WO2023236152A1 - 二次电池、含有该二次电池的电池模块、电池包及用电装置 - Google Patents

二次电池、含有该二次电池的电池模块、电池包及用电装置 Download PDF

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WO2023236152A1
WO2023236152A1 PCT/CN2022/097944 CN2022097944W WO2023236152A1 WO 2023236152 A1 WO2023236152 A1 WO 2023236152A1 CN 2022097944 W CN2022097944 W CN 2022097944W WO 2023236152 A1 WO2023236152 A1 WO 2023236152A1
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negative electrode
film layer
electrode film
lithium
secondary battery
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PCT/CN2022/097944
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English (en)
French (fr)
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董晓斌
王家政
严青伟
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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 EP22927593.8A priority Critical patent/EP4329014A1/en
Priority to CN202280060933.2A priority patent/CN118104013A/zh
Priority to PCT/CN2022/097944 priority patent/WO2023236152A1/zh
Publication of WO2023236152A1 publication Critical patent/WO2023236152A1/zh
Priority to US18/424,867 priority patent/US20240170641A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery, a battery module, a battery pack and an electrical device containing the secondary battery.
  • Secondary batteries rely on active ions to reciprocate and deintercalate between the positive and negative electrodes for charging and discharging. They have outstanding features such as high energy density, long cycle life, no pollution, and no memory effect. Therefore, as a clean energy source, secondary batteries have gradually spread from electronic products to large-scale devices such as electric vehicles to adapt to the sustainable development strategy of the environment and energy. As a result, higher requirements have been placed on the energy density of secondary batteries.
  • the purpose of this application is to provide a secondary battery, a battery module, a battery pack and a power device containing the secondary battery, so that the secondary battery has high energy density, good cycle performance and storage performance.
  • the first aspect of the present application provides a secondary battery, including a positive electrode plate with a positive electrode film layer disposed thereon; a separation film; and a negative electrode plate including a first negative electrode film layer, the first negative electrode
  • the film layer is arranged opposite to the positive electrode film layer across the isolation film, and a second negative electrode film layer, the second negative electrode film layer includes a negative electrode film layer that is not arranged opposite to the positive electrode film layer, the second negative electrode film layer is disposed opposite to the positive electrode film layer.
  • the negative electrode film layer includes a central area and a peripheral area surrounding the central area, wherein at least a part of the peripheral area of the second negative electrode film layer stores lithium for supplementing lithium to the first negative electrode film layer. source.
  • a lithium source for supplementing lithium to the first negative electrode film layer is stored in the outer peripheral area of the second negative electrode film layer of the negative electrode sheet, and the area where the lithium source is stored can have a low potential. Therefore, when the lithium ion secondary battery is charged, after the Li + detached from the positive electrode is embedded in the first negative electrode film layer, although the potential of the first negative electrode film layer decreases, the first negative electrode film layer and the second negative electrode film layer The potential difference can be maintained small, thereby preventing Li + from diffusing and intercalating into the second negative electrode film layer. During the discharge process of the lithium-ion secondary battery, the potential of the first negative electrode film layer will gradually increase.
  • the lithium source When the potential of the first negative electrode film layer is much higher than the potential of the second negative electrode film layer, the lithium source will be in the first negative electrode film layer. Li + is formed driven by the potential difference between the film layer and the second negative electrode film layer, and diffuses toward the first negative electrode film layer at a slow speed. As a result, the active lithium lost during the charge and discharge cycles of the lithium-ion secondary battery can be replenished, thereby significantly improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery. Furthermore, the lithium source of the present application is stored in the peripheral area of the second negative electrode film layer. Compared with the central area, the distance between the outer peripheral area and the first negative electrode film layer is shorter. When the lithium source forms Li + driven by the potential difference, Li + can have a shorter diffusion path, thereby avoiding the loss of Li + during the diffusion process, thereby significantly improving the efficiency of lithium replenishment and the utilization rate of the lithium source.
  • the equivalent circular area diameter R of the second negative electrode film layer and the equivalent circular area diameter R 1 of the outer peripheral region satisfy: 0.257R ⁇ R 1 ⁇ 0.9434R.
  • the equivalent circular area diameter of the second negative electrode film layer and the equivalent circular area diameter of the outer peripheral region satisfy the above conditions, which can allow the lithium source of the present application to have appropriate storage space, thereby being able to supplement an appropriate amount of activity to the secondary battery through the lithium source. lithium ion.
  • the equivalent circular area diameter of the second negative electrode film layer and the equivalent circular area diameter of the outer peripheral region meet the above conditions, which enables the Li + formed by the lithium source driven by the potential difference to have a suitable diffusion path, thereby improving lithium replenishment. efficiency and utilization of lithium sources. As a result, the first Coulombic efficiency, cycle performance and storage performance of the secondary battery can be further improved.
  • the peripheral area has a first part and a second part surrounding the first part, and the equivalent circular area diameter R 2 of the second part satisfies: 0 ⁇ R 2 ⁇ R 1 , which can be Optionally, 0 ⁇ R 2 ⁇ 0.5R 1 , more optionally, 0 ⁇ R 2 ⁇ 0.1R 1 , wherein the lithium source is stored in the first part.
  • R 2 equivalent circular area diameter
  • the lithium source located at the edge of the second negative electrode film layer may separate from the negative electrode piece, thereby causing the loss of the lithium source.
  • Dividing the peripheral area into a first part and a second part located at the edge of the second negative electrode film layer allows the lithium source to be stored in the first part, which enables the lithium source to stably exist in the second negative electrode film layer, thereby reducing the risk of lithium source loss. .
  • the efficiency of lithium replenishment of the secondary battery can be improved.
  • the first part is annular
  • the minimum distance d 1 between the outer contour of the first part and the edge of the second negative electrode film layer, and the width d 0 of the second negative electrode film layer satisfy : 0 ⁇ d 1 ⁇ d 0 /6.
  • the minimum distance d 1 between the outer contour of the first part and the edge of the second negative electrode film layer is within the above-mentioned appropriate range, which can effectively reduce the loss of lithium source while ensuring that the Li + released from the lithium source has a diffusion path of appropriate length. risks of.
  • the efficiency of lithium replenishment of the secondary battery can be improved, thereby improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery.
  • d 3 ⁇ d 2 ⁇ d 0 /6, where d 2 represents the minimum distance between the outer contour line and the side in the length direction of the second negative electrode film layer, and d 3 represents The minimum distance between the outer contour line and the side in the width direction of the second negative electrode film layer.
  • d 2 represents the minimum distance between the outer contour line and the side in the length direction of the second negative electrode film layer
  • d 3 represents The minimum distance between the outer contour line and the side in the width direction of the second negative electrode film layer.
  • the first part is a hollow rectangle, and the first part satisfies: 0 ⁇ d 4 ⁇ d 0 /3, and d 4 indicates that the first part is along the width direction of the second negative electrode film layer.
  • the first part has a suitable width, so that the first part has a suitable area, so that a suitable amount of lithium source can be stored.
  • the first part has a suitable width, which in turn allows the second part and the central area to have a suitable area.
  • the lithium source when the lithium source is stored in the first part, it can have an appropriate distance from the center of the second negative electrode film layer and/or the edge of the second negative electrode film layer. Therefore, the second negative electrode film layer of the present application can store appropriate active lithium. Not only is the active lithium not easy to fall off from the second negative electrode film layer, but when the secondary battery needs to replenish lithium ions, the active lithium can also pass through relatively The short path diffuses and embeds the first negative electrode film layer. Therefore, the secondary battery of the present application can have high first Coulombic efficiency and good cycle performance and storage performance.
  • the secondary battery satisfies: 1mm ⁇ d2 ⁇ 5mm .
  • l 1 represents the length of the outer contour.
  • (d 0 -10mm) ⁇ l 2 ⁇ (d 0 -2mm), l 2 represents the width of the outer contour line.
  • the secondary battery meets at least one of the above conditions, it is beneficial for the second negative electrode film layer to provide enough space for storing the lithium source, and the lithium source can be appropriately distributed in the second negative electrode film layer.
  • the lithium source is not only difficult to fall off from the second negative electrode film layer, but when the secondary battery needs to replenish lithium ions, the Li + provided by the lithium source can also diffuse through a shorter path and be embedded in the first negative electrode film layer. Therefore, the secondary battery of the present application can have high first Coulombic efficiency and good cycle performance and storage performance.
  • the lithium source is distributed annularly in the first part.
  • the second negative electrode film layer can have a suitable potential.
  • Li + in the first negative electrode film layer is less likely to be embedded in the second negative electrode film layer, thereby further reducing the loss of active lithium. Therefore, the secondary battery of the present application can have high first Coulombic efficiency, good cycle performance and storage performance.
  • the area S 1 of the second negative electrode film layer storing the lithium source and the area S 2 of the peripheral area satisfy: 10% ⁇ S 1 /S 2 ⁇ 100%, optionally 80% ⁇ S 1 /S 2 ⁇ 100%, more optionally 90% ⁇ S 1 /S 2 ⁇ 100%.
  • the ratio of S 1 to S 2 is within an appropriate range, so that the amount of lithium source stored in the second negative electrode film layer is appropriate.
  • the appropriate amount of lithium source can, on the one hand, make the second negative electrode film layer have a suitable potential, thereby reducing the Li + in the first negative electrode film layer to escape and embed in the second negative electrode film layer; on the other hand, it can provide enough active lithium In the case of ions, avoid excess lithium source. This can reduce the loss of Li + during the cycle of the secondary battery, improve the efficiency of lithium replenishment, and control the cost of lithium replenishment. Therefore, the secondary battery of the present application can have high first Coulombic efficiency, good cycle performance and storage performance, and low cost.
  • the lithium source includes at least one of lithium metal, lithium alloy, a composite of lithium metal and anode active material, or a composite of aluminum alloy and anode active material.
  • the Lithium alloys include at least one of silicon-lithium alloys, aluminum-lithium alloys, magnesium-lithium alloys, and tin-lithium alloys. Whether it is metallic lithium foil, lithium powder, silicon-lithium alloy, aluminum-lithium alloy, magnesium-lithium alloy, tin-lithium alloy and other forms of lithium alloy, they can be used as a lithium supplement layer and interact with the active material in the second negative electrode film layer.
  • the lithium source of the present application is formed, thereby realizing lithium replenishment for secondary batteries.
  • the secondary battery satisfies: 20% C 0 ⁇ C Li ⁇ 120% C 0 , optionally, 90% C 0 ⁇ C Li ⁇ 120% C 0 , where C 0 represents The active material capacity per unit area of the second negative electrode film layer, C Li , represents the capacity per unit area of the lithium source.
  • C 0 and C Li meet the above conditions, the speed of Li + removal from the lithium source can be within a more appropriate range, thus taking into account the lithium replenishment efficiency and the safety performance of the secondary battery.
  • the secondary battery has a winding structure
  • the second negative electrode film layer includes a starting area and an ending area along the winding direction
  • the secondary battery satisfies: C A ⁇ C B
  • C A represents the capacity of the lithium source located in the starting area
  • CB represents the capacity of the lithium source located in the ending area.
  • the second negative electrode film layer located in the starting area has a better ability to retain the electrolyte, which is more conducive to the diffusion of Li + desorbed from the lithium source.
  • the lithium source capacity in the starting area is higher, which is beneficial to improving the lithium replenishment efficiency and the utilization rate of the lithium source.
  • the minimum distance d 7 between the lithium source and the first negative electrode film layer satisfies: 0 ⁇ d 7 ⁇ 10 mm.
  • the minimum distance between the lithium source and the first negative electrode film layer is within the above-mentioned appropriate range, which allows the Li + released from the lithium source to have a shorter diffusion path, thereby improving the lithium replenishment efficiency and the utilization rate of the lithium source.
  • the surface of the central region is covered with a barrier layer, and the barrier layer includes a barrier film and/or a barrier coating.
  • the barrier film is selected from at least one of cast polypropylene film, uniaxially stretched polypropylene film, biaxially stretched polypropylene film, polyethylene film, polyester fiber film, and polyvinyl chloride film.
  • the barrier coating includes polyvinylidene fluoride, polytetrafluoroethylene, polyphenylpropamide, polyamide, polyimide, polymethyl methacrylate, polyurethane, polystyrene, polyacrylic acid, polyacrylamide, poly At least one of acrylonitrile or copolymers of the above substances.
  • the surface of the central area is covered with a barrier layer, which can reduce the risk of the electrolyte infiltrating the central area.
  • the active Li + in the secondary battery can be reduced to be embedded in the negative electrode film layer in the central area, thereby further improving the lithium replenishment efficiency and the utilization rate of the lithium source, thereby improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery.
  • the barrier layer has a thickness of 6 ⁇ m to 40 ⁇ m, and more optionally, the barrier layer has a thickness of 10 ⁇ m to 20 ⁇ m.
  • the thickness of the barrier layer is within a suitable range, it can not only have good mechanical strength and thus be less likely to be damaged, but also enable the thickness of the negative electrode piece to be within a smaller range, thereby facilitating the processing of the negative electrode piece.
  • a second aspect of the present application provides a battery module, which includes the secondary battery of the present application.
  • a third aspect of the present application provides a battery pack, which includes the battery module of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack of the present application.
  • the electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an electrode assembly included in a secondary battery according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of an electrode assembly included in the secondary battery in an embodiment of the secondary battery of the present application.
  • FIG. 3 is a schematic diagram of the second negative electrode film layer in an embodiment of the secondary battery of the present application.
  • FIG. 4 is a schematic diagram of the second negative electrode film layer in an embodiment of the secondary battery of the present application.
  • FIG. 5 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 6 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 7 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 8 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 9 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 8 .
  • FIG. 10 is a schematic diagram of an embodiment of a device using a secondary battery as a power source of the present application.
  • the drawings are not necessarily drawn to actual scale.
  • the reference numerals are as follows: 10 electrode assembly, 11 positive electrode piece, 12 isolation film, 13 negative electrode piece, 13a first surface, 13b second surface, 131 negative electrode film layer and/or disposed in the starting area Negative electrode film layer provided in the finishing area, 130 second negative electrode film layer, 1310 central area, 1320 outer peripheral area, 1321 first part, 1322 second part, 1321a outer contour line of the first part, 1321b inner contour line of the first part, 1 Battery pack, 2 upper box, 3 lower box, 4 battery module, 5 secondary battery, 51 shell, 52 electrode assembly, 53 cover.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • every point or individual value between the endpoints of a range is included in the range.
  • each point or single value may serve as a lower or upper limit on its own in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • 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).
  • an SEI (solid electrolyte interface) film inevitably forms on the surface of the negative active material, causing irreversible consumption of active ions, resulting in irreversible capacity loss of the secondary battery that is difficult to eliminate.
  • lithium supplementation technology can be used to increase the active lithium content and compensate for the loss of active lithium during the first charging process of lithium-ion secondary batteries.
  • the main one with high technological maturity is the negative electrode lithium replenishment process.
  • the surface of the negative electrode sheet is covered with a lithium metal layer through lithium powder or lithium foil.
  • This lithium can be used in the manufacturing and full life cycle of lithium-ion secondary batteries. During use, it gradually releases and compensates for the loss of active lithium caused by internal side reactions in the lithium-ion secondary battery, thus greatly avoiding the capacity drop of the lithium-ion secondary battery.
  • a lithium source (such as a lithium metal layer) is usually provided on the surface of the negative electrode current collector to supplement lithium for the lithium-ion secondary battery.
  • the inventor found that when the lithium source is placed on the surface of the negative electrode current collector and the electrolyte is injected into the secondary battery, the lithium in the lithium source will form Li + under the action of the potential difference, and these Li + will be preferentially embedded in the closest distance negative electrode film layer.
  • a large amount of Li + embedded in a small area of the negative electrode film may lead to excessive local Li + , making it difficult to fully embed it, thereby inducing risks such as lithium precipitation on the surface of the negative electrode sheet, reduced cycle performance, and battery short circuit.
  • the negative electrode film layer may include a first negative electrode film layer that is opposite to the positive electrode film layer through a separator film and a third negative electrode film layer that is not opposite to the positive electrode film layer. Two negative electrode film layers.
  • the first negative electrode film layer can also be called the negative electrode film layer in the reaction zone.
  • the negative electrode film layer may also include a second negative electrode film layer, that is, a negative electrode film layer that is not disposed opposite to the positive electrode film layer.
  • the second negative electrode film layer may also be called a non-reactive region negative electrode film layer.
  • Li + embedded in the non-reactive area is difficult to return to the positive electrode during the discharge process, which will also cause irreversible loss of active lithium, thus reducing the first Coulombic efficiency, cycle performance and storage performance of lithium-ion secondary batteries.
  • the inventor has provided a secondary battery, a battery module containing the secondary battery, a battery pack and an electrical device after in-depth thinking.
  • a first aspect of this application provides a secondary battery, which includes: a positive electrode piece, a separator film and a negative electrode piece.
  • the positive electrode sheet is provided with a positive electrode film layer
  • the negative electrode sheet includes a first negative electrode film layer and a second negative electrode film layer, wherein the first negative electrode film layer is arranged opposite to the positive electrode film layer through a separation film.
  • the second negative electrode film layer includes a negative electrode film layer that is not opposite to the positive electrode film layer.
  • the second negative electrode film layer includes a central region and a peripheral region surrounding the central region, wherein at least a part of the peripheral region of the second negative electrode film layer stores a lithium source for supplementing lithium to the first negative electrode film layer.
  • the first negative electrode film layer may also be called the reaction zone negative electrode film layer
  • the second negative electrode film layer may also be called the non-reaction zone negative electrode film layer.
  • the secondary battery of the present application may include an electrode assembly having a laminated structure.
  • the electrode assembly 10 includes a positive electrode piece 11 , an isolation film 12 and a negative electrode piece 13 .
  • the negative electrode tab 13 located at the outermost side of the electrode assembly includes a first surface 13 a facing the outside of the electrode assembly 10 and a second surface 13 b facing the inside of the electrode assembly 10 .
  • the electrode assembly 10 includes two outermost negative electrode pieces 13 , and a negative electrode film layer (not shown in the figure) may be disposed on the first surface 13 a of one or both of them.
  • the negative electrode film layer provided on the first surface 13a is an example of the second negative electrode film layer according to the embodiment of the present application.
  • a negative electrode film layer is also provided on other surfaces of the negative electrode sheet in the electrode assembly 10 (including surface 13b), which faces the positive electrode film layer (not shown in the figure) provided on the positive electrode sheet 11 across the isolation film 12. .
  • Such a negative electrode film layer is an example of the first negative electrode film layer according to the embodiment of the present application.
  • the secondary battery of the present application may include an electrode assembly having a wound structure.
  • the electrode assembly 10 includes a positive electrode piece 11 , an isolation film 12 and a negative electrode piece 13 .
  • the negative electrode sheet 13 may be provided with a negative electrode film layer 131 in a starting area along the winding direction (the central unwound area of the electrode assembly) and an ending area along the winding direction (the peripheral ending area of the electrode assembly). It is easy to understand that in the electrode assembly 10 , the negative electrode film layer 131 provided in the starting region and/or the negative electrode film layer 131 provided in the ending region is an example of the second negative electrode film layer according to the embodiment of the present application.
  • negative electrode sheet 13 may include a negative electrode film layer (not shown in the figure) opposite to the positive electrode film layer (not shown in the figure) on the positive electrode sheet 11.
  • a negative electrode film layer is based on An example of the first negative electrode film layer according to the embodiment of the present application.
  • the central region and the peripheral region have meanings known in the art.
  • the central region may represent a region closer to the geometric center of the second negative electrode film layer than the peripheral region; and the peripheral region may represent a region closer to the edge of the second negative electrode film layer than the central region.
  • This application does not limit the shape of the central area and the peripheral area.
  • the central area can be a rectangle, a square, a parallelogram, a circle, an ellipse, a polygon or an irregular shape.
  • the lithium source of the present application may be a lithium source formed by placing a lithium replenishing agent on the surface of the peripheral area of the second negative electrode film layer.
  • the lithium replenishing agent can be a lithium replenishing agent that is well known in the art and can be used for negative electrodes.
  • it can include but is not limited to metal lithium foil, lithium powder, silicon-lithium alloy, aluminum-lithium alloy, magnesium-lithium alloy, tin-lithium alloy and others. form of lithium alloy.
  • the lithium source may include a lithium-rich compound formed by the reaction of the lithium replenishing agent with the negative electrode active material in the negative electrode film layer and the possible unreacted lithium replenishing agent.
  • the lithium source may include a lithium replenishing agent, LiC x (x ⁇ 6) generated by the reaction of the lithium replenishing agent and the carbon negative electrode material, Li y Siz (y>0) generated by the reaction of the lithium replenishing agent and the silicon negative electrode material, etc. At least one of. In some embodiments, at least part of the surface of the outer peripheral area of the second negative electrode film layer can be covered with lithium metal to form a lithium replenishing layer, and then the electrolyte is injected into the secondary battery, so that the lithium replenishing layer and the negative electrode film layer are The negative active material reacts to form the lithium source of the present application.
  • the standard electrode potential of lithium metal for hydrogen is -3.05V
  • the standard potential of negative active materials without lithium (such as graphite, silicon-carbon composite materials, etc.) for hydrogen is about 0V.
  • a lithium source used to supplement lithium to the first negative electrode film layer is stored in the peripheral area of the second negative electrode film layer, which can effectively improve the first Coulombic efficiency, storage performance and Cycle performance.
  • a lithium source for supplementing lithium to the first negative electrode film layer is stored in the peripheral area of the second negative electrode film layer of the present application, and the area where the lithium source is stored can have a low potential. Therefore, when the lithium ion secondary battery is charged, after the Li + detached from the positive electrode is embedded in the first negative electrode film layer, although the potential of the first negative electrode film layer decreases, the first negative electrode film layer and the second negative electrode film layer The potential difference can be maintained small, thereby preventing Li + from diffusing and intercalating into the second negative electrode film layer. During the discharge process of the lithium-ion secondary battery, the potential of the first negative electrode film layer will gradually increase.
  • the lithium source When the potential of the first negative electrode film layer is much higher than the potential of the second negative electrode film layer, the lithium source will be in the first negative electrode film layer. Li + is formed driven by the potential difference between the film layer and the second negative electrode film layer, and diffuses toward the first negative electrode film layer at a slow speed. As a result, the active lithium lost during the charge and discharge cycles of the lithium-ion secondary battery can be replenished, thereby significantly improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery. Furthermore, the lithium source of the present application is stored in the peripheral area of the second negative electrode film layer. Compared with the central area, the distance between the outer peripheral area and the first negative electrode film layer is shorter. When the lithium source forms Li + driven by the potential difference, Li + can have a shorter diffusion path, thereby avoiding the loss of Li + during the diffusion process, thereby significantly improving the efficiency of lithium replenishment and the utilization rate of the lithium source.
  • the equivalent circular area diameter R of the second negative electrode film layer and the equivalent circular area diameter R 1 of the outer peripheral region can satisfy: 0.257R ⁇ R 1 ⁇ 0.9434R, 0.3R ⁇ R 1 ⁇ 0.85R, 0.35R ⁇ R 1 ⁇ 0.8R, 0.4R ⁇ R 1 ⁇ 0.75R, 0.45R ⁇ R 1 ⁇ 0.7R, 0.5R ⁇ R 1 ⁇ 0.65R or 0.55R ⁇ R 1 ⁇ 0.6R.
  • the equivalent circle area diameter may represent the diameter corresponding to a circle having the same area as the defined area.
  • the equivalent circle area diameter of the second negative electrode film layer means: the diameter corresponding to a circle with the same area as the second negative electrode film layer;
  • the equivalent circle area diameter of the outer peripheral area means: the diameter corresponding to the circle with the same area as the outer peripheral area. corresponding diameter.
  • the equivalent circular area diameter of the second negative electrode film layer and the equivalent circular area diameter of the outer peripheral region satisfy the above conditions, which can allow the lithium source of the present application to have appropriate storage space, so that it can The secondary battery is replenished with an appropriate amount of active lithium ions through a lithium source.
  • the equivalent circular area diameter of the second negative electrode film layer and the equivalent circular area diameter of the outer peripheral region meet the above conditions, which enables the Li + formed by the lithium source driven by the potential difference to have a suitable diffusion path, thereby improving lithium replenishment. efficiency and utilization of lithium sources. As a result, the first Coulombic efficiency, cycle performance and storage performance of the secondary battery can be further improved.
  • the peripheral area has a first part and a second part surrounding the first part, and the equivalent circular area diameter R 2 of the second part may satisfy: 0 ⁇ R 2 ⁇ R 1 , optionally Specifically, 0 ⁇ R 2 ⁇ 0.5R 1 , more optionally, 0 ⁇ R 2 ⁇ 0.1R 1 , wherein the lithium source is stored in the first part.
  • the first part may be annular, elliptical, hollow rectangular, etc. or have an irregular shape. At least a part of the first part stores a lithium source for supplementing lithium to the first negative electrode film layer.
  • the inventor found that the farther the lithium replenishment area is from the edge of the second negative electrode film layer, the longer the diffusion path of Li + released from the lithium source, and correspondingly, the lower the lithium replenishment efficiency. .
  • the edge of the second negative electrode film layer is easily affected by external force. Therefore, the lithium source located at the edge of the second negative electrode film layer may separate from the negative electrode piece, thereby causing the loss of the lithium source. Dividing the peripheral area into a first part and a second part located at the edge of the second negative electrode film layer allows the lithium source to be stored in the first part, which enables the lithium source to stably exist in the second negative electrode film layer, thereby reducing the risk of lithium source loss. . As a result, the efficiency of lithium replenishment of the secondary battery can be improved.
  • the first part is annular, and the minimum distance d 1 between the outer contour of the first part and the edge of the second negative electrode film layer and the width d 0 of the second negative electrode film layer can satisfy: 0 ⁇ d 1 ⁇ d 0 /6.
  • the annular shape is not limited, and may specifically include a figure enclosed by a closed outer contour and a closed inner contour.
  • the first part may be annular, elliptical, hollow rectangular, etc. or have an irregular shape.
  • FIG. 3 is a schematic diagram of the second negative electrode film layer in an embodiment of the secondary battery of the present application.
  • the exemplary second negative electrode film layer 130 includes a central region 1310 and an outer peripheral region 1320 .
  • the outer peripheral area 1320 is composed of an elliptical ring-shaped first part 1321 and a second part 1322.
  • the first part 1321 is enclosed by an outer contour 1321a and an inner contour 1321b. At least a part of the first part 1321 stores a lithium source for supplementing lithium to the first negative electrode film layer.
  • the minimum distance d 1 between the outer contour 1321a of the first part and the edge of the second negative electrode film layer can be as shown in FIG. 3 .
  • FIG. 4 is a schematic diagram of the second negative electrode film layer in another embodiment of the secondary battery of the present application.
  • the exemplary second negative electrode film layer 130 includes a central region 1310 and an outer peripheral region 1320 .
  • the outer peripheral area 1320 is composed of a first part 1321 and a second part 1322 that are hollow rectangular.
  • the first part 1321 is enclosed by an outer contour 1321a and an inner contour 1321b.
  • At least a part of the first part 1321 stores a lithium source for supplementing lithium to the first negative electrode film layer.
  • the minimum distance d 1 between the outer contour line 1321a of the first part and the edge of the second negative electrode film layer 130 can be as shown in FIG. 4 .
  • the minimum distance d 1 between the outer contour of the first part and the edge of the second negative electrode film layer is within the above-mentioned appropriate range, which can ensure that the Li + extracted from the lithium source has an appropriate length. While reducing the diffusion path, it effectively reduces the risk of lithium source falling off. As a result, the efficiency of lithium replenishment of the secondary battery can be improved, thereby improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery.
  • the secondary battery may satisfy: d 3 ⁇ d 2 ⁇ d 0 /6, where d 2 represents the distance between the outer contour and the side in the length direction of the second negative electrode film layer.
  • the minimum distance, d3, represents the minimum distance between the outer contour and the side in the width direction of the second negative electrode film layer.
  • d 2 represents the minimum distance between the outer contour 1321 a and the side in the length direction of the second negative electrode film layer 130
  • d 3 represents the outer contour and the second negative electrode film layer 130 .
  • the minimum distance between sides in the width direction of 130. Among them, d 3 ⁇ d 2 ⁇ d 0 /6, at this time, d 3 d 1 .
  • the first part 1321 is a hollow rectangle, and the first part 1321 can satisfy: 0 ⁇ d4 ⁇ d0 /3, and/or 0 ⁇ d5 ⁇ l0 / 3.
  • d 4 represents the width of the first part 1321 along the width direction of the second negative electrode film layer 130 ;
  • d 5 represents the width of the first part 1321 in the length direction of the second negative electrode film layer 130 , and
  • l 0 represents the The length of the second negative electrode film layer 130.
  • the first part may be a hollow rectangle, and the geometric centers of the outer contour and the inner contour of the first part may not coincide with each other.
  • the first part has two unequal widths d 41 and d 42 along the width direction of the second negative electrode film layer.
  • d 41 and d 42 can both satisfy greater than 0 and less than or equal to d 0 /3; the first part has two unequal widths along the second negative electrode film layer.
  • the negative electrode film layer has two unequal widths d 51 and d 52 in the length direction, and d 51 and d 52 can both satisfy the requirements of being greater than 0 and less than or equal to l 0 /3.
  • the first portion has a suitable width such that the first portion has a suitable area to be able to store an appropriate amount of lithium source.
  • the first part has a suitable width, which in turn allows the second part and the central area to have a suitable area. Therefore, when the lithium source is stored in the first part, it can have an appropriate distance from the center of the second negative electrode film layer and/or the edge of the second negative electrode film layer. Therefore, the second negative electrode film layer of the present application can store appropriate active lithium. Not only is the active lithium not easy to fall off from the second negative electrode film layer, but when the secondary battery needs to replenish lithium ions, the active lithium can also pass through relatively The short path diffuses and embeds the first negative electrode film layer. Therefore, the secondary battery of the present application can have high first Coulombic efficiency and good cycle performance and storage performance.
  • the secondary battery may satisfy: 1 mm ⁇ d 2 ⁇ 5 mm.
  • (l 0 -10mm) ⁇ l 1 ⁇ (l 0 -2mm), l 1 represents the length of the outer contour.
  • (d 0 -10mm) ⁇ l 2 ⁇ (d 0 -2mm), l 2 represents the width of the outer contour line.
  • the secondary battery meets at least one of the above conditions, it is beneficial for the second negative electrode film layer to provide enough space for storing the lithium source, and the lithium source can be appropriately distributed in the second negative electrode film layer.
  • the lithium source is not only difficult to fall off from the second negative electrode film layer, but when the secondary battery needs to replenish lithium ions, the Li + provided by the lithium source can also diffuse through a shorter path and be embedded in the first negative electrode film layer. Therefore, the secondary battery of the present application can have high first Coulombic efficiency and good cycle performance and storage performance.
  • the lithium source is distributed annularly in the first part.
  • the second negative electrode film layer when the lithium source is distributed in an annular shape in the first part, the second negative electrode film layer can have a suitable potential. As a result, Li + in the first negative electrode film layer is less likely to be embedded in the second negative electrode film layer, thereby further reducing the loss of active lithium. Therefore, the secondary battery of the present application can have high first Coulombic efficiency, good cycle performance and storage performance.
  • the area S 1 of the second negative electrode film layer storing the lithium source and the area S 2 of the peripheral region may satisfy: 10% ⁇ S 1 /S 2 ⁇ 100%. Alternatively, 80% ⁇ S 1 /S 2 ⁇ 100%, more optionally, 90% ⁇ S 1 /S 2 ⁇ 100%.
  • the ratio of S 1 to S 2 is within the above-mentioned appropriate range, so that the amount of lithium source stored in the second negative electrode film layer is appropriate.
  • the appropriate amount of lithium source can, on the one hand, make the second negative electrode film layer have a suitable potential, thereby reducing the Li + in the first negative electrode film layer to escape and embed in the second negative electrode film layer; on the other hand, it can provide enough active lithium In the case of ions, avoid excess lithium source. This can reduce the loss of Li + during the cycle of the secondary battery, improve the efficiency of lithium replenishment, and control the cost of lithium replenishment. Therefore, the secondary battery of the present application can have high first Coulombic efficiency, good cycle performance and storage performance, and low cost.
  • the lithium source may include at least one of lithium metal, lithium alloy, a composite of lithium metal and anode active material, a composite of aluminum alloy and anode active material, optionally lithium metal and/or lithium A composite of metal and negative active material.
  • the lithium alloy includes at least one of silicon-lithium alloy, aluminum-lithium alloy, magnesium-lithium alloy, and tin-lithium alloy.
  • metal lithium foil, lithium powder, silicon-lithium alloy, aluminum-lithium alloy, magnesium-lithium alloy, tin-lithium alloy and other forms of lithium alloy can be used as lithium supplements. layer, and interacts with the active material in the second negative electrode film layer to form the lithium source of the present application.
  • lithium metal including metallic lithium foil, lithium powder, etc.
  • metallic lithium foil has good processing performance.
  • the lithium replenishment efficiency can be improved and the lithium replenishment efficiency can be improved.
  • the secondary battery of the present application has high productivity.
  • the secondary battery can satisfy: 20% C 0 ⁇ C Li ⁇ 120% C 0 , where C 0 represents the active material capacity per unit area of the second negative electrode film layer, and C Li represents the Describe the unit area capacity of the lithium source.
  • C 0 represents the active material capacity per unit area of the second negative electrode film layer
  • C Li represents the Describe the unit area capacity of the lithium source.
  • 90%C 0 ⁇ C Li ⁇ 120%C 0 90%C 0 ⁇ C Li ⁇ 120%C 0 ,
  • the active material capacity C 0 per unit area of the second negative electrode film layer can represent: the capacity of the negative electrode active material in the second negative electrode film layer per unit area. Normally, C 0 may be equal to the active material capacity per unit area of the first negative electrode film layer.
  • the capacity per unit area of the lithium source C Li can represent the capacity of the lithium source contained in the second negative electrode film layer per unit area in which the lithium source is stored.
  • the inventor unexpectedly discovered that when C 0 and C Li meet the above conditions, the secondary battery can have high first Coulombic efficiency, good cycle performance, good storage performance and good safety performance.
  • C Li when C Li is small, the area where the lithium source is stored has a higher potential.
  • the second negative electrode film layer forms a sufficient potential difference to drive the lithium source to extract Li + and diffuse toward the first negative electrode film layer at a slow speed.
  • C Li is large, the area where the lithium source is stored has a lower potential, and it is easy to form a sufficient potential difference with the second negative electrode film layer, allowing the lithium source to quickly desorb Li + .
  • the secondary battery has a winding structure
  • the second negative electrode film layer includes a starting area and an ending area along the winding direction
  • the secondary battery can satisfy: C A ⁇ C B
  • CA represents the capacity of the lithium source located in the starting area
  • CB represents the capacity of the lithium source located in the ending area.
  • the inventor found that compared to the second negative electrode film layer located in the ending area, the second negative electrode film layer located in the starting area has a better ability to retain the electrolyte, thereby being more conducive to the lithium source Diffusion of liberated Li + .
  • the lithium source capacity in the starting area is higher, which is beneficial to improving the lithium replenishment efficiency and the utilization rate of the lithium source.
  • the minimum distance d 7 between the lithium source and the first negative electrode film layer may satisfy: 0 ⁇ d 7 ⁇ 10 mm.
  • the minimum distance between the lithium source and the first negative electrode film layer is within the above-mentioned appropriate range, which can allow the Li + extracted from the lithium source to have a shorter diffusion path, thereby improving the lithium replenishment efficiency and Lithium source utilization.
  • the surface of the central region is covered with a barrier layer including a barrier film and/or a barrier coating.
  • a barrier layer including a barrier film and/or a barrier coating.
  • This application does not limit the material of the barrier film, as long as it can prevent the electrolyte from contacting the central area. It can be a film with one-sided adhesiveness or double-sided adhesiveness, preferably a single-sided adhesive film.
  • the bonding force between at least one surface of the barrier film and the surface of the central region may be greater than 20 N/m. More optionally, the bonding force between the barrier film and the surface of the central region is greater than the cohesive force of the second negative electrode film layer.
  • the barrier film is selected from at least one of cast polypropylene film, uniaxially oriented polypropylene film, biaxially oriented polypropylene film, polyethylene film, polyester fiber film, and polyvinyl chloride film.
  • the barrier coating includes polyvinylidene fluoride, polytetrafluoroethylene, polyphenylpropamide, polyamide, polyimide, polymethyl methacrylate, polyurethane, polystyrene, polyacrylic acid, polyacrylamide, poly At least one of acrylonitrile or copolymers of the above substances.
  • covering the surface of the central area with a barrier layer can reduce the risk of electrolyte infiltration into the central area.
  • the active Li + in the secondary battery can be reduced to be embedded in the negative electrode film layer in the central area, thereby further improving the lithium replenishment efficiency and the utilization rate of the lithium source, thereby improving the first Coulombic efficiency, cycle performance and storage performance of the secondary battery.
  • the barrier layer has a thickness of 6 ⁇ m to 40 ⁇ m, and more optionally, the barrier layer has a thickness of 10 ⁇ m to 20 ⁇ m.
  • the thickness of the barrier layer When the thickness of the barrier layer is within a suitable range, it can not only have good mechanical strength and thus be less likely to be damaged, but also enable the thickness of the negative electrode piece to be within a smaller range, thereby facilitating the processing of the negative electrode piece.
  • the length and width of the negative electrode film layer have meanings known in the art.
  • the length of the negative electrode film layer may represent the length of the negative electrode film layer along the winding direction of the electrode assembly
  • the width of the negative electrode film layer may represent the length of the negative electrode film layer perpendicular to the winding direction. direction length.
  • the length of the negative electrode film layer may represent the length of the longer side of the negative electrode film layer
  • the width of the negative electrode film layer may represent the length of the shorter side of the negative electrode film layer.
  • C 0 can be obtained by performing a capacity test on the second negative electrode film layer in which no lithium source is stored. As an example, scrub one side of the negative electrode film layer to expose the empty substrate, punch the pole piece containing one side of the negative electrode film layer into small discs with an area S, and use a button type lithium half cell to test the small discs containing the negative electrode film layer.
  • C Li can be calculated by methods known in the art.
  • the capacity C 1 of the lithium foil can be calculated based on the weight and theoretical gram capacity of the lithium foil, and then the area S of the lithium foil can be measured.
  • C Li can be calculated.
  • 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 and including a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its 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 film layer includes the first negative electrode film layer and the second negative electrode film layer described in the present application.
  • the type of negative electrode active material is not particularly limited, and negative electrode active materials known in the art for secondary batteries can be used.
  • the negative active material may include one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite, and silicon alloy materials.
  • the tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative active material includes one or more of artificial graphite, natural graphite, and silicon-based materials.
  • the negative active material is selected from the above types of materials, which can make the second negative electrode film layer have a suitable potential, thereby improving the lithium replenishment efficiency and the lithium source utilization rate.
  • the negative electrode current collector can be a metal foil or a composite current collector.
  • a metal foil a copper foil can be used as the negative electrode current collector.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly One or more types of ethylene (PE).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE poly One or more types of ethylene
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional adhesive, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or water, but is not limited thereto.
  • the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, Ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • Binders may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • Other optional additives include thickeners (such as carboxymethyl cellulose sodium CMC-Na), PTC thermistor materials, etc.
  • the negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet described in the present application may further include a conductive undercoat layer (for example, composed of a conductive agent and an adhesive) disposed between the negative electrode current collector and the negative electrode film layer.
  • the negative electrode sheet described in this application further includes a protective layer covering the surface of the negative electrode film layer.
  • 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 and including a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its 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 type of the positive electrode active material is not particularly limited, and a positive electrode active material known in the art for secondary batteries can be used.
  • the cathode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium iron manganese phosphate, lithium iron manganese phosphate
  • One or more of the composite materials with carbon and their respective modified compounds may be used. The present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for secondary batteries can also be used.
  • the type of negative electrode current collector is not subject to specific restrictions and can be selected according to actual needs.
  • the positive electrode current collector can be a metal foil or a composite current collector (metal materials can be disposed on a polymer substrate to form a composite current collector).
  • the positive electrode current collector may be aluminum foil.
  • the positive electrode film layer usually includes a positive electrode active material and an optional binder and an optional conductive agent. It is usually coated with a positive electrode slurry, dried and cold-pressed. .
  • the cathode slurry is usually formed by dispersing the cathode active material and optional conductive agent and binder in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP).
  • the binder used for the positive electrode membrane layer may include one or more of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • the conductive agent used for the positive electrode film layer may include one or more of superconducting carbon, carbon black (for example, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene and carbon nanofibers. .
  • the secondary battery of the present application has no specific restrictions on the type of electrolyte, and can be selected according to needs.
  • the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, electrolyte).
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt can be selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (bisfluorosulfonate) Lithium imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium triflate), LiDFOB (lithium difluoromethanesulfonate), LiBOB (lithium difluoromethanesulfonate), LiPO 2 F 2 One or more of (lithium difluorodifluorophosphate), LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl s
  • EC
  • additives are optionally included in the electrolyte.
  • 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 the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, and additives that improve the low-temperature performance of the battery. Additives etc.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • 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 can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 5 , a square-structured secondary battery 5 is shown 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 is used to 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 several, and can be adjusted according to needs.
  • the secondary batteries according to the present application can be assembled into battery modules.
  • the number of secondary batteries contained in the battery module can be multiple. The specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 7 is a schematic diagram of the 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, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover 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 of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • Figure 10 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 including the secondary battery of the present application may be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain positive electrode sheets.
  • the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and then processed, dried, cold pressed, and cut to obtain negative electrode sheets.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the above-mentioned positive electrode pieces, isolation films and negative electrode pieces are stacked in order so that the isolation film plays an isolation role between the positive and negative electrode pieces.
  • a laminated electrode assembly is obtained; the laminated electrode assembly is placed In the outer packaging shell, after drying, the electrolyte is injected, and through processes such as vacuum packaging, standing, formation, and shaping, a secondary battery is obtained.
  • a lithium replenishing agent is applied to the surface of the outer peripheral area of the second negative electrode film layer of the negative electrode piece to form the second negative electrode film layer as shown in Figure 4 after the electrolyte is injected.
  • the lithium replenishing agent is discontinuously applied to the peripheral area to form a discontinuously distributed lithium source.
  • the lithium replenishing agent is continuously applied to the peripheral area to form a continuously distributed lithium source.
  • the above-mentioned positive electrode plates, isolation films, and negative electrode plates are stacked in order so that the isolation film plays an isolation role between the positive and negative electrode plates.
  • a rolled electrode assembly is obtained; the rolled electrode assembly is obtained It is placed in an outer packaging shell, dried and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.
  • the second negative electrode film layer located in the starting area, and/or the outer peripheral area of the second negative electrode film layer (denoted as B side) located in the ending area
  • the lithium replenishing agent is applied to the surface, so that after the electrolyte is injected, the second negative electrode film layer as shown in Figure 4 is formed on the A side and/or the B side respectively.
  • the positive electrode sheets, negative electrode sheets, electrolytes, separators and secondary batteries of Examples 19-20 were prepared.
  • the central area of surface A of Example 19 is coated with a polyethylene isolation film with a thickness of 20 ⁇ m
  • the central area of surface A of Example 20 is coated with a polytetrafluoroethylene coating with a thickness of 20 ⁇ m.
  • the d 0 of the A side is 100 mm
  • the l 0 of the A side is 150 mm
  • the d 0 of the B side is 100 mm
  • the l 0 of the B side is 165 mm.
  • R, R 2 /R 1 , d 2 , d 3 , d 4 , d 5 , 1 1 , l 2 , S 1 /S 2 , and C Li /C 0 are shown in Table 1 respectively.
  • Examples 13 to 20 based on the total capacity of the lithium source, the capacity ratio of the lithium source stored on the A side C A , the capacity ratio of the lithium source stored on the B side C B , negative active material, lithium replenishing agent, d 7 They are shown in Table 1-2.
  • the positive electrode sheets, negative electrode sheets, electrolytes, separators and secondary batteries of Comparative Examples 1 to 2 were prepared according to Table 1-1, wherein the No lithium replenishing agent is applied to the surface of the outer peripheral area of the second negative electrode film layer.
  • the positive electrode sheets, negative electrode sheets, electrolytes, separators and secondary batteries of Comparative Examples 3 to 4 were prepared according to Table 1-2, wherein the No lithium replenishing agent is applied to the surface of the outer peripheral area of the second negative electrode film layer.
  • the measured capacity measured by charging at 0.02C rate for 10 hours at 45°C is marked as C0, then charged at 25°C at 0.33C rate to 3.65V, and the measured capacity measured by charging at 3.65V constant voltage to 0.05C is marked as C1. Finally, the capacity measured by discharging at 0.33C to 2.5V is marked as D0.
  • the first Coulombic efficiency of the secondary battery D0/(C0+C1) ⁇ 100%.
  • C dn n represents the number of days of storage; let it stand for 5 minutes; charge to 3.65V at 0.33D0; charge to 0.05D0 (fully charged state) at 3.65V constant voltage; transfer the secondary battery to an environment of 45°C storage.
  • Examples 1 to 12 have better performance in the second negative electrode film layer of the secondary battery with a laminated structure.
  • the first Coulombic efficiency of the secondary battery can be increased by more than 0.3%
  • the reversible capacity retention rate can be increased by more than 0.7%
  • the cycle life can be increased by more than 79 cycles.
  • arranging a lithium source in the peripheral area of the second negative electrode film layer can achieve efficient lithium replenishment of the secondary battery, thereby effectively improving the first Coulombic efficiency and long-term cycle performance of the secondary battery.
  • Examples 1 to 7 It can be seen from Examples 1 to 7 that arranging a lithium source in the peripheral area of the second negative electrode film layer, with an appropriate area of the lithium source, and an appropriate distance between the lithium source and the edge of the second negative electrode film layer, can improve the lithium replenishment efficiency and lithium replenishment efficiency. source utilization. It can be seen from Example 8 that compared with discontinuously distributed lithium sources, continuously distributed lithium sources can have higher lithium replenishment efficiency and lithium source utilization rate. It can be seen from Examples 9 and 10 that the lithium source is stored in the peripheral area of the second negative electrode film layer, and C Li /C 0 is in the range of 20% to 120%, which can effectively improve the first Coulombic efficiency and long-term efficiency of the secondary battery.
  • Examples 13 to 20 are provided in the outer peripheral area of the second negative electrode film layer of the secondary battery with a rolled structure.
  • the lithium source With the lithium source, the first Coulombic efficiency of the secondary battery can be increased by more than 0.3%, the reversible capacity retention rate can be increased by more than 1%, and the cycle life can be increased by more than 139 cycles. It can be seen that arranging a lithium source in the peripheral area of the second negative electrode film layer can achieve efficient lithium replenishment of the secondary battery, thereby effectively improving the first Coulombic efficiency and long-term cycle performance of the secondary battery.
  • Examples 13 to 15 It can be seen from Examples 13 to 15 that arranging a lithium source in the peripheral area of the second negative electrode film layer, with an appropriate area of the lithium source, and an appropriate distance between the lithium source and the edge of the second negative electrode film layer, can improve the lithium replenishment efficiency and lithium replenishment efficiency. source utilization. It can be seen from Examples 17 and 18 that when the secondary battery has a wound structure, compared with arranging the lithium source in the ending area of the winding, arranging the lithium source in the starting area of the winding can achieve higher lithium replenishment efficiency.
  • Examples 19 and 20 it can be seen from Examples 19 and 20 that providing a barrier layer in the central area of the second negative electrode film layer can effectively reduce the infiltration of the electrolyte into the negative electrode film layer in the central area, thereby improving the first Coulombic efficiency and reversible capacity retention of the secondary battery. rate and cycle life.

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Abstract

本申请公开了一种二次电池、含有该二次电池的电池模块、电池包及用电装置，该二次电池包括：正极极片，包括正极膜层；隔离膜；负极极片，包括第一负极膜层，所述第一负极膜层隔着所述隔离膜与所述正极膜层相对设置，和第二负极膜层，所述第二负极膜层包括不与所述正极膜层相对设置的负极膜层，所述第二负极膜层包括中心区域和围绕所述中心区域的外周区域，其中，所述第二负极膜层的所述外周区域中的至少一部分中存储有用于向所述第一负极膜层补充锂的锂源。

Description

二次电池、含有该二次电池的电池模块、电池包及用电装置 技术领域
本申请属于二次电池技术领域，具体涉及一种二次电池、含有该二次电池的电池模块、电池包及用电装置。
背景技术
二次电池依靠活性离子在正极和负极之间往复脱嵌来进行充电和放电，其具有能量密度高、循环寿命长，以及无污染、无记忆效应等突出特点。因此，二次电池作为清洁能源，已由电子产品逐渐普及到电动汽车等大型装置领域，以适应环境和能源的可持续发展战略。由此，也对二次电池的能量密度提出了更高的要求。
但是，二次电池在首次充电过程中，负极活性材料表面不可避免地形成SEI(solid electrolyte interface，固体电解质界面)膜，造成活性离子不可逆消耗，由此导致二次电池的不可逆容量损失难以消除，给二次电池能量密度的提升带来挑战。
发明内容
本申请的目的在于提供一种二次电池、含有该二次电池的电池模块、电池包及用电装置，旨在使二次电池具有高能量密度、良好的循环性能和存储性能。
为了实现上述发明目的，本申请第一方面提供一种二次电池，包括正极极片，其上设置有正极膜层；隔离膜；负极极片，包括第一负极膜层，所述第一负极膜层隔着所述隔离膜与所述正极膜层相对设置，和第二负极膜层，所述第二负极膜层包括不与所述正极膜层相对设置的负极膜层，所述第二负极膜层包括中心区域和围绕所述中心区域的外周区域，其中，所述第二负极膜层的所述外周区域中的至少一部分中存储有用于向所述第一负极膜层补充锂的锂源。
本申请的二次电池中，负极极片的第二负极膜层的外周区域中存储有用于向第一负极膜层补充锂的锂源，存储有该锂源的区域能够具有低电势。由此，在锂离子二次电池充电时，正极脱出的Li +嵌入第一负极膜层后，第一负极膜层的电位虽有有所下降，但是第一负极膜层与第二负极膜层能够保持较小的电势差，从而能够防止Li +向第二负极膜层扩散和嵌入。在锂离子二次电池放电的过程中，第一负极膜层的电势会逐渐升高，当第一负极膜层的电势远高于第二负极膜层的电势时，锂源会在第一负极膜层和第二负极膜层之间的电势差的驱动下形成Li +，并以缓慢的速度向第一负极膜层扩散。由此，能够补充锂离子二次电池充放电循环中损失的活性锂，从而显著提升二次电池的首次库伦效率、循环性能和存储性能。进一步地，本申请的锂源存储于第二负极膜层的外周区域，相较于中心区域，外周区域与第一负极膜层之间的距离更短。当锂源在电势差的驱动下 形成Li +时，Li +能够具有更短的扩散路径，从而能够避免Li +在扩散过程中发生损失，进而显著提升补锂的效率和锂源的利用率。
在本申请任意实施方式中，所述第二负极膜层的等效圆面积直径R与所述外周区域的等效圆面积直径R 1满足：0.257R≤R 1≤0.9434R。第二负极膜层的等效圆面积直径与外周区域的等效圆面积直径满足上述条件，能够允许本申请的锂源具有合适的存储空间，从而能够通过锂源向二次电池补充适量的活性锂离子。此外，第二负极膜层的等效圆面积直径与外周区域的等效圆面积直径满足上述条件，能够使得锂源在电势差的驱动下形成的Li +具有合适的扩散路径，从而能够提升补锂的效率和锂源的利用率。由此，能够进一步提升二次电池的首次库伦效率、循环性能和存储性能。
在本申请任意实施方式中，所述外周区域具有第一部分以及围绕所述第一部分的第二部分，所述第二部分的等效圆面积直径R 2满足：0＜R 2＜R 1，可选地，0＜R 2＜0.5R 1，更可选地，0＜R 2＜0.1R 1，其中，所述锂源存储于所述第一部分。补锂区距离第二负极膜层的边缘越远，锂源脱出的Li +的扩散路径越长，相应地，补锂效率也越低。但是，第二负极膜层的边缘容易受到外力的作用，因此，位于第二负极膜层边缘的锂源可能会脱离负极极片，从而造成锂源的损失。将外周区域分为第一部分以及位于第二负极膜层边缘的第二部分，使锂源存储于第一部分，能够使得锂源稳定地存在于第二负极膜层中，从而降低锂源损失的风险。由此，能够提升对二次电池进行补锂的效率。
在本申请任意实施方式中，所述第一部分为环形，所述第一部分的外轮廓线与所述第二负极膜层边缘的最小距离d 1、所述第二负极膜层的宽度d 0满足：0＜d 1≤d 0/6。第一部分的外轮廓线与所述第二负极膜层边缘的最小距离d 1在上述合适的范围内，能够在保证锂源脱出的Li +具有合适长度的扩散路径的同时，有效降低锂源脱落的风险。由此，能够提升对二次电池进行补锂的效率，从而提升二次电池的首次库伦效率、循环性能和存储性能。
在本申请任意实施方式中，d 3≤d 2≤d 0/6，其中，d 2表示所述外轮廓线与所述第二负极膜层的长度方向上的边的最小距离，d 3表示所述外轮廓线与所述第二负极膜层的宽度方向上的边的最小距离。第一部分的外轮廓线与第二负极膜层的长度方向上的边以及第二负极膜层的宽度方向上的边之间均具有一定的距离，且该距离在较小的范围内，能够在保证锂源脱出的Li +具有合适长度的扩散路径的同时，有效降低锂源脱落的风险。由此，能够提升对二次电池进行补锂的效率，从而提升二次电池的首次库伦效率、循环性能和存储性能。
在本申请任意实施方式中，所述第一部分为空心矩形，所述第一部分满足：0＜d 4≤d 0/3，d 4表示所述第一部分沿所述第二负极膜层宽度方向上的宽度；和/或0＜d 5≤l 0/3，d 5表示所述第一部分沿所述第二负极膜层长度方向上的宽度，l 0表示所述第二负极膜层的长度。第一部分具有合适的宽度，能够使得第一部分具有合适的面积，从而能够存储适量的锂源。第一部分具有合适的宽度，还能够相应地允许第二部分和中心区域具有合适的面积。因此，锂源存储于第一部分时，能够与第二负极膜层的中心和/或第二负极膜层的边缘具有合适的距离。由此，本申请的第二负极膜层中能够存储合适的活性锂，该活性锂不仅不易从第二负极膜层中脱落，在二次电池需要补充锂离子时，该活性锂还能够 通过较短的路径扩散并嵌入第一负极膜层。因此，本申请的二次电池能够具备高首次库伦效率以及良好的循环性能和存储性能。
在本申请任意实施方式中，所述二次电池满足：1mm≤d 2≤5mm。可选地，(l 0-10mm)≤l 1≤(l 0-2mm)，l 1表示所述外轮廓线的长度。可选地，10mm≤d 4≤d 0/5。可选地，1mm≤d 3≤5mm。可选地，(d 0-10mm)≤l 2≤(d 0-2mm)，l 2表示所述外轮廓线的宽度。可选地，10mm≤d 5≤d 4。二次电池满足上述条件中的至少一者时，有利于第二负极膜层提供足够的用于存储锂源的空间，并且能够使得锂源在第二负极膜层中的分布位置适当。由此，锂源不仅不易从第二负极膜层中脱落，在二次电池需要补充锂离子时，锂源提供的Li +还能够通过较短的路径扩散并嵌入第一负极膜层。因此，本申请的二次电池能够具备高首次库伦效率以及良好的循环性能和存储性能。
可选地，所述锂源呈环形分布于所述第一部分。锂源呈环形分布于第一部分时，能够使得第二负极膜层具有合适的电势。由此，第一负极膜层中的Li +不易嵌入第二负极膜层中，从而进一步减少了活性锂的损失。因此，本申请的二次电池能够具备高首次库伦效率、良好的循环性能和存储性能。
在本申请任意实施方式中，存储有所述锂源的第二负极膜层的面积S 1与所述外周区域的面积S 2满足：10％≤S 1/S 2≤100％，可选为80％≤S 1/S 2＜100％，更可选为90％≤S 1/S 2＜100％。S 1与S 2的比值在合适的范围内，能够使得第二负极膜层中存储的锂源的量适当。锂源的量适当，一方面能够使得第二负极膜层具有合适的电势，从而减少第一负极膜层中的Li +脱出并嵌入第二负极膜层；另一方面能够提供在足够的活性锂离子的情况下，避免锂源过剩。由此，能够减少二次电池在循环过程中损失的Li +、提升补锂效率、控制补锂的成本。因此，本申请的二次电池能够具备高首次库伦效率、良好的循环性能和存储性能、低成本。
在本申请任意实施方式中，所述锂源包括锂金属、锂合金、锂金属与负极活性材料的复合物、铝合金与负极活性材料的复合物中的至少一者，可选地，所述锂合金包括硅锂合金、铝锂合金、镁锂合金、锡锂合金中的至少一者。无论是金属锂箔、锂粉、硅锂合金、铝锂合金、镁锂合金、锡锂合金及其它形式的锂合金都可以作为补锂层，并与第二负极膜层中的活性物质相互作用形成本申请的锂源，从而实现对二次电池的补锂。
在本申请任意实施方式中，所述二次电池满足：20％C 0≤C Li≤120％C 0，可选地，90％C 0≤C Li≤120％C 0，其中，C 0表示所述第二负极膜层的单位面积活性物质容量，C Li表示所述锂源的单位面积容量。在常规的电池容量设计下，C 0和C Li满足上述条件时，能够使得锂源脱出Li +的速度处于更合适的范围内，从而兼顾补锂效率和二次电池的安全性能。
在本申请任意实施方式中，所述二次电池具有卷绕结构，所述第二负极膜层包括沿卷绕方向的起始区域以及收尾区域，所述二次电池满足：C A≥C B，C A表示位于所述起始区域的锂源的容量，C B表示位于所述收尾区域的锂源的容量。相对于位于收尾区域的第二负极膜层，位于起始区域的第二负极膜层保留电解液的能力更好，从而更有利于锂源脱出的Li +的扩散。锂源的总容量一定时，起始区域的锂源容量更高，有利于提升补锂效率和锂源的利用率。
在本申请任意实施方式中，所述锂源与所述第一负极膜层的最小距离d 7满足：0＜d 7≤10mm。锂源与第一负极膜层的最小距离在上述合适的范围内，能够使得锂源脱出的Li +具有更短的扩散路径，从而提高补锂效率和锂源的利用率。
在本申请任意实施方式中，所述中心区域的表面覆盖有阻隔层，所述阻隔层包括阻隔膜和/或阻隔涂层。其中，所述阻隔膜选自流延聚丙烯薄膜、单向拉伸聚丙烯膜、双向拉伸聚丙烯膜、聚乙烯膜、聚酯纤维膜、聚氯乙烯膜中的至少一者。所述阻隔涂层包括聚偏氟乙烯、聚四氟乙烯、聚苯丙酰胺、聚酰胺、聚酰亚胺、聚甲基丙烯酸甲酯、聚氨酯、聚苯乙烯、聚丙烯酸、聚丙烯酰胺、聚丙烯腈或上述物质的共聚物中的至少一者。在中心区域的表面覆盖有阻隔层，能够降低电解液浸润中心区域的风险。由此，能够减少二次电池中的活性Li +嵌入中心区域的负极膜层，从而进一步提升补锂效率以及锂源的利用率，进而提升二次电池的首次库伦效率、循环性能和存储性能。
可选地，所述阻隔层的厚度为6μm～40μm，更可选地，所述阻隔层的厚度为10μm～20μm。阻隔层的厚度在合适的范围内，既能够具有良好的机械强度，从而不易破损，又能够使得负极极片的厚度在较小的范围内，从而便于负极极片的加工。
本申请第二方面提供一种电池模块，其包括本申请的二次电池。
本申请第三方面提供一种电池包，其包括本申请的电池模块。
本申请第四方面提供一种用电装置，其包括本申请的二次电池、电池模块、或电池包中的至少一种。
本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将简要说明本申请实施例中所需要使用的附图；显而易见地，下面所描述的附图仅仅涉及本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式中，二次电池所包括的电极组件的示意图。
图2是本申请的二次电池的一实施方式中，二次电池所包括的电极组件的示意图。
图3是本申请的二次电池的一实施方式中的第二负极膜层的示意图。
图4是本申请的二次电池的一实施方式中的第二负极膜层的示意图。
图5是本申请的二次电池的一实施方式的示意图。
图6是本申请的二次电池的一实施方式的分解示意图。
图7是本申请的电池模块的一实施方式的示意图。
图8是本申请的电池包的一实施方式的示意图。
图9是图8所示的电池包的实施方式的分解示意图。
图10是本申请的二次电池用作电源的装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。其中，附图标记说明如下：10电极组件，11正极极片，12隔离膜，13负极极片，13a第一表面，13b第二表面，131设置在起始区域中的负极膜层和/或设置在收尾区域的负极膜层，130第二负极膜层，1310中心区 域，1320外周区域，1321第一部分，1322第二部分，1321a第一部分的外轮廓线，1321b第一部分的内轮廓线，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盖板。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例对本申请进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种或两种以上。
在本文的描述中，除非另有说明，术语“或”是包括性的。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)。
应理解，术语“第一”、“第二”、等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或暗示这些实体或操作之间存在任何实际的关系或顺序。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
二次电池在首次充电过程中，负极活性材料表面不可避免地形成SEI(solid electrolyte interface，固体电解质界面)膜，造成活性离子不可逆消耗，由此导致二次电池的不可逆容量损失难以消除。
为了满足锂离子二次电池在高能量密度方面的需求，可采用补锂技术来增加活性锂含量，补偿锂离子二次电池首次充电过程中的活性锂损失。目前主要的、且技术成熟度较高的是负极补锂工艺，例如通过锂粉或锂箔在负极极片表面覆盖一层锂金属层，这些锂能在锂离子二次电池制造和全生命周期使用过程中逐步释放并补偿锂离子二次电池内部副反应导致的活性锂损失，从而极大地避免锂离子二次电池的容量下降。
相关技术中，多是在负极集流体表面设置锂源(例如锂金属层)，以实现对锂离子二次电池的补锂。然而，发明人发现：将锂源设置于负极集流体表面，在向二次电池注入电解液后，锂源中的锂将会在电势差的作用下形成Li +，这些Li +会优先嵌入距离最近的负极膜层。大量的Li +嵌入较小区域的负极膜层，可能会导致局部Li +过量，难以全部嵌 入，从而诱发负极极片表面析锂、循环性能下降、电池短路等风险。
此外，经深入研究，发明人还发现：在锂离子二次电池中，负极膜层可以包括隔着隔离膜与正极膜层相对设置的第一负极膜层和未与正极膜层相对设置的第二负极膜层。在二次电池充电时，从正极膜层脱出的Li +将在电势差的驱动下通过隔离膜后优先嵌入第一负极膜层，因此，第一负极膜层也可以称为反应区负极膜层。除了第一负极膜层或反应区负极膜层，负极膜层还可以包括第二负极膜层，即未与正极膜层相对设置的负极膜层。第二负极膜层也可以称为非反应区负极膜层。在锂离子二次电池充电时，正极脱出的Li +嵌入反应区后，反应区的电位下降，与非反应区形成电位差，此时，反应区的Li +会以缓慢的速度向非反应区扩散和嵌入。嵌入非反应区的Li +在放电过程中很难回到正极，这也会造成活性锂的不可逆损失，从而降低了锂离子二次电池的首次库伦效率、循环性能和存储性能。目前，鲜有针对这一技术问题的相关解决方案。
鉴于此，发明人经深入思考，提供了一种二次电池、含有该二次电池的电池模块、电池包及用电装置。
二次电池
本申请第一方面提供二次电池，其包括：正极极片、隔离膜和负极极片。正极极片上设置有正极膜层，负极极片包括第一负极膜层和第二负极膜层，其中，第一负极膜层隔着隔离膜与正极膜层相对设置。第二负极膜层包括不与所述正极膜层相对设置的负极膜层。第二负极膜层包括中心区域和围绕所述中心区域的外周区域，其中，第二负极膜层的外周区域中的至少一部分中存储有用于向第一负极膜层补充锂的锂源。
本申请中，第一负极膜层也可以称为反应区负极膜层，第二负极膜层也可以称为非反应区负极膜层。本申请对第一负极膜层和第二负极膜层在二次电池中的位置不作限制，其可以根据二次电池的结构确定。本申请对二次电池的结构不作限制。
作为一个示例，本申请的二次电池可以包括具有叠片式结构的电极组件。如图1所示，电极组件10包括正极极片11、隔离膜12和负极极片13。位于电极组件最外侧的负极极片13包括朝向电极组件10外侧的第一表面13a和朝向电极组件10内侧的第二表面13b。如图1所示，电极组件10包括两个位于最外侧的负极极片13，可以在其中之一或两者的第一表面13a上设置负极膜层(图中未示出)。在第一表面13a上设置的负极膜层是根据本申请实施方式的第二负极膜层的实施例。在电极组件10中的负极极片的其它表面上(包括表面13b)也设置有负极膜层，其隔着隔离膜12与正极极片11上设置的正极膜层(图中未示出)相对。这样的负极膜层是根据本申请实施方式的第一负极膜层的实施例。
作为另一个示例，本申请的二次电池可以包括具有卷绕式结构的电极组件。如图2所示，电极组件10包括正极极片11、隔离膜12和负极极片13。负极极片13可以在沿卷绕方向的起始区域(电极组件的中心空卷区域)以及沿卷绕方向的收尾区域(电极组件的外周收尾区域)设置负极膜层131。容易理解的，电极组件10中，设置在起始区域中的负极膜层131和/或设置在收尾区域的负极膜层131是根据本申请实施方式的第二负极膜层的实施例。在负极极片13的其它区域中，可以包括与正极极片11上的正极膜层(图中未示出)相对设置的负极膜层(图中未示出)，这样的负极膜层是根据本申请实施方式的第一负极膜层的实施例。
本申请中，中心区域、外周区域具有本领域公知的含义。例如，中心区域可以表示相对于外周区域更靠近第二负极膜层的几何中心的区域；外周区域可以表示相对于中心区域更靠近第二负极膜层的边缘的区域。本申请对中心区域和外周区域的形状不作限制，作为示例，中心区域可以为矩形、正方形、平行四边形、圆形、椭圆形、多边形或不规则形状。
本申请的锂源可以是由补锂剂置于第二负极膜层的外周区域表面而形成的锂源。其中，补锂剂可以为本领域公知的可用于负极的补锂剂，例如，可以包括但不限于金属锂箔、锂粉、硅锂合金、铝锂合金、镁锂合金、锡锂合金及其它形式的锂合金。锂源可包括由补锂剂与负极膜层中的负极活性材料反应形成的富锂化合物以及可能存在的未反应的补锂剂。作为示例，锂源可包括补锂剂、补锂剂与碳负极材料反应生成的LiC x(x≥6)、补锂剂与硅负极材料反应生成的Li ySi z(y＞0)等中的至少一者。在一些实施方式中，可以在第二负极膜层的外周区域的至少部分表面覆盖锂金属，从而形成补锂层，再向二次电池注入电解液，从而使补锂层与负极膜层中的负极活性材料反应，以形成本申请的锂源。锂金属对氢的标准电极电位是-3.05V，未嵌锂的负极活性材料(例如石墨、硅碳复合材料等)对氢的标准电位为0V左右。向二次电池注入电解液后，由于锂金属与负极膜层直接接触，可以形成回路，此时，相当于以锂金属为负极、负极膜层为正极的电池直接发生短路，至少部分锂金属失去电子，以Li +的形式嵌入负极膜层，从而实现在第二负极膜层的外周区域存储本申请的锂源。
虽然机理尚不明确，发明人意外地发现，在第二负极膜层的外周区域存储有用于向第一负极膜层补充锂的锂源，能够有效提升二次电池的首次库伦效率、存储性能和循环性能。
并非意在受限于任何理论或解释，本申请的第二负极膜层的外周区域中存储有用于向第一负极膜层补充锂的锂源，存储有该锂源的区域能够具有低电势。由此，在锂离子二次电池充电时，正极脱出的Li +嵌入第一负极膜层后，第一负极膜层的电位虽有有所下降，但是第一负极膜层与第二负极膜层能够保持较小的电势差，从而能够防止Li +向第二负极膜层扩散和嵌入。在锂离子二次电池放电的过程中，第一负极膜层的电势会逐渐升高，当第一负极膜层的电势远高于第二负极膜层的电势时，锂源会在第一负极膜层和第二负极膜层之间的电势差的驱动下形成Li +，并以缓慢的速度向第一负极膜层扩散。由此，能够补充锂离子二次电池充放电循环中损失的活性锂，从而显著提升二次电池的首次库伦效率、循环性能和存储性能。进一步地，本申请的锂源存储于第二负极膜层的外周区域，相较于中心区域，外周区域与第一负极膜层之间的距离更短。当锂源在电势差的驱动下形成Li +时，Li +能够具有更短的扩散路径，从而能够避免Li +在扩散过程中发生损失，进而显著提升补锂的效率和锂源的利用率。
在一些实施方式中，所述第二负极膜层的等效圆面积直径R与所述外周区域的等效圆面积直径R 1可满足：0.257R≤R 1≤0.9434R，0.3R≤R 1≤0.85R，0.35R≤R 1≤0.8R，0.4R≤R 1≤0.75R，0.45R≤R 1≤0.7R，0.5R≤R 1≤0.65R或0.55R≤R 1≤0.6R。
本申请中，等效圆面积直径可以表示与所限定区域具有相等面积的圆所对应的直径。例如，第二负极膜层的等效圆面积直径表示：与第二负极膜层具有相等面积的圆所对应的直径；外周区域的等效圆面积直径表示：与外周区域具有相等面积的圆所对应的 直径。
并非意在受限于任何理论或解释，第二负极膜层的等效圆面积直径与外周区域的等效圆面积直径满足上述条件，能够允许本申请的锂源具有合适的存储空间，从而能够通过锂源向二次电池补充适量的活性锂离子。此外，第二负极膜层的等效圆面积直径与外周区域的等效圆面积直径满足上述条件，能够使得锂源在电势差的驱动下形成的Li +具有合适的扩散路径，从而能够提升补锂的效率和锂源的利用率。由此，能够进一步提升二次电池的首次库伦效率、循环性能和存储性能。
在一些实施方式中，所述外周区域具有第一部分以及围绕所述第一部分的第二部分，所述第二部分的等效圆面积直径R 2可满足：0＜R 2＜R 1，可选地，0＜R 2＜0.5R 1，更可选地，0＜R 2＜0.1R 1，其中，所述锂源存储于所述第一部分。
本申请对第一部分以及第二部分的形状不作限制。作为示例，第一部分可以为圆环形、椭圆环形、空心矩形等环形或具有不规则形状。第一部分中的至少一部分中存储有用于向第一负极膜层补充锂的锂源。
并非意在受限于任何理论或解释，发明人发现：补锂区距离第二负极膜层的边缘越远，锂源脱出的Li +的扩散路径越长，相应地，补锂效率也越低。但是，第二负极膜层的边缘容易受到外力的作用，因此，位于第二负极膜层边缘的锂源可能会脱离负极极片，从而造成锂源的损失。将外周区域分为第一部分以及位于第二负极膜层边缘的第二部分，使锂源存储于第一部分，能够使得锂源稳定地存在于第二负极膜层中，从而降低锂源损失的风险。由此，能够提升对二次电池进行补锂的效率。
在一些实施方式中，所述第一部分为环形，所述第一部分的外轮廓线与所述第二负极膜层边缘的最小距离d 1、所述第二负极膜层的宽度d 0可满足：0＜d 1≤d 0/6。
该实施方式中对环形不作限制，其具体可以包括由闭合的外轮廓线和闭合的内轮廓线围合而成的图形。作为示例，第一部分可以为圆环形、椭圆环形、空心矩形等环形或具有不规则形状。
图3是本申请的二次电池的一实施方式中，第二负极膜层的示意图。该示例性的第二负极膜层130包括中心区域1310、外周区域1320。其中，外周区域1320由呈椭圆环形的第一部分1321以及第二部分1322组成。第一部分1321由外轮廓线1321a和内轮廓线1321b围合而成。第一部分中1321的至少一部分中存储有用于向第一负极膜层补充锂的锂源。所述第一部分的外轮廓线1321a与所述第二负极膜层边缘的最小距离d 1可以如图3中所示。
图4是本申请的二次电池的另一实施方式中，第二负极膜层的示意图。该示例性的第二负极膜层130包括中心区域1310、外周区域1320。其中，外周区域1320由呈空心矩形的第一部分1321以及第二部分1322组成。第一部分1321由外轮廓线1321a和内轮廓线1321b围合而成。第一部分中1321的至少一部分中存储有用于向第一负极膜层补充锂的锂源。所述第一部分的外轮廓线1321a与所述第二负极膜层130边缘的最小距离d 1可以如图4中所示。
并非意在受限于任何理论或解释，第一部分的外轮廓线与所述第二负极膜层边缘的最小距离d 1在上述合适的范围内，能够在保证锂源脱出的Li +具有合适长度的扩散路径的同时，有效降低锂源脱落的风险。由此，能够提升对二次电池进行补锂的效率，从而 提升二次电池的首次库伦效率、循环性能和存储性能。
在一些实施方式中，所述二次电池可满足：d 3≤d 2≤d 0/6，其中，d 2表示所述外轮廓线与所述第二负极膜层的长度方向上的边的最小距离，d 3表示所述外轮廓线与所述第二负极膜层的宽度方向上的边的最小距离。
在一些实施方式中，如图4所示，d 2表示外轮廓线1321a与第二负极膜层130的长度方向上的边的最小距离，d 3表示所述外轮廓线与第二负极膜层130的宽度方向上的边的最小距离。其中，d 3≤d 2≤d 0/6，此时，d 3＝d 1。
并非意在受限于任何理论或解释，第一部分的外轮廓线与第二负极膜层的长度方向上的边以及第二负极膜层的宽度方向上的边之间均具有一定的距离，且该距离在较小的范围内，能够在保证锂源脱出的Li +具有合适长度的扩散路径的同时，有效降低锂源脱落的风险。由此，能够提升对二次电池进行补锂的效率，从而提升二次电池的首次库伦效率、循环性能和存储性能。
在一些实施方式中，如图4所示，所述第一部分1321为空心矩形，所述第一部分1321可满足：0＜d 4≤d 0/3，和/或0＜d 5≤l 0/3。其中d 4表示所述第一部分1321沿所述第二负极膜层130宽度方向上的宽度；d 5表示所述第一部分1321所述第二负极膜层130长度方向上的宽度，l 0表示所述第二负极膜层130的长度。
在一些实施方式中，第一部分可以为空心矩形，且第一部分的外轮廓线与内轮廓线的几何中心可以不重合。此时，第一部分沿第二负极膜层宽度方向上具有两个不相等的宽度d 41和d 42，d 41和d 42可以均满足大于0且小于等于d 0/3；第一部分沿第二负极膜层长度方向上具有两个不相等的宽度d 51和d 52，d 51和d 52可以均满足大于0且小于等于l 0/3。
并非意在受限于任何理论或解释，第一部分具有合适的宽度，能够使得第一部分具有合适的面积，从而能够存储适量的锂源。第一部分具有合适的宽度，还能够相应地允许第二部分和中心区域具有合适的面积。因此，锂源存储于第一部分时，能够与第二负极膜层的中心和/或第二负极膜层的边缘具有合适的距离。由此，本申请的第二负极膜层中能够存储合适的活性锂，该活性锂不仅不易从第二负极膜层中脱落，在二次电池需要补充锂离子时，该活性锂还能够通过较短的路径扩散并嵌入第一负极膜层。因此，本申请的二次电池能够具备高首次库伦效率以及良好的循环性能和存储性能。
在一些实施方式中，所述二次电池可满足：1mm≤d 2≤5mm。
可选地，(l 0-10mm)≤l 1≤(l 0-2mm)，l 1表示所述外轮廓线的长度。
可选地，10mm≤d 4≤d 0/5。
可选地，1mm≤d 3≤5mm。
可选地，(d 0-10mm)≤l 2≤(d 0-2mm)，l 2表示所述外轮廓线的宽度。
可选地，10mm≤d 5≤d 4。
当二次电池满足上述条件中的至少一者时，有利于第二负极膜层提供足够的用于存储锂源的空间，并且能够使得锂源在第二负极膜层中的分布位置适当。由此，锂源不仅不易从第二负极膜层中脱落，在二次电池需要补充锂离子时，锂源提供的Li +还能够通过较短的路径扩散并嵌入第一负极膜层。因此，本申请的二次电池能够具备高首次库伦效率以及良好的循环性能和存储性能。
可选地，所述锂源呈环形分布于所述第一部分。
并非意在受限于任何理论或解释，锂源呈环形分布于第一部分时，能够使得第二负极膜层具有合适的电势。由此，第一负极膜层中的Li +不易嵌入第二负极膜层中，从而进一步减少了活性锂的损失。因此，本申请的二次电池能够具备高首次库伦效率、良好的循环性能和存储性能。
在一些实施方式中，存储有所述锂源的第二负极膜层的面积S 1与所述外周区域的面积S 2可满足：10％≤S 1/S 2≤100％。可选地，80％≤S 1/S 2＜100％，更可选地，90％≤S 1/S 2＜100％。
并非意在受限于任何理论或解释，S 1与S 2的比值在上述合适的范围内，能够使得第二负极膜层中存储的锂源的量适当。锂源的量适当，一方面能够使得第二负极膜层具有合适的电势，从而减少第一负极膜层中的Li +脱出并嵌入第二负极膜层；另一方面能够提供在足够的活性锂离子的情况下，避免锂源过剩。由此，能够减少二次电池在循环过程中损失的Li +、提升补锂效率、控制补锂的成本。因此，本申请的二次电池能够具备高首次库伦效率、良好的循环性能和存储性能、低成本。
在一些实施方式中，锂源可包括锂金属、锂合金、锂金属与负极活性材料的复合物、铝合金与负极活性材料的复合物中的至少一者，可选为锂金属和/或锂金属与负极活性材料的复合物。可选地，所述锂合金包括硅锂合金、铝锂合金、镁锂合金、锡锂合金中的至少一者。
并非意在受限于任何理论或解释，发明人发现：无论是金属锂箔、锂粉、硅锂合金、铝锂合金、镁锂合金、锡锂合金及其它形式的锂合金都可以作为补锂层，并与第二负极膜层中的活性物质相互作用形成本申请的锂源。其中，锂金属(包括金属锂箔、锂粉等)的克容量高，且与负极活性材料反应后无杂质产生，因此，锂金属形成的锂源能够具有更高的补锂效率。进一步地，金属锂箔具有良好的加工性能，通过在第二负极膜层表面贴敷金属锂箔，并使金属锂箔与负极活性材料反应形成锂源，能够在提升补锂效率的同时，使得本申请的二次电池具备高产能。
在一些实施方式中，所述二次电池可满足：20％C 0≤C Li≤120％C 0，其中，C 0表示所述第二负极膜层的单位面积活性物质容量，C Li表示所述锂源的单位面积容量。可选地，90％C 0≤C Li≤120％C 0，
本申请中，第二负极膜层的单位面积活性物质容量C 0可以表示：单位面积的第二负极膜层中的负极活性材料的容量。通常情况下，C 0可以等于第一负极膜层的单位面积活性物质容量。锂源的单位面积容量C Li可以表示：单位面积的、存储有锂源的第二负极膜层所包含的锂源的容量。
发明人意外地发现，C 0和C Li满足上述条件时，二次电池能够兼具高首次库伦效率、良好的循环性能、良好的存储性能以及良好的安全性能。并非意在受限于任何理论或解释，当C Li较小时，存储有锂源的区域具有较高的电势，在二次电池放电时，第一膜层的需要达到较高的电势才能够与第二负极膜层形成足够的电势差，以驱动锂源脱出Li +，并以缓慢的速度向第一负极膜层扩散。当C Li较大时，存储有锂源的区域具有较低的电势，极易与第二负极膜层形成足够的电势差，并使得锂源快速地脱出Li +。当Li +脱出的速度过快时，可能会导致Li +难以及时地嵌入第一负极膜层，从而造成负极极片局部析 锂的风险。在常规的电池容量设计下，C 0和C Li满足上述条件时，能够使得锂源脱出Li +的速度处于更合适的范围内，从而兼顾补锂效率和二次电池的安全性能。
在一些实施方式中，所述二次电池具有卷绕结构，所述第二负极膜层包括沿卷绕方向的起始区域以及收尾区域，所述二次电池可满足：C A≥C B，C A表示位于所述起始区域的锂源的容量，C B表示位于所述收尾区域的锂源的容量。
并非意在受限于任何理论或解释，发明人发现相对于位于收尾区域的第二负极膜层，位于起始区域的第二负极膜层保留电解液的能力更好，从而更有利于锂源脱出的Li +的扩散。锂源的总容量一定时，起始区域的锂源容量更高，有利于提升补锂效率和锂源的利用率。
在一些实施方式中，锂源与所述第一负极膜层的最小距离d 7可满足：0＜d 7≤10mm。
并非意在受限于任何理论或解释，锂源与第一负极膜层的最小距离在上述合适的范围内，能够使得锂源脱出的Li +具有更短的扩散路径，从而提高补锂效率和锂源的利用率。
在一些实施方式中，所述中心区域的表面覆盖有阻隔层，所述阻隔层包括阻隔膜和/或阻隔涂层。本申请对阻隔膜的材质不作限制，只要能够阻隔电解液与中心区域接触即可，其可以为具有单面粘性或双面粘性的薄膜，优选为单面粘性的薄膜。可选地，阻隔膜的至少一个表面与中心区域表面的粘结力可大于20N/m，更可选地，阻隔膜与中心区域的表面的粘结力大于第二负极膜层的内聚力。
可选地，所述阻隔膜选自流延聚丙烯薄膜、单向拉伸聚丙烯膜、双向拉伸聚丙烯膜、聚乙烯膜、聚酯纤维膜、聚氯乙烯膜中的至少一者。所述阻隔涂层包括聚偏氟乙烯、聚四氟乙烯、聚苯丙酰胺、聚酰胺、聚酰亚胺、聚甲基丙烯酸甲酯、聚氨酯、聚苯乙烯、聚丙烯酸、聚丙烯酰胺、聚丙烯腈或上述物质的共聚物中的至少一者。
并非意在受限于任何理论或解释，在中心区域的表面覆盖有阻隔层，能够降低电解液浸润中心区域的风险。由此，能够减少二次电池中的活性Li +嵌入中心区域的负极膜层，从而进一步提升补锂效率以及锂源的利用率，进而提升二次电池的首次库伦效率、循环性能和存储性能。
可选地，所述阻隔层的厚度为6μm～40μm，更可选地，所述阻隔层的厚度为10μm～20μm。
阻隔层的厚度在合适的范围内，既能够具有良好的机械强度，从而不易破损，又能够使得负极极片的厚度在较小的范围内，从而便于负极极片的加工。
在本申请中，负极膜层的长度和宽度具有本领域公知的含义。例如，当二次电池包括具有卷绕式结构的电极组件时，负极膜层的长度可以表示负极膜层沿电极组件卷绕方向的长度，负极膜层的宽度可以表示负极膜层垂直于卷绕方向的长度。当二次电池包括具有叠片式结构的电极组件时，负极膜层的长度可以表示负极膜层较长的边的长度，负极膜层的宽度可以表示负极膜层较短的边的长度。
在本申请中，C 0可以通过对未存储有锂源的第二负极膜层进行容量测试得到。作为示例，将负极膜层的一面擦洗露出空基材，将含有一面负极膜层的极片冲切成小圆片 面积为S，利用扣式对锂半电池测试出含有负极膜层小圆片的容量C，通过公式C 0＝C/S计算出单位面积负极膜层容量C 0。
在本申请中，C Li可以通过本领域公知的方法计算得到。作为示例，锂源由贴敷于第二负极膜层的外周区域的金属锂箔形成时，可以根据锂箔的重量、理论克容量计算得到锂箔的容量C 1，再测量锂箔的面积S’，即可计算C Li。C Li可通过下式计算：C Li＝C 1/S’。
本申请的二次电池中，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且包括负极活性材料的负极膜层。例如，负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置于负极集流体的两个相对表面中的任意一者或两者上。
如之前参考图1和图2所述的，在本申请的实施例中，负极膜层包括本申请中所述的第一负极膜层和第二负极膜层。
负极活性材料的种类并不受到具体的限制，可采用本领域公知的用于二次电池的负极活性材料。作为示例，负极活性材料可包括石墨、软碳、硬碳、中间相碳微球、硅基材料、锡基材料、钛酸锂中的一种或多种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或多种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或多种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。这些负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。
在一些实施方式中，负极活性材料包括人造石墨、天然石墨、硅基材料中的一种或几种。负极活性材料选自上述种类的材料，能够使得第二负极膜层具有合适的电位，从而提升补锂效率和锂源利用率。
负极集流体的种类不受具体的限制，可根据实际需求进行选择。例如，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，负极集流体可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可选自聚丙烯(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)中的一种或多种。
在本申请的二次电池中，负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料、可选的导电剂、可选的粘剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或水，但不限于此。作为示例，导电剂可包括超导碳、炭黑(例如乙炔黑、科琴黑等)、碳点、碳纳米管、石墨烯及碳纳米纤维中一种或几种。粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸树脂、聚乙烯醇(PVA)、海藻酸钠(SA)及羧甲基壳聚糖(CMCS)中的一种或几种。其他可选助剂例如是增稠剂(如羧甲基纤维素钠CMC-Na)、PTC热敏电阻材料等。
另外，本申请的二次电池中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在一些实施方式中，本申请所述的负极极片还可以包括设置在负极集流体和 负极膜层之间的导电底涂层(例如由导电剂和粘接剂组成)。在另外一些实施方式中，本申请所述的负极极片还包括覆盖在负极膜层表面的保护层。
本申请的二次电池中，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且包括正极活性材料的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
正极活性材料的种类并不受到具体的限制，可采用本领域公知的用于二次电池的正极活性材料。例如，正极活性材料可包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物及其改性化合物中的一种或几种。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、磷酸铁锂与碳的复合材料、磷酸锰锂、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及其各自的改性化合物中的一种或几种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池正极活性材料的传统公知的材料。
负极集流体的种类不受具体的限制，可根据实际需求进行选择。例如，所述正极集流体可采用金属箔片或复合集流体(可以将金属材料设置在高分子基材上形成复合集流体)。作为示例，正极集流体可采用铝箔。
本申请的二次电池中，所述正极膜层通常包含正极活性材料以及可选的粘结剂和可选的导电剂，通常是由正极浆料涂布，并经干燥、冷压而成的。正极浆料通常是将正极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)。
作为示例，用于正极膜层的粘结剂可以包括聚偏氟乙烯(PVDF)和聚四氟乙烯(PTFE)中的一种或几种。
作为示例，用于正极膜层的导电剂可以包括超导碳、炭黑(例如，乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或几种。
本申请的二次电池对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施方式中，电解质采用电解液。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LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或几种。
在一些实施方式中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二 乙砜(ESE)中的一种或几种。
在一些实施方式中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请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，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。
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，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图5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6，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用于盖设所述开口，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。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
电池模块和电池包
根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图7是作为一个示例的电池模块4的示意图。如图7所示，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根据电池包的应用和容量进行调节。
图8和图9是作为一个示例的电池包1的示意图。如图8和图9所示，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用于盖设下箱体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。
用电装置
本申请还提供一种用电装置，所述用电装置包括本申请的二次电池、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。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
图10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。为了满足该装置对高功率和高能量密度的需求，可以采用包括本申请的二次电池的电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1～12
正极极片的制备
将正极活性材料磷酸铁锂、导电剂乙炔黑、粘结剂PVDF按质量比96:2:2进行混合，加入溶剂NMP，在真空搅拌机作用下搅拌至体系呈均一状，获得正极浆料；
将正极浆料均匀涂覆在正极集流体铝箔上，然后经过干燥，冷压、分切得到正极极片。
负极极片的制备
将负极活性材料、导电剂乙炔黑、增稠剂CMC、粘结剂SBR按质量比96.4:1:1.2:1.4进行混合，加入溶剂去离子水，在真空搅拌机作用下搅拌至体系呈均一状，获得负极浆料；
将负极浆料均匀涂覆在负极集流体铜箔上，然后经过、干燥，冷压、分切得到负极极片。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂；将充分干燥的锂盐LiPF 6溶解于所述有机溶剂中，配制成浓度为1mol/L的电解液。
隔离膜的制备
以聚乙烯膜作为隔离膜。
二次电池的制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，经加工得到叠片式电极组件；将叠片式电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得二次电池。
其中，在注入电解液之前，在负极极片的第二负极膜层的外周区域的表面贴敷补锂剂，以在注入电解液之后形成如图4所示的第二负极膜层。实施例8中，补锂剂非连续地贴敷于外周区域，以形成非连续分布的锂源。其余实施例中，补锂剂连续地贴敷于外周区域，以形成连续分布的锂源。
实施例1～12中，补锂d 0＝100mm，l 0＝150mm，负极活性材料、补锂剂、R 1/R、R 2/R 1、d 2、d 3、d 4、d 5、1 1、l 2、S 1/S 2、C Li/C 0分别如表1-1中所示。
实施例13～18
根据实施例1～12的制备过程，制备实施例13～18的正极极片、负极极片、电解液和隔离膜；
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，经卷绕得到卷绕式电极组件；将卷绕式电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得二次电池。
其中，在注入电解液之前，在位于起始区域的第二负极膜层(记为A面)的外周区域，和/或位于收尾区域的第二负极膜层(记为B面)的外周区域的表面贴敷补锂剂，以在注入电解液之后，分别于A面和/或B面形成如图4所示的第二负极膜层。
实施例19～20
基于实施例13～18的制备过程，制备实施例19～20的正极极片、负极极片、电解液、隔离膜及二次电池。
其中，实施例19的A面的中心区域贴敷有厚度为20μm的聚乙烯隔离膜，实施例20的A面的中心区域涂覆有厚度为20μm微米的聚四氟乙烯涂料。
实施例13～20中，A面的d 0＝100mm，A面的l 0＝150mm，B面的d 0＝100mm，B面的l 0＝165mm。A面的R 1/R、R 2/R 1、d 2、d 3、d 4、d 5、1 1、l 2、S 1/S 2、C Li/C 0以及B面的R 1/R、R 2/R 1、d 2、d 3、d 4、d 5、1 1、l 2、S 1/S 2、C Li/C 0分别如表1中所示。
实施例13～20中，基于锂源的总容量，A面存储的锂源的容量占比C A、B面存储的锂源的容量占比C B、负极活性材料、补锂剂、d 7分别如表1-2中所示。
对比例1～2
基于实施例1～12的制备过程，根据表1-1所示制备对比例1～2的正极极片、负极极片、电解液、隔离膜及二次电池，其中，对比例1～2的第二负极膜层的外周区域表面未贴敷补锂剂。
对比例3～4
基于实施例13～18的制备过程，根据表1-2所示制备对比例3～4的正极极片、负极极片、电解液、隔离膜及二次电池，其中，对比例3～4的第二负极膜层的外周区域表面未贴敷补锂剂。
Figure PCTCN2022097944-appb-000001
Figure PCTCN2022097944-appb-000002
测试部分
1)二次电池的首次库伦效率测试
在45℃下以0.02C倍率充电10h所测得的容量标记为C0，然后在25℃下以0.33C倍率充电至3.65V，3.65V恒压充电至0.05C所测得的容量标记为C1，最后以0.33C放电至2.5V所测得的容量标记为D0，二次电池的首次库伦效率＝D0/(C0+C1)×100％。
2)二次电池的存储性能测试
在25℃环境下执行以下步骤：
静置5分钟；以0.33D0放电至2.5V；静置5分钟；以0.33D0充电至3.65V，3.65V恒压充电至0.05D0；静置5分钟；以0.33D0放电至2.5V记录此时的容量为C dn，n表示存储的天数；静置5分钟；以0.33D0充电电至3.65V；3.65V恒压充电至0.05D0(满充状态)；将二次电池转移至45℃环境下存储。
每存储30天在25℃的环境下按以上步骤采集一次数据，存储180天采集最后一次数据。二次电池的可逆容量保持率＝C d180/C d0*100％。
3)二次电池的循环性能测试
在25℃环境下执以下步骤：
静置5分钟；以0.33D0放电至2.5V；静置5分钟；以0.33D0充电至3.65V，3.65V恒压充电至0.05C；静置5分钟；以0.33C放电至2.5V，记录此时的容量记为C’0。
将二次电池静置5分钟后，转移至45℃环境下，按照以下步骤进行充放电循环：静置20分钟，以1D0充电至3.65V，3.65V恒压充电至0.05D0；静置5分钟；以1D0放电至2.5V；静置5分钟。记录每圈的放电容量C m，m表示循环圈数，直至C m/C’0*100＝80％，记录此时m的值，作为二次电池的循环寿命：
实施例1～20及对比例1～4的测试结果分别如表2所示。
表2-1
Figure PCTCN2022097944-appb-000003
表2-2
Figure PCTCN2022097944-appb-000004
表2-3
序号 首次库伦效率 可逆容量保持率 循环寿命/圈
实施例13 91.50％ 90.40％ 2151
实施例14 92.10％ 91.00％ 2314
实施例15 92.00％ 90.90％ 2306
实施例17 91.70％ 90.10％ 2153
实施例18 92.00％ 90.60％ 2274
实施例19 92.10％ 91.30％ 2418
实施例20 92.00％ 91.10％ 2369
对比例3 91.20％ 89.10％ 2012
表2-4
序号 首次库伦效率 可逆容量保持率 循环寿命/圈
实施例16 88.40％ 86.80％ 851
对比例4 87.30％ 84.70％ 709
由表1和表2可知，在负极极片的第二负极膜层的外周区域设置锂源，能够显著提升二次电池的首次库伦效率，并使得二次电池保持较高的可逆容量保持率和较长的循环寿命。
具体地，由表1-1、表2-1、2-2可知，相较于对比例1、2，实施例1～12在具有叠片式结构的二次电池的第二负极膜层的外周区域设置锂源，二次电池的首次库伦效率能够提升0.3％以上、可逆容量保持率能够提升0.7％以上、循环寿命能够提升79圈以上。可见，在第二负极膜层的外周区域设置锂源，能够实现对二次电池的高效补锂，从而有效提升二次电池的首次库伦效率和长期循环性能。由实施例1～7可知，在第二负极膜层的外周区域设置锂源，锂源的面积适当、且锂源与第二负极膜层的边缘保持合适的距离，能够提升补锂效率和锂源的利用率。由实施例8可知，相较于非连续分布的锂源，连续分布的锂源能够具有更高的补锂效率和锂源利用率。由实施例9、10可知，锂源存储于第二负极膜层的外周区域，且C Li/C 0在20％～120％的范围内，均能够有效提升二次电池的首次库伦效率和长期循环性能，尤其是当C Li/C 0在90％～120％的范围内时，二次电池的首次库伦效率和长期循环性能的提升更为明显。由实施例12可知，由锂合金形成的锂源也能够具有高补锂效率，但是相对来说，锂金属形成的锂源在补锂方面具有更大的优势。
由表1-2、表2-3、2-4可知，相较于对比例3、4，实施例13～20在具有卷绕式结构的二次电池的第二负极膜层的外周区域设置锂源，二次电池的首次库伦效率能够提升0.3％以上、可逆容量保持率能够提升1％以上、循环寿命能够提升139圈以上。可见，在第二负极膜层的外周区域设置锂源，能够实现对二次电池的高效补锂，从而有效提升二次电池的首次库伦效率和长期循环性能。由实施例13～15可知，在第二负极膜层的外周区域设置锂源，锂源的面积适当、且锂源与第二负极膜层的边缘保持合适的距离，能够提升补锂效率和锂源的利用率。由实施例17、18可知，当二次电池具有卷绕结构时，相较于在卷绕的收尾区域设置锂源，在卷绕的起始区域设置锂源能够具有更高的补锂效率。此外，由实施例19、20可知，在第二负极膜层的中心区域设置阻隔层，能够有效降低电解液对中心区域负极膜层的浸润，从而提升二次电池的首次库伦效率、可逆容量保持率和循环寿命。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可容易想到各种等效的修改或替换，这些修改或替换都应被涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (16)

  1. 一种二次电池，包括：
    正极极片，包括正极膜层；
    隔离膜；
    负极极片，包括
    第一负极膜层，所述第一负极膜层隔着所述隔离膜与所述正极膜层相对设置，和
    第二负极膜层，所述第二负极膜层包括不与所述正极膜层相对设置的负极膜层，所述第二负极膜层包括中心区域和围绕所述中心区域的外周区域，其中，所述第二负极膜层的所述外周区域中的至少一部分中存储有用于向所述第一负极膜层补充锂的锂源。
  2. 根据权利要求1所述的二次电池，其中，所述第二负极膜层的等效圆面积直径R与所述外周区域的等效圆面积直径R 1满足：0.257R≤R 1≤0.9434R。
  3. 根据权利要求1或2所述的二次电池，其中，所述外周区域具有第一部分以及围绕所述第一部分的第二部分，所述第二部分的等效圆面积直径R 2满足：0＜R 2＜R 1，可选地，0＜R 2＜0.5R 1，更可选地，0＜R 2＜0.1R 1，
    其中，所述锂源存储于所述第一部分。
  4. 根据权利要求3所述的二次电池，其中，所述第一部分为环形，所述第一部分的外轮廓线与所述第二负极膜层边缘的最小距离d 1、所述第二负极膜层的宽度d 0满足：0＜d 1≤d 0/6。
  5. 根据权利要求4所述的二次电池，其满足：d 3≤d 2≤d 0/6，其中，d 2表示所述外轮廓线与所述第二负极膜层的长度方向上的边的最小距离，d 3表示所述外轮廓线与所述第二负极膜层的宽度方向上的边的最小距离。
  6. 根据权利要求4或5所述的二次电池，其中，所述第一部分为空心矩形，所述第一部分满足：
    0＜d 4≤d 0/3，d 4表示所述第一部分沿所述第二负极膜层宽度方向上的宽度；和/或
    0＜d 5≤l 0/3，d 5表示所述第一部分沿所述第二负极膜层长度方向上的宽度，l 0表示所述第二负极膜层的长度。
  7. 根据权利要求5或6所述的二次电池，其中，所述二次电池满足如下至少一者：
    (1)1mm≤d 2≤5mm；
    (2)(l 0-10mm)≤l 1≤(l 0-2mm)，l 1表示所述外轮廓线的长度；
    (3)10mm≤d 4≤d 0/5；
    (4)1mm≤d 3≤5mm；
    (5)(d 0-10mm)≤l 2≤(d 0-2mm)，l 2表示所述外轮廓线的宽度；
    (6)10mm≤d 5≤d 4；
    (7)所述锂源呈环形分布于所述第一部分。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，存储有所述锂源的第二负极膜层的面积S 1与所述外周区域的面积S 2满足：10％≤S 1/S 2≤100％，可选为80％≤S 1/S 2＜100％，更可选为90％≤S 1/S 2＜100％。
  9. 根据权利要求1-8中任一项所述的二次电池，其中，所述锂源包括锂金属、锂合金、锂金属与负极活性材料的复合物、铝合金与负极活性材料的复合物中的至少一者，可选地，所述锂合金包括硅锂合金、铝锂合金、镁锂合金、锡锂合金中的至少一者。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，所述二次电池满足：20％C 0≤C Li≤120％C 0，可选地，90％C 0≤C Li≤120％C 0，其中，C 0表示所述第二负极膜层的单位面积活性物质容量，C Li表示所述锂源的单位面积容量。
  11. 根据权利要求1-10中任一项所述的二次电池，其中，所述二次电池具有卷绕结构，所述第二负极膜层包括沿卷绕方向的起始区域以及收尾区域，所述二次电池满足：C A≥C B，C A表示位于所述起始区域的锂源的容量，C B表示位于所述收尾区域的锂源的容量。
  12. 根据权利要求11所述的二次电池，其中，所述锂源与所述第一负极膜层的最小距离d 7满足：0＜d 7≤10mm。
  13. 根据权利要求1-12中任一项所述的二次电池，其中，所述中心区域的表面覆盖有阻隔层，所述阻隔层包括阻隔膜和/或阻隔涂层，其中，
    所述阻隔膜选自流延聚丙烯薄膜、单向拉伸聚丙烯膜、双向拉伸聚丙烯膜、聚乙烯膜、聚酯纤维膜、聚氯乙烯膜中的至少一者；
    所述阻隔涂层包括聚偏氟乙烯、聚四氟乙烯、聚苯丙酰胺、聚酰胺、聚酰亚胺、聚甲基丙烯酸甲酯、聚氨酯、聚苯乙烯、聚丙烯酸、聚丙烯酰胺、聚丙烯腈或上述物质的共聚物中的至少一者，
    可选地，所述阻隔层的厚度为6μm～40μm，更可选地，所述阻隔层的厚度为10μm～20μm。
  14. 一种电池模块，包括权利要求1-13中任一项所述的二次电池。
  15. 一种电池包，包括权利要求14所述的电池模块。
  16. 一种用电装置，包括权利要求1-13中任一项所述的二次电池、权利要求14所述的电池模块或权利要求15所述的电池包中的至少一种。
PCT/CN2022/097944 2022-06-09 2022-06-09 二次电池、含有该二次电池的电池模块、电池包及用电装置 WO2023236152A1 (zh)

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