。在一些可选地实施方式中，基于正极膜层的总重量，所述正极膜层中可包含1重量％～25重量％的粘结剂。可选地，粘结剂在正极膜层中的重量占比为1％～10％，1％～5％，或2％～5％。
在一些实施方式中，正极膜层的粘结剂可包括聚偏氟乙烯(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、以及它们的改性聚合物中的一种或几种。
导电剂能改善正极膜层的电子传导性能。在一些可选地实施方式中，基于正极膜层的总重量，所述正极膜层中可包含2重量％～20重量％的导电剂。可选地，导电剂在正极膜层中的重量占比为2％～10％，或2％～5％。
在一些实施方式中，正极膜层的导电剂可包括超导碳、炭黑(如Super P、乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
需要说明的是，本申请所给的各正极膜层的组成或参数均指正极集流体单面膜层的组成或参数范围。当正极膜层设置在正极集流体相对的两个表面上时，其中任意一个表面上的正极膜层的组成或参数满足本申请，即认为落入本申请的保护范围内。
[负极极片]
本申请的负极极片中包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层。
作为示例，负极集流体具有在自身厚度方向相对的两个表面，负极膜层层合于负极集流体相对的两个表面的其中任意一者或两者上。
负极集流体可以采用具有良好导电性及机械强度的材质，起导电和集流的作用。在一些实施例中，负极集流体可以采用铜箔。
本申请的负极极片中，负极膜层通常包含负极活性材料以及可选地粘结剂、可选地导电剂和其它可选助剂。其通常是由负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料以及可选地导电剂、可选地粘结剂、可选助剂 等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。
在一些实施方式中，负极活性材料可包括人造石墨、天然石墨、硅基材料和锡基材料中的一种或几种。可选地，负极活性材料包括人造石墨和天然石墨中的一种或几种。可选地，负极活性材料包括人造石墨。
在一些实施方式中，导电剂可包括超导碳、炭黑(例如Super P、乙炔黑、科琴黑等)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。
在一些实施方式中，粘结剂可包括丁苯橡胶(SBR)、水性丙烯酸树脂、聚乙烯醇(PVA)、海藻酸钠(SA)及羧甲基壳聚糖(CMCS)中的一种或几种。
在一些实施方式中，其它可选助剂例如是增稠剂(例如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
[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，电解质可以选自电解液。所述电解液包括电解质盐和溶剂。
在一些实施例中，电解质盐可选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
在一些实施例中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施例中，所述电解液中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，也可以包括正极成膜添加剂，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、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请的二次电池对隔离膜的种类没有特别的限制，可以选用任意公知的用于二次电池的多孔结构隔离膜。例如，隔离膜可选自玻璃纤维薄膜、无纺布薄膜、聚乙烯薄膜、聚丙烯薄膜、聚偏二氟乙烯薄膜、以及包含它们中的一种或两种以上的多层复合薄膜中的一种或几种。
正极极片、负极极片和隔离膜可经叠片工艺或卷绕工艺制成电极组件，使隔离膜处于正极极片与负极极片之间起到隔离的作用；将电极组件置于外包装中，注入电解液并封口，即可得到二次电池。
二次电池的外包装用于封装电极组件和电解质。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，如可包括聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
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3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，参照图4，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能够盖设于所述开口，以封闭所述容纳腔。电极组件52封装于所述容纳腔。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几个，可根据需求来调节。
在一些实施例中，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5是作为一个示例的电池模块4。参照图5，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6和图7是作为一个示例的电池包1。参照图6和图7，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能够盖设于下箱体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。
本申请还提供一种装置，所述装置包括本申请所述的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述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。
所述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8是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该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、和比值都是基于重量计，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
锂离子二次电池的制备：
复合正极材料的制备
正极补锂材料为Li 2Cu 0.6Ni 0.4O 2，中值粒径D v50为15μm。正极活性材料为LiFePO 4(磷酸铁锂，LFP)，中值粒径D v50为1μm。使用机械融合机进行高速机械融合包覆：将正极补锂材料Li 2Cu 0.6Ni 0.4O 2和正极活性材料LFP按质量比1:35混合，在400rpm的转速下高速融合4h，使LFP包覆在Li 2Cu 0.6Ni 0.4O 2的外表面，得到复合正极材料。
正极极片的制备
将上述制备的复合正极材料、导电剂炭黑(Super P)、粘结剂PVDF按照质量比97:2:1分散于溶剂NMP中，充分搅拌混合均匀，得到正极浆料。将正极浆料涂覆于正极集流体铝箔的相对两个表面，经烘干、冷压后，得到正极极片。其中，正极膜层的面密度为17.5mg/cm 2，压实密度为2.35g/cm 3。
负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)及增稠剂羧甲基纤维素钠(CMC-Na)按质量比96:1.5:1.5:1.0分散于溶剂去离子水中，搅拌混合均匀后，得到负极浆料。将负极浆料涂覆在负极集流体铜箔的相对两个表面，经烘干、冷压后，得到负极极片。其中，负极膜层的面密度为8.0mg/cm 2，压实密度为1.65g/cm 3。
电解液的制备
将碳酸亚乙酯(EC)和碳酸甲乙酯(EMC)按质量比30:70混合均匀，得到有机溶剂；再将锂盐LiPF 6溶解于上述有机溶剂中，混合均匀，得到电解液，其中LiPF 6的浓度为1mol/L。
二次电池的制备
将正极极片、聚乙烯(PE)多孔隔离膜、负极极片按顺序层叠好，然后卷绕得到电极组件；将电极组件装入外包装中，注入电解液并封装，得到二次电池。
实施例2～30及对比例1～6
二次电池的制备与实施例1类似，不同的是，调整复合正极材料的制备中的相关参数，详见表1；以及，
实施例26～30和对比例4～6中，正极活性材料采用LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)；正极膜层的面密度为19.5mg/cm 2，压实密度为3.4g/cm 3；负极膜层的面密度为10.8mg/cm 2，压实密度为1.65g/cm 3；
对比例1和4中无正极补锂；
对比例2中，将正极补锂材料Li 2Cu 0.6Ni 0.4O 2与正极活性材料LFP按质量比1:15混合，所得混合材料与导电剂Super P和粘结剂PVDF按质量比97:2:1分散于NMP中，制 备正极浆料；
对比例3中，正极补锂材料Li 2Cu 0.6Ni 0.4O 2采用氧化铝颗粒包覆后得到的Li 2Cu 0.6Ni 0.4O 2/Al 2O 3(其中Al 2O 3含量2wt％)，将正极补锂材料Li 2Cu 0.6Ni 0.4O 2/Al 2O 3和正极活性材料LFP按质量比为1:15混合，所得混合材料与导电剂Super P和粘结剂PVDF按质量比97:2:1分散于NMP中，制备正极浆料；
对比例5中，将正极补锂材料Li 2Cu 0.6Ni 0.4O 2与正极活性材料NCM811按质量比1:20混合，所得混合材料与导电剂Super P和粘结剂PVDF按质量比97:2:1分散于NMP中，制备正极浆料；
对比例6中，正极补锂材料采用Li 2Cu 0.6Ni 0.4O 2/Al 2O 3(其中Al 2O 3含量2wt％)，将正极补锂材料Li 2Cu 0.6Ni 0.4O 2/Al 2O 3和正极活性材料NCM811按质量比为1:20混合，所得混合材料与导电剂Super P和粘结剂PVDF按质量比97:2:1分散于NMP中，制备正极浆料。
二次电池的性能测试：
在25℃下，将二次电池以1C倍率恒流充电至上限截止电压，然后恒压充电至电流为0.05C，记录此时的充电容量，即为第1圈充电容量；再以1C恒流放电至下限截止电压，之后静置5min，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将电池按照上述方法进行充放电测试，记录每圈的放电容量，直至电池的容量保持率衰减为80％，此时的循环圈数即为循环寿命。
首次充电克容量(mAh/g)＝第1圈充电容量/电池所含复合正极材料的质量
首次放电克容量(mAh/g)＝第1圈放电容量/电池所含复合正极材料的质量
二次电池第N圈的容量保持率(％)＝第N圈放电容量/第1圈放电容量×100％
测试中，当正极活性材料为LFP时，二次电池的充放电电压范围为2.5V～3.65V；当正极活性材料为NCM811时，二次电池的充放电电压范围为2.8V～4.25V。
表1
Figure PCTCN2020131578-appb-000001
注：如无特别说明，表1中质量比是正极补锂材料与正极活性材料的质量比。
由表1的结果可知，本申请的复合正极材料通过将正极活性材料对富锂金属氧化物进行表面包覆，使二次电池获得较高的首次充放电容量、能量密度和循环寿命。
对比例1～6由于不符合上述条件，二次电池的首次充放电容量和能量密度及其循 环寿命均较低。
由实施例1～7的结果可以看出，当正极补锂材料和正极活性材料的配比在适当范围内时，能进一步提高二次电池的能量密度和循环寿命。
由实施例5、8～18的结果可以看出，当正极补锂材料或正极活性材料的粒径分布在适当范围内时，能进一步提高二次电池的能量密度和循环寿命。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (19)

  1. 一种复合正极材料，包括核和覆盖在所述核的至少一部分表面的包覆层，所述核包括正极补锂材料，所述正极补锂材料包括富锂金属氧化物，所述包覆层包括正极活性材料。
  2. 根据权利要求1所述的复合正极材料，其中，所述复合正极材料中，所述正极活性材料以独立的颗粒形态分布于所述核的表面；和/或，
    所述正极补锂材料与所述正极活性材料的质量比为1:2～1:35，可选地为1:5～1:30，进一步可选地为1:10～1:20。
  3. 根据权利要求1或2所述的复合正极材料，其中，所述正极补锂材料的中值粒径D v50为2μm～35μm，可选地为5μm～30μm，进一步可选地为15μm～25μm。
  4. 根据权利要求1-3任一项所述的复合正极材料，其中，所述正极活性材料的中值粒径D v50为0.1μm～15μm，可选为0.2μm～10μm，进一步可选地为0.5μm～6μm。
  5. 根据权利要求1-4任一项所述的复合正极材料，其中，所述富锂金属氧化物选自Li 2M 1O 2、Li 2M 2O 3、Li 3M 3O 4、Li 5M 4O 4、Li 6M 5O 4中的一种或几种，
    其中，
    M 1包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu中的一种或几种，
    M 2包括Mn、Sn、Mo、Ru、Ir中的一种或几种，
    M 3包括V、Nb、Cr、Mo中的一种或几种，
    M 4包括Fe、Cr、V、Mo中的一种或几种，
    M 5包括Co、V、Cr、Mo中的一种或几种，
    所述富锂金属氧化物中除Li外的每种金属元素的价态均低于其自身的最高氧化价态。
  6. 根据权利要求1-4任一项所述的复合正极材料，其中，所述富锂金属氧化物选自Li 3VO 4、Li 2MnO 2、Li 3NbO 4、Li 5FeO 4、Li 6CoO 4、Li 2NiO 2、Li 2CuO 2和Li 2Cu x1Ni 1-x1- y1M y1O 2中的一种或几种，其中0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种；可选地，0.2≤x1≤0.8。
  7. 根据权利要求1-6任一项所述的复合正极材料，其中，所述正极活性材料选自层状锂过渡金属氧化物、尖晶石结构的锂金属氧化物和聚阴离子型正极材料中的一种或几种；
    可选地，所述层状锂过渡金属氧化物选自LiCoO 2、LiNiO 2、LiMnO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2以及它们的改性材料中的一种或几种，其中，0＜a＜1，0＜b＜1，0＜c＜1，a+b+c＝1，0＜α＜1，0＜β＜1，0＜γ＜1，α+β+γ＝1；
    可选地，所述尖晶石结构的锂金属氧化物选自LiMn 2O 4、LiNi 0.5Mn 1.5O 4中的一种或几种；
    可选地，所述聚阴离子型正极材料选自LiFePO 4、LiMnPO 4、LiCoPO 4、LiNiPO 4、Li 3V 2(PO 4) 3、LiFe yMn 1-yPO 4以及它们的改性材料中的一种或几种，其中0＜y＜1；可选地，0.2≤y≤0.8。
  8. 根据权利要求1-6任一项所述的复合正极材料，其中，所述正极活性材料选自LiFePO 4、LiMnPO 4、Li 3V 2(PO 4) 3以及它们的改性材料中的一种或几种。
  9. 根据权利要求1-4任一项所述的复合正极材料，其中，所述正极活性材料的充电截止电压为4.2V～5.2V(vs.Li/Li +)，所述富锂金属氧化物选自Li 6CoO 4、Li 5FeO 4、Li 2NiO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 3VO 4、Li 3NbO 4中的一种或几种，其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种；可选地，0.1≤x1≤0.9；进一步可选地，0.2≤x1≤0.8；
    可选地，所述正极活性材料选自LiCoO 2、LiNi aCo bMn cO 2、LiNi αCo βAl γO 2、LiMn 2O 4、LiNi 0.5Mn 1.5O 4、LiCoPO 4、LiNiPO 4以及它们的改性材料中的一种或几种，其中，0＜a＜1，0＜b＜1，0＜c＜1，a+b+c＝1，0＜α＜1，0＜β＜1，0＜γ＜1，α+β+γ＝1。
  10. 根据权利要求9所述的复合正极材料，其中，所述正极活性材料的中值粒径D v50为1μm～15μm，可选为2μm～10μm，进一步可选地为4μm～6μm。
  11. 根据权利要求1-4任一项所述的复合正极材料，其中，所述正极活性材料的充电截止电压为3.5V～4.2V(vs.Li/Li +)，所述富锂金属氧化物选自Li 5FeO 4、Li 2CuO 2、Li 2Cu x1Ni 1-x1-y1M y1O 2、Li 2MnO 2中的一种或几种，其中，0＜x1＜1，0≤y1＜0.1，M选自Zn、Sn、Mg、Fe和Mn中的一种或几种；可选地，0.1≤x1≤0.9；进一步可选地，0.2≤x1≤0.8；
    可选地，所述正极活性材料选自LiFePO 4、Li 3V 2(PO 4) 3和LiFe yMn 1-yPO 4中的一种或几种，其中0＜y＜1；可选地，0.2≤y≤0.8。
  12. 根据权利要求11所述的复合正极材料，其中，所述正极活性材料的中值粒径D v50为0.1μm～3.5μm，可选为0.2μm～2μm，进一步可选地为0.5μm～1.5μm。
  13. 一种复合正极材料的制备方法，包括以下步骤：
    提供核，所述核包括正极补锂材料，所述正极补锂材料包括富锂金属氧化物；
    提供包覆材料，所述包覆材料包括正极活性材料；
    使所述包覆材料包覆所述核的至少一部分表面，得到复合正极材料。
  14. 一种正极极片，包括正极集流体以及设置于所述正极集流体上的正极膜层，所述正极膜层包含根据权利要求1-12任一项所述的复合正极材料、或根据权利要求13所述制备方法得到的复合正极材料。
  15. 根据权利要求14所述的正极极片，其中，所述正极膜层还包含导电剂和粘结剂，其中，基于所述正极膜层的总重量，所述正极膜层中包含70重量％～97重量％的复合正极材料，2重量％～20重量％的导电剂和1重量％～25重量％的粘结剂。
  16. 一种二次电池，包括根据权利要求14或15所述的正极极片。
  17. 一种电池模块，包括根据权利要求16所述的二次电池。
  18. 一种电池包，包括根据权利要求16所述的二次电池、或根据权利要求17所述的电池模块。
  19. 一种装置，包括根据权利要求16所述的二次电池、根据权利要求17所述的电池模块、或根据本申请权利要求18所述的电池包。
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