WO2024239443A1 - 一种复合电芯及应用其的电池 - Google Patents

一种复合电芯及应用其的电池 Download PDF

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Publication number
WO2024239443A1
WO2024239443A1 PCT/CN2023/109021 CN2023109021W WO2024239443A1 WO 2024239443 A1 WO2024239443 A1 WO 2024239443A1 CN 2023109021 W CN2023109021 W CN 2023109021W WO 2024239443 A1 WO2024239443 A1 WO 2024239443A1
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Prior art keywords
negative electrode
electrode active
active material
active coating
blended
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PCT/CN2023/109021
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English (en)
French (fr)
Inventor
李嘉玲
王超
胡骐
曾汉民
何巍
刘金成
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Eve Power Co Ltd
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Eve Power Co Ltd
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Priority claimed from CN202310606798.3A external-priority patent/CN116598598A/zh
Priority claimed from CN202321265535.2U external-priority patent/CN219998286U/zh
Application filed by Eve Power Co Ltd filed Critical Eve Power Co Ltd
Publication of WO2024239443A1 publication Critical patent/WO2024239443A1/zh
Anticipated expiration legal-status Critical
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the field of battery technology, and specifically relates to a composite battery cell and a battery using the same.
  • Non-carbon negative electrode materials are mainly silicon-based materials. Among them, artificial graphite has excellent cycle, rate, and high temperature performance, and its various properties are relatively balanced.
  • the silicon-based series mainly includes silicon-carbon and silicon-oxygen materials. Its theoretical specific capacity is extremely high. The lithium insertion potential of silicon is higher than that of carbon materials. The risk of lithium precipitation is small and its safety is high. However, the volume of silicon-based lithium-insertion and deintercalation changes greatly during the process. The particles are easily broken and pulverized, which leads to easy failure, low initial efficiency and poor cycle.
  • the industry generally directly coats the slurry formed by mixing different types of the above-mentioned negative electrode active materials on the surface of the current collector to prepare the negative electrode sheet.
  • the different types of negative electrode active materials often cannot give full play to their material advantages due to uneven material mixing and unreasonable material matching. It can even make the battery cells that integrate different types of negative electrode active materials worse than the battery cells that only use a single active material in some performance.
  • the present application provides a composite battery cell and a battery using the same, which fully utilizes the synergistic advantages of different types of negative electrode active materials and further improves the energy density, rate performance, and cycle performance of the battery.
  • a composite battery cell comprising at least two negative electrode sheets, wherein the negative electrode active materials contained in the composite battery cell comprise at least two of artificial graphite, natural graphite, hard carbon, soft carbon, and silicon-based materials, and the negative electrode active materials are used to construct the negative electrode active coating of the negative electrode sheet;
  • the composite battery cell comprises at least one of a first negative electrode sheet and a second negative electrode sheet, wherein the first negative electrode sheet comprises only one negative electrode active material, and the second negative electrode sheet comprises at least two different types of negative electrode active materials; wherein the second negative electrode sheet comprises at least one of a composite negative electrode sheet and a blended negative electrode sheet;
  • the composite negative electrode sheet is provided with at least two layers of single-phase negative electrode active coatings on one side of the negative electrode current collector, and the single-phase negative electrode active coatings contain only one negative electrode active material; at least one layer of the negative electrode active coatings provided on the blended negative electrode sheet is a blended negative electrode active coating, and the blended negative electrode active coating comprises at
  • Qn represents the area of any layer of negative electrode active coating included in the negative electrode sheet
  • Sn represents the surface density of any layer of negative electrode active coating included in the negative electrode sheet
  • Cm represents the gram capacity of any negative electrode active material
  • Wm represents the mass percentage of the negative electrode active material in the layer of negative electrode active coating
  • i represents the number of types of negative electrode active materials included in each layer of negative electrode active coating, i is an integer greater than or equal to 1
  • k represents the number of layers of negative electrode active coating included in each negative electrode sheet, k is an integer greater than or equal to 1
  • the composite battery cell provided in the present application integrates at least two negative electrode active materials, and can select the types of negative electrode active materials used and adjust the amount of different types of negative electrode active materials to enable the composite battery cell
  • the composite battery cell can give full play to the synergistic advantages of different types of negative electrode active materials, so that the energy density, rate performance, and cycle performance of the above-mentioned composite battery cell are better than those of the battery cell using a single negative electrode active material. In other words, the overall improvement has been achieved.
  • the first negative electrode sheet and the second negative electrode sheet are used as examples to illustrate different calculation methods of Formula I.
  • Formula I For example, an optional implementation of the first negative electrode sheet (setting of the negative electrode active coating: single-layer coating on one side of the current collector and symmetrical setting on both sides): the first negative electrode sheet only uses one negative electrode active material, and uses the negative electrode active material to set a layer of negative electrode active coating on both sides of the negative electrode current collector, respectively.
  • the two layers of negative electrode active coatings located on both sides of the negative electrode current collector are symmetrically arranged with each other, and the mass content of the negative electrode active material used in one layer of the negative electrode active coating is W1, the gram capacity of the negative electrode active material is C1, the surface density of the negative electrode active coating layer is S1, and the area of the negative electrode active coating layer is Q1. Then, the capacity of the negative electrode active coating layer is Q1 ⁇ S1 ⁇ W1 ⁇ C1. Correspondingly, the capacity of the other layer of the negative electrode active coating is also calculated in the above manner. Since the two layers of negative electrode active coatings are symmetrically arranged, the total capacity of the first negative electrode sheet is 2 ⁇ Q1 ⁇ S1 ⁇ W1 ⁇ C1.
  • a first optional implementation of a composite negative electrode sheet (setting of the negative electrode active coating: layered coating on one side of the current collector and symmetrical setting on both sides): the composite negative electrode sheet uses two negative electrode active materials, marked as a first negative electrode active material and a second negative electrode active material, and a first negative electrode active coating containing only a single negative electrode active material of the first negative electrode active material and a second negative electrode active coating containing only a single negative electrode active material of the second negative electrode active material are sequentially arranged on one side of the negative electrode current collector, and then negative electrode active coatings symmetrical to the first negative electrode active coating and the second negative electrode active coating are correspondingly arranged on the other side of the negative electrode current collector; on either side of the negative electrode current collector, the mass content of the first negative electrode active material in the first negative electrode active coating is W1, the gram capacity of the first negative electrode active material is C1, the surface density of the first negative electrode active coating is S1, and the area of the first negative electrode active coating is Q1.
  • the capacity of the first negative electrode active coating is Q1 ⁇ S1 ⁇ W1 ⁇ C1
  • the mass content of its second negative electrode active material in the second negative electrode active coating is W2
  • the gram capacity of the second negative electrode active material is C2
  • the surface density of the second negative electrode active coating is S2
  • the area of the second negative electrode active coating is Q2
  • the capacity of the second negative electrode active coating is Q2 ⁇ S2 ⁇ W2 ⁇ C2
  • the capacity of the negative electrode active coating on this side is (Q1 ⁇ S1 ⁇ W1 ⁇ C1+Q2 ⁇ S2 ⁇ W2 ⁇ C2).
  • the capacity of the negative electrode active coating on the other side of the negative electrode current collector is also calculated in the above manner.
  • the total capacity of the first negative electrode sheet is 2 ⁇ (Q1 ⁇ S1 ⁇ W1 ⁇ C1+Q2 ⁇ S2 ⁇ W2 ⁇ C2).
  • a second optional implementation of the composite negative electrode sheet (setting of the negative electrode active coating: layered coating or single-layer coating on one side of the current collector, asymmetrical setting on both sides): the composite negative electrode sheet uses three negative electrode active materials, marked as a first negative electrode active material, a second negative electrode active material and a third negative electrode active material, and a first negative electrode active coating containing only a single negative electrode active material of the first negative electrode active material and a second negative electrode active coating containing only a single negative electrode active material of the second negative electrode active material are sequentially arranged on one side of the negative electrode current collector, and then a third negative electrode active coating containing only a single negative electrode active material of the third negative electrode active material is arranged on the other side of the negative electrode current collector; On one side of the negative electrode current collector where a double-layer negative electrode active coating is provided, the mass content of the first negative electrode active material in the first negative electrode active coating is W1, the gram capacity of the first negative electrode active material is C1, the surface density of the first negative electrode
  • a first optional implementation of the blended negative electrode sheet (setting of the negative electrode active coating: a single layer coating on one side of the current collector and symmetrical setting on both sides): the blended negative electrode sheet uses two negative electrode active materials, marked as a first negative electrode active material and a second negative electrode active material, and a layer of negative electrode active coating is set on each side of the negative electrode current collector using a slurry blended from the first negative electrode active material and the second negative electrode active material.
  • the two layers of negative electrode active coatings located on the two layers of the negative electrode current collector are symmetrically set to each other, and in one layer of the negative electrode active coating, the mass content of the first negative electrode active material is W1, with The gram capacity of the first negative electrode active material is C1, and the mass content of the second negative electrode active material is W2.
  • the gram capacity of the second negative electrode active material is C2, the surface density of the negative electrode active coating layer is S1, and the area of the negative electrode active coating layer is Q1.
  • the capacity of the negative electrode active coating layer is Q1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2).
  • the capacity of the other negative electrode active coating layer is also calculated in the above manner.
  • the total capacity of the second negative electrode sheet is 2 ⁇ (Q1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2)).
  • the blended negative electrode sheet uses three negative electrode active materials, marked as a first negative electrode active material, a second negative electrode active material and a third negative electrode active material, and a slurry formed by blending the first negative electrode active material and the second negative electrode active material is used to set the first negative electrode active coating on one side of the negative electrode active coating, and then a second negative electrode active coating containing only a single negative electrode active material of the third negative electrode active material is set on the other side of the negative electrode current collector;
  • the mass content of the first negative electrode active material is W1
  • the gram capacity of the first negative electrode active material is C1
  • the composite battery cell includes two first negative electrode sheets, the first negative electrode sheets include a first negative electrode sheet A and a first negative electrode sheet B, the negative electrode active material contained in the first negative electrode sheet A is only the first negative electrode active material A, the negative electrode active material contained in the first negative electrode sheet B is only the first negative electrode active material B, and the types of the first negative electrode active material A and the first negative electrode active material B are different from each other.
  • the first negative electrode active material A is artificial graphite
  • the first negative electrode active material B is natural graphite.
  • a negative electrode sheet containing only artificial graphite and a negative electrode sheet containing only natural graphite are connected in parallel, so that the advantages of artificial graphite and natural graphite are integrated in the battery cell at the same time.
  • Artificial graphite has excellent cycle performance and rate performance, which reduces the problem of low first efficiency caused by many surface defects of natural graphite and the problem of low cycle life caused by large expansion, thereby improving the rate performance and cycle performance of the negative electrode active coating containing natural graphite.
  • natural graphite can give play to its high capacity, high compaction and low cost characteristics, and then in the process of realizing the simultaneous charging and discharging of the battery cell containing the two above-mentioned two negative electrode active materials, give full play to the advantages of the two materials and form complementary advantages.
  • the above-mentioned negative electrode sheets only use one negative electrode active material, which is conducive to the batch production of the electrode sheets and is suitable for industrial production.
  • A1 represents the number of first negative electrode sheets A
  • A2 represents the number of first negative electrode sheets B
  • A1/A2 0.005-200.
  • the negative electrode active coating provided on the first negative electrode sheet A is the first negative electrode active coating A
  • the negative electrode active coating provided on the first negative electrode sheet B is the first negative electrode active coating B
  • the first negative electrode active coating A is symmetrically provided on both sides of the negative electrode collector of the first negative electrode sheet A
  • the first negative electrode active coating B is symmetrically provided on both sides of the negative electrode collector of the first negative electrode sheet B.
  • the composite battery cell includes a first negative electrode sheet and a composite negative electrode sheet, the negative electrode active material contained in the first negative electrode sheet is only a first negative electrode active material, and the single-phase negative electrode active coating provided on the composite negative electrode sheet includes a single-phase negative electrode active coating A and a single-phase negative electrode active coating B, wherein the negative electrode active material contained in the single-phase negative electrode active coating A is only a single-phase negative electrode active material A, and the negative electrode active material contained in the single-phase negative electrode active coating B is only a single-phase negative electrode active material B, and the single-phase negative electrode active material B is different from at least one of the first negative electrode active material and the single-phase negative electrode active material A.
  • the first negative electrode active material is artificial graphite
  • the single-phase negative electrode active material A is artificial graphite
  • the single-phase negative electrode active material B is hard carbon.
  • artificial graphite-hard carbon negative electrode sheets and artificial graphite negative electrode sheets are used together. Since hard carbon has the advantages of large interlayer spacing and stable structure, the negative electrode active coating containing hard carbon is The rate performance and cycle stability reach a high level. At the same time, artificial graphite has the advantages of high capacity and good compatibility with the electrolyte.
  • the advantages of the two substances are fully utilized to exert a synergistic effect, so that the composite battery cell has the advantages of high energy density, high rate and long cycle.
  • A1 represents the number of first negative electrode sheets
  • A3 represents the number of composite negative electrode sheets
  • A1/A3 0.005-200.
  • the single-phase negative electrode active coating A and the single-phase negative electrode active coating B are sequentially arranged in a direction away from the current collector surface.
  • the negative electrode active coating provided on the first negative electrode sheet is the first negative electrode active coating; the single-phase negative electrode active coating is symmetrically provided on both sides of the negative electrode collector of the composite negative electrode sheet, or the single-phase negative electrode active coating is provided on one side of the negative electrode collector and the first negative electrode active coating is provided on the other side of the negative electrode collector.
  • the composite battery cell includes a first negative electrode sheet and a blended negative electrode sheet, the negative electrode active material contained in the first negative electrode sheet is only one kind of first negative electrode active material, the blended negative electrode active coating provided on the blended negative electrode sheet includes blended negative electrode active material A and blended negative electrode active material B, and the blended negative electrode active material B is different from at least one of the first negative electrode active material and the blended negative electrode active material A.
  • A1 represents the number of first negative electrode sheets
  • A4 represents the number of blended negative electrode sheets
  • A1/A4 0.005-200.
  • the first negative electrode active material is artificial graphite
  • the blended negative electrode active material A is artificial graphite
  • the blended negative electrode active material B is a silicon-based material.
  • the composite battery cell also includes a positive electrode sheet and a separator.
  • the negative electrode sheet and the positive electrode sheet are arranged at intervals, and a separator is also provided between the negative electrode sheet and the positive electrode sheet;
  • the positive electrode sheet includes a first positive electrode sheet and a second positive electrode sheet, the first positive electrode sheet only includes iron-lithium positive electrode material, and the second positive electrode sheet only includes a ternary positive electrode material.
  • the negative electrode active coating provided on the first negative electrode sheet is the first negative electrode active coating
  • the blended negative electrode active coating is symmetrically provided on both sides of the negative electrode collector of the blended negative electrode sheet, or the blended negative electrode active coating is provided on one side of the negative electrode collector and the first negative electrode active coating is provided on the other side of the negative electrode collector.
  • the composite battery cell includes two composite negative electrode sheets, the composite negative electrode sheets include a composite negative electrode sheet A and a composite negative electrode sheet B, the single-phase negative electrode active coating provided on the composite negative electrode sheet A includes a single-phase negative electrode active coating A1 and a single-phase negative electrode active coating A2; the single-phase negative electrode active coating provided on the composite negative electrode sheet B includes a single-phase negative electrode active coating B1 and a single-phase negative electrode active coating B2, wherein the negative electrode active materials contained in the single-phase negative electrode active coating A1, the single-phase negative electrode active coating A2, the single-phase negative electrode active coating B1, and the single-phase negative electrode active coating B2, respectively, are only the single-phase negative electrode active materials A1 and the single-phase negative electrode active coating B2.
  • the single-phase negative electrode active material A1 is different from at least one of the single-phase negative electrode active material A2, the single-phase negative electrode active material B1 and the single-phase negative electrode active material B2.
  • the composite battery cell includes two blended negative electrode sheets, the blended negative electrode sheets include a blended negative electrode sheet A and a blended negative electrode sheet B, the blended negative electrode active coating A provided on the blended negative electrode sheet A includes a blended negative electrode active material A1 and a blended negative electrode active material A2; the blended negative electrode active coating B provided on the blended negative electrode sheet B includes a blended negative electrode active material B1 and a blended negative electrode active material B2, and the blended negative electrode active material A1 is different from at least one of the blended negative electrode active material A2, the blended negative electrode active material B1, and the blended negative electrode active material B2.
  • the composite battery cell includes a composite negative electrode sheet and a blended negative electrode sheet
  • the single-phase negative electrode active coating provided on the composite negative electrode sheet includes a single-phase negative electrode active coating A and a single-phase negative electrode active coating B
  • the negative electrode active materials contained in the single-phase negative electrode active coatings A and B respectively are only single-phase negative electrode active materials A and B
  • the blended negative electrode active coating provided on the blended negative electrode sheet includes a blended negative electrode active material A and a blended negative electrode active material B
  • the composite negative electrode active material A is different from at least one of the composite negative electrode active material B, the blended negative electrode active material A, and the blended negative electrode active material B.
  • the negative electrode active coatings located on different sides of the current collector respectively meet a specific K2 value range, thereby, the two sides of the current collector of the negative electrode sheet basically reach a state of capacity balance, so that the negative electrode sheet can have excellent energy density, rate performance, and cycle performance.
  • the negative electrode active material has a mass content of 90-98% in the negative electrode active coating layer containing the negative electrode active material.
  • the gram capacity of artificial graphite is 300-370 mAh/g
  • the gram capacity of natural graphite is 340-372 mAh/g
  • the gram capacity of hard carbon is 200-1000 mAh/g
  • the gram capacity of soft carbon is 100-800 mAh/g
  • the gram capacity of silicon-based material is 300-4200 mAh/g.
  • the surface density of each negative electrode active coating layer is 20-400 g/m 2 .
  • a battery comprising the composite battery cell as described above.
  • the battery provided by the present application can realize simultaneous charging and discharging of different negative electrode active materials, thereby making full use of the advantages of different negative electrode active materials to obtain a battery with good energy density, rate performance and cycle performance.
  • FIG1 is a schematic diagram of a feasible structure of a first negative electrode sheet
  • FIG2 is a schematic diagram of one possible structure of a composite negative electrode sheet
  • FIG3 is a schematic diagram of another feasible structure of a composite negative electrode sheet
  • FIG4 is a schematic diagram of one possible structure of a symmetrical hybrid negative electrode sheet
  • FIG5 is a schematic diagram of one possible structure of an asymmetric hybrid negative electrode sheet
  • FIG6 is a schematic diagram of the structure of a single combined battery cell
  • FIG7 is a schematic diagram of the structure of composite cells 1 to 8.
  • FIG. 8 is a schematic structural diagram of a composite battery cell 9 .
  • This embodiment uses different artificial graphites, natural graphites, hard carbons, soft carbons, and silicon-based materials to construct negative electrode sheets with different negative electrode active coating compositions, wherein the negative electrode sheet containing only a single negative electrode active material is used as the first negative electrode sheet, and the negative electrode sheet containing at least two negative electrode active materials is used as the second negative electrode sheet.
  • first negative electrode sheet In the first negative electrode sheet involved in this embodiment, its structural schematic diagram is shown in Figure 1, and negative electrode active coatings containing only one negative electrode active material are symmetrically arranged on the two sides of the negative electrode current collector, respectively marked as the first negative electrode active coating 1-1 and the second negative electrode active coating 1-2.
  • artificial graphite first negative electrode sheet artificial graphite with a gram capacity of 350 mAh/g is used as the negative electrode active material, artificial graphite, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed uniformly at a mass ratio of 96:1:1:2 to prepare a negative electrode coating slurry, and then the negative electrode coating slurry is coated on the two opposite sides of the negative electrode current collector respectively, and dried, so as to form a symmetrically arranged first negative electrode active coating 1-1 and a second negative electrode active coating 1-2 on the two sides of the negative electrode current collector, and the negative electrode active material contained in the first negative electrode active coating 1-1 and the second negative electrode active coating 1-2 is only artificial graphite.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the artificial graphite negative electrode sheet thus prepared is marked as an artificial graphite single-phase negative electrode sheet.
  • the negative electrode sheet including a negative electrode active coating with a surface density of 120 g/m 2 is marked as artificial graphite first negative electrode sheet (1)
  • the negative electrode sheet including a negative electrode active coating with a surface density of 200 g/m 2 is marked as artificial graphite first negative electrode sheet (2).
  • a first graphite negative electrode sheet (2) is produced.
  • FIG1 The structural schematic diagram of the artificial graphite first negative electrode sheet prepared as above is shown in FIG1 .
  • first natural graphite negative electrode sheet natural graphite with a gram capacity of 360 mAh/g is used as the negative electrode active material, natural graphite, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed uniformly at a mass ratio of 96:1:1:2 to form a negative electrode coating slurry, and then the negative electrode coating slurry is coated on the two opposite sides of the negative electrode current collector, respectively, and dried, so as to form a symmetrically arranged first negative electrode active coating 1-1 and a second negative electrode active coating 1-2 on the two sides of the negative electrode current collector, and the negative electrode active material contained in the first negative electrode active coating 1-1 and the second negative electrode active coating 1-2 is only natural graphite.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the natural graphite negative electrode sheet thus prepared is marked as a natural graphite first negative electrode sheet.
  • the negative electrode sheet including a negative electrode active coating with a surface density of 120 g/m 2 is marked as a natural graphite first negative electrode sheet (1)
  • the negative electrode sheet including a negative electrode active coating with a surface density of 50 g/m 2 is marked as a natural graphite first negative electrode sheet (2).
  • FIG1 The structural schematic diagram of the natural graphite first negative electrode sheet prepared as above is shown in FIG1 .
  • the first hard carbon negative electrode sheet hard carbon with a gram capacity of 500 mAh/g is used as the negative electrode active material, and the hard carbon, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed uniformly at a mass ratio of 96:1:1:2 to form a negative electrode coating slurry, and then the negative electrode coating slurry is coated on the two opposite sides of the negative electrode current collector, respectively, and dried, so as to form a symmetrically arranged first negative electrode active coating 1-1 and a second negative electrode active coating 1-2 on the two sides of the negative electrode current collector, and the negative electrode active material contained in the first negative electrode active coating 1-1 and the second negative electrode active coating 1-2 is only hard carbon.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the hard carbon negative electrode sheet thus prepared is marked as a hard carbon first negative electrode sheet.
  • the negative electrode sheet including a negative electrode active coating with a surface density of 90 g/ m2 is marked as the hard carbon first negative electrode sheet (1)
  • the negative electrode sheet including a negative electrode active coating with a surface density of 50 g/ m2 is marked as the hard carbon first negative electrode sheet (2).
  • FIG1 The structural schematic diagram of the hard carbon first negative electrode sheet prepared as above is shown in FIG1 .
  • the first negative electrode sheet of silicon-based material a silicon-based material with a gram capacity of 1800 mAh/g is used as the negative electrode active material, the silicon-based material, the conductive agent (SP), the binder sodium carboxymethyl cellulose (CMC), and the styrene-butadiene rubber (SBR) are mixed uniformly at a mass ratio of 96:1:1:2 to prepare a negative electrode coating slurry, and then the negative electrode coating slurry is coated on two opposite sides of the negative electrode current collector, respectively, and dried, so as to form a symmetrically arranged first negative electrode active coating A 1-1 and a negative electrode active coating B 1-2 on two sides of the negative electrode current collector, and the negative electrode active coating A 1-1 and the negative electrode active coating B 1-2 contained negative electrode active
  • the material is only silicon-based material.
  • the silicon-based material negative electrode sheet thus prepared is marked as the first silicon-based material negative electrode sheet.
  • the negative electrode sheet with a negative electrode active coating surface density of 120 g/m 2 is marked as the first silicon-based material negative electrode sheet (1)
  • the negative electrode sheet with a negative electrode active coating surface density of 50 g/m 2 is marked as the first silicon-based material negative electrode sheet (2).
  • FIG1 The structural schematic diagram of the first negative electrode sheet of the silicon-based material prepared above is shown in FIG1 .
  • FIG. 2 One of the feasible structural forms of the composite negative electrode sheet is shown in Figure 2, in which a single-phase negative electrode active coating A2-1 and a single-phase negative electrode active coating B 2-2 that are composited with each other are symmetrically arranged on the two sides of the negative electrode current collector, and the negative electrode active material contained in the single-phase negative electrode active coating A2-1 is only negative electrode active material A, and the negative electrode active material contained in the single-phase negative electrode active coating B 2-2 is only negative electrode active material B, and the negative electrode active material A is different from the negative electrode active material B.
  • FIG. 3 Another feasible structural form of the composite negative electrode sheet is shown in Figure 3, in which a single-phase negative electrode active coating A3-1 and a single-phase negative electrode active coating B 3-2 that are composited with each other are arranged on one side of the negative electrode current collector, and a single-phase negative electrode active coating C 3-3 is arranged on the other side of the negative electrode current collector, the negative electrode active material contained in the single-phase negative electrode active coating A3-1 is only one kind of negative electrode active material A, the negative electrode active material contained in the single-phase negative electrode active coating B 3-2 is only one kind of negative electrode active material B, the negative electrode active material contained in the single-phase negative electrode active coating C 3-3 is only one kind of negative electrode active material C, and the first negative electrode active material C is different from at least one of the first negative electrode active material A and the negative electrode active material B.
  • Artificial graphite with a gram capacity of 350 mAh/g was used as the negative electrode active material, and the artificial graphite, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed evenly in a mass ratio of 96:1:1:2 to prepare negative electrode coating slurry A; hard carbon with a gram capacity of 500 mAh/g was used as the negative electrode active material, and the hard carbon, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed evenly in a mass ratio of 96:1:1:2 to prepare negative electrode coating slurry B.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the negative electrode coating slurry A is coated on one side of the negative electrode current collector and dried to form a single-phase negative electrode active coating A2-1. Then, the negative electrode coating slurry B is coated on the surface of the single-phase negative electrode active coating A2-1 and dried to form a single-phase negative electrode active coating B2-2. Then, the above operation is repeated on the other side of the negative electrode current collector to symmetrically arrange the single-phase negative electrode active coating A2-1 (using artificial graphite as the negative electrode active material) and the single-phase negative electrode active coating B2-2 (using hard carbon as the negative electrode active material) composited with each other on the two sides of the negative electrode current collector.
  • the symmetrical negative electrode sheet thus prepared is marked as an artificial graphite-hard carbon composite negative electrode sheet.
  • the symmetrical negative electrode sheet including the single-phase negative electrode active coating A2-1 with an area density of 80 g/ m2 and the single-phase negative electrode active coating B2-2 with an area density of 40 g/ m2 is used.
  • the composite negative electrode sheet is marked as artificial graphite-hard carbon composite negative electrode sheet (1); the surface density of the single-phase negative electrode active coating A2-1 is 160g/ m2 , and the surface density of the single-phase negative electrode active coating B2-2 is 80g/ m2 .
  • the symmetrical composite negative electrode sheet thus prepared is marked as artificial graphite-hard carbon composite negative electrode sheet (2).
  • FIG2 The structural schematic diagram of the artificial graphite-hard carbon composite negative electrode sheet prepared above is shown in FIG2 .
  • the second negative electrode sheet involved in this embodiment refers to a negative electrode sheet in which at least one layer of all the negative electrode active coatings contained therein is a blend of at least two different negative electrode active materials.
  • a blended negative electrode active coating 4-1 is symmetrically provided on both sides of the negative electrode current collector, and the blended negative electrode active coating 4-1 contains two different types of negative electrode active materials (a first negative electrode active material and a second negative electrode active material).
  • FIG5 Another feasible structural form of the second negative electrode sheet is shown in FIG5 , where a blended negative electrode active coating 5-1 is provided on one side of the negative electrode current collector, and the blended negative electrode active coating 5-1 contains two different types of negative electrode active materials (a first negative electrode active material and a second negative electrode active material), and a single-phase negative electrode active coating 5-2 using only one negative electrode active material is provided on the other side of the negative electrode current collector.
  • a blended negative electrode active coating 5-1 is provided on one side of the negative electrode current collector
  • the blended negative electrode active coating 5-1 contains two different types of negative electrode active materials (a first negative electrode active material and a second negative electrode active material), and a single-phase negative electrode active coating 5-2 using only one negative electrode active material is provided on the other side of the negative electrode current collector.
  • Artificial graphite with a gram capacity of 350 mAh/g and a silicon-based material with a gram capacity of 1800 mAh/g are used as negative electrode active materials.
  • the artificial graphite and the silicon-based material are mixed in a mass ratio of 9:1 to obtain a blended negative electrode active material, and then the blended negative electrode active material, a conductive agent (SP), a binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:1:1:2 to prepare a negative electrode coating slurry.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the negative electrode coating slurry is coated on two opposite sides of the negative electrode current collector respectively and dried, thereby forming two symmetrically arranged layers of blended negative electrode active coatings 4-1 on the two sides of the negative electrode current collector.
  • the negative electrode active material contained in each layer of blended negative electrode active coating 4-1 is blended artificial graphite and silicon-based material.
  • the surface density of each layer of blended negative electrode active coating 4-1 is 90 g/m 2 .
  • the blended negative electrode sheet thus prepared is marked as symmetrical blended negative electrode sheet (1); the surface density of each layer of blended negative electrode active coating 4-1 is 110 g/m 2 .
  • the blended negative electrode sheet thus prepared is marked as symmetrical blended negative electrode sheet (2).
  • FIG4 The structural schematic diagram of the symmetrical blended negative electrode sheet prepared above is shown in FIG4 .
  • Artificial graphite with a gram capacity of 350mAh/g and a silicon-based material with a gram capacity of 1800mAh/g are used as negative electrode active materials.
  • the artificial graphite and the silicon-based material are mixed in a mass ratio of 9:1 to obtain a blended negative electrode active material, and then the blended negative electrode active material, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:1:1:2 to form a negative electrode coating slurry A.
  • SP conductive agent
  • CMC binder sodium carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • the artificial graphite, conductive agent (SP), binder sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:1:1:2 to form a negative electrode coating slurry B.
  • the negative electrode coating slurry A is coated on one side of the negative electrode current collector and dried to form a blended negative electrode active coating 5-1, and then the negative electrode coating slurry B is coated on the other side of the negative electrode current collector and dried to form a first negative electrode active coating 5-2.
  • the surface density of the blended negative electrode active coating 5-1 is 110 g/m 2
  • the surface density of the first negative electrode active coating 5-2 is 120 g/m 2.
  • the blended negative electrode sheet thus prepared is marked as an asymmetric blended negative electrode sheet.
  • the asymmetric blended negative electrode sheet including the blended negative electrode active coating 5-1 with a surface density of 110 g/m 2 and the first negative electrode active coating 5-2 with a surface density of 120 g/m 2 is marked as an asymmetric blended negative electrode sheet.
  • FIG5 The structural schematic diagram of the asymmetric blended negative electrode sheet prepared above is shown in FIG5 .
  • Formula I Calculate the total capacity of the above-mentioned negative electrode sheet prepared in this embodiment; in Formula I, Qn represents the area of any layer of negative electrode active coating included in the negative electrode sheet, Sn represents the surface density of any layer of negative electrode active coating included in the negative electrode sheet, in the layer of negative electrode active coating, Cm represents the gram capacity of any negative electrode active material, Wm represents the mass percentage of the negative electrode active material in the layer of negative electrode active coating, i represents the number of categories of negative electrode active materials included in each layer of negative electrode active coating, i is an integer greater than or equal to 1, k represents the number of layers of negative electrode active coating included in each negative electrode sheet, k is an integer greater than or equal to 1.
  • K1 involved in Table 1 is the ratio of the total capacity of negative electrode sheet A to the total capacity of negative electrode sheet B.
  • Formula I It represents the capacity level of a certain layer of negative electrode active coating in the negative electrode sheet. After calculating the capacity of each layer of negative electrode active coating separately, the calculation results are summed up, that is, according to Calculate and finally get the capacity level of the entire negative electrode sheet.
  • the total capacity is calculated as follows: the mass content of the negative electrode active material used in the first negative electrode active coating A 1-1 is W1, the gram capacity of the negative electrode active material is C1, and the surface density of the first negative electrode active coating A 1-1 is S1. Then, the capacity of the first negative electrode active coating A 1-1 is Q1 ⁇ S1 ⁇ W1 ⁇ C1. Correspondingly, the capacity of the first negative electrode active coating B 1-2 is also calculated in the above manner. Since the first negative electrode active coating A 1-1 and the first negative electrode active coating B 1-2 are symmetrically arranged, the total capacity of the first negative electrode sheet is 2 ⁇ Q1 ⁇ S1 ⁇ W1 ⁇ C1.
  • the total capacity is calculated as follows: on either side of the negative electrode current collector, the mass content of the negative electrode active material in the single-phase negative electrode active coating A2-1 is W1, the gram capacity of the negative electrode active material is C1, and the surface density of the single-phase negative electrode active coating A2-1 is S1, then the capacity of the single-phase negative electrode active coating A2-1 is Q1 ⁇ S1 ⁇ W1 ⁇ C1, the mass content of the negative electrode active material in the single-phase negative electrode active coating B 2-2 is W2, the gram capacity of the negative electrode active material is C2, and the surface density of the single-phase negative electrode active coating B 2-2 is S2, then the capacity of the single-phase negative electrode active coating B 2-2 is Q2 ⁇ S2 ⁇ W2 ⁇ C2, accordingly, the capacity of the negative electrode active coating on this side is (Q1 ⁇ S1 ⁇ W1 ⁇ C1+Q2 ⁇ S2 ⁇ W2 ⁇ C2), in addition, the capacity of the negative electrode active coating on the other side of the negative electrode active coating
  • the calculation method of its total capacity is as follows: in one layer of the blended negative electrode active coating 4-1, the mass content of one negative electrode active material A is W1, and the gram capacity of the negative electrode active material is C1, the mass content of the other negative electrode active material B is W2, and the gram capacity of the negative electrode active material is C2, and the surface density of the blended negative electrode active coating 4-1 is S1, then the capacity of the blended negative electrode active coating 4-1 is Q1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2), and accordingly, the capacity of the other layer of the blended negative electrode active coating 4-1 is also calculated in the above manner. Since the two layers of the blended negative electrode active coating 4-1 are symmetrically arranged, the total capacity of the second negative electrode sheet is 2 ⁇ (Q1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2)).
  • the total capacity is calculated as follows: in the blended negative electrode active coating 5-1 containing multiple negative electrode active materials, the mass content of one negative electrode active material A is W1, the gram capacity of the negative electrode active material is C1, the mass content of another negative electrode active material B is W2, the gram capacity of the negative electrode active material is C2, and the surface density of the blended negative electrode active coating 5-1 is S1, then the capacity of the blended negative electrode active coating 5-1 is Q 1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2), in the first active coating 5-2 containing only one negative electrode active material, the mass content of the negative electrode active material A is W3, the gram capacity of the first negative electrode active material is C3, the surface density of the first negative electrode active coating 5-2 is S2, and the capacity of the first negative electrode active coating 5-2 is S2 ⁇ W3 ⁇ C3; the total capacity of the asymmetric blended negative electrode sheet is (Q1 ⁇ S1 ⁇ (W1 ⁇ C1+W2 ⁇ C2)+
  • This embodiment uses different negative electrode sheets and positive electrode sheets and separators prepared in Example 1 to prepare different battery cells.
  • the first positive electrode sheet used in this embodiment is prepared as follows: lithium iron phosphate is used as the positive electrode active material, lithium iron phosphate, binder PVDF, and conductive agent acetylene black are mixed in a mass ratio of 90:5:5, and then solvent N-methylpyrrolidone (NMP) is added and stirred evenly to prepare a positive electrode coating slurry; then the above-mentioned positive electrode coating slurry is respectively coated on two back-to-back sides of the positive electrode current collector, and dried, so as to form two symmetrically arranged positive electrode active coating layers on the two sides of the positive electrode current collector.
  • NMP solvent N-methylpyrrolidone
  • the second positive electrode sheet used in this embodiment is prepared as follows: a ternary material is used as the positive electrode active material, the ternary material, a binder PVDF, and a conductive agent acetylene black are mixed in a mass ratio of 90:5:5, and then a solvent N-methylpyrrolidone (NMP) is added and stirred evenly to prepare a positive electrode coating slurry; then the above-mentioned positive electrode coating slurry is respectively coated on two back-to-back sides of the positive electrode current collector, and dried, so as to form two symmetrically arranged positive electrode active coating layers on the two sides of the positive electrode current collector.
  • NMP solvent N-methylpyrrolidone
  • the diaphragm used in this embodiment is a polyethylene film.
  • the electrolyte used in this embodiment is prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then sufficiently dried lithium salt LiPF6 is dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • the negative electrode sheet prepared in Example 1 is used in different matching ways with the positive electrode sheet prepared in this example to construct a battery cell, and the cells using different negative electrode sheet combinations are numbered.
  • the specific grouping is shown in Table 2 and Table 3, wherein the cell shown in Table 2 is a single combination cell using only one negative electrode sheet, and the cell shown in Table 3 is a composite cell using two negative electrode sheets.
  • the negative electrode sheet capacity distribution of the composite cell using the negative electrode sheets is shown in Table 4.
  • K1 is the ratio of the total capacity of the negative electrode sheet A to the total capacity of the negative electrode sheet B in the composite cell.
  • a battery using single combination cells 1 to 6 is prepared as follows: 50 negative electrode sheets 6-1 and 49 first positive electrode sheets 6-2 are used, so that the negative electrode sheets 6-1 and the first positive electrode sheets 6-2 are arranged in sequence, and each electrode sheet is separated by a diaphragm 6-3, and a single combination cell is obtained by a stacking or winding process.
  • the structural schematic diagram of the single combination cell is shown in Figure 6; then the single combination cell is placed in a battery shell, and then the battery shell is subjected to treatments such as welding the pole ears and baking. After the moisture content is tested to be qualified, an appropriate amount of electrolyte is injected into the battery shell, and the battery is packaged, and the battery is prepared by aging, formation, and vacuum packaging.
  • the battery using the single combination battery cell 7-8 is prepared as follows: 50 negative electrode sheets 6-1 and 49 second positive electrode sheets 6-2 are used, and the negative electrode sheets 6-1 and the second positive electrode sheets 6-2 are arranged in sequence, and the electrode sheets are separated by a diaphragm 6-3, and the single combination battery cell is obtained by a lamination or winding process.
  • the structural schematic diagram of the single combination battery cell is shown in FIG6; and then the single combination battery cell is The assembled battery cell is placed in a battery shell, and then the battery shell is subjected to treatments such as welding the pole ears and baking. After the moisture content is tested to be qualified, an appropriate amount of electrolyte is injected into the battery shell, and the battery is packaged.
  • the battery is prepared through aging, formation, and vacuum packaging.
  • a battery using composite cells 1 to 8 is prepared as follows: 101 negative electrode sheets (including 51 negative electrode sheets A 7-1 and 50 negative electrode sheets B 7-2) and 100 first positive electrode sheets 7-3 are used, and the negative electrode sheets and the positive electrode sheets are arranged in sequence of negative electrode sheet A 7-1, first positive electrode sheet 7-3, and negative electrode sheet B 7-2, and each electrode sheet is separated by a diaphragm 7-4.
  • the structural schematic diagram of the composite cell is shown in Figure 7; then the composite cell is placed in a battery casing, and then the battery casing is subjected to treatments such as welding the pole ears and baking. After the moisture content is tested to be qualified, an appropriate amount of electrolyte is injected into the battery casing, and the battery is packaged, and the battery is prepared by aging, formation, and vacuum packaging.
  • a battery using the composite battery cell 9 is prepared as follows: 101 negative electrode sheets (including 51 negative electrode sheets A 8-1 and 50 negative electrode sheets B 8-2) and 100 positive electrode sheets (including 50 first positive electrode sheets 8-3 and 50 second positive electrode sheets 8-5) are used, wherein one negative electrode sheet A 8-1 and one first positive electrode sheet 8-3 are defined as a first battery cell assembly unit, one second positive electrode sheet 8-5 and one negative electrode sheet B 8-2 are defined as a second battery cell assembly unit, 50 first battery cell assembly units are arranged in sequence, 50 second battery cell assembly units are arranged in sequence, and the negative electrode sheets and the positive electrode sheets are arranged in sequence in the order of arranging the 50 first battery cell assembly units, the negative electrode sheet A, and the 50 second battery cell assembly units.
  • Each electrode piece is separated by a diaphragm 8-4, and the structural schematic diagram of the composite battery cell is shown in Figure 8; then the composite battery cell is placed in a battery shell, and then the battery shell is subjected to treatments such as welding the electrode ears and baking. After the moisture content is tested to be qualified, an appropriate amount of electrolyte is injected into the battery shell, and the battery is packaged, and the battery is prepared through aging, formation, and vacuum packaging.
  • Example 2 the battery prepared in Example 2 was used as a test object to conduct relevant performance tests.
  • the test battery was charged to 4.25V at 0.33C constant current and constant voltage, cut off at 0.02C, and then discharged to 2.8V at 0.33C.
  • the capacity, average voltage and cell mass were recorded.
  • the test battery was charged to 4.25V at 0.33C constant current and constant voltage, cut off at 0.02C, then discharged at 0.33C for 90min, left for 10min, and the terminal voltage V1 was recorded; then discharged at 2C (current I) for 10s, and the discharge terminal voltage V2 was recorded.
  • the tested batteries were placed in a 45°C constant temperature box, charged at 1C constant current and constant voltage, cut off at 0.02C, and then discharged at 1C, cycled to 80% SOC, and the number of cycles was recorded.
  • the relevant performance test results of the battery prepared in Example 2 are shown in Table 5.
  • the battery prepared by composite battery cells 1 to 9 contains two negative electrode sheets.
  • the test results show that the DC impedance of the battery prepared by composite battery cells 1 to 9 is low, and the energy density and cycle performance are good. This is mainly because the high-rate long-cycle electrode sheet and the high-safety and high-energy-density electrode sheet are mixed in the composite battery cell to achieve the combination of two systems, and obtain a battery cell with two different negative electrode sheets coexisting.
  • the prepared battery has excellent energy density, cycle performance and safety performance. It can be seen that the composite battery provided in this application can give full play to the synergistic advantages of different kinds of negative active materials, so that the energy density, rate performance and cycle performance of the composite battery cell are improved as a whole relative to the battery cell using a single negative active material.
  • Composite cells 1, 2, composite cells 3, 4, composite cells 5, 6, composite cells 7, 8 are compared respectively.
  • the ratio K1 of the total capacity of negative electrode sheet A to the total capacity of negative electrode sheet B in composite cell 2 does not meet 0.8-1.2.
  • the test results show that the battery prepared by composite cell 1 has a lower DC impedance, and better energy density and cycle performance. This is mainly because the different negative electrode sheets of composite cell 1 meet a specific K1 value range, thereby basically achieving a state of capacity balance between different negative electrode sheets.
  • the test results of composite cells 3, 5, and 7 are the same as above.
  • the composite cell provided in the present application makes the total capacity ratio between different negative electrode sheets meet the K1 value range, and the different negative electrode sheets basically reach a state of capacity balance, thereby enabling different types of negative electrode active materials to give full play to their synergistic advantages, thereby improving the comprehensive performance of the composite cell.
  • the battery made of composite cell 9 contains two different positive electrodes.
  • the test results show that the battery made of composite cell 9 has lower DC impedance, and has higher energy density and cyclability. The performance is better, mainly because the composite battery cell 9 includes two positive electrode sheets, and the second positive electrode sheet (the positive electrode active material used is a ternary positive electrode material) is adjacent to the mixed negative electrode sheet including the silicon-based material, which further improves the overall performance of the battery.
  • the composite battery cell provided by the present application integrates different negative electrode active materials and positive electrode active materials, so that various positive and negative electrode sheets can play a synergistic advantage, further improving the energy density, rate performance, and cycle performance of the composite battery cell.

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Abstract

一种复合电芯，包括至少两种负极片，所含有的负极活性材料包括人造石墨、天然石墨、硬碳、软碳、硅基材料中的至少两种；复合电芯包括第一负极片、第二负极片中的至少一种，第一负极片仅包括一种负极活性材料，第二负极片包括至少两种不同种类的负极活性材料；其中，第二负极片包括复合负极片、共混负极片中的至少一种；复合负极片在负极集流体的一侧至少设有两层单相负极活性涂层；共混负极片设有的负极活性涂层中至少一层为共混负极活性涂层。

Description

一种复合电芯及应用其的电池
本申请要求在2023年05月23日提交中国专利局、申请号为2023106067983的中国专利申请以及在2023年05月23日提交中国专利局、申请号为2023212655352的中国专利申请早的优先权，以上申请的全部内容通过引用结合在本申请中。
技术领域
本申请属于电池技术领域，具体地，涉及一种复合电芯及应用其的电池。
背景技术
随着锂离子电池技术的发展，市场对锂电池的能量密度、倍率性能、高低温性能等性能提出了越来越高的需求，相应的，也对负极体系的设计提出来更高的要求。常用负极活性材料分为碳负极材料和非碳负极材料，碳负极材料有人造石墨、天然石墨、硬碳、软碳等，非碳负极材料主要为硅基材料。其中，人造石墨具有优异的循环、倍率、高温性能，各项性能比较均衡，与电解液的相容性也比较好，但生产工序复杂、成本高；天然石墨具备低成本和高比容量优势，但其表面缺陷多导致首效低，膨胀大导致循环寿命低，各向异性强导致倍率性能差，并且一致性低于人造石墨；硬碳是难石墨化碳，其结晶分散，层间距大，锂离子很容易进出，结构稳定，因此具有极好的倍率性能和循环稳定性，但缺点是容量低、首效低、压实低，并且容易产气。软碳是易石墨化碳，由于结晶度低，与电解液相容性好，故低温性能优异，倍率性能良好，但是其容量低、首效低，无明显充放电平台。硅基系列主要为硅碳、硅氧材料，其理论比容量极其高，硅的嵌锂电位高于碳材料，析锂风险小，安全性高，但硅基脱嵌锂过程中体积变化极大，颗粒易破碎粉化，导致容易失效，且首效低、循环差。
基于不同负极活性材料所具有的优势不同，目前行业中一般将不同种类的上述负极活性材料混合后形成的浆料直接涂布在集流体的表面上以制备负极片。然而，不同种类的负极活性材料由于材料特性各异，只采用直接混合的方式，往往由于材料混合不均匀、材料搭配方式不合理而使得不同种类的负极活性材料无法充分发挥其材料优势，甚至使集成了不同种类负极活性材料的电芯在某些性能上还不如仅采用单一活性材料的电芯。此外，对于某些特性不同的负极活性材料，如首效特性，当其各自所制备的负极片在同一电芯复合时，若搭配同一种正极片，则不能很好的发挥上述两种负极活性材料的优势，基于此，如何在同一电芯中 集成不同负极活性材料并发挥上述负极活性材料的协同优势，是本领域技术人员在研究中急需解决的技术问题。
发明内容
本申请通过提供一种复合电芯及应用其的电池，充分发挥不同种负极活性材料的协同优势，进一步提高电池的能量密度、倍率性能、循环性能。
根据本申请的第一个方面，提供一种复合电芯，包括至少两种负极片，复合电芯所含有的负极活性材料包括人造石墨、天然石墨、硬碳、软碳、硅基材料中的至少两种，负极活性材料用于构造负极片的负极活性涂层；复合电芯包括第一负极片、第二负极片中的至少一种，第一负极片仅包括一种负极活性材料，第二负极片包括至少两种不同种类的负极活性材料；其中，第二负极片包括复合负极片、共混负极片中的至少一种；复合负极片在负极集流体的一侧至少设有两层单相负极活性涂层，单相负极活性涂层中仅含有一种负极活性材料；共混负极片设有的负极活性涂层中至少一层为共混负极活性涂层，共混负极活性涂层中至少包括两种互不相同的负极活性材料。该复合电芯能够充分发挥不同种负极活性材料的协同优势，使得上述复合电芯的能量密度、倍率性能、循环性能相对于采用单一负极活性材料的电芯而言，得到整体的提高。
在一实施例中，在复合电芯中，任一片负极片的总容量与其余任一片负极片的总容量之比K1＝0.8～1.2，每片负极片的总容量以式Ⅰ表示：在式Ⅰ中，Qn表示负极片所包括的任一层负极活性涂层的面积，Sn表示负极片所包括的任一层负极活性涂层的面密度，在该层负极活性涂层中，Cm表示任一种负极活性材料的克容量，Wm表示该种负极活性材料在该层负极活性涂层中的质量百分比，i表示每层负极活性涂层所包括的负极活性材料的类别数量，i为大于等于1的整数，k表示每片负极片所包括的负极活性涂层的层数，k为大于等于1的整数；本申请所提供的电池的复合电芯集成了至少两种负极活性材料，能够通过对所采用的负极活性材料种类进行挑选、调节不同种类负极活性材料的用量，以使复合电芯灵活地适应各种不同的产品要求。在上述复合电芯中，不同负极片之间满足特定的K1值范围，由此，不同的负极片之间基本达到容量平衡的状态，从而能够对复合电芯中由于集成了不同种类的负极活性材料之间所产生的阻抗等其他劣化效果起到有效的缓解作用，基于此，该复合电芯能够充分发挥不同种负极活性材料的协同优势，使得上述复合电芯的能量密度、倍率性能、循环性能相对于采用单一负极活性材料的电芯而 言，得到整体的提高。
分别以第一负极片、第二负极片举例说明不同式Ⅰ的运算方式，式Ⅰ， 例如，第一负极片的一种可选的实施方式(负极活性涂层的设置：集流体单侧单层涂布、两侧对称设置)：第一负极片仅采用了一种负极活性材料，利用该种负极活性材料分别在负极集流体的两侧各设置了一层负极活性涂层，分别位于负极集流体两侧的两层负极活性涂层互为对称设置，以其所采用的负极活性材料在其中一层负极活性涂层中的质量含量为W1，以该负极活性材料的克容量为C1，该层负极活性涂层的面密度为S1，该层负极活性涂层的面积为Q1，则该层负极活性涂层的容量为Q1×S1×W1×C1，相应的，另一层负极活性涂层的容量也按照上述方式进行计算，由于两层负极活性涂层对称设置，所以该第一负极片的总容量为2×Q1×S1×W1×C1。例如，复合负极片的第一种可选的实施方式(负极活性涂层的设置：集流体单侧分层涂布、两侧对称设置)：复合负极片采用了两种负极活性材料，标记为第一负极活性材料和第二负极活性材料，在负极集流体的一侧依次设置仅含有第一负极活性材料单种负极活性材料的第一负极活性涂层和仅含有第二负极活性材料单种负极活性材料的第二负极活性涂层，然后在负极集流体的另一侧对应地设置分别与第一负极活性涂层、第二负极活性涂层对称的负极活性涂层；在负极集流体的任一侧，以其第一负极活性材料在第一负极活性涂层中的质量含量为W1，以该第一负极活性材料的克容量为C1，第一负极活性涂层的面密度为S1，第一负极活性涂层的面积为Q1，则第一负极活性涂层的容量为Q1×S1×W1×C1，以其第二负极活性材料在第二负极活性涂层中的质量含量为W2，以该第二负极活性材料的克容量为C2，第二负极活性涂层的面密度为S2，第二负极活性涂层的面积为Q2，则第二负极活性涂层的容量为Q2×S2×W2×C2，相应地，该侧的负极活性涂层容量为(Q1×S1×W1×C1+Q2×S2×W2×C2)，另外，位于负极集流体另一侧的负极活性涂层的容量也按照上述方式进行计算，由于在负极集流体的另一侧设置的负极活性涂层分别与第一负极活性涂层、第二负极活性涂层互为对称，所以该第一负极片的总容量为2×(Q1×S1×W1×C1+Q2×S2×W2×C2)。例如，复合负极片的第二种可选的实施方式(负极活性涂层的设置：集流体单侧分层涂布或单层涂布、两侧不对称设置)：复合负极片采用了三种负极活性材料，标记为第一负极活性材料、第二负极活性材料和第三负极活性材料，在负极集流体的一侧依次设置仅含有第一负极活性材料单种负极活性材料的第一负极活性涂层和仅含有第二负极活性材料单种负极活性材料的第二负极活性涂层，然后在负极集流体的另一侧设置仅含有第三负极活性材料单种负极活性材料的第三负极活性涂层； 在负极集流体设置双层负极活性涂层的一侧，以其第一负极活性材料在第一负极活性涂层中的质量含量为W1，以该第一负极活性材料的克容量为C1，第一负极活性涂层的面密度为S1，第一负极活性涂层的面积为Q1，则第一负极活性涂层的容量为Q1×S1×W1×C1，以其第二负极活性材料在第二负极活性涂层中的质量含量为W2，以该第二负极活性材料的克容量为C2，第二负极活性涂层的面密度为S2，第二负极活性涂层的面积为Q2，则第二负极活性涂层的容量为Q2×S2×W2×C2而相应的，该侧的负极活性涂层容量为(Q1×S1×W1×C1+Q2×S2×W2×C2)；在负极集流体设置单层负极活性涂层的一侧，以其第三负极活性材料在第三负极活性涂层中的质量含量为W3，以该第三负极活性材料的克容量为C3，第三负极活性涂层的面密度为S3，第三负极活性涂层的面积为Q3，则第一负极活性涂层的容量为Q3×S3×W3×C3；则该第一负极片的总容量为(Q1×S1×W1×C1+Q2×S2×W2×C2+Q3×S3×W3×C3)。例如，共混负极片的第一种可选的实施方式(负极活性涂层的设置：集流体单侧单层涂布、两侧对称设置)：共混负极片采用两种负极活性材料，标记为第一负极活性材料和第二负极活性材料，利用由第一负极活性材料和第二负极活性材料共混而成的浆料分别在负极集流体的两侧各设置了一层负极活性涂层，分别位于负极集流体两层的两层负极活性涂层互为对称设置，在其中一层负极活性涂层中，第一负极活性材料的质量含量为W1，以第一负极活性材料的克容量为C1，第二负极活性材料的质量含量为W2，以第二负极活性材料的克容量为C2，该层负极活性涂层的面密度为S1，该层负极活性涂层的面积为Q1，则该层负极活性涂层的容量为Q1×S1×(W1×C1+W2×C2)，相应的，另一层负极活性涂层的容量也按照上述方式进行计算，由于两层负极活性涂层对称设置，所以该第二负极片的总容量为2×(Q1×S1×(W1×C1+W2×C2))。例如，共混负极片的第二种可选的实施方式(负极活性涂层的设置：集流体单侧单层涂布、两侧不对称设置)：共混负极片采用了三种负极活性材料，标记为第一负极活性材料、第二负极活性材料和第三负极活性材料，利用由第一负极活性材料和第二负极活性材料共混而成的浆料在负极活性涂层的一侧设置第一负极活性涂层，然后在负极集流体的另一侧设置仅含有第三负极活性材料单种负极活性材料的第二负极活性涂层；在第一负极活性涂层中，第一负极活性材料的质量含量为W1，以第一负极活性材料的克容量为C1，第二负极活性材料的质量含量为W2，以第二负极活性材料的克容量为C2，第一负极活性涂层的面密度为S1，第一负极活性涂层的面密度为Q1，第一负极活性涂层的容量为Q1×S1×(W1×C1+W2×C2)；在第二负极活性涂层中，第三负极活性材料的质量含量为W3，以第三负极活性材料的克容量为C3，第二负极活性 涂层的面密度为S2，第二负极活性涂层的容量为Q2×S2×W3×C3；该第二负极片的总容量为(Q1×S1×(W1×C1+W2×C2)+Q2×S2×W3×C3)。
在一实施例中，复合电芯包括两种第一负极片，第一负极片包括第一负极片A和第一负极片B，第一负极片A所含有的负极活性材料仅为第一负极活性材料A一种，第一负极片B中所含有的负极活性材料仅为第一负极活性材料B一种，且第一负极活性材料A与第一负极活性材料B的种类互不相同。
在一实施例中，第一负极活性材料A为人造石墨，第一负极活性材料B为天然石墨。在上述复合电芯中，采用了仅含有人造石墨的负极片和仅含有天然石墨的负极片并联，使电芯中同时集成了人造石墨、天然石墨的优势，利用人造石墨具有优异的循环性能和倍率性能，降低了由于天然石墨表面缺陷多导致的首效低的问题和膨胀大导致的循环寿命低的问题，从而提升了含有天然石墨的负极活性涂层的倍率性能和循环性能，同时，天然石墨能够发挥其高容量、高压实、低成本的特性，进而在实现含有两种上述两种负极活性材料的电芯同时充放电的过程中，充分发挥两种材料的优势，形成优势互补。并且，上述负极片均仅采用一种负极活性材料，有利于极片的批量制作，适合工业化生产。
在一实施例中，在复合电芯中，以A1表示第一负极片A的片数，以A2表示第一负极片B的片数，A1/A2＝0.005～200。
在一实施例中，第一负极片A所设有的负极活性涂层为第一负极活性涂层A，第一负极片B所设有的负极活性涂层为第一负极活性涂层B；在第一负极片A的负极集流体的两侧对称设有第一负极活性涂层A，在第一负极片B的负极集流体的两侧对称设有第一负极活性涂层B。
在一实施例中，复合电芯包括第一负极片和复合负极片，第一负极片所含有的负极活性材料仅为第一负极活性材料一种，复合负极片所设有的单相负极活性涂层包括单相负极活性涂层A和单相负极活性涂层B，其中，单相负极活性涂层A中所含有的负极活性材料仅为单相负极活性材料A一种，单相负极活性涂层B中所含有的负极活性材料仅为单相负极活性材料B一种，且单相负极活性材料B与第一负极活性材料、单相负极活性材料A中的至少一种互不相同。
在一实施例中，第一负极活性材料为人造石墨，单相负极活性材料A为人造石墨，单相负极活性材料B为硬碳。在上述复合电芯中，采用人造石墨-硬碳负极片和人造石墨负极片搭配使用，由于硬碳具有层间距大、结构稳定的优势，进而使含有硬碳的负极活性涂层的 倍率性能和循环稳定性达到较高水平，同时，人造石墨具有容量高、与电解液相容性好的优势，进而在实现含有两种上述两种负极活性材料的电芯同时充放电的过程中，充分利用两种物质的优势，发挥协同增效作用，使复合电芯兼具高能量密度、高倍率、长循环的优势。
在一实施例中，在复合电芯中，以A1表示第一负极片的片数，以A3表示复合负极片的片数，A1/A3＝0.005～200。
在一实施例中，在复合负极片的集流体同一侧，沿远离集流体表面的方向上，单相负极活性涂层A和单相负极活性涂层B依次设置。
在一实施例中，第一负极片所设有的负极活性涂层为第一负极活性涂层；在复合负极片的负极集流体的两侧对称设有单相负极活性涂层，或，在负极集流体的一侧设有单相负极活性涂层，在负极集流体的另一侧设有第一负极活性涂层。
在一实施例中，复合电芯包括第一负极片和共混负极片，第一负极片所含有的负极活性材料仅为第一负极活性材料一种，共混负极片所设有的共混负极活性涂层包括共混负极活性材料A和共混负极活性材料B，且共混负极活性材料B与第一负极活性材料、共混负极活性材料A中的至少一种互不相同。
在一实施例中，在复合电芯中，以A1表示第一负极片的片数，以A4表示共混负极片的片数，A1/A4＝0.005～200。
在一实施例中，第一负极活性材料为人造石墨，共混负极活性材料A为人造石墨，共混负极活性材料B为硅基材料。
在一实施例中，复合电芯还包括正极片和隔膜，在复合电芯中，负极片、正极片间隔设置，负极片和正极片之间还设有隔膜；正极片包括第一正极片和第二正极片，第一正极片仅包括铁锂正极材料，第二正极片仅包括三元正极材料。
在一实施例中，第一负极片所设有的负极活性涂层为第一负极活性涂层，在共混负极片的负极集流体的两侧对称设有共混负极活性涂层，或，在负极集流体的一侧设有共混负极活性涂层，在负极集流体的另一侧设有第一负极活性涂层。
在一实施例中，复合电芯包括两种复合负极片，复合负极片包括复合负极片A和复合负极片B，复合负极片A所设有的单相负极活性涂层包括单相负极活性涂层A1和单相负极活性涂层A2；复合负极片B所设有的单相负极活性涂层包括单相负极活性涂层B1和单相负极活性涂层B2，其中，单相负极活性涂层A1、单相负极活性涂层A2、单相负极活性涂层B1、单相负极活性涂层B2中分别所含有的负极活性材料仅为单相负极活性材料A1、单 相负极活性材料A2、单相负极活性材料B1、单相负极活性材料B2一种，且单相负极活性材料A1与单相负极活性材料A2、单相负极活性材料B1、单相负极活性材料B2中的至少一种互不相同。
在一实施例中，复合电芯包括两种共混负极片，共混负极片包括共混负极片A和共混负极片B，共混负极片A所设有的共混负极活性涂层A包括共混负极活性材料A1和共混负极活性材料A2；共混负极片B所设有的共混负极活性涂层B包括共混负极活性材料B1和共混负极活性材料B2，且共混负极活性材料A1与共混负极活性材料A2、共混负极活性材料B1、共混负极活性材料B2中的至少一种互不相同。
在一实施例中，复合电芯包括复合负极片和共混负极片，复合负极片所设有的单相负极活性涂层包括单相负极活性涂层A和单相负极活性涂层B，单相负极活性涂层A、B中分别所含有的负极活性材料仅为单相负极活性材料A、B；共混负极片所设有的共混负极活性涂层包括共混负极活性材料A和共混负极活性材料B；且复合负极活性材料A与复合负极活性材料B、共混负极活性材料A、共混负极活性材料B中的至少一种互不相同。
在一实施例中，负极片的集流体包括背对设置的两个侧面，每一侧面上均设有负极活性涂层，设置在任一侧面上的负极活性涂层的总容量与设置另一侧面上的负极活性涂层的总容量之比K2＝0.8～1.2，设置在同一侧面上的负极活性涂层的总容量按照式Ⅱ确定， 式Ⅱ中包括的Qn、Sn、Cm、Wm、i均与其各自在式Ⅰ中的含义相同，式Ⅱ中包括的h表示设置在同一侧面上的正极活性涂层的层数，h为大于等于1的整数。在上述负极片中，分别位于集流体不同侧的负极活性涂层之间满足特定的K2值范围，由此，负极片的集流体两侧基本达到容量平衡的状态，从而能使得负极片兼具优异的能量密度、倍率性能、循环性能。
在一实施例中，负极活性材料在包含其的负极活性涂层中的质量含量为90～98％。
在一实施例中，人造石墨的克容量为300～370mAh/g，天然石墨的克容量为340～372mAh/g，硬碳的克容量为200～1000mAh/g，软碳的克容量为100～800mAh/g，硅基材料的克容量为300～4200mAh/g。
在一实施例中，每层负极活性涂层的面密度为20～400g/m2。
根据本申请的第二个方面，提供一种电池，包括如上复合电芯。本申请提供的电池能够实现不同种负极活性材料同时充放电，从而充分利用不同负极活性材料的优势，获得兼具良好的能量密度、倍率性能以及循环性能的电池。
附图说明
图1为第一负极片的可行结构示意图；
图2为复合负极片的其中一种可行结构示意图；
图3为复合负极片的另一种可行结构示意图；
图4为对称型混合负极片的其中一种可行结构示意图；
图5为非对称型混合负极片的其中一种可行结构示意图；
图6为单组合电芯的结构示意图；
图7为复合电芯1～8的结构示意图；
图8为复合电芯9的结构示意图。
具体实施方式
实施例1
本实施例采用不同人造石墨、天然石墨、硬碳、软碳、硅基材料构造具有不同负极活性涂层组成的负极片，其中，以仅含有单种负极活性材料的负极片作为第一负极片，以含有至少两种负极活性材料的负极片作为第二负极片。
1.第一负极片
在本实施例所涉及的第一负极片中，其结构示意图如图1所示，分别在负极集流体的两个侧面上对称设置仅含有一种负极活性材料的负极活性涂层，分别标记为第一负极活性涂层1-1和第二负极活性涂层1-2。
1)人造石墨第一负极片
人造石墨第一负极片的制备：采用克容量为350mAh/g的人造石墨作为负极活性材料，将人造石墨、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料，然后在负极集流体的两个背对设置的侧面上分别涂布上述负极涂布浆料，干燥，从而在负极集流体的两个侧面形成对称设置的第一负极活性涂层1-1和第二负极活性涂层1-2，第一负极活性涂层1-1和第二负极活性涂层1-2中所含有的负极活性材料仅为人造石墨。将由此制得的人造石墨负极片标记为人造石墨单相负极片。在所制得的人造石墨第一负极片中，以所包括的负极活性涂层面密度为120g/m2的负极片标记为人造石墨第一负极片(1)、以所包括的负极活性涂层面密度为200g/m2的负极片标记为人 造石墨第一负极片(2)。
上述所制得的人造石墨第一负极片的结构示意图如图1所示。
2)天然石墨第一负极片
天然石墨第一负极片的制备：采用克容量为360mAh/g的天然石墨作为负极活性材料，将天然石墨、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料，然后在负极集流体的两个背对设置的侧面上分别涂布上述负极涂布浆料，干燥，从而在负极集流体的两个侧面形成对称设置的第一负极活性涂层1-1和第二负极活性涂层1-2，第一负极活性涂层1-1和第二负极活性涂层1-2中所含有的负极活性材料仅为天然石墨。将由此制得的天然石墨负极片标记为天然石墨第一负极片。在所制得天然石墨第一负极片中，以所包括的负极活性涂层面密度为120g/m2的负极片标记为天然石墨第一负极片(1)、以所包括的负极活性涂层面密度为50g/m2的负极片标记为天然石墨第一负极片(2)。
上述所制得的天然石墨第一负极片的结构示意图如图1所示。
3)硬碳第一负极片
硬碳第一负极片的制备：采用克容量为500mAh/g的硬碳作为负极活性材料，将硬碳、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料，然后在负极集流体的两个背对设置的侧面上分别涂布上述负极涂布浆料，干燥，从而在负极集流体的两个侧面形成对称设置的第一负极活性涂层1-1和第二负极活性涂层1-2，第一负极活性涂层1-1和第二负极活性涂层1-2中所含有的负极活性材料仅为硬碳。将由此制得的硬碳负极片标记为硬碳第一负极片。在所制得硬碳第一负极片中，以所包括的负极活性涂层面密度为90g/m2的负极片标记为硬碳第一负极片(1)、以所包括的负极活性涂层面密度为50g/m2的负极片标记为硬碳第一负极片(2)。
上述所制得的硬碳第一负极片的结构示意图如图1所示。
4)硅基材料第一负极片
硅基材料第一负极片的制备：采用克容量为1800mAh/g的硅基材料作为负极活性材料，将硅基材料、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料，然后在负极集流体的两个背对设置的侧面上分别涂布上述负极涂布浆料，干燥，从而在负极集流体的两个侧面形成对称设置的第一负极活性涂层A 1-1和负极活性涂层B 1-2，负极活性涂层A 1-1和负极活性涂层B 1-2中所含有的负极活性 材料仅为硅基材料。将由此制得的硅基材料负极片标记为硅基材料第一负极片。在所制得硅基材料第一负极片中，以所包括的负极活性涂层面密度为120g/m2的负极片标记为硅基材料第一负极片(1)、以所包括的负极活性涂层面密度为50g/m2的负极片标记为硅基材料第一负极片(2)。
上述所制得硅基材料第一负极片的结构示意图如图1所示。
2.第二负极片
(1)复合负极片
复合负极片的其中一种可行的结构形式如图2所示，分别在负极集流体的两个侧面上对称地设置相互复合的单相负极活性涂层A2-1和单相负极活性涂层B 2-2，单相负极活性涂层A2-1中所含有的负极活性材料仅为负极活性材料A一种，单相负极活性涂层B 2-2中所含有的负极活性材料仅为负极活性材料B一种，且负极活性材料A与负极活性材料B互不相同。复合负极片的另一种可行的结构形式如图3所示，在负极集流体的其中一个侧面上设置相互复合的单相负极活性涂层A3-1和单相负极活性涂层B 3-2，在负极集流体的另一个侧面上设置单相负极活性涂层C 3-3，单相负极活性涂层A3-1中所含有的负极活性材料仅为负极活性材料A一种，单相负极活性涂层B 3-2中所含有的负极活性材料仅为负极活性材料B一种，单相负极活性涂层C 3-3中所含有的负极活性材料仅为负极活性材料C一种，且第一负极活性材料C与第一负极活性材料A、负极活性材料B中的至少一种互不相同。
1)对称型复合负极片
采用克容量为350mAh/g的人造石墨作为负极活性材料，将人造石墨、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料A；采用克容量为500mAh/g的硬碳作为负极活性材料，将硬碳、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料B。在负极集流体的其中一个侧面上涂布上述负极涂布浆料A，干燥，形成单相负极活性涂层A2-1，接着在该单相负极活性涂层A2-1的表面涂布负极涂布浆料B，干燥，形成单相负极活性涂层B 2-2，然后在负极集流体的另一个侧面重复上述操作，以在负极集流体的两个侧面上对称地设置相互复合的单相负极活性涂层A2-1(采用负极活性材料为人造石墨)和单相负极活性涂层B 2-2(采用的负极活性材料为硬碳)，将由此制得的对称型负极片标记为人造石墨-硬碳复合负极片。在所制得人造石墨-硬碳复合负极片中，以所包括的单相负极活性涂层A2-1的面密度为80g/m2，单相负极活性涂层B 2-2的面密度为40g/m2的对称型 复合负极片标记为人造石墨-硬碳复合负极片(1)；以所包括的单相负极活性涂层A2-1的面密度为160g/m2，单相负极活性涂层B 2-2的面密度为80g/m2，将由此制得的对称型复合负极片标记为人造石墨-硬碳复合负极片(2)。
上述所制得人造石墨-硬碳复合负极片的结构示意图如图2所示。
(2)共混负极片
本实施例所涉及的第二负极片指的是所含有的所有负极活性涂层中的至少一层由至少两种不同的负极活性材料共混而成的负极片。第二负极片的其中一种可行的结构形式如图4所示，在负极集流体的两侧对称设有共混负极活性涂层4-1，共混负极活性涂层4-1中含有两种不同种类的负极活性材料(第一负极活性材料和第二负极活性材料)。第二负极片的另一种可行的结构形式如图5所示，在负极集流体的一侧设有共混负极活性涂层5-1，共混负极活性涂层5-1中含有两种不同种类的负极活性材料(第一负极活性材料和第二负极活性材料)，在负极集流体的另一侧设有仅采用一种负极活性材料的单相负极活性涂层5-2。
1)对称型共混负极片
采用克容量为350mAh/g的人造石墨以及克容量为1800mAh/g的硅基材料作为负极活性材料。将上述人造石墨和硅基材料按照9:1的质量比混合得到共混负极活性材料，然后将由此得到的共混负极活性材料、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料。然后在负极集流体的两个背对设置的侧面上分别涂布上述负极涂布浆料，干燥，从而在负极集流体的两个侧面形成对称设置的两层共混负极活性涂层4-1，每层共混负极活性涂层4-1中所含有的负极活性材料为共混的人造石墨和硅基材料，每层共混负极活性涂层4-1的面密度为90g/m2，将由此制得的共混负极片标记为对称型共混负极片(1)；每层共混负极活性涂层4-1的面密度为110g/m2，将由此制得的共混负极片标记为对称型共混负极片(2)。
上述所制得对称型共混负极片的结构示意图如图4所示。
2)非对称型第二负极片
采用克容量为350mAh/g的人造石墨以及克容量为1800mAh/g的硅基材料作为负极活性材料。将上述人造石墨和硅基材料按照9:1的质量比混合得到共混负极活性材料，然后将由此得到的共混负极活性材料、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料A。将上述人造石墨、导电剂(SP)、粘结剂羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)按96:1:1:2的质量比混合均匀制成负极涂布浆料 B。在负极集流体的其中一个侧面上涂布上述负极涂布浆料A，干燥，形成共混负极活性涂层5-1，然后在负极集流体的另一个侧面涂布负极涂布浆料B，干燥，形成第一负极活性涂层5-2，共混负极活性涂层5-1的面密度为110g/m2，第一负极活性涂层5-2的面密度为120g/m2。将由此制得的共混负极片标记为非对称型共混负极片。在所制得非对称型共混负极片中，以所包括的共混负极活性涂层5-1的面密度为110g/m2，第一负极活性涂层5-2的面密度为120g/m2的非对称型共混负极片标记为非对称型共混负极片。
上述所制得非对称型共混负极片的结构示意图如图5所示。
依据式Ⅰ计算本实施例所制得的上述负极片的总容量；在式Ⅰ中，Qn表示负极片所包括的任一层负极活性涂层的面积，Sn表示负极片所包括的任一层负极活性涂层的面密度，在该层负极活性涂层中，Cm表示任一种负极活性材料的克容量，Wm表示该种负极活性材料在该层负极活性涂层中的质量百分比，i表示每层负极活性涂层所包括的负极活性材料的类别数量，i为大于等于1的整数，k表示每片负极片所包括的负极活性涂层的层数，k为大于等于1的整数。在表1中所涉及的K1为负极A片的总容量与负极片B的总容量之比。在式Ⅰ中，表示的是负极片中某一层负极活性涂层的容量水平，在分别对每一层负极活性涂层的容量进行计算后，将计算结果进行求和，即按照计算，最终得到整片负极片的容量水平。
对于第一负极片，总容量的计算方式具体如下：以其所采用的负极活性材料在第一负极活性涂层A 1-1中的质量含量为W1，以该负极活性材料的克容量为C1，第一负极活性涂层A 1-1的面密度为S1，则第一负极活性涂层A 1-1的容量为Q1×S1×W1×C1，相应的，第一负极活性涂层B 1-2的容量也按照上述方式进行计算，由于第一负极活性涂层A 1-1和第一负极活性涂层B 1-2对称设置，所以该第一负极片的总容量为2×Q1×S1×W1×C1。
对于属于第二负极片的对称型复合负极片，其总容量的计算方式具体如下：在负极集流体的任一侧，以单相负极活性涂层A2-1中的负极活性材料质量含量为W1，以该负极活性材料的克容量为C1，单相负极活性涂层A2-1的面密度为S1，则单相负极活性涂层A2-1的容量为Q1×S1×W1×C1，以单相负极活性涂层B 2-2中的负极活性材料质量含量为W2，以该负极活性材料的克容量为C2，单相负极活性涂层B 2-2的面密度为S2，则单相负极活性涂层B 2-2的容量为Q2×S2×W2×C2，相应地，该侧的负极活性涂层容量为(Q1×S1×W1×C1+Q2×S2×W2×C2)，另外，位于负极集流体另一侧的负极活性涂层的容量也按照 上述方式进行计算，由于在负极集流体的另一侧设置的负极活性涂层分别与单相负极活性涂层A2-1、单相负极活性涂层B 2-2互为对称，所以该对称型复合负极片的总容量为2×(Q1×S1×W1×C1+Q2×S2×W2×C2)。
对于属于第二负极片的对称型共混负极片，其总容量的计算方式具体如下：在其中一层共混负极活性涂层4-1中，其中一种负极活性材料A的质量含量为W1，以该负极活性材料的克容量为C1，另一种负极活性材料B的质量含量为W2，以该负极活性材料的克容量为C2，该层共混负极活性涂层4-1的面密度为S1，则该层共混负极活性涂层4-1的容量为Q1×S1×(W1×C1+W2×C2)，相应的，另一层共混负极活性涂层4-1的容量也按照上述方式进行计算，由于两层共混负极活性涂层4-1对称设置，所以该第二负极片的总容量为2×(Q1×S1×(W1×C1+W2×C2))。
对于属于第二负极片的非对称型共混负极片，其总容量的计算方式具体如下：在采用含有多种负极活性材料的共混负极活性涂层5-1中，其中一种负极活性材料A的质量含量为W1，以该负极活性材料的克容量为C1，另一种负极活性材料B的质量含量为W2，以该负极活性材料的克容量为C2，共混负极活性涂层5-1的面密度为S1，则共混负极活性涂层5-1的容量为Q1×S1×(W1×C1+W2×C2)，在仅含有一种负极活性材料的第一活性涂层5-2中，负极活性材料A的质量含量为W3，以第一负极活性材料的克容量为C3，第一负极活性涂层5-2的面密度为S2，第一负极活性涂层5-2的容量为S2×W3×C3；该非对称型共混负极片的总容量为(Q1×S1×(W1×C1+W2×C2)+Q2×S2×W3×C3)。
表1.各负极片的总容量计算

实施例2
本实施例采用实施例1所制得的不同负极片与正极片、隔膜搭配制备不同的电池电芯。
本实施例采用的第一正极片按照如下方式制备：采用磷酸铁锂作为正极活性材料，将磷酸铁锂、粘结剂PVDF、导电剂乙炔黑按照90：5：5的质量比混合，然后加入溶剂N-甲基吡咯烷酮(NMP)，搅拌均匀，制成正极涂布浆料；然后在正极集流体的两个背对设置的侧面上分别涂布上述正极涂布浆料，干燥，从而在正极集流体的两个侧面形成对称设置的两层正极活性涂层。
本实施例采用的第二正极片按照如下方式制备：采用三元材料作为正极活性材料，将三元材料、粘结剂PVDF、导电剂乙炔黑按照90：5：5的质量比混合，然后加入溶剂N-甲基吡咯烷酮(NMP)，搅拌均匀，制成正极涂布浆料；然后在正极集流体的两个背对设置的侧面上分别涂布上述正极涂布浆料，干燥，从而在正极集流体的两个侧面形成对称设置的两层正极活性涂层。
本实施例所采用的隔膜为聚乙烯膜。
本实施例所采用的电解液按照如下方式制备：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比1：1：1进行混合得到有机溶剂，然后将充分干燥的锂盐LiPF6溶解于有机溶剂中，配制成浓度为1mol/L的电解液。
应用实施例1所制得的负极片按照不同的搭配方式与本实施例所制得上述正极片构建电池电芯，并对采用不同负极片组合的电芯进行编号，具体分组情况如表2、表3所示，其中，表2中所展示的电芯为仅采用了一种负极片的单组合电芯，表3所展示的电芯为采用了两种负极片的复合电芯。利用表1展示的数据进行计算，负极片进行搭配的复合电芯的负极片容量分布情况如表4所示，表4中，K1为复合电芯中负极片A的总容量与负极片B的总容量之比。
采用单组合电芯1～6的电池按照如下方式制备：采用50片负极片6-1、49片第一正极片6-2，使负极片6-1、第一正极片6-2依次间隔设置，各极片之间均采用隔膜6-3进行分隔，通过叠片或者卷绕的工艺制得单组合电芯，单组合电芯的结构示意图如图6所示；然后将单组合电芯置于电池壳体中，接着对电池壳体进行焊接极耳、烘烤等处理，待水分含量检测合格后向电池壳体中注入适量电解液，封装，通过老化，化成，抽气封装，制备电池。
采用单组合电芯7～8的电池按照如下方式制备：采用50片负极片6-1、49片第二正极片6-2，使负极片6-1、第二正极片6-2依次间隔设置，各极片之间均采用隔膜6-3进行分隔，通过叠片或者卷绕的工艺制得单组合电芯，单组合电芯的结构示意图如图6所示；然后将单 组合电芯置于电池壳体中，接着对电池壳体进行焊接极耳、烘烤等处理，待水分含量检测合格后向电池壳体中注入适量电解液，封装，通过老化，化成，抽气封装，制备电池。
采用复合电芯1～8的电池按照如下方式制备：采用101片负极片(其中，51片负极片A7-1、50片负极片B 7-2)、100片第一正极片7-3，按负极片A7-1、第一正极片7-3、负极片B 7-2的排列顺序使负极片、正极片依次间隔设置，各极片之间均采用隔膜7-4进行分隔，复合电芯的结构示意图如图7所示；然后将复合电芯置于电池壳体中，接着对电池壳体进行焊接极耳、烘烤等处理，待水分含量检测合格后向电池壳体中注入适量电解液，封装，通过老化，化成，抽气封装，制备电池。
采用复合电芯9的电池按照如下方式制备：采用101片负极片(其中，51片负极片A 8-1、50片负极片B 8-2)、100片正极片(其中，50片第一正极片8-3、50片第二正极片8-5)，其中，按一片负极片A 8-1、一片第一正极片8-3定义为第一电芯组合单元，将一片第二正极片8-5、一片负极片B 8-2定义为第二电芯组合单元，使50个第一电芯组合单元依次排列，使50个第二电芯组合单元依次排列，并按50个第一电芯组合单元、负极片A、50个第二电芯组合单元的排列顺序使负极片、正极片依次间隔设置。各极片之间均采用隔膜8-4进行分隔，复合电芯的结构示意图如图8所示；然后将复合电芯置于电池壳体中，接着对电池壳体进行焊接极耳、烘烤等处理，待水分含量检测合格后向电池壳体中注入适量电解液，封装，通过老化，化成，抽气封装，制备电池。
表2.单组合电芯对应所采用的负极片
表3.复合电芯所包括的负极片组合情况
表4.复合电芯中负极片组合的容量分布情况

测试例
1.参试对象
本测试例以实施例2所制得的电池作为参试对象，进行相关性能测试。
2.测试内容
(1)能量密度
将参试的电池以0.33C恒流恒压充电至4.25V，0.02C截止，然后0.33C放电至2.8V，记录容量，平均电压和电芯质量，按照以下公式计算电池的能量密度：能量密度＝容量*平均电压/电池质量。
(2)直流阻抗
将参试的电池以0.33C恒流恒压充电至4.25V，0.02C截止，然后0.33C放电90min，搁置10min，记录搁置末端电压V1；然后以2C(电流I)放电10s，记录放电末端电压V2，按照以下公式计算钠离子电池的直流阻抗：直流阻抗＝|V1-V2|/I。
(3)循环性能
将参试的电池放在45℃恒温箱中，以1C恒流恒压充电，0.02C截止，然后以1C放电，循环至80％SOC，记录循环圈数。
3.测试结果
表5.本测试例的电池性能测试结果

实施例2所制得的电池的相关性能测试结果如表5所示。相较于单组合电芯1～8(仅含有一种负极片)而言，复合电芯1～9所制得的电池中含有两种负极片，测试结果显示，复合电芯1～9所制得的电池的直流阻抗较低，且能量密度和循环性能较好，这主要是因为在复合电芯中将高倍率长循环的极片和高安全高能量密度的极片进行混搭，实现两种体系的搭配，得到两种不同的负极片共存的电芯，通过调整高倍率长循环的数量或者高安全高能量密度的数量以使电芯实现优异的能量密度、循环性能和安全性能的结合，所制得的电池同时兼具优异的能量密度、循环性能和安全性能的特性。由此说明，本申请提供的复合电芯能够充分发挥不同种负极活性材料的协同优势，使得复合电芯的能量密度、倍率性能、循环性能相对于采用单一负极活性材料的电芯而言，得到整体的提高。
将复合电芯1、2，复合电芯3、4，复合电芯5、6、复合电芯7、8分别进行比对。与复合电芯1相比，在制备电池的其他条件相同的情况下，复合电芯2中负极片A的总容量与负极片B的总容量之比K1没有满足0.8～1.2，测试结果显示，复合电芯1所制得的电池的直流阻抗更低，且能量密度和循环性能更好，这主要是因为复合电芯1不同负极片之间满足特定的K1值范围，由此，不同的负极片之间基本达到容量平衡的状态。复合电芯3、5、7的测试结果同上。由此说明，本申请提供的复合电芯通过使不同负极片之间的总容量之比满足K1值范围，不同的负极片之间基本达到容量平衡的状态，进而使不同种负极活性材料充分发挥其协同优势，进而提高了复合电芯的综合性能。
相较于复合电芯8(仅含有一种正极片)而言，复合电芯9所制得的电池中含有两种不同正极片，测试结果显示，复合电芯9所制得的电池的直流阻抗更低，且能量密度和循环性 能更好，这主要是因为复合电芯9包括了两种正极片，且将第二正极片(所采用的正极活性材料为三元正极材料)与包括硅基材料的共混负极片相邻搭配，进一步提高了电池的综合性能。由此说明，本申请提供的复合电芯通过集成不同的负极活性材料和正极活性材料，使各种正极片和负极片发挥协同优势，进一步提高了复合电芯的能量密度、倍率性能、循环性能。

Claims (17)

  1. 一种复合电芯，所述复合电芯包括至少两种负极片，所述复合电芯所含有的负极活性材料包括人造石墨、天然石墨、硬碳、软碳、硅基材料中的至少两种，所述负极活性材料用于构造所述负极片的负极活性涂层；
    所述复合电芯包括第一负极片、第二负极片中的至少一种，所述第一负极片仅包括一种所述负极活性材料，所述第二负极片包括至少两种不同种类的所述负极活性材料；
    其中，所述第二负极片包括复合负极片、共混负极片中的至少一种；所述复合负极片在负极集流体的一侧至少设有两层单相负极活性涂层，所述单相负极活性涂层中仅含有一种负极活性材料；所述共混负极片设有的负极活性涂层中至少一层为共混负极活性涂层，所述共混负极活性涂层中至少包括两种互不相同的负极活性材料。
  2. 如权利要求1所述复合电芯，其中，在所述复合电芯中，任一片所述负极片的总容量与其余任一片所述负极片的总容量之比K1＝0.8～1.2，每片所述负极片的总容量以式Ⅰ表示：
    在所述式Ⅰ中，Qn表示所述负极片所包括的任一层所述负极活性涂层的面积，Sn表示所述负极片所包括的任一层所述负极活性涂层的面密度，在该层所述负极活性涂层中，Cm表示任一种所述负极活性材料的克容量，Wm表示该种所述负极活性材料在该层所述负极活性涂层中的质量百分比，i表示每层所述负极活性涂层所包括的所述负极活性材料的类别数量，i为大于等于1的整数，k表示每片所述负极片所包括的所述负极活性涂层的层数，k为大于等于1的整数；
  3. 如权利要求1所述复合电芯，其中，所述复合电芯包括两种所述第一负极片，所述第一负极片包括第一负极片A和第一负极片B，所述第一负极片A所含有的负极活性材料仅为第一负极活性材料A一种，第一负极片B中所含有的负极活性材料仅为第一负极活性材料B一种，且第一负极活性材料A与第一负极活性材料B的种类互不相同。
  4. 如权利要求3所述复合电芯，其中，所述第一负极片A所设有的所述负极活性涂层为第一负极活性涂层A，所述第一负极片B所设有的所述负极活性涂层为第一负极活性涂层B；
    在所述第一负极片A的负极集流体的两侧对称设有所述第一负极活性涂层A，在所述第一负极片B的负极集流体的两侧对称设有所述第一负极活性涂层B。
  5. 如权利要求1所述复合电芯，其中，所述复合电芯包括所述第一负极片和所述复合负极片，所述第一负极片所含有的负极活性材料仅为第一负极活性材料一种，所述复合负极片所设有的单相负极活性涂层包括单相负极活性涂层A和单相负极活性涂层B，其中，所述单相负极活性涂层A中所含有的负极活性材料仅为单相负极活性材料A一种，所述单相负极活性涂层B中所含有的负极活性材料仅为单相负极活性材料B一种，且单相负极活性材料B与第一负极活性材料、单相负极活性材料A中的至少一种互不相同。
  6. 如权利要求5所述复合电芯，其中，在所述复合负极片的集流体同一侧，沿远离集流体表面的方向上，所述单相负极活性涂层A和所述单相负极活性涂层B依次设置。
  7. 如权利要求5所述复合电芯，其中，所述第一负极片所设有的所述负极活性涂层为第一负极活性涂层；在所述复合负极片的负极集流体的两侧对称设有所述单相负极活性涂层，或，在负极集流体的一侧设有所述单相负极活性涂层，在负极集流体的另一侧设有所述第一负极活性涂层。
  8. 如权利要求1所述复合电芯，其中，所述复合电芯包括第一负极片和共混负极片，所述第一负极片所含有的负极活性材料仅为第一负极活性材料一种，所述共混负极片所设有的共混负极活性涂层包括共混负极活性材料A和共混负极活性材料B，且共混负极活性材料B与第一负极活性材料、共混负极活性材料A中的至少一种互不相同。
  9. 如权利要求8所述复合电芯，其中，所述第一负极片所设有的所述负极活性涂层为第一负极活性涂层，在所述共混负极片的负极集流体的两侧对称设有所述共混负极活性涂层，或，在负极集流体的一侧设有所述共混负极活性涂层，在负极集流体的另一侧设有所述第一负极活性涂层。
  10. 如权利要求1所述复合电芯，其中，所述复合电芯包括两种所述复合负极片，所述复合负极片包括复合负极片A和复合负极片B，所述复合负极片A所设有的单相负极活性涂层包括单相负极活性涂层A1和单相负极活性涂层A2；所述复合负极片B所设有的单相 负极活性涂层包括单相负极活性涂层B1和单相负极活性涂层B2，其中，所述单相负极活性涂层A1、所述单相负极活性涂层A2、所述单相负极活性涂层B1、所述单相负极活性涂层B2中分别所含有的负极活性材料仅为单相负极活性材料A1、单相负极活性材料A2、单相负极活性材料B1、单相负极活性材料B2一种，且单相负极活性材料A1与单相负极活性材料A2、单相负极活性材料B1、单相负极活性材料B2中的至少一种互不相同。
  11. 如权利要求1所述复合电芯，其中，所述复合电芯包括两种所述共混负极片，所述共混负极片包括共混负极片A和共混负极片B，所述共混负极片A所设有的共混负极活性涂层A包括共混负极活性材料A1和共混负极活性材料A2；所述共混负极片B所设有的共混负极活性涂层B包括共混负极活性材料B1和共混负极活性材料B2，且共混负极活性材料A1与共混负极活性材料A2、共混负极活性材料B1、共混负极活性材料B2中的至少一种互不相同。
  12. 如权利要求1所述复合电芯，其中，所述复合电芯包括所述复合负极片和所述共混负极片，所述复合负极片所设有的单相负极活性涂层包括单相负极活性涂层A和单相负极活性涂层B，所述单相负极活性涂层A、B中分别所含有的负极活性材料仅为单相负极活性材料A、B；所述共混负极片所设有的共混负极活性涂层包括共混负极活性材料A和共混负极活性材料B；且复合负极活性材料A与复合负极活性材料B、共混负极活性材料A、共混负极活性材料B中的至少一种互不相同。
  13. 如权利要求1～12任一项所述复合电芯，其中，所述负极片的集流体包括背对设置的两个侧面，每一所述侧面上均设有所述负极活性涂层，设置在任一所述侧面上的所述负极活性涂层的总容量与设置另一所述侧面上的所述负极活性涂层的总容量之比K2＝0.8～1.2，设置在同一所述侧面上的所述负极活性涂层的总容量按照式Ⅱ确定， 所述式Ⅱ中包括的Qn、Sn、Cm、Wm、i均与其各自在所述式Ⅰ中的含义相同，所述式Ⅱ中包括的h表示设置在同一侧面上的所述正极活性涂层的层数，h为大于等于1的整数。
  14. 如权利要求1～12任一项所述复合电芯，其中，所述负极活性材料在包含其的所述负 极活性涂层中的质量含量为90～98％。
  15. 如权利要求1～12任一项所述复合电芯，其中，所述人造石墨的克容量为300～370mAh/g，所述天然石墨的克容量为340～372mAh/g，所述硬碳的克容量为200～1000mAh/g，所述软碳的克容量为100～800mAh/g，所述硅基材料的克容量为300～4200mAh/g。
  16. 如权利要求1～12任一项所述复合电芯，其中，每层所述负极活性涂层的面密度为20～400g/m2。
  17. 一种电池，包括如权利要求1～16任一项所述复合电芯。
PCT/CN2023/109021 2023-05-23 2023-07-25 一种复合电芯及应用其的电池 Ceased WO2024239443A1 (zh)

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