WO2025001946A1 - 二次电池及电子装置 - Google Patents

二次电池及电子装置 Download PDF

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Publication number
WO2025001946A1
WO2025001946A1 PCT/CN2024/100143 CN2024100143W WO2025001946A1 WO 2025001946 A1 WO2025001946 A1 WO 2025001946A1 CN 2024100143 W CN2024100143 W CN 2024100143W WO 2025001946 A1 WO2025001946 A1 WO 2025001946A1
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WO
WIPO (PCT)
Prior art keywords
region
secondary battery
pole piece
thickness
active material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2024/100143
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English (en)
French (fr)
Inventor
闫东阳
江南
曾巧
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ningde Amperex Technology Ltd
Original Assignee
Ningde Amperex Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ningde Amperex Technology Ltd filed Critical Ningde Amperex Technology Ltd
Priority to EP24830592.2A priority Critical patent/EP4738504A1/en
Publication of WO2025001946A1 publication Critical patent/WO2025001946A1/zh
Priority to US19/433,375 priority patent/US20260121181A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of energy storage technology, and in particular to a secondary battery and an electronic device having the secondary battery.
  • secondary batteries eg, lithium-ion secondary batteries
  • secondary batteries may experience thermal runaway when overcharged, reducing the reliability and service life of the secondary batteries.
  • the present application also provides an electronic device having the secondary battery.
  • the present application provides a secondary battery, comprising a shell, an electrode assembly disposed in the shell, and a first conductive plate.
  • the electrode assembly is a laminated structure, comprising a first pole piece, an isolation membrane, and a second pole piece stacked in sequence in a first direction.
  • the first conductive plate is connected to the first pole piece.
  • the first conductive plate extends from the shell in a second direction perpendicular to the first direction.
  • the first pole piece includes a first outer pole piece, which is the outermost layer of the electrode assembly. When viewed from a third direction perpendicular to both the first and second directions, the first outer pole piece includes a first region and a second region connected in the second direction.
  • the first region When viewed from the third direction, the first region includes a first end connected to the second region and a second end disposed opposite to the first end in the second direction, the first region extends from the first end away from the second direction, and the second end is farther away from the second pole piece in the first direction than the first end.
  • the present application sets the first region to deviate from the second direction and extend.
  • the first region or the second pole piece corresponding to the first region can be used as a sacrificial position during overcharging to preferentially deposit lithium, thereby reducing the probability or degree of lithium deposition at other positions, and is also beneficial to reduce the possibility of contact short circuit caused by the deposited lithium dendrites piercing the isolation membrane, thereby reducing the occurrence of thermal runaway.
  • the contact interface of the adjacent first outer pole piece, isolation membrane and second pole piece can be stretched open by the action of the gas, which is beneficial to further reduce the possibility of contact short circuit caused by lithium dendrites piercing the isolation membrane, and is also beneficial to timely dissipation of heat in the electrode assembly. Therefore, the present application can improve the overcharge resistance of the secondary battery, thereby improving reliability and service life.
  • the angle ⁇ between the line connecting the first end and the second end and the second direction satisfies: 1° ⁇ 12°.
  • the influence of the first region on the energy density and appearance smoothness of the secondary battery is reduced, the possibility of the active material in the first region falling off easily and causing a short circuit is reduced, and the possibility of an increase in active materials in the first region that are difficult to play a capacity role is reduced.
  • 3° ⁇ 10° thereby further allowing lithium to be preferentially deposited in the first region or the second electrode corresponding to the first region when the secondary battery is overcharged, and reducing the possibility of the deposited lithium dendrites piercing the isolation membrane and causing a contact short circuit; moreover, it further reduces the impact of the first region on the energy density and appearance smoothness of the secondary battery, the possibility of active materials in the first region easily falling off and causing a short circuit, and the possibility of an increase in active materials in the first region that are difficult to play a capacity role.
  • the length of the first region extending from the first end to the second end is the first length
  • the length of the second region in the second direction is the second length
  • the ratio of the second length to the first length is greater than or equal to 7 and less than or equal to 29.
  • the ratio of the second length to the first length is greater than or equal to 11 and less than or equal to 19, thereby further reducing the impact of the first region on the energy density and appearance smoothness of the secondary battery, further reducing the possibility of an increase in active materials in the first region that are difficult to play a capacity role, and further reducing the possibility of failing to significantly reduce the probability or degree of lithium deposition in other locations during overcharging.
  • the first region in the second direction, is farther away from the first conductive plate than the second region, thereby reducing the possibility that the first electrode ear connected to the first conductive plate enters the space between the first region and the second electrode sheet adjacent to the first outer electrode sheet when the electrode assembly moves in the shell along the second direction, thereby causing a contact short circuit.
  • the first region in the second direction, is closer to the first conductive plate than the second region. Therefore, when the secondary battery is overcharged, the gas generated near the first region is released into the space of the housing for accommodating the first conductive plate and the first electrode connected to the first conductive plate, thereby reducing the possibility of excessive gas accumulation and causing the first region to further deviate from the second direction.
  • the first direction has a first side from the second pole piece toward the first outer pole piece.
  • the shell is a packaging bag and includes a main body for accommodating the electrode assembly and a packaging portion connected to the main body, and the first conductive plate extends from the packaging portion to the shell.
  • the main body includes a first end face connected to the packaging portion. When viewed from a third direction, the first end face extends from the packaging portion to the first side. When viewed from the third direction, the first area extends from the first end to the first side.
  • the first area of the first outer pole piece is at least partially placed in a recess of the shell formed by the extension of the first end face to the first side, thereby facilitating the reduction of friction on the first outer pole piece when the shell is covered from the other side, thereby reducing the possibility of deformation of the first outer pole piece under friction.
  • the first direction also has a second side opposite to the first side.
  • the shell is a packaging bag and includes a main body for accommodating the electrode assembly and a packaging part connected to the main body, and the first conductive plate extends out of the shell from the packaging part.
  • the main body includes a first end face connected to the packaging part.
  • the first end face When viewed from a third direction, the first end face includes a first part extending from the packaging part to the first side and a second part extending from the packaging part to the second side.
  • the length of the first part in the first direction is greater than the length of the second part in the first direction.
  • the first area extends from the first end to the first side.
  • the first area of the first outer pole piece is at least partially placed in the recess of the shell formed by the extension of the first part to the first side, so as to reduce the friction on the first outer pole piece when the shell is covered from the other side, thereby reducing the possibility of deformation of the first outer pole piece under friction.
  • the shell is a packaging bag and includes a main body for accommodating the electrode assembly and a packaging part connected to the main body.
  • the first conductive plate includes a first conductive area and a second conductive area connected to each other.
  • the first conductive area is arranged in the packaging part and extends from the packaging part to the shell.
  • the second conductive area is electrically connected to the first pole piece.
  • the second conductive area includes a first end connected to the first conductive area, and the second conductive area extends from the first end to the first side, so as to reduce the friction of the first outer pole piece when the shell is closed, thereby reducing the possibility of deformation of the first outer pole piece under friction.
  • the first outer pole piece includes a first current collector and a first active material layer stacked in a first direction.
  • the first current collector includes a first surface facing the second pole piece and a second surface opposite to the first surface.
  • the first active material layer is provided on the first surface, and no active material is provided on the second surface. Therefore, the waste of energy density can be reduced.
  • the first pole piece also includes a first inner pole piece, and the first inner pole piece is located on the inner side of the first outer pole piece.
  • the first inner pole piece includes a second current collector. In the first direction, the thickness of the first current collector is the first thickness, the thickness of the second current collector is the second thickness, and the ratio of the first thickness to the second thickness is greater than or equal to 1.2 and less than or equal to 2.5. Therefore, the first outer pole piece located in the outermost layer has a higher strength, so that a protective layer can be formed to reduce the possibility of damage to the electrode assembly during mechanical abuse.
  • the first thickness is larger than the second thickness, which is also conducive to reducing the possibility that the first current collector is prone to curling and warping due to inconsistent tension on the opposite sides of the single-sided coated first current collector.
  • the secondary battery further includes a first layer disposed on the second surface.
  • the first layer includes an insulating material. The first layer is used to dissipate heat generated at the first outer electrode sheet when the secondary battery is overcharged, reduce the temperature of the electrode assembly, and improve the overcharge resistance of the secondary battery.
  • the thickness of the first current collector is defined as the first thickness
  • the thickness of the first layer is defined as the third thickness
  • the third thickness is less than twice the first thickness. Therefore, the influence of the first layer on the energy density of the secondary battery is reduced when the third thickness is too large, and the possibility that the heat dissipation effect of the first layer is reduced and the first layer is easily pierced by the edge burrs of the first current collector is also reduced when the third thickness is too small.
  • the first layer is bonded to the second surface and the shell. Therefore, the first layer can also conduct the heat generated at the first outer pole piece when the secondary battery is overcharged to the shell, so that the heat is dissipated to the outside through the shell, improving the heat dissipation effect, thereby further improving the overcharge resistance of the secondary battery.
  • the first outer pole piece includes a first active material layer, a first current collector, and a second active material layer stacked in a first direction.
  • the first current collector includes a first surface facing the second pole piece and a second surface opposite to the first surface.
  • the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface.
  • the first pole piece is a positive pole piece
  • the mass of active material provided on the first current collector per unit area is G, G ⁇ 23 mg/cm 2 . Therefore, the possibility of active material falling off in the first region can be reduced, and the first region can be easily bent during preparation (i.e., extending away from the second direction).
  • the possibility of the first thickness being too large is reduced, so that the first region can be easily bent during preparation.
  • the isolation film adjacent to the first outer pole piece is bonded to the second region, thereby further reducing the possibility of short circuit between the first outer pole piece and the adjacent second pole piece.
  • the second pole piece adjacent to the first pole piece includes a third region and a fourth region connected in the second direction.
  • the first region and the third region overlap, and the second region and the fourth region overlap.
  • the isolation film adjacent to the first pole piece is also bonded to the third region, thereby further reducing the possibility of short circuit between the first pole piece and the adjacent second pole piece.
  • the third region includes a first partition and a second partition connected in a second direction.
  • the second partition When viewed from the third direction, the second partition includes a third end connected to the first partition. The first partition overlaps with the first region in the first direction. When viewed from the first direction, the second partition extends from the third end to beyond the first region. When viewed from the third direction, the second partition extends from the third end in a direction away from the first outer pole sheet.
  • the degree of deviation of the first region can be reduced, thereby reducing the influence of the first region on the energy density and appearance smoothness of the secondary battery, the possibility of the active material in the first region easily falling off and causing a short circuit, and the possibility of an increase in the active material in the first region that is difficult to play a capacity role.
  • the isolation film when viewed from the second direction, includes a plurality of main body segments stacked in the first direction and a plurality of connecting segments connecting the ends of two adjacent main body segments.
  • the main body segment is disposed between adjacent first and second pole pieces. Due to the provision of the connecting segments, the isolation film can restrain at least part of the first pole piece and at least part of the second pole piece, thereby reducing the possibility of the first pole piece and the second pole piece being excessively bulged and broken under the action of high-temperature gas when the secondary battery is overcharged.
  • the second aspect of the present application also provides an electronic device, which includes the above secondary battery.
  • the electronic device is powered by the above secondary battery, and the secondary battery has a high overcharge resistance performance, so the reliability and service life are improved.
  • FIG. 1 is a schematic structural diagram of a secondary battery provided in one embodiment of the present application when viewed from a first direction.
  • FIG. 2 is a cross-sectional view of the secondary battery shown in FIG. 1 along line II-II in some embodiments.
  • FIG. 3 is a cross-sectional view of the secondary battery shown in FIG. 1 along line III-III in some embodiments.
  • FIG. 4 is a partial enlarged view of the secondary battery at point A shown in FIG. 3 .
  • FIG. 5 is a cross-sectional view of the secondary battery shown in FIG. 1 along line IV-IV in some embodiments.
  • FIG. 6 is a cross-sectional view of the secondary battery shown in FIG. 1 along line II-II in some other embodiments.
  • FIG. 7 is a schematic structural diagram of the secondary battery shown in FIG. 1 before packaging in some embodiments.
  • FIG. 8 is a cross-sectional view of the secondary battery shown in FIG. 1 along line III-III in some other embodiments.
  • FIG. 9 is a schematic structural diagram of the secondary battery shown in FIG. 1 before packaging in some other embodiments.
  • FIG. 10 is a cross-sectional view of a first casing of the secondary battery shown in FIG. 7 or FIG. 9 .
  • FIG. 11 is a cross-sectional view of a second casing of the secondary battery shown in FIG. 7 or FIG. 9 .
  • FIG. 12 is a cross-sectional view of the secondary battery shown in FIG. 1 along line III-III in some other embodiments.
  • FIG. 13 is a cross-sectional view of the secondary battery shown in FIG. 1 along line III-III in some other embodiments.
  • FIG. 14 is a partial enlarged view of a secondary battery in some other embodiments.
  • FIG. 15 is a cross-sectional view of a separator of the secondary battery shown in FIG. 14 .
  • FIG. 16 is a partial enlarged view of a secondary battery in some other embodiments.
  • FIG. 17 is a cross-sectional view of a secondary battery provided in another embodiment of the present application.
  • FIG. 18 is a cross-sectional view of a secondary battery provided in another embodiment of the present application.
  • FIG. 19 is a schematic diagram of the structure of an electronic device provided in one embodiment of the present application.
  • spatially relative terms such as “above” and the like, may be used herein for convenience of description to describe the relationship of one element or feature to another element (or elements) or feature (or features) as illustrated in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device or apparatus in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figure is turned over, elements described as being “above” or “on” other elements or features would be oriented “below” or “below” the other elements or features. Thus, the exemplary term “above” may include both above and below. It should be understood that although the terms first, second, third, etc.
  • the parameter values being greater than, less than, or not equal to the designed relationship need to exclude the reasonable errors of the measuring equipment.
  • the positive electrode material When a secondary battery is overcharged, the positive electrode material releases excessive lithium ions, and the charging voltage exceeds the charging cut-off voltage.
  • the positive electrode material and the electrolyte are prone to undergo redox reactions under high pressure, generating a large amount of heat and causing thermal runaway of the secondary battery.
  • the occurrence of side reactions will also release a large amount of oxygen and other combustible gases, causing the shell to swell and aggravate thermal runaway.
  • the excess lithium ions that are released may accumulate on the surface of the negative electrode and precipitate lithium dendrites. The lithium dendrites may pierce the isolation membrane and cause the positive and negative electrodes to short-circuit, thereby further accelerating heat generation. Therefore, overcharging a secondary battery will reduce the reliability and service life of the secondary battery.
  • an embodiment of the present application provides a secondary battery 100, including a housing 10, an electrode assembly 20 and an electrolyte (not shown) disposed in the housing 10, a first conductive plate 30, and a second conductive plate 40.
  • the electrode assembly 20 is a laminate structure, which includes a plurality of first pole pieces 21, a plurality of second pole pieces 22, and a plurality of isolation films 23.
  • the first pole pieces 21 and the second pole pieces 22 are alternately stacked in sequence, and a second pole piece 22 is provided in each of two adjacent first pole pieces 21, and a first pole piece 21 is provided in each of two adjacent second pole pieces 22.
  • the isolation film 23 is disposed between the adjacent first pole pieces 21 and the second pole piece 22, and the isolation film 23 is used to prevent the first pole piece 21 and the second pole piece 22 from directly contacting each other, thereby reducing the possibility of contact short circuit between the first pole piece 21 and the second pole piece 22.
  • the first conductive plate 30 is electrically connected to the first pole piece 21, and as shown in FIGS. 1 and 5 , the second conductive plate 40 is electrically connected to the second pole piece 22.
  • the first conductive plate 30 and the second conductive plate 40 are both extended from one end of the housing 10 , and the first conductive plate 30 and the second conductive plate 40 are used to connect to an external device (not shown).
  • the first direction X is the stacking direction of the first pole piece 21, the isolation film 23 and the second pole piece 22.
  • the first direction X has a first side X1 and a second side X2 opposite to the first side X1.
  • the second direction Y is the direction in which the first conductive plate 30 or the second conductive plate 40 extends out of the housing 10, and is also the direction in which the first conductive plate 30 or the second conductive plate 40 protrudes from the electrode assembly 20.
  • the third direction Z is the direction from the second conductive plate 40 to the first conductive plate 30.
  • the outermost pole pieces among the plurality of first pole pieces 21 are defined as the first outer pole piece 21a and the second outer pole piece 21b, respectively, and the inner pole piece among the plurality of first pole pieces 21 is the first inner pole piece 21c.
  • the first inner pole piece 21c is disposed between the first outer pole piece 21a and the second outer pole piece 21b, and the first inner pole piece 21c is located on the inner side of the first outer pole piece 21a.
  • the second pole piece 22 and the isolation film 23 may also be located between the first outer pole piece 21a and the second outer pole piece 21b.
  • the first outer pole piece 21a and the second outer pole piece 21b are located at the outermost layer of the electrode assembly 20.
  • the first side X1 is the direction from the second pole piece 22 toward the first outer pole piece 21a, or the direction from the second outer pole piece 21b toward the first outer pole piece 21a.
  • the second side X2 is a direction from the first outer pole piece 21 a toward the second outer pole piece 22 , or a direction from the first outer pole piece 21 a toward the second outer pole piece 21 b .
  • the first outer pole piece 21a and the second outer pole piece 21b are single-sided coated pole pieces.
  • the first outer pole piece 21a includes a first current collector 210 and a first active material layer 211 stacked in the first direction X.
  • the first current collector 210 includes a first surface 210a facing the second pole piece 22 and a second surface 210b opposite to the first surface 210a.
  • the first active material layer 211 is provided on the first surface 210a, and the second surface 210b is not provided with active material.
  • the first inner pole piece 21c is a double-sided coated pole piece.
  • the first inner pole piece 21c includes a first active material layer 211, a second current collector 213 and a second active material layer 212 stacked in the first direction X.
  • the second outer pole piece 21b includes a fourth current collector 214 and a first active material layer 211 stacked in the first direction X, and the first active material layer 211 of the second outer pole piece 21b is provided on the surface of the fourth current collector 214 facing the second pole piece 22.
  • the first pole piece 21 can be a positive pole piece.
  • the first current collector 210, the second current collector 213 and the fourth current collector 214 can all be positive electrode current collectors, and the first active material layer 211 and the second active material layer 212 can all be positive electrode active material layers.
  • the active material contained in the first active material layer 211 of the second outer pole sheet 21b can be the same as that of the first outer pole sheet 21a.
  • the active materials contained in the first active material layer 211 may be the same or different.
  • the active materials contained in the first active material layer 211 or the second active material layer 212 of the first inner pole piece 21c may be the same as or different from the active materials contained in the first active material layer 211 of the first outer pole piece 21a.
  • the waste of energy density is reduced.
  • the first pole piece 21 is a positive pole piece, the possibility of excessive lithium ion accumulation and lithium precipitation due to the failure of the second pole piece 22 to embed the corresponding lithium ions (such as the lithium ions released from the part of the active material when the second surface 210b is provided with active materials) can also be reduced.
  • the thickness of the first current collector 210 is the first thickness h 1
  • the thickness of the second current collector 213 is the second thickness h 2 , and 1.2 ⁇ h 1 /h 2 ⁇ 2.5.
  • the thickness h 1 of the first current collector 210 is larger, so that the first outer pole sheet 21a located at the outermost layer has a higher strength, so that a protective layer can be formed, reducing the possibility of damage to the electrode assembly 20 during mechanical abuse (such as extrusion, acupuncture, etc.), and improving the ability of the electrode assembly 20 to withstand mechanical impact.
  • the thickness h 1 of the first current collector 210 is larger than the thickness h 2 of the second current collector 213, which is also conducive to reducing the possibility that the first current collector 210 is easily curled or warped due to inconsistent tension on the opposite sides of the first current collector 210 coated on one side.
  • the thickness of the fourth current collector 214 of the second outer pole sheet 21 b may be set to be greater than the thickness of the second current collector 213 .
  • the second pole piece 22 may be a double-sided coated pole piece.
  • the second pole piece 22 includes a third active material layer 221, a third current collector 220, and a fourth active material layer 222 which are stacked.
  • the third active material layer 221 is arranged toward the first active material layer 211 across the isolation film 23, and the fourth active material layer 222 is arranged toward the second active material layer 212 across the isolation film 23.
  • the second pole piece 22 may be a negative pole piece.
  • the third current collector 220 may be a negative current collector
  • the third active material layer 221 and the fourth active material layer 222 may both be negative active material layers.
  • a plurality of first pole tabs 51 and a plurality of second pole tabs 52 may be provided on the electrode assembly 20.
  • the plurality of first pole tabs 51 are respectively connected to the first current collector 210 and the second current collector 213.
  • the plurality of second pole tabs 52 are respectively connected to the third current collector 220.
  • the first pole tabs 51 are welded to the first conductive plate 30 by transfer welding, and the second pole tabs 52 are welded to the second conductive plate 40 by transfer welding.
  • the positive electrode current collector may be aluminum foil or nickel foil, and the negative electrode current collector may be at least one of copper foil, nickel foil or carbon-based current collector.
  • the positive electrode active material layer contains positive electrode active material, and the positive electrode active material includes a compound (lithiated intercalation compound) that can reversibly embed and deintercalate lithium ions.
  • the positive electrode active material may include a lithium transition metal composite oxide.
  • the lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel.
  • the positive electrode active material is selected from at least one of lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ) or lithium iron phosphate (LiFePO 4 ).
  • the negative electrode active material layer contains negative electrode active material, and a negative electrode active material known in the art that can reversibly deintercalate active ions is used, and this application does not limit it.
  • graphite can be selected from a combination of one or more of artificial graphite, natural graphite and modified graphite
  • silicon-based materials can be selected from a combination of one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys
  • tin-based materials can be selected from a combination of one or more of elemental tin, tin oxide compounds, and tin alloys, etc.
  • the isolation film 23 is a porous structure, which includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene or ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene have a good effect on improving short circuits and can improve the stability of the secondary battery 100 through the shutdown effect.
  • the electrode assembly 20 may also include a separator 23.
  • the separator 23 is an integrated structure, and is formed into a Z-shaped structure by alternately bending and folding in positive and negative directions.
  • the separator 23 includes a plurality of main body segments 233 stacked and a connecting segment 234 connecting the ends of two adjacent main body segments 233.
  • Each main body segment 233 is disposed between the adjacent first pole piece 21 and the second pole piece 22. Due to the provision of the connecting segment 234, the separator 23 can play a role in at least a portion of the first pole piece 21 and at least a portion of the second pole piece 22.
  • the restraint function reduces the possibility that the first pole piece 21 and the second pole piece 22 are excessively bulged and broken under the action of high-temperature gas when the secondary battery 100 is overcharged.
  • the shell 10 may be a packaging bag obtained by packaging with a packaging film, and the secondary battery 100 is a soft-pack battery.
  • the shell 10 includes a main body 11 for accommodating the electrode assembly 20 and a packaging part 12 connected to the main body 11.
  • the first conductive plate 30 and the second conductive plate 40 both extend from the packaging part 12 to the shell 10.
  • the main body 11 includes a first end face 110 connected to the packaging part 12.
  • the first end face 110 extends from the packaging part 12 to the first side X1.
  • FIG. 7 is a schematic diagram of the structure of the secondary battery 100 before packaging. As shown in FIG.
  • the shell 10 includes a first shell 101 and a second shell 102 arranged opposite to each other in the first direction X.
  • the first shell 101 includes a first shell area 101a and a second shell area 101b connected to each other.
  • the three sides of the second shell area 101b are surrounded by the first shell area 101a.
  • the second shell 102 includes a third shell area 102a and a fourth shell area 102b connected to each other.
  • the three sides of the fourth shell area 102b are surrounded by the third shell area 102a.
  • the shell 10 is encapsulated by the first shell 101 and the second shell 102.
  • the second shell area 101b of the first shell 101 is provided with a first recess R1
  • the second shell 102 is a flat plate structure.
  • the electrode assembly 20 can be placed in the first recess R1 of the first shell 101, and the second shell 102 is covered on the first shell 101.
  • the first recess R1 is closed by the second shell area 101b of the first shell 101, and the first shell area 101a is connected to the third shell area 102a to encapsulate the main body 11.
  • the first conductive plate 30 is bent as a whole.
  • the first conductive plate 30 includes a first conductive area 31 and a second conductive area 32 connected to each other.
  • the first conductive area 31 is disposed in the packaging portion 12 and extends out of the housing 10 from the packaging portion 12 along the second direction Y.
  • the second conductive area 32 is electrically connected to the first electrode piece 21 (e.g., the second conductive area 32 is connected to the first electrode piece 21 through the first electrode ear 51).
  • the second conductive area 32 is bent relative to the first conductive area 31.
  • the second conductive area 32 includes a first end 321 connected to the first conductive area 31 and a second end 322 disposed opposite to the first end 321, and the second conductive area 32 extends from the first end 321 to the first side X1. Therefore, when viewed from the second direction Y, the second conductive area 32 overlaps with the first end surface 110. Among them, the second conductive area 32 can extend along the first direction X, or can be tilted relative to the first direction X.
  • the first end surface 110 when viewed from the third direction Z, may further include a first portion 111 extending from the packaging portion 12 to the first side X1 and a second portion 112 extending from the packaging portion 12 to the second side X2.
  • the packaging portion 12 is located at the connection between the first portion 111 and the second portion 112 in the first direction X.
  • the length W 1 of the first portion 111 in the first direction X is less than the length W 2 of the second portion 112 in the first direction X.
  • the first portion 111 is a deep pit surface of the shell 10
  • the second portion 112 is a shallow pit surface of the shell 10.
  • FIG9 is a schematic diagram of the structure of the secondary battery 100 before packaging.
  • the fourth shell area 102b of the second shell 102 is correspondingly provided with a second recess R2.
  • the second shell area 101b and the fourth shell area 102b together constitute the main body 11 for accommodating the electrode assembly 20.
  • the materials of the first shell 101 and the second shell 102 may both be multilayer sheets.
  • the first shell 101 may include a first protective layer 1011, a first metal layer 1012, and a first polymer layer 1013 stacked in sequence. Compared with the first protective layer 1011, the first polymer layer 1013 is closer to the electrode assembly 20.
  • the material of the first protective layer 1011 can be a polymer resin, which can be used to protect the first metal layer 1012, reduce the possibility of damage to the first metal layer 1012 due to external force, and at the same time delay the air infiltration of the external environment, and maintain the normal operation of the secondary battery 100.
  • the material of the first protective layer 1011 can be selected from at least one of polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyamide, and polyimide.
  • the first metal layer 1012 can be used to delay the moisture penetration of the external environment and reduce the damage to the electrode assembly 20 caused by external force.
  • the first metal layer 1012 may be an aluminum foil layer or a steel foil layer.
  • the first polymer layer 1013 has the property of being heated and melted, can be used for packaging, and can reduce the possibility of the multilayer sheet being dissolved or swelled by the organic solvent in the electrolyte.
  • the first polymer layer 1013 can also be used to reduce the possibility of the electrolyte in the electrolyte contacting the first metal layer 1012 and causing the metal layer to be corroded.
  • the first polymer layer 1013 includes a polymer material, which can be selected from at least one of polypropylene, propylene copolymer, polyethylene, and polymethyl methacrylate.
  • the second shell 102 may include a second protective layer 1021, a second metal layer 1022, and a second polymer layer 1023 stacked in sequence.
  • first shell 101 and the second shell 102 can be formed by a sealing sheet
  • the materials of the second protective layer 1021, the second metal layer 1022 and the second polymer layer 1023 are exactly the same as the materials of the first protective layer 1011, the first metal layer 1012 and the first polymer layer 1013, and are not described again here.
  • a certain temperature and pressure can be applied to the first shell area 101a and the third shell area 102a by using the sealing head of the packaging equipment, so that the first polymer layer 1013 and the second polymer layer 1023 are melted and bonded together to form the packaging part 12.
  • the housing 10 may also be a metal housing, such as a steel housing or an aluminum housing.
  • the first outer pole piece 21a when viewed from the third direction Z, includes a first region 2101 and a second region 2102 connected in the second direction Y.
  • the first region 2101 when viewed from the third direction Z, includes a first end 2101a connected to the second region 2102 and a second end 2101b disposed opposite to the first end 2101a in the second direction Y.
  • the first region 2101 extends from the first end 2101a away from the second direction Y, and the second end 2101b is further away from the second pole piece 22 in the first direction X than the first end 2101a.
  • an extension line S1 can be formed by extending outward along the contour of the first region 2101, and an extension line S2 of the second region 2102 can be made along the second direction Y.
  • the intersection of the extension line S1 and the extension line S2 is the first end 2101a, and the first end 2101a can be regarded as the boundary point between the first region 2101 and the second region 2102 when viewed from the third direction Z.
  • the second end 2101b is arranged opposite to the first end 2101a in the second direction Y, which does not mean that the line S3 connecting the first end 2101a and the second end 2101b must extend along the second direction Y.
  • the second end 2101b when the second end 2101b is described as being arranged opposite to the first end 2101a in the second direction Y, it means that the line S3 connecting the first end 2101a and the second end 2101b may deviate from the second direction Y under the premise of ensuring that the purpose of the present invention is achieved.
  • the second region 2102 may include a curved portion when viewed from the third direction Z.
  • the first region 2101 is further away from the first conductive plate 30 than the second region 2102, thereby reducing the possibility that the first pole ear 51 enters the space between the first region 2101 and the second pole piece 22 adjacent to the first outer pole piece 21a when the electrode assembly 20 moves in the housing 10 along the second direction Y (such as when the secondary battery 100 falls or vibrates), thereby causing a contact short circuit.
  • the first region 2101 extends from the first end 2101a to the first side X1.
  • the first region 2101 may overlap with the first end face 110.
  • the first region 2101 of the first outer pole piece 21a is at least partially placed in the first recess R1 formed by the extension of the first end face 110.
  • the first region 2101 extends from the first end 2101a to the first side X1.
  • the first region 2101 may overlap with the first portion 111. This can also reduce the friction on the first outer pole piece 21 a when the second shell 102 is covered on the first shell 101 , thereby reducing the possibility of deformation of the first outer pole piece 21 a due to friction.
  • the second pole piece 22 adjacent to the first outer pole piece 21a includes a third region 2201 and a fourth region 2202 connected in the second direction Y.
  • the first region 2101 is arranged opposite to the third region 2201, and the first region 2101 and the third region 2201 overlap.
  • the second region 2102 is arranged opposite to the fourth region 2202, and the second region 2102 and the fourth region 2202 overlap. Therefore, when the secondary battery 100 is charged, the lithium ions precipitated from the first region 2101 can be embedded in the third region 2201, and the lithium ions precipitated from the second region 2102 can be embedded in the fourth region 2202.
  • a dotted line S4 parallel to the first direction X can be made through the first end 2101a, and when viewed from the third direction Z, the intersection of the dotted line S4 and the second pole piece 22 is the boundary between the third region 2201 and the fourth region 2202. Since the first region 2101 of the first outer pole piece 21a deviates from the extension of the second direction Y, in the first direction X, the distance between the first region 2101 and the third region 2201 is greater than the distance between the second region 2102 and the fourth region 2202, so that the ion transmission path between the first region 2101 and the third region 2201 is extended.
  • the distance between the first region 2101 and the third region 2201 is not a constant value, and the distance between the first end 2101a of the first region 2101 and the third region 2201 is less than the distance between the second end 2101b and the third region 2201.
  • the third region 2201 includes a first partition 2203 and a second partition 2204 connected in the second direction Y.
  • the second partition 2204 When viewed from the third direction Z, the second partition 2204 includes a third end 2204a connected to the first partition 2203 and a fourth end 2204b arranged opposite to the third end 2204a.
  • the first partition 2203 overlaps with the first region 2101 in the first direction X.
  • the second partition 2204 When viewed from the first direction X, the second partition 2204 extends from the third end 2204a to beyond the first area 2101, and the second partition 2204 is the extension area 2200 of the second pole piece 22 adjacent to the first outer pole piece 21a.
  • a dotted line S5 can be drawn along the first direction X at the second end 2101b, and when viewed from the third direction Z, the intersection of the dotted line S5 and the second pole piece 22 is the third end 2204a, and the third end 2204a is also the dividing point between the first partition 2203 and the second partition 2204 when viewed from the third direction Z.
  • the present invention sets the first region 2101 of the first external pole piece 21a to deviate from the second direction Y and extend outward, so that the ion transmission path between the first region 2101 and the third region 2201 is extended and the transmission impedance is increased.
  • the third region 2201 can be used as a sacrificial position during overcharge to preferentially deposit lithium, thereby reducing the probability or degree of lithium deposition at other locations in the second pole piece 22 adjacent to the first external pole piece 21a, and also reducing the probability or degree of lithium deposition at other second pole pieces 22, thereby reducing the occurrence of thermal runaway.
  • the distance between the first region 2101 and the third region 2201 is relatively large, the possibility of lithium dendrites deposited in the third region 2201 contacting the first region 2101 is reduced even after piercing the isolation membrane 23, thereby reducing the possibility of lithium dendrites contacting the first external pole piece 21a and short-circuiting.
  • the present application can improve the overcharge resistance of the secondary battery 100, thereby improving the reliability and service life of the secondary battery 100. Please refer to Figure 13.
  • the second external pole sheet 21b can also be provided with the same structure as the first external pole sheet 21a, such as providing a region extending outward from the second direction Y on the second external pole sheet 21b.
  • the first region 2101 may be arranged closer to the first conductive plate 30 than the second region 2102 in the second direction Y. Since there is a certain space between the first end surface 110 and the electrode assembly 20 to accommodate the first electrode tab 51 and part of the first conductive plate 30, by arranging the first region 2101 closer to the first conductive plate 30, when the secondary battery 100 is overcharged, it is beneficial for the gas generated near the first region 2101 to be released into the above space, thereby reducing the possibility of excessive gas accumulation and causing the first region 2101 to further deviate from the second direction Y, thereby reducing the impact on the energy density and appearance flatness of the secondary battery 100 when the first region 2101 deviates to a large extent, and also reducing the possibility that the active material in the first region 2101 is easy to fall off and cause a short circuit, and also reducing the possibility that the active material in the first region 2101 is difficult to play a capacity role.
  • the mass of the active material provided on the first current collector 210 per unit area is G (i.e., the weight of the first active material layer 211 per unit area is G), and G ⁇ 23 mg/cm 2 . Therefore, the possibility of the active material in the first region 2101 falling off can be reduced, and the first region 2101 of the first external pole sheet 21a can be easily bent during preparation (i.e., extending away from the second direction Y).
  • G the mass of the active material provided on the first current collector 210 per unit area
  • G i.e., the weight of the first active material layer 211 per unit area is G
  • G ⁇ 23 mg/cm 2 the mass of the active material provided on the first current collector 210 per unit area
  • the angle ⁇ between the line S3 connecting the first end 2101a and the second end 2101b and the second direction Y satisfies: 1° ⁇ 12°.
  • the first region 2101 can deviate from the second direction Y by a certain range, thereby extending the ion transmission path between the first region 2101 and the third region 2201, so that when the secondary battery 100 is overcharged, the third region 2201 can be used as a sacrificial position during overcharge to preferentially deposit lithium, and the deviation of the first region 2101 from the second direction Y by a certain range also reduces the possibility of lithium dendrites deposited in the third region 2201 contacting the first region 2101.
  • the influence of the first region 2101 on the energy density and appearance smoothness of the secondary battery 100 when the deviation degree of the first region 2101 is large is reduced.
  • the possibility that the active material in the first region 2101 will easily fall off and cause a short circuit when the deviation degree of the first region 2101 is large is also reduced.
  • the possibility that the active material in the first region 2101 will be difficult to play a capacity role when the deviation degree of the first region 2101 is large is also reduced.
  • the ion transmission path between the first region 2101 and the third region 2201 is further extended, so that when the secondary battery 100 is overcharged, the third region 2201 can be used as a sacrificial position during overcharge to preferentially precipitate lithium, and the possibility of lithium dendrites precipitated from the third region 2201 contacting the first region 2101 is further reduced.
  • the influence of the first region 2101 on the energy density and appearance smoothness of the secondary battery 100 is further reduced, and the possibility of the active material in the first region 2101 easily falling off and causing a short circuit is further reduced, and the possibility of an increase in active materials in the first region 2101 that are difficult to play a capacity role is further reduced.
  • the steps for measuring ⁇ may be: (1) using X-rays to perform two-dimensional projection and scanning tests on the secondary battery 100 from a third direction Z.
  • the instrument may be an instrument or device known to those skilled in the art (e.g., GE Phoenix vtomex S equipment) to obtain a CT image; (2) using a caliper or other suitable measuring tool to directly measure the value of ⁇ .
  • the steps of measuring ⁇ may also be: (1) discharging the secondary battery 100 at 0.2C to 2.75V; (2) preparing a resin composition, which is prepared by mixing a crystal glue resin matrix (such as epoxy resin), a catalyst and a curing agent in a certain proportion; (3) pouring the resin composition into a mold, and cutting the shell 10 of the secondary battery 100 and placing it in the mold at an angle to reduce the bubbles that may remain at the bottom of the secondary battery 100, and then slowly pouring the resin composition to completely immerse the secondary battery 100 in the resin composition.
  • a crystal glue resin matrix such as epoxy resin
  • the resin composition slowly flows into the shell 10 through the cutout of the shell 10; (4) the secondary battery 100 is adjusted to a horizontal position, excess bubbles are discharged, and then the secondary battery 100 is allowed to stand until the resin composition solidifies; (5) the secondary battery 100 is cut along a cross section perpendicular to the third direction Z and the cut surface is polished to obtain a cross section of the secondary battery 100; (6) the angle ⁇ between the line S3 connecting the first end 2101a and the second end 2101b and the second direction Y is marked on the cross section, and the value of ⁇ is directly measured using a caliper or other suitable measuring tool.
  • the length of the first region 2101 extending from the first end 2101a to the second end 2101b is a first length L 1 (when the first region 2101 includes a curved portion, L 1 refers to the arc length of the first region 2101), and as shown in FIG3 , the length of the second region 2102 in the second direction Y is a second length L 2 , 7 ⁇ L 2 /L 1 ⁇ 29.
  • the influence of the first region 2101 on the energy density and appearance flatness of the secondary battery 100 when the above ratio is too small is reduced, and the possibility of increasing the number of active materials in the first region 2101 that are difficult to play a capacity role is also reduced.
  • the possibility that the third region 2201 fails to significantly reduce the probability or degree of lithium deposition at other locations when overcharged is reduced when the ratio is too large (such as when the length L1 is too small and the area of the first region 2101 is too small).
  • 11 ⁇ L 2 /L 1 ⁇ 19 thereby further reducing the influence of the first region 2101 on the energy density and appearance flatness of the secondary battery 100, further reducing the possibility of increasing the active material that is difficult to play a capacity role in the first region 2101, and further reducing the possibility that the third region 2201 fails to significantly reduce the probability or degree of lithium deposition in other locations when overcharged.
  • the lengths L 1 and L 2 can be measured using a measurement step similar to the angle ⁇ .
  • the secondary battery 100 may further include a first layer 60 including an insulating material disposed on the second surface 210b.
  • the first layer 60 is used to dissipate the heat generated at the first external pole piece 21a when the secondary battery 100 is overcharged, thereby reducing the temperature of the electrode assembly 20 and improving the overcharge resistance of the secondary battery 100.
  • the first layer 60 may also insulate the first current collector 210 from the shell 10, thereby reducing the possibility that the edge burrs of the first current collector 210 (the above burrs may be generated when the first current collector 210 is cut, but the present application is not limited thereto) pierce the polymer layer of the shell 10 and short-circuit with the aluminum foil layer, resulting in a large amount of heat generation in the secondary battery 100, and also reduce the possibility that the lithium ions released from the first external pole piece 21a during the charging process react to form an aluminum-lithium alloy (AlLi) at the contact point between the first current collector 210 and the aluminum foil layer and cause corrosion of the aluminum foil layer.
  • AlLi aluminum-lithium alloy
  • the insulating material of the first layer 60 may be selected from at least one of an inorganic ceramic material and a binder.
  • the inorganic ceramic material includes at least one of hafnium dioxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide.
  • the binder may be selected from at least one of styrene-butadiene rubber, polypropylene, polyacrylic acid, acrylate and its derivatives, polyvinyl alcohol, natural rubber or modified rubber.
  • the adhesive body can be single-sided adhesive, double-sided adhesive or hot melt adhesive, and the first layer 60 can be bonded to the second surface 210b and cover the entire second surface 210b. In other embodiments, the first layer 60 can be distributed in dots, strips or other irregular shapes on the second surface 210b.
  • the thickness of the first current collector 210 is defined as the first thickness h 1
  • the thickness of the first layer 60 is defined as the third thickness h 3
  • h 3 ⁇ 2h 1 the influence of the first layer 60 on the energy density of the secondary battery 100 is reduced when the thickness h 3 is too large, and the possibility that the heat dissipation effect of the first layer 60 is reduced and the first layer 60 is easily pierced by the edge burrs of the first current collector 210 is also reduced when the thickness h 3 is too small.
  • the first layer 60 may be a double-sided adhesive or a hot melt adhesive, which bonds the second surface 210b and the housing 10. Therefore, the first layer 60 can also conduct the heat generated at the first outer pole piece 21a when the secondary battery 100 is overcharged to the housing 10, so that the heat is dissipated to the outside through the housing 10, thereby improving the heat dissipation effect and further improving the overcharge resistance of the secondary battery 100.
  • the isolation film 23 adjacent to the first outer pole piece 21a is bonded to the second region 2102, thereby further reducing the possibility of short circuit between the first outer pole piece 21a and the adjacent second pole piece 22.
  • the isolation film 23 may include a first adhesive layer 231, a base layer 230, and a second adhesive layer 232 stacked in the first direction X, and the first adhesive layer 231, the base layer 230, and the second adhesive layer 232 are all porous structures. The isolation film 23 is bonded to the second region 2102 through the first adhesive layer 231.
  • the base layer 230 may be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the first adhesive layer 231 and the second adhesive layer 232 respectively include an adhesive, and the adhesive includes a homopolymer or a copolymer formed by a polymer monomer, and the polymer monomer includes at least one of vinylidene fluoride, hexafluoropropylene, acrylic acid, acrylic ester, butadiene, styrene, acrylonitrile, ethylene, chlorostyrene, fluorostyrene or propylene.
  • the isolation film 23 adjacent to the first external pole piece 21a can also be bonded to the third region 2201, such as the isolation film 23 adjacent to the first external pole piece 21a is bonded to the third region 2201 through the second adhesive layer 232, thereby further reducing the possibility of short circuit between the first external pole piece 21a and the adjacent second pole piece 22.
  • the isolation film 23 is a porous structure, the gas can pass through the isolation film 23 and open the contact interface of the adjacent first external pole piece 21a, the isolation film 23 and the second pole piece 22, thereby reducing the possibility of short circuit between the lithium dendrites precipitated in the third region 2201 and the first external pole piece 21a, and also facilitating the timely dissipation of heat in the electrode assembly 20.
  • the second partition 2204 when viewed from the third direction Z, extends from the third end 2204a in a direction away from the first outer pole sheet 21a.
  • the extension direction of the second partition 2204 is inclined relative to the second direction Y.
  • the ion transmission path between the third region 2201 and the first region 2101 can also be extended, thereby reducing the degree of deviation of the first region 2101, thereby reducing the impact on the energy density and appearance flatness of the secondary battery 100 when the first region 2101 deviates to a large extent, and also reducing the possibility that the active material of the first region 2101 is easy to fall off and cause a short circuit when the first region 2101 deviates to a large extent, and also reducing the possibility that the active material of the first region 2101 is difficult to play a capacity role in the first region 2101 when the first region 2101 deviates to a large extent.
  • the first electrode 21 may be set as a negative electrode and the second electrode 22 may be set as a positive electrode.
  • the first region 2101 may be used as a sacrificial position during overcharge to preferentially deposit lithium, thereby reducing the possibility or degree of lithium deposition at other positions of the first external electrode 21a, and also reducing the possibility or degree of lithium deposition at other first electrode 21 outside the first external electrode 21a.
  • the distance between the first region 2101 and the third region 2201 is relatively large, the possibility of lithium dendrites deposited in the first region 2101 contacting the third region 2201 is reduced even after piercing the isolation membrane 23, thereby reducing the possibility of lithium dendrites contacting the third region 2201 and causing a short circuit.
  • the first outer pole piece 21a may also be a double-sided coated pole piece.
  • the first outer pole piece 21a includes a first active material layer 211, a first current collector 210, and a second active material layer 212 stacked in a first direction X.
  • the first current collector 210 includes a first surface 210a facing the second pole piece 22 and a second surface 210b opposite to the first surface 210a.
  • the first active material layer 211 is disposed on the first surface 210a
  • the second active material layer 212 is disposed on the second surface 210b.
  • the mass of the active material disposed on the first current collector 210 per unit area is G, and G ⁇ 23 mg/cm 2 , which specifically refers to the mass of the first active material disposed on the first current collector 210 per unit area.
  • the total mass of the material layer 211 and the second active material layer 212 is less than 23 mg/cm 2 .
  • the secondary battery 100 of the present application may be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery and a lithium ion polymer secondary battery.
  • One embodiment of the present application also provides an electronic device 1, including the above-mentioned secondary battery 100.
  • the electronic device 1 is powered by the above-mentioned secondary battery 100, and the secondary battery 100 has a high overcharge resistance.
  • the electronic device 1 of the present application can be, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight,
  • the secondary battery 100 is a soft-pack lithium-ion secondary battery as an example and the present application is described in combination with a specific test method.
  • the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.
  • Preparation of the first pole piece 21 Mix the active materials lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, prepare a slurry with a solid content of 75wt%, and stir evenly. The slurry is evenly coated on one surface of an aluminum foil with a thickness of 12 ⁇ m, and an empty foil area is reserved at the edge of the aluminum foil. Dry at 90°C to obtain an active material layer with a thickness of 100 ⁇ m. The first pole piece 21 coated on one side is subsequently used as the first outer pole piece 21a and the second outer pole piece 21b. When preparing other first pole pieces 21 coated on both sides, repeat the above steps on the other surface of the aluminum foil. Then, the excess empty foil area is cut off by laser die cutting to obtain the first pole ear 51.
  • NMP N-methylpyrrolidone
  • Preparation of the second pole piece 22 Mix the negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, prepare a slurry with a solid content of 70wt%, and stir evenly. The slurry is evenly coated on one surface of a copper foil with a thickness of 10 ⁇ m, and an empty foil area is reserved at the edge of the copper foil. Dry at 110°C to obtain an active material layer with a thickness of 150 ⁇ m. Repeat the above steps on the other surface of the foil. Then, the excess empty foil area is cut off by laser die-cutting to obtain the second pole ear 52.
  • Super P conductive carbon black
  • SBR styrene-butadiene rubber
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • FEC fluoroethylene carbonate
  • PS 1,3-propane sultone
  • LiPF 6 lithium salt lithium hexafluorophosphate
  • Preparation of electrode assembly 20 The first pole piece 21, the separator 23 and the second pole piece 22 except the first pole piece 21a are stacked in sequence, and the separator 23 is selected to be a polyethylene (PE) film with a thickness of 15 ⁇ m.
  • PE polyethylene
  • the structure obtained after stacking is subjected to flat plate hot pressing for 10s at a temperature of 60°C and a pressure of 1Mpa.
  • the first pole piece 21a and the second pole piece 21b are stacked on opposite sides of the above structure respectively, and then the position of the first pole piece 21a to be bent is heated for 60s by an arc roller at a temperature of 150°C, so that the first area 2101 deviates from the second direction Y and bends outward.
  • the bending related parameters are recorded in Tables 1 and 2.
  • the angle ⁇ , L2 / L1 and other values can be controlled by adjusting the temperature and heating time of the arc roller.
  • the second area 2102 of the first pole piece 21a is subjected to flat plate hot pressing for 10s at a temperature of 60°C and a pressure of 1Mpa, so that the second area 2102 is bonded to the separator 23.
  • the second outer pole piece 21 b is subjected to heat pressing through similar steps.
  • the first pole ear 51 and the second pole ear 52 are welded to the first conductive plate 30 and the second conductive plate 40 respectively by transfer welding.
  • the first conductive plate 30 is made of aluminum and the second conductive plate 40 is made of nickel.
  • the aluminum-plastic film (thickness of 150 ⁇ m) with a pit is placed in the assembly fixture with the pit facing upwards.
  • the electrode assembly 20 is placed in the pit.
  • the electrolyte is injected into the pit of the aluminum-plastic film, and the first conductive plate 30 and the second conductive plate 40 are led out of the aluminum-plastic film.
  • the edge of the aluminum-plastic film is pressurized with a special-shaped sealing head to form a packaging part 12, and then the injection is performed. Liquid, chemical formation, packaging, and battery making.
  • the difference from the first embodiment is that the outermost first pole piece 21 is not bent outward.
  • the test steps of the overcharge test include: 1) charging the battery to 4.48V at a constant current of 0.5C at 25°C, and charging to 0.05C at a constant voltage; 2) after the battery is coated with white foam with a thickness of 10mm (the foam needs to cover the entire surface of the battery), the battery is placed in an overcharge and overdischarge tester (manufacturer: Arbin, model: BT-ML-30V15A), and then the battery is charged to 18.5V at a constant current of 1C, and constant voltage is charged for 2h; 3) monitoring the changes in the open circuit voltage and temperature of the battery during overcharge, measuring the weight of the battery after the overcharge is completed, and observing whether the battery smokes, catches fire, etc. If not, it passes, and then the number of batteries that pass the test is counted, and the results are recorded in Table 1.
  • Overcharge pass rate X/20 means that among the 20 samples tested, the number of samples that passed the test is X.
  • Examples 1-8 Examples 1 and 4-6 satisfy 3° ⁇ 10°, so the overcharge pass rate and energy density are both high; the angle ⁇ of Example 2 is smaller, so when the secondary battery 100 is overcharged, lithium deposition does not occur preferentially in the third region 2201, and the possibility of lithium dendrites deposited in the third region 2201 contacting the first region 2101 is increased, so the overcharge pass rate is relatively reduced; the angle ⁇ of Examples 7-8 is larger, so the energy density is reduced.

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Abstract

一种二次电池及电子装置。二次电池包括壳体、设于壳体内的电极组件、以及第一导电板。电极组件为叠片结构，电极组件包括在第一方向上依次叠设的第一极片、隔离膜和第二极片。第一导电板连接于第一极片，第一导电板沿与第一方向垂直的第二方向从壳体伸出。第一极片包括位于电极组件中的最外层的第一外极片，从与第一方向和第二方向均垂直的第三方向观察，第一外极片包括在第二方向上相连接的第一区域和第二区域。从第三方向观察，第一区域包括连接于第二区域的第一端和在第二方向上与第一端相对设置的第二端。第一区域自第一端偏离第二方向延伸，且第二端相较于第一端在第一方向上更远离第二极片。所述二次电池可提高抗过充性能。

Description

二次电池及电子装置 技术领域
本申请涉及储能技术领域，尤其涉及一种二次电池及具有上述二次电池的电子装置。
背景技术
随着消费电子类的产品如笔记本电脑、手机、掌上游戏机、平板电脑、移动电源和无人机等的普及，人们对二次电池(例如，锂离子二次电池)的要求越来越严格。
然而，二次电池在过充电时可能会出现热失控，降低了二次电池的可靠性和使用寿命。
发明内容
鉴于以上不足之处，有必要提供一种有利于提高抗过充性能的二次电池。
另，本申请还提供一种具有上述二次电池的电子装置。
本申请第一方面提供一种二次电池，包括壳体、设于壳体内的电极组件、以及第一导电板。电极组件为叠片结构，包括在第一方向上依次叠设的第一极片、隔离膜和第二极片。第一导电板连接于第一极片。第一导电板沿与第一方向垂直的第二方向从壳体伸出。第一极片包括第一外极片，第一外极片为电极组件的最外层。从与第一方向和第二方向均垂直的第三方向观察，第一外极片包括在第二方向上相连接的第一区域和第二区域。从第三方向观察，第一区域包括连接于第二区域的第一端和在第二方向上与第一端相对设置的第二端，第一区域自第一端偏离第二方向延伸，且第二端相较于第一端在第一方向上更远离第二极片。
本申请通过设置第一区域偏离第二方向延伸，当二次电池过充时，第一区域或与第一区域对应的第二极片可作为过充时的牺牲位置优先发生析锂，从而减小了其它位置发生析锂的概率或析锂程度，也有利于减小析出的锂枝晶刺穿隔离膜后导致接触短路的可能性，减小热失控的发生。再者，二次电池过充时若第一区域附近产气，相邻的第一外极片、隔离膜以及第二极片的接触界面可在气体作用下被撑开，这有利于进一步降低锂枝晶刺穿隔离膜后导致接触短路的可能性，也有利于电极组件内的热量及时散发。因此，本申请可提高二次电池的抗过充性能，从而提高可靠性和使用寿命。
在一些可能的实现方式中，从第三方向观察，第一端和第二端的连线与第二方向之间的夹角α满足：1°≤α≤12°。通过限定夹角α的下限值，可使得二次电池过充时第一区域或与第一区域对应的第二极片优先发生析锂，也减小了析出的锂枝晶刺穿隔离膜后导致接触短路的可能性。通过限定夹角α的上限值，减小了第一区域对二次电池的能量密度及外观平整度的影响，也减小了第一区域的活性材料容易脱落并导致短路的可能性，也减小了第一区域难以发挥容量作用的活性材料增多的可能性。
在一些可能的实现方式中，3°≤α≤10°，从而进一步使得二次电池过充时第一区域或与第一区域对应的第二极片优先发生析锂，也减小了析出的锂枝晶刺穿隔离膜后导致接触短路的可能性；而且，也进一步减小了第一区域对二次电池的能量密度及外观平整度的影响、第一区域的活性材料容易脱落并导致短路的可能性、第一区域难以发挥容量作用的活性材料增多的可能性。
在一些可能的实现方式中，从第三方向观察，第一区域自第一端延伸至第二端的长度为第一长度，第二区域在第二方向上的长度为第二长度，第二长度与第一长度的比值大于等于7且小于等于29。通过限定L2/L1的下限值，减小了第一区域对二次电池的能量密度及外观平整度的影响，也减小了第一区 域难以发挥容量作用的活性材料增多的可能性。通过限定L2/L1的上限值，减小了过充时未能显著减小其它位置发生析锂的概率或析锂程度的可能性。
在一些可能的实现方式中，第二长度与第一长度的比值大于等于11且小于等于19，从而进一步减小了第一区域对二次电池的能量密度及外观平整度的影响，进一步减小了第一区域中难以发挥容量作用的活性材料增多的可能性，也进一步减小了过充时未能显著减小其它位置发生析锂的概率或析锂程度的可能性。
在一些可能的实现方式中，在第二方向上，第一区域相较于第二区域更远离第一导电板，从而减小了当电极组件沿第二方向在壳体内移动时，与第一导电板连接的第一极耳进入第一区域和与第一外极片相邻的第二极片之间的空间、进而导致接触短路的可能性。
在一些可能的实现方式中，在第二方向上，第一区域相较于第二区域更靠近第一导电板。因此当二次电池过充时，有利于第一区域附近产生的气体释放至壳体用于收容第一导电板及与第一导电板连接的第一极耳的空间内，减小过量气体聚集并导致第一区域进一步偏离第二方向的可能性。
在一些可能的实现方式中，第一方向具有自第二极片朝向第一外极片的第一侧。壳体为包装袋且包括用于容置电极组件的主体部和连接主体部的封装部，第一导电板从封装部伸出壳体。主体部包括连接封装部的第一端面。从第三方向观察，第一端面自封装部向第一侧延伸。从第三方向观察，第一区域自第一端向第一侧延伸。因此，第一外极片的第一区域至少部分置于第一端面向第一侧延伸所形成的壳体凹部内，从而利于壳体从另一侧盖合时减小对第一外极片的摩擦，进而减小第一外极片在摩擦下变形的可能性。
在一些可能的实现方式中，第一方向还具有与第一侧相背的第二侧。壳体为包装袋且包括用于容置电极组件的主体部和连接主体部的封装部，第一导电板从封装部伸出壳体。主体部包括连接封装部的第一端面。从第三方向观察，第一端面包括自封装部向第一侧延伸的第一部分和自封装部向第二侧延伸的第二部分。第一部分在第一方向上的长度大于第二部分在第一方向上的长度。从第三方向观察，第一区域自第一端向第一侧延伸。因此，第一外极片的第一区域至少部分置于第一部分向第一侧延伸所形成的壳体凹部内，从而利于壳体从另一侧盖合时减小对第一外极片的摩擦，进而减小第一外极片在摩擦下变形的可能性。
在一些可能的实现方式中，壳体为包装袋且包括用于容置电极组件的主体部和连接主体部的封装部。第一导电板包括相连接的第一导电区和第二导电区。第一导电区设于封装部内且从封装部伸出壳体。第二导电区电连接第一极片。第二导电区包括连接第一导电区的第一端部，第二导电区自第一端部向第一侧延伸，从而可减小壳体盖合时对第一外极片的摩擦，进而减小第一外极片在摩擦下变形的可能性。
在一些可能的实现方式中，第一外极片包括在第一方向上叠设的第一集流体和第一活性材料层。第一集流体包括朝向第二极片的第一表面和与第一表面相背的第二表面。第一活性材料层设于第一表面，第二表面未设有活性材料。因此，可减小能量密度的浪费。
在一些可能的实现方式中，第一极片还包括第一内极片，第一内极片位于第一外极片的内侧。第一内极片包括第二集流体。在第一方向上，第一集流体的厚度为第一厚度，第二集流体的厚度为第二厚度，第一厚度与第二厚度的比值大于等于1.2且小于等于2.5。因此，位于最外层的第一外极片具有较高的强度，从而能够形成保护层，减小机械滥用时电极组件损坏的可能性，同时第一厚度相比第二厚度较大也利于减小单面涂覆的第一集流体的相对两侧张力不一致导致第一集流体容易发生卷曲、翘起的可能性。通过设置h1/h2的上限值，还减小了h1过大时对能量密度的影响。
在一些可能的实现方式中，二次电池还包括设于第二表面的第一层。第一层包含绝缘材料。第一层用于将二次电池过充时第一外极片处产生的热量进行散发，降低电极组件的温度，提高二次电池的抗过充性能。
在一些可能的实现方式中，在第一方向上，定义第一集流体的厚度为第一厚度，第一层的厚度为第三厚度，第三厚度小于两倍的第一厚度。因此，减小了第三厚度过大时第一层对二次电池能量密度的影响，也减小了第三厚度过小时第一层散热效果降低及容易被第一集流体的边缘毛刺刺穿的可能性。
在一些可能的实现方式中，第一层粘接第二表面和壳体。因此，第一层还能够将二次电池过充时第一外极片处产生的热量传导至壳体上，使得该部分热量经壳体散发至外界，改善散热效果，从而进一步提高二次电池的抗过充性能。
在一些可能的实现方式中，第一外极片包括在第一方向上叠设的第一活性材料层、第一集流体和第二活性材料层。第一集流体包括朝向第二极片的第一表面和与第一表面相背的第二表面。第一活性材料层设于第一表面，第二活性材料层设于第二表面。
在一些可能的实现方式中，第一极片为正极极片，单位面积的第一集流体上设有的活性材料的质量为G，G≤23mg/cm2。因此，可减小第一区域的活性材料脱落的可能性，也使得第一区域在制备时容易被弯曲(即，偏离第二方向延伸)。另外通过设置第一厚度和第二厚度的比值的上限值，减小了第一厚度过大的可能性，从而也使得第一区域在制备时容易被弯曲。
在一些可能的实现方式中，与第一外极片相邻的隔离膜粘接于第二区域，从而可进一步减小第一外极片和相邻的第二极片接触短路的可能性。
在一些可能的实现方式中，与第一外极片相邻的第二极片包括在第二方向上相连接的第三区域和第四区域。从第一方向观察，第一区域和第三区域存在重叠，第二区域和第四区域存在重叠。与第一外极片相邻的隔离膜还粘接于第三区域，从而可进一步减小第一外极片和相邻的第二极片接触短路的可能性。
在一些可能的实现方式中，第三区域包括在第二方向上相连接的第一分区和第二分区。从第三方向观察，第二分区包括连接第一分区的第三端。第一分区在第一方向上与第一区域存在重叠。从第一方向观察，第二分区自第三端延伸至超出第一区域。从第三方向观察，第二分区自第三端沿背离第一外极片的方向延伸。通过设置第二分区沿背离第一外极片的方向延伸，能够减小第一区域的偏离程度，从而减小第一区域对二次电池的能量密度及外观平整度的影响、第一区域的活性材料容易脱落并导致短路的可能性、第一区域难以发挥容量作用的活性材料增多的可能性。
在一些可能的实现方式中，从第二方向观察，隔离膜包括在第一方向上堆叠设置的多个主体段和多个连接相邻两个主体段的端部的连接段。主体段设于相邻的第一极片和第二极片之间。由于设置连接段，隔离膜能够对至少部分第一极片和至少部分第二极片起到束缚的作用，减小二次电池过充时第一极片和第二极片在高温气体作用下过度鼓起并断裂的可能性。
本申请第二方面还提供一种电子装置，其包括如上二次电池。电子装置通过上述二次电池供电，且二次电池具有较高的抗过充性能，因此可靠性和使用寿命得到改善。
附图说明
本申请的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：
图1为本申请一实施方式提供的二次电池从第一方向观察时的结构示意图。
图2为一些实施例中图1所示的二次电池沿II-II的剖视图。
图3为一些实施例中图1所示的二次电池沿III-III的剖视图。
图4为图3所示的二次电池于A处的局部放大图。
图5为一些实施例中图1所示的二次电池沿IV-IV的剖视图。
图6为另一些实施例中图1所示的二次电池沿II-II的剖视图。
图7一些实施例中图1所示的二次电池在封装前的结构示意图。
图8为另一些实施例中图1所示的二次电池沿III-III的剖视图。
图9为另一些实施例中图1所示的二次电池在封装前的结构示意图。
图10为图7或图9所示的二次电池的第一壳体的剖视图。
图11为图7或图9所示的二次电池的第二壳体的剖视图。
图12为另一些实施例中图1所示的二次电池沿III-III的剖视图。
图13为另一些实施例中图1所示的二次电池沿III-III的剖视图。
图14为另一些实施例中二次电池的局部放大图。
图15为图14所示的二次电池的隔离膜的剖视图。
图16为另一些实施例中二次电池的局部放大图。
图17为本申请另一实施方式提供的二次电池的剖视图。
图18为本申请另一实施方式提供的二次电池的剖视图。
图19为本申请一实施方式提供的电子装置的结构示意图。
如下具体实施方式将结合上述附图进一步说明本申请。
具体实施方式
下面对本申请实施例中的技术方案进行清楚、详细地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
下文，将详细地描述本申请的实施方式。但是，本申请可体现为许多不同的形式，并且不应解释为限于本文阐释的示例性实施方式。而是，提供这些示例性实施方式，从而使本申请透彻的和详细的向本领域技术人员传达。
另外，为了简洁和清楚，在附图中，各种组件、层的尺寸或厚度可被放大。遍及全文，相同的数值指相同的要素。如本文所使用，术语“及/或”、“以及/或者”包括一个或多个相关列举项目的任何和所有组合。另外，应当理解，当要素A被称为“连接”要素B时，要素A可直接连接至要素B，或可能存在中间要素C并且要素A和要素B可彼此间接连接。
进一步，当描述本申请的实施方式时使用“可”指“本申请的一个或多个实施方式”。
本文使用的专业术语是为了描述具体实施方式的目的并且不旨在限制本申请。如本文所使用，单数形式旨在也包括复数形式，除非上下文另外明确指出。应进一步理解，术语“包括”，当在本说明书中使用时，指存在叙述的特征、数值、步骤、操作、要素和/或组分，但是不排除存在或增加一个或多个其他特征、数值、步骤、操作、要素、组分和/或其组合。
空间相关术语，比如“上”等可在本文用于方便描述，以描述如图中阐释的一个要素或特征与另一要素(多个要素)或特征(多个特征)的关系。应理解，除了图中描述的方向之外，空间相关术语旨在包括设备或装置在使用或操作中的不同方向。例如，如果将图中的设备翻转，则描述为在其他要素或特征“上方”或“上”的要素将定向在其他要素或特征的“下方”或“下面”。因此，示例性术语“上”可包括上面和下面 的方向。应理解，尽管术语第一、第二、第三等可在本文用于描述各种要素、组分、区域、层和/或部分，但是这些要素、组分、区域、层和/或部分不应受这些术语的限制。这些术语用于区分一个要素、组分、区域、层或部分与另一要素、组分、区域、层或部分。因此，下面讨论的第一要素、组分、区域、层或部分可称为第二要素、组分、区域、层或部分，而不背离示例性实施方式的教导。
在本申请中，参数数值之间的大于、小于或不等于设计关系，需要排除测量设备的合理误差。
二次电池在过充电时，正极材料过度脱出锂离子，充电电压超过充电截止电压。一方面，正极材料与电解液容易在高压下发生氧化还原反应，大量产热并导致二次电池发生热失控，同时副反应的发生也会大量释放氧气及其它可燃性气体，引起壳体鼓胀并加剧热失控。另一方面，脱出的过量锂离子可能会囤积于负极极片表面并析出锂枝晶，锂枝晶可能会刺穿隔离膜并导致正极极片和负极极片接触短路，从而进一步加速产热。因此二次电池过充时会降低二次电池的可靠性和使用寿命。
请参阅图1至图5，本申请一实施方式提供一种二次电池100，包括壳体10、设于壳体10内的电极组件20和电解液(图未示)、第一导电板30以及第二导电板40。如图2和图3所示，电极组件20为叠片结构，其包括多个第一极片21、多个第二极片22和多个隔离膜23。叠片结构中第一极片21和第二极片22依次交替堆叠，每相邻两个第一极片21中设有一个第二极片22，每相邻两个第二极片22中设有一个第一极片21。隔离膜23设置于相邻的第一极片21和第二极片22之间，隔离膜23用于防止第一极片21和第二极片22直接接触，从而降低第一极片21和第二极片22发生接触短路的可能性。如图1和图3所示，第一导电板30电连接于第一极片21，如图1和图5所示，第二导电板40电连接于第二极片22。第一导电板30和第二导电板40均从壳体10的一端伸出，第一导电板30和第二导电板40用于连接外部设备(图未示)。
其中，根据相互垂直的第一方向X、第二方向Y和第三方向Z建立三维坐标系。在本申请实施例的说明中，第一方向X为第一极片21、隔离膜23和第二极片22的堆叠方向，如图2和图3所示，第一方向X上具有第一侧X1以及与第一侧X1相反的第二侧X2。第二方向Y为第一导电板30或第二导电板40伸出壳体10的方向，也为第一导电板30或第二导电板40凸出于电极组件20的方向。第三方向Z为自第二导电板40至第一导电板30的方向。
如图2和图3所示，定义多个第一极片21中的最外层极片分别为第一外极片21a和第二外极片21b，多个第一极片21中的内层极片为第一内极片21c。在第一方向X上，第一内极片21c设于第一外极片21a和第二外极片21b之间，第一内极片21c位于第一外极片21a的内侧。在第一方向X上，第二极片22和隔离膜23也可均位于第一外极片21a和第二外极片21b之间。第一外极片21a和第二外极片21b位于电极组件20的最外层。其中，第一侧X1为自第二极片22朝向第一外极片21a的方向，或是自第二外极片21b朝向第一外极片21a的方向。第二侧X2为自第一外极片21a朝向第二极片22的方向，或是自第一外极片21a朝向第二外极片21b的方向。
在一些实施例中，第一外极片21a和第二外极片21b分别为单面涂覆极片。第一外极片21a包括在第一方向X上叠设的第一集流体210和第一活性材料层211。第一集流体210包括朝向第二极片22的第一表面210a和与第一表面210a相背的第二表面210b。第一活性材料层211设于第一表面210a，第二表面210b未设有活性材料。第一内极片21c为双面涂覆极片。第一内极片21c包括在第一方向X上叠设的第一活性材料层211、第二集流体213和第二活性材料层212。第二外极片21b包括在第一方向X上叠设的第四集流体214和第一活性材料层211，第二外极片21b的第一活性材料层211设于第四集流体214朝向第二极片22的表面。其中，第一极片21可以是正极极片。对应地，第一集流体210、第二集流体213和第四集流体214可以均是正极集流体，第一活性材料层211和第二活性材料层212可以均是正极活性材料层。第二外极片21b的第一活性材料层211包含的活性材料可以与第一外极片21a的 第一活性材料层211包含的活性材料相同，也可以不同。第一内极片21c的第一活性材料层211或第二活性材料层212包含的活性材料可以与第一外极片21a的第一活性材料层211包含的活性材料相同，也可以不同。通过设置第一外极片21a和第二外极片21b分别为单面涂覆极片，从而减小了能量密度的浪费。当第一极片21是正极极片时，还可减少由于第二极片22未能嵌入对应的锂离子(如，当第二表面210b设有活性材料时该部分活性材料脱出的锂离子)而导致过量锂离子囤积并析锂的可能性。
请进一步参照图4，在一些实施例中，在第一方向X上，第一集流体210的厚度为第一厚度h1，第二集流体213的厚度为第二厚度h2，1.2≤h1/h2≤2.5。通过设置h1/h2的下限值，使得第一集流体210的厚度h1较大，因此位于最外层的第一外极片21a具有较高的强度，从而能够形成保护层，减小机械滥用(如挤压、针刺等)时电极组件20损坏的可能性，提高电极组件20耐机械冲击的能力。同时，第一集流体210的厚度h1相比第二集流体213的厚度h2较大，也利于减小单面涂覆的第一集流体210的相对两侧张力不一致导致第一集流体210容易发生卷曲、翘起的可能性。而且通过设置h1/h2的上限值，减小了厚度h1过大时对能量密度的影响。进一步地，也可以设置第二外极片21b的第四集流体214的厚度大于第二集流体213的厚度。
第二极片22可为双面涂覆极片。第二极片22包括堆叠设置的第三活性材料层221、第三集流体220和第四活性材料层222。第三活性材料层221隔着隔离膜23朝向第一活性材料层211设置，第四活性材料层222隔着隔离膜23朝向第二活性材料层212设置。其中，第二极片22可以是负极极片。对应地，第三集流体220可以是负极集流体，第三活性材料层221和第四活性材料层222可以均是负极活性材料层。为减小第二极片22发生析锂的可能性，第二极片22在第二方向Y上的边缘可超出第一极片21在第二方向Y上的边缘，使得第二极片22形成伸出区2200(overhang，在图3中标出)。电极组件20上可设有多个第一极耳51和多个第二极耳52。多个第一极耳51分别一体连接于第一集流体210和第二集流体213。多个第二极耳52分别一体连接于第三集流体220。第一极耳51通过转接焊工艺焊接于第一导电板30，第二极耳52通过转接焊工艺焊接于第二导电板40。
正极集流体可以采用铝箔或镍箔，负极集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。正极活性材料层包含正极活性材料，正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物(锂化插层化合物)。在一些实施例中，正极活性材料可以包括锂过渡金属复合氧化物。该锂过渡金属复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在一些实施例中，正极活性材料选自钴酸锂(LiCoO2)、锂镍锰钴三元材料(NCM)、锰酸锂(LiMn2O4)、镍锰酸锂(LiNi0.5Mn1.5O4)或磷酸铁锂(LiFePO4)中的至少一种。负极活性材料层包含负极活性材料，采用本领域已知的能够进行活性离子可逆脱嵌的负极活性材料，本申请不做限制。例如，可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属等中的一种或多种的组合。其中，石墨可选自人造石墨、天然石墨以及改性石墨中的一种或多种的组合；硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或多种的组合；锡基材料可选自单质锡、锡氧化合物、锡合金等中的一种或多种的组合。
隔离膜23为多孔结构，其包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。其中聚乙烯和聚丙烯，它们对改善短路具有良好的作用，并可以通过关断效应改善二次电池100的稳定性。
请参阅图6，在另一些实施例中，电极组件20也可以包括一个隔离膜23。隔离膜23为一体式结构，且通过正反向交替弯曲折叠的方式形成类似Z形结构。隔离膜23包括堆叠设置的多个主体段233和连接相邻两个主体段233的端部的连接段234。每一主体段233设置于相邻的第一极片21和第二极片22之间。由于设置连接段234，隔离膜23能够对至少部分第一极片21和至少部分第二极片22起到 束缚的作用，减小二次电池100过充时第一极片21和第二极片22在高温气体作用下过度鼓起并断裂的可能性。
在一些实施例中，壳体10可以为采用封装膜封装得到的包装袋，二次电池100为软包电池。如图1和图3所示，壳体10包括用于容置电极组件20的主体部11和连接主体部11的封装部12。第一导电板30和第二导电板40均从封装部12伸出壳体10。主体部11包括连接封装部12的第一端面110。在一些实施例中，从第三方向Z观察，第一端面110自封装部12向第一侧X1延伸。图7为二次电池100在封装前的结构示意图，如图7所示，壳体10包括在第一方向X上相对设置的第一壳体101和第二壳体102。第一壳体101包括相互连接的第一壳体区101a和第二壳体区101b。第二壳体区101b的三个侧边被第一壳体区101a包围。第二壳体102包括相互连接的第三壳体区102a和第四壳体区102b。第四壳体区102b的三个侧边被第三壳体区102a包围。壳体10由第一壳体101和第二壳体102封装而成。其中，第一壳体101的第二壳体区101b设有第一凹部R1，第二壳体102为平板结构。制备时，可将电极组件20放置于第一壳体101的第一凹部R1，并将第二壳体102盖合于第一壳体101。当第一壳体101和第二壳体102封装后，第一凹部R1被第一壳体101的第二壳体区101b封闭，第一壳体区101a与第三壳体区102a相连接以封装主体部11。
如图3所示，在一些实施例中，第一导电板30整体弯折设置。第一导电板30包括相连接的第一导电区31和第二导电区32。第一导电区31设于封装部12内且沿第二方向Y从封装部12伸出壳体10。第二导电区32电连接第一极片21(如，第二导电区32通过第一极耳51连接第一极片21)。第二导电区32相较于第一导电区31弯折设置。第二导电区32包括连接第一导电区31的第一端部321和与第一端部321相对设置的第二端部322，第二导电区32自第一端部321向第一侧X1延伸。因此从第二方向Y观察，第二导电区32与第一端面110存在重叠。其中，第二导电区32可沿着第一方向X延伸，也可以相较于第一方向X倾斜设置。
如图8所示，在另一些实施例中，从第三方向Z观察，第一端面110还可以包括自封装部12向第一侧X1延伸的第一部分111和自封装部12向第二侧X2延伸的第二部分112。封装部12在第一方向X上位于第一部分111和第二部分112的连接处。第一部分111在第一方向X上的长度W1小于第二部分112在第一方向X上的长度W2。如，第一部分111为壳体10的深坑面，第二部分112为壳体10的浅坑面。图9为二次电池100在封装前的结构示意图，如图9所示，此时第二壳体102的第四壳体区102b对应设有第二凹部R2。当第一壳体101和第二壳体102封装后，第二壳体区101b和第四壳体区102b共同组成用于收容电极组件20的主体部11。
如图10和图11所示，在一些实施例中，第一壳体101和第二壳体102的材料可均为多层片材。如图10所示，第一壳体101可包括依次叠设的第一保护层1011、第一金属层1012和第一聚合物层1013。相较于第一保护层1011，第一聚合物层1013更靠近电极组件20。第一保护层1011的材质可以为高分子树脂，其可以用于保护第一金属层1012，降低第一金属层1012因外力作用破损的可能性，同时能够延缓外部环境的空气渗透，维持二次电池100内部处于正常运作的环境。在一些实施例中，第一保护层1011的材质可选自对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚偏氟乙烯、聚四氟乙烯、聚丙烯、聚酰胺、聚酰亚胺中的至少一种。第一金属层1012可以用于延缓外部环境的水分渗透，并减少外力对电极组件20造成的损伤。在一些实施例中，第一金属层1012可以为铝箔层或钢箔层。第一聚合物层1013具有加热熔融的性质，可以用于封装，且可以降低多层片材被电解液中的有机溶剂溶解或溶胀的可能性。第一聚合物层1013还可用于降低电解液中的电解质与第一金属层1012接触而导致金属层被腐蚀的可能性。在一些实施例中，第一聚合物层1013包括聚合物材料，其可选自聚丙烯、丙烯共聚物、聚乙烯、聚甲基丙烯酸甲酯中的至少一种。如图11所示，第二壳体102可包括依次叠设的第二保护层1021、第二金属层1022和第二聚合物层1023。可以理解，当第一壳体101和第二壳体102可由一张封 装膜折叠后得到时，第二保护层1021、第二金属层1022和第二聚合物层1023的材质分别与第一保护层1011、第一金属层1012和第一聚合物层1013的材质完全相同，在此不作重复描述。制备壳体10时，可利用封装设备的封头同时在第一壳体区101a与第三壳体区102a处施加一定的温度和压力，使第一聚合物层1013和第二聚合物层1023相互熔融并粘合在一起，形成封装部12。
在其它实施例中，壳体10还可以为金属壳体，例如可以为钢壳或铝壳等。
如图4所示，从第三方向Z观察，第一外极片21a包括在第二方向Y上相连接的第一区域2101和第二区域2102。从第三方向Z观察，第一区域2101包括连接于第二区域2102的第一端2101a和在第二方向Y上与第一端2101a相对设置的第二端2101b。第一区域2101自第一端2101a偏离第二方向Y延伸，且第二端2101b相较于第一端2101a在第一方向X上更远离第二极片22。本申请中，可沿着第一区域2101的轮廓向外延伸形成延伸线S1，沿着第二方向Y作第二区域2102的延伸线S2，延伸线S1和延伸线S2的交点即为第一端2101a，第一端2101a可视为从第三方向Z观察时第一区域2101和第二区域2102的分界点。其中，第二端2101b在第二方向Y上与第一端2101a相对设置，并不意味着第一端2101a和第二端2101b的连线S3必须沿着第二方向Y延伸，本申请实施例的说明中，当描述第二端2101b在第二方向Y上与第一端2101a相对设置时，表示在确保达成本发明目的的前提下，第一端2101a和第二端2101b的连线S3可能偏离第二方向Y。其中，从第三方向Z观察，第二区域2102可以包括弯曲部分。结合参照图3和图4，在一些实施例中，在第二方向Y上，第一区域2101相较于第二区域2102更远离第一导电板30，从而减小了当电极组件20沿第二方向Y在壳体10内移动时(如二次电池100发生跌落或振动)第一极耳51进入第一区域2101和与第一外极片21a相邻的第二极片22之间的空间、进而导致接触短路的可能性。
如图3所示，当第一端面110自封装部12向第一侧X1延伸时，第一区域2101自第一端2101a向第一侧X1延伸。从第二方向Y观察，第一区域2101可与第一端面110存在重叠。第一外极片21a的第一区域2101至少部分置于由第一端面110所延伸形成的第一凹部R1内。从而，可减小当第二壳体102盖合于第一壳体101时对第一外极片21a的摩擦，进而减小第一外极片21a在摩擦下变形的可能性。如图8所示，当第一端面110包括自封装部12向第一侧X1延伸的第一部分111和自封装部12向第二侧X2延伸的第二部分112时，第一区域2101自第一端2101a向第一侧X1延伸。从第二方向Y观察，第一区域2101可与第一部分111存在重叠。这同样可减小当第二壳体102盖合于第一壳体101时对第一外极片21a的摩擦，进而减小第一外极片21a在摩擦下变形的可能性。
如图4所示，与第一外极片21a相邻的第二极片22包括在第二方向Y上相连接的第三区域2201和第四区域2202。从第一方向X观察，第一区域2101与第三区域2201相对设置，第一区域2101和第三区域2201存在重叠。从第一方向X观察，第二区域2102与第四区域2202相对设置，第二区域2102和第四区域2202存在重叠。因此，当二次电池100充电时，第一区域2101析出的锂离子能够嵌入第三区域2201，第二区域2102析出的锂离子能够嵌入第四区域2202。本申请中，可经过第一端2101a作平行于第一方向X的虚线S4，从第三方向Z观察时，虚线S4与第二极片22的相交处即为第三区域2201和第四区域2202的分界处。由于第一外极片21a的第一区域2101偏离第二方向Y延伸，因此在第一方向X上，第一区域2101与第三区域2201之间的距离大于第二区域2102与第四区域2202之间的距离，使得第一区域2101与第三区域2201之间的离子传输路径延长。其中，第一区域2101与第三区域2201之间的距离并非恒定值，第一区域2101的第一端2101a与第三区域2201之间的距离小于第二端2101b与第三区域2201之间的距离。在一些实施例中，第三区域2201包括在第二方向Y上相连接的第一分区2203和第二分区2204。从第三方向Z观察，第二分区2204包括连接第一分区2203的第三端2204a和与第三端2204a相对设置的第四端2204b。第一分区2203在第一方向X上与第一区域2101存在重叠。 从第一方向X观察，第二分区2204自第三端2204a延伸至超出第一区域2101，第二分区2204即为与第一外极片21a相邻的第二极片22的伸出区2200。本申请中，可在第二端2101b处沿着第一方向X作虚线S5，从第三方向Z观察时，虚线S5与第二极片22的相交处即为第三端2204a，第三端2204a也为从第三方向Z观察时第一分区2203和第二分区2204的分界点。
本发明通过设置第一外极片21a的第一区域2101偏离第二方向Y向外延伸，因此第一区域2101与第三区域2201之间的离子传输路径延长，传输阻抗增加。当二次电池100过充时，第三区域2201可作为过充时的牺牲位置优先发生析锂，从而减小了与第一外极片21a相邻的第二极片22中其它位置发生析锂的概率或析锂程度，也减小了其它第二极片22发生析锂的概率或析锂程度，减小热失控的发生。而且由于第一区域2101与第三区域2201之间的距离较大，第三区域2201析出的锂枝晶即便刺穿隔离膜23后与第一区域2101接触的可能性降低，因此降低了锂枝晶与第一外极片21a接触短路的可能性。此外，二次电池100过充时若第一区域2101附近产气，相邻的第一外极片21a、隔离膜23以及第二极片22的接触界面可在气体作用下被撑开，这有利于进一步降低第三区域2201析出的锂枝晶和第一外极片21a接触短路的可能性，也有利于电极组件20内的热量及时散发。因此，本申请可提高二次电池100的抗过充性能，从而提高二次电池100的可靠性和使用寿命。请参阅图13，在一些实施例中，为了进一步提高二次电池100的抗过充性能，还可以设置第二外极片21b具有与第一外极片21a相同的结构，如，在第二外极片21b上设置偏离第二方向Y向外延伸的区域。
请参阅图12，在另一些实施例中，在第二方向Y上，也可以设置第一区域2101相较于第二区域2102更靠近第一导电板30。由于第一端面110和电极组件20之间具有一定的空间以收容第一极耳51和部分第一导电板30，通过设置第一区域2101更靠近第一导电板30，因此当二次电池100过充时有利于第一区域2101附近产生的气体释放至上述空间内，减小过量气体聚集并导致第一区域2101进一步偏离第二方向Y的可能性，从而减小了第一区域2101偏离程度较大时对二次电池100的能量密度及外观平整度造成的影响，也减小了第一区域2101的活性材料容易脱落并导致短路的可能性，同时也减小了第一区域2101难以发挥容量作用的活性材料相应增多的可能性。
在一些实施例中，单位面积的第一集流体210上设有的活性材料的质量为G(即单位面积的第一活性材料层211的重量为G)，G≤23mg/cm2。因此，可减小第一区域2101的活性材料脱落的可能性，也使得第一外极片21a的第一区域2101在制备时容易被弯曲(即，偏离第二方向Y延伸)。另外可以理解，当设置h1/h2的上限值时，能够减小厚度h1过大的可能性，从而也使得第一外极片21a的第一区域2101在制备时容易被弯曲。其中，G的测量步骤可以是：(1)将二次电池100以0.2C放电至2.75V，拆解二次电池100，清洗、烘干；(2)使用天平对一定面积A的第一外极片21a进行称重，重量记为G1；(3)使用溶剂洗掉第一外极片21a的第一集流体210上的活性材料，烘干，测量第一集流体210的重量，记为G2；(4)通过下式计算G：G＝(G1-G2)/A。
如图4所示，在一些实施例中，从第三方向Z观察，第一端2101a和第二端2101b的连线S3与第二方向Y之间的夹角α满足：1°≤α≤12°。通过限定夹角α的下限值，可使得第一区域2101相较于第二方向Y偏离一定的范围，从而延长第一区域2101与第三区域2201之间的离子传输路径，使得二次电池100过充时第三区域2201可作为过充时的牺牲位置优先发生析锂，而且第一区域2101相较于第二方向Y偏离一定的范围也减小了第三区域2201析出的锂枝晶与第一区域2101接触的可能性。通过限定夹角α的上限值，减小了第一区域2101偏离程度较大时对二次电池100的能量密度及外观平整度的影响，也减小了第一区域2101偏离程度较大时第一区域2101的活性材料容易脱落并导致短路的可能性，也减小了第一区域2101偏离程度较大时第一区域2101难以发挥容量作用的活性材料增多的可能性。
进一步地，在一些实施例中，3°≤α≤10°。通过进一步通限定夹角α的下限值，从而进一步延长第一区域2101与第三区域2201之间的离子传输路径，使得二次电池100过充时第三区域2201可作为过充时的牺牲位置优先发生析锂，而且也进一步减小了第三区域2201析出的锂枝晶与第一区域2101接触的可能性。通过进一步限定夹角α的上限值，从而进一步减小了第一区域2101对二次电池100的能量密度及外观平整度的影响，也进一步减小了第一区域2101的活性材料容易脱落并导致短路的可能性，也进一步减小了第一区域2101难以发挥容量作用的活性材料增多的可能性。
其中，α的测量步骤可以是：(1)采用X射线从第三方向Z对二次电池100进行二维投影和扫描测试，仪器可以采用本领域技术人员公知的仪器或设备(例如GE Phoenixvtomex S设备)，从而获得CT图；(2)采用卡尺或其它合适的量具直接测量α的数值。
α的测量步骤还可以是：(1)将二次电池100以0.2C放电至2.75V；(2)配置树脂组合物，其由水晶胶树脂基体(如环氧树脂)、催化剂及固化剂按照一定比例调配而成；(3)将树脂组合物倒入模具中，并将二次电池100的壳体10切开后倾斜地置于模具中，以减少二次电池100底部可能残存的气泡，再继续缓慢倒入树脂组合物，使得将二次电池100完全浸没于树脂组合物中，使得树脂组合物通过壳体10的切口缓慢流入壳体10内；(4)将二次电池100调整至位置水平，将多余的气泡排出，然后静置至树脂组合物凝固；(5)沿垂直于第三方向Z的截面切割二次电池100并对切割面进行打磨，从而得到二次电池100的横截面；(6)在横截面上标注第一端2101a和第二端2101b的连线S3与第二方向Y之间的夹角α，并采用卡尺或其它合适的量具直接测量α的数值。
在一些实施例中，如图4所示，从第三方向Z观察，第一区域2101自第一端2101a延伸至第二端2101b的长度为第一长度L1(当第一区域2101包括弯曲部分时，L1指的是第一区域2101的弧长)，如图3所示，第二区域2102在第二方向Y上的长度为第二长度L2，7≤L2/L1≤29。通过限定L2/L1的下限值，减小了上述比值过小时(如长度L1过大，导致第一区域2101偏离程度较大)第一区域2101对二次电池100的能量密度及外观平整度的影响，也减小了第一区域2101难以发挥容量作用的活性材料增多的可能性。通过限定L2/L1的上限值，减小了上述比值过大时(如长度L1过小，第一区域2101面积过小)第三区域2201在过充时未能显著减小其它位置发生析锂的概率或析锂程度的可能性。
进一步地，在一些实施例中，11≤L2/L1≤19，从而进一步减小了第一区域2101对二次电池100的能量密度及外观平整度的影响，进一步减小了第一区域2101中难以发挥容量作用的活性材料增多的可能性，也进一步减小了第三区域2201在过充时未能显著减小其它位置发生析锂的概率或析锂程度的可能性。其中，可采用与夹角α相似的测量步骤测量长度L1、L2。
如图14所示，在另一些实施例中，二次电池100还可包括设于第二表面210b的包含绝缘材料的第一层60。第一层60用于将二次电池100过充时第一外极片21a处产生的热量进行散发，降低了电极组件20的温度，提高了二次电池100的抗过充性能。当第一极片21为负极极片且壳体10的金属层为铝箔层时，第一层60还可隔绝第一集流体210和壳体10，从而降低第一集流体210的边缘毛刺(上述毛刺可以在第一集流体210裁切时产生，但本申请并不作限制)刺穿壳体10的聚合物层并与铝箔层发生接触短路、导致二次电池100大量产热的可能性，也可降低第一外极片21a在充电过程中脱出的锂离子在第一集流体210与铝箔层接触处发生反应生成铝锂合金(AlLi)并导致铝箔层腐蚀的可能性。其中，第一层60的绝缘材料可以选自无机陶瓷材料和粘结剂中的至少一种。无机陶瓷材料包括二氧化铪、钛酸锶、二氧化锡、氧化铯、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、氧化钇、三氧化二铝、氧化钛、二氧化硅、勃姆石、氢氧化镁或氢氧化铝中的至少一种。粘结剂可以选自丁苯橡胶、聚丙烯、聚丙烯酸、丙烯酸酯及其衍生物、聚乙烯醇、天然橡胶或改性橡胶中的至少一种。其中，第一层60具 体可以为单面胶、双面胶或热熔胶，第一层60可粘接于第二表面210b并覆盖整个第二表面210b。另一些实施例中，第一层60在第二表面210b上可呈点状、条状或其它不规则形状分布。
在一些实施例中，在第一方向X上，定义第一集流体210的厚度为第一厚度h1，第一层60的厚度为第三厚度h3，h3<2h1。因此，减小了厚度h3过大时第一层60对二次电池100能量密度的影响，也减小了厚度h3过小时第一层60散热效果降低及容易被第一集流体210的边缘毛刺刺穿的可能性。
在一些实施例中，第一层60具体可以为双面胶或热熔胶，粘接第二表面210b和壳体10。因此，第一层60还能够将二次电池100过充时第一外极片21a处产生的热量传导至壳体10上，使得该部分热量经壳体10散发至外界，改善散热效果，从而进一步提高二次电池100的抗过充性能。
如图4或图14所示，在一些实施例中，与第一外极片21a相邻的隔离膜23粘接于第二区域2102，从而可进一步减小第一外极片21a和相邻的第二极片22接触短路的可能性。请参照图15，在一些具体的实施例中，隔离膜23可包括在第一方向X上叠设的第一粘接层231、基层230和第二粘接层232，第一粘接层231、基层230和第二粘接层232均为多孔结构。隔离膜23通过第一粘接层231粘接于第二区域2102。基层230可选自聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。第一粘接层231和第二粘接层232分别包括粘接剂，粘接剂包括由聚合物单体形成的均聚物或共聚物，聚合物单体包括偏二氟乙烯、六氟丙烯、丙烯酸、丙烯酸酯、丁二烯、苯乙烯、丙烯腈、乙烯、氯苯乙烯、氟苯乙烯或丙烯中的至少一种。
在一些实施例中，与第一外极片21a相邻的隔离膜23还可粘接于第三区域2201，如，与第一外极片21a相邻的隔离膜23通过第二粘接层232粘接于第三区域2201，从而可进一步减小第一外极片21a和相邻的第二极片22接触短路的可能性。可以理解，二次电池100过充时若第一区域2101附近产气，由于隔离膜23为多孔结构，上述气体可以通过隔离膜23并撑开相邻的第一外极片21a、隔离膜23以及第二极片22的接触界面，从而降低第三区域2201析出的锂枝晶和第一外极片21a接触短路的可能性，也有利于电极组件20内的热量及时散发。
请参阅图16，在另一些实施例中，从第三方向Z观察，第二分区2204自第三端2204a沿背离第一外极片21a的方向延伸。第二分区2204的延伸方向相较于第二方向Y倾斜设置。通过设置第二分区2204自第三端2204a沿背离第一外极片21a的方向延伸，也可使得第三区域2201与第一区域2101之间的离子传输路径延长，因此能够减小第一区域2101的偏离程度，从而减小第一区域2101偏离程度较大时对二次电池100的能量密度及外观平整度的影响，也减小了第一区域2101偏离程度较大时第一区域2101的活性材料容易脱落并导致短路的可能性，还减小了第一区域2101偏离程度较大时第一区域2101难以发挥容量作用的活性材料增多的可能性。
请参阅图17，在另一些实施例中，也可以设置第一极片21为负极极片，第二极片22为正极极片。此时由于第一区域2101与第三区域2201之间的离子传输路径延长，当二次电池100过充时，第一区域2101可作为过充时的牺牲位置优先发生析锂，从而减小了与第一外极片21a其它位置发生析锂的可能性或析锂程度，也减小了处第一外极片21a外其它第一极片21发生析锂的可能性或析锂程度。而且由于第一区域2101与第三区域2201之间的距离较大，第一区域2101析出的锂枝晶即便刺穿隔离膜23后与第三区域2201接触的可能性降低，因此降低了锂枝晶与第三区域2201接触短路的可能性。
请参阅图18，在另一些实施例中，第一外极片21a还可以为双面涂覆极片。第一外极片21a包括在第一方向X上叠设的第一活性材料层211、第一集流体210和第二活性材料层212。第一集流体210包括朝向第二极片22的第一表面210a和与第一表面210a相背的第二表面210b。第一活性材料层211设于第一表面210a，第二活性材料层212设于第二表面210b。此时，单位面积的第一集流体210上设有的活性材料的质量为G，G≤23mg/cm2，具体指的是单位面积的第一集流体210上设有的第一活性材 料层211和第二活性材料层212的总质量小于23mg/cm2。
其中，本申请的二次电池100可以为锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池和锂离子聚合物二次电池。
请参阅图19，本申请一实施方式还提供一种电子装置1，包括上述二次电池100。电子装置1通过上述二次电池100供电，且二次电池100具有较高的抗过充性能。在一实施方式中，本申请的电子装置1可以是，但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
以下通过具体实施例和对比例对本申请作详细说明。其中，以二次电池100为软包锂离子二次电池为例并结合具体测试方法对本申请进行说明。本领域技术人员应理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例1-14
第一极片21的制备：将活性材料钴酸锂(LiCoO2)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为12μm的铝箔的一个表面上，在铝箔边缘预留空箔区。90℃条件下烘干，得到厚度为100μm的活性材料层，该单面涂覆的第一极片21后续分别作为第一外极片21a和第二外极片21b。当制备双面涂覆的其它第一极片21时，在铝箔的另一个表面上重复以上步骤。然后，通过激光模切成型切除多余的空箔区，得到第一极耳51。
第二极片22的制备：将负极活性材料人造石墨、导电炭黑(Super P)、丁苯橡胶(SBR)按照重量比96:1.5:2.5进行混合，加入去离子水作为溶剂，调配成固含量为70wt％的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为10μm的铜箔的一个表面上，在铜箔边缘预留空箔区。110℃条件下烘干，得到厚度为150μm的活性材料层。在箔的另一个表面上重复以上步骤。然后，通过激光模切成型切除多余的空箔区，得到第二极耳52。
电解液的制备：在干燥氩气气氛中，首先将有机溶剂碳酸乙烯酯(EC)和碳酸二乙酯(DEC)以质量比1:1混合，然后向有机溶剂中加入质量分数为5％的氟代碳酸乙烯酯(FEC)、质量分数为5％的1,3-丙磺酸内酯(PS)、以及锂盐六氟磷酸锂(LiPF6)溶解并混合均匀，得到锂盐浓度为1mol/L的电解液。
电极组件20的制备：将除第一外极片21a之外的第一极片21、隔离膜23和第二极片22依次层叠，隔离膜23选用厚度为15μm的聚乙烯(PE)膜，将层叠后得到的结构在温度为60℃、压力为1Mpa的条件下通过平板热压10s。然后将第一外极片21a和第二外极片21b分别层叠于上述结构的相对两侧，然后通过弧形辊在温度为150℃的条件下对第一外极片21a需弯折的位置加热60s，使得第一区域2101偏离第二方向Y向外弯折，弯折相关参数记录于表1和表2中，通过调节弧形辊的温度和加热时间可控制夹角α、L2/L1等数值。在第一外极片21a的第二区域2102在温度为60℃、压力为1Mpa的条件下通过平板热压10s，从而使第二区域2102与隔离膜23粘接。通过相似的步骤对第二外极片21b进行热压处理。
二次电池100的组装：将第一极耳51和第二极耳52通过转接焊分别焊接至第一导电板30和第二导电板40，第一导电板30材质为铝，第二导电板40材质为镍。将冲坑成型的铝塑膜(厚度为150μm)置于组装夹具内，坑面朝上，将电极组件20置于坑内，铝塑膜的坑内注入电解液，并将第一导电板30和第二导电板40引出铝塑膜外。利用异形封头在铝塑膜的边缘处加压以形成封装部12，然后将再进行注 液、化成、封装，制成电池。
对比例
与实施例1不同之处在于，最外层的第一极片21未向外弯折。
对各个实施例和对比例的电池各取20个分别进行过充测试和能量密度测试。
过充测试的测试步骤包括：1)将电池在25℃下以0.5C恒流充电至4.48V，在恒压充电至0.05C；2)在电池外包覆厚度为10mm的白色泡棉后(泡棉需将电池全部表面包覆)，将电池置入过充过放测试机(厂商：Arbin，型号：BT-ML-30V15A)，再将电池以1C恒流充电至18.5V，恒压充电2h；3)监控过充过充中电池的开路电压和温度等变化，过充结束后测量电池的重量，并观察电池是否发生冒烟、起火等现象，若未发生则为通过，然后统计通过测试的电池的数量，结果记录于表1中。
能量密度的测试步骤包括：1)将电池在25℃环境下，以0.5C的恒流充电至4.4V，再以4.4V恒压充电至0.025C，静置5min，以0.1C的放电速率放电至3.0V，静置5min，测定0.1C放电容量C。充放电步骤完成后，测试电池的长L、宽W和厚H。则电池能量密度＝C/(L×W×H)。测试结果记录于表2中。
表1
注：过充通过率X/20表示测试的20个样品中，通过测试的个数为X个。
由表1数据可知，相较于对比例，实施例1通过设置第一外极片21a的第一区域2101偏离第二方向Y向外弯折，因此过充通过率得到改善。
表2
由表2数据可知，在实施例1-8中，实施例1、4-6满足3°≤α≤10°，因此过充通过率和能量密度均较高；实施例2的夹角α较小，因此二次电池100过充时第三区域2201未优先发生析锂，且第三区域2201析出的锂枝晶与第一区域2101接触的可能性提高，因此过充通过率相对降低；实施例7-8的夹角α较大，因此能量密度降低。
在实施例4、9-14中，实施例4、10-13满足7≤L2/L1≤29，因此过充通过率和能量密度均较高；实施例14的L2/L1比值较大，因此二次电池100过充时第三区域2201未优先发生析锂，因此过充通过率相对降低；实施例9的L2/L1比值较小，因此能量密度降低。
以上所揭露的仅为本申请较佳实施方式而已，当然不能以此来限定本申请，因此依本申请所作的等 同变化，仍属本申请所涵盖的范围。

Claims (22)

  1. 一种二次电池，包括壳体、设于所述壳体内的电极组件、以及第一导电板，所述电极组件为叠片结构，所述电极组件包括在第一方向上依次叠设的第一极片、隔离膜和第二极片，所述第一导电板连接于所述第一极片，所述第一导电板沿与所述第一方向垂直的第二方向从所述壳体伸出，其特征在于，
    所述第一极片中包括第一外极片，所述第一外极片为所述电极组件的最外层，从与所述第一方向和所述第二方向均垂直的第三方向观察，所述第一外极片包括在所述第二方向上相连接的第一区域和第二区域；
    从所述第三方向观察，所述第一区域包括连接于所述第二区域的第一端和在所述第二方向上与所述第一端相对设置的第二端，所述第一区域自所述第一端偏离所述第二方向延伸，且所述第二端相较于所述第一端在所述第一方向上更远离所述第二极片。
  2. 如权利要求1所述的二次电池，其特征在于，从所述第三方向观察，所述第一端和所述第二端的连线与所述第二方向之间的夹角α满足：1°≤α≤12°。
  3. 如权利要求2所述的二次电池，其特征在于，3°≤α≤10°。
  4. 如权利要求1所述的二次电池，其特征在于，从所述第三方向观察，所述第一区域自所述第一端延伸至所述第二端的长度为第一长度，所述第二区域在所述第二方向上的长度为第二长度，所述第二长度与所述第一长度的比值大于等于7且小于等于29。
  5. 如权利要求4所述的二次电池，其特征在于，所述第二长度与所述第一长度的比值大于等于11且小于等于19。
  6. 如权利要求1所述的二次电池，其特征在于，在所述第二方向上，所述第一区域相较于所述第二区域更远离所述第一导电板。
  7. 如权利要求1所述的二次电池，其特征在于，在所述第二方向上，所述第一区域相较于所述第二区域更靠近所述第一导电板。
  8. 如权利要求1所述的二次电池，其特征在于，所述第一方向具有自所述第二极片朝向所述第一外极片的第一侧；所述壳体为包装袋且包括用于容置所述电极组件的主体部和连接所述主体部的封装部，所述第一导电板从所述封装部伸出所述壳体；所述主体部包括连接所述封装部的第一端面，从所述第三方向观察，所述第一端面自所述封装部向所述第一侧延伸；从所述第三方向观察，所述第一区域自所述第一端向所述第一侧延伸。
  9. 如权利要求1所述的二次电池，其特征在于，所述第一方向具有自所述第二极片朝向所述第一外极片的第一侧和与所述第一侧相背的第二侧；所述壳体为包装袋且包括用于容置所述电极组件的主体部和连接所述主体部的封装部，所述第一导电板从所述封装部伸出所述壳体；所述主体部包括连接所述封装部的第一端面，从所述第三方向观察，所述第一端面包括自所述封装部向所述第一侧延伸的第一部分和自所述封装部向所述第二侧延伸的第二部分，所述第一部分在所述第一方向上的长度大于所述第二部分在所述第一方向上的长度；从所述第三方向观察，所述第一区域自所述第一端向所述第一侧延伸。
  10. 如权利要求1所述的二次电池，其特征在于，所述第一方向具有自所述第二极片朝向所述第一外极片的第一侧；所述壳体为包装袋且包括用于容置所述电极组件的主体部和连接所述主体部的封装部；所述第一导电板包括相连接的第一导电区和第二导电区，所述第一导电区设于所述封装部内且从所述封装部伸出所述壳体，所述第二导电区电连接所述第一极片，所述第二导电区包括连接所述第一导电区的第一端部，所述第二导电区自所述第一端部向所述第一侧延伸。
  11. 如权利要求1所述的二次电池，其特征在于，所述第一外极片包括在所述第一方向上叠设的第一集流体和第一活性材料层，所述第一集流体包括朝向所述第二极片的第一表面和与所述第一表面相背的第二表面，所述第一活性材料层设于所述第一表面，所述第二表面未设有活性材料。
  12. 如权利要求11所述的二次电池，其特征在于，所述第一极片还包括第一内极片，所述第一内极片位于所述第一外极片的内侧，所述第一内极片包括第二集流体，在所述第一方向上，所述第一集流体的厚度为第一厚度，所述第二集流体的厚度为第二厚度，所述第一厚度与所述第二厚度的比值大于等于1.2且小于等于2.5。
  13. 如权利要求11所述的二次电池，其特征在于，所述二次电池还包括设于所述第二表面的第一层，所述第一层包含绝缘材料。
  14. 如权利要求13所述的二次电池，其特征在于，在所述第一方向上，定义所述第一集流体的厚度为第一厚度，所述第一层的厚度为第三厚度，所述第三厚度小于两倍的所述第一厚度。
  15. 如权利要求13所述的二次电池，其特征在于，所述第一层粘接所述第二表面和所述壳体。
  16. 如权利要求1所述的二次电池，其特征在于，所述第一外极片包括在所述第一方向上叠设的第一活性材料层、第一集流体和第二活性材料层，所述第一集流体包括朝向所述第二极片的第一表面和与所述第一表面相背的第二表面，所述第一活性材料层设于所述第一表面，所述第二活性材料层设于所述第二表面。
  17. 如权利要求11或16所述的二次电池，其特征在于，所述第一极片为正极极片，单位面积的所述第一集流体上设有的活性材料的质量为G，G≤23mg/cm2。
  18. 如权利要求1所述的二次电池，其特征在于，与所述第一外极片相邻的所述隔离膜粘接于所述第二区域。
  19. 如权利要求18所述的二次电池，其特征在于，与所述第一外极片相邻的所述第二极片包括在所述第二方向上相连接的第三区域和第四区域，从所述第一方向观察，所述第一区域和所述第三区域存在重叠，所述第二区域和所述第四区域存在重叠；与所述第一外极片相邻的所述隔离膜还粘接于所述第三区域。
  20. 如权利要求19所述的二次电池，其特征在于，所述第三区域包括在所述第二方向上相连接的第一分区和第二分区，从所述第三方向观察，所述第二分区包括连接所述第一分区的第三端；所述第一分区在所述第一方向上与所述第一区域存在重叠，从所述第一方向观察，第二分区自所述第三端延伸至超出所述第一区域；从所述第三方向观察，所述第二分区自所述第三端沿背离所述第一外极片的方向延伸。
  21. 如权利要求1所述的二次电池，其特征在于，从所述第二方向观察，所述隔离膜包括在所述第一方向上堆叠设置的多个主体段和多个连接相邻两个所述主体段的端部的连接段，所述主体段设于相邻的所述第一极片和所述第二极片之间。
  22. 一种电子装置，其特征在于，包括如权利要求1至21中任一项所述的二次电池。
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Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116544345B (zh) * 2023-06-28 2023-09-19 宁德新能源科技有限公司 二次电池及电子装置
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WO2025076648A1 (zh) * 2023-10-08 2025-04-17 东莞新能源科技有限公司 二次电池和电子装置
CN120858475A (zh) * 2023-12-29 2025-10-28 宁德新能源科技有限公司 二次电池及电子装置
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20190363402A1 (en) * 2017-04-07 2019-11-28 Murata Manufacturing Co., Ltd. Secondary battery and method of manufacturing the same
CN113097430A (zh) * 2021-03-30 2021-07-09 宁德新能源科技有限公司 电化学装置及电子装置
CN113728486A (zh) * 2021-02-09 2021-11-30 宁德新能源科技有限公司 电化学装置和电子装置
CN115668595A (zh) * 2021-12-22 2023-01-31 东莞新能源科技有限公司 电化学装置和电子装置
CN115843399A (zh) * 2021-12-29 2023-03-24 东莞新能源科技有限公司 电化学装置和电子装置
WO2023108558A1 (zh) * 2021-12-16 2023-06-22 东莞新能源科技有限公司 电池及电子设备
CN116544345A (zh) * 2023-06-28 2023-08-04 宁德新能源科技有限公司 二次电池及电子装置

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6295912B2 (ja) * 2014-10-02 2018-03-20 トヨタ自動車株式会社 非水電解液二次電池およびその製造方法
CN204857872U (zh) * 2015-08-05 2015-12-09 宁德新能源科技有限公司 锂离子电池
WO2022061851A1 (zh) * 2020-09-28 2022-03-31 宁德新能源科技有限公司 电池
CN113437443B (zh) * 2021-06-21 2023-06-20 东莞新能安科技有限公司 电化学装置和电子装置
WO2023082181A1 (zh) * 2021-11-12 2023-05-19 宁德新能源科技有限公司 电化学装置及包括其的电子装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20190363402A1 (en) * 2017-04-07 2019-11-28 Murata Manufacturing Co., Ltd. Secondary battery and method of manufacturing the same
CN113728486A (zh) * 2021-02-09 2021-11-30 宁德新能源科技有限公司 电化学装置和电子装置
CN113097430A (zh) * 2021-03-30 2021-07-09 宁德新能源科技有限公司 电化学装置及电子装置
WO2023108558A1 (zh) * 2021-12-16 2023-06-22 东莞新能源科技有限公司 电池及电子设备
CN115668595A (zh) * 2021-12-22 2023-01-31 东莞新能源科技有限公司 电化学装置和电子装置
CN115843399A (zh) * 2021-12-29 2023-03-24 东莞新能源科技有限公司 电化学装置和电子装置
CN116544345A (zh) * 2023-06-28 2023-08-04 宁德新能源科技有限公司 二次电池及电子装置

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