WO2021190650A1 - 二次电池、含有该二次电池的电池模块、电池包及装置 - Google Patents

二次电池、含有该二次电池的电池模块、电池包及装置 Download PDF

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WO2021190650A1
WO2021190650A1 PCT/CN2021/083463 CN2021083463W WO2021190650A1 WO 2021190650 A1 WO2021190650 A1 WO 2021190650A1 CN 2021083463 W CN2021083463 W CN 2021083463W WO 2021190650 A1 WO2021190650 A1 WO 2021190650A1
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Prior art keywords
active material
negative electrode
electrode active
secondary battery
artificial graphite
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PCT/CN2021/083463
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English (en)
French (fr)
Chinese (zh)
Inventor
马建军
何立兵
沈睿
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202180007775.XA priority Critical patent/CN114902450B/zh
Priority to EP21774396.2A priority patent/EP3961770B1/en
Priority to KR1020237034396A priority patent/KR102778746B1/ko
Priority to KR1020227018607A priority patent/KR102588574B1/ko
Priority to EP23195533.7A priority patent/EP4265568A3/en
Priority to CN202410328877.7A priority patent/CN118263501A/zh
Priority to JP2022532691A priority patent/JP7392151B2/ja
Publication of WO2021190650A1 publication Critical patent/WO2021190650A1/zh
Priority to US17/547,243 priority patent/US20220102700A1/en
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/52—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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/027—Negative 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery, a battery module, a battery pack and a device containing the secondary battery.
  • Secondary batteries have the advantages of reliable working performance, no pollution, no memory effect, etc., so they are widely used. For example, with increasing attention to environmental protection issues and the increasing popularity of new energy vehicles, the demand for power-type secondary batteries will show explosive growth. However, as the application range of the secondary battery becomes wider and wider, the performance of the secondary battery also poses a severe challenge. In order to improve the user experience, the secondary battery needs to take into account various performances such as dynamic performance and cycle life at the same time. However, the problem faced in the prior art is that it is often difficult to take into account the high temperature cycle performance of the battery while improving the dynamic performance of the battery.
  • This application was developed in view of the above technical problems, and its purpose is to provide a secondary battery that can improve the dynamic performance while taking into account better high-temperature cycle performance and safety performance.
  • the first aspect of the present application provides a secondary battery, which includes a positive pole piece and a negative pole piece.
  • a positive electrode film comprising a positive electrode active material, the positive electrode active material comprising one or more of layered lithium transition metal oxides and modified compounds thereof;
  • the negative electrode plate comprising a negative electrode current collector and a negative electrode
  • a negative electrode membrane on at least one surface of the current collector and comprising a negative electrode active material, the negative electrode active material comprising a first material and a second material, the first material comprising artificial graphite, and the second material comprising natural graphite;
  • the artificial graphite contains both primary particles and secondary particles, and the quantity ratio S of the secondary particles in the negative electrode active material satisfies: 10% ⁇ S ⁇ 50%.
  • the inventor of the present application has found through intensive research that when the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds, when the negative electrode active material of the negative electrode film of the secondary battery It includes both artificial graphite and natural graphite. Artificial graphite includes both primary particles and secondary particles, and when the number of secondary particles in the negative electrode active material S is set to a specific range, the secondary battery can improve power At the same time of academic performance, good high temperature cycle performance is also taken into account.
  • the ratio S of the number of secondary particles in the negative electrode active material optionally satisfies: 10% ⁇ S ⁇ 30%, more optionally 15% ⁇ S ⁇ 30%.
  • the volume of the negative electrode active material average particle diameter D v 50 ⁇ 14.0 ⁇ m; alternatively, volume average particle diameter D v negative electrode active material 50 is 8.0 ⁇ m-12.0 ⁇ m; alternatively, a negative electrode active material
  • the volume average particle size D v 50 of TM is 12.0 ⁇ m-14.0 ⁇ m.
  • the volume average particle size D v 50 of the artificial graphite may be 10.0 ⁇ m-14.5 ⁇ m, optionally 11.0 ⁇ m-13.5 ⁇ m; and/or, natural stone
  • the volume average particle diameter D v 50 of the ink may be 7.0 ⁇ m-14.0 ⁇ m, and may be 7.0 ⁇ m-13.0 ⁇ m.
  • the volume distribution particle size D v 90 of the negative active material may be 16.0 ⁇ m-25.0 ⁇ m, and may be 20.0 ⁇ m-25.0 ⁇ m.
  • the battery can simultaneously take into account better dynamic performance, high temperature cycle performance and safety performance.
  • the volume distribution particle size D v 90 of the artificial graphite may be 23.0 ⁇ m-30.0 ⁇ m, optionally 25.0 ⁇ m-29.0 ⁇ m; and/or, natural stone
  • the volume distribution particle size D v 90 of the ink may be 15.0 ⁇ m-23.0 ⁇ m, and may be 18.0 ⁇ m-21.0 ⁇ m.
  • the volume distribution particle diameter D v 99 of the negative active material may be 25.0 ⁇ m-37.0 ⁇ m, and may be 33.0 ⁇ m-36.5 ⁇ m.
  • the battery can simultaneously take into account better dynamic performance, high temperature cycle performance and safety performance.
  • the volume distribution particle size D v 99 of the artificial graphite may be 30.0 ⁇ m-45.0 ⁇ m, optionally 32.0 ⁇ m-43.0 ⁇ m; and/or, natural stone
  • the volume distribution particle size D v 99 of the ink may be 21.0 ⁇ m-35.0 ⁇ m, and may be 25.0 ⁇ m-30.0 ⁇ m.
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative active material may be 1.30 to 1.55, and may be 1.35-1.50.
  • the battery can simultaneously take into account better dynamic performance, high temperature cycle performance and safety performance.
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative electrode active material can be 1.25-1.95, It may be 1.35-1.80; and/or the particle size distribution (D v 90-D v 10)/D v 50 of natural graphite may be 0.88-1.28, and may be 0.98-1.18.
  • the proportion of the secondary particles in the artificial graphite can be 25%-60%, and optionally 30%-50%.
  • the expansion rate of the pole piece can be further reduced.
  • the tap density of the negative electrode active material satisfy ⁇ 1.10g / cm 3, optionally 1.10g / cm 3 -1.15g / cm 3 .
  • the energy density and dynamic performance of the battery can be further improved.
  • the tap density of artificial graphite can be 0.90 g/cm 3 -1.20 g/cm 3 , optionally 1.15 g/cm 3 -1.15 g/cm 3 ; and/or, the tap density of natural graphite density may be 0.90g / cm 3 -1.18g / cm 3 , optionally 0.93g / cm 3 -1.13g / cm 3 .
  • the graphitization degree of the negative electrode active material may be 92%-96%, and may be 93%-95%.
  • the energy density of the battery can be further increased and the expansion rate of the pole piece can be reduced.
  • the graphitization degree of the artificial graphite can be 90%-95%, optionally 93%-95%; and/or the graphitization degree of the natural graphite can be 95% %-98%, 95%-97% can be selected.
  • the surface of natural graphite has a coating layer.
  • a coating layer By forming a coating layer on the surface of natural graphite, its surface activity can be reduced, thereby further improving the high-temperature cycle performance of the battery.
  • the mass proportion of natural graphite in the negative electrode active material may satisfy ⁇ 30%, and may be 15%-25%.
  • the battery can have a higher energy density while significantly reducing side reactions during the battery cycle, thereby further improving the battery's high-temperature cycle performance and safety performance .
  • the compacted density of the negative electrode film can be 1.60 g/cm 3 -1.80 g/cm 3 , and optionally 1.65 g/cm 3 -1.75 g/cm 3 .
  • the compaction density of the negative electrode membrane is within the above range, the dynamic performance and energy density of the battery can be further improved.
  • the areal density of the negative electrode film may be 10.0 mg/cm 2 -13.0 mg/cm 2 , and may be 10.5 mg/cm 2 -11.5 mg/cm 2 .
  • the areal density of the negative electrode membrane is within the above range, the dynamic performance of the battery and the cycle performance of the battery can be further improved.
  • the cohesive force F of the negative electrode membrane may satisfy: 220N/m ⁇ F ⁇ 300N/m, optionally 240N/m ⁇ F ⁇ 260N/m.
  • the cohesive force of the negative electrode membrane is within the above range, the negative electrode membrane can have higher active ion and electron transport performance, and at the same time, it can reduce the cycle expansion rate of the electrode piece, and it can also reduce the addition of binder in the negative electrode membrane. quantity.
  • the positive electrode active material may include a general formula Li a Ni b Co c M d M ' layered lithium transition metal oxides e O f A g, wherein, 0.8 ⁇ a ⁇ 1.2,0.6 ⁇ b ⁇ in any embodiment 1,0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 0 ⁇ e ⁇ 0.1, 1 ⁇ f ⁇ 2, 0 ⁇ g ⁇ 1; M is one or more selected from Mn and Al; M'is One or more selected from Zr, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti and B; A is one or more selected from N, F, S and Cl; Optionally, 0.65 ⁇ b ⁇ 1.
  • the positive electrode active material adopts the above-mentioned materials, the effect of improving the safety performance of the battery is more significant.
  • a second aspect of the present application provides a method for preparing a secondary battery, which is used to prepare the secondary battery of any of the foregoing embodiments, and includes the following steps:
  • the artificial graphite and the natural graphite are mixed to obtain a negative active material;
  • the negative active material includes artificial graphite and natural graphite;
  • the artificial graphite includes both primary particles and secondary particles, and the secondary
  • the proportion S of the number of particles in the negative active material satisfies: 10% ⁇ S ⁇ 50%.
  • a third aspect of the present application provides a battery module, which includes the secondary battery according to the first aspect of the present application or the secondary battery obtained by the preparation method of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack including the battery module according to the third aspect of the present application.
  • a fifth aspect of the present application provides a device, which includes the secondary battery of the first aspect of the present application, the secondary battery prepared by the method of the second aspect of the present application, the battery module of the third aspect of the present application, or the fourth aspect of the present application. At least one of the battery packs of aspect.
  • the battery module, battery pack, and device of the present application have at least the same advantages as the above-mentioned secondary battery.
  • Fig. 1-1 is an ion-polished cross-sectional morphology (CP) diagram of an embodiment of artificial graphite of the present application.
  • Figure 1-2 is an ion-polished cross-sectional morphology (CP) diagram of an embodiment of natural graphite of the present application.
  • FIG. 2-1 is a scanning electron microscope (SEM) image of an embodiment of the negative electrode active material in the negative electrode film of the present application.
  • Figure 2-2 is a scanning electron microscope (SEM) image of another embodiment of the negative electrode active material in the negative electrode film 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 an 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 other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range.
  • every point or single value between the end points of the range is included in the range. Therefore, each point or single numerical value can be used as its own lower limit or upper limit in combination with any other point or single numerical value or in combination with other lower or upper limits to form an unspecified range.
  • the first aspect of the application provides a secondary battery.
  • a secondary battery usually includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions are inserted and extracted back and forth between the positive pole piece and the negative pole piece.
  • the isolation film is arranged between the positive pole piece and the negative pole piece, which can insulate electrons, prevent internal short circuits, and enable active ions to penetrate and move between the positive and negative electrodes.
  • the electrolyte conducts ions between the positive pole piece and the negative pole piece.
  • the negative electrode piece of the present application includes a negative electrode current collector and a negative electrode membrane provided on at least one surface of the negative electrode current collector.
  • the negative electrode membrane includes a negative electrode active material.
  • the negative active material includes a first material and a second material, the first material includes artificial graphite, and the second material includes natural graphite.
  • the artificial graphite includes both primary particles and secondary particles, and the quantity ratio S of the secondary particles in the negative electrode active material satisfies: 10% ⁇ S ⁇ 50%.
  • the quantity ratio S of the secondary particles in the negative electrode active material may be within a numerical range constituted by any two of the following listed values as end values: 10%, 13%, 15% , 17%, 20%, 23%, 25%, 30%, 33%, 35%, 40%, 42%, 45%, 48%, 50%.
  • S can satisfy: 15% ⁇ S ⁇ 50%, 20% ⁇ S ⁇ 48%, 25% ⁇ S ⁇ 50%, 30% ⁇ S ⁇ 50%, 10% ⁇ S ⁇ 30%, 15% ⁇ S ⁇ 30%, 20% ⁇ S ⁇ 45%.
  • the inventors of the present application have found through intensive research that when the negative electrode active material of the negative electrode membrane includes both artificial graphite and natural graphite, the artificial graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material
  • the proportion is within a specific range, it can reduce the cyclic expansion of the negative pole piece during the charge and discharge process, and at the same time, it also has a higher reversible capacity and higher active ion transport performance, thereby effectively improving the high temperature cycle of the secondary battery. Performance and dynamics performance.
  • primary particles and the secondary particles in the negative electrode active material both have a well-known meaning in the art.
  • primary particles refer to particles in a non-agglomerated state.
  • the secondary particles refer to the agglomerated particles formed by the aggregation of two or more primary particles.
  • Primary particles and secondary particles can be distinguished by using scanning electron microscope (SEM) images.
  • the proportion of the secondary particles in the negative active material S means: any one test sample is taken from the negative electrode film, multiple test areas are taken from the test sample, and the scanning electron microscope SEM is used to obtain the results of the multiple test areas. Image, count the proportion of the number of negative active material particles with secondary particle morphology in each SEM image to the total number of negative active material particles, and the average of multiple statistical results is the number of secondary particles in the negative active material Accounted for.
  • Artificial graphite generally refers to graphite materials obtained through high-temperature graphitization treatment, and the degree of graphitization and crystallization is usually high. Under normal circumstances, the crystal lattice structure of artificial graphite tends to be arranged in a long-range orderly layered arrangement, which can be observed by a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • Natural graphite generally refers to graphite formed naturally in nature and does not need to be graphitized.
  • natural graphite particles usually have more closed-cell structures inside.
  • the negative electrode active material can be prepared into a negative pole piece, and the negative pole piece can be subjected to an ion polishing cross-sectional morphology (CP) test to observe the type of material.
  • CP ion polishing cross-sectional morphology
  • the test method can be: preparing artificial graphite into a negative pole piece, cutting the prepared negative pole piece into a sample to be tested of a certain size (for example, 2cm ⁇ 2cm), and fixing the negative pole piece on the sample table with paraffin wax superior.
  • argon ion cross-section polisher such as IB-19500CP
  • vacuum such as 10-4Pa
  • argon flow such as 0.15MPa
  • voltage such as 8KV
  • polishing time for example, 2 hours
  • sample test please refer to JY/T010-1996. It is possible to randomly select an area in the sample to be tested for scanning test, and obtain the ion polished cross-sectional topography (CP) picture of the negative pole piece at a certain magnification (for example, 1000 times).
  • Fig. 1-1 is an example of the artificial graphite of the present application.
  • Fig. 1-1 It can be seen from Fig. 1-1 that the material particles are denser and have fewer pores.
  • Fig. 1-2 is an example of the natural graphite of the present application. Compared with Fig. 1-1, the material particles of Fig. 1-2 have more internal pores and mostly have a closed-pore structure.
  • the particle morphology of the negative electrode active material and the proportion of the number of secondary particles can be tested using methods known in the art.
  • Use scanning electron microscope & energy spectrometer such as ZEISS SEM (sigma300) to test the morphology of the particles in the sample to be tested.
  • the test can refer to JY/T010-1996.
  • 2-1 and 2-2 are scanning electron microscope (SEM) images of specific embodiments of the negative electrode active material in the negative electrode film of the present application. It can be seen from Figure 2-1 and Figure 2-2 that the negative electrode active material includes artificial graphite and natural graphite, and artificial graphite includes both primary particles and secondary particles. The number of secondary particles in the negative electrode active material can be counted from the SEM image.
  • SEM scanning electron microscope
  • S is related to the intrinsic parameters of the active material and the formulation design of the pole piece. Those skilled in the art can adjust the above parameters to realize the proportion of the secondary particles in this application. For example, when the models of artificial graphite and natural graphite are fixed (that is, specific artificial graphite and natural graphite are selected), the mixing ratio of artificial graphite and natural graphite and the pole piece preparation process (such as the compaction density of the pole piece) can be adjusted. Etc.) to adjust the size of S.
  • the preparation process of artificial graphite and/or natural graphite (such as raw material type, shaping process, granulation process, etc.) and the intrinsic parameters of artificial graphite (such as volume average particle size) can be adjusted. Diameter, material morphology, etc.) and the pole piece preparation process (such as the compaction density of the pole piece, etc.) to adjust the size of S.
  • the volume average particle diameter D v 50 of the negative active material may be 8.0 ⁇ m-19.0 ⁇ m.
  • the volume average particle size D v 50 of the negative electrode active material can be within a numerical range composed of any two of the following listed values as end values: 8.0 ⁇ m, 8.5 ⁇ m, 8.9 ⁇ m, 9.0 ⁇ m, 9.2 ⁇ m, 9.6 ⁇ m, 10.0 ⁇ m, 10.2 ⁇ m, 10.5 ⁇ m, 10.8 ⁇ m, 11.3 ⁇ m, 11.6 ⁇ m, 11.9 ⁇ m, 12.2 ⁇ m, 12.4 ⁇ m, 12.8 ⁇ m, 13.2 ⁇ m, 13.5 ⁇ m, 14.0 ⁇ m, 14.2 ⁇ m, 14.5 ⁇ m, 15.0 ⁇ m, 15.5 ⁇ m , 15.9 ⁇ m, 16.0 ⁇ m, 16.3 ⁇ m, 16.5 ⁇ m, 17.0 ⁇ m, 17.5 ⁇ m, 18.0 ⁇ m, 18.4 ⁇ m, 19.0 ⁇ m.
  • the volume average particle diameter D v 50 of the negative active material may be 8.0 ⁇ m-17.5 ⁇ m, 8.0 ⁇ m-15.5 ⁇ m, 8.0 ⁇ m-14.5 ⁇ m, 8.0 ⁇ m-14.0 ⁇ m, 8.0 ⁇ m-12.0 ⁇ m, 8.5 ⁇ m-13.5 ⁇ m , 8.5 ⁇ m-13.0 ⁇ m, 8.5 ⁇ m-12.5 ⁇ m, 8.5 ⁇ m-11.5 ⁇ m, 9.0 ⁇ m-18.0 ⁇ m, 9.0 ⁇ m-16.5 ⁇ m, 9.0 ⁇ m-14.2 ⁇ m, 9.0 ⁇ m-13.5 ⁇ m, 9.2 ⁇ m-14.0 ⁇ m, 10.0 ⁇ m-13.5 ⁇ m, 11.0 ⁇ m-19.0 ⁇ m, 11.0 ⁇ m-15.0 ⁇ m, 11.5 ⁇ m-18.0 ⁇ m, 12.0 ⁇ m-18.0 ⁇ m, 12.0 ⁇ m-14.0 ⁇ m, 13.0 ⁇ m-19.0 ⁇ m, 14.0 ⁇ m-18.5 ⁇ m, 15.0 ⁇ m- 19.0 ⁇ m, 15.5 ⁇ m-18.0 ⁇ m, 16.0
  • the volume average particle size D v 50 of the artificial graphite may be 10.0 ⁇ m-19.0 ⁇ m.
  • the volume average particle size D v 50 of artificial graphite can be within the numerical range formed by any two of the following values as the end values: 10.0 ⁇ m, 11.0 ⁇ m, 12.0 ⁇ m, 13.0 ⁇ m, 13.5 ⁇ m, 14.5 ⁇ m, 15.0 ⁇ m, 16.0 ⁇ m, 17.0 ⁇ m, 18.0 ⁇ m, 19.0 ⁇ m, for example, the volume average particle diameter D v 50 of artificial graphite may be 10.0 ⁇ m-19.0 ⁇ m, 12.0 ⁇ m-18.0 ⁇ m, 13.0 ⁇ m-17.0 ⁇ m, 10.0 ⁇ m-14.5 ⁇ m, 11.0 ⁇ m-13.5 ⁇ m, 12.0 ⁇ m-16.0 ⁇ m, 13.0 ⁇ m-15.0 ⁇ m, 14.0 ⁇ m-18.0 ⁇ m, 15.0 ⁇ m-19
  • the volume average particle size D v 50 of the natural graphite may be 7.0 ⁇ m-20.0 ⁇ m.
  • the volume average particle size D v 50 of natural graphite can be within the numerical range formed by any two of the following values as the end values: 7.0 ⁇ m, 10.0 ⁇ m, 11.0 ⁇ m, 13.0 ⁇ m, 14.0 ⁇ m, 15.0 ⁇ m, 16.0 ⁇ m, 18.0 ⁇ m, 19.0 ⁇ m, 20.0 ⁇ m, for example, the volume average particle size D v 50 of natural graphite may be 7.0 ⁇ m-20.0 ⁇ m, 7.0 ⁇ m-14.0 ⁇ m, 7.0 ⁇ m-13.0 ⁇ m, 10.0 ⁇ m-19.0 ⁇ m, 10.0 ⁇ m-14.0 ⁇ m, 11.0 ⁇ m-18.0 ⁇ m, 11.0 ⁇ m-13.0 ⁇ m, 15.0 ⁇ m-20.0 ⁇ m, 15.0 ⁇ m-19.0 ⁇ m
  • the volume distribution particle size D v 90 of the natural graphite may be 15.0 ⁇ m-35.0 ⁇ m, and the volume distribution particle size D of the natural graphite v 90 can be within the numerical range formed by any two of the following values as the end values: 15.0 ⁇ m, 18.0 ⁇ m, 21.0 ⁇ m, 23.0 ⁇ m, 25.0 ⁇ m, 31.0 ⁇ m, 35.0 ⁇ m, for example, the volume of natural graphite
  • the distributed particle diameter D v 90 may be 15.0 ⁇ m-23.0 ⁇ m, 18.0 ⁇ m-21.0 ⁇ m, 25.0 ⁇ m-35.0 ⁇ m, 25.0 ⁇ m-31.0 ⁇ m.
  • the volume distribution particle size D v 99 of the artificial graphite may be 30.0 ⁇ m-50.0 ⁇ m, and the volume distribution particle size D of the artificial graphite v 99 can be within the numerical range formed by any two of the following values as end values: 30.0 ⁇ m, 32.0 ⁇ m, 38.0 ⁇ m, 40.0 ⁇ m, 43.0 ⁇ m, 45.0 ⁇ m, 48.0 ⁇ m, 50.0 ⁇ m, for example, artificial
  • the volume distribution particle size D v 99 of graphite may be 30.0 ⁇ m-45.0 ⁇ m, 32.0 ⁇ m-43.0 ⁇ m, 38.0 ⁇ m-50.0 ⁇ m, 40.0 ⁇ m-48.0 ⁇ m.
  • the volume distribution particle size D v 99 of the natural graphite may be 21.0 ⁇ m-48.0 ⁇ m, and the volume distribution particle size D of the natural graphite v 99 can be within the numerical range formed by any two of the following listed values as end values: 21.0 ⁇ m, 25.0 ⁇ m, 30.0 ⁇ m, 32.0 ⁇ m, 35.0 ⁇ m, 45.0m, 48.0 ⁇ m, for example, the volume of natural graphite
  • the distributed particle size D v 99 may be 21.0 ⁇ m-35.0 ⁇ m, 25.0 ⁇ m-30.0 ⁇ m, 30.0 ⁇ m-48.0 ⁇ m, 32.0 ⁇ m-45.0 ⁇ m.
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative electrode active material it can be 1.25-1.95.
  • the particle size distribution of artificial graphite (D v 90-D v 10)/D v 50 can be within the numerical range formed by any two of the following values as the end values: 1.25, 1.30, 1.35, 1.45, 1.65, 1.80 , 1.95, for example, the particle size distribution (D v 90-D v 10)/D v 50 of artificial graphite can be 1.25-1.95, 1.25-1.65, 1.30-1.45, 1.35-1.80.
  • the particle size distribution of natural graphite (D v 90-D v 10)/D v 50 can be within the numerical range formed by any two of the following values as end values: 0.88, 0.90, 0.98, 1.05, 1.18, 1.25 , 1.28, 1.30, for example, the particle size distribution (D v 90-D v 10)/D v 50 of natural graphite can be 0.88-1.28, 0.90-1.30, 0.98-1.18, 1.05-1.25.
  • the D v 99, D v 90, D v 50, and D v 10 of the negative electrode active material, artificial graphite, and natural graphite have meanings known in the art, and can be tested by methods known in the art. For example, it can be measured with a laser particle size analyzer (such as Malvern Master Size 3000) with reference to the standard GB/T 19077.1-2016.
  • a laser particle size analyzer such as Malvern Master Size 3000
  • the proportion of the secondary particles in the artificial graphite may be 25%-80%.
  • the proportion of the secondary particles in the artificial graphite can be within the numerical range formed by any two of the following listed values as the end values: 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%.
  • the proportion of secondary particles in artificial graphite can be 25%-60%, 30%-50%, 30%-45%, 35%-50%, 35%-45%, 50%-80% , 55%-75%, 60%-75%, 65%-80%.
  • the natural graphite includes primary particles, and the number of primary particles in the natural graphite accounts for ⁇ 90%; for example, ⁇ 95%, ⁇ 97%, ⁇ 98%.
  • the natural graphite is all primary particles (that is, the proportion of the primary particles in the natural graphite is 100%).
  • the tap density of the negative active material may be 1.0 g/cm 3 -1.3 g/cm 3 .
  • the tap density of the negative electrode active material can be within the numerical range formed by any two of the following listed values as end values: 1.0g/cm 3 , 1.05g/cm 3 , 1.09g/cm 3 , 1.10g/cm 3. 1.15g/cm 3 , 1.2g/cm 3 , 1.3g/cm 3 .
  • the tap density of the negative electrode active material may be 1.05g / cm 3 -1.2g / cm 3 , 0.90g / cm 3 -1.20g / cm 3, 1.0g / cm 3 -1.09g / cm 3, 1.05g / cm 3 -1.15g/cm 3 , 1.10g/cm 3 -1.15g/cm 3 .
  • the tap density of the negative electrode active material has a well-known meaning in the art, and can be tested by methods known in the art. For example, you can refer to the standard GB/T 5162-2006 and use a powder tap density tester (such as Dandong Baxter BT-301) for testing.
  • a powder tap density tester such as Dandong Baxter BT-301
  • a tap density of artificial graphite may be 0.85g / cm 3 -1.25g / cm 3 , 0.90g / cm 3 -1.18g / cm 3, 0.90g / cm 3 -1.35g / cm 3, 0.9g / cm 3 -1.30g / cm 3, 0.9g / cm 3 -1.20g / cm 3, 0.95g / cm 3 -1.15g / cm 3, 1.05g / cm 3 -1.15g / cm 3, 1.15g / cm 3 - 1.30g/cm 3 .
  • the tap density of natural graphite may be 0.80 g/cm 3 -1.35 g/cm 3 .
  • the tap density of natural graphite can be within the numerical range formed by any two of the values listed below as end values: 0.80g/cm 3 , 0.90g/cm 3 , 0.93g/cm 3 , 0.95g/cm 3 , 1.00g/cm 3 , 1.13g/cm 3 , 1.15g/cm 3 , 1.18g/cm 3 , 1.20g/cm 3 , 1.30g/cm 3 , 1.35g/cm 3 .
  • the tap density of the natural graphite may be 0.8g / cm 3 -1.35g / cm 3 , 0.80g / cm 3 -1.30g / cm 3, 0.90g / cm 3 -1.18g / cm 3, 0.90g / cm 3 -1.20g/cm 3 , 0.93g/cm 3 -1.13g/cm 3 , 0.95g/cm 3 -1.2g/cm 3 , 0.95g/cm 3 -1.15g/cm 3 , 1.00g/cm 3- 1.20g/cm 3 .
  • the graphitization degree of the negative active material may be 92%-96%.
  • the graphitization degree of the negative electrode active material can be within the numerical range formed by any two of the following values as the end values: 92%, 92.3%, 92.7%, 93%, 93.4%, 94%, 94.2%, 94.4 %, 94.7%, 95%, 95.2%, 95.5%, 96%.
  • the graphitization degree of the negative active material may be 92%-95%, 93%-95%, 93%-94%, 94%-96%, 94.2%-95.5%.
  • the graphitization degree of the artificial graphite may be 90%-95%.
  • the graphitization degree of artificial graphite can be within the numerical range formed by any two of the following values as the end values: 90%, 91%, 92%, 93%, 94%, 95%, for example, the artificial graphite
  • the degree of graphitization can be 91%-94%, 91%-93%, 92%-95%, 93%-95%.
  • the graphitization degree of natural graphite can be 93%-98%, and the graphitization degree of natural graphite can be any of the values listed below Within two numerical ranges constituted as end values: 93%, 94%, 95%, 96%, 97%, 98%, for example, the graphitization degree of natural graphite can be 94%-98%, 94%- 97%, 95%-98%, 95%-97%, 96%-97%.
  • the degree of graphitization of the negative electrode active material, natural graphite, and artificial graphite has a well-known meaning in the art, and can be tested by a method known in the art.
  • an X-ray diffractometer such as Bruker D8 Discover
  • CuK ⁇ rays are used as the radiation source, and the wavelength of the rays is The scanning 2 ⁇ angle range is 20°-80°, and the scanning rate is 4°/min.
  • the surface of the artificial graphite does not have a coating layer.
  • the artificial graphite of the present application has a relatively stable surface. When the surface does not have a coating layer, it is beneficial to maintain its lower reactivity (because the reactivity of the carbon coating layer is higher than that of the surface of the artificial graphite substrate of the present application. High), which is beneficial to reduce side reactions during battery cycling, thereby further improving the high-temperature cycling performance of the battery.
  • the surface of natural graphite has a coating layer (for example, a carbon coating layer).
  • a coating layer for example, a carbon coating layer.
  • the natural graphite of the present application has relatively high surface activity, and the formation of a coating layer on its surface can reduce its surface activity (because natural graphite has more defects on the surface after spheroidization and purification treatment, the coating layer formed by carbonization can effectively Repair surface defects and reduce side reactions during cycling), thereby further improving the high-temperature cycling performance of the battery.
  • the carbon coating layer can be formed on the surface of natural graphite by calcination and thermal decomposition of petroleum or coal pitch.
  • the transmission electron microscope (TEM) image can be used to determine whether there is a coating on the surface of artificial graphite and natural graphite.
  • the mass ratio of natural graphite in the negative electrode active material is ⁇ 50%, for example, it can be 10%-50%.
  • the mass proportion of natural graphite in the negative electrode active material can be within the numerical range formed by any two of the following listed values as the end values: 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%.
  • the mass proportion of natural graphite in the negative electrode active material may be 10%-30%, 15%-25%, 20%-50%, 35%-50%, 35%-45%.
  • the negative electrode current collector can be made of materials with good electrical conductivity and mechanical strength to play the role of conduction and current collection.
  • copper foil may be used as the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode film is laminated on either or both of the two surfaces of the negative electrode current collector.
  • the negative electrode active material may further include other active materials, and the other active materials may include, but are not limited to, one or more of hard carbon, soft carbon, silicon-based materials, and tin-based materials.
  • the silicon-based material can be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen compounds, and silicon alloys.
  • the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.
  • the negative electrode membrane further includes a thickener.
  • the thickener may be sodium carboxymethyl cellulose (CMC-Na).
  • the negative electrode membrane further includes a conductive agent.
  • the conductive agent used for the negative electrode film may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the areal density of the negative electrode membrane prepared by using the aforementioned negative electrode active material may be 7 mg/cm 2 to 13 mg/cm 2 .
  • the areal density of the negative electrode membrane can be within the numerical range formed by any two of the following values as the end values: 7mg/cm 2 , 8mg/cm 2 , 10mg/cm 2 , 10.5mg/cm 2 , 11.5mg /cm 2 , 13.0mg/cm 2 .
  • the surface density of the negative electrode film can be 7mg/cm 2 -10mg/cm 2 , 7mg/cm 2 -8mg/cm 2 , 10.0mg/cm 2 -13.0mg/cm 2 , 10.5mg/cm 2 -11.5mg /cm 2 .
  • the compacted density of the negative electrode membrane prepared by using the aforementioned negative electrode active material may be 1.40 g/cm 3 -1.80 g/cm 3 .
  • the compaction density of the negative electrode film can be within the numerical range formed by any two of the following listed values as end values: 1.40g/cm 3 , 1.50g/cm 3 , 1.40g/cm 3 , 1.55g/cm 3. 1.60g/cm 3 , 1.65g/cm 3 , 1.68g/cm 3 , 1.70g/cm 3 , 1.73g/cm 3 , 1.75g/cm 3 , 1.80g/cm 3 .
  • the compaction density of the negative electrode film can be 1.50g/cm 3 -1.70g/cm 3 , 1.55g/cm 3 -1.60g/cm 3 , 1.60g/cm 3 -1.80g/cm 3 , 1.65g/cm 3 cm 3 -1.75g / cm 3, 1.68g / cm 3 -1.73g / cm 3.
  • the compaction density of the negative electrode film has a well-known meaning in the art, and can be tested by a method known in the art. For example, take the cold-pressed negative electrode piece, measure the thickness of the negative electrode film (here, measure the thickness of the negative electrode film on any surface of the negative electrode current collector), and then test the areal density of the negative electrode film according to the above method.
  • the compaction density of the negative electrode membrane area density of the negative electrode membrane/thickness of the negative electrode membrane.
  • the cohesive force F of the negative electrode membrane prepared by using the aforementioned negative electrode active material may satisfy 150N/m ⁇ F ⁇ 300N/m.
  • the cohesive force F of the negative electrode membrane can be within the numerical range formed by any two of the following listed values as end values: 150N/m, 180N/m, 220N/m, 240N/m, 250N/m, 260N/m , 300N/m.
  • the cohesive force F of the negative electrode film may be 150N/m-250N/m, 180N/m-220N/m, 220N/m-300N/m, 240N/m-260N/m.
  • the cohesion of the negative electrode film is a well-known meaning in the art, and can be tested by methods known in the art.
  • An exemplary test method is as follows: take the cold-pressed negative electrode piece (if it is a double-sided coated negative electrode piece, wipe off the negative electrode film on one side first), and cut the negative electrode piece to a length of 100mm and a width of 10mm to be tested sample. Take a stainless steel plate with a width of 25mm, paste the double-sided tape (width 11mm), paste the sample to be tested on the double-sided tape on the stainless steel plate, where the negative current collector is bonded to the double-sided tape; use a 2000g pressure roller to test the sample The surface is rolled back and forth three times at a rate of 300mm/min.
  • a tape with a width of 10 mm and a thickness of 50 ⁇ m was pasted on the surface of the negative electrode film, and a 2000 g pressure roller was used to roll it back and forth three times at a rate of 300 mm/min. Bend the tape 180 degrees, manually peel off the tape and negative electrode film by 25mm, and fix the sample on the Instron 336 tensile testing machine to keep the peeling surface consistent with the force line of the testing machine (that is, perform 180° peeling).
  • test sample is taken from a prepared secondary battery, as an example, the sample can be taken as follows:
  • step (1) Bake the dried negative pole piece in step (1) at a certain temperature and time (for example, 400°C, 2h), choose any area in the negative pole piece after baking, and sample the negative electrode active material (You can choose to scrape powder sampling by blade).
  • a certain temperature and time for example, 400°C, 2h
  • step (3) The negative active material collected in step (2) is sieved (for example, sieved with a 200-mesh sieve), and finally a sample that can be used to test the parameters of the above-mentioned negative active material is obtained.
  • the positive pole piece may include a positive electrode current collector and a positive electrode membrane provided on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode film is laminated on either or both of the two surfaces of the positive electrode current collector.
  • the positive electrode current collector can be made of materials with good electrical conductivity and mechanical strength to play the role of conduction and current collection.
  • aluminum foil may be used as the anode current collector.
  • the positive electrode membrane includes a positive electrode active material.
  • a positive electrode active material for a secondary battery known in the art can be used.
  • the positive electrode active material may include one or more of layered lithium transition metal oxides and modified compounds thereof, olivine-structured lithium-containing phosphates and modified compounds thereof, and the like.
  • the positive active material includes layered lithium transition metal oxides and modified compounds thereof.
  • layered lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt oxide
  • the layered lithium transition metal oxide can be selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof.
  • the modified compound of the layered lithium transition metal oxide may be doping modification and/or surface coating modification of the layered lithium transition metal oxide.
  • the positive active material includes layered lithium transition metal oxides and modified compounds thereof (especially including lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and modified compounds thereof), and the negative active material includes Artificial graphite and natural graphite, artificial graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material S satisfies: 10% ⁇ S ⁇ 50%.
  • S satisfies 10% ⁇ S ⁇ 30%, such as 15% ⁇ S ⁇ 30%, such as 20%, 25%, 30%
  • the battery can take into account both good kinetic performance and high-temperature cycle performance.
  • the positive electrode active material includes one or more of layered lithium transition metal oxides and their modified compounds (especially including lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, etc.) And modified compounds thereof)
  • the negative electrode active material includes artificial graphite and natural graphite, the artificial graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material S satisfies the range given in this application, If the negative electrode active material also optionally satisfies one or more of the following conditions, the performance of the battery can be further improved.
  • the volume average particle size D v 50 of the negative active material is ⁇ 14.0 ⁇ m.
  • the volume average particle size D v 50 of the negative electrode active material can be within a numerical range composed of any two of the following listed values as end values: 8.0 ⁇ m, 8.5 ⁇ m, 8.9 ⁇ m, 9.0 ⁇ m, 9.2 ⁇ m, 9.6 ⁇ m, 10.0 ⁇ m, 10.2 ⁇ m, 10.5 ⁇ m, 10.8 ⁇ m, 11.2 ⁇ m, 11.6 ⁇ m, 11.9 ⁇ m, 12.2 ⁇ m, 12.4 ⁇ m, 12.8 ⁇ m, 13.1 ⁇ m, 13.2 ⁇ m, 13.5 ⁇ m, 13.8 ⁇ m, 13.9 ⁇ m, 14.0 ⁇ m.
  • the volume average particle diameter D v 50 of the negative active material may be 8.0 ⁇ m-14.0 ⁇ m, 8.0 ⁇ m-12.0 ⁇ m, 8.5 ⁇ m-13.5 ⁇ m, 8.5 ⁇ m-13.0 ⁇ m, 8.5 ⁇ m-12.5 ⁇ m, 8.5 ⁇ m-11.5 ⁇ m , 8.9 ⁇ m-12.2 ⁇ m, 9.0 ⁇ m-14.0 ⁇ m, 9.0 ⁇ m-13.5 ⁇ m, 9.2 ⁇ m-14.0 ⁇ m, 10.0 ⁇ m-13.5 ⁇ m, 11.0 ⁇ m-14.0 ⁇ m, 11.5 ⁇ m-13.5 ⁇ m, 12.0 ⁇ m-14.0 ⁇ m.
  • the inventor of the present application discovered that when the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, the D v 50 of the negative electrode active material is adjusted at the same time, When it is within the given range, the cyclic expansion rate of the pole piece can be further reduced without affecting other properties (such as kinetic performance and high-temperature cycle performance), thereby further improving the safety performance of the battery.
  • the inventor’s research found that when the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, if the D v 50 of the negative electrode active material is within the above range , It will reduce the polarization of the battery, effectively reduce the occurrence of side reactions, greatly reduce the probability of lithium evolution from the pole piece, and reduce the cycle expansion rate of the negative pole piece, thereby further improving the safety performance of the battery.
  • the volume average particle size D v 50 of the artificial graphite may be 10.0 ⁇ m-14.5 ⁇ m, and may be 11.0 ⁇ m-13.5 ⁇ m. , For example, 10.3 ⁇ m, 10.8 ⁇ m, 11.4 ⁇ m, 12.3 ⁇ m, 13.0 ⁇ m, 14.0 ⁇ m.
  • the volume average particle diameter D v 50 of natural graphite may be 7.0 ⁇ m-14.0 ⁇ m, and may be 7.0 ⁇ m-13.0 ⁇ m. , For example, 7.1 ⁇ m, 8.7 ⁇ m, 11.2 ⁇ m, 12.1 ⁇ m, 12.4 ⁇ m, 12.8 ⁇ m.
  • the volume distribution particle size D v 90 of the negative active material may be 16.0 ⁇ m-25.0 ⁇ m, and may be 20.0 ⁇ m-25.0 ⁇ m.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, while adjusting the D v 90 of the negative electrode active material to be within the given range , Can take into account better dynamic performance, high temperature cycle performance and safety performance at the same time.
  • the volume distribution particle size D v 90 of the artificial graphite may be 23.0 ⁇ m-30.0 ⁇ m, optionally 25.0 ⁇ m-29.0 ⁇ m .
  • the volume distribution particle size D v 90 of the negative electrode active material may be 15.0 ⁇ m-23.0 ⁇ m, and may be 18.0 ⁇ m-21.0 ⁇ m. .
  • the volume distribution particle diameter D v 99 of the negative active material may be 25.0 ⁇ m-37.0 ⁇ m, and may be 33.0 ⁇ m-36.5 ⁇ m.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, while adjusting the D v 99 of the negative electrode active material to be within the given range , Can make the battery take into account better dynamic performance, high temperature cycle performance and safety performance at the same time.
  • the volume distribution particle size D v 99 of the artificial graphite may be 30.0 ⁇ m-45.0 ⁇ m, optionally 32.0 ⁇ m-43.0 ⁇ m .
  • the volume distribution particle size D v 99 of the negative electrode active material may be 21.0 ⁇ m-35.0 ⁇ m, and may be 25.0 ⁇ m-30.0 ⁇ m. .
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative active material may be 1.30 to 1.55, and may be 1.35-1.50.
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative electrode active material can be 1.25-1.95, and can be 1.35-1.80.
  • the particle size distribution of natural graphite (D v 90-D v 10)/D v 50 can be 0.88-1.28, optional 0.98-1.18.
  • the proportion of the secondary particles in the artificial graphite is 25%-60%, and optionally 30%-50%.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds
  • the energy density of the battery will be greatly improved, but the cycle life will be relatively poor.
  • the secondary particles are When the proportion of the negative electrode active material and the proportion of the secondary particles in the artificial graphite are both within the given range, the cohesion of the negative electrode film can be effectively improved on the premise of ensuring that the negative electrode has a small expansion rate. And adhesive force, thereby further improving the high temperature cycle performance of the battery.
  • the tap density of the negative electrode active material ⁇ 1.10g / cm 3, optionally 1.10g / cm 3 -1.15g / cm 3 .
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, while adjusting the tap density of the negative electrode active material to make it within the given range , Can further improve the energy density and dynamic performance of the battery.
  • the tap density of the artificial graphite may be 0.90 g/cm 3 -1.20 g/cm 3 , optionally 1.05 g/cm 3 -1.15 g/cm 3 .
  • the tap density of natural graphite may be 0.90 g/cm 3 -1.18 g/cm 3 , for example, it may be 0.93 g/cm 3 -1.13 g/cm 3 .
  • the graphitization degree of the negative active material may be 92%-96%, and may be 93%-95%.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, while adjusting the graphitization degree of the negative electrode active material to make it within the given range , Can further improve the energy density and cycle expansion of the battery.
  • the graphitization degree of the artificial graphite may be 92%-95%, optionally 93%-95%.
  • the graphitization degree of natural graphite may be 95%-98%, for example, it may be 95%-97%.
  • the surface of the artificial graphite does not have a coating layer.
  • the surface of natural graphite has a carbon coating layer.
  • the mass ratio of natural graphite in the negative electrode active material is ⁇ 30%, for example, it can be 10%-30%, 15%-25%.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds, and S is within the given range, the mass ratio of natural graphite in the negative electrode active material is adjusted to make it in Within the given range, the high temperature cycle performance and safety performance of the battery can be further improved.
  • the gram capacity of the negative electrode active material may be 351 mAh/g-359 mAh/g, and optionally 353 mAh/g-357 mAh/g.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds and S is within the given range, while adjusting the gram capacity of the negative electrode active material to be within the given range, Further improve the dynamic performance and energy density of the secondary battery.
  • the gram capacity of the artificial graphite may be 349 mAh/g-357 mAh/g, optionally 351 mAh/g-355 mAh/g.
  • the gram capacity of natural graphite may be 360 mAh/g-367 mAh/g, for example, 361 mAh/g-365 mAh/g.
  • the compaction density of the negative electrode film can be 1.60 g/ cm 3 -1.80g / cm 3, for example, may be 1.65g / cm 3 -1.75g / cm 3 , 1.68g / cm 3 -1.73g / cm 3.
  • the compaction density of the negative electrode membrane is within the above range, it is helpful to make the secondary particles in the negative electrode membrane account for the number of secondary particles in the negative electrode active material S within the given range, thereby further improving the cycle life of the battery; at the same time; It can effectively reduce the probability of defects on the surface of the negative electrode active material, reduce the occurrence of side reactions, and reduce the expansion of the battery during cycling, thereby further improving the safety performance of the battery.
  • the areal density of the negative electrode film may be 10.0 mg/cm 2 -13.0mg / cm 2, optionally 10.5mg / cm 2 -11.5mg / cm 2 .
  • the battery can have a higher energy density, and the battery also has better active ion and electron transport performance, thereby further improving the dynamic performance of the battery, and further reducing Polarization and side reactions, thereby further improving the cycle performance of the battery.
  • the cohesive force F of the negative electrode membrane satisfies: 220N/ m ⁇ F ⁇ 300N/m, for example, 240N/m ⁇ F ⁇ 260N/m.
  • the inside of the negative electrode membrane have suitable cohesive force, the structure of the negative electrode active material can be better protected from being damaged, and the negative electrode membrane can have a porosity that can quickly infiltrate the electrolyte, especially the negative electrode membrane has a higher Active ion and electron transport performance, while reducing the battery cycle expansion force. Therefore, the use of the negative electrode membrane can further improve the cycle performance and dynamic performance of the battery.
  • the cohesion of the negative electrode membrane is controlled within an appropriate range, which can also reduce the amount of binder added in the negative electrode membrane.
  • the positive electrode active material comprising a europium layered lithium transition metal oxide Li a Ni b Co c M d M 'e O f A g , wherein, 0.8 ⁇ a ⁇ 1.2,0 ⁇ b ⁇ 1 , 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 0 ⁇ e ⁇ 0.1, 1 ⁇ f ⁇ 2, 0 ⁇ g ⁇ 1; M is one or more selected from Mn and Al; M'is optional From one or more of Zr, Mn, Al, Zn, Cu, Cr, Mg, Fe, V, Ti and B; A is one or more selected from N, F, S and Cl. Optionally, 0.6 ⁇ b ⁇ 1, for example, 0.65 ⁇ b ⁇ 1. The inventor found that when b is within this range, the negative electrode active material of any of the above embodiments is safe for the battery when matched with the positive electrode active material. The performance improvement effect is more significant.
  • the positive electrode active material includes one or more of the layered lithium transition metal oxide and its modified compounds
  • the following steps may be adopted to prepare the negative electrode active material of the present application:
  • Intermediate product 2 is obtained by high-temperature graphitization of intermediate product 1, and intermediate product 2 is mixed in a mixer, and sieved to obtain artificial graphite A of the present application.
  • non-needle petroleum coke is used as the raw material, and the volatile content of the raw material is ⁇ 6%, and the sulfur content is ⁇ 1%.
  • the non-needle petroleum coke that meets the above conditions has good self-adhesiveness, and it is easy to prepare secondary particles of artificial graphite, which helps to achieve the scope of S of the present application.
  • the volatile content of the raw material is 8%-15%.
  • the sulfur content is ⁇ 0.5%.
  • the reaction kettle may be a vertical reaction kettle or a horizontal reaction kettle.
  • the heating temperature of the raw materials in the reaction kettle can be 450°C-700°C, and the holding time can be 1h-8h.
  • the rotation speed of the mixer during mixing is ⁇ 500 revolutions/min. If the rotation speed of the mixer is too high, the formed secondary particles will be broken up and become primary particles, so that the scope of S of the present application cannot be achieved. Moreover, the high speed of the mixer will increase the defects on the surface of the material, which will affect the high temperature cycle performance of the battery.
  • the D V 50 of the raw material may be 7 ⁇ m-12 ⁇ m.
  • the D V 50 of the intermediate product 1 may be 11.5 ⁇ m-20.5 ⁇ m.
  • the D V 50 of artificial graphite A may be 9 ⁇ m-17.5 ⁇ m.
  • the proportion of secondary particles in artificial graphite A may be 30%-70%.
  • the graphitization temperature may be 2500°C-3200°C.
  • the green needle-shaped petroleum coke refers to a raw material that has not been calcined at a high temperature (for example, 1000° C.-1500° C.).
  • a high temperature for example, 1000° C.-1500° C.
  • the self-adhesiveness of this kind of raw materials is low, and it is easy to prepare the artificial graphite of primary particles.
  • the rotation speed of the mixer during mixing in step (2) is 500 rpm-1000 rpm, and controlling the rotation speed within the given range is helpful Therefore, the proportion of the secondary particles in the artificial graphite B is less than or equal to 3%.
  • a method known in the art can be used to adjust the required D V 50, D V 90, and D V 99 of artificial graphite B by adjusting the particle size of the raw material.
  • the value of (D v 90-D v 10)/D v 50 may be 5 ⁇ m-10.5 ⁇ m.
  • the treatment temperature of graphitization may be 2500°C-3200°C.
  • the artificial graphite A and the artificial graphite B prepared above are mixed to obtain the artificial graphite of the present application.
  • the mass proportion of artificial graphite A in the artificial graphite may be 40%-75%, and optionally 60%-75%.
  • the intermediate 2 is dried, mixed with pitch and then carbonized, and natural graphite is obtained after sieving.
  • one or more of hydrochloric acid, hydrofluoric acid, and nitric acid may be used to chemically purify the intermediate 1.
  • the tap density of the obtained intermediate 1 is ⁇ 0.6 g/cm 3 .
  • the carbon content of the obtained intermediate 2 is ⁇ 99.9%.
  • the temperature of the carbonization treatment may be 900° C.-1600° C.
  • the time of the carbonization treatment may be 2 h-24 h.
  • the negative electrode active material includes artificial graphite and natural graphite; the artificial graphite includes both primary particles and secondary particles, and the proportion of the number of secondary particles in the negative electrode active material S satisfies: 10% ⁇ S ⁇ 50%.
  • the other parameters of the negative electrode active material prepared by the above method can be controlled in accordance with the aforementioned range to achieve the purpose of further improving the battery performance.
  • the positive electrode active material includes one or more of an olivine structured lithium-containing phosphate and its doped and/or coated modified compounds.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composite material, lithium manganese phosphate, lithium manganese phosphate and carbon composite material, lithium iron manganese phosphate, lithium iron manganese phosphate One or more of the composite materials with carbon and its modified compounds.
  • the lithium-containing phosphate with an olivine structure is selected from one or more of lithium iron phosphate, composite materials of lithium iron phosphate and carbon, and modified compounds thereof.
  • the positive electrode active material includes one or more of olivine structured lithium-containing phosphate and its doped and/or coated modified compounds
  • the negative electrode active material includes both artificial graphite and natural graphite.
  • Graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material, S, satisfies 10% ⁇ S ⁇ 50%.
  • the number of secondary particles in the negative electrode active material S satisfies 15% ⁇ S ⁇ 45%, such as 25% ⁇ S ⁇ 35%, such as 17%, 23%, 25%, 28%, 30% , 32%, 34%, 35%, 42%, can further improve the high temperature cycle performance of the battery.
  • the inventor of the present application has further researched and found that when the positive electrode active material includes one or more of olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, the negative electrode active material includes both artificial graphite and Natural graphite and artificial graphite include both primary particles and secondary particles, and when the number of secondary particles in the negative electrode active material S is within the range given in this application, if the negative electrode active material also optionally satisfies the following conditions One or more of them, the performance of the battery can be further improved.
  • the volume average particle diameter D v 50 of the negative active material is ⁇ 15.0 ⁇ m, and may be 15.0 ⁇ m-19.0 ⁇ m, 16.0 ⁇ m-18.0 ⁇ m, for example, 15.3 ⁇ m, 15.9 ⁇ m, 16.5 ⁇ m, 16.7 ⁇ m, 17.5 ⁇ m, 18.0 ⁇ m, 18.6 ⁇ m, 19.0 ⁇ m.
  • the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range
  • the volume average particle size of the negative electrode active material is adjusted at the same time.
  • the diameter D v 50 is within the given range, the high temperature cycle performance of the battery can be further improved.
  • the volume average particle size D v 50 of the artificial graphite may be 14.0 ⁇ m-19.0 ⁇ m, and may be 14.0 ⁇ m-18.0 ⁇ m. , 15.0 ⁇ m-18.0 ⁇ m, 15.0 ⁇ m-17.0 ⁇ m, for example 15.1 ⁇ m, 15.8 ⁇ m, 16.6 ⁇ m, 17.1 ⁇ m, 18.0 ⁇ m, 18.6 ⁇ m, 18.9 ⁇ m.
  • the volume average particle size D v 50 of natural graphite may be 15.0 ⁇ m-20.0 ⁇ m, and may be 15.0 ⁇ m-19.0 ⁇ m. , 16.0 ⁇ m-19.0 ⁇ m, 16.0 ⁇ m-18.0 ⁇ m, for example 15.4 ⁇ m, 16.5 ⁇ m, 16.8 ⁇ m, 17.7 ⁇ m, 17.9 ⁇ m, 18.2 ⁇ m, 18.5 ⁇ m.
  • the volume distribution particle size D v 90 of the artificial graphite may be 25.0 ⁇ m-37.0 ⁇ m, optionally 27.0 ⁇ m-33.0 ⁇ m .
  • the volume distribution particle size D v 90 of the negative electrode active material may be 25.0 ⁇ m-35.0 ⁇ m, and may be 25.0 ⁇ m-31.0 ⁇ m. .
  • the volume distribution particle diameter D v 99 of the negative active material may be 35.0 ⁇ m-43.0 ⁇ m, and may be 38.0 ⁇ m-40.0 ⁇ m.
  • the positive electrode active material includes one or more of the olivine structure lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range, the D v 99 of the negative electrode active material is adjusted at the same time, When it is within the given range, the dynamic performance and high temperature cycle performance of the battery can be further improved.
  • the volume distribution particle size D v 99 of the artificial graphite may be 38.0 ⁇ m-50.0 ⁇ m, and may be 40.0 ⁇ m-48.0 ⁇ m. .
  • the volume distribution particle size D v 99 of the negative electrode active material may be 30.0 ⁇ m-48.0 ⁇ m, and may be 32.0 ⁇ m-45.0 ⁇ m. .
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative electrode active material may be 1.10-1.30, and may optionally be 1.10-1.25.
  • the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds and S is within the given range
  • the particle size distribution of the negative electrode active material (D When v 90-D v 10)/D v 50 is within the given range, the dynamic performance and high temperature cycle performance of the battery can be further improved.
  • the particle size distribution (D v 90-D v 10)/D v 50 of the negative electrode active material can be 1.25-1.65, and can be 1.35-1.45.
  • the particle size distribution of natural graphite (D v 90-D v 10)/D v 50 can be 0.90-1.30, for example, it can be 1.05-1.25.
  • the proportion of the secondary particles in the artificial graphite is 50%-80%, optionally 60%-75%.
  • the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds and S is within the given range, at the same time, the secondary particles are in the artificial graphite. If the proportion of the number is in an appropriate range, the orientation of the pole pieces after cold pressing can be further improved, which is conducive to the deintercalation of lithium ions, thereby improving the dynamic performance of the secondary battery, and it is also conducive to improving the expansion force during the cycle. Further, the manufacturing process of the negative active material (for example, slurry stirring and filtering) can be improved.
  • the tap density of the negative electrode active material may satisfy ⁇ 1.10 g/cm 3 , and may be 1.00 g/cm 3 -1.09 g/cm 3 .
  • the tap density of the negative electrode active material is adjusted at the same time, Keeping it within the given range can further improve the high temperature cycle performance of the battery.
  • a tap density of artificial graphite may be 0.90g / cm 3 -1.18g / cm 3 , optionally 0.95g / cm 3 -1.15 g/cm 3 .
  • the tap density of natural graphite may be 0.90 g/cm 3 -1.20 g/cm 3 , optionally 0.95 g/cm 3 -1.15 g/cm 3 .
  • the graphitization degree of the negative electrode active material may be 92%-95%, and may be 93%-94%.
  • the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range
  • the graphitization degree of the negative electrode active material is adjusted at the same time Within the given range, the secondary battery can have both higher energy density and better high-temperature cycle performance.
  • the graphitization degree of the artificial graphite may be 90%-95%, optionally 91%-93%.
  • the graphitization degree of natural graphite may be 95%-98%, more optionally 96%-97%.
  • the surface of the artificial graphite does not have a coating layer.
  • the surface of natural graphite has a carbon coating layer.
  • the mass proportion of natural graphite in the negative electrode active material may be ⁇ 30%, and may be 30%-50%, 35%-50%.
  • the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range, natural graphite is also included in the negative electrode active material.
  • the mass ratio of the battery is controlled within the given range, and the battery can take into account both higher energy density and better dynamic performance at the same time.
  • the negative electrode membrane when the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range, the negative electrode membrane
  • the compacted density can be 1.5g/cm 3 -1.7g/cm 3 , more optionally 1.55g/cm 3 -1.6g/cm 3 .
  • the compaction density of the negative electrode membrane is within the above range, which helps The number ratio S of the secondary particles in the negative electrode active material is within the given range, thereby further improving the high temperature cycle life of the battery.
  • the negative electrode membrane when the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doped and/or coated modified compounds, and S is within the given range, the negative electrode membrane
  • the areal density can be 7mg/cm 2 -10mg/cm 2 , optionally 7mg/cm 2 -8mg/cm 2 .
  • the negative electrode when the positive electrode active material includes one or more of the olivine structured lithium-containing phosphate and its doping and/or coating modification compounds, and S is within the given range, the negative electrode
  • the cohesive force F of the diaphragm satisfies: 150N/m ⁇ F ⁇ 250N/m, optionally 180N/m ⁇ F ⁇ 220N/m.
  • the preparation of the negative electrode active material can be based on the preparation method described above, Use methods known in the art to adjust the various parameters of the negative electrode active material to meet the required range, so as to further improve the positive electrode active material, including lithium-containing phosphate with olivine structure and its doping and/or coating modification Compound battery performance.
  • the positive electrode membrane may also optionally include a binder.
  • a binder There is no specific restriction on the type of binder, and those skilled in the art can make a selection according to actual needs.
  • the binder used for the positive electrode membrane may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
  • a conductive agent is optionally included in the positive electrode film.
  • the type of conductive agent is not specifically limited, and those skilled in the art can make a selection according to actual needs.
  • the conductive agent used for the positive electrode film may include one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the electrolyte conducts ions between the positive pole piece and the negative pole piece.
  • the type of electrolyte in this application can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytes).
  • an electrolyte is used as the electrolyte.
  • the electrolyte includes electrolyte salt and solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), and bis-fluorosulfonamide.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiAsF 6 lithium hexafluoroarsenate
  • bis-fluorosulfonamide bis-fluorosulfonamide
  • Lithium Amide Lithium Bistrifluoromethanesulfonimide (LiTFSI), Lithium Trifluoromethanesulfonate (LiTFS), Lithium Difluorooxalate (LiDFOB), Lithium Dioxalate (LiBOB), Lithium Difluorophosphate One or more of (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).
  • 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), ethylene 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) , Ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE) one
  • the electrolyte may also optionally include additives.
  • the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature performance. Additives, etc.
  • the isolation film is arranged between the positive pole piece and the negative pole piece to play a role of isolation.
  • the type of isolation membrane in this application, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multilayer composite film. When the isolation film is a multilayer composite film, the materials of each layer can be the same or different.
  • FIG. 3 shows a secondary battery 5 with a square structure as an example.
  • the secondary battery may include an outer package.
  • the outer packaging is used to encapsulate the positive pole piece, the negative pole piece and the electrolyte.
  • 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 enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and a cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the receiving cavity.
  • the electrolyte may be an electrolyte, and the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 included in the secondary battery 5 can be one or several, which can be adjusted according to requirements.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, or the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a pouch type soft bag.
  • the material of the soft bag may be plastic, for example, it may include one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • the secondary batteries can be assembled into battery modules, 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 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodating space, and a plurality of secondary batteries 5 are accommodated in the accommodating space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • a second aspect of the present application provides a device including the secondary battery of the first aspect of the present application.
  • the secondary battery can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a secondary battery, a battery module, or a battery pack according to its usage requirements.
  • Fig. 8 is a device as an example.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module can be used.
  • the device may be a mobile phone, a tablet computer, a notebook 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 active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the conductive agent Super P, and the binder PVDF are fully stirred and mixed in an appropriate amount of NMP at a mass ratio of 96.5:1.5:2 to form a uniform positive electrode slurry Material; coating the positive electrode slurry on the surface of the positive electrode current collector aluminum foil, after drying and cold pressing, the positive electrode piece is obtained.
  • the areal density of the positive electrode membrane is 17.8 mg/cm 2
  • the compacted density of the positive electrode membrane is 3.4 g/cm 3 .
  • Natural graphite is all primary particles, and the quantity of secondary particles in the negative electrode active material accounts for about S Is 10%.
  • the areal density of the polar membrane can be 11.5 mg/cm 2 .
  • the compacted density of the negative electrode film can be 1.70 g/cm 3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the above-mentioned positive pole piece, separator film, and negative pole piece are stacked and wound in order to obtain an electrode assembly; put the electrode assembly into an outer package, add the electrolyte prepared above, and go through the processes of encapsulation, standing, chemical conversion, and aging After that, a secondary battery was obtained.
  • the preparation method is similar to that in Example 1, except that the relevant parameters in the preparation step of the negative electrode sheet are adjusted. See Tables 1 and 3 for details.
  • the positive electrode active material lithium iron phosphate (LFP), the conductive agent Super P, and the binder PVDF are fully stirred and mixed in an appropriate amount of NMP at a mass ratio of 96.5:1.5:2 to form a uniform positive electrode slurry;
  • the material is coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode pole piece is obtained.
  • the areal density of the positive electrode membrane is 18.1 mg/cm 2
  • the compaction density of the positive electrode membrane is 2.45 g/cm 3 .
  • Natural graphite is all primary particles, and the quantity of secondary particles in the negative electrode active material accounts for about S Is 10%.
  • the areal density of the negative electrode membrane is 8.5 mg/cm 2
  • the compaction density of the negative electrode membrane is 1.60 g/cm 3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the above-mentioned positive pole piece, separator film, and negative pole piece are stacked and wound in order to obtain an electrode assembly; put the electrode assembly into an outer package, add the electrolyte prepared above, and go through the processes of encapsulation, standing, chemical conversion, and aging After that, a secondary battery was obtained.
  • the preparation method is similar to that in Example 8, except that the relevant parameters in the preparation step of the negative electrode sheet are adjusted. See Tables 2 and 4 for details.
  • the battery is disassembled and the interface is observed for lithium evolution. If lithium is not deposited on the surface of the negative electrode, increase the charge rate and perform the test again until lithium is deposited on the surface of the negative electrode. Record the maximum charge rate of undepleted lithium on the surface of the negative electrode to characterize the dynamic performance of the battery.
  • the first charge and discharge performs the first charge and discharge, and perform constant current and constant voltage charging at a charge current of 1.0C (that is, the current value of the theoretical capacity completely discharged within 1h) until the charge cut-off voltage (when the positive electrode
  • the charge cut-off voltage is 4.2V; when the positive electrode active material is lithium iron phosphate, the charge cut-off voltage is 3.65V), and then perform constant current discharge at a discharge current of 1.0C until Discharge cut-off voltage (when the positive electrode active material is lithium nickel cobalt manganese oxide, the discharge cut-off voltage is 2.8V; when the positive electrode active material is lithium iron phosphate, the discharge cut-off voltage is 2.5V), this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is a charge and discharge cycle, this is
  • the discharge capacity at this time is the actual capacity of the battery at 1.0C, denoted as C0.
  • C0 the actual capacity of the battery at 1.0C
  • the secondary battery is subjected to a 100% DOD (100% depth of discharge, that is, fully charged and then fully discharged) 1C0/1C0 charge-discharge cycle in the Xinwei charger and discharge machine.
  • DOD 100% depth of discharge, that is, fully charged and then fully discharged
  • H1 thickness of the corresponding negative pole piece
  • the secondary battery of the examples of the present application adopts a positive electrode active material containing lithium transition metal oxide and artificial graphite and Natural graphite negative electrode active material, artificial graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material S is within a specific range, which enables the secondary battery to have good high-temperature cycle performance at the same time And dynamic performance.
  • Example 3 it can be seen from the comparison results of Example 3 and Example 7 that when the mass ratio of natural graphite in the negative electrode active material meets a specific range, the side reactions during the battery cycle can be significantly reduced, so that Further increase the number of high temperature cycles of the battery.
  • the secondary battery of the examples of the present application adopts a positive electrode active material containing a lithium phosphate containing an olivine structure and
  • the negative electrode active material of artificial graphite and natural graphite, artificial graphite includes both primary particles and secondary particles, and the number of secondary particles in the negative electrode active material S is in a specific range, so that the secondary battery can take into account both High temperature cycle performance and dynamic performance.
  • Example 14 when the mass ratio of natural graphite in the negative electrode active material meets a specific range, the battery can have both high energy density and good power. Learn performance.

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PCT/CN2021/083463 2020-03-27 2021-03-27 二次电池、含有该二次电池的电池模块、电池包及装置 Ceased WO2021190650A1 (zh)

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CN202180007775.XA CN114902450B (zh) 2020-03-27 2021-03-27 二次电池、含有该二次电池的电池模块、电池包及装置
EP21774396.2A EP3961770B1 (en) 2020-03-27 2021-03-27 Secondary battery and battery module, battery pack and apparatus containing the same
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