WO2023206140A1 - 二次电池、电池模块、电池包和用电装置 - Google Patents

二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023206140A1
WO2023206140A1 PCT/CN2022/089563 CN2022089563W WO2023206140A1 WO 2023206140 A1 WO2023206140 A1 WO 2023206140A1 CN 2022089563 W CN2022089563 W CN 2022089563W WO 2023206140 A1 WO2023206140 A1 WO 2023206140A1
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negative electrode
secondary battery
carbon
battery according
lithium
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PCT/CN2022/089563
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English (en)
French (fr)
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王育文
吴益扬
叶永煌
武宝珍
游兴艳
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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 CN202280014078.1A priority Critical patent/CN116888759A/zh
Priority to PCT/CN2022/089563 priority patent/WO2023206140A1/zh
Publication of WO2023206140A1 publication Critical patent/WO2023206140A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and more specifically to secondary batteries, battery modules, battery packs and electrical devices.
  • this application provides a secondary battery, a battery module, a battery pack and a power device, which can improve the energy density of the battery while also providing the battery with fast charging performance and a longer life.
  • this application provides a secondary battery, including:
  • An isolation film disposed between the positive electrode piece and the negative electrode piece
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material in the negative electrode active material layer includes graphite, amorphous carbon and non-carbon negative electrode materials; wherein , the amorphous carbon includes one or more of hard carbon, soft carbon, and porous carbon, and the non-carbon negative electrode material is a silicon-based negative electrode material and/or a tin-based negative electrode material.
  • amorphous carbon since amorphous carbon has a high early lithium insertion potential, it will preferentially lithium insertion, and its expansion rebound is small. Therefore, amorphous carbon is used for high energy density non-carbon negative electrodes such as silicon/tin-based ones.
  • the synergy of the three can not only effectively improve the charging capacity and cycle performance of the silicon/tin-based anode high-energy density system, but also avoid surface particles of the silicon/tin-based anode material caused by fast charging. The fragmentation and battery life decay effectively improve the overall performance of high-energy density systems.
  • the mass percentage of the graphite is x
  • the mass percentage of the amorphous carbon is y
  • the mass percentage of the non-carbon negative material is z ;x, y, z satisfy the following relationship: 0.062x+0.263y ⁇ z ⁇ 1.18x+5y.
  • the x, y, and z satisfy the following relationship: 0.08x+0.4y ⁇ z ⁇ 1x+4y.
  • the value range of y is 5% to 50%.
  • the amounts of graphite, amorphous carbon and non-carbon negative electrode materials are set within an appropriate range, which is crucial to further improving the fast charging, cycle performance and lifespan of the high-energy density system.
  • several materials can synergize, exert their respective advantages, and minimize the impact of the material's own disadvantages on the entire system, complementing each other's advantages, thereby achieving balance and maximization of performance.
  • the lithium insertion capacity of the amorphous carbon in the first charging stage is C 1
  • the lithium insertion capacity of the negative active material during the entire charging process is C sum
  • C 1 /C sum is The value range is 5% to 50%
  • the first charging stage refers to when the lithium insertion potential of the amorphous carbon is greater than the lithium insertion potential of the graphite, and the lithium insertion potential of the amorphous carbon is greater than the lithium insertion potential of the non-carbon negative electrode material. charging stage.
  • the value range of C 1 /C sum is 10% to 35%.
  • the voltage change of amorphous carbon materials during the charging process is relatively large.
  • the lithium insertion potential is greater than that of non-carbon anode materials and graphite materials.
  • the lithium insertion potential is lower than that of non-carbon anode materials and graphite materials, which is close to 0V. interval, during the charging process, materials with larger lithium insertion potential will preferentially absorb lithium. Therefore, controlling the lithium insertion capacity of amorphous carbon in the first charging stage accounts for a certain proportion of the lithium insertion capacity of the negative electrode during the entire charging process.
  • the range can minimize the expansion of the negative electrode material during early high-rate charging, but at the same time, it will not have an obvious negative impact on the system due to the lower energy density and first effect of amorphous carbon materials.
  • the hard carbon includes one or more of resin carbon and carbon black.
  • Hard carbon is pyrolytic carbon of high molecular polymer, which is difficult to graphitize at high temperatures above 2500°C. Hard carbon has a stable structure, long charge and discharge cycle life, and good safety performance. Using hard carbon as the source of amorphous carbon is more conducive to improving the cycle performance and life of the negative electrode.
  • the soft carbon includes one or more of mesocarbon microspheres, coke, and carbon fibers.
  • Soft carbon refers to amorphous carbon that can be graphitized at temperatures ⁇ 2500°C. It has a low and stable charge and discharge potential platform. Using soft carbon as the source of amorphous carbon is more conducive to the charge and discharge capacity and efficiency of the negative electrode. promote.
  • the silicon-based negative electrode material includes one or more of elemental silicon, silicon oxide compounds, silicon nitrogen composites, and silicon alloys.
  • the Dv50 particle size of the graphite ranges from 5 ⁇ m to 25 ⁇ m.
  • the graphitization degree of the graphite is 88% to 99%.
  • the degree of graphitization refers to the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure. The closer the lattice size is to the lattice parameters of ideal graphite, the higher the degree of graphitization.
  • the Dv50 particle size of the amorphous carbon ranges from 2 ⁇ m to 10 ⁇ m.
  • the Dv50 particle size of the non-carbon anode material ranges from 0.05 ⁇ m to 20 ⁇ m.
  • Controlling the particle sizes of several raw materials within a suitable range can make the negative active material of the present application disperse better when it is made into a slurry, making it less likely to agglomerate, and the resulting negative electrode sheet has a more uniform structure and more suitable porosity. The result is better quality.
  • the mass percentage of the negative active material in the negative active material layer is 92% to 99%.
  • the mass percentage of the negative active material in the negative active material layer is specially designed according to the negative active material formula of this application. The mass percentage is controlled within an appropriate range, which can maximize the advantages of the negative active material, thereby The negative electrode piece has better performance and at the same time, the production cost is lower.
  • the thickness of the negative active material layer ranges from 30 ⁇ m to 100 ⁇ m. This thickness refers to the thickness of a single layer of negative active material layer formed on one surface of the current collector, and is also set based on the negative active material formula of this application. A suitable thickness range can make the characteristic thickness of the active material layer account for a higher proportion. , play better performance.
  • the compacted density of the negative electrode piece is 1g/cm 3 to 1.7g/cm 3 . According to the formula of the negative active material of this application, appropriate compaction density can well balance the energy density, charging performance and safety of the pole piece.
  • the negative electrode sheet has a porosity of 20% to 70%.
  • the porosity of the negative electrode piece is 25% to 60%.
  • the porosity of the negative electrode piece is controlled within an appropriate range, which ensures the charging capability without greatly reducing the energy density of the system.
  • the full charge rebound of the negative electrode piece is 20% to 60%. While the negative electrode sheet of the present application has high energy density, its full charge rebound is far lower than that of silicon/tin-based negative electrode materials with high energy density ( ⁇ 100%), effectively avoiding the problem of the outer layer of material particles during the fast charging process.
  • the mismatch between the expansion stress and the expansion stress inside the particles causes particle breakage, thereby avoiding further SEI film (solid electrolyte interface film, solid electrolyte interface) repair and loss of active lithium. Therefore, during the fast charging process, more traditional The high energy density system has lower cycle decay and longer life.
  • the anode potential at the discharge end of the negative electrode piece is ⁇ 0.6V, and the discharge curve has ⁇ 2 voltage platforms.
  • the negative electrode piece produced by this application has a high end anode potential at the discharge point, which allows the anode to fully exert its power during discharge; the discharge curve greater than two voltage platforms enables the amorphous carbon material to be charged according to the predetermined rate during high-rate charging.
  • the designed lithium insertion sequence is orderly lithium insertion, thereby taking advantage of the composite negative active material of the present application and taking into account high energy density, excellent cycle performance and long service life.
  • the positive electrode sheet includes a positive active material and a lithium replenishing agent;
  • the positive active material includes lithium nickel cobalt manganate, lithium manganate, lithium iron phosphate, lithium-rich lithium manganate, and lithium cobalt oxide.
  • the lithium replenishing agent includes Li 7/3 Ti 5/3 O 4 , Li 2.3 Mo 6 S 7.7 , Li 2 NiO2, Li 2 CuO 2 , Li 6 CoO 4 , Li 5 FeO 4 , Li 6 MnO 4 , Li 2 MoO 3 , Li 3 N, Li 2 O, LiOH and one or more of Li 2 CO 3 .
  • the negative electrode plate of this application can be used with a variety of common positive active materials, has a wide range of applications, and can meet various different needs of the market.
  • the introduction of a suitable type of lithium replenishing agent can further enable the battery made of the negative active material of the present application to have higher first efficiency.
  • the ratio N/P of the loading amount of the negative electrode material per unit area to the loading amount of the positive electrode material per unit area in the electrode assembly ranges from 0.99 to 1.2.
  • the N/P ratio enables the negative electrode piece produced in this application to better exert its advantages, and when paired with the positive electrode piece, an electrode assembly with better performance can be produced.
  • the present application provides a battery module, which includes the secondary battery in the above embodiment.
  • the present application provides a battery pack, which includes the battery module in the above embodiment.
  • the present application provides an electrical device, which includes one or more of the secondary battery, battery module, and battery pack in the above embodiments.
  • Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Figure 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in Figure 1;
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG 5 is an exploded view of the battery pack according to an embodiment of the present application shown in Figure 4;
  • Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application
  • Figure 7 is the anode potential at the end of discharge and the discharge curve of the negative electrode piece in the full battery produced in Example 1 of the present application;
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • Graphite is a widely used anode material.
  • the theoretical gram capacity of graphite is only 372mAh/g, which greatly limits the demand for higher energy density.
  • silicon-based and tin-based materials with higher energy density.
  • other anode materials to improve the energy density of graphite anode materials, especially silicon-based anode materials, which are currently the most promising next-generation high-energy-density anode materials.
  • the current silicon/tin-based anode materials have the problem of large expansion and rebound, which causes larger particles of the material to break on the surface during the cycle, causing the surface SEI film (solid electrolyte interface film, solid electrolyte interface) to continue to repair, resulting in Loss of active lithium and rapid capacity fading.
  • the silicon/tin anode material has a higher lithium insertion potential than graphite, in the fast charge test, the silicon/tin anode material will preferentially absorb lithium at high rates, but the conductivity of the silicon/tin material itself is very poor.
  • the lithium insertion inside the material will be very uneven, and most of the lithium insertion will be concentrated on the surface of the particles, resulting in a mismatch between the expansion stress of the outer layer of the particles and the expansion stress inside the particles, thus aggravating the rapid charging process of silicon/tin-based materials.
  • the particles on the surface are broken, which in turn leads to more serious surface SEI repair and loss of active lithium.
  • the cycle attenuation of the silicon/tin-based chemical system will be faster under the fast charging process than under the full cycle process.
  • the overall cycle and storage performance of current silicon-based materials is poor, and it is difficult to meet the current long-life needs. Therefore, how to improve the cycle performance of silicon/tin-based anode high-density energy systems, especially the cycle during fast charging Performance is particularly urgent.
  • this application provides a secondary battery, including:
  • An isolation film disposed between the positive electrode piece and the negative electrode piece
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material in the negative electrode active material layer includes graphite, amorphous carbon and non-carbon negative electrode materials; wherein , amorphous carbon may include one or more of hard carbon, soft carbon, and porous carbon, and the non-carbon negative electrode material may be a silicon-based negative electrode material and/or a tin-based negative electrode material.
  • amorphous carbon since amorphous carbon has a high early lithium insertion potential, it will preferentially lithium insertion, and its expansion rebound is small. Therefore, amorphous carbon is used for high energy density non-carbon negative electrodes such as silicon/tin-based ones.
  • the synergy of the three can not only effectively improve the charging capacity and cycle performance of the silicon/tin-based anode high-energy density system, but also avoid surface particles of the silicon/tin-based anode material caused by fast charging. The fragmentation and battery life decay effectively improve the overall performance of high-energy density systems.
  • the mass percentage of graphite is x
  • the mass percentage of amorphous carbon is y
  • the mass percentage of non-carbon negative electrode material is z
  • x, y, and z satisfy the following Relationship: 0.062x+0.263y ⁇ z ⁇ 1.18x+5y.
  • x, y, and z satisfy the following relationship: 0.08x+0.4y ⁇ z ⁇ 1x+4y.
  • the value of y ranges from 5% to 50%. Furthermore, the value range of y may be, for example, 12% to 38%. The value of y can also be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%.
  • the amounts of graphite, amorphous carbon and non-carbon negative electrode materials are set within an appropriate range, which is crucial to further improving the fast charging, cycle performance and lifespan of the high-energy density system.
  • several materials can synergize, exert their respective advantages, and minimize the impact of the material's own disadvantages on the entire system, complementing each other's advantages, thereby achieving balance and maximization of performance.
  • the lithium insertion capacity of amorphous carbon in the first charging stage is C 1
  • the lithium insertion capacity of the negative active material during the entire charging process is C sum
  • the value range of C 1 /C sum is 5 % ⁇ 50%
  • the first charging stage refers to the charging stage when the lithium insertion potential of amorphous carbon is greater than the lithium insertion potential of graphite, and the lithium insertion potential of amorphous carbon is greater than the lithium insertion potential of the non-carbon negative electrode material.
  • C 1 /C sum ranges from 10% to 35%. Controlling the value of C 1 /C sum within the optimal range can make the battery have better fast charging performance, longer life, and smaller full-charge rebound.
  • the value of C 1 /C sum may also be, for example, 8%, 12%, 16%, 20%, 24%, 28%, 32%, 36%, 40%, 44% or 48%. .
  • the voltage change of amorphous carbon materials during the charging process is relatively large.
  • the lithium insertion potential is greater than that of non-carbon anode materials and graphite materials.
  • the lithium insertion potential is lower than that of non-carbon anode materials and graphite materials, which is close to 0V. interval, during the charging process, materials with larger lithium insertion potential will preferentially absorb lithium. Therefore, controlling the lithium insertion capacity of amorphous carbon in the first charging stage accounts for a certain proportion of the lithium insertion capacity of the negative electrode during the entire charging process.
  • the range can minimize the expansion of the negative electrode material during early high-rate charging, but at the same time, it will not have an obvious negative impact on the system due to the lower energy density and first effect of amorphous carbon materials.
  • the hard carbon includes one or more of resinous carbon and carbon black.
  • Hard carbon is pyrolytic carbon of polymers, which is difficult to graphitize at temperatures ⁇ 2500°C. Hard carbon has a stable structure, long charge and discharge cycle life, and good safety performance. Using hard carbon as the source of amorphous carbon is more conducive to improving the cycle performance and life of the negative electrode.
  • the soft carbon includes one or more of mesocarbon microspheres, coke, and carbon fibers.
  • Soft carbon refers to amorphous carbon that can be graphitized at high temperatures above 2500°C. It has a low and stable charge and discharge potential platform. Using soft carbon as the source of amorphous carbon is more conducive to the charge and discharge capacity and efficiency of the negative electrode. promote.
  • the silicon-based negative electrode material includes one or more of elemental silicon, silicon oxide compounds, silicon nitrogen composites, and silicon alloys.
  • the graphite has a Dv50 particle size ranging from 5 ⁇ m to 25 ⁇ m.
  • Dv50 refers to the particle size corresponding to 50% of the particles in the volume distribution.
  • the Dv50 particle size of graphite may also be, for example, 10 ⁇ m, 15 ⁇ m, or 20 ⁇ m.
  • the graphitization degree of the graphite is 88% to 99%.
  • the degree of graphitization refers to the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure. The closer the lattice size is to the lattice parameters of ideal graphite, the higher the degree of graphitization.
  • the degree of graphitization of graphite may also be, for example, 90%, 92%, 94%, 96% or 98%.
  • the amorphous carbon has a Dv50 particle size ranging from 2 ⁇ m to 10 ⁇ m.
  • the Dv50 particle size of amorphous carbon may be, for example, 4 ⁇ m, 6 ⁇ m, or 8 ⁇ m.
  • the Dv50 particle size of the non-carbon anode material ranges from 0.05 ⁇ m to 20 ⁇ m.
  • the Dv50 particle size of the amorphous carbon may be, for example, 2 ⁇ m, 4 ⁇ m, 6 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 14 ⁇ m, 16 ⁇ m, or 18 ⁇ m.
  • Controlling the particle sizes of several raw materials within a suitable range can make the negative active material of the present application disperse better when it is made into a slurry, making it less likely to agglomerate, and the resulting negative electrode sheet has a more uniform structure and more suitable porosity. The result is better quality.
  • the graphite, amorphous carbon and non-carbon negative electrode materials in this application can all be primary particles, secondary particles, or a mixture of primary particles or secondary particles.
  • the mass percentage of the negative active material in the negative active material layer is 92% to 99%.
  • the mass percentage of the negative active material in the negative active material layer is specially designed according to the negative active material formula of this application. The mass percentage is controlled within an appropriate range, which can maximize the advantages of the negative active material, thereby making the negative electrode The chip has better performance and at the same time, the production cost is lower.
  • the mass percentage of the negative active material in the negative active material layer may be, for example, 93%, 94%, 95%, 96%, 97% or 98%.
  • the thickness of the negative active material layer ranges from 30 ⁇ m to 100 ⁇ m. This thickness refers to the thickness of a single layer of negative active material layer formed on one surface of the current collector, and is also set based on the negative active material formula of this application. A suitable thickness range can make the characteristic thickness of the active material layer account for a higher proportion. , play better performance.
  • the thickness of the negative active material layer may be, for example, 52 ⁇ m to 88 ⁇ m, or may be 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, 65 ⁇ m, 70 ⁇ m, 75 ⁇ m, 80 ⁇ m, 85 ⁇ m, 90 ⁇ m, or 95 ⁇ m. .
  • the compacted density of the negative electrode piece is 1g/cm 3 to 1.7g/cm 3 . According to the formula of the negative active material of this application, appropriate compaction density can well balance the energy density, charging performance and safety of the pole piece.
  • the compacted density of the negative electrode sheet may be, for example, 1.28g/cm 3 to 1.48g/cm 3 , or may also be 1.05g/cm 3 , 1.1g/cm 3 , or 1.15g/cm 3 , 1.2g/cm 3 , 1.25g/cm 3 , 1.3g /cm 3 , 1.35g/cm 3 , 1.4g/cm 3 , 1.45g/cm 3 , 1.5g/cm 3 , 1.55g/cm 3 , 1.6 g/cm 3 or 1.65g/cm 3 .
  • the negative electrode sheet has a porosity of 20% to 70%.
  • the negative electrode sheet has a porosity of 25% to 60%.
  • the porosity of the negative electrode sheet may be, for example, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44% , 46%, 48%, 50%, 52%, 54%, 56% or 58%.
  • the porosity of the negative electrode piece is controlled within an appropriate range, which ensures the charging capability without greatly reducing the energy density of the system.
  • the full charge rebound of the negative electrode piece is 20% to 60%.
  • the full-charge rebound of the negative electrode piece may be, for example, 22% to 48%, or may be 25%, 30%, 35%, 40%, 45%, 50% or 55%.
  • the negative electrode sheet of the present application has high energy density, its full charge rebound is far lower than that of silicon/tin-based negative electrode materials with high energy density ( ⁇ 100%), effectively avoiding the problem of the outer layer of material particles during the fast charging process.
  • the mismatch between the expansion stress and the expansion stress inside the particles causes particle breakage, thus avoiding further SEI film repair and loss of active lithium. Therefore, during the fast charging process, it has a lower cycle time than the traditional high energy density system. decay and longer life.
  • the anode potential at the discharge end of the negative electrode piece is ⁇ 0.6V, and the discharge curve has ⁇ 2 voltage platforms. Further, the anode potential at the end of the negative electrode piece is ⁇ 1.0V.
  • the negative electrode piece produced by this application has a high end anode potential at the discharge point, which allows the anode to fully exert its power during discharge; the discharge curve greater than two voltage platforms enables the amorphous carbon material to be charged according to the predetermined rate during high-rate charging.
  • the designed lithium insertion sequence is orderly lithium insertion, thereby taking advantage of the composite negative active material of the present application and taking into account high energy density, excellent cycle performance and long service life.
  • the positive electrode sheet includes a positive active material and a lithium replenishing agent; the positive active material may include one of lithium nickel cobalt manganate, lithium manganate, lithium iron phosphate, lithium-rich lithium manganate, and lithium cobalt oxide.
  • the lithium supplement can include Li 7/3 Ti 5/3 O 4 , Li 2.3 Mo 6 S 7.7 , Li 2 NiO2, Li 2 CuO 2 , Li 6 CoO 4 , Li 5 FeO 4 , Li 6 MnO 4.
  • Li 2 MoO 3 Li 3 N, Li 2 O, LiOH and Li 2 CO 3 .
  • the negative electrode plate of this application can be used with a variety of common positive active materials, has a wide range of applications, and can meet various different needs of the market.
  • the introduction of a suitable type of lithium replenishing agent can further enable the battery made of the negative active material of the present application to have higher first efficiency.
  • the ratio N/P of the loading amount of the negative electrode material per unit area to the loading amount of the positive electrode material per unit area ranges from 0.99 to 1.2.
  • the N/P ratio enables the negative electrode piece produced in this application to better exert its advantages, and when paired with the positive electrode piece, a secondary battery with better performance can be produced.
  • the secondary battery further includes an electrolyte.
  • an electrolyte there is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the above-mentioned preparation method of the negative electrode sheet includes the following steps:
  • negative electrode slurry Mix the negative active material, solvent and optional additives to prepare negative electrode slurry; apply the negative electrode slurry on at least one surface of the negative electrode current collector, dry and press;
  • the auxiliary agent includes one or more of a binder, a dispersant and a conductive agent.
  • the negative active material of this application does not require special treatment. It can be simply mixed with raw materials such as additives and solvents to prepare negative electrode slurry, and then the negative electrode sheet can be prepared by coating, drying and pressing using conventional processes. The preparation method is simple and easy for large-scale industrial production.
  • the binder is selected from one or more of polystyrene butadiene, polyvinylidene fluoride, polyacrylic acid, polyacrylonitrile, polyvinyl alcohol (PVA), carboxymethyl chitosan and sodium alginate. kind.
  • the mass percentage of the binder in the negative electrode slurry is 0.5% to 5%.
  • the dispersant is selected from one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose and PTC thermistor material.
  • the mass percentage of the dispersant in the negative electrode slurry is 0% to 3%.
  • the conductive agent is selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and porous carbon materials.
  • the mass percentage of the conductive agent in the negative electrode slurry is 0% to 4%.
  • the present application provides a battery module, which includes the secondary battery in the above embodiment.
  • the present application provides a battery pack, which includes the battery module in the above embodiment.
  • the present application provides an electrical device, which includes one or more of the secondary battery, battery module, and battery pack in the above embodiments.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material adopts the negative active material included in any embodiment of the present application.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the electrode assembly includes a separation film between the positive electrode piece and the negative electrode piece.
  • the secondary battery further includes a separator film, and the separator film is located between the positive electrode piece and the negative electrode piece.
  • isolation membrane there is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and secondary batteries can be used as the power source.
  • the electrode piece is dried in an oven and then rolled on a cold pressing roller.
  • the negative electrode slurry is compacted to obtain a negative electrode sheet.
  • the thickness of the single-sided negative electrode active material layer formed after drying and compacting the above negative electrode slurry is 75 ⁇ m.
  • the compacted density of the negative electrode sheet is 1.3g/cm 3 . Porosity 45%;
  • the particle size Dv50 of the above-mentioned artificial graphite is 14 ⁇ m, and the degree of graphitization is 95%; the particle size Dv50 of hard carbon is 5 ⁇ m, and the Dv50 of prelithiated SiOx is 8 ⁇ m.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the obtained electrolyte is subjected to conventional processes such as packaging, standing, formation, and aging to obtain a secondary battery.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 9.61: 72.075: 14.415: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 88 ⁇ m
  • the compacted density of the negative electrode sheet is 1.1 g/cm 3
  • the porosity of the negative electrode sheet is 42%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 72.075: 9.61: 14.415: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 65 ⁇ m
  • the compacted density of the negative electrode sheet is 1.5 g/cm 3
  • the porosity of the negative electrode sheet is 32%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethylcellulose is 78.802:9.61:7.688:0.2:0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 63 ⁇ m
  • the compacted density of the negative electrode sheet is 1.55g/cm 3
  • the porosity of the negative electrode sheet is 30%.
  • Example 2 It is basically the same as Example 1, except that the amorphous carbon in the negative active material is soft carbon.
  • Example 2 It is basically the same as Example 1. The difference is that Li 2 NiO 2 lithium replenishing agent is added to the positive electrode sheet in this example, and the N/P ratio is 1.05.
  • the mass ratio of natural graphite: porous carbon material: tin-based negative electrode: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethylcellulose is 72.075:19.22:4.805:0.2:0.5:2 :1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 57 ⁇ m
  • the compacted density of the negative electrode sheet is 1.7g/cm 3
  • the porosity of the negative electrode sheet is 28%
  • the particle size Dv50 of the above-mentioned natural graphite is 20 ⁇ m, and the graphitization degree is 95%; the particle size Dv50 of the porous carbon is 6 ⁇ m, and the Dv50 of the tin-based negative electrode material is 10 ⁇ m;
  • the cathode material is lithium-rich manganese-based lithium manganate.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 89.5: 4.6: 2: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 63 ⁇ m
  • the compacted density of the negative electrode sheet is 1.55g/cm 3
  • the porosity of the negative electrode sheet is 20%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 14.415: 43.245: 38.44: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 63 ⁇ m
  • the compacted density of the negative electrode sheet is 1.55g/cm 3
  • the porosity of the negative electrode sheet is 70%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 72.075: 4.805: 19.22: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 63 ⁇ m
  • the compacted density of the negative electrode sheet is 1.55g/cm 3
  • the porosity of the negative electrode sheet is 23%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 9.61: 81.685: 4.805: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 97 ⁇ m
  • the compacted density of the negative electrode sheet is 1 g/cm 3
  • the porosity of the negative electrode sheet is 34%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 81.685: 4.805: 9.61: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 63 ⁇ m
  • the compacted density of the negative electrode sheet is 1.55g/cm 3
  • the porosity of the negative electrode sheet is 22%.
  • composition of the negative active material is:
  • the mass ratio of artificial graphite: hard carbon: prelithiated SiOx: conductive agent sp: carbon nanotube: binder styrene-butadiene rubber: thickener sodium carboxymethyl cellulose is 4.805: 86.49: 4.805: 0.2: 0.5: 2:1.2;
  • the thickness of the negative active material layer formed after drying and compacting the negative electrode slurry is 97 ⁇ m
  • the compacted density of the negative electrode sheet is 1 g/cm 3
  • the porosity of the negative electrode sheet is 32%.
  • Example 6 It is basically the same as Example 6, except that the dosage of lithium supplement is adjusted so that the N/P ratio is 0.98.
  • Example 6 It is basically the same as Example 6, except that the dosage of lithium supplement is adjusted so that the N/P ratio is 1.25.
  • Diaphragm thickness In this application, the thickness of the negative electrode diaphragm has a well-known meaning in the art, and can be measured using methods known in the art, such as a micrometer (such as Mitutoyo 293-100 type, accuracy is 0.1 ⁇ m).
  • Double-layer coating film thickness In this application, the respective thicknesses of the first negative electrode film layer and the second negative electrode film layer can be tested by using a scanning electron microscope (such as ZEISS Sigma 300).
  • the sample preparation is as follows: first, cut the negative electrode piece into a sample to be tested of a certain size (for example, 2cm ⁇ 2cm), and fix the negative electrode piece on the sample stage through paraffin wax.
  • the sample stage into the sample rack and lock it, turn on the power and vacuum (for example 10 -4 Pa) of the argon ion cross-section polisher (for example IB-19500CP), set the argon flow rate (for example 0.15MPa) and voltage (for example 8KV) and polishing time (for example, 2 hours), adjust the sample stage to rocking mode and start polishing.
  • the argon flow rate for example 0.15MPa
  • voltage for example 8KV
  • polishing time for example, 2 hours
  • Mass proportion of silicon-based material in this application, has a meaning known in the art, and can be tested using methods known in the art. For example, use a scanning electron microscope (such as ZEISS Sigma 300) to observe the cross section of the negative electrode diaphragm (such as the cross section in the thickness direction of the diaphragm), and use energy dispersive X-ray analysis (such as ZEISS Sigma 300's own energy spectrometer) for quantitative mapping. From this, the element content of the negative electrode membrane was measured at the scanning position of the cross section, and the element distribution was obtained. In a region within the cross section, the Si content in the region can be obtained by integrating the Si element distribution. In order to improve the accuracy of the test, the test results of multiple areas (for example, 10) can be counted and averaged.
  • ZEISS Sigma 300 scanning electron microscope
  • energy dispersive X-ray analysis such as ZEISS Sigma 300's own energy spectrometer
  • the particle size of the silicon-based material is a meaning known in the art and can be tested using methods known in the art. For example, a scanning electron microscope (such as ZEISS Sigma 300) can be used for testing.
  • the sample preparation is as follows: first, cut the negative electrode piece into a sample to be tested of a certain size (for example, 2cm ⁇ 2cm), and fix the negative electrode piece on the sample stage through paraffin wax.
  • the sample stage into the sample rack and lock it, turn on the power and vacuum (for example 10 -4 Pa) of the argon ion cross-section polisher (for example IB-19500CP), set the argon flow rate (for example 0.15MPa) and voltage (for example 8KV) and polishing time (for example, 2 hours), adjust the sample stage to rocking mode and start polishing.
  • the argon flow rate for example 0.15MPa
  • voltage for example 8KV
  • polishing time for example, 2 hours
  • the Dv50 of the negative active material is a meaning known in the art, and can be measured using instruments and methods known in the art. For example, refer to the standard GB/T 19077.1-2016 and use a laser particle size analyzer (such as Malvern Master Size 3000) to measure. Wherein, D v 50 is the particle size corresponding to when the cumulative volume distribution percentage of the negative active material reaches 50%.
  • the compacted density of the negative electrode membrane has a well-known meaning in the art, and can be tested using methods known in the art.
  • the compacted density of the negative electrode diaphragm the area density of the negative electrode diaphragm/the thickness of the negative electrode diaphragm.
  • the batteries of the above-mentioned embodiments and comparative examples were charged and discharged for the first time with a current of 1C (that is, the current value that completely discharges the theoretical capacity within 1 hour), specifically including: charging the battery with a constant current at a rate of 1C. to a voltage of 4.25V, then charge at a constant voltage until the current is ⁇ 0.05C, let it sit for 5 minutes, and then discharge at a constant current of 0.33C to a voltage of 2.5V, and record its actual capacity as C0.
  • a current of 1C that is, the current value that completely discharges the theoretical capacity within 1 hour
  • the charging rate is The charging window in this SOC state is recorded as C10%SOC, C20%SOC, C30%SOC, C40%SOC, C50%SOC, C60%SOC, C70%SOC, C80%SOC, according to the formula (60/C20% SOC+60/C30%SOC+60/C40%SOC+60/C50%SOC+60/C60%SOC+60/C70%SOC+60/C80%SOC) ⁇ 10% calculates that the battery is charged from 10% SOC Charging time T to 80% SOC, unit is min. The shorter the time, the better the battery's fast charging performance.
  • the secondary batteries prepared in each Example and Comparative Example were charged at a constant current rate of 1C to a charge cutoff voltage of 4.25V, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then charged at a constant current rate of 1C. Discharge to the discharge cut-off voltage of 2.5V and let it sit for 5 minutes. This is a charge and discharge cycle.
  • This method to perform a cycle charge and discharge test on the battery until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery at 25°C.
  • N/P Prepare the cathode and anode plates with lithium plates respectively into button-type half-cells, conduct charge and discharge tests at a rate of 0.04C, and obtain the first charge capacity of the cathode plate and the anode plate respectively.
  • the first charging capacity in grams, in which the charging cut-off voltage of the cathode plate button half-cell is 4.3V and the discharge cut-off voltage is 2.5V; the charging cut-off voltage of the anode plate button half-cell is 1.2V and the discharge cut-off voltage is 0V.
  • (10) Energy density Test the volume of the battery core.
  • Square shell batteries can be calculated by the dimensions of length, width and height, cylindrical batteries can be calculated by height and diameter, and soft-packed batteries can obtain the volume of the battery core through the drainage method; Then charge and discharge through the charging and discharging equipment at 25°C and 0.33C, record the discharge energy, and divide the discharge energy by the volume of the battery core to obtain the volumetric energy density of the battery core;
  • Comparative Example 1 Compared with Example 1, the y value in Comparative Example 1 is too small, resulting in C 1 /C sum being too small, and the cycle performance, energy density and fast charging performance are significantly reduced; in Comparative Example 2, the y value is too large, resulting in serious cycle performance decreases, and the full charge rebound increases significantly; in Comparative Example 3, the z value is too small, lower than the lower limit of 0.062x+0.263y, resulting in C 1 /C sum being too small, fast charging performance declining, energy density and number of cycles It has also declined, and the full-charge rebound has increased; in Comparative Example 4, the z value is too large, higher than the upper limit of 1.18x+5y.

Abstract

一种二次电池（5），其包括：正极极片、负极极片和隔离膜，隔离膜设置于正极极片和负极极片之间；负极极片包括负极集流体以及设置于负极集流体至少一个表面的负极活性材料层，负极活性材料层中的负极活性材料包括石墨、无定形碳和非碳负极材料；其中，无定形碳包括硬碳、软碳以及多孔碳中的一种或多种，非碳负极材料为硅基负极材料和/或锡基负极材料。

Description

二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及二次电池技术领域，更具体地涉及二次电池、电池模块、电池包和用电装置。
背景技术
这里的陈述仅提供与本申请有关的背景信息，而不必然构成现有技术。
随着新能源汽车的快速发展，客户和市场对于锂离子电池能量密度的要求越来越高，尤其是为了跟当前的燃油车市场进行竞争，必须进一步提升能量密度。
然而，目前市场上具备高能量密度的电池往往在充电能力方面不具备好的表现，在快速充电过程中容易出现循环衰减等问题，且也难以具备较长的使用寿命。
发明内容
鉴于上述问题，本申请提供了一种二次电池、电池模块、电池包和用电装置，能够在提高电池能量密度的同时，使电池具备快速充电性能，并具有较长寿命。
第一方面，本申请提供了一种二次电池，包括：
正极极片；
负极极片；
隔离膜，设置于所述正极极片和所述负极极片之间；
所述负极极片包括负极集流体以及设置于所述负极集流体至少一个表面的负极活性材料层，所述负极活性材料层中的负极活性材料包括石墨、无定形碳和非碳负极材料；其中，所述无定形碳包括硬碳、软碳以及多孔碳中的一种或多种，所述非碳负极材料为硅基负极材料和/或锡基负极材料。
本申请实施例的技术方案中，由于无定形碳的前期嵌锂电位高，会优先嵌锂，且膨胀反弹小，因此，将无定形碳用于硅/锡基等非碳的负极高能量密度体系中，并辅以石墨材料，三者协同作用，不仅能有效改善硅/锡基负极高能量密度体系的充电能力和循环性能，并避免了因为快充造成的硅/锡基负极材料表面颗粒破碎和电池的寿命衰减，有效提升了高能密度体系的综合性能。
在一些实施例中，所述负极活性材料中，所述石墨的质量百分含量为x，所述无 定形碳的质量百分含量为y，所述非碳负极材料的质量百分含量为z；x、y、z满足如下关系：0.062x+0.263y≤z≤1.18x+5y。
在一些实施例中，所述x、y、z满足如下关系：0.08x+0.4y≤z≤1x+4y。
在一些实施例中，所述x、y、z满足以下关系：x+y+z＝1。
在一些实施例中，所述y的取值范围为5％～50％。
本申请实施例的技术方案中，石墨、无定形碳和非碳负极材料的用量设定在合适的范围内，对能否更好地进一步提升高能密度体系的快充、循环性能以及寿命至关重要，在预设范围内，几种材料能够协同增效，发挥各自优势的同时，且尽可能地减小材料自身的劣势对整个体系的影响，优势互补，从而实现性能的平衡和最大化。
在一些实施例中，所述无定形碳在第一充电阶段内的嵌锂容量为C 1，所述负极活性材料在整个充电过程中的嵌锂容量为C sum，C 1/C sum的取值范围为5％～50％；
其中，所述第一充电阶段是指所述无定形碳的嵌锂电位大于所述石墨的嵌锂电位，且所述无定形碳的嵌锂电位大于所述非碳负极材料的嵌锂电位时的充电阶段。
在一些实施例中，所述C 1/C sum的取值范围为10％～35％。
无定形碳材料在充电过程中的电压变化比较大，有前期嵌锂电位均大于非碳负极材料和石墨材料的区间，也有后期较长一段低于非碳负极材料和石墨材料接近0V的嵌锂区间，在充电过程中，嵌锂电位较大的材料会优先嵌锂，因此，控制无定形碳在第一充电阶段内的嵌锂容量在整个充电过程中负极嵌锂容量中的占比为一定范围，可以尽可能地减少前期大倍率充电时负极材料的膨胀，但同时又不会因为无定形碳材料较低的能量密度和首效对体系造成明显的负面影响。
在一些实施例中，所述硬碳包括树脂碳以及炭黑中的一种或多种。硬碳是高分子聚合物的热解碳，其在2500℃以上的高温也难以石墨化。硬碳结构稳定且充放电循环寿命长、安全性能好，采用硬碳作为无定形碳来源，更有利于负极的循环性能以及寿命的提升。
在一些实施例中，所述软碳包括中间相炭微球、焦炭以及碳纤维中的一种或多种。软碳是指在≥2500℃的温度下能石墨化的无定型碳，其具有较低且平稳的充放电电位平台，采用软碳作为无定形碳来源，更有利于负极充放电容量和效率的提升。
在一些实施例中，所述硅基负极材料包括单质硅、硅氧化合物、硅氮复合物以及硅合金中的一种或多种。
在一些实施例中，所述石墨的Dv50粒径范围为5μm～25μm。
在一些实施例中，所述石墨的石墨化度为88％～99％。石墨化度是指碳原子形成密排六方石墨晶体结构的程度，其晶格尺寸越接近理想石墨的点阵参数，石墨化度就越高。通过控制石墨材料需具有一定的石墨化度，可赋予负极材料更高的性能，使本申请的负极活性材料制得的电池具有更大的容量。
在一些实施例中，所述无定形碳的Dv50粒径范围为2μm～10μm。
在一些实施例中，所述非碳负极材料的Dv50粒径范围为0.05μm～20μm。
控制几种原料的粒径在合适范围内，能使得本申请的负极活性材料制成浆料时分散更好，不易团聚，且制得的负极极片结构更均匀、具有更合适的孔隙率，从而品质更优。
在一些实施例中，所述负极活性材料在所述负极活性材料层中的质量百分比为92％～99％。负极活性材料在负极活性材料层中的质量百分占比是特别根据本申请的负极活性材料配方设计的，质量百分占比控制在合适范围内，能使得负极活性材料最大限度发挥优势，从而使负极极片具有更佳的性能，同时，生产成本更低。
在一些实施例中，所述负极活性材料层的厚度为30μm～100μm。该厚度是指在集流体的一个表面形成的单层负极活性材料层的厚度，也是基于本申请的负极活性材料配方设定的，合适的厚度范围能使得活性材料层的特征厚度占比更高，发挥更好的性能。
在一些实施例中，所述负极极片的压实密度为1g/cm 3～1.7g/cm 3。根据本申请的负极活性材料的配方，合适的压实密度能够很好地平衡极片的能量密度、充电性能与安全性。
在一些实施例中，所述负极极片的孔隙率为20％～70％。
在一些实施例中，所述负极极片的孔隙率为25％～60％。负极极片的孔隙率控制在合适范围内，保障了充电能力的同时，不会过大地降低体系的能量密度。
在一些实施例中，所述负极极片的满充反弹为20％～60％。本申请的负极极片在具备高能量密度的同时，满充反弹远远低于硅/锡基等高能量密度的负极材料(≥100％)，有效避免了由于快速充电过程中材料颗粒外层的膨胀应力与颗粒内部的膨胀应力不匹配导致的颗粒破碎，进而避免了进一步的SEI膜(固体电解质界面膜，solid electrolyte interface)修复和活性锂的损失，因此，在快充过程中，较传统的高能量密度体系具备更低的循环衰减和更长的寿命。
在一些实施例中，所述负极极片的放电末端阳极电位≥0.6V，放电曲线≥2个电 压平台。本申请制得的负极极片具有较高的放点末端阳极电位，这使得阳极在放电时电量能够得以充分发挥；大于两个电压平台的放电曲线使得大倍率充电时无定形碳材料能按照预设的嵌锂顺序有序嵌锂，从而发挥本申请复合负极活性材料的优势，兼顾高能量密度、优秀的循环性能以及较长的使用寿命。
在一些实施例中，所述正极极片中包括正极活性物质和补锂剂；所述正极活性物质包括镍钴锰酸锂、锰酸锂、磷酸铁锂、富锂锰酸锂以及钴酸锂中的一种或多种，所述补锂剂包括Li 7/3Ti 5/3O 4、Li 2.3Mo 6S 7.7、Li 2NiO2、Li 2CuO 2、Li 6CoO 4、Li 5FeO 4、Li 6MnO 4、Li 2MoO 3、Li 3N、Li 2O、LiOH以及Li 2CO 3中的一种或多种。本申请的负极极片可以搭配多种常见的正极活性材料使用，适用范围广，能满足市场多种不同需求。合适种类的补锂剂的引入可以进一步使得本申请的负极活性材料制得的电池具备更高的首效。
在一些实施例中，所述电极组件中单位面积负极材料的负载量与单位面积正极材料的负载量的比值N/P的取值范围为0.99～1.2。N/P比能使得本申请制得的负极极片更好地发挥其优势，与正极极片搭配，制得性能更优异的电极组件。
第二方面，本申请提供了一种电池模块，其包括上述实施例中的二次电池。
第三方面，本申请提供了一种电池包，其包括上述实施例中的电池模块。
第四方面，本申请提供了一种用电装置，其包括上述实施例中的二次电池、电池模块以及电池包中的一种或多种。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明这里公开的那些申请的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的电池模块的示意图；
图4是本申请一实施方式的电池包的示意图；
图5是图4所示的本申请一实施方式的电池包的分解图；
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图；
图7是本申请实施例1制得的全电池中负极极片的放电末端阳极电位以及放电曲线；
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
以下，适当地参照附图详细说明具体公开了本申请的负极活性材料、负极极片及其制备方法、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。 另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
由于现实存在的石油资源短缺问题，以及可持续发展观念的深入人心，多个领域都致力于寻找适用于该领域的新能源以替代传统的石油。作为石油化工产品消耗大户的燃油车由于工艺成熟、零部件造价相对较低，且具有长里程的行驶能力，依然占据整个机动车行业的主流地位，因此，为了使得新能源汽车，如电动汽车，能切实地与燃油车具备竞争价值，具备高能量密度、长使用寿命和优异的充电和循环性能的锂离子电池亟待被开发。
石墨是被广泛使用的负极材料，然而，由于石墨的理论克容量仅372mAh/g，大大限制了更高能量密度的需求；为了进一步提升能量密度，需要引入更高能量密度的硅基、锡基等负极材料对石墨负极材料的能量密度进行改善，尤其是硅基负极材料，是当前最有希望的下一代高能量密度负极材料。然而，目前的硅/锡基负极材料存在膨胀反弹大的问题，这导致循环过程中材料的较大颗粒在表面破碎，引起表面SEI膜(固体电解质界面膜，solid electrolyte interface)的持续修复，导致活性锂的损失和容量的快速衰减。同时，由于硅/锡负极材料相对于石墨的嵌锂电位更高，因此在快充测试中，硅/锡负极材料会优先在大倍率下嵌锂，但硅/锡材料本身的导电性很差，因此，材料内 部嵌锂会非常不均匀，大部分会集中在颗粒表面进行嵌锂，导致颗粒外层的膨胀应力和颗粒内部的膨胀应力不匹配，从而加剧快速充电过程中硅/锡基材料表面的颗粒破碎，进而引发更加严重的表面SEI修复和活性锂的损失，导致在快充流程下，硅/锡基化学体系的循环衰减会较满循环流程下循环衰减更快。概言之，当前硅基材料的循环和存储性能整体较差，较难满足当前长寿命的需求，因此，如何提升硅/锡基负极高密度能量体系的循环性能，特别是快速充电时的循环性能，显得尤为迫切。
基于此，第一方面，本申请提供了一种二次电池，包括：
正极极片；
负极极片；
隔离膜，设置于所述正极极片和所述负极极片之间；
所述负极极片包括负极集流体以及设置于所述负极集流体至少一个表面的负极活性材料层，所述负极活性材料层中的负极活性材料包括石墨、无定形碳和非碳负极材料；其中，无定形碳可以包括硬碳、软碳以及多孔碳中的一种或多种，非碳负极材料可以为硅基负极材料和/或锡基负极材料。
本申请实施例的技术方案中，由于无定形碳的前期嵌锂电位高，会优先嵌锂，且膨胀反弹小，因此，将无定形碳用于硅/锡基等非碳的负极高能量密度体系中，并辅以石墨材料，三者协同作用，不仅能有效改善硅/锡基负极高能量密度体系的充电能力和循环性能，并避免了因为快充造成的硅/锡基负极材料表面颗粒破碎和电池的寿命衰减，有效提升了高能密度体系的综合性能。
在一些实施例中，负极活性材料中，石墨的质量百分含量为x，无定形碳的质量百分含量为y，非碳负极材料的质量百分含量为z；x、y、z满足如下关系：0.062x+0.263y≤z≤1.18x+5y。
在一些实施例中，x、y、z满足如下关系：0.08x+0.4y≤z≤1x+4y。
在一些实施例中，x、y、z满足以下关系：x+y+z＝1。
在一些实施例中，y的取值范围为5％～50％。进一步地，y的取值范围例如可以是12％～38％。y的取值例如还可以是10％、15％、20％、25％、30％、35％、40％或45％。
本申请实施例的技术方案中，石墨、无定形碳和非碳负极材料的用量设定在合适的范围内，对能否更好地进一步提升高能密度体系的快充、循环性能以及寿命至关重要，在预设范围内，几种材料能够协同增效，发挥各自优势的同时，且尽可能地减小材料自身的劣势对整个体系的影响，优势互补，从而实现性能的平衡和最大化。
在一些实施例中，无定形碳在第一充电阶段内的嵌锂容量为C 1，负极活性材料在整个充电过程中的嵌锂容量为C sum，C 1/C sum的取值范围为5％～50％；
其中，第一充电阶段是指无定形碳的嵌锂电位大于石墨的嵌锂电位，且无定形碳的嵌锂电位大于非碳负极材料的嵌锂电位时的充电阶段。
在一些实施例中，优选地，C 1/C sum的取值范围为10％～35％。C 1/C sum的取值控制在优选范围内，能使得电池的快充性能更好、寿命更长、且满充反弹更小。
在一些实施例中，C 1/C sum的取值例如还可以是8％、12％、16％、20％、24％、28％、32％、36％、40％、44％或48％。
无定形碳材料在充电过程中的电压变化比较大，有前期嵌锂电位均大于非碳负极材料和石墨材料的区间，也有后期较长一段低于非碳负极材料和石墨材料接近0V的嵌锂区间，在充电过程中，嵌锂电位较大的材料会优先嵌锂，因此，控制无定形碳在第一充电阶段内的嵌锂容量在整个充电过程中负极嵌锂容量中的占比为一定范围，可以尽可能地减少前期大倍率充电时负极材料的膨胀，但同时又不会因为无定形碳材料较低的能量密度和首效对体系造成明显的负面影响。
在一些实施例中，硬碳包括树脂碳以及炭黑中的一种或多种。硬碳是高分子聚合物的热解碳，其在≥2500℃的温度下也难以石墨化。硬碳结构稳定且充放电循环寿命长、安全性能好，采用硬碳作为无定形碳来源，更有利于负极的循环性能以及寿命的提升。
在一些实施例中，软碳包括中间相炭微球、焦炭以及碳纤维中的一种或多种。软碳是指在2500℃以上的高温下能石墨化的无定型碳，其具有较低且平稳的充放电电位平台，采用软碳作为无定形碳来源，更有利于负极充放电容量和效率的提升。
在一些实施例中，硅基负极材料包括单质硅、硅氧化合物、硅氮复合物以及硅合金中的一种或多种。
在一些实施例中，石墨的Dv50粒径范围为5μm～25μm。Dv50是指体积分布中50％的颗粒所对应的粒径。石墨的Dv50粒径例如还可以是10μm、15μm或20μm。
在一些实施例中，石墨的石墨化度为88％～99％。石墨化度是指碳原子形成密排六方石墨晶体结构的程度，其晶格尺寸越接近理想石墨的点阵参数，石墨化度就越高，通过控制石墨材料需具有一定的石墨化度，可赋予负极材料更高的性能，使本申请的负极活性材料制得的电池具有更大的容量。石墨的石墨化度例如还可以是90％、92％、94％、96％或98％。
在一些实施例中，无定形碳的Dv50粒径范围为2μm～10μm。无定形碳的Dv50粒径例如还可以是4μm、6μm或8μm。
在一些实施例中，非碳负极材料的Dv50粒径范围为0.05μm～20μm。无定形碳的Dv50粒径例如还可以是2μm、4μm、6μm、8μm、10μm、12μm、14μm、16μm或18μm。
控制几种原料的粒径在合适范围内，能使得本申请的负极活性材料制成浆料时分散更好，不易团聚，且制得的负极极片结构更均匀、具有更合适的孔隙率，从而品质更优。
本申请中的石墨、无定形碳以及非碳负极材料均可以为一次颗粒，也可以为二次颗粒，还可以是一次颗粒或二次颗粒的混合物。
在一些实施例中，负极活性材料在负极活性材料层中的质量百分比为92％～99％。负极活性材料在负极活性材料层中的质量百分占比是特别根据本申请的负极活性材料配方设计的，质量百分比控制在合适范围内，能使得负极活性材料最大限度发挥优势，从而使负极极片具有更佳的性能，同时，生产成本更低。
在一些实施例中，负极活性材料在负极活性材料层中的质量百分比例如还可以是93％、94％、95％、96％、97％或98％。
在一些实施例中，负极活性材料层的厚度为30μm～100μm。该厚度是指在集流体的一个表面形成的单层负极活性材料层的厚度，也是基于本申请的负极活性材料配方设定的，合适的厚度范围能使得活性材料层的特征厚度占比更高，发挥更好的性能。
在一些实施例中，负极活性材料层的厚度例如还可以是52μm～88μm，又如还可以是35μm、40μm、45μm、50μm、55μm、60μm、65μm、70μm、75μm、80μm、85μm、90μm或95μm。
在一些实施例中，负极极片的压实密度为1g/cm 3～1.7g/cm 3。根据本申请的负极活性材料的配方，合适的压实密度能够很好地平衡极片的能量密度、充电性能与安全性。
在一些实施例中，负极极片的压实密度例如可以是1.28g/cm 3～1.48g/cm 3，又如还可以是1.05g/cm 3、1.1g/cm 3、1.15g/cm 3、1.2g/cm 3、1.25g/cm 3、1.3g/cm 3、1.35g/cm 3、1.4g/cm 3、1.45g/cm 3、1.5g/cm 3、1.55g/cm 3、1.6g/cm 3或1.65g/cm 3。
在一些实施例中，负极极片的孔隙率为20％～70％。
在一些实施例中，优选地，负极极片的孔隙率为25％～60％。
在一些实施例中，负极极片的孔隙率例如可以是22％、24％、26％、28％、30％、32％、34％、36％、38％、40％、42％、44％、46％、48％、50％、52％、54％、56％或58％。负极极片的孔隙率控制在合适范围内，保障了充电能力的同时，不会过大地降低体系的能量密度。
在一些实施例中，负极极片的满充反弹为20％～60％。负极极片的满充反弹例如可以是22％～48％，又如还可以是25％、30％、35％、40％、45％、50％或55％。本申请的负极极片在具备高能量密度的同时，满充反弹远远低于硅/锡基等高能量密度的负极材料(≥100％)，有效避免了由于快速充电过程中材料颗粒外层的膨胀应力与颗粒内部的膨胀应力不匹配导致的颗粒破碎，进而避免了进一步的SEI膜修复和活性锂的损失，因此，在快充过程中，较传统的高能量密度体系具备更低的循环衰减和更长的寿命。
在一些实施例中，负极极片的放电末端阳极电位≥0.6V，放电曲线≥2个电压平台。进一步地，负极极片的放点末端阳极电位≥1.0V。本申请制得的负极极片具有较高的放点末端阳极电位，这使得阳极在放电时电量能够得以充分发挥；大于两个电压平台的放电曲线使得大倍率充电时无定形碳材料能按照预设的嵌锂顺序有序嵌锂，从而发挥本申请复合负极活性材料的优势，兼顾高能量密度、优秀的循环性能以及较长的使用寿命。
在一些实施例中，正极极片中包括正极活性物质和补锂剂；正极活性物质可以包括镍钴锰酸锂、锰酸锂、磷酸铁锂、富锂锰酸锂以及钴酸锂中的一种或多种，补锂剂可以包括Li 7/3Ti 5/3O 4、Li 2.3Mo 6S 7.7、Li 2NiO2、Li 2CuO 2、Li 6CoO 4、Li 5FeO 4、Li 6MnO 4、Li 2MoO 3、Li 3N、Li 2O、LiOH以及Li 2CO 3中的一种或多种。本申请的负极极片可以搭配多种常见的正极活性材料使用，适用范围广，能满足市场多种不同需求。合适种类的补锂剂的引入可以进一步使得本申请的负极活性材料制得的电池具备更高的首效。
在一些实施例中，单位面积负极材料的负载量与单位面积正极材料的负载量的比值N/P的取值范围为0.99～1.2。N/P比能使得本申请制得的负极极片更好地发挥其优势，与正极极片搭配，制得性能更优异的二次电池。
在一些实施例中，二次电池还包括电解质。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施例中，上述负极极片的制备方法包括以下步骤：
将负极活性材料、溶剂以及任选的助剂混合，制得负极浆料；将负极浆料涂布在 负极集流体的至少一个表面，干燥、压制；
其中，助剂包括粘结剂、分散剂以及导电剂中的一种或多种。本申请负极活性材料无需特殊处理，与助剂、溶剂等原料简单混合即可制得负极浆料，再采用常规工艺进行涂布、干燥和压制即可制得负极极片。制备方法简单，易于大规模工业化生产。
进一步地，粘结剂选自聚苯乙烯丁二烯、聚偏氟乙烯、聚丙烯酸、聚丙烯腈、聚乙烯醇(PVA)、羧甲基壳聚糖以及海藻酸钠中的一种或多种。
进一步地，粘结剂在负极浆料中的质量百分含量为0.5％～5％。
进一步地，分散剂选自羧甲基纤维素、羧甲基纤维素钠以及PTC热敏电阻材料中的一种或多种。
进一步地，分散剂在负极浆料中的质量百分含量为0％～3％。
进一步地，导电剂选自石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维以及多孔碳材料中的一种或多种。
进一步地，导电剂在负极浆料中的质量百分含量为0％～4％。
第二方面，本申请提供了一种电池模块，其包括上述实施例中的二次电池。
第三方面，本申请提供了一种电池包，其包括上述实施例中的电池模块。
第四方面，本申请提供了一种用电装置，其包括上述实施例中的二次电池、电池模块以及电池包中的一种或多种。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，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。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为 金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(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-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料采用本申请任一实施例中包括的负极活性材料。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟 砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，电极组件中包括位于正极极片和负极极片之间的隔离膜。
在一些实施方式中，二次电池中还包括隔离膜，隔离膜位于正极极片和负极极片之间。
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，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。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，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一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，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。
在一些实施方式中，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，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。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、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用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电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。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
(1)在100L的搅拌罐中，分别加入人造石墨、硬碳、预锂化的SiOx(0＜x＜2)、导电剂(导电炭黑sp和碳纳米管)、粘结剂丁苯橡胶和增稠剂羧甲基纤维素钠；对应加入质量比例如下，人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠为43.245：38.44：14.415：0.2：0.5：2：1.2；加入一定量溶剂水混合均匀，保证浆料的固含为50％，得到负极浆料；利用挤压式涂布机进行涂布，将前述制得的负极浆料涂布在负极集流体的两个表面，涂布面密度为9.7mg/cm 2，涂布完成后，极片经过烘箱烘干后，再在冷压辊中进行压实，得到负极极片，上述负极浆料干燥压实后形成的单面的负极活性材料层的厚度为75μm，负极极片的压实密度为1.3g/cm 3，负极极片的孔隙率为45％；
上述人造石墨的粒径Dv50为14μm，石墨化度为95％；硬碳的粒径Dv50为5μm，预锂化的SiOx的Dv50为8μm。
(2)将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、导电剂Super P、粘结剂聚偏氟乙烯(PVDF)按质量比97:1.5:1.5在适量的溶剂N-甲基吡咯烷酮(NMP)中充分搅拌混合，形成均匀的正极浆料；将正极浆料涂覆于正极集流体铝箔的表面，经干燥、冷压后，得到正极极片。其中，正极膜片的面密度为24mg/cm 2，压实密度为3.4g/cm 3。
(3)电解液的制备
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比4:3:3混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。
(4)二次电池的制备
将步骤(2)制得的正极极片、PE隔离膜、步骤(1)制得的负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件加入外包装，加入步骤(3)制得的电解液，经封装、静置、化成、老化等常规工序后得到二次电池。
实施例2
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为9.61：72.075：14.415：0.2：0.5：2：1.2；
该实施例中，负极浆料干燥压实后形成的负极活性材料层的厚度为88μm，负极极片的压实密度为1.1g/cm 3，负极极片的孔隙率为42％。
实施例3
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为72.075：9.61：14.415：0.2：0.5：2：1.2；
该实施例中，负极浆料干燥压实后形成的负极活性材料层的厚度为65μm，负极极片的压实密度为1.5g/cm 3，负极极片的孔隙率为32％。
实施例4
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为78.802：9.61：7.688：0.2：0.5：2：1.2；
该实施例中，负极浆料干燥压实后形成的负极活性材料层的厚度为63μm，负极极片的压实密度为1.55g/cm 3，负极极片的孔隙率为30％。
实施例5
与实施例1基本一致，区别在于，负极活性材料中的无定形碳为软碳。
实施例6
与实施例1基本一致，区别在于，该实施例中的正极极片添加了Li 2NiO 2补锂剂，且N/P比为1.05。
实施例7
制备工艺与实施例1一致，负极活性材料的组成为：
天然石墨：多孔碳材料：锡基负极：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为72.075：19.22：4.805：0.2：0.5：2：1.2；
该实施例中，负极浆料干燥压实后形成的负极活性材料层的厚度为57μm，负极 极片的压实密度为1.7g/cm 3，负极极片的孔隙率为28％；
上述天然石墨的粒径Dv50为20μm，石墨化度为95％；多孔碳的粒径Dv50为6μm，锡基负极材料的Dv50为10μm；
正极材料选用富锂锰基锰酸锂。
对比例1
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为89.5：4.6：2：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为63μm，负极极片的压实密度为1.55g/cm 3，负极极片的孔隙率为20％。
对比例2
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为14.415：43.245：38.44：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为63μm，负极极片的压实密度为1.55g/cm 3，负极极片的孔隙率为70％。
对比例3
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为72.075：4.805：19.22：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为63μm，负极极片的压实密度为1.55g/cm 3，负极极片的孔隙率为23％。
对比例4
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为9.61：81.685：4.805：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为97μm，负极极片的压实密度为1g/cm 3，负极极片的孔隙率为34％。
对比例5
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为81.685：4.805：9.61：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为63μm，负极极片的压实密度为1.55g/cm 3，负极极片的孔隙率为22％。
对比例6
与实施例1基本一致，区别在于，负极活性材料的组成为：
人造石墨：硬碳：预锂化的SiOx：导电剂sp：碳纳米管：粘结剂丁苯橡胶：增稠剂羧甲基纤维素钠的质量比为4.805：86.49：4.805：0.2：0.5：2：1.2；
该对比例中，负极浆料干燥压实后形成的负极活性材料层的厚度为97μm，负极极片的压实密度为1g/cm 3，负极极片的孔隙率为32％。
对比例7
与实施例6基本一致，区别在于，调整补锂剂用量，使N/P比为0.98。
对比例8
与实施例6基本一致，区别在于，调整补锂剂用量，使N/P比为1.25。
表征测试：
将上述各实施例及对比例中制得的锂离子电池进行以下表征测试
(1)膜片厚度：在本申请中，负极膜片的厚度为本领域公知的含义，可采用本领域已知的方法测试，例如万分尺(如Mitutoyo293-100型，精度为0.1μm)。
(2)双层涂布膜片厚度：在本申请中，第一负极膜层和第二负极膜层各自的厚度可以通过使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。样品制备如下：首先将负极极片裁成一定尺寸的待测样品(例如2cm×2cm)，通过石蜡将负极极片固定在样品台上。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如 IB-19500CP)电源和抽真空(例如10 -4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光。样品测试可参考JY/T010-1996。为了确保测试结果的准确性，可以在待测样品中随机选取多个(例如10个)不同区域进行扫描测试，并在一定放大倍率(例如500倍)下，读取标尺测试区域中第一负极膜层和第二负极膜层各自的厚度，取多个测试区域的测试结果的平均值分别作为第一负极膜层和第二负极膜层的厚度。
(3)硅基材料的质量占比：在本申请中，硅基材料在负极膜层中的质量占比为本领域公知的含义，可采用本领域已知的方法测试。例如利用扫描电子显微镜(例如ZEISS Sigma 300)观察负极膜片的截面(例如膜片厚度方向的截面)，使用能量分散型X射线分析(例如ZEISS Sigma 300自带能谱仪)进行定量映射。由此，对截面的扫描位置测定负极膜片的元素含量，求出元素分布。在截面内的一个区域中，可通过对Si元素分布进行积分，从而求出区域中的Si含量。为了提高测试的准确性，可以统计多个区域(例如10个)的测试结果，取平均值。
(4)粒径：在本申请中，硅基材料的粒径为本领域公知的含义，可采用本领域已知的方法测试，例如可以使用扫描电子显微镜(例如ZEISS Sigma 300)进行测试。样品制备如下：首先将负极极片裁成一定尺寸的待测样品(例如2cm×2cm)，通过石蜡将负极极片固定在样品台上。然后将样品台装进样品架上锁好固定，打开氩离子截面抛光仪(例如IB-19500CP)电源和抽真空(例如10 -4Pa)，设置氩气流量(例如0.15MPa)和电压(例如8KV)以及抛光时间(例如2小时)，调整样品台为摇摆模式开始抛光。样品测试可参考JY/T010-1996。为了确保测试结果的准确性，可以在待测样品中随机选取多个(例如10个)不同区域进行扫描测试，并在一定放大倍率(例如500倍)下，读取标尺测试区域中所有硅基材料的粒径。为了进一步提高测试的准确性，可以统计多个区域的测试结果。
在本申请中，负极活性材料的Dv50为本领域公知的含义，可采用本领域已知的仪器和方法进行测定。例如参照标准GB/T 19077.1-2016，使用激光粒度分析仪(如Malvern Master Size 3000)测定。其中，D v50为所述负极活性材料累计体积分布百分数达到50％时所对应的粒径。
(5)负极膜片面密度：在本申请中，负极膜片的面密度为本领域公知的含义，可采用本领域已知的方法测试。例如取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜片)，冲切成面积为S1的小圆片，称其重 量，记录为M1。然后将上述称重后的负极极片的负极膜片擦拭掉，称量负极集流体的重量，记录为M0，负极膜片的面密度＝(负极极片的重量M1－负极集流体的重量M0)/S1。为了确保测试结果的准确性，可以测试10组待测样品，并计算平均值。
在本申请中，负极膜片的压实密度为本领域公知的含义，可采用本领域已知的方法测试。负极膜片的压实密度＝负极膜片的面密度/负极膜片的厚度。
(6)电池的快速充电能力测试
25℃下，将上述各实施例和对比例的电池以1C(即1h内完全放掉理论容量的电流值)的电流进行第一次充电和放电，具体包括：将电池以1C倍率恒流充电至电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至电压2.5V，记录其实际容量为C0。
然后将电池依次以1.0C0、1.3C0、1.5C0、1.8C0、2.0C0、2.3C0、2.5C0、3.0C0、恒流充电至全电池充电截止电压4.25V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C0放电至全电池放电截止电压2.8V，记录不同充电倍率下充电至10％、20％、30％、……、80％SOC(State of Charge，荷电状态)时所对应的负极电位，绘制出不同SOC态下的充电倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C10％SOC、C20％SOC、C30％SOC、C40％SOC、C50％SOC、C60％SOC、C70％SOC、C80％SOC，根据公式(60/C20％SOC+60/C30％SOC+60/C40％SOC+60/C50％SOC+60/C60％SOC+60/C70％SOC+60/C80％SOC)×10％计算得到该电池从10％SOC充电至80％SOC的充电时间T，单位为min。该时间越短，则电池的快速充电性能越优秀。
(7)电池的循环性能测试
25℃下，将各实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以1C倍率恒流放电至放电截止电压2.5V，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池在25℃下的循环寿命。
(8)C 1/C sum：将阳极极片和锂片，装成扣式半电池，采用0.04C的倍率进行充放电，充电截至电压为1.2V，放电截至电压为0V，根据充放电曲线，得到总的放电克容量，以及C 1，计算后得到C 1/C sum；
(9)N/P：将阴极极片和阳极极片分别跟锂片制备成扣式半电池，采用0.04C的 倍率进行充放电测试，分别得到阴极极片的首次充电克容量和阳极极片的首次充电克容量，其中阴极极片扣式半电池的充电截止电压为4.3V，放电截止电压为2.5V；阳极极片扣式半电池的充电截至电压为1.2V，放电截至电压为0V，
(10)能量密度：测试电芯的体积，方壳电芯可以通过长宽高的尺寸计算，圆柱电芯可以通过高和直径进行计算，软包电芯可以通过排水法得到电芯的体积；然后通过充放电设备，在25℃下，0.33C进行充放电，记录放电能量，放电能量除以电芯的体积，就得到电芯的体积能量密度；
表1
Figure PCTCN2022089563-appb-000001
从表1可知，本申请各实施例中制得的负极活性材料制成电池后，具备良好的快充性能和循环性能，且能量密度高、满充反弹小，特别是各项参数均位于优选范围内的实施例1，具备最优的综合性能。
相较于实施例1，对比例1中y值过小，导致C 1/C sum过小，循环性能、能量密度和快充性能都明显下降；对比例2中y值过大，循环性能严重下降，且满充反弹大幅度上升；对比例3中，z值过小，低于0.062x+0.263y的下限，导致C 1/C sum过小，快 充性能下降，能量密度和循环圈数也有所下降，且满充反弹上升；对比例4中，z值过大，高于1.18x+5y的上限，虽然满充反弹降低，但快充性能、能量密度和循环圈数均下降；对比例5中，C 1/C sum过小，能量密度稍有下降，快充性能和循环圈数下降明显；对比例6中，C 1/C sum过大，能量密度和循环性能明显下降；对比例7中，N/P比偏小，虽然能量密度有所提升，但快充性能下降，循环性能尤其下降明显；对比例8中，N/P比偏大，虽然快充性能和满充反弹变化不大，但能量密度和循环性能均有所下降。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准，说明书及附图可用于解释权利要求的范围。

Claims (26)

  1. 一种二次电池，包括：
    正极极片；
    负极极片；
    隔离膜，设置于所述正极极片和所述负极极片之间；
    所述负极极片包括负极集流体以及设置于所述负极集流体至少一个表面的负极活性材料层，所述负极活性材料层中的负极活性材料包括石墨、无定形碳和非碳负极材料；其中，所述无定形碳包括硬碳、软碳以及多孔碳中的一种或多种，所述非碳负极材料为硅基负极材料和/或锡基负极材料。
  2. 根据权利要求1所述的二次电池，其特征在于，所述负极活性材料中，所述石墨的质量百分含量为x，所述无定形碳的质量百分含量为y，所述非碳负极材料的质量百分含量为z；x、y、z满足如下关系：0.062x+0.263y≤z≤1.18x+5y。
  3. 根据权利要求2所述的二次电池，其特征在于，所述x、y、z满足如下关系：0.08x+0.4y≤z≤1x+4y。
  4. 根据权利要求2～3任一项所述的二次电池，其特征在于，所述x、y、z满足以下关系：x+y+z＝1。
  5. 根据权利要求2～4任一项所述的二次电池，其特征在于，所述y的取值范围为5％～50％。
  6. 根据权利要求1～5任一项所述的二次电池，其特征在于，所述无定形碳在第一充电阶段内的嵌锂容量为C 1，所述负极活性材料在整个充电过程中的嵌锂容量为C sum，C 1/C sum的取值范围为5％～50％；
    其中，所述第一充电阶段是指所述无定形碳的嵌锂电位大于所述石墨的嵌锂电位，且所述无定形碳的嵌锂电位大于所述非碳负极材料的嵌锂电位时的充电阶段。
  7. 根据权利要求6所述的二次电池，其特征在于，所述C 1/C sum的取值范围为10％～35％。
  8. 根据权利要求1～7任一项所述的二次电池，其特征在于，所述硬碳包括树脂碳以及炭黑中的一种或多种。
  9. 根据权利要求1～8任一项所述的二次电池，其特征在于，所述软碳包括中间相炭微球、焦炭以及碳纤维中的一种或多种。
  10. 根据权利要求1～9任一项所述的二次电池，其特征在于，所述硅基负极材料包 括单质硅、硅氧化合物、硅氮复合物以及硅合金中的一种或多种。
  11. 根据权利要求1～10任一项所述的二次电池，其特征在于，所述石墨的Dv50粒径范围为5μm～25μm。
  12. 根据权利要求1～11任一项所述的二次电池，其特征在于，所述石墨的石墨化度为88％～99％。
  13. 根据权利要求1～12任一项所述的二次电池，其特征在于，所述无定形碳的Dv50粒径范围为2μm～10μm。
  14. 根据权利要求1～13任一项所述的二次电池，其特征在于，所述非碳负极材料的Dv50粒径范围为0.05μm～20μm。
  15. 根据权利要求1～14所述的二次电池，其特征在于，所述负极活性材料在所述负极活性材料层中的质量百分比为92％～99％。
  16. 根据权利要求1～15任一项所述的二次电池，其特征在于，所述负极活性材料层的厚度为30μm～100μm。
  17. 根据权利要求1～16任一项所述的二次电池，其特征在于，所述负极极片的压实密度为1g/cm 3～1.7g/cm 3。
  18. 根据权利要求1～17任一项所述的二次电池，其特征在于，所述负极极片的孔隙率为20％～60％。
  19. 根据权利要求1～18任一项所述的二次电池，其特征在于，所述负极极片的孔隙率为30％～55％。
  20. 根据权利要求1～19任一项所述的二次电池，其特征在于，所述负极极片的满充反弹为20％～50％。
  21. 根据权利要求1～20任一项所述的二次电池，其特征在于，所述负极极片的放电末端阳极电位≥0.6V，放电曲线≥2个电压平台。
  22. 根据权利要求1～21任一项所述的二次电池，其特征在于，所述正极极片中包括正极活性物质和补锂剂；所述正极活性物质包括镍钴锰酸锂、锰酸锂、磷酸铁锂、富锂锰酸锂以及钴酸锂中的一种或多种，所述补锂剂包括Li 7/3Ti 5/3O 4、Li 2.3Mo 6S 7.7、Li 2NiO2、Li 2CuO 2、Li 6CoO 4、Li 5FeO 4、Li 6MnO 4、Li 2MoO 3、Li 3N、Li 2O、LiOH以及Li 2CO 3中的一种或多种。
  23. 根据权利要求1～22任一项所述的二次电池，其特征在于，所述二次电池中，单位面积负极材料的负载量与单位面积正极材料的负载量的比值N/P的取值范围为 0.99～1.2。
  24. 一种电池模块，其特征在于，包括权利要求1～23任一项所述的二次电池。
  25. 一种电池包，其特征在于，包括权利要求24所述的电池模块。
  26. 一种用电装置，其特征在于，包括权利要求1～23任一项所述的二次电池、权利要求24所述的电池模块以及权利要求25所述的电池包中的一种或多种。
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KR20190101651A (ko) * 2018-02-23 2019-09-02 주식회사 엘지화학 음극 슬러리, 이를 포함하는 리튬 이차전지용 음극 및 리튬 이차전지
CN113964305A (zh) * 2021-10-22 2022-01-21 湖北亿纬动力有限公司 一种硅碳复合负极材料、其制备方法和锂离子电池

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