WO2022001987A1 - 二次电池和终端 - Google Patents

二次电池和终端 Download PDF

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Publication number
WO2022001987A1
WO2022001987A1 PCT/CN2021/102850 CN2021102850W WO2022001987A1 WO 2022001987 A1 WO2022001987 A1 WO 2022001987A1 CN 2021102850 W CN2021102850 W CN 2021102850W WO 2022001987 A1 WO2022001987 A1 WO 2022001987A1
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Prior art keywords
elongation
separator
secondary battery
active material
ratio
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PCT/CN2021/102850
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English (en)
French (fr)
Inventor
李政杰
邓耀明
张新枝
高云雷
阳东方
洪达
谢封超
Original Assignee
华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP21834251.7A priority Critical patent/EP4170809A1/en
Publication of WO2022001987A1 publication Critical patent/WO2022001987A1/zh
Priority to US18/145,749 priority patent/US20230163417A1/en

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    • H—ELECTRICITY
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    • 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
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
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    • H01M10/052—Li-accumulators
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
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    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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    • 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 technical field of secondary batteries, and in particular, to a secondary battery and a terminal.
  • the heat generation power at the short-circuit point is the largest at this time, and the temperature rises rapidly. The risk of thermal runaway is highest.
  • the secondary battery is usually composed of battery cell components (positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector) by stacking or winding, in the process of foreign matter piercing until piercing the battery
  • battery cell components positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector
  • the various debris generated by the damage are often in random contact, which is more prone to internal short circuit, and at the same time, the internal short circuit releases heat and easily causes a thermal runaway chain reaction. Therefore, it is necessary to provide a high-safety secondary battery that minimizes or avoids the occurrence of the above-mentioned internal short circuit and improves the safety performance of the battery.
  • the embodiment of the present application provides a secondary battery.
  • the secondary battery can reduce or avoid the occurrence of internal short circuits when subjected to mechanical abuse, Improve battery safety performance.
  • a first aspect of the embodiments of the present application provides a secondary battery, including at least one battery cell assembly, wherein the battery cell assembly includes a positive pole piece, a negative pole piece, and a secondary battery disposed on the positive pole piece and the negative pole piece
  • the separator between the two, the positive electrode and the negative electrode both include a current collector and an active material layer arranged on the current collector; wherein, the elongation of the separator is greater than 100%, and the extension of the separator
  • the ratio includes the elongation in the MD direction (Machine Direction, that is, the longitudinal direction, the length direction) and/or the elongation in the TD direction (Transverse Direction, which is perpendicular to the machine direction, that is, the transverse direction, the width direction).
  • the ratio of the elongation to the thickness of the active material layer of the positive electrode and/or the negative electrode is 3.0%/ ⁇ m ⁇ 8.0%/ ⁇ m, and the elongation of the separator is the same as that of the positive electrode and/or the negative electrode.
  • the ratio of the elongation ratios of the current collectors of the sheet is greater than or equal to 60.
  • the secondary battery of the present application selects a separator with a higher elongation rate and reasonably designs the current collector elongation rate, the elongation rate of the separator and the thickness of the active material layer.
  • the separator When the secondary battery is pierced by needle-shaped conductors or other foreign objects, Compared with the current collector and the active material layer, the separator has a higher elongation rate, which can effectively stretch and elongate, and realizes the wrapping of needle-like conductors, other foreign objects, and the debris of the current collector and the active material layer generated by the destruction, avoiding the positive and negative electrode collectors.
  • the contact between the fluid and the positive and negative active materials and their debris leads to internal short circuits, which greatly reduces the probability of internal short circuits, avoids thermal runaway chain reactions from the source, and improves battery safety performance.
  • the secondary battery can obtain high safety performance under the premise of high energy density of the battery.
  • the elongation ratio of the separator in the battery cell assembly is greater than 100%, and the elongation ratio of the separator includes the elongation ratio along the length direction and/or along the width direction
  • the elongation rate in the direction, the ratio of the elongation rate of the separator to the thickness of the active material layer of the positive electrode sheet and/or the negative electrode sheet is 3.0%/ ⁇ m ⁇ 8.0%/ ⁇ m, and the elongation rate of the separator is proportional to the thickness of the active material layer.
  • the ratio of the elongation ratio of the current collector of the positive pole piece and/or the negative pole piece is greater than or equal to 60.
  • the secondary battery when the secondary battery includes a plurality of stacked battery cell assemblies, at least the positive electrode and/or the negative electrode and the separator in the outermost battery cell assembly of the secondary battery are as described above. configuration.
  • the positive pole piece and/or the negative pole piece and the separator in two or more battery cell assemblies may also be processed in the above manner. configuration.
  • the positive electrode sheets and/or negative electrode sheets and separators in the plurality of battery cell assemblies may also be configured such that: the elongation of the separator is greater than 100%, and the The elongation includes the elongation in the length direction and/or the elongation in the width direction, the ratio of the elongation of the separator to the thickness of the active material layer is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the separator has an elongation of 3.0%/ ⁇ m to 8.0%/ ⁇ m.
  • the ratio of the elongation to the elongation of the current collector is greater than or equal to 60.
  • a plurality of stacked battery cell assemblies may be included along the thickness of the battery.
  • the positive pole pieces and/or negative pole pieces and separators in more battery cell components are configured in the above manner, which can further improve the safety performance of the battery.
  • the ratio of the elongation of the separator to the thickness of the active material layer is 4.0%/ ⁇ m ⁇ 6.0%/ ⁇ m.
  • the suitable ratio of the elongation of the separator to the thickness of the active material layer enables the separator to stretch to a certain length when the battery is pierced by foreign objects, so that the foreign objects and various debris can be well wrapped to reduce or avoid the occurrence of internal short circuits; At the same time, an ideal energy density can also be obtained, thereby effectively taking into account the battery safety performance and high energy density.
  • the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 70. In other embodiments of the present application, the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 90.
  • the ratio of the elongation ratio of the separator to the elongation ratio of the current collector is controlled at a high ratio, so that when the battery is penetrated by foreign objects, the separator can be stretched to a certain length, and the foreign objects and various debris can be well wrapped. Reduce or avoid the occurrence of internal short circuits; at the same time, it can also reduce the generation of current collector debris to a certain extent.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector;
  • the negative electrode electrode sheet includes a negative electrode current collector and a negative electrode disposed on the negative electrode current collector active material layer.
  • the positive current collector, the positive active material layer and the separator in the positive electrode sheet are configured as described above, that is, the elongation of the separator is greater than 100%, and the elongation of the separator includes the elongation along the length direction and/or Or the elongation in the width direction, the ratio of the elongation of the separator to the thickness of the active material layer is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60.
  • the safety performance of the battery can be significantly improved by rationally designing the positive electrode and the separator.
  • the negative electrode current collector, the negative electrode active material layer and the separator in the negative electrode pole piece are configured in the above manner, which can improve the safety performance of the battery to a certain extent.
  • the positive electrode current collector, the positive active material layer and the separator in the positive electrode sheet can also be configured as described above, while the negative electrode current collector, the negative electrode active material layer and the separator in the negative electrode sheet are also The configuration is performed in the above manner. In this embodiment, both the positive electrode and the negative electrode are reasonably designed, which can better improve the safety performance of the battery.
  • the elongation of the separator is greater than or equal to 120%. In other embodiments of the present application, the elongation of the separator is greater than or equal to 150%. The higher the elongation of the separator, the more beneficial it is to protect the battery when the battery is damaged by mechanical external forces, such as foreign objects, to relieve internal short circuits, block thermal runaway in advance, and improve battery safety performance.
  • the material of the separator is various separator materials that can satisfy the secondary battery system
  • the material of the separator includes polyethylene, polyalphaolefin, polypropylene, polyethylene terephthalate, polymethyl methacrylate Pentene, polybutene, polyimide, polyamide, polyester, polyurethane, polycarbonate, cycloolefin copolymer, polybenzimidazole, polybenzobisoxazole, aramid, polyvinylidene fluoride, One or more of polytetrafluoroethylene, poly(vinylidene fluoride-hexafluoropropylene), polyetherimide, polyvinyl alcohol, and copolymers, blends, mixtures, compositions of the foregoing polymers .
  • the thickness of the separator is 1 ⁇ m-12 ⁇ m.
  • the above-mentioned reasonable design of the current collector elongation, the elongation of the separator and the thickness of the active material layer does not need to increase the thickness of the separator and sacrifice the energy density of the battery to improve the safety of the battery. Reducing the volume ratio of inactive auxiliary materials is conducive to improving the energy density of the battery.
  • the secondary battery is usually a stacked structure of a plurality of battery cell components consisting of a positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector, forming a laminated battery or winding type battery.
  • the secondary battery may include a positive electrode current collector-positive electrode active material layer-separator-negative electrode active material layer-negative electrode current collector-negative electrode active material layer-separator-positive electrode active material layer-positive electrode current collector.
  • the active material layer includes an active material and a binder and a conductive agent distributed in the active material.
  • the mass percentages of the active material, the binder and the conductive agent may be 80%-98.5%: 0.5%-5%: 1.0%-15%.
  • the current collector includes a metal foil or a metal foil with a functional coating on the surface.
  • the metal foil is, for example, aluminum foil, copper foil, titanium foil, or the like.
  • the functional coating may include a functional material and a conductive agent, and the functional material may specifically be one or more of an active ion supplement, a flame retardant, and an expansion-releasing agent.
  • the functional coating includes functional materials including lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium-rich manganese base, artificial graphite, natural graphite, hard carbon, soft carbon, mesocarbon microspheres, Carbon Nanotubes, Graphene, Carbon Fiber, Vapor Growth Carbon Fiber, Activated Carbon, Porous Carbon, Acetylene Black, Ketjen Black, Conductive Ink, Thermally Expandable Microspheres, Polyethylene, Polyamide, Polybutadiene, Ethylene Ethyl Acrylate, Ethylene vinyl acetate copolymer, fluorinated ethylene propylene copolymer, polyethylene terephthalate, polypyrrole and its derivatives, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, sodium carboxymethyl cellulose, SBR, Alumina, Silica, Zirconia, Aluminum Hydroxide, Hexagonal Boron Nitride, MXene, Perovskite,
  • the thickness of the active material layer is greater than or equal to 35 ⁇ m.
  • the setting of the active material layer with a certain thickness can ensure the total amount of active materials in the battery and ensure that the battery has a high energy density.
  • the elongation of the current collector is less than 3%.
  • the lower elongation of the current collector can effectively reduce the probability that the current collector debris generated when the battery is pierced by a foreign object diffuses into the active material layer and reduces the occurrence of contact short circuits.
  • the lower the elongation of the current collector is, the higher the tensile strength is, the better the mechanical properties and the better the processing performance.
  • the secondary battery includes a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a zinc secondary battery, a magnesium secondary battery, or an aluminum secondary battery.
  • the structure of the secondary battery may be a winding structure or a laminated structure.
  • the secondary battery further includes an encapsulation case, and the one or more battery cell components are encapsulated in the encapsulation case.
  • An embodiment of the present application further provides a terminal, the terminal includes a housing, an electronic component and a battery accommodated in the housing, and the battery includes the secondary battery according to the first aspect of the embodiment of the present application, the A battery powers the electronic components.
  • the ratio of the elongation of the separator to the thickness of the active material layer is controlled to be 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the elongation of the separator is equal to that of the active material layer.
  • the ratio of the elongation ratio of the current collector is controlled to be greater than or equal to 60, so that the separator has a higher elongation ratio than the active material layer and the current collector.
  • the active material layer can be effectively stretched and stretched to realize the formation of the needle-shaped conductor and the current collector and active material layer debris generated by the destruction, reducing the probability of contact short circuit, especially directly isolating the cathode collector with the highest risk of short circuit heat release.
  • the direct contact between the fluid and its debris and the negative electrode active material layer prevents the occurrence of internal short circuits in advance, alleviates the thermal runaway chain reaction from the source, and improves the safety performance of the battery.
  • the secondary battery of the embodiment of the present application through the rational design of the current collector, the separator and the active material layer, can also make the secondary battery take into account high energy density ( ⁇ 600wh/l) and fast charging capability (30min full of 80% SOC) ), with high security features. The use of this secondary battery for end products can improve the competitiveness of end products.
  • FIG. 1 is a schematic structural diagram of a secondary battery provided by an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a secondary battery provided by an embodiment of the present application after being pierced by a needle-shaped conductor;
  • FIG. 3 is a schematic structural diagram of a terminal provided by an embodiment of the present application.
  • an embodiment of the present application provides a secondary battery 100 .
  • the secondary battery 100 includes a battery cell assembly, and the battery cell assembly includes a positive pole piece 10 , a negative pole piece 20 , and a positive pole piece 10 disposed on the positive pole piece 10 .
  • the elongation of the separator is greater than 100%, and the elongation of the current collector in the positive electrode sheet 10 and/or the negative electrode sheet 20 and the thickness of the active material layer and the elongation of the separator satisfy the following relationship:
  • the ratio of the thickness of the material layer 12 is 3.0%/ ⁇ m to 8.0%/ ⁇ m, the ratio of the elongation of the separator to the elongation of the positive electrode current collector 11 is greater than or equal to 60; and/or the elongation of the separator and the negative electrode active material layer 22
  • the ratio of the thickness of the separator is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the negative electrode current collector 21 is greater than or equal to 60.
  • the secondary battery 100 may further include a plurality of stacked battery cell assemblies.
  • the battery When the battery is damaged by a mechanical external force, the foreign matter generally penetrates from the outermost side of the battery inward. Therefore, in order to improve the safety performance of the battery, at least The positive electrode sheet and/or the negative electrode sheet in the outermost battery cell assembly of the secondary battery, and the separator are configured such that the elongation of the separator is greater than 100%, and the ratio of the elongation of the separator to the thickness of the active material layer is 3.0 %/ ⁇ m ⁇ 8.0%/ ⁇ m, the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60.
  • more (two or more) positive electrode sheets and/or negative electrode sheets and separators in the battery unit assembly may also be used.
  • the positive electrode sheets and/or negative electrode sheets and separators in the plurality of battery cell assemblies may also be configured such that the elongation rate of the separator is greater than 100%, and the elongation rate of the separator is related to the activity of the separator.
  • the ratio of the thickness of the material layer is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60.
  • the positive current collector 11 , the positive active material layer 12 and the separator 30 in the positive electrode sheet 10 are configured as described above, that is, the elongation of the separator is greater than 100%, and the elongation of the separator is related to the active material layer.
  • the ratio of the thickness of the separator is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60.
  • the negative electrode current collector 21 , the negative electrode active material 22 layer and the separator 30 in the negative electrode pole piece 20 are configured as described above.
  • the positive electrode current collector 11 , the positive electrode active material layer 12 and the separator 30 in the positive electrode plate 10 may be configured in the above-mentioned manner, and the negative electrode current collector 21 , The anode active material 22 layer and the separator 30 are also arranged in the above-described manner.
  • the secondary battery of the present application can improve the safety performance of the battery by selecting a separator with a higher elongation ratio and rationally designing the current collector elongation ratio, the elongation ratio of the separator and the thickness of the active material layer.
  • the separator when the secondary battery is pierced by needle-shaped conductors or other foreign objects, the separator has a higher elongation rate than the current collector and the active material layer, which can effectively stretch and elongate.
  • the foreign matter and the current collector and active material layer debris formed by the destruction form a package to avoid the contact between the positive and negative current collectors and the positive and negative active materials and their debris, which may cause internal short circuit, block the probability of internal short circuit in advance, and avoid thermal runaway from the source. Chain reaction improves battery safety performance.
  • the secondary battery can obtain high safety performance on the premise of taking into account the high energy density ( ⁇ 600wh/l) of the battery.
  • the elongation of the separator includes the elongation in the length direction and/or the elongation in the width direction. That is, in some embodiments of the present application, the separator may only have an elongation rate greater than 100% in the length direction; in other embodiments of the present application, the separator may also only have an elongation rate greater than 100% in the width direction; In an embodiment, the elongation in the length direction and the elongation in the width direction of the separator may both be greater than 100%.
  • the elongation of the separator may also be greater than or equal to 120%. In other embodiments of the present application, the elongation of the separator is greater than or equal to 150%. In some embodiments, the elongation of the membrane may be, for example, 100%-300%.
  • the ratio of the elongation of the separator to the thickness of the active material layer is 4.0%/ ⁇ m ⁇ 6.0%/ ⁇ m.
  • a suitable ratio of the elongation of the separator to the thickness of the active material layer enables the battery to be stretched to a certain length when the battery is damaged by mechanical external force, such as when a foreign body is pierced, so that the foreign body and various debris can be well wrapped and reduced. Or avoid the occurrence of internal short circuit; at the same time, a higher energy density can be obtained, thus effectively taking into account the battery safety performance and high energy density.
  • the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 70. In other embodiments of the present application, the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 90.
  • the ratio of the elongation of the separator to the elongation of the current collector is controlled at a high ratio, so that the separator can be stretched to a certain length when the battery is pierced by foreign matter, and the foreign matter and various debris can be well wrapped. , reduce or avoid the occurrence of internal short circuit; at the same time, it can also reduce or avoid the generation of current collector debris to a certain extent.
  • the material of the separator can be various separator materials that can satisfy the secondary battery system, and specifically, the material of the separator can include polyethylene, polyalphaolefin, polypropylene, polyethylene terephthalate , polymethylpentene, polybutene, polyimide, polyamide, polyester, polyurethane, polycarbonate, cycloolefin copolymer, polybenzimidazole, polybenzobisoxazole, aramid, polyvinylidene One of vinyl fluoride, polytetrafluoroethylene, poly(vinylidene fluoride-hexafluoropropylene), polyetherimide, polyvinyl alcohol, and copolymers, blends, mixtures, and compositions of the above polymers or more.
  • the thickness of the separator may be 1 ⁇ m-12 ⁇ m. In the embodiment of the present application, the thickness of the separator may be 2 ⁇ m-10 ⁇ m.
  • the active material layer includes an active material and a binder and a conductive agent distributed in the active material.
  • the active material is a substance that can intercalate/deintercalate active ions (Li + , Na + , K + , Mg 2+ , Zn 2+ , Al 3+ , etc.).
  • the mass percentage of the active material, the binder and the conductive agent may be 80%-98.5%: 0.5%-5%: 1.0%-15%.
  • the mass percentage of active material, binder and conductive agent can be comprehensively selected according to different materials, battery types, application requirements, etc.
  • the active material layer includes a positive electrode active material layer 12 and a negative electrode active material layer 22 .
  • the positive electrode active material layer 12 includes a positive electrode active material, a binder and a conductive agent, and the positive electrode active material includes but is not limited to lithium cobalt oxide, lithium iron phosphate, sodium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, and sodium vanadium phosphate. , lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, lithium nickelate, lithium manganate, lithium nickel cobalt manganate, lithium-rich manganese base, lithium nickel cobalt aluminate, lithium titanate, and composites of the above materials one or more of , blends or compositions.
  • the negative electrode active material layer 22 includes a negative electrode active material, a binder and a conductive agent, and the negative electrode active material includes but is not limited to artificial graphite, natural graphite, hard carbon, soft carbon, mesocarbon microspheres, silicon carbon, silicon oxygen, carbon nanometers Tubes, graphene, and one or more of composites, blends, or compositions of the foregoing materials.
  • the binder and the conductive agent may be the types commonly used in the preparation of electrode sheets, specifically, the binder may be, but not limited to, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl One or more of sodium cellulose, styrene-butadiene rubber, and polyacrylic acid.
  • the conductive agent can be, but is not limited to, one or more of conductive carbon super-P, carbon nanotubes, graphene, carbon fiber, vapor-grown carbon fiber, activated carbon, porous carbon, acetylene black, and Ketjen black.
  • the current collector includes a metal foil or a metal foil with a functional coating on the surface.
  • copper foil and aluminum foil are used.
  • copper foil is usually used as a negative electrode current collector
  • aluminum foil is usually used as a positive electrode current collector.
  • the elongation of the current collector is less than 3%, and specifically may be 1%, 1.5%, 2%, or 2.5%.
  • the thickness of the current collector may be 8 ⁇ m ⁇ 20 ⁇ m.
  • the functional coating may include a functional material and a conductive agent, and the functional material may specifically be one or more of an active ion supplement, a flame retardant, and an expansion-releasing agent.
  • functional materials may include lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium rich manganese base, artificial graphite, natural graphite, hard carbon, soft carbon, mesocarbon microspheres, carbon nanotubes, graphene , carbon fiber, vapor-grown carbon fiber, activated carbon, porous carbon, acetylene black, Ketjen black, conductive ink, thermally expandable microspheres, polyethylene, polyamide, polybutadiene, ethylene ethyl acrylate, ethylene vinyl acetate copolymer, Fluorinated ethylene propylene copolymer, polyethylene terephthalate, polypyrrole and its derivatives, polyvinylidene fluoride, polytetrafluoroethylene, poly
  • the thickness of the active material layer is greater than or equal to 35 ⁇ m.
  • the active material layer with a certain thickness can ensure the total amount of active material in the battery and improve the energy density of the battery.
  • the thickness of the active material layer is 35 ⁇ m ⁇ 60 ⁇ m.
  • the thickness of the active material layer is 38 ⁇ m ⁇ 50 ⁇ m.
  • the thickness of the negative electrode active material layer is greater than the thickness of the positive electrode active material layer.
  • the peel strength of the active material layer is greater than 8 N/m.
  • the active material layer is firmly bonded on the surface of the current collector, which can improve the structural stability of the battery and improve the battery cycle life.
  • the secondary battery may be a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a zinc secondary battery, a magnesium secondary battery, or an aluminum secondary battery.
  • the structure of the secondary battery is not limited, and may be a wound structure or a laminated structure.
  • the secondary battery further includes an encapsulation case, which is used to encapsulate the positive electrode piece, the negative pole piece, the separator and the electrolyte.
  • the preparation method of the secondary battery may adopt the existing conventional technology.
  • the secondary battery provided by the embodiment of the present invention can be used in terminal consumer products, such as mobile phones, tablet computers, mobile power sources, portable machines, notebook computers, and other wearable or movable electronic devices, automobiles, etc., to improve product safety and reliability.
  • an embodiment of the present application further provides a terminal 300
  • the terminal 300 may be a mobile phone, a tablet computer, a power bank, a notebook computer, a portable computer, a smart wearable product, a car, or other products, including a casing.
  • the battery 302 supplies power for the electronic components, wherein the battery 302 is the secondary battery provided above in the embodiment of the application, and the housing 301 may include a battery assembled in front of the terminal The front cover on the side and the rear case assembled on the rear side, the battery can be fixed inside the rear case.
  • Lithium cobalt oxide is used as the positive electrode active material, and aluminum foil is used as the positive electrode current collector.
  • the positive electrode active material layer is uniformly coated on the surface of the positive electrode current collector. 1.4wt% conductive carbon black, dried at 80°C, cold-pressed, cut, slit, and vacuum-dried to obtain a positive pole piece;
  • the negative electrode active material layer is uniformly coated on the surface of the negative electrode current collector.
  • the composition of the negative electrode active material layer is 97.4wt% graphite, 1.4wt% styrene-butadiene rubber and 1.2wt% carboxylate Sodium methyl cellulose, drying at 80°C, cold-pressing, cutting, slitting, and vacuum drying to obtain negative pole pieces;
  • the positive pole piece and the negative pole piece are wound after being slit, and the positive pole piece and the negative pole piece are separated by a separator to prepare a wound bare battery core.
  • the bare cell undergoes top-side sealing, coding, vacuum drying, liquid injection, and standing at room temperature and high temperature for formation and volume separation to obtain a secondary battery.
  • the elongation of the separator is 180%
  • the elongation of the positive electrode current collector is 2%
  • the elongation of the negative electrode current collector is 2%
  • the thickness of the positive electrode active material layer is 38 ⁇ m
  • the thickness of the negative electrode active material layer is 50 ⁇ m.
  • the ratios of layer thickness and anode active material layer thickness were 4.7%/ ⁇ m and 3.6%/ ⁇ m, respectively, and the ratio of separator elongation to current collector elongation was 90 (the same for positive and negative current collectors).
  • the preparation method of the secondary battery is the same as that in Example 1, except that the elongation of the separator, the ratio of elongation of the separator to the thickness of the active material layer, and the ratio of elongation of the separator to the elongation of the current collector are different from those in Example 1. See Table 1.
  • the preparation method is the same as that of Example 1, except that the elongation of the separator in Comparative Example 1 is 50%, and the ratio of the elongation of the separator to the thickness of the positive electrode active material layer and the thickness of the negative electrode active material layer is 1.32%/ ⁇ m, respectively. and 1.0%/ ⁇ m, the ratio of separator elongation to current collector elongation is 25.
  • the lithium cobalt oxide-graphite battery system when the battery is designed to have a high energy density of 695wh/l and a fast charge performance of 80.7% SOC in 30 minutes, by selecting a separator with an elongation greater than 100%, and Ensure that the ratio of the elongation of the separator to the thickness of the active material layer (positive electrode and negative electrode) is in the range of 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60, the battery is pierced. The test showed a high pass rate.
  • Comparative Example 1 failed to pass the nail penetration test because the elongation of the separator, the ratio of elongation of the separator to the thickness of the active material layer, and the ratio of elongation of the separator to the elongation of the current collector did not meet the design requirements of the embodiments of the present application.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 20 is 36 ⁇ m, the thickness of the negative active material layer is 48 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 5.0%/ ⁇ m and 3.75%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 21 is 39 ⁇ m, the thickness of the negative active material layer is 51 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.62%/ ⁇ m and 3.53%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 22 is 40 ⁇ m, the thickness of the negative active material layer is 52 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.5%/ ⁇ m and 3.46%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 23 is 41 ⁇ m, the thickness of the negative active material layer is 53 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.39%/ ⁇ m and 3.40%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 24 is 42 ⁇ m, the thickness of the negative active material layer is 54 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.28%/ ⁇ m and 3.33%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 25 is 43 ⁇ m, the thickness of the negative active material layer is 55 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.19%/ ⁇ m and 3.27%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 26 is 44 ⁇ m, the thickness of the negative active material layer is 56 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.09%/ ⁇ m and 3.21%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 27 is 45 ⁇ m, the thickness of the negative active material layer is 57 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 4.0%/ ⁇ m and 3.16%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 28 is 46 ⁇ m, the thickness of the negative active material layer is 58 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 3.91%/ ⁇ m and 3.10%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Example 29 is 47 ⁇ m, the thickness of the negative active material layer is 59 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 3.83%/ ⁇ m and 3.05%/ ⁇ m.
  • the preparation method is the same as that of Example 1, except that the thickness of the positive active material layer in Comparative Example 2 is 70 ⁇ m, the thickness of the negative active material layer is 85 ⁇ m, and the ratio of the elongation of the separator to the thickness of the active material layer is 2.57%/ ⁇ m and 2.12%/ ⁇ m.
  • the batteries of Examples 20-29 have larger elongation separators, and the ratio of the separator elongation to the thickness of the active material layer and the ratio of the separator elongation to the current collector elongation are all in the examples of this application. range, so the battery penetration test showed a higher pass rate.
  • Comparative Example 2 although the selected elongation of the diaphragm and the ratio of the elongation of the diaphragm to the elongation of the current collector are the same as those of Examples 20-29, the ratio of the elongation of the diaphragm to the thickness of the active material layer does not meet the requirements of the embodiments of the present application. design requirements, so the battery penetration test pass rate is low.
  • the preparation method is the same as that of Example 1, except that the positive electrode active material is lithium nickel cobalt manganate.
  • the preparation method is the same as that of Example 1, except that the positive electrode active material is lithium iron phosphate.
  • the preparation method is the same as that of Example 1, except that the positive electrode active material is a composition of lithium cobalt oxide and lithium iron phosphate with a mass ratio of 97:3.
  • the preparation method is the same as that of Example 1, except that the positive electrode active material is lithium nickel cobalt aluminate.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is a composite of graphite and silicon carbon with a mass ratio of 95:5.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is a composite of graphite and silicon carbon with a mass ratio of 90:10.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is a composite of graphite and silicon carbon with a mass ratio of 85:15.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is a composite of graphite and silicon-oxygen with a mass ratio of 90:10.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is a composite of graphite and silicon-oxygen with a mass ratio of 80:20.
  • the preparation method is the same as that of Example 1, except that the negative electrode active material is hard carbon.
  • the ratio of the elongation of the separator to the thickness of the active material layer is controlled within the scope of the embodiments of the present application, and the batteries have High pass rate of nail penetration test, with high safety.
  • the battery can also have both higher energy density and better fast charging performance.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a conductive carbon coating.
  • the ratio of separator elongation to cathode current collector elongation was 120.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a nano-lithium iron phosphate coating.
  • the ratio of separator elongation to cathode current collector elongation was 140.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a conductive ink coating.
  • the ratio of separator elongation to cathode current collector elongation was 150.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a thermally expandable microsphere coating.
  • the ratio of separator elongation to cathode current collector elongation was 160.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a poly-1-butylpyrrole coating.
  • the ratio of separator elongation to cathode current collector elongation was 160.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with a poly-3-butylpyrrole-coated nanolithium iron phosphate coating.
  • the ratio of separator elongation to cathode current collector elongation was 170.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is a PTC functional aluminum foil with polyethylene and conductive carbon black.
  • the ratio of separator elongation to cathode current collector elongation was 171.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is a porous aluminum foil.
  • the ratio of separator elongation to cathode current collector elongation was 170.
  • the preparation method is the same as that of Example 1, except that the negative electrode current collector is a copper foil with a conductive carbon coating.
  • the ratio of separator elongation to anode current collector elongation was 162.
  • the preparation method is the same as that of Example 1, except that the negative electrode current collector is a copper foil with a nano-lithium iron phosphate coating.
  • the ratio of the elongation of the separator to the elongation of the negative current collector was 140.
  • the preparation method is the same as that of Example 1, except that the negative electrode current collector is a copper foil with a poly-1-butylpyrrole coating.
  • the ratio of the elongation of the separator to the elongation of the negative current collector was 160.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with an elongation rate of 4%, and the negative electrode current collector is a copper foil with an elongation rate of 4%.
  • the ratio of the elongation of the separator to the elongation of the positive electrode current collector is 45, and the ratio of the elongation of the separator to the elongation of the negative electrode current collector is 45.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with an elongation rate of 8%, and the negative electrode current collector is a copper foil with an elongation rate of 4%.
  • the ratio of the elongation of the separator to the elongation of the positive current collector is 22.5, and the ratio of the elongation of the separator to the elongation of the negative current collector is 45.
  • the preparation method is the same as that of Example 1, except that the positive electrode current collector is an aluminum foil with an elongation rate of 12%, and the negative electrode current collector is a copper foil with an elongation rate of 4%.
  • the ratio of the elongation of the separator to the elongation of the positive current collector was 15, and the ratio of the elongation of the separator to the elongation of the negative current collector was 45.
  • the batteries of Examples 40-50 have larger elongation separators, and the ratio of the separator elongation to the thickness of the active material layer and the ratio of the separator elongation to the current collector elongation are all in the examples of this application. range, so the battery penetration test showed a higher pass rate.
  • Comparative Examples 3-5 although the selected diaphragm elongation and the ratio of the diaphragm elongation to the thickness of the active material layer were the same as those of Examples 40-50, the ratio of the diaphragm elongation to the current collector elongation was less than 60, which was not satisfied. Because of the design requirements of the embodiments of the present application, the battery failed to pass the nail penetration test.
  • Thickness test of active material layer randomly select 5 points on the left, middle and right areas of the active material film, then measure the thickness with a spiral micrometer, and take the average value as the thickness of the active material layer.
  • Elongation test prepare splines with a width of 15mm and a length of 100mm along the MD and TD directions of the samples, respectively, clamp the splines to both ends of the upper and lower clamps of the stretching machine, the stretching speed is 50mm/min, and the spacing is 40mm. Record the initial spline length L0 and the total elongation L when the spline is broken, and calculate the MD and TD elongation of the spline according to (L-L0)/L0*100%.
  • Nail penetration test put the battery in a 25°C incubator, let it stand for 30 minutes, discharge it to 3.0V at 0.7C, set it aside for 5 minutes, charge it with a constant current of 0.7C to a voltage of 4.45V, and then charge it with a constant current of 4.45V. Pressure charge to 0.025C. Then put the battery in an explosion-proof box at 25°C, pierce the steel nail into the central part of the battery at a speed of 150mm/s until it penetrates, keep the needle retracted for 10 minutes, and record the test pass rate.
  • Example 1-50, Comparative Example 1-3, and Table 1-4 show that under the premise of taking into account the battery energy density (>600Wh/l) and fast charging capability (30min full of 80% SOC), when the ratio of the elongation of the separator to the thickness of the active material layer is 3.0%/ ⁇ m to 8.0%/ ⁇ m, and the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60, it can effectively improve the penetration rate of the battery and improve the battery safety performance.
  • the ratio of the elongation of the separator to the thickness of the active material layer is 3.0%/ ⁇ m to 8.0%/ ⁇ m
  • the ratio of the elongation of the separator to the elongation of the current collector is greater than or equal to 60

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Abstract

本申请提供一种二次电池，包括至少一个电池单元组件，所述电池单元组件包括正极极片、负极极片、以及设置在正极极片和负极极片之间的隔膜，正极极片和负极极片均包括集流体和设置在集流体上的活性材料层；其中，隔膜的延伸率大于100％，隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率，隔膜的延伸率与正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。本申请实施例二次电池可在兼顾高能量密度的基础上具备高安全性能。本申请实施例还提供包含该二次电池的终端。

Description

二次电池和终端
本申请要求于2020年6月28日提交中国专利局、申请号为202010598014.3、申请名称为“二次电池和终端”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及二次电池技术领域，尤其涉及一种二次电池和终端。
背景技术
随着互联网的发展和便携式移动电子设备的普及，人们对锂二次电池的容量续航和快充能力的要求越来越高，但伴随而来的电池热失控安全事故也越来越多。大量研究分析发现，二次电池的机械滥用(如穿钉、弯折、异物挤压等)所导致的内部短路，是其热失控的主要原因之一。当二次电池遭到机械外力破坏，如针状导体或其他异物刺入，集流体和活性材料层被破坏，产生碎屑，发生直接接触短路，同时，这些集流体和活性材料碎屑会随着刺入物及刺入创口扩散，从而引发更严重的正负极集流体和正负极活性材料的接触内短路，包括但不限于以下四种接触方式：(1)正极集流体(通常为铝箔)与负极集流体(通常为铜箔)；(2)正极集流体(通常为铝箔)与负极活性材料层；(3)正极活性材料层与负极活性材料层；(4)负极集流体(通常为铜箔)与正极活性材料层。其中，由于正极集流体(铝箔)和负极活性材料层的短路电阻和电池内阻较为接近，此时短路点产热功率最大，温度迅速上升，温度升高引发SEI分解及隔膜收缩熔融，导致电池发生热失控风险最高。同时，由于二次电池通常是由电池单元组件(正极集流体-正极活性材料层-隔膜-负极活性材料层-负极集流体)通过堆叠或卷绕构成，在异物刺入直至刺穿电池的过程中，破坏产生的各种碎屑往往随机接触，更容易发生内短路，同时内短路放热又极易引发热失控连锁反应。因此，有必要提供一种高安全二次电池，尽量降低或避免上述内短路的发生，提高电池安全性能。
发明内容
本申请实施例提供了一种二次电池，通过对集流体延伸率、隔膜延伸率和活性材料层厚度进行合理设计，使得二次电池可在遭到机械滥用时降低或避免内短路的发生，提高电池安全性能。
本申请实施例第一方面提供了一种二次电池，包括至少一个电池单元组件，所述电池单元组件包括正极极片、负极极片、以及设置在所述正极极片和所述负极极片之间的隔膜，所述正极极片和所述负极极片均包括集流体和设置在所述集流体上的活性材料层；其中，所述隔膜的延伸率大于100％，所述隔膜的延伸率包括沿MD方向(Machine Direction，机械方向，即纵向、长度方向)的延伸率和/或沿TD方向(Transverse Direction，垂直于机械方向，即横向、宽度方向)的延伸率，所述隔膜的延伸率与所述正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。本申请二次电池通过选择具有较高延 伸率的隔膜，并对集流体延伸率、隔膜延伸率和活性材料层厚度进行合理设计，当二次电池遭到针状导体或其他异物刺入时，隔膜相比集流体和活性材料层具有更高延伸率，可以有效拉伸伸长，实现对针状导体、其他异物以及破坏产生的集流体和活性材料层碎屑形成包裹，避免正负极集流体和正负极活性材料及其碎屑发生接触而导致内短路，大大降低内短路发生几率，从源头避免热失控连锁反应，提升电池安全性能。该二次电池，可在电池高能量密度的前提下，获得高安全性能。
本申请实施方式中，当二次电池仅包括一个电池单元组件时，该电池单元组件中的隔膜的延伸率大于100％，所述隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率，所述隔膜的延伸率与所述正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。
本申请实施方式中，当二次电池包括多个堆叠的电池单元组件时，则至少是位于二次电池最外侧的电池单元组件中的正极极片和/或负极极片、以及隔膜按上述方式配置。为了进一步提升电池的安全性能，在本申请一些实施方式中，也可以是将两个或两个以上的电池单元组件中的所述正极极片和/或负极极片、以及隔膜按上述方式进行配置。在本申请一些实施方式中，也可以是将多个电池单元组件中的正极极片和/或负极极片、以及隔膜均被配置为：所述隔膜的延伸率大于100％，所述隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率，所述隔膜的延伸率与所述活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述集流体的延伸率的比值大于或等于60。不论是叠片式电池，还是卷绕式电池，都可沿电池厚度方向包括多个堆叠的电池单元组件。多个电池单元组件中，更多的电池单元组件中的正极极片和/或负极极片、以及隔膜按上述方式进行配置，可以进一步提升电池安全性能。
本申请一些实施方式中，所述隔膜的延伸率与所述活性材料层的厚度的比值为4.0％/μm～6.0％/μm。适合的隔膜延伸率与活性材料层厚度比值，使得电池在遭到异物刺入时，隔膜能够拉伸到一定长度，对异物、各种碎屑进行较好地包裹，减少或避免内短路发生；同时也能够获得较理想的能量密度，从而有效兼顾电池安全性能和高能量密度。
本申请一些实施方式中，所述隔膜的延伸率与所述集流体的延伸率的比值大于或等于70。本申请另一些实施方式中，所述隔膜的延伸率与所述集流体的延伸率的比值大于或等于90。将隔膜的延伸率与集流体的延伸率比值控制在较高的比值，使得电池在遭到异物刺入时，隔膜能够拉伸到一定长度，对异物、各种碎屑进行较好地包裹，减少或避免内短路发生；同时，也能一定程度上减少集流体碎屑的产生。该比值越大，则隔膜延伸率相对越高，对异物和碎屑的包裹效果越好，电池安全性越好，同时集流体延伸率相对越低，有利于保证集流体较好的力学性能和加工性能，防止集流体涂布加工时发生变形和断带。
本申请实施方式中，所述正极极片包括正极集流体和设置在所述正极集流体上的正极活性材料层；所述负极极片包括负极集流体和设置在所述负极集流体上的负极活性材料层。
本申请一些实施方式中，正极极片中的正极集流体、正极活性材料层与隔膜按上述方式进行配置，即隔膜的延伸率大于100％，隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率，隔膜的延伸率与活性材料层的厚度的比值为3.0％/μm～8.0％/μm，隔膜 的延伸率与所述集流体的延伸率的比值大于或等于60。由于正极集流体与负极活性材料的短路是导致热失控发生风险最大的因素，通过对正极与隔膜进行合理设计可以较明显地提升电池安全性能。本申请另一些实施方式中，负极极片中的负极集流体、负极活性材料层与隔膜按上述方式进行配置，可以一定程度提升电池安全性能。本申请其他一些实施方式中，还可以是正极极片中的正极集流体、正极活性材料层与隔膜按上述方式进行配置，同时负极极片中的负极集流体、负极活性材料层与隔膜也按上述方式进行配置，该实施方式中，正极极片和负极极片都进行合理设计，可以更好地提升电池安全性能。
本申请一些实施方式中，所述隔膜的延伸率大于或等于120％。本申请另一些实施方式中，所述隔膜的延伸率大于或等于150％。隔膜的延伸率越高，越有利于在电池遭到机械外力破坏，如异物刺入时，发挥其保护作用，缓解内短路，提前阻断热失控，提高电池安全性能。
本申请实施方式中，隔膜的材质为能够满足二次电池体系的各种隔膜材料，所述隔膜的材质包括聚乙烯、聚α烯烃、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基戊烯、聚丁烯、聚酰亚胺、聚酰胺、聚酯、聚氨酯、聚碳酸酯、环烯烃共聚物、聚苯并咪唑、聚苯并双恶唑、芳纶、聚偏氟乙烯、聚四氟乙烯、聚(偏二氟乙烯-六氟丙烯)、聚醚酰亚胺、聚乙烯醇、以及上述聚合物的共聚物、共混物、混合物、组合物中的一种或多种。
本申请实施方式中，所述隔膜的厚度为1μm-12μm。本申请实施例通过对集流体延伸率、隔膜延伸率和活性材料层厚度进行上述合理设计，不需要通过增加隔膜厚度以及牺牲电池能量密度来提升电池安全性，同时，较薄的隔膜设计，可降低非活性辅材体积占比，有利于提升电池的能量密度。
本申请实施方式中，二次电池通常为多个由正极集流体-正极活性材料层-隔膜-负极活性材料层-负极集流体组成的电池单元组件的堆叠结构，形成叠片式电池或卷绕式电池。本申请一些实施方式中，二次电池可包括正极集流体-正极活性材料层-隔膜-负极活性材料层-负极集流体-负极活性材料层-隔膜-正极活性材料层-正极集流体。
本申请实施方式中，所述活性材料层包括活性材料和分布在所述活性材料中的粘结剂和导电剂。活性材料层中，活性材料、粘结剂与导电剂的质量百分比可以是80％～98.5％∶0.5％～5％∶1.0％～15％。
本申请实施方式中，所述集流体包括金属箔或表面具有功能涂层的金属箔。金属箔具体例如为铝箔、铜箔、钛箔等。而功能涂层可以是包括功能材料和导电剂，功能材料具体可以是活性离子补充剂、阻燃剂、膨胀缓解剂中的一种或多种。所述功能涂层包括功能材料，所述功能材料包括磷酸铁锂、磷酸锰铁锂、磷酸钒锂、富锂锰基、人造石墨、天然石墨、硬碳、软碳、中间相碳微球、碳纳米管、石墨烯、碳纤维、气相生长炭纤维、活性碳、多孔碳、乙炔黑、科琴黑、导电油墨、热膨胀微球、聚乙烯、聚酰胺、聚丁二烯、乙烯丙烯酸乙酯、乙烯醋酸乙烯共聚物、氟化乙烯丙烯共聚物、聚对苯二甲酸乙二醇酯、聚吡咯及其衍生物、聚偏氟乙烯、聚四氟乙烯、聚酰胺、羧甲基纤维素钠、丁苯橡胶、氧化铝、氧化硅、氧化锆、羟基氧化铝、六方氮化硼、MXene、钙钛矿、磷酸钛铝锂(LATP)、锂镧钛氧(LLTO)、锂镧锆氧(LLZO)、以及上述材料的复合物、共混物或组合物中的一种或多种。金属箔涂覆功能涂层后集流体整体的延伸率相对下降。功能涂层的设置可以提高电池安全 性和导热散热等性能。
本申请实施方式中，所述活性材料层的厚度大于或等于35μm。一定厚度的活性材料层设置能够保证电池中活性材料的总量，保证电池具有高能量密度。
本申请实施方式中，所述集流体的延伸率为小于3％。集流体具有较低延伸率可以有效减少在电池遭到异物刺入时产生的集流体碎屑扩散进入到活性材料层的几率，减少接触短路的发生。而且集流体延伸率相对越低，则拉伸强度相对越高，力学性能较好，加工性能更佳。
本申请实施方式中，所述二次电池包括锂二次电池、钾二次电池、钠二次电池、锌二次电池、镁二次电池或铝二次电池。
本申请实施方式中，所述二次电池的结构可以是卷绕结构，也可以是叠片结构。
本申请实施方式中，所述二次电池还包括封装壳，所述一个或多个电池单元组件封装在所述封装壳内。
本申请实施例还提供一种终端，所述终端包括壳体和收容于所述壳体内的电子元器件和电池，所述电池包括本申请实施例第一方面所述的二次电池，所述电池为所述电子元器件供电。
本申请实施例提供的二次电池，通过选择具有较高延伸率的隔膜，并将隔膜延伸率与活性材料层厚度的比值控制在3.0％/μm～8.0％/μm，以及将隔膜延伸率与集流体延伸率的比值控制在大于或等于60，这样隔膜相比活性材料层和集流体具有更高的延伸率，当二次电池遭到机械外力破坏，如穿钉时，隔膜相比集流体和活性材料层可以有效拉伸伸长，实现对针状导体以及破坏产生的集流体和活性材料层碎屑形成包裹，减少接触短路发生几率，特别是直接隔绝了短路放热风险最高的正极集流体及其碎屑和负极活性材料层的直接接触，提前阻断内短路发生，从源头缓解热失控连锁反应，提升了电池安全性能。本申请实施例的二次电池，通过对集流体、隔膜和活性材料层的合理设计，还可使得二次电池在兼顾高能量密度(≥600wh/l)和快充能力(30min充满80％SOC)的前提下，具备高安全特性。将该二次电池用于终端产品，可以提高终端产品的竞争力。
附图说明
图1是本申请实施例提供的二次电池的结构示意图；
图2是本申请实施例提供的二次电池被针状导体刺入后的示意图；
图3是本申请实施例提供的终端的结构示意图。
具体实施方式
下面结合本申请实施例中的附图对本申请实施例进行描述。
如图1所示，本申请实施例提供了一种二次电池100，二次电池100包括一个电池单元组件，电池单元组件包括正极极片10、负极极片20、以及设置在正极极片10和负极极片20之间的隔膜30、电解液40，正极极片10包括正极集流体11和设置在正极集流体11上的正极活性材料层12；负极极片20包括负极集流体21和设置在负极集流体21上的负极活性材料层22。其中，隔膜的延伸率大于100％，正极极片10和/或负极极片20中的集 流体的延伸率和活性材料层的厚度与隔膜的延伸率满足如下关系：隔膜的延伸率与正极活性材料层12的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与正极集流体11的延伸率的比值大于或等于60；和/或隔膜的延伸率与负极活性材料层22的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与负极集流体21的延伸率的比值大于或等于60。
本申请一些实施方式中，二次电池100还可包括多个堆叠的电池单元组件，由于电池遭遇机械外力破坏时，异物一般从电池最外侧向内刺入，因此，为提高电池安全性能，至少位于二次电池最外侧的电池单元组件中的正极极片和/或负极极片、以及隔膜被配置为：隔膜的延伸率大于100％，隔膜的延伸率与活性材料层的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与集流体的延伸率的比值大于或等于60。当然，为了进一步提升电池的安全性能，在本申请一些实施方式中，也可以是将更多的(两个或两个以上)电池单元组件中的正极极片和/或负极极片、以及隔膜按上述方式进行配置。在本申请一些实施方式中，也可以是将多个电池单元组件中的正极极片和/或负极极片、以及隔膜均被配置为：隔膜的延伸率大于100％，隔膜的延伸率与活性材料层的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与集流体的延伸率的比值大于或等于60。
本申请一些实施方式中，将正极极片10中的正极集流体11、正极活性材料层12与隔膜30按上述方式进行配置，即隔膜的延伸率大于100％，隔膜的延伸率与活性材料层的厚度的比值为3.0％/μm～8.0％/μm，隔膜的延伸率与集流体的延伸率的比值大于或等于60。本申请另一些实施方式中，将负极极片20中的负极集流体21、负极活性材料22层与隔膜30按上述方式进行配置。本申请其他一些实施方式中，还可以是将正极极片10中的正极集流体11、正极活性材料层12与隔膜30按上述方式进行配置，以及将负极极片20中的负极集流体21、负极活性材料22层与隔膜30也按上述方式进行配置。
本申请二次电池通过选择具有较高延伸率的隔膜，并对集流体延伸率、隔膜延伸率和活性材料层厚度进行合理设计，可提升电池安全性能。如图2所示，当二次电池遭到针状导体或其他异物刺入时，隔膜相比集流体和活性材料层具有更高延伸率可以有效拉伸伸长，实现对针状导体、其他异物以及破坏产生的集流体和活性材料层碎屑形成包裹，避免正负极集流体和正负极活性材料及其碎屑发生接触而导致内短路，提前阻断内短路发生几率，从源头避免热失控连锁反应，提升电池安全性能。该二次电池，可在兼顾电池高能量密度(≥600wh/l)的前提下，获得高安全性能。
本申请实施方式中，隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率。即在本申请一些实施方式中，隔膜可以是仅有长度方向的延伸率大于100％；在本申请另一些实施方式中，隔膜也可以是仅有宽度方向的延伸率大于100％；在其他一些实施方式中，隔膜还可以是长度方向的延伸率和宽度方向的延伸率均大于100％。
本申请一些实施方式中，隔膜的延伸率也可以是大于或等于120％。本申请另一些实施方式中，所述隔膜的延伸率大于或等于150％。在一些实施方式中，隔膜的延伸率例如可以是100％-300％。通过选择具有高延伸率的隔膜，在电池机械滥用场景中，在外物的作用下，隔膜会被拉伸，包裹外物及产生的碎屑，最大程度避免破坏后的集流体碎屑和活性材料接触，以及集流体碎屑直接接触，提高二次电池的安全性。隔膜的延伸率越高，越有利于在电池遭到异物刺入时发挥其保护作用，避免热失控的发生。
本申请一些实施方式中，隔膜的延伸率与活性材料层的厚度的比值为4.0％/μm～6.0％/μm。适合的隔膜延伸率与活性材料层厚度比值，能够使得电池在遭到机械外力破坏，如异物刺入时，隔膜能够拉伸到一定长度，对异物、各种碎屑进行较好地包裹，减少或避免内短路发生；同时也能够获得较高的能量密度，从而有效兼顾电池安全性能和高能量密度。
本申请一些实施方式中，隔膜的延伸率与集流体的延伸率的比值大于或等于70。本申请另一些实施方式中，隔膜的延伸率与集流体的延伸率的比值大于或等于90。将隔膜的延伸率与集流体的延伸率比值控制在较高的比值，能够使得电池在遭到异物刺入时，隔膜能够拉伸到一定长度，对异物、各种碎屑进行较好地包裹，减少或避免内短路发生；同时，也能一定程度上减少或避免集流体碎屑的产生。
本申请实施方式中，隔膜的材质可以是能够满足二次电池体系的各种隔膜材料，具体地，隔膜的材质可包括聚乙烯、聚α烯烃、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基戊烯、聚丁烯、聚酰亚胺、聚酰胺、聚酯、聚氨酯、聚碳酸酯、环烯烃共聚物、聚苯并咪唑、聚苯并双恶唑、芳纶、聚偏氟乙烯、聚四氟乙烯、聚(偏二氟乙烯-六氟丙烯)、聚醚酰亚胺、聚乙烯醇、以及上述聚合物的共聚物、共混物、混合物、组合物中的一种或多种。本申请实施方式中，隔膜的厚度可以是1μm-12μm。本申请实施方式中，隔膜的厚度可以是2μm-10μm。
本申请实施方式中，活性材料层包括活性材料和分布在活性材料中的粘结剂和导电剂。活性材料为可嵌入/脱出活性离子(Li +，Na +，K +，Mg 2+，Zn 2+，Al 3+等)的物质。活性材料层中，活性材料、粘结剂与导电剂的质量百分比可以是80％～98.5％∶0.5％～5％∶1.0％～15％。活性材料、粘结剂与导电剂的质量百分比可根据不同材料、电池型号、应用需求等进行综合选择。参见图1，活性材料层包括正极活性材料层12和负极活性材料层22。其中，正极活性材料层12包括正极活性材料、粘结剂和导电剂，正极活性材料包括但不限于钴酸锂、磷酸铁锂、磷酸铁钠、磷酸锰铁锂、磷酸钒锂、磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、镍酸锂、锰酸锂、镍钴锰酸锂、富锂锰基、镍钴铝酸锂、钛酸锂、以及上述材料的复合物、共混物或组合物中的一种或多种。负极活性材料层22包括负极活性材料、粘结剂和导电剂，负极活性材料包括但不限于人造石墨、天然石墨、硬碳、软碳、中间相碳微球、硅碳、硅氧、碳纳米管、石墨烯、以及上述材料的复合物、共混物或组合物中的一种或多种。
本申请实施方式中，粘结剂和导电剂可以是电极极片制备中常用的种类，具体地，粘结剂可以但不限于是聚偏氟乙烯、聚四氟乙烯、聚酰胺、羧甲基纤维素钠、丁苯橡胶、聚丙烯酸中的一种或多种。导电剂可以但不限于是导电碳super-P、碳纳米管、石墨烯、碳纤维、气相生长炭纤维、活性碳、多孔碳、乙炔黑、科琴黑中的一种或多种。
本申请实施方式中，集流体包括金属箔或表面具有功能涂层的金属箔。具体例如为铜箔、铝箔。其中，铜箔通常作为负极集流体，铝箔通常作为正极集流体。本申请实施方式中，集流体的延伸率小于3％，具体可以为1％、1.5％、2％、2.5％。集流体的厚度可为8μm～20μm。
本申请实施方式中，功能涂层可以是包括功能材料和导电剂，功能材料具体可以是活性离子补充剂、阻燃剂、膨胀缓解剂中的一种或多种。更具体地，功能材料可包括磷酸铁 锂、磷酸锰铁锂、磷酸钒锂、富锂锰基、人造石墨、天然石墨、硬碳、软碳、中间相碳微球、碳纳米管、石墨烯、碳纤维、气相生长炭纤维、活性碳、多孔碳、乙炔黑、科琴黑、导电油墨、热膨胀微球、聚乙烯、聚酰胺、聚丁二烯、乙烯丙烯酸乙酯、乙烯醋酸乙烯共聚物、氟化乙烯丙烯共聚物、聚对苯二甲酸乙二醇酯、聚吡咯及其衍生物、聚偏氟乙烯、聚四氟乙烯、聚酰胺、羧甲基纤维素钠、丁苯橡胶、氧化铝、氧化硅、氧化锆、羟基氧化铝、六方氮化硼、MXene、钙钛矿、磷酸钛铝锂(LATP)、锂镧钛氧(LLTO)、锂镧锆氧(LLZO)、以及上述材料的复合物、共混物或组合物中的一种或多种。
本申请实施方式中，活性材料层的厚度大于或等于35μm。一定厚度的活性材料层设置能够保证电池中活性材料的总量，提高电池能量密度。本申请一些实施例中，活性材料层的厚度为35μm～60μm。本申请另一些实施例中，活性材料层的厚度为38μm～50μm。其中一些实施方式中，负极活性材料层的厚度大于正极活性材料层的厚度。
本申请实施方式中，活性材料层的剥离强度大于8N/m。活性材料层在集流体表面牢固结合，能够提升电池的结构稳定性，提高电池循环寿命。
本申请实施方式中，二次电池可以是锂二次电池、钾二次电池、钠二次电池、锌二次电池、镁二次电池或铝二次电池。二次电池的结构不限，可以是卷绕结构，也可以是叠片结构。本申请实施方式中，二次电池还包括封装壳，封装壳用于封装正极极片、负极极片、隔膜和电解液，封装壳可以但不限于是铝塑膜、金属壳。二次电池的制备方法可以是采用现有常规工艺。本发明实施例提供的二次电池，可用于终端消费产品，如手机、平板电脑、移动电源、便携机、笔记本电脑以及其它可穿戴或可移动的电子设备、汽车等，提高产品安全可靠性。
如图3所示，本申请实施例还提供一种终端300，该终端300可以是手机、也可以是平板电脑、移动电源、笔记本电脑、便携机、智能穿戴产品、汽车等产品，包括壳体301、以及收容于壳体301内的电子元器件和电池302，电池302为电子元器件供电，其中，电池302为本申请实施例上述提供的二次电池，壳体301可包括组装在终端前侧的前盖和组装在后侧的后壳，电池可固定在后壳内侧。
下面通过具体实施例对本申请实施例技术方案进行进一步的说明。
实施例1
采用钴酸锂作为正极活性材料，铝箔作为正极集流体，在正极集流体表面均匀涂布正极活性材料层，正极活性材料层的组成为97.0wt％钴酸锂、1.6wt％聚偏氟乙烯和1.4wt％导电炭黑，80℃下烘干，经过冷压、裁切、分切、真空干燥后得到正极极片；
采用石墨作为负极活性材料，铜箔作为负极集流体，在负极集流体表面均匀涂布负极活性材料层，负极活性材料层的组成为97.4wt％石墨、1.4wt％丁苯橡胶和1.2wt％羧甲基纤维素钠，80℃下烘干，经过冷压、裁切、分切、真空干燥后得到负极极片；
正极极片和负极极片经分条后进行卷绕，正极极片和负极极片之间以隔膜进行分隔，制备得到卷绕裸电芯。裸电芯经过顶侧封、喷码、真空干燥、注液、常温和高温静置后进行化成及分容，得到二次电池。其中，隔膜延伸率为180％，正极集流体延伸率为2％，负极集流体延伸率为2％，正极活性材料层厚度为38μm，负极活性材料层厚度为50μm，隔膜 延伸率与正极活性材料层厚度、负极活性材料层厚度的比值分别为4.7％/μm和3.6％/μm，隔膜延伸率与集流体延伸率的比值为90(正极集流体和负极集流体相同)。
实施例2-19
二次电池制备方法与实施例1相同，不同之处仅在于，隔膜延伸率、隔膜延伸率与活性材料层厚度的比值、以及隔膜延伸率与集流体延伸率的比值与实施例1不同，具体参见表1。
对比例1
与实施例1的制备方法相同，不同之处仅在于，对比例1中的隔膜延伸率为50％，隔膜延伸率与正极活性材料层厚度、负极活性材料层厚度的比值分别为1.32％/μm和1.0％/μm，隔膜延伸率与集流体延伸率的比值为25。
表1：实施例1-19和对比例1的电池参数值和电池性能测试结果
Figure PCTCN2021102850-appb-000001
Figure PCTCN2021102850-appb-000002
基于上述测试结果可知，对于钴酸锂-石墨电池体系，在将电池设计为具有高能量密度695wh/l和30min充满80.7％SOC的快充性能下，通过选择延伸率大于100％的隔膜，并保证隔膜延伸率与活性材料层(正极和负极)厚度的比值在3.0％/μm～8.0％/μm范围内，且隔膜延伸率与集流体延伸率的比值大于或等于60时，电池的穿钉测试表现出较高的通过率。而从实施例17-19也可以获知，正极和负极中，当只有正极满足隔膜延伸率与正极的活性材料层的厚度的比值在3.0％/μm～8.0％/μm范围内，而负极不满足时，电池的穿钉测试也能获得较高的通过率，电池仍具有较高安全性，这主要是因为正极集流体与负极活性材料的短路是导致热失控发生风险最大的因素，通过对正极与隔膜进行合理设计可以较好地提升电池安全性能。而对比例1由于隔膜延伸率、隔膜延伸率与活性材料层厚度的比值、以及隔膜延伸率与集流体延伸率的比值均不满足本申请实施例的设计要求，因此未能通过穿钉测试。
实施例20：
与实施例1的制备方法相同，不同之处仅在于实施例20中的正极活性材料层厚度为36μm，负极活性材料层厚度为48μm，隔膜延伸率与活性材料层厚度的比值分别为5.0％/μm和3.75％/μm。
实施例21：
与实施例1的制备方法相同，不同之处仅在于实施例21中的正极活性材料层厚度为39μm，负极活性材料层厚度为51μm，隔膜延伸率与活性材料层厚度的比值分别为4.62％/μm和3.53％/μm。
实施例22：
与实施例1的制备方法相同，不同之处仅在于实施例22中的正极活性材料层厚度为40μm，负极活性材料层厚度为52μm，隔膜延伸率与活性材料层厚度的比值分别为4.5％/μm和3.46％/μm。
实施例23：
与实施例1的制备方法相同，不同之处仅在于实施例23中的正极活性材料层厚度为41μm，负极活性材料层厚度为53μm，隔膜延伸率与活性材料层厚度的比值分别为4.39％/μm和3.40％/μm。
实施例24：
与实施例1的制备方法相同，不同之处仅在于实施例24中的正极活性材料层厚度为42μm，负极活性材料层厚度为54μm，隔膜延伸率与活性材料层厚度的比值分别为4.28％/μm和3.33％/μm。
实施例25：
与实施例1的制备方法相同，不同之处仅在于实施例25中的正极活性材料层厚度为43μm，负极活性材料层厚度为55μm，隔膜延伸率与活性材料层厚度的比值分别为4.19％/μm和3.27％/μm。
实施例26：
与实施例1的制备方法相同，不同之处仅在于实施例26中的正极活性材料层厚度为44μm，负极活性材料层厚度为56μm，隔膜延伸率与活性材料层厚度的比值分别为4.09％/μm和3.21％/μm。
实施例27：
与实施例1的制备方法相同，不同之处仅在于实施例27中的正极活性材料层厚度为45μm，负极活性材料层厚度为57μm，隔膜延伸率与活性材料层厚度的比值分别为4.0％/μm和3.16％/μm。
实施例28：
与实施例1的制备方法相同，不同之处仅在于实施例28中的正极活性材料层厚度为46μm，负极活性材料层厚度为58μm，隔膜延伸率与活性材料层厚度的比值分别为3.91％/μm和3.10％/μm。
实施例29：
与实施例1的制备方法相同，不同之处仅在于实施例29中的正极活性材料层厚度为47μm，负极活性材料层厚度为59μm，隔膜延伸率与活性材料层厚度的比值分别为3.83％/μm和3.05％/μm。
对比例2：
与实施例1的制备方法相同，不同之处仅在于对比例2中的正极活性材料层厚度为70μm，负极活性材料层厚度为85μm，隔膜延伸率与活性材料层厚度的比值分别为2.57％/μm和2.12％/μm。
表2：实施例20-29和对比例2的测试结果
Figure PCTCN2021102850-appb-000003
基于上述测试数据可知，实施例20-29的电池由于选用具有较大延伸率隔膜，且隔膜延伸率与活性材料层厚度的比值、隔膜延伸率与集流体延伸率的比值均在本申请实施例范围内，因此电池穿钉测试表现出较高的通过率。而对比例2虽然选用的隔膜的延伸率，以及隔膜延伸率与集流体延伸率的比值与实施例20-29的相同，但由于隔膜延伸率与活性材料层厚度的比值未满足本申请实施例的设计要求，因此电池穿钉测试通过率低。
实施例30：
与实施例1的制备方法相同，不同之处仅在于正极活性材料为镍钴锰酸锂。
实施例31：
与实施例1的制备方法相同，不同之处仅在于正极活性材料为磷酸铁锂。
实施例32：
与实施例1的制备方法相同，不同之处仅在于正极活性材料为质量比为97:3的钴酸锂和磷酸铁锂的组合物。
实施例33：
与实施例1的制备方法相同，不同之处仅在于正极活性材料为镍钴铝酸锂。
实施例34：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为质量比为95:5的石墨和硅碳的复合物。
实施例35：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为质量比为90:10的石墨和硅碳的复合物。
实施例36：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为质量比为85:15的石墨和硅碳的复合物。
实施例37：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为质量比为90:10的石墨和硅氧的复合物。
实施例38：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为质量比为80:20的石墨和硅氧的复合物。
实施例39：
与实施例1的制备方法相同，不同之处仅在于负极活性材料为硬碳。
表3：实施例30-39的测试结果
Figure PCTCN2021102850-appb-000004
Figure PCTCN2021102850-appb-000005
基于上述测试数据可知，对于不同正、负极活性材料电池体系，通过将隔膜延伸率与活性材料层厚度的比值，隔膜延伸率与集流体延伸率比值控制在本申请实施例的范围，电池均具有较高穿钉测试通过率，具有高安全性。此外，电池也可以兼具较高能量密度和较佳的快充性能。
实施例40：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有导电碳涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为120。
实施例41：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有纳米磷酸铁锂涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为140。
实施例42：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有导电油墨涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为150。
实施例43：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有热膨胀微球涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为160。
实施例44：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有聚1-丁基吡咯涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为160。
实施例45：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有聚3-丁基吡咯包覆纳米磷酸铁锂涂层的铝箔。隔膜延伸率与正极集流体延伸率的比值为170。
实施例46：
与实施例1的制备方法相同，不同之处仅在于正极集流体为具有聚乙烯和导电炭黑的PTC功能铝箔。隔膜延伸率与正极集流体延伸率的比值为171。
实施例47：
与实施例1的制备方法相同，不同之处仅在于正极集流体为多孔铝箔。隔膜延伸率与 正极集流体延伸率的比值为170。
实施例48：
与实施例1的制备方法相同，不同之处仅在于负极集流体为具有导电碳涂层的铜箔。隔膜延伸率与负极集流体延伸率的比值为162。
实施例49：
与实施例1的制备方法相同，不同之处仅在于负极集流体为具有纳米磷酸铁锂涂层的铜箔。隔膜延伸率与负极集流体延伸率的比值为140。
实施例50：
与实施例1的制备方法相同，不同之处仅在于负极集流体为具有聚1-丁基吡咯涂层的铜箔。隔膜延伸率与负极集流体延伸率的比值为160。
对比例3：
与实施例1的制备方法相同，不同之处仅在于正极集流体为延伸率4％的铝箔，负极集流体为延伸率4％的铜箔。隔膜延伸率与正极集流体延伸率的比值为45，隔膜延伸率与负极集流体延伸率的比值为45。
对比例4：
与实施例1的制备方法相同，不同之处仅在于正极集流体为延伸率8％的铝箔，负极集流体为延伸率4％的铜箔。隔膜延伸率与正极集流体延伸率的比值为22.5，隔膜延伸率与负极集流体延伸率的比值为45。
对比例5：
与实施例1的制备方法相同，不同之处仅在于正极集流体为延伸率12％的铝箔，负极集流体为延伸率4％的铜箔。隔膜延伸率与正极集流体延伸率的比值为15，隔膜延伸率与负极集流体延伸率的比值为45。
表4：实施例40-50和对比例3-5的测试结果
Figure PCTCN2021102850-appb-000006
Figure PCTCN2021102850-appb-000007
基于上述测试数据可知，实施例40-50的电池由于选用具有较大延伸率隔膜，且隔膜延伸率与活性材料层厚度的比值、隔膜延伸率与集流体延伸率的比值均在本申请实施例范围内，因此电池穿钉测试表现出较高的通过率。而对比例3-5虽然选用的隔膜延伸率，以及隔膜延伸率与活性材料层厚度的比值与实施例40-50的相同，但由于隔膜延伸率与集流体延伸率的比值小于60，未满足本申请实施例的设计要求，因此电池未能通过穿钉测试。
本申请上述实施例和对比例的电池电极片和二次电池的性能测试方法如下：
1、活性材料层厚度测试：在活性材料膜片上的左、中、右区域各随机选取5个点，然后用螺旋测微器测厚，取平均值作为活性材料层厚度。
2、延伸率测试：沿样品MD和TD方向分别制备宽度15mm、长度100mm的样条，将样条夹持到拉伸机上下夹具的两端，拉伸速度为50mm/min，间距为40mm，记录初始样条长度L0，以及将样条拉断时的总伸长L，根据(L-L0)/L0*100％，计算得到样条的MD和TD延伸率。
3、能量密度测试：将电池置于25℃恒温箱中，静置30分钟，以0.5C恒流充电至电压为4.45V，然后以4.45V恒压充电至电流为0.025C，以0.5C放电至电压为3.0V，记录放电能量。能量密度＝放电能量/(电池长度*电池宽度*电池厚度)。
4、快充测试：将电池置于25℃恒温箱中，静置30分钟，以2.0C恒流充电至电压为4.25V，继续以1.5C恒流充电至4.45V，再以4.45V恒压充电至0.025C，记录充电30min的SOC。
5、穿钉测试：将电池置于25℃恒温箱中，静置30分钟，以0.7C放电至3.0V，搁置5 分钟，以0.7C恒流充电至电压为4.45V，再以4.45V恒压充电至0.025C。然后将电池置于25℃防爆箱中，以150mm/s的速度将钢钉刺入电芯中央部分，直至贯穿为止，保持10min后退针，记录测试通过率。
综合实施例1-50、对比例1-3、以及表1-4的测试结果表明，在兼顾电池能量密度(>600Wh/l)和快充能力(30min充满80％SOC)的前提下，当隔膜延伸率与活性材料层厚度的比值为3.0％/μm～8.0％/μm，且隔膜延伸率与集流体延伸率的比值大于或等于60时，可以有效提高电池的穿钉通过率，提升电池安全性能。

Claims (19)

  1. 一种二次电池，其特征在于，包括至少一个电池单元组件，所述电池单元组件包括正极极片、负极极片、以及设置在所述正极极片和所述负极极片之间的隔膜，所述正极极片和所述负极极片均包括集流体和设置在所述集流体上的活性材料层；
    其中，所述隔膜的延伸率大于100％，所述隔膜的延伸率包括沿长度方向的延伸率和/或沿宽度方向的延伸率，所述隔膜的延伸率与所述正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。
  2. 如权利要求1所述的二次电池，其特征在于，所述二次电池包括多个堆叠的电池单元组件，至少位于所述二次电池最外侧的电池单元组件中的隔膜的延伸率大于100％，所述隔膜的延伸率与所述正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。
  3. 如权利要求2所述的二次电池，其特征在于，每一所述电池单元组件中的隔膜的延伸率大于100％，所述隔膜的延伸率与所述正极极片和/或负极极片的活性材料层的厚度的比值为3.0％/μm～8.0％/μm，所述隔膜的延伸率与所述正极极片和/或负极极片的集流体的延伸率的比值大于或等于60。
  4. 如权利要求1-3任一项所述的二次电池，其特征在于，所述隔膜的延伸率与所述活性材料层的厚度的比值为4.0％/μm～6.0％/μm。
  5. 如权利要求1-4任一项所述的二次电池，其特征在于，所述隔膜的延伸率与所述集流体的延伸率的比值大于或等于70。
  6. 如权利要求5所述的二次电池，其特征在于，所述隔膜的延伸率与所述集流体的延伸率的比值大于或等于90。
  7. 如权利要求1-6任一项所述的二次电池，其特征在于，所述隔膜的延伸率大于或等于120％。
  8. 如权利要求7所述的二次电池，其特征在于，所述隔膜的延伸率大于或等于150％。
  9. 如权利要求1-8任一项所述的二次电池，其特征在于，所述隔膜的材质包括聚乙烯、聚α烯烃、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基戊烯、聚丁烯、聚酰亚胺、聚酰胺、聚酯、聚氨酯、聚碳酸酯、环烯烃共聚物、聚苯并咪唑、聚苯并双恶唑、芳纶、聚偏氟乙烯、聚四氟乙烯、聚(偏二氟乙烯-六氟丙烯)、聚醚酰亚胺、聚乙烯醇、以及上述聚合物的共聚物、共混物、混合物、组合物中的一种或多种。
  10. 如权利要求1-9任一项所述的二次电池，其特征在于，所述隔膜的厚度为1μm-12μm。
  11. 如权利要求1-10任一项所述的二次电池，其特征在于，所述活性材料层包括活性材料和分布在所述活性材料中的粘结剂和导电剂。
  12. 如权利要求1-11任一项所述的二次电池，其特征在于，所述集流体包括金属箔或表面具有功能涂层的金属箔。
  13. 如权利要求12所述的二次电池，其特征在于，所述功能涂层包括功能材料，所述 功能材料包括磷酸铁锂、磷酸锰铁锂、磷酸钒锂、富锂锰基、人造石墨、天然石墨、硬碳、软碳、中间相碳微球、碳纳米管、石墨烯、碳纤维、气相生长炭纤维、活性碳、多孔碳、乙炔黑、科琴黑、导电油墨、热膨胀微球、聚乙烯、聚酰胺、聚丁二烯、乙烯丙烯酸乙酯、乙烯醋酸乙烯共聚物、氟化乙烯丙烯共聚物、聚对苯二甲酸乙二醇酯、聚吡咯及其衍生物、聚偏氟乙烯、聚四氟乙烯、聚酰胺、羧甲基纤维素钠、丁苯橡胶、氧化铝、氧化硅、氧化锆、羟基氧化铝、六方氮化硼、MXene、钙钛矿、磷酸钛铝锂、锂镧钛氧、锂镧锆氧、以及上述材料的复合物、共混物或组合物中的一种或多种。
  14. 如权利要求1-13任一项所述的二次电池，其特征在于，所述集流体的延伸率小于3％。
  15. 如权利要求1-14任一项所述的二次电池，其特征在于，所述活性材料层的厚度大于或等于35μm。
  16. 如权利要求1-15任一项所述的二次电池，其特征在于，所述二次电池包括锂二次电池、钾二次电池、钠二次电池、锌二次电池、镁二次电池或铝二次电池。
  17. 如权利要求1-16任一项所述的二次电池，其特征在于，所述二次电池的结构包括卷绕结构、叠片结构中的一种或多种。
  18. 如权利要求1-17任一项所述的二次电池，其特征在于，所述二次电池还包括封装壳，所述一个或多个电池单元组件封装在所述封装壳内。
  19. 一种终端，其特征在于，所述终端包括壳体和收容于所述壳体内的电子元器件和电池，所述电池包括权利要求1-18任一项所述的二次电池，所述电池为所述电子元器件供电。
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