WO2024031221A1 - 集流体、极片、二次电池、电池模块、电池包和用电装置 - Google Patents

集流体、极片、二次电池、电池模块、电池包和用电装置 Download PDF

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Publication number
WO2024031221A1
WO2024031221A1 PCT/CN2022/110792 CN2022110792W WO2024031221A1 WO 2024031221 A1 WO2024031221 A1 WO 2024031221A1 CN 2022110792 W CN2022110792 W CN 2022110792W WO 2024031221 A1 WO2024031221 A1 WO 2024031221A1
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Prior art keywords
current collector
layer
foaming agent
adhesive
adhesive layer
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PCT/CN2022/110792
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English (en)
French (fr)
Inventor
李铭领
刘欣
黄起森
李铖
刘向辉
Original Assignee
宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/110792 priority Critical patent/WO2024031221A1/zh
Publication of WO2024031221A1 publication Critical patent/WO2024031221A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials

Definitions

  • the present application relates to the field of battery technology, and in particular to a current collector, pole piece, secondary battery, battery module, battery pack and electrical device.
  • secondary batteries In recent years, the application scope of secondary batteries has become more and more extensive. They are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aviation aerospace and other fields. As secondary batteries have achieved great development, higher requirements have been placed on their safety performance and other aspects.
  • the current collector used in the existing technology cannot cut off the internal short circuit of the battery in time, and the temperature of the secondary battery will rise, which is not conducive to improving the safety performance of the battery. .
  • This application was made in view of the above technical problems, and its purpose is to provide a current collector to improve the safety performance of the battery.
  • the present application provides a current collector, a pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • the first aspect of the application provides a current collector, including: a metal layer and an adhesive layer; the adhesive layer is bonded to the metal layer, and the adhesive layer includes an adhesive and a foaming agent; Wherein, the adhesive and foaming agent in the adhesive layer satisfy: 0.2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 20, where m1 is the mass of the adhesive in the adhesive layer, ⁇ 1 is the density of the adhesive in the adhesive layer, m2 is the mass of the foaming agent in the adhesive layer, and a is the gas generation amount per unit mass of the foaming agent in the adhesive layer.
  • the current collector includes a metal layer and an adhesive layer.
  • the adhesive layer is bonded to the metal layer, and the adhesive layer includes an adhesive and a foaming agent.
  • the adhesive and foaming agent in the adhesive layer satisfy: 0.2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 20.
  • the foaming agent in the adhesive layer begins to decompose and generate gas, which drives the adhesive layer to expand and the adhesive layer
  • the expansion of the metal layer drives the metal layer to expand and break; on the other hand, the adhesive melts, and the molten or molten adhesive loses at least part of its adhesive force, causing the metal layer to lose support and promoting the breakage of the metal layer.
  • the structure of the current collector is destroyed, and the conductive circuit between the positive and negative electrodes of the battery is disconnected, ensuring the safety performance of the battery.
  • the foaming agent and adhesive in the adhesive layer satisfy: 0.5 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 10.
  • the amount of gas generated by the decomposition of the foaming agent can be within a suitable range, which can not only cause the metal layer to break in time when overheated, but also avoid excessive gas generation that will cause excessive pressure inside the battery.
  • the adhesive layer further includes a conductive agent
  • the mass ratio of the conductive agent in the adhesive layer to the adhesive layer is 0.2 to 0.5.
  • the addition of conductive agent can improve the conductive performance of the adhesive layer. By setting the mass ratio of the conductive agent to the adhesive layer in the adhesive layer to 0.2 to 0.5, the conductive performance and adhesive performance of the adhesive layer can be taken into consideration.
  • the current collector further includes a support layer, and the metal layer and the support layer are connected through the adhesive layer.
  • the arrangement of the supporting layer is beneficial to improving the strength of the current collector.
  • the support layer is provided with a through hole penetrating the support layer, the through hole is filled with a filling layer, and the filling layer includes a foaming agent.
  • the filling layer can expand in time, which can promote the fracture of the metal layer and promptly disconnect the path between the positive and negative electrodes inside the battery.
  • the filling layer further includes a binder.
  • the setting of the adhesive can help improve the adhesion between the support layer and the adhesive layer, and can also inhibit the foaming agent from detaching from the filling layer.
  • the foaming agent and adhesive in the filling layer satisfy: 1 ⁇ (m3/m4)*b* ⁇ 2 ⁇ 40; where m4 is the adhesive in the filling layer.
  • the mass of the agent ⁇ 2 is the density of the binder in the filling layer
  • m3 is the mass of the foaming agent in the filling layer
  • b is the gas generation amount per unit mass of the foaming agent in the filling layer.
  • the content of the foaming agent in the filling layer is in an appropriate range, which not only ensures that when the support layer expands, it can drive the current collector to break along the thickness direction and the direction perpendicular to the thickness, but also ensures that the gas generated by the foaming agent can A suitable range that will not cause the pressure within the battery to rise sharply.
  • the foaming agent and adhesive in the filling layer satisfy: 2 ⁇ (m3/m4)*b* ⁇ 2 ⁇ 20. In this way, the foaming effect of the foaming agent in the filling layer can be further improved.
  • the filling layer further includes a conductive agent, and the mass ratio of the conductive agent in the filling layer to the bonding layer is greater than the mass ratio of the conductive agent in the bonding layer to the bonding layer. layer mass ratio. Since the area of the through holes of the support layer is much smaller than that of the current collector or adhesive layer, more conductive agent needs to be added to the filling layer to improve the conductivity of the filling layer.
  • the mass ratio of the conductive agent in the filling layer to the adhesive layer is greater than or equal to 0.4, and can be selected from 0.4 to 0.9. In this way, the adhesiveness and conductivity of the filling layer can be balanced.
  • the thickness of the support layer is 2-30 ⁇ m, optionally, the thickness of the support layer is 3-12 ⁇ m. In this way, both the strength of the current collector and the volumetric energy density of the battery can be taken into consideration.
  • the radial size of the through hole is 50 to 2000 ⁇ m. In this way, both the strength and conductivity of the current collector can be taken into consideration.
  • the distance between adjacent through holes is 1 to 50 mm. In this way, both the strength and conductivity of the current collector can be taken into consideration.
  • the material of the support layer is selected from: polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polynaphthalate Glycol ester, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene Ethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfide nitride, polyphenylene, polypyrrole, polyaniline, polythiophene, At least one of polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, and their derivatives, cross-linked products or copolymers. In this specification is selected from:
  • the foaming agent decomposes when the temperature reaches the decomposition temperature, so that the metal layer breaks. In this way, the connection between the positive electrode and the negative electrode inside the battery can be easily disconnected.
  • the decomposition temperature of the foaming agent is 80-250°C, optionally 100-220°C, further optionally 110-210°C. In this way, different foaming agents can be selected according to actual needs.
  • the adhesive layer and/or the filling layer further includes a foaming assistant.
  • the decomposition temperature of the foaming agent can be reduced.
  • the mass ratio of the foaming assistant to the foaming agent is 0.1-10. Adding an appropriate amount of foaming aid will help reduce the foaming temperature of the foaming agent. During the process of decomposing the foaming agent to produce gas, under the action of gas or bubbles, the contact effect between the foaming aid and the foaming agent will be better. , can further promote the decomposition of the foaming agent and improve the foaming effect. At the same time, under the action of gas or bubbles, the foaming aid can move, which can puncture or scratch the metal layer and promote the fracture of the metal layer.
  • the foaming assistant is selected from the group consisting of zinc oxide, zinc stearate, cadmium stearate, calcium stearate, lead stearate, nitrourea, and zinc nitrourea salt. , at least one of urea, stearic acid, lauric acid, benzoic acid and salicylic acid. In this way, it is easy to choose different foaming aids according to actual needs.
  • the conductive agent includes conductive carbon material and metal material.
  • the mixture of metal materials and conductive carbon materials is conducive to forming a better conductive network and improving the performance of the conductive agent.
  • the mass ratio of the metal material to the conductive agent is 0.5 to 0.7. This will help the conductive agent achieve better conductive effects.
  • the conductive carbon material includes: at least one of carbon black, graphite, acetylene black, carbon nanotubes, and graphene. In this way, it is easy to select different conductive carbon materials according to actual needs.
  • the metal material includes: at least one of silver, copper, iron, nickel, and aluminum. In this way, it is easy to choose different metal materials according to actual needs.
  • the foaming agent is selected from: azodicarbonamide, azobisisobutyronitrile, potassium azocarbonamideformate, dinitrosopentamethyltetramine, trinitrite Trimethylenetriamine, 4,4'-oxobenzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, benzenesulfonyl hydrazide, 2,4-toluene disulfonyl hydrazide, nitrourea, nitrourea zinc salt , diethyl azodicarboxylate, at least one of 1,3-disulfonylhydrazine benzene. In this way, it is easy to choose different foaming agents according to actual needs.
  • the binder is selected from: polypropylene, carboxylic acid and derivatives grafted polypropylene, polyethylene, carboxylic acid and derivatives grafted polyethylene, ethylene-vinyl acetate copolymer, Polyvinyl chloride, polystyrene, carboxymethylcellulose, polyacrylate, styrene-butadiene rubber, sodium polyacrylate, polyurethane, arylsulfone-grafted polyurethane, benzimidazole-grafted polyurethane, polyethyleneimine, polyvinylidene fluoride , chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenolic resin, epoxy resin, titanate coupling agent, zirconium coupling agent, aluminate coupling agent and boric acid At least one of the ester coupling agents may be at least one of polyurethane and polypropylene, and further may be polyvinyl chloride
  • the metal layer is selected from at least one of Cu, Al, Ni, Ti, Pt, Fe, Co, Cr, W, Mo, Mg, Pb, In, and Sn. Select Cu or Al. In this way, it is convenient to select the corresponding material as the metal layer according to actual needs.
  • the thickness of each metal layer is 0.5-5 ⁇ m, optionally 0.7-2 ⁇ m. In this way, both the strength of the current collector and the volumetric energy density of the battery can be taken into consideration.
  • the thickness of the adhesive layer is 0.5-5 ⁇ m, optionally 0.8-2 ⁇ m. In this way, both the bonding strength between the adhesive layer and the metal layer and the volumetric energy density of the battery can be taken into consideration.
  • a second aspect of the application provides a pole piece, including the current collector in the first aspect of the application.
  • a third aspect of the present application provides a secondary battery, including the current collector of the first aspect of the present application or the pole piece of the second aspect.
  • a fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, including the secondary battery of the third aspect of the present application or the battery module of the fourth aspect.
  • a sixth aspect of the present application provides an electrical device, including at least one selected from the group consisting of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect, and the battery pack of the fifth aspect of the present application.
  • the current collector includes a metal layer and an adhesive layer.
  • the adhesive layer is bonded to the metal layer, and the adhesive layer includes an adhesive and a foaming agent.
  • the adhesive and foaming agent in the adhesive layer satisfy: 0.2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 20.
  • the foaming agent in the adhesive layer begins to decompose and generate gas, which drives the adhesive layer to expand and the adhesive layer
  • the expansion of the metal layer drives the metal layer to expand and break; on the other hand, the adhesive melts, and the molten or molten adhesive loses at least part of its adhesive force, causing the metal layer to lose support and promoting the breakage of the metal layer.
  • the structure of the current collector is destroyed, and the conductive circuit between the positive and negative electrodes of the battery is disconnected, ensuring the safety performance of the battery.
  • Figure 1 is a schematic diagram of a current collector according to an embodiment of the present application.
  • Figure 2 is a schematic diagram of a current collector according to an embodiment of the present application.
  • Figure 3 is a schematic diagram of a current collector according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a current collector according to an embodiment of the present application.
  • Figure 5 is a schematic diagram of a current collector according to an embodiment of the present application.
  • Figure 6 is a schematic diagram of a support layer provided with through holes according to an embodiment of the present application.
  • Figure 7 is a schematic diagram of the current collector after fracture according to an embodiment of the present application.
  • Figure 8 is a microscopic schematic diagram of the bonding layer or filling layer in a normal state according to an embodiment of the present application.
  • Figure 9 is a microscopic schematic diagram of the adhesive layer or filling layer in an expanded state according to an embodiment of the present application.
  • Figure 10 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Figure 11 is an exploded view of a secondary battery according to an embodiment of the present application.
  • Figure 12 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 13 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Figure 14 is an exploded view of a battery pack according to an embodiment of the present application.
  • Figure 15 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be combined in any combination, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the current collector is an important component for preparing positive and negative electrode sheets.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer.
  • the positive electrode active material layer is coated on the surface of the positive electrode current collector.
  • the current collector that is not coated with the positive electrode active material layer protrudes from the current collector that is coated with the positive electrode active material layer.
  • the current collector coated with the positive electrode active material layer serves as the positive electrode tab.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode active material layer is coated on the surface of the negative electrode current collector.
  • the current collector that is not coated with the negative electrode active material layer protrudes from the current collector that is coated with the negative electrode active material layer.
  • the current collector coated with the negative active material layer serves as the negative electrode tab.
  • Secondary batteries mainly rely on the movement of metal ions between the positive and negative electrodes to work.
  • an internal short circuit of the battery may occur, that is, a short circuit between the positive and negative electrodes of the secondary battery.
  • the temperature of the secondary battery may rise sharply or exceed the normal operating temperature, causing thermal runaway, fire or even explosion.
  • the current collector plays a role in connecting the positive electrode and the negative electrode, which is crucial to the safety performance of the battery.
  • the present application provides a current collector, which includes a metal layer and an adhesive layer connected to the metal layer.
  • the adhesive layer includes adhesive and foaming agent.
  • Figure 1 is a schematic diagram of a current collector according to an embodiment of the present application.
  • the current collector 1 includes a metal layer 11 and an adhesive layer 12 .
  • the adhesive layer 12 is bonded to the metal layer 11 , and the adhesive layer 12 includes an adhesive and a foaming agent.
  • the adhesive and foaming agent in the adhesive layer 12 satisfy: 0.2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 20, where m1 is the mass of the adhesive in the adhesive layer 12 and ⁇ 1 is the adhesive layer.
  • the density of the adhesive in 12, m2 is the mass of the foaming agent in the adhesive layer 12, and a is the gas generation amount per unit mass of the foaming agent in the adhesive layer 12.
  • the current collector 1 can be as shown in Figure 1, including a metal layer 11 and an adhesive layer 12 connected along the thickness direction of the current collector 1, that is, the z direction.
  • the current collector 1 with this structure can be used in stacked batteries. , diversion structures in secondary batteries and other mechanical structures.
  • FIG. 2 is a schematic diagram of a current collector according to an embodiment of the present application.
  • the current collector 1 can also include, as shown in Figure 2, a metal layer 11, an adhesive layer 12, and a metal layer 11 arranged in sequence along the thickness direction of the current collector 1.
  • the current collector 1 with this structure can be used in secondary batteries and the like.
  • the adhesive layer 12 may be directly connected to the metal layer 11 , or the adhesive layer 12 may be indirectly connected to the metal layer 11 through an intermediate layer.
  • the adhesive layer 12 includes adhesive and foaming agent.
  • the adhesive layer 12 can be firmly connected to the metal layer 11 to ensure Normal function of current collector 1.
  • the temperature of the current collector 1 exceeds the normal temperature, for example, overheating caused by a short circuit of the battery or thermal runaway of the battery, on the one hand, the foaming agent in the adhesive layer 12 begins to decompose and generate gas, thereby driving the adhesive layer 12 to expand.
  • the expansion of the adhesive layer 12 drives the metal layer 11 to expand and break; on the other hand, the adhesive melts, and the molten or molten adhesive loses at least part of its adhesive force, causing the metal layer 11 to lose support and promoting metal Breakage of layer 11.
  • the structure of the current collector 1 is destroyed, so that the conductive circuit between the positive electrode and the negative electrode of the battery is disconnected, ensuring the safety performance of the battery.
  • the mass unit of the binder and the foaming agent is g.
  • the unit of the gas generation amount a per unit mass of the foaming agent is cm 3 /g.
  • the unit of the density ⁇ 1 of the binder is g/cm 3 .
  • the density ⁇ 1 is the ratio of the mass of the adhesive in the adhesive layer 12 to the volume of the adhesive in the adhesive layer 12 . It can also be said that the density ⁇ 1 of the binder is the density of the binder itself in the solid state.
  • the current collector 1 includes a metal layer 11 and an adhesive layer 12 .
  • the adhesive layer 12 is bonded to the metal layer 11 , and the adhesive layer 12 includes an adhesive and a foaming agent.
  • the adhesive and foaming agent in the adhesive layer 12 satisfy: 0.2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 20.
  • the expansion of the adhesive layer 12 drives the metal layer 11 to expand and break; on the other hand, the adhesive melts, and the molten or molten adhesive loses at least part of its adhesive force, causing the metal layer 11 to lose support and promoting metal Breakage of layer 11.
  • the structure of the current collector 1 is destroyed, so that the conductive circuit between the positive electrode and the negative electrode of the battery is disconnected, ensuring the safety performance of the battery.
  • the foaming agent and adhesive in the adhesive layer 12 satisfy: 0.5 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 10.
  • the content of the foaming agent is within an appropriate range, and the amount of gas generated by the decomposition of the foaming agent is also within an appropriate range. Therefore, the adhesive layer 12 can be expanded in time to promote the timely fracture of the metal layer 11 to cut off the internal conductive circuit of the battery, and can also avoid premature rupture of the pressure relief mechanism or battery explosion caused by excessive pressure inside the battery.
  • the foaming agent and adhesive in the adhesive layer 12 can also satisfy 2 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 10.
  • the foaming agent and adhesive in the adhesive layer 12 can also satisfy 0.5 ⁇ (m2/m1)*a* ⁇ 1 ⁇ 5. In this way, the foaming effect of the foaming agent can be further improved when the battery experiences abnormalities such as short circuit or thermal runaway.
  • the foaming effect of the foaming agent can be reflected in aspects such as the amount of gas generated when the foaming agent decomposes, the speed at which the gas is generated, the decomposition temperature, etc.
  • the amount of gas generated when the foaming agent decomposes can not only allow the metal layer 11 to break in time, but also prevent the internal pressure of the battery from being too high. At this time, it can be said that the foaming effect of the foaming agent is good.
  • the adhesive layer 12 further includes a conductive agent, and the mass ratio of the conductive agent in the adhesive layer 12 to the adhesive layer 12 is 0.2 to 0.5.
  • the addition of the conductive agent can improve the conductive performance of the adhesive layer 12. By setting the mass ratio of the conductive agent to the adhesive layer 12 in the adhesive layer 12 to 0.2-0.5, both the conductive performance and the adhesive performance of the adhesive layer 12 can be taken into consideration.
  • FIG. 3 is a schematic diagram of a current collector according to an embodiment of the present application.
  • the current collector 1 further includes a support layer 13 , and the metal layer 11 and the support layer 13 are connected through an adhesive layer 12 .
  • the arrangement of the support layer 13 is beneficial to improving the strength of the current collector 1 .
  • FIG. 4 is a schematic diagram of a current collector according to an embodiment of the present application. As shown in FIG. 4 , along the thickness direction of the current collector 1 , a metal layer 11 , an adhesive layer 12 , a support layer 13 , an adhesive layer 12 , and a metal layer 11 are arranged in sequence. That is to say, the specific structure of the current collector 1 can be specifically set according to actual needs. For example, the number of layers of the adhesive layer 12 and the support layer 13 can be specifically set according to the actual situation.
  • FIG. 5 is a schematic diagram of a current collector according to an embodiment of the present application.
  • the support layer 13 is provided with a through hole 131 penetrating the support layer 13
  • the through hole 131 is filled with a filling layer 132
  • the filling layer 132 includes a foaming agent.
  • the support layer 13 is provided with four through holes 131 penetrating the support layer 13 .
  • the through holes 131 are filled with fillers, and the fillers and the through holes 131 form a filling layer 132 . It should be noted that the number and size of the through holes 131 can be specifically set according to the actual situation, and FIG. 5 is only for illustration.
  • the filling layer 132 is filled with a foaming agent.
  • the foaming agent decomposes to generate gas.
  • the filling layer 132 expands along the thickness direction of the current collector 1 and bulges toward the metal layer 11, driving the metal layer. 11 breaks; at the same time, the filling layer 132 drives the support layer 13 to extend along the thickness direction perpendicular to the current collector 1, such as the x direction, and drives the metal layer 11 to break along the x direction. Therefore, by providing the support layer 13 and providing the filling layer 132 containing a foaming agent in the support layer 13, the fracture of the metal layer 11 and the current collector 1 can be further promoted, thereby timely disconnecting the positive electrode and the negative electrode of the battery. short circuit to avoid further development of thermal runaway.
  • the filling layer 132 further includes an adhesive.
  • the provision of the adhesive can improve the adhesion between the support layer 13 and the adhesive layer, and can also inhibit the foaming agent from detaching from the filling layer 132 .
  • the foaming agent and adhesive in the filling layer 132 satisfy: 1 ⁇ (m3/m4)*b* ⁇ 2 ⁇ 40; where m4 is the adhesive in the filling layer 132.
  • ⁇ 2 is the density of the binder in the filling layer 132
  • m3 is the mass of the foaming agent in the filling layer 132
  • b is the gas generation amount per unit mass of the foaming agent in the filling layer 132.
  • the density ⁇ 2 of the adhesive in the filling layer 132 is the ratio of the mass of the adhesive in the filling layer 132 to the volume of the adhesive. It can also be said that the density ⁇ 2 of the binder is the density of the binder itself in the solid state.
  • ⁇ 2 and ⁇ 1 are the same.
  • the foaming agent and adhesive in the filling layer 132 satisfy: 1 ⁇ (m3/m4)*b* ⁇ 2 ⁇ 40.
  • the content of the foaming agent in the filling layer is in a suitable range, which can ensure that the support layer 13
  • the current collector 1 can be driven to break along the thickness direction and the direction perpendicular to the thickness, and it can ensure that the gas generated by the foaming agent is within a suitable range and will not cause the pressure in the battery to rise sharply.
  • the foaming agent and adhesive in the filling layer 132 satisfy: 2 ⁇ (m3/m4)*b* ⁇ 2 ⁇ 20. In this way, the foaming effect of the foaming agent in the filling layer 132 can be further improved.
  • the filling layer 132 also includes a conductive agent, and the mass ratio of the conductive agent in the filling layer 132 to the filling layer 132 is greater than the mass ratio of the conductive agent in the bonding layer 12 to the bonding layer 12 Compare.
  • the filling layer 132 Since the area of the through hole 131 of the support layer 13 is much smaller than the area of the current collector 1 or the adhesive layer 12 , more conductive agent needs to be added to the filling layer 132 to improve the conductivity of the filling layer 132 . Since the filling layer 132 has lower requirements for adhesiveness, the content of the adhesive in the filling layer 132 is lower than the content of the adhesive in the adhesive layer 12 , so more can be added to the filling layer 132 .
  • the conductive agent is used to improve the electrical connection performance of the metal layer 11 located on both sides of the filling layer 132 in the thickness direction, thereby conducive to improving the conductivity of the current collector 1 .
  • the mass ratio of the conductive agent in the filling layer 132 to the filling layer 132 is 0.4 ⁇ 0.9. In this way, both the adhesiveness and conductivity of the filling layer 132 can be achieved.
  • the thickness of the support layer 13 is 2 to 30 ⁇ m, and optionally, the thickness of the support layer 13 is 3 to 12 ⁇ m.
  • the thickness of the support layer 13 is less than 2 ⁇ m, the thickness of the current collector 1 is small and it is difficult to meet the requirements for structural strength.
  • the thickness of the support layer 13 is greater than 30 ⁇ m, the thickness of the current collector 1 is larger and takes up more space, making it difficult to meet the volume energy density requirements of the battery.
  • the thickness of the support layer 13 By setting the thickness of the support layer 13 to 2-30 ⁇ m, the requirements for structural strength and volumetric energy density can be taken into consideration. Setting the thickness of the support layer 13 to 3-12 ⁇ m is conducive to further meeting the requirements for structural strength and volumetric energy density.
  • Figure 6 is a schematic diagram of a support layer provided with through holes.
  • the radial size of the through hole 131 is 50 to 2000 ⁇ m.
  • FIG. 6 shows a top view of the support layer 13 .
  • the radial dimension may be the maximum dimension of the through hole 131 along the x direction.
  • the radial dimension may be the diameter d1 of the through hole 131 ; for a through hole 131 with a rectangular cross section, the radial dimension may be rectangular.
  • the cross section of the through hole 131 may also be elliptical or other irregular shapes, and is not specifically limited here.
  • the support layer 13 or the current collector 1 may be easily broken during subsequent processes, such as cold pressing.
  • the size of the through hole 131 is less than 20 ⁇ m, the conductive agent content in the filling layer 132 in the through hole 131 is limited, and it is difficult to conduct the metal layers 11 located on both sides of the filling layer 132 .
  • both the strength and conductivity of the current collector 1 can be achieved.
  • the distance d2 between adjacent through holes 131 is 1 to 50 mm.
  • the distance d2 may be the minimum distance between adjacent through holes 131 . If the distance between adjacent through holes 131 is too large, the total content of the conductive agent in the filling layer 132 in the support layer 13 is reduced, which is not conducive to improving the conductivity of the current collector 1; the distance between adjacent through holes 131 If it is too small, it is not conducive to improving the structural strength of the current collector 1.
  • the distance between adjacent through holes 131 is 1 to 50 mm, so that the strength and conductivity of the current collector 1 can be taken into consideration.
  • the material of the support layer 13 is selected from: polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polynaphthalene.
  • the foaming agent decomposes when the temperature reaches the decomposition temperature, so that the metal layer 11 breaks.
  • the blowing agent When the blowing agent decomposes, it can produce gases such as nitrogen, carbon monoxide or carbon dioxide. When a short circuit or thermal runaway occurs in the battery, the decomposition of the foaming agent intensifies and a large amount of gas is generated. As a result, the adhesive layer 12 and the filling layer 132 expand rapidly, causing the metal layer 11 to break. The breakage of the metal layer 11 can disconnect the connection between the positive electrode and the negative electrode, thereby avoiding the further development of thermal runaway or short circuit.
  • gases such as nitrogen, carbon monoxide or carbon dioxide.
  • the decomposition temperature of the foaming agent is 80-250°C, optionally 100-220°C, and further optionally 110-210°C.
  • Different batteries may have different temperature requirements, so different foaming agents can be used. In this way, different foaming agents can be selected according to actual needs.
  • the foaming agent can be selected from azodicarbonamide, azobisisobutyronitrile, potassium azocarbonamideformate, dinitrosopentamethyltetramine, trinitrosotrimethylenetriamine, 4,4' -Oxodibenzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, benzenesulfonyl hydrazide, 2,4-toluenedisulfonyl hydrazide, nitrourea, zinc nitrourea salt, diethyl azodicarboxylate, 1, At least one of 3-disulfonylhydrazine benzene.
  • Potassium azocarboxamideformate also known as foaming agent AP, has a decomposition temperature of 175-185°C; decomposition temperature of trinitrosotrimethylenetriamine is 160-170°C; 4,4'-oxobiphenyl
  • the decomposition temperature of sulfonyl hydrazide is 157-162°C; the decomposition temperature of p-toluenesulfonyl hydrazide is 103-111°C; the decomposition temperature of benzenesulfonyl hydrazide is 130-140°C; the decomposition temperature of 2, 4-toluene disulfonyl hydrazide
  • the temperature is 130-140°C; the decomposition temperature of nitrourea is 150°C; the decomposition temperature of zinc nitrourea salt is 120°C; the decomposition temperature of diethyl azodicarboxylate is 110 ⁇ 120°C; 1,3-bis The decomposition temperature
  • the adhesive layer 12 and/or the filling layer 132 further includes a foaming assistant.
  • Foaming aids can adjust the decomposition temperature and decomposition speed of the foaming agent. By adding foaming aids, the decomposition temperature of the foaming agent can be reduced. In actual situations, different foaming agents and foaming assistants can be added according to specific conditions.
  • the decomposition temperature of azodicarbonamide is 195-210°C.
  • a foaming assistant needs to be added to reduce the decomposition temperature of the foaming agent.
  • the foaming aid of azodicarbonamide can be selected from one of zinc oxide, zinc stearate, cadmium stearate, calcium stearate, lead stearate, nitrourea, and nitrourea zinc salt, or Several kinds. For nitrourea whose decomposition temperature is around 150°C, it is not necessary to add a foaming assistant to the adhesive layer 12 and/or the filling layer 132 .
  • FIG. 7 is a schematic diagram after the current collector is broken according to an embodiment of the present application.
  • the foaming agent in the filling layer 132 and the adhesive layer 12 decomposes to produce gas.
  • the decomposed gas causes adhesion.
  • the junction layer 12 and the filling layer 132 expand and break.
  • the expanded bonding layer 12 and the filling layer 132 cause the metal layer 11 to break, so that the current collector 1 breaks.
  • the mass ratio of the foaming assistant to the foaming agent is 0.1 to 10.
  • the foaming agent plays a very small role and it is difficult to achieve the effect of promoting the decomposition of the foaming agent.
  • the mass ratio of foaming additive to foaming agent is greater than 10, the foaming agent may decompose too much and too quickly, producing excess gas, causing excessive pressure in the battery or even explosion, which is not conducive to improving the safety performance of the battery.
  • foaming aid Adding an appropriate amount of foaming aid is conducive to achieving better contact between the foaming aid and the foaming agent.
  • the foaming aid and foaming agent The contact effect of the foaming agent is better, which can further promote the decomposition of the foaming agent and improve the foaming effect.
  • the foaming aid can move, thereby puncturing or scratching the metal layer 11 and promoting the breakage of the metal layer 11 .
  • the foaming assistant can be selected from zinc oxide, zinc stearate, cadmium stearate, calcium stearate, lead stearate, nitrourea, and zinc nitrourea. at least one of salt, urea, stearic acid, lauric acid, benzoic acid and salicylic acid. In this way, it is easy to select foaming assistants according to different actual needs.
  • the conductive agent includes conductive carbon materials and metal materials.
  • the mixture of metal materials and conductive carbon materials is conducive to forming a better conductive network and improving the performance of the conductive agent.
  • Figure 8 is a microscopic schematic diagram of the bonding layer or the filling layer in a normal state according to an embodiment of the present application.
  • Figure 9 is a microscopic schematic diagram of the adhesive layer or filling layer in an expanded state according to an embodiment of the present application.
  • the bonding layer 12 or the filling layer 132 includes a bonding agent, a foaming agent, a metal material and a conductive carbon material, where the metal material can be metal particles.
  • the metal particles are connected to the conductive carbon material to form a conductive network.
  • the binder melts and the foaming agent decomposes to produce gas, which drives the adhesive layer or filling layer to expand.
  • the connection between the metal particles and the conductive carbon material becomes Disconnected, the conductive network is destroyed, and the conductivity of the current collector 1 is greatly reduced. Therefore, safety performance is further improved.
  • Figures 8 and 9 are only simple illustrations and do not represent the actual shapes and sizes of metal particles, foaming agents and conductive carbon materials.
  • the mass ratio of the metal material to the conductive agent is 0.5 to 0.7.
  • the conductive agent can have a better conductive effect.
  • the metal material includes first metal particles, and the ratio of D50 of the first metal particles to the thickness of the adhesive layer 12 is 0.7 to 0.9.
  • the D50 can refer to the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%, also known as the median particle size.
  • the D50 of the first metal particles may mean that 50% of the metal particles have a particle diameter larger than the first metal particles, and 50% of the metal particles have a particle diameter smaller than the first metal particles.
  • the ratio of the D50 of the first metal particles to the thickness of the bonding layer 12 is 0.7-0.9. In this way, metal particles of different sizes can make the contact area between the metal particles larger and promote the contact between the metal particles.
  • the mass ratio of the first metal particles to the metal material is 0.1 to 0.3.
  • the first metal particles can scratch or puncture the metal layer 11 with the movement of the gas generated by the decomposition, which is beneficial to promoting the fracture of the metal layer 11 .
  • the mass ratio of the first metal particles to the metal material is 0.1 to 0.3. In this way, the proportion of the first metal particles is in an appropriate range, which is conducive to promoting the fracture of the metal layer 11 .
  • the mass ratio of the first metal particles to the metal material is 0.1 ⁇ 0.2.
  • the metal material further includes second metal particles, and the ratio of the size D50 of the second metal particles to the thickness of the adhesive layer is less than 0.7.
  • the metal material includes first metal particles and second metal particles.
  • the metal material includes a variety of metal particles of different sizes, which is beneficial to increasing the contact area between the metal particles and improving the conductive performance.
  • the conductive carbon material includes: at least one of carbon black, graphite, acetylene black, carbon nanotubes, and graphene. In this way, it is easy to select different conductive carbon materials according to actual needs.
  • the metal material includes: at least one of silver, copper, iron, nickel, and aluminum. In this way, it is easy to choose different metal materials according to actual needs.
  • the binder is selected from: polypropylene, carboxylic acid and derivatives grafted polypropylene, polyethylene, carboxylic acid and derivatives grafted polyethylene, ethylene-vinyl acetate copolymer , polyvinyl chloride, polystyrene, carboxymethyl cellulose, polyacrylate, styrene-butadiene rubber, sodium polyacrylate, polyurethane, aryl sulfone grafted polyurethane, benzimidazole grafted polyurethane, polyethylene imine, polyvinylidene fluoride Ethylene, chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenolic resin, epoxy resin, titanate coupling agent, zirconium coupling agent, aluminate coupling agent and boron At least one of the acid ester coupling agents may be at least one of polyurethane, phenolic resin, epoxy resin,
  • the metal layer is selected from: at least one of Cu, Al, Ni, Ti, Pt, Fe, Co, Cr, W, Mo, Mg, Pb, In, and Sn, Optional Cu or Al. In this way, it is convenient to select the corresponding material as the metal layer according to actual needs.
  • the thickness of each metal layer 11 is 1 to 5 ⁇ m, optionally 0.7 to 2 ⁇ m. In this way, both the strength of the current collector 1 and the volumetric energy density of the battery can be taken into consideration.
  • the thickness of the adhesive layer 12 is 0.5-5 ⁇ m, optionally 0.8-2 ⁇ m. In this way, both the adhesive force between the adhesive layer 12 and the metal layer 11 and the volumetric energy density of the battery can be taken into consideration.
  • the thickness of the adhesive layer 12 When the thickness of the adhesive layer 12 is too small, for example, when the thickness of the adhesive layer 12 is less than 0.5 ⁇ m, the adhesive force between the adhesive layer 12 and the metal layer 11 is insufficient, which may result in a gap between the adhesive layer 12 and the metal layer 11 . separation in time.
  • the thickness of the adhesive layer 12 is too large, for example, when the thickness of the adhesive layer 12 is greater than 5 ⁇ m, the adhesive layer 12 occupies more volume space, resulting in a larger thickness of the current collector 1 , which is not conducive to improving the volumetric energy density of the battery. .
  • ball milling can be performed, followed by centrifugation for screening.
  • the ball-milled particles are first sieved through a 1 ⁇ m mesh to screen out particles with a particle size of more than 1 ⁇ m; then the obtained particles are ultrasonically treated in an aqueous solution to form a suspension, and then the particles are slurried in a solution of less than 1 ⁇ m.
  • a particle size analyzer such as a Malvern Master 3000 particle size analyzer. Determine whether to perform multiple screenings based on the particle size measurement results.
  • the solvent may be selected from one or more of DMF, cyclohexane, methylethanone, decalin, ethyl acetate, toluene, xylene, and NMP.
  • the mass ratio of the first metal particles to the second metal particles in the metal particles is 1:4.
  • the mass ratio of the first metal particles to the second metal particles in the metal particles is 1:4.
  • Drill holes on the surface of the support layer 13, for example, using a UV laser for example, using a UV laser.
  • the diameter of the through holes is 300 ⁇ m, the shape is circular, and the adjacent through holes are evenly arranged with a spacing of 5 mm;
  • steps (4) and (5) are optional steps and can be selected according to the specific structure of the current collector.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium Manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1/3Co1/3Mn1/3O2 (can also be abbreviated to NCM333), LiNi0.5Co0.2Mn0.3O2 (can also be abbreviated to NCM523), LiNi0 .5Co0.25Mn0.25O2 (can also be abbreviated to NCM211), LiNi0.6Co0.2Mn0.2O2 (can also be abbreviated to NCM622), LiNi0.8Co0.1Mn0.1O2 (can also be abbreviated to NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Al0.05O2) and at least one of
  • lithium-containing phosphates with an olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO4 (also referred to as LFP) ), at least one of composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO4 (also referred to as LFP)
  • LiMnPO4 lithium manganese phosphate
  • composite materials of lithium manganese phosphate and carbon such as LiMnPO4
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 10 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 12 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 6 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 15 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • Table 1 shows the relevant parameters and test results of the embodiment
  • the thickness of the support layer 13 is 4.5 ⁇ m
  • the thickness of the metal layer 11 is 1 ⁇ m
  • the density ⁇ 1 of the adhesive in the adhesive layer 12 is 0.905g/cm 3
  • the foaming The gas generating capacity of the agent is 215cm 3 /g.
  • a2 is the thickness of the adhesive layer 12
  • m2/m1 is the mass ratio of the foaming agent to the adhesive in the adhesive layer 12
  • m3/m4 is the mass ratio of the foaming agent to the adhesive in the filling layer 132
  • k3 is the mass ratio of foaming assistant to foaming agent in the bonding layer and filling layer
  • k4 is (m2/m1)*a* ⁇ 1
  • k5 is (m3/m4)*b* ⁇ 2
  • the through hole in the support layer is
  • the radial dimensions are all 300 ⁇ m, the distance between adjacent through holes is 5 mm, the mass ratio of the conductive agent in the adhesive layer 12 to the adhesive layer 12 is 35%, and the conductive agent in the filling layer 132 is 35%.
  • the mass ratio of the filling layer 132 is 60%.
  • No. 1 to 5 The mass ratio of the foaming auxiliary to the foaming agent is different.
  • the mass ratio of the foaming auxiliary to the foaming agent is less than 0.1, the foaming temperature cannot be effectively reduced, the foaming effect cannot be improved, and acupuncture cannot be achieved. test.
  • the mass ratio of foaming additive to foaming agent is greater than 10, the conductivity of the adhesive layer is affected, causing the conductivity of the current collector to decrease, and too much foaming additive makes the current collector's adhesion unqualified, further deteriorating it.
  • the conductive properties increase the DCR of the cell (secondary battery) and decrease the 2C discharge capacity retention rate.
  • Example 2 differ only in the through hole size d1, the through hole spacing d2, the mass proportion k6 of the conductive agent in the adhesive layer, and the through hole filling.
  • the mass proportion of conductive agent in the layer is k7.
  • Table 2 shows the relevant parameters and test results of the embodiment
  • No. 32 ⁇ 36 When the mass proportion of conductive agent in the adhesive layer is controlled at 20 ⁇ 50%, it can not only ensure the conductivity of the adhesive layer, but also ensure the adhesion of the adhesive layer, making the DCR and 2C of the battery core The discharge capacity retention rate maintains good performance, and the substrate bonding is qualified; when it is less than 20%, the conductivity of the adhesive layer is insufficient, resulting in insufficient current collector conductivity, DCR increases, and the 2C discharge capacity retention rate decreases; when it is greater than 50 %, the adhesiveness of the adhesive layer decreases, causing the base material adhesion to fail to meet the requirements, thereby deteriorating the conductive performance in the battery core, thereby increasing the DCR of the battery core and reducing the 2C discharge capacity retention rate.
  • No. 37 ⁇ 40 The proportion of conductive agent in the filling layer. Since the area of the filling layer is generally smaller than the adhesive layer, it is necessary to control the proportion of conductive agent at ⁇ 40% to ensure better through-hole conductivity, thereby making the assembly
  • the upper and lower metal layers of the fluid are well connected, so that the DCR and 2C discharge capacity retention rate of the cell perform better; when the ratio is less than 40%, the conductivity of the filling layer is insufficient, causing the conductivity between the upper and lower metal layers to becomes worse, causing the DCR to increase and the 2C discharge capacity retention rate to decrease.
  • Example 41-56 the difference in current collector preparation parameters from Example 2 is only the support layer thickness a1, the adhesive layer thickness a2 and the metal layer thickness a3.
  • Table 3 shows the relevant parameters and test results of the embodiment
  • Serial numbers 41 to 44 It shows that current collectors with different support thicknesses (2 to 30um) can achieve good performance and pass the needle punch test.
  • No. 45 ⁇ 50 When the thickness of the adhesive layer is controlled at 0.5 ⁇ 5 ⁇ m, the adhesive force of the current collector is qualified, the DCR and 2C discharge capacity retention rate of the current collector-prepared cell maintains good performance, and both can pass the pinprick test. ; When the thickness of the adhesive layer is less than 0.5 ⁇ m, the adhesion is insufficient, causing the metal layer to easily fall off, resulting in insufficient conductivity in the battery core, resulting in increased DCR and reduced 2C discharge capacity retention rate. When the thickness of the adhesive layer is greater than 5 ⁇ m, the thickness of the adhesive layer is too thick, which causes the support performance of the adhesive layer to become stronger.
  • the foaming agent foams, it cannot form an effective fracture effect of the metal layer, so it cannot be nailed through. Test; and the excessively thick adhesive layer makes the conductive agent in the adhesive layer prone to local unevenness, which reduces the conductivity of the current collector, thereby increasing the DCR and reducing the 2C discharge capacity retention rate.
  • No. 51-56 Different metal layer thicknesses.
  • the metal layer thickness is controlled between 0.5 and 5 ⁇ m, it can maintain good DCR and rate performance, and can pass the needle punch test;
  • the metal layer thickness is less than 0.5 ⁇ m, the conductivity of the metal layer Decrease, resulting in an increase in DCR and a decrease in the 2C discharge capacity retention rate;
  • the metal layer thickness is >5 ⁇ m, the metal layer is too thick and the expansion of the foaming agent cannot effectively drive the metal layer to break, and it cannot pass the needle punch test.
  • the positive electrode slurry is evenly coated on the aluminum foil or one side of the positive electrode current collector with the aluminum foil as the metal layer prepared by the above method through an extrusion coater or a transfer coater, and at 60 Drying at °C ⁇ 80 °C, then cold pressing, die cutting, and slitting to obtain the positive electrode piece.
  • the negative electrode slurry is evenly coated on the copper foil or one side of the positive electrode current collector having the copper foil as the metal layer prepared by the above method through an extrusion coater or a transfer coater, and It is dried at 60°C to 80°C, and then cold-pressed, die-cut, and slit to obtain the negative electrode piece.
  • lithium salt LiPF 6
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • VC additive vinylene carbonate
  • DEC diethyl ester
  • a polyethylene film (PE) with a thickness of 9 ⁇ m is used as the base film of the separator, and alumina, sodium carboxymethyl cellulose (CMC) and acrylate in a weight ratio of 93%: 3%: 4% are added to deionized water.
  • a vacuum mixer to obtain a slurry with a solid content of 55%.
  • the obtained slurry is evenly coated on the base film with a thickness of 2 ⁇ m on one side, and then PVDF is coated on both sides to obtain a separator.
  • the positive electrode piece, separator and negative electrode piece in order, so that the separator is between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the resulting laminate is then rolled into a square bare cell, the tabs are welded, the bare cell is put into a square aluminum case, and the top cover is laser welded. Then, after vacuum baking at 60 to 80°C to remove water, electrolyte is injected and sealed. After that, after standing at 45°C, formation (0.02C constant current charging to 3.3V, and then 0.1C constant current charging to 3.6V), shaping and capacity testing, the finished hard-shell lithium-ion battery is obtained, with a thickness of 28mm. , width is 97.5mm, length is 148mm.
  • the fresh battery is fully charged at a rate of 0.33C at room temperature 25°C and then discharged.
  • the discharge capacity at this time is recorded as the initial capacity C 0 .
  • the battery is discharged at a rate of 2C at room temperature of 25°C, and the discharge capacity at this time is calculated as C 1 .
  • Paste double-sided tape on a smooth steel plate cut the current collector to the same width as the double-sided tape, and stick it flatly on the surface of the double-sided tape. Then, cut the surface tape to have the same width as the current collector, attach it to the surface of the current collector, and connect an A4 paper strip with a length greater than the length of the steel plate at the head. Use a 2.5kg roller to roll back and forth on the surface tape until the tape is flat. Fix one end of the steel plate on the tensile machine (INSTRON, 3365), and fix the A4 paper with surface tape on the other end of the tensile machine.
  • INHTRON tensile machine
  • the tape was peeled off at a speed of 500mm/min to obtain a peeling force curve, and the average value of the peeling force was calculated and recorded as the adhesive force of the current collector.
  • the adhesive strength of the tape is ⁇ 230N/m. If no peeling of the metal layer occurs after the test, the adhesive strength is deemed to be qualified. If peeling of the metal layer occurs, the adhesive strength is deemed to be unqualified.
  • the battery core After the battery core is fully charged, it is fixed on the fixture.
  • the positive and negative poles of the battery core are connected to the voltage detection wire.
  • Temperature sensing wires are arranged at multiple positions of the battery core.
  • a 3mm diameter high-temperature resistant steel needle passes through the battery core at a speed of 80mm/s. .

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Abstract

本申请提供一种集流体，包括金属层和粘结层。粘结层与金属层粘结，粘结层中包括粘结剂和发泡剂；其中，粘结层中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20，其中，m1为粘结层中的粘结剂的质量，ρ1为粘结层中的粘结剂的密度，m2为粘结层中的发泡剂的质量，a为粘结层中的发泡剂的单位质量的发气量。本申请的技术方案可以提高电池的安全性能。

Description

集流体、极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种集流体、极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，二次电池的应用范围越来越广泛，其广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其安全性能等也提出了更高的要求。
当二次电池发生碰撞、挤压、穿刺等异常情况时，现有技术中所采用的集流体，无法及时切断电池的内短路，二次电池的温度会上升，不利于电池的安全性能的提升。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种集流体，以提高电池的安全性能。
为了达到上述目的，本申请提供了一种集流体、极片、二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种集流体，包括：金属层和粘结层；所述粘结层与所述金属层粘结，所述粘结层中包括粘结剂和发泡剂；其中，所述粘结层中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20，其中，m1为所述粘结层中的粘结剂的质量，ρ1为所述粘结层中的粘结剂的密度，m2为所述粘结层中的发泡剂的质量，a为所述粘结层中的发泡剂的单位质量的发气量。
在本申请实施例中，集流体包括金属层和粘结层。粘结层与金属层粘结， 粘结层中包括粘结剂和发泡剂。粘结层中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20。在集流体的温度超过正常温度时，比如，电池短路引发的过热、电池发生热失控时，一方面，粘结层中的发泡剂开始分解产生气体，从而带动粘结层膨胀，粘结层的膨胀带动金属层膨胀及断裂；另一方面，粘结剂发生熔化，熔化或熔融态的粘结剂失去至少部分粘结力，从而导致金属层失去支撑，促进了金属层的断裂。金属层断裂后，集流体的结构被破坏，从而电池的正极与负极之间的导电回路断开，保证了电池的安全性能。通过设置0.2≤(m2/m1)*a*ρ1≤20，可以保证在集流体的温度异常时，发泡剂分解产生的气体量处于合适的范围，既能保证金属层的及时断裂，又不会使电池内部压力过大。因此，本申请实施例的技术方案可以提高电池的安全性能。
在一种可能的实施方式中，所述粘结层中的发泡剂与粘结剂满足：0.5≤(m2/m1)*a*ρ1≤10。这样，可以发泡剂分解产生的气体量处于一个合适的范围，既能是金属层在过热时及时断裂，又能避免产生的气体过多而导致电池内部的压力过高。
在一种可能的实施方式中，所述粘结层还包括导电剂，所述粘结层中的导电剂与所述粘结层的质量比为0.2～0.5。导电剂的添加能够提升粘结层的导电性能，通过设置粘结层中导电剂与粘结层的质量比为0.2～0.5，可以兼顾粘结层的导电性能和粘结性能。
在一种可能的实施方式中，所述集流体还包括支撑层，所述金属层与所述支撑层通过所述粘结层连接。支撑层的设置有利于提高集流体的强度。
在一种可能的实施方式中，所述支撑层设置有贯穿所述支撑层的通孔，所述通孔内填充有填充层，所述填充层中包括发泡剂。这样，填充层可以及时膨胀，从而可以促进金属层的断裂，及时断开电池内部的正极与负极之间的通路。
在一种可能的实施方式中，所述填充层中还包括粘结剂。粘结剂的设置有利于提升支撑层与粘结层之间的粘结性，同时还可以抑制发泡剂从填充层中脱离。
在一种可能的实施方式中，所述填充层中的发泡剂与粘结剂满足：1≤(m3/m4)*b*ρ2≤40；其中，m4为所述填充层中的粘结剂的质量，ρ2为所述填充层中的粘结剂的密度，m3为所述填充层中的发泡剂的质量，b为所述填充层中的发泡剂的单位质量的发气量。这样，填充层中的发泡剂的含量处于一个合适的范围，既能保证支撑层发生膨胀时可以带动集流体沿厚度方向和垂直于厚度的方向断裂，又能保证发 泡剂产生的气体在一个合适的范围，不会导致电池内的压力急剧升高。
在一种可能的实施方式中，所述所述填充层中的发泡剂与粘结剂满足：2≤(m3/m4)*b*ρ2≤20。这样，可以进一步提升填充层中的发泡剂的发泡效果。
在一种可能的实施方式中，所述填充层还包括导电剂，所述填充层中的导电剂与所述粘结层的质量比大于所述粘结层中的导电剂与所述粘结层的质量比。由于支撑层的通孔的面积相对于集流体或粘结层的面积小很多，所以需要在填充层中添加更多的导电剂，以提高填充层的导电性。
在一种可能的实施方式中，所述填充层中的导电剂与所述粘结层的质量比大于或等于0.4，可选为0.4～0.9。这样，可以兼顾填充层的粘结性与导电性。
在一种可能的实施方式中，所述支撑层的厚度为2～30μm，可选地，所述支撑层的厚度为3～12μm。这样，可以兼顾集流体的强度和电池的体积能量密度。
在一种可能的实施方式中，所述通孔的径向尺寸为50～2000μm。这样，可以兼顾集流体的强度和导电性。
在一种可能的实施方式中，相邻的所述通孔之间的距离为1～50mm。这样，可以兼顾集流体的强度和导电性。
在一种可能的实施方式中，所述支撑层的材料选自：聚酰胺、聚酰亚胺、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚萘二甲酸乙二醇酯、聚碳酸酯、聚乙烯、聚丙烯、聚丙乙烯、丙烯腈-丁二烯-苯乙烯共聚物、聚乙烯醇、聚苯乙烯、聚氯乙烯、聚偏氟乙烯、聚四氟乙烯、聚苯乙烯磺酸钠、聚乙炔、硅橡胶、聚甲醛、聚苯醚、聚苯硫醚、聚乙二醇、聚氮化硫类、聚苯、聚吡咯、聚苯胺、聚噻吩、聚吡啶、纤维素、淀粉、蛋白质、环氧树脂、酚醛树脂、及其衍生物、交联物或共聚物中的至少一种。这样，能够满足支撑层对金属层的支撑要求。
在一种可能的实施方式中，所述发泡剂在温度达到分解温度时分解，以使所述金属层断裂。这样，便于实现电池内部的正极与负极之间的连接的断开。
在一种可能的实施方式中，所述发泡剂的分解温度为80～250℃，可选为100～220℃，进一步地可选为110～210℃。这样，可以根据实际需求选择不同的发泡剂。
在一种可能的实施方式中，在所述发泡剂的分解温度大于或等于190℃的情 况下，所述粘结层和/或所述填充层还包括发泡助剂。通过添加发泡助剂，可以降低发泡剂的分解温度。
在一种可能的实施方式中，所述发泡助剂与所述发泡剂的质量比为0.1～10。添加适量的发泡助剂有利于降低发泡剂的发泡温度，在发泡剂分解产生气体的过程中，在气体或气泡的作用下，发泡助剂与发泡剂的接触效果更好，可以进一步促进发泡剂分解，提高发泡效果。同时，在气体或气泡作用下，发泡助剂可以运动，从而可以刺破或划破金属层，促进金属层的断裂。
在一种可能的实施方式中，所述发泡助剂选自：氧化锌，硬酯酸锌，硬酯酸镉，硬酯酸钙，硬酯酸铅，硝基脲，硝基脲锌盐，尿素，硬酯酸，月桂酸，苯甲酸和水杨酸中的至少一种。这样，便于根据实际需要选择不同的发泡助剂。
在一种可能的实施方式中，所述导电剂包括导电碳材料和金属材料。金属材料和导电碳材料的混合有利于形成更好的导电网络，提升导电剂的性能。
在一种可能的实施方式中，所述金属材料与所述导电剂的质量比为0.5～0.7。这样，有利于导电剂实现更好的导电效果。
在一种可能的实施方式中，所述导电碳材料包括：碳黑、石墨、乙炔黑、碳纳米管、石墨烯中的至少一种。这样，便于根据实际需要选择不同的导电碳材料。
在一种可能的实施方式中，所述金属材料包括：银、铜、铁、镍、铝中的至少一种。这样，便于根据实际需要选择不同的金属材料。
在一种可能的实施方式中，所述发泡剂选自：偶氮二甲酰胺，偶氮二异丁腈，偶氮甲酰胺甲酸钾，二亚硝基五次甲基四胺，三亚硝基三亚甲基三胺，4，4’-氧代双苯磺酰肼，对甲苯磺酰肼，苯磺酰肼，2，4-甲苯二磺酰肼，硝基脲，硝基脲锌盐，偶氮二甲酸二乙酯，1,3-二磺酰肼苯中的至少一种。这样，便于根据实际需要选择不同的发泡剂。
在一种可能的实施方式中，所述粘结剂选自：聚丙烯、羧酸及衍生物接枝聚丙烯、聚乙烯、羧酸及衍生物接枝聚乙烯、乙烯-醋酸乙烯共聚物、聚氯乙烯、聚苯乙烯、羧甲基纤维素、聚丙烯酸酯、丁苯橡胶、聚丙烯酸钠、聚氨酯、芳砜接枝聚胺酯、苯并咪唑接枝聚胺酯、聚乙烯亚胺、聚偏氟乙烯、氯丁橡胶、丁腈橡胶、硅橡胶、 聚醋酸乙烯酯、脲醛树脂、酚醛树脂、环氧树脂、钛酸酯偶联剂、锆类偶联剂、铝酸酯类偶联剂和硼酸酯偶联剂中的至少一种，可选为聚氨酯类和聚丙烯类中的至少一种，进一步可选为聚氨酯类。这样，便于根据实际需要选择不同的粘结剂。
在一种可能的实施方式中，所述金属层选自：Cu、Al、Ni、Ti、Pt、Fe、Co、Cr、W、Mo、Mg、Pb、In、Sn中的至少一种，可选为Cu或Al。这样，便于根据实际需要选择相应的材料作为金属层。
在一种可能的实施方式中，每层所述金属层的厚度为0.5～5μm，可选为0.7～2μm。这样，可以兼顾集流体的强度和电池的体积能量密度。
在一种可能的实施方式中，所述粘接层的厚度为0.5～5μm，可选为0.8～2μm。这样，可以兼顾粘结层与金属层之间的粘结强度和电池的体积能量密度。
本申请的第二方面提供一种极片，包括本申请的第一方面中的集流体。
本申请的第三方面提供一种二次电池，包括本申请的第一方面中的集流体或第二方面的极片。
本申请的第四方面提供一种电池模块，包括本申请的第三方面的二次电池。
本申请的第五方面提供一种电池包，包括本申请的第三方面的二次电池或第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括选自本申请的第三方面的二次电池、第四方面的电池模块、第五方面的电池包中的至少一种。
在本申请实施例中，集流体包括金属层和粘结层。粘结层与金属层粘结，粘结层中包括粘结剂和发泡剂。粘结层中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20。在集流体的温度超过正常温度时，比如，电池短路引发的过热、电池发生热失控时，一方面，粘结层中的发泡剂开始分解产生气体，从而带动粘结层膨胀，粘结层的膨胀带动金属层膨胀及断裂；另一方面，粘结剂发生熔化，熔化或熔融态的粘结剂失去至少部分粘结力，从而导致金属层失去支撑，促进了金属层的断裂。金属层断裂后，集流体的结构被破坏，从而电池的正极与负极之间的导电回路断开，保证了电池的安全性能。通过设置0.2≤(m2/m1)*a*ρ1≤20，可以保证在集流体的温度异常时，发泡剂分解产生的气体量处于合适的范围，既能保证金属层的及时断裂，又不会 使电池内部压力过大。因此，本申请实施例的技术方案可以提高电池的安全性能。
附图说明
图1是本申请一实施例的集流体的示意图；
图2是本申请一实施例的集流体的示意图；
图3是本申请一实施例的集流体的示意图；
图4是本申请一实施例的集流体的示意图；
图5是本申请一实施例的集流体的示意图；
图6是本申请一实施例的设置有通孔的支撑层的示意图；
图7是本申请一实施例的集流体断裂后的示意图；
图8是本申请一实施例的粘结层或填充层的正常状态下的微观示意图；
图9是本申请一实施例的粘结层或填充层的膨胀状态下的微观示意图；
图10本申请一实施例的二次电池的示意图；
图11是本申请一实施例的二次电池的分解图；
图12是本申请一实施例的电池模块的示意图；
图13是本申请一实施例的电池包的示意图；
图14是本申请一实施例的电池包的分解图；
图15是本申请一实施例的用电装置的示意图；
在附图中，附图并未按照实际的比例绘制。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的集流体，极片，二次电池，电池及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方 式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
集流体是制备正极片和负极片的重要部件。正极片包括正极集流体和正极活性物质层，正极活性物质层涂覆于正极集流体的表面，未涂敷正极活性物质层的集流体凸出于已涂覆正极活性物质层的集流体，未涂敷正极活性物质层的集流体作为正极极耳。负极片包括负极集流体和负极活性物质层，负极活性物质层涂覆于负极集流体的表面，未涂敷负极活性物质层的集流体凸出于已涂覆负极活性物质层的集流体，未涂敷负极活性物质层的集流体作为负极极耳。二次电池主要依靠金属离子在正极片和负极片之间移动来工作。
在二次电池的使用过程中，由于析锂或者诸如穿刺、挤压、碰撞等外界因素的影响，可能会发生电池的内短路，即二次电池的正极与负极之间的短路。在发生短路后，可能会造成二次电池的温度急剧升高或超过正常工作温度，从而引发热失控产生起火甚至爆炸等现象。集流体作为正极片和负极片的组成部分，起到导通正极与负极的作用，对于电池的安全性能至关重要。
在发生碰撞、挤压、穿刺或析锂等故障导致二次电池发生短路时，现有的集流体难以及时切断二次电池内部的短路，不利于电池的安全性能的提升。因此，如何提供一种集流体，以提升电池的安全性能是一项亟待解决的技术问题。
有鉴于此，本申请提供了一种集流体，该集流体包括金属层和与金属层连接的粘结层。粘结层中包括粘结剂和发泡剂，通过将粘结层中的粘结剂和发泡剂设置在一个合适的范围内，既可以使金属层及时断裂以切断电池的内短路，又可以避免发泡剂分解产生过多气体导致电池内压力骤升，从而提高了电池的安全性能。
图1为本申请一实施例的集流体的示意图。在本申请的一个实施方式中，如图1所示，集流体1包括金属层11和粘结层12。粘结层12与金属层11粘结，粘结层12中包括粘结剂和发泡剂。粘结层12中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20，其中，m1为粘结层12中的粘结剂的质量，ρ1为粘结层12中的粘结剂的密度，m2为粘结层12中的发泡剂的质量，a为粘结层12中的发泡剂的单位质量的发气量。
集流体1可以如图1所示，包括沿集流体1的厚度方向，即z方向，连接的一层金属层11和一层粘结层12，该结构的集流体1可以用于叠片电池、二次电池及其它机械结构中的导流结构。
图2为本申请一实施例的集流体的示意图。集流体1也可以如图2所示，包 括沿集流体1的厚度方向依次排列的金属层11，粘结层12，金属层11，该结构的集流体1可以用于二次电池等。
可选地，粘结层12可以与金属层11直接连接，粘结层12也可以通过中间层与金属层11间接连接。
粘结层12中包括粘结剂和发泡剂。在二次电池处于正常的工作状态时，即集流体1的温度处于预设的正常温度时，由于粘结层12中包括粘结剂，粘结层12可以与金属层11牢固地连接，保证集流体1的正常功能。在集流体1的温度超过正常温度时，比如，电池短路引发的过热、电池发生热失控时，一方面，粘结层12中的发泡剂开始分解产生气体，从而带动粘结层12膨胀，粘结层12的膨胀带动金属层11膨胀及断裂；另一方面，粘结剂发生熔化，熔化或熔融态的粘结剂失去至少部分粘结力，从而导致金属层11失去支撑，促进了金属层11的断裂。金属层11断裂后，集流体1的结构被破坏，从而电池的正极与负极之间的导电回路断开，保证了电池的安全性能。
粘结剂和发泡剂的质量的单位均为g，发泡剂的单位质量的发气量a的单位为cm 3/g，粘结剂的密度ρ1的单位为g/cm 3，粘结剂的密度ρ1为粘结层12中粘结剂的质量与粘结层12中粘结剂的体积的比值。也可以说，粘结剂的密度ρ1为粘结剂在固态状态下其本身的密度。
在(m2/m1)*a*ρ1<0.2时，发泡剂的含量过少，在电池或集流体1的温度异常时，发泡剂分解产生的气体量不足，发泡效果不明显，粘结层的体积变化小，金属层难以断裂或断裂不及时。此时，在发生短路或热失控时，无法及时切断电池的内部通路，不利于提升电池的安全性能。
在(m2/m1)*a*ρ1>20时，发泡剂的含量过多，在电池或集流体的温度异常时，发泡剂发生分解产生的气体过多，导致电池内部的压力过高，从而可能导致电池的泄压机构提前破裂或电池爆炸，不利于电池的安全性的提升。
通过设置0.2≤(m2/m1)*a*ρ1≤20，可以保证在集流体1的温度异常时，发泡剂分解产生的气体量处于合适的范围，既能保证金属层11的及时断裂，又不会使电池内部压力过大。
在本申请实施例中，集流体1包括金属层11和粘结层12。粘结层12与金属层11粘结，粘结层12中包括粘结剂和发泡剂。粘结层12中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20。在集流体1的温度超过正常温度时，比如，电池短路引发的 过热、电池发生热失控时，一方面，粘结层12中的发泡剂开始分解产生气体，从而带动粘结层12膨胀，粘结层12的膨胀带动金属层11膨胀及断裂；另一方面，粘结剂发生熔化，熔化或熔融态的粘结剂失去至少部分粘结力，从而导致金属层11失去支撑，促进了金属层11的断裂。金属层11断裂后，集流体1的结构被破坏，从而电池的正极与负极之间的导电回路断开，保证了电池的安全性能。通过设置0.2≤(m2/m1)*a*ρ1≤20，可以保证在集流体1的温度异常时，发泡剂分解产生的气体量处于合适的范围，既能保证金属层11的及时断裂，又不会使电池内部压力过大。因此，本申请实施例的技术方案可以提高电池的安全性能。
可选地，在本申请一实施例中，粘结层12中的发泡剂与粘结剂满足：0.5≤(m2/m1)*a*ρ1≤10。这样，发泡剂的含量处于一个合适的范围，从而发泡剂分解产生的气体量也处于一个合适的范围。因此，既可以使粘结层12及时膨胀，从而促进金属层11的及时断裂，以切断电池的内部的导电回路，又能避免电池内部的压力过高导致的泄压机构提前破裂或电池爆炸。
可选地，粘接层12中的发泡剂与粘接剂还可以满足2≤(m2/m1)*a*ρ1≤10。可选地，粘接层12中的发泡剂与粘接剂还可以满足0.5≤(m2/m1)*a*ρ1≤5。这样，可以进一步提升电池发生短路或热失控等异常时的发泡剂的发泡效果。
发泡剂的发泡效果可以体现在例如发泡剂分解时产生的气体量，产生气体的速度，分解温度等方面。例如，发泡剂分解时产生的气体量，既能满足时金属层11及时断裂，又能避免电池内部压力过高时，此时，可以表示发泡剂的发泡效果好。
可选地，在本申请一实施例中，粘结层12还包括导电剂，粘结层12中的导电剂与粘结层12的质量比为0.2～0.5。导电剂的添加能够提升粘结层12的导电性能，通过设置粘结层12中导电剂与粘结层12的质量比为0.2～0.5，可以兼顾粘结层12的导电性能和粘结性能。
图3为本申请一实施例的集流体的示意图。可选地，在本申请一实施例中，如图3所示，集流体1还包括支撑层13，金属层11与支撑层13通过粘结层12连接。支撑层13的设置，有利于提高集流体1的强度。
图4为本申请一实施例的集流体的示意图。如图4所示，沿集流体1的厚度方向，依次设置有金属层11，粘结层12，支撑层13，粘结层12，金属层11。也就是说，集流体1的具体结构可以根据实际需要具体设置，例如，粘结层12和支撑层13的 层数可以根据实际情况具体设置。
图5为本申请一实施例的集流体的示意图。可选地，在本申请一实施例中，如图5所示，支撑层13设置有贯穿支撑层13的通孔131，通孔131内填充有填充层132，填充层132中包括发泡剂。
如图5所示，支撑层13中设置有4个贯穿支撑层13的通孔131，通孔131内填充有填充物，该填充物和通孔131形成填充层132。需要注意的是，通孔131的数量和大小可以根据实际情况具体设置，图5仅作为示意。
填充层132中填充有发泡剂，这样，在集流体1的温度异常时，发泡剂分解产生气体，填充层132沿集流体1的厚度方向膨胀并朝向金属层11凸起，带动金属层11断裂；同时填充层132带动支撑层13沿垂直于集流体1的厚度方向，例如x方向，延展，带动金属层11沿x方向断裂。因此，通过设置支撑层13，并在支撑层13中设置含有发泡剂的填充层132，能够进一步促进金属层11和集流体1的断裂，从而能够及时断开电池的正极与负极之间的短路，避免热失控的进一步发展。
可选地，在本申请一实施例中，填充层132中还包括粘结剂。粘结剂的设置可以提升支撑层13与粘结层之间的粘结性，同时还可以抑制发泡剂从填充层132中脱离。
可选地，在本申请一实施例中，填充层132中的发泡剂与粘结剂满足：1≤(m3/m4)*b*ρ2≤40；其中，m4为填充层132中的粘结剂的质量，ρ2为填充层132中的粘结剂的密度，m3为填充层132中的发泡剂的质量，b为填充层132中的发泡剂的单位质量的发气量。
填充层132中的粘结剂的密度ρ2为填充层132中的粘结剂的质量与粘结剂的体积的比值。也可以说，粘结剂的密度ρ2为粘结剂在固态状态下其本身的密度。
可选地，ρ2与ρ1的值相同。
填充层132中的发泡剂与粘结剂满足：1≤(m3/m4)*b*ρ2≤40这样，填充层中的发泡剂的含量处于一个合适的范围，既能保证支撑层13发生膨胀时可以带动集流体1沿厚度方向和垂直于厚度的方向断裂，又能保证发泡剂产生的气体在一个合适的范围，不会导致电池内的压力急剧升高。
可选地，在本申请一实施例中，填充层132中的发泡剂与粘结剂满足：2≤(m3/m4)*b*ρ2≤20。这样，可以进一步提升填充层132中的发泡剂的发泡效果。
可选地，在本申请一实施例中，填充层132还包括导电剂，填充层132中的导电剂与填充层132的质量比大于粘结层12中的导电剂与粘结层12的质量比。
由于支撑层13的通孔131的面积相对于集流体1或粘结层12的面积小很多，所以需要在填充层132中添加更多的导电剂，以提高填充层132的导电性。又由于填充层132对于粘结性的要求较低，填充层132中的粘结剂的含量相对于粘结层12中的粘结剂的含量较低，从而可以在填充层132中添加更多的导电剂，以提升位于填充层132的厚度方向的两侧的金属层11的电连接性能，从而有利于提升集流体1的导电性。
可选地，在本申请一实施例中，填充层132中的导电剂与填充层132的质量比为0.4～0.9。这样，可以兼顾填充层132的粘结性和导电性。
可选地，在本申请一实施例中，支撑层13的厚度为2～30μm，可选地，支撑层13的厚度为3～12μm。
支撑层13的厚度小于2μm时，集流体1的厚度较小，难以满足对结构强度的要求。支撑层13的厚度大于30μm时，集流体1的厚度较大，占用较多的空间，难以满足电池对于体积能量密度的要求。
通过设置支撑层13的厚度为2～30μm，可以兼顾对结构强度和体积能量密度的要求。将支撑层13的厚度设置为3～12μm，有利于进一步满足对结构强度和体积能量密度的要求。
图6为设置有通孔的支撑层的示意图。可选地，在本申请一实施例中，通孔131的径向尺寸为50～2000μm。
图6示出了支撑层13的俯视图。如图6所示，示意性的示出了沿x方向排列的4个通孔131。径向尺寸可以为通孔131的沿x方向的最大尺寸。对于横截面为圆形的通孔131而言，例如图6所示，径向尺寸可以为通孔131的直径d1；对于横截面为矩形的通孔131而言，径向尺寸可以为矩形中的长度最长的边的尺寸。通孔131的横截面还可以为椭圆形或其他不规则形状，在此不作具体限制。
通孔131的尺寸大于2000μm时，在进行后续的工序，例如冷压时，容易导致支撑层13或集流体1的断裂。通孔131的尺寸小于20μm时，通孔131内的填充层132中的导电剂含量有限，难以导通位于填充层132两侧的金属层11。
通过将通孔131的径向尺寸设置为50～2000μm，可以兼顾集流体1的强度和导电性。
可选地，在本申请一实施例中，相邻的通孔131之间的距离d2为1～50mm。
距离d2可以为相邻的通孔131之间的最小距离。相邻的通孔131之间的距离过大，支撑层13中的填充层132中的导电剂的总含量减少，不利于提升集流体1的导电性；相邻的通孔131之间的距离过小，不利于提高集流体1的结构强度。
相邻的通孔131之间的距离为1～50mm，这样可以兼顾集流体1的强度和导电性。
可选地，在本申请一实施例中，支撑层13的材料选自：聚酰胺、聚酰亚胺、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚萘二甲酸乙二醇酯、聚碳酸酯、聚乙烯、聚丙烯、聚丙乙烯、丙烯腈-丁二烯-苯乙烯共聚物、聚乙烯醇、聚苯乙烯、聚氯乙烯、聚偏氟乙烯、聚四氟乙烯、聚苯乙烯磺酸钠、聚乙炔、硅橡胶、聚甲醛、聚苯醚、聚苯硫醚、聚乙二醇、聚氮化硫类、聚苯、聚吡咯、聚苯胺、聚噻吩、聚吡啶、纤维素、淀粉、蛋白质、环氧树脂、酚醛树脂、及其衍生物、交联物或共聚物中的至少一种。这样，能够满足支撑层对金属层的支撑要求。
可选地，在本申请一实施例中，发泡剂在温度达到分解温度时分解，以使金属层11断裂。
发泡剂在分解时，可以产生氮气、一氧化碳或二氧化碳等气体。在电池发生短路、热失控时，发泡剂分解加剧，产生大量气体，从而粘结层12和填充层132迅速膨胀，进而带动金属层11断裂。金属层11断裂可以使正极与负极之间的连接断开，避免了热失控或短路的进一步发展。
可选地，在本申请一实施例中，发泡剂的分解温度为80～250℃，可选为100～220℃，进一步地可选为110～210℃。不同的电池可能具有不同的温度要求，因而可以采用不同的发泡剂，这样，可以根据实际需求选择不同的发泡剂。
发泡剂可以选自偶氮二甲酰胺，偶氮二异丁腈，偶氮甲酰胺甲酸钾，二亚硝基五次甲基四胺，三亚硝基三亚甲基三胺，4，4’-氧代双苯磺酰肼，对甲苯磺酰肼，苯磺酰肼，2，4-甲苯二磺酰肼，硝基脲，硝基脲锌盐，偶氮二甲酸二乙酯，1,3-二磺酰肼苯，中的至少一种。
偶氮甲酰胺甲酸钾，也可称为发泡剂AP，分解温度为175～185℃；三亚硝基三亚甲基三胺的分解温度为160-170℃；4，4’-氧代双苯磺酰肼的分解温度为157-162℃；对甲苯磺酰肼的分解温度为103-111℃；苯磺酰肼的分解温度为130-140℃；2， 4-甲苯二磺酰肼的分解温度为130-140℃；硝基脲的分解温度为150℃；硝基脲锌盐的分解温度为120℃；偶氮二甲酸二乙酯的分解温度为110～120℃；1,3-二磺酰肼苯的分解温度为150℃；二亚硝基五次甲基四胺，也可称为发泡剂H，分解温度为200～205℃。
可选地，在本申请一实施例中，在发泡剂的分解温度大于或等于190℃的情况下，粘结层12和/或填充层132中还包括发泡助剂。
发泡助剂可以调节发泡剂的分解温度和分解速度。通过添加发泡助剂，可以降低发泡剂的分解温度。在实际情况中，可以根据具体情况添加不同的发泡剂和发泡助剂。
例如，当选用偶氮二甲酰胺作为发泡剂时，偶氮二甲酰胺的分解温度为195～210℃，此时，需要加入发泡助剂，以降低该发泡剂的分解温度。偶氮二甲酰胺的发泡助剂可以选为氧化锌，硬酯酸锌，硬酯酸镉，硬酯酸钙，硬酯酸铅，硝基脲，硝基脲锌盐中的一种或几种。对于分解温度在150℃左右的硝基脲，可以不用在粘结层12和/或填充层132添加发泡助剂。
图7为本申请一实施例的集流体断裂后的示意图。如图7所示，当电池发生内部短路时，电池的温度升高至发泡剂的分解温度时，填充层132和粘结层12中的发泡剂分解产生气体，分解产生的气体引起粘结层12和填充层132膨胀和断裂，同时膨胀的粘结层12和填充层132导致金属层11发生断裂，从而集流体1发生断裂。
可选地，在本申请一实施例中，发泡助剂与发泡剂的质量比为0.1～10。
当发泡助剂与发泡剂的质量比小于0.1时，发泡剂起到的作用很小，难以达到促进发泡剂分解的效果。当发泡助剂与发泡剂的质量比大于10时，可能导致发泡剂分解过多过快，产生过量气体，造成电池内压力过大甚至爆炸，不利于提高电池的安全性能。
添加适量的发泡助剂有利于发泡助剂与发泡剂之间实现更好的接触，在发泡剂分解产生气体的过程中，在气体或气泡的作用下，发泡助剂与发泡剂的接触效果更好，可以进一步促进发泡剂分解，提高发泡效果。同时，在气体或气泡作用下，发泡助剂可以运动，从而可以刺破或划破金属层11，促进金属层11的断裂。
可选地，在本申请一实施例中，发泡助剂可以选为氧化锌，硬酯酸锌，硬酯酸镉，硬酯酸钙，硬酯酸铅，硝基脲，硝基脲锌盐，尿素，硬酯酸，月桂酸，苯甲酸以及水杨酸中的至少一种。这样，便于根据不同的实际需要选择发泡助剂。
可选地，在本申请一实施例中，导电剂包括导电碳材料和金属材料。金属材料和导电碳材料的混合有利于形成更好的导电网络，提升导电剂的性能。
图8为本申请一实施例的粘结层或填充层的正常状态下的微观示意图。图9为本申请一实施例的粘结层或填充层的膨胀状态下的微观示意图。粘结层12或填充层132中包括粘结剂，发泡剂，金属材料和导电碳材料，其中金属材料可以为金属颗粒。如图8所示，在电池未发生短路或热失控，也即，电池处于正常工作的状态下，金属颗粒与导电碳材料连接，形成导电网络。在电池发生内短路或热失控时，粘结剂熔化，发泡剂分解产生气体从而带动粘结层或填充层膨胀，粘结层或填充层膨胀后，金属颗粒与导电碳材料之间的连接断开，从而该导电网络被破坏，集流体1的导电性大大下降。因此，进一步提升了安全性能。
需要注意的是，图8和图9仅作简单示意，并不代表真实的金属颗粒、发泡剂及导电碳材料的形状和大小。
可选地，在本申请一实施例中，金属材料与导电剂的质量比为0.5～0.7。这样，可以使导电剂起到更好的导电效果。
可选地，在本申请一实施例中，金属材料包括第一金属颗粒，第一金属颗粒的D50与粘结层12的厚度的比值为0.7～0.9。
D50可以指一个样品的累计粒度分布百分数达到50％时所对应的粒径，也称为中值粒径。第一金属颗粒的D50可以指，粒径大于第一金属颗粒的金属颗粒占50％，粒径小于第一金属颗粒的金属颗粒占50％。
第一金属颗粒的D50与粘结层12的厚度比值为0.7～0.9，这样，不同大小的金属颗粒可以使金属颗粒之间的接触面积更大，促进金属颗粒之间的接触。
可选地，在本申请一实施例中，第一金属颗粒与金属材料的质量比为0.1～0.3。
第一金属颗粒在发泡剂分解的过程中，随着分解产生的气体的运动，第一金属颗粒可以划破或刺破金属层11，有利于促进金属层11的断裂。
第一金属颗粒与金属材料的质量比为0.1～0.3，这样，第一金属颗粒的占比处于一个合适的范围，有利于促进金属层11的断裂。
可选地，第一金属颗粒与金属材料的质量比为0.1～0.2。
可选地，在本申请一实施例中，金属材料还包括第二金属颗粒，第二金属 颗粒的尺寸D50与粘结层厚度的比值小于0.7。金属材料包括第一金属颗粒和第二金属颗粒，金属材料中包括多种不同大小的金属颗粒，有利于提升金属颗粒之间的接触面积，提升导电性能。
可选地，在本申请一实施例中，导电碳材料包括：碳黑、石墨、乙炔黑、碳纳米管、石墨烯中的至少一种。这样，便于根据实际需要选择不同的导电碳材料。
可选地，在本申请一实施例中，金属材料包括：银、铜、铁、镍、铝中的至少一种。这样，便于根据实际需要选择不同的金属材料。
可选地，在本申请一实施例中，粘结剂选自：聚丙烯、羧酸及衍生物接枝聚丙烯、聚乙烯、羧酸及衍生物接枝聚乙烯、乙烯-醋酸乙烯共聚物、聚氯乙烯、聚苯乙烯、羧甲基纤维素、聚丙烯酸酯、丁苯橡胶、聚丙烯酸钠、聚氨酯、芳砜接枝聚胺酯、苯并咪唑接枝聚胺酯、聚乙烯亚胺、聚偏氟乙烯、氯丁橡胶、丁腈橡胶、硅橡胶、聚醋酸乙烯酯、脲醛树脂、酚醛树脂、环氧树脂、钛酸酯偶联剂、锆类偶联剂、铝酸酯类偶联剂和硼酸酯偶联剂中的至少一种，可选为聚氨酯类和聚丙烯类中的至少一种，进一步可选为聚氨酯类。这样，便于根据实际需要选择不同的粘结剂。
可选地，在本申请一实施例中，金属层选自：Cu、Al、Ni、Ti、Pt、Fe、Co、Cr、W、Mo、Mg、Pb、In、Sn中的至少一种，可选为Cu或Al。这样，便于根据实际需要选择相应的材料作为金属层。
可选地，在本申请一实施例中，每层金属层11的厚度为1～5μm，可选为0.7～2μm。这样，可以兼顾集流体1的强度和电池的体积能量密度。
可选地，在本申请一实施例中，粘结层12的厚度为0.5～5μm，可选为0.8～2μm。这样，可以兼顾粘结层12与金属层11之间的粘接力和电池的体积能量密度。
当粘结层12的厚度过小，例如，粘结层12的厚度小于0.5μm时，粘结层12与金属层11之间的粘接力不足，可能导致粘结层12与金属层11之间的脱离。当粘结层12的厚度过大，例如，粘结层12的厚度大于5μm时，粘结层12占据较多体积空间，导致集流体1的厚度较大，不利于电池的体积能量密度的提升。
[金属颗粒的制备方法]
以商用的金属颗粒作为原料，进行球磨和筛选。
在制备1μm以上的金属颗粒时，采用球磨和筛网进行两次或者多次过筛，以得到目标尺寸的颗粒。
在制备1μm以下的金属颗粒时，可以进行球磨，再结合离心的方式进行筛选。在该过程中，首先将球磨后的颗粒经过1μm的筛网过筛，筛除粒径1μm以上的颗粒；而后将得到的颗粒在水溶液中超声处理，配成悬浊液，然后将其在小于或等于3000r/min的转速下离心30min；将该离心得到的底部沉淀物(大颗粒)去除，取上清液过滤烘干得到颗粒。(如果要进一步去除小颗粒，将金属颗粒地悬浊液在≥5000r/min的转速下离心20min。将该离心得到的上清液(小颗粒)去除，取沉淀物颗粒；根据实际情况还可以通过化学刻蚀进一步减小金属颗粒的直径)
通过粒度仪，例如Malvern Master 3000粒度仪，确定颗粒的中值粒径D50。根据粒径测量结果决定是否进行多次筛选。
[填充层中的粘结剂的浆料的制备方法]
将金属颗粒36份、导电碳24份、发泡剂0.537份、发泡助剂2.685份、粘结剂35.8份、固化剂1份和溶剂30份，进行混合搅拌均匀。其中，溶剂可选自DMF，环己烷，丁酮，十氢化萘，乙酸乙酯，甲苯，二甲苯，NMP中的一种或几种。可选地，金属颗粒中的第一金属颗粒与第二金属颗粒的质量比为1:4。
[粘结层中的粘结剂的浆料制备方法]
将金属颗粒21份、导电碳14份、发泡剂0.602份、发泡助剂3.01份、粘结剂60.2份、固化剂1.2份和溶剂30份，进行搅拌均匀。可选地，金属颗粒中的第一金属颗粒与第二金属颗粒的质量比为1:4。
[集流体的制备方法]
(1)在支撑层13的表面进行打孔，例如采用紫外激光进行打孔，通孔的孔径大小为300μm，形状为圆形，相邻的通孔之间以间距为5mm均匀排布；
(2)在支撑层13的表面进行浆料涂覆，使用凹版涂布进行或挤压涂布进行涂覆，采用刮刀将支撑层表面的浆料刮去，只留下通孔内的浆料，而后在60～80℃下进行烘干处理；
(3)在支撑层13的一个表面涂覆粘结剂层，在60～80℃条件下进行烘烤，而后将金属层与粘结剂层进行热压复合，热压温度为65～85℃，而后在60℃条件下熟化72h；其中，粘结剂层内包含发泡剂、金属颗粒和导电碳；
(4)在支撑层13的另一个表面涂覆粘结剂层，在60～80℃条件下进行烘烤，而后将粘结剂层与金属层在65～85℃温度下进行热压复合，而后在60℃条件下熟化72h；
(5)对金属层11进行减薄处理，利用5mol/L NaOH溶液进行化学减薄，降低金属层厚度。
在集流体的制备方法中，步骤(4)和步骤(5)为可选步骤，可以根据集流体的具体结构进行选择。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物(如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化 物(如LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、 碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图10是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图11，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个 或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图12是作为一个示例的电池模块4。参照图12，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图13和图14是作为一个示例的电池包6。参照图13和图14，在电池包6中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图15是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
表1为实施例的相关参数和测试结果
表1实施例的相关参数和测试结果
Figure PCTCN2022110792-appb-000001
在实施例和/或对比例1-19中，支撑层13厚度为4.5μm，金属层11厚度为1μm，粘结层12中的粘结剂的密度ρ1均为0.905g/cm 3，发泡剂的发气量均为215cm 3/g。a2为粘结层12的厚度，m2/m1粘结层12中的发泡剂与粘结剂的质量比，m3/m4为填充层132中的发泡剂与粘结剂的质量比，k3为粘结层和填充层中发泡助剂与发泡剂的质量比，k4为(m2/m1)*a*ρ1，k5为(m3/m4)*b*ρ2，支撑层中通孔的径向尺寸均为300μm，相邻的通孔之间的距离均为5mm，粘结层12中的导电剂与粘接层12的的质量比均为35％，填充层132中的导电剂与填充层132的质量比均为60％。
序号1～19实施例和对比例及其测试结果说明：
序号1～5：发泡助剂与发泡剂的质量比不同，发泡助剂与发泡剂的质量比小于0.1时，未能有效降低发泡温度，提升发泡效果，无法通过针刺测试。发泡助剂与发泡剂的质量比大于10时，粘结层的导电性受影响，使得集流体导电性下降，并且过多的发泡助剂使得集流体粘结力不合格，进一步恶化导电性能，使得电芯(二次电池)DCR提高，2C放电容量保持率下降。
序号6～12：当k4，即(m2/m1)*a*ρ1，小于0.2时(序号11与10对比)，粘结层中的发泡剂产生的膨胀对于金属层的断裂几乎无作用，无法通过针刺测试；当k4大于20时(序号12与6对比)，粘结层中的发泡剂产生的膨胀过大，使得电池的内压上升过大，顶破防爆阀，使得外膜(电池外部)的氧气和水分进入，引起电池失效；k4控制在0.2～20之间(序号6～10)，粘结层的发泡剂的膨胀量合适，既能使得金属层断裂，也能保证电芯的防爆阀不打开，使得电芯能够通过针刺测试。
序号13～19：当k5，即(m3/m4)*a*ρ1，小于1时，填充层内的发泡剂膨胀对于金属层断裂的贡献不足，无法通过针刺测试；当k5大于40时，填充层内的发泡剂膨胀过大，使得电芯内压上升过大，顶破防爆阀，使得外膜的氧气和水分进入，引起电芯失效。
在实施例和/或对比例20-40中，与实施例2的集流体制备参数区别仅在于通孔尺寸d1、通孔间距d2、粘结层中导电剂的质量占比k6和通孔填充层中导电剂的质量占比k7。
表2为实施例的相关参数和测试结果
表2实施例的相关参数和测试结果
Figure PCTCN2022110792-appb-000002
序号20～40实施例和/或对比例及其测试结果说明：
序号20～25：支撑层的通孔尺寸大于2000μm时，集流体强度下降，在生产过程中容易出现断带，例如当通孔尺寸达到3000μm时，平均冷压1000m出现30次断带，因而在实际生产中无法应用，并且力学性能的下降，导致其金属层在加工过程中容易收到一些破坏，因此并没有表现出更好的DCR和倍率性能；当支撑层通孔小于50μm时，填充层的导电性贡献不足，使得DCR增大，2C放电容量保持率降低；支撑层的通孔尺寸控制在50～2000mm时候既能达到良好的电芯效果，也能使得生产过程中不增加断带频次。
序号26～31：支撑层的通孔间距大于50mm时，填充层对上限两层的导电性贡献不足，使得DCR增大，2C放电容量保持率降低；支撑层通孔间距小于1mm时，集流体强度下降，导致加工过程中断带严重，序号30对应孔间距为0.5mm，平均冷压1000m产生20次断带，并且力学性能下降使得在加工过程金属层容易受到破坏，从而使得DCR有所增大，2C倍率性能有所下降；支撑层通孔间距控制在1～50mm时候既能达到良好的电芯效果，也能使得生产过程中不增加断带频次。
序号32～36：粘结层中的导电剂质量占比控制在20～50％时，既能保证粘结层导电性，也能保证粘结层的粘结性，使得电芯的DCR和2C放电容量保持率保持较好的性能，同时基材粘结是合格的；小于20％时，粘结层导电性不足，使得集流体导电不足，DCR增大，2C放电容量保持率降低；大于50％时，粘结层的粘结性下降，使得基材粘结不满足要求，从而恶化在电芯中的导电性能，从而电芯的DCR增大，2C放电容量保持率降低。
序号37～40：填充层中的导电剂占比，由于填充层的面积总体小于粘结层，所以需要控制导电剂比例在≥40％时候，能保证较好的通孔导电性，从而使得集流体上下金属层较好地导通，使得电芯地DCR和2C放电容量保持率表现较好的性能；当比例小于40％时，填充层的导电性不足，使得上下金属层之间的导电性变差，使得DCR上升，2C放电容量保持率下降。
在实施例和/或对比例41-56中，与实施例2的集流体制备参数区别仅在于支撑层厚度a1、粘结层厚度a2和金属层厚度a3。
表3为实施例的相关参数和测试结果
表3实施例的相关参数和测试结果
Figure PCTCN2022110792-appb-000003
序号20～40实施例和对比例及其测试结果说明：
序号41～44：说明不同支撑厚度(2～30um)的集流体，都能获得良好的性能，且都能通过针刺测试。
序号45～50：粘结层厚度控制在0.5～5μm时候，集流体的粘结力合格，集流体制备电芯的DCR和2C放电容量保持率保持较好性能，同时也都能通过针刺测试；当粘结层的厚度小于0.5μm时，粘结性不足，导致金属层容易脱落，从而导致在电芯中导电性不足，导致DCR增大，2C放电容量保持率降低。当粘结层的厚度大于5μm时，粘结层的厚度过厚，导致粘结层的支撑性能变强，因而在发泡剂发泡时无法形成有效的金属层断裂效果，因此无法通过穿钉测试；并且过厚的粘结层使得粘结层內导电剂容易存在局部不均匀，使得集流体导电能力下降，从而使得导致DCR增大，2C放电容量保持率降低。
序号51-56：不同的金属层厚度，金属层厚度控制在0.5～5μm时候，能保持较好的DCR和倍率性能，并且能够通过针刺测试；当金属厚度小于0.5μm时，金属层导电性降低，导致DCR增大，2C放电容量保持率降低；当金属层厚度＞5μm时，金属层太厚，发泡剂的膨胀无法有效带动金属层断裂，无法通过针刺测试。
电池的制备方法
(1)正极极片的制备
将活性物质LiNi 0.8Co 0.1Mn 0.1O 2和LiNi 0.5Co 0.2Mn 0.3O 2按照17：3的比例混合、导电剂乙炔黑(Denka Black，来自日本电化株式会社)、粘结剂聚偏二氟乙烯(HSV 900，来自Arkema Group)按重量比95:3:2在N-甲基吡咯烷酮溶剂体系中充分搅拌，以均匀混合，得到固体含量为70％的浆料。通过常规的工艺，将正极浆料通过挤压涂布机或者转移涂布机均匀涂覆在铝箔或者具有通过通过上述方法制备的具有铝箔作为金属层的正极集流体的一侧上，并在60℃～80℃下烘干，然后经过冷压、模切、分条得到正极极片。
(2)负极极片的制备
将负极活性材料人造石墨、导电剂Super P、增稠剂羧甲基纤维素钠(CMC))、粘结剂丁苯橡胶乳液(SBR))按照质量比97:0.7:1.8:0.5进行混合，加入至溶剂去离子水中，在真空搅拌机作用下搅拌均匀，获得负极浆料，该负极浆料中的固体含量为56重量％。通过常规的工艺，将负极浆料通过挤压涂布机或者转移涂布机均匀涂覆在铜箔或者具有通过通过上述方法制备的具有铜箔作为金属层的正极集流体的一侧上，并在60℃～80℃下烘干，然后经过冷压、模切、分条得到负极极片。
(3)电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐(LiPF 6)溶解在体积比为20:20:60的碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混合溶剂中，然后加入添加剂碳酸亚乙烯酯(VC)，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。
(4)隔膜的制备
以厚度为9μm的聚乙烯膜(PE)作为隔膜的基膜，将重量比93％：3％：4％的氧化铝、羧甲基纤维素钠(CMC)和丙烯酸酯加入至去离子水中，在真空搅拌机作用下搅拌均匀，获得浆料，该浆料中的固体含量为55％。将得到的浆料以单面2μm的厚度均匀涂覆在基膜上，而后在双面涂覆PVDF，获得隔膜。
(5)锂离子电池的装配
将正极极片、隔膜和负极极片按顺序叠好，使隔膜处于正极极片和负极极片之间，起到隔离的作用。然后将得到的层叠体卷绕成方形的裸电芯，焊接极耳，将裸电芯装入方形铝壳中，激光焊接顶盖。然后在60～80℃下真空烘烤除水后，注入电解液并封口。之后，经过45℃静置、化成(0.02C恒流充电到3.3V，再以0.1C恒流充电到3.6V)、整形和容量测试等工序，获得成品硬壳锂离子电池，其厚度为28mm、宽度为97.5mm、长度为148mm。
[粘结剂密度ρ1测量]
取一定重量的粘结剂(≥0.1g)，用天平称量其重量m1，而后利用真密度测试仪测试粘结剂的真体积V1，粘结剂的密度ρ1＝m1/V1。
[发泡剂单位重量发气量a测量]
取一定重量的发泡剂(0.1～0.5g)，用天平称量其重量m2，根据发泡剂种类选择性按1：1加入发泡助剂，均匀混合后放入铝塑膜袋内，进行抽真空密封(并且真空密封一个空的铝塑膜袋)，而后将密封好的铝塑膜袋放入烘箱中，加热30min(烘箱温度根据发泡剂种类而不同)；将发泡膨胀后的铝塑膜袋用悬挂法测试其重力F1，而后再将膨胀后的铝塑膜袋完全浸没在水中，用相同的悬挂法测试其在水中的重力F2，膨胀后铝塑膜体积V3＝(F1-F2)/(gρ 水)(其中g为重力常数，ρ 水为水的密度)；用相同方法测量膨胀前铝塑膜的体积V0，发泡剂膨胀气体体积V2＝V3-V0，发泡剂单位质量的发气量a＝V2/m2。
[DCR测试]
将电池调整到50％SOC的状态，以4C的倍率(对应放电电流为I)放电30s，记录30s放电前后的电压差ΔV。根据以下公式计算50％SOC对应的直流电阻DCR(Direct Current Resistence)：DCR＝ΔV/I。
[2C的放电容量保持率]
将新鲜电池以0.33C倍率在常温25℃进行满充后放电，此时放电容量记为初始容量C 0。然后，将电池在常温25℃环境下以2C倍率进行放电，此时的放电容量计为C 1。根据以下公式计算容量保持率：容量保持率＝C 1/C 0×100％。
[粘结力测试]
在平滑的钢板上贴双面胶，将集流体裁成宽度与双面胶相同，并平贴在双面胶表面。然后，将表面胶带裁成宽度与集流体相同，并贴附在集流体表面，并在头部连接长度大于钢板长度的A4纸条。用2.5kg滚轮在贴好的表面胶带上来回滚动，直至把胶带贴平。将钢板一端固定在拉力机(INSTRON，3365)上，A4纸连着表面胶带固定在拉力机另一端。以500mm/min的速度，将胶带进行剥离，得到剥离力曲线，从而计算出剥离力平均值记为集流体的粘结力。胶带粘结力～230N/m,若测试完未出现金属层剥离，则认定粘结力合格，若出现金属层剥离，则认定粘结力不合格。
[针刺测试]
将电芯进行满充后固定在夹具上，电芯的正负极连接电压探测线，电芯的多个位置布置感温线，直径3mm耐高温钢针以80mm/s的速度穿过电芯。在本文中，穿钉后出现冒烟、起火、防爆阀打开或电压降＞1.5V判定为没有通过穿钉测试；穿钉后不冒烟，不起火，防爆阀未打开且电压降≤1.5V判定为通过穿钉测试。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (31)

  1. 一种集流体，其特征在于，包括：
    金属层和粘结层；
    所述粘结层与所述金属层粘结，所述粘结层中包括粘结剂和发泡剂；其中，
    所述粘结层中的粘结剂和发泡剂满足：0.2≤(m2/m1)*a*ρ1≤20，其中，m1为所述粘结层中的粘结剂的质量，ρ1为所述粘结层中的粘结剂的密度，m2为所述粘结层中的发泡剂的质量，a为所述粘结层中的发泡剂的单位质量的发气量。
  2. 根据权利要求1所述的集流体，其特征在于，所述粘结层中的发泡剂与粘结剂满足：0.5≤(m2/m1)*a*ρ1≤10。
  3. 根据权利要求1或2所述的集流体，其特征在于，所述粘结层还包括导电剂，所述粘结层中的导电剂与所述粘结层的质量比为0.2～0.5。
  4. 根据权利要求1至3中任一项所述的集流体，其特征在于，所述集流体还包括支撑层，所述金属层与所述支撑层通过所述粘结层连接。
  5. 根据权利要求4所述的集流体，其特征在于，所述支撑层设置有贯穿所述支撑层的通孔，所述通孔内填充有填充层，所述填充层中包括发泡剂。
  6. 根据权利要求5所述的集流体，其特征在于，所述填充层中还包括粘结剂。
  7. 根据权利要求6所述的集流体，其特征在于，所述填充层中的发泡剂与粘结剂满足：1≤(m3/m4)*b*ρ2≤40；其中，m4为所述填充层中的粘结剂的质量，ρ2为所述填充层中的粘结剂的密度，m3为所述填充层中的发泡剂的质量，b为所述填充层中的发泡剂的单位质量的发气量。
  8. 根据权利要求7所述的集流体，其特征在于，所述所述填充层中的发泡剂与粘结剂满足：2≤(m3/m4)*b*ρ2≤20。
  9. 根据权利要求5至8中任一项所述的集流体，其特征在于，所述填充层还包括导电剂，所述填充层中的导电剂与所述填充层的质量比大于或等于0.4，可选为0.4～0.9。
  10. 根据权利要求4至9中任一项所述的集流体，其特征在于，所述支撑层的厚度为2～30μm，可选地，所述支撑层的厚度为3～12μm。
  11. 根据权利要求5至10中任一项所述的集流体，其特征在于，所述通孔的径向尺寸为50～2000μm。
  12. 根据权利要求5至11中任一项所述的集流体，其特征在于，相邻的所述通孔之间的距离为1～50mm。
  13. 根据权利要求4至12中任一项所述的集流体，其特征在于，所述支撑层的材料选自：聚酰胺、聚酰亚胺、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚萘二甲酸乙二醇酯、聚碳酸酯、聚乙烯、聚丙烯、聚丙乙烯、丙烯腈-丁二烯-苯乙烯共聚物、聚乙烯醇、聚苯乙烯、聚氯乙烯、聚偏氟乙烯、聚四氟乙烯、聚苯乙烯磺酸钠、聚乙炔、硅橡胶、聚甲醛、聚苯醚、聚苯硫醚、聚乙二醇、聚氮化硫类、聚苯、聚吡咯、聚苯胺、聚噻吩、聚吡啶、纤维素、淀粉、蛋白质、环氧树脂、酚醛树脂、及其衍生物、交联物或共聚物中的至少一种。
  14. 根据权利要求1至13中任一项所述的集流体，其特征在于，所述发泡剂在温度达到分解温度时分解，以使所述金属层断裂。
  15. 根据权利要求14所述的集流体，其特征在于，所述发泡剂的分解温度为80～250℃，可选为100～220℃，进一步地可选为110～210℃。
  16. 根据权利要求5至15中任一项所述的集流体，其特征在于，在所述发泡剂的分解温度大于或等于190℃的情况下，所述粘结层和/或所述填充层中还包括发泡助剂。
  17. 根据权利要求16所述的集流体，其特征在于，所述发泡助剂与所述发泡剂的质量比为0.1～10。
  18. 根据权利要求16或17所述的集流体，其特征在于，所述发泡助剂选自：氧化锌，硬酯酸锌，硬酯酸镉，硬酯酸钙，硬酯酸铅，硝基脲，硝基脲锌盐，尿素，硬酯酸，月桂酸，苯甲酸和水杨酸中的至少一种。
  19. 根据权利要求3或9所述的集流体，其特征在于，所述导电剂包括导电碳材料和金属材料。
  20. 根据权利要求19所述的集流体，其特征在于，所述导电碳材料包括：碳黑、石墨、乙炔黑、碳纳米管、石墨烯中的至少一种。
  21. 根据权利要求19或20所述的集流体，其特征在于，所述金属材料包括：银、铜、铁、镍、铝中的至少一种。
  22. 根据权利要求1至21中任一项所述的集流体，其特征在于，所述发泡剂选自：偶氮二甲酰胺，偶氮二异丁腈，偶氮甲酰胺甲酸钾，二亚硝基五次甲基四胺，三亚硝基三亚甲基三胺，4，4’-氧代双苯磺酰肼，对甲苯磺酰肼，苯磺酰肼，2，4-甲苯二磺 酰肼，硝基脲，硝基脲锌盐，偶氮二甲酸二乙酯，1,3-二磺酰肼苯中的至少一种。
  23. 根据权利要求1至22中任一项所述的集流体，其特征在于，所述粘结剂选自：聚丙烯、羧酸及衍生物接枝聚丙烯、聚乙烯、羧酸及衍生物接枝聚乙烯、乙烯-醋酸乙烯共聚物、聚氯乙烯、聚苯乙烯、羧甲基纤维素、聚丙烯酸酯、丁苯橡胶、聚丙烯酸钠、聚氨酯、芳砜接枝聚胺酯、苯并咪唑接枝聚胺酯、聚乙烯亚胺、聚偏氟乙烯、氯丁橡胶、丁腈橡胶、硅橡胶、聚醋酸乙烯酯、脲醛树脂、酚醛树脂、环氧树脂、钛酸酯偶联剂、锆类偶联剂、铝酸酯类偶联剂和硼酸酯偶联剂中的至少一种，可选为聚氨酯类和聚丙烯类中的至少一种，进一步可选为聚氨酯类。
  24. 根据权利要求1至23中任一项所述的集流体，其特征在于，所述金属层选自：Cu、Al、Ni、Ti、Pt、Fe、Co、Cr、W、Mo、Mg、Pb、In、Sn中的至少一种，可选为Cu或Al。
  25. 根据权利要求1至24中任一项所述的集流体，其特征在于，每层所述金属层的厚度为0.5～5μm，可选为0.7～2μm。
  26. 根据权利要求1至25中任一项所述的集流体，其特征在于，所述粘接层的厚度为0.5～5μm，可选为0.8～2μm。
  27. 一种极片，其特征在于，包括如权利要求1至26中任一项所述的集流体。
  28. 一种二次电池，其特征在于，包括如权利要求27所述的极片。
  29. 一种电池模块，其特征在于，包括如权利要求28所述的二次电池。
  30. 一种电池包，其特征在于，包括如权利要求28所述的二次电池或权利要求29所述的电池模块。
  31. 一种用电装置，其特征在于，包括如权利要求28所述的二次电池、权利要求29所述的电池模块、权利要求30所述的电池包中的至少一种。
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CN114015994A (zh) * 2021-11-03 2022-02-08 合肥国轩高科动力能源有限公司 一种超薄复合集流体的制备方法

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