Composite separator, secondary battery, and electric device

Abstract

The invention discloses a composite isolating membrane, a secondary battery and an electric device. The secondary battery comprises a composite isolating membrane, a positive electrode active material layer located on one side of the composite isolating membrane and a negative electrode active material layer located on the other side of the composite isolating membrane, the composite isolating membrane comprises a polymer layer and conductive structures located on the two sides of the polymer layer, the conductive structures are provided with through holes, and the through holes are communicated with the polymer layer. The porosity of the composite isolating membrane is 15-30%, and the average pore diameter of the pore structure is 100 nm to 20 [mu] m. The secondary battery can relieve cycle performance reduction caused by poor electrolyte infiltration, so that the secondary battery has relatively good cycle performance and safety.

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and in particular, to a composite isolation membrane, a secondary battery, and an electrical device. Background Art

[0002] With the development and promotion of battery technology, secondary batteries such as lithium-ion batteries are used in a variety of electrical devices to provide clean electricity. Secondary batteries store and supply electricity through the intercalation and deintercalation of energy storage ions, such as lithium ions, between the positive and negative electrodes. The volume of the positive and negative active materials will expand during the battery cycle, which will cause the electrolyte between the internal electrodes of the battery to be squeezed out, resulting in poor electrolyte infiltration.

[0003] Therefore, the current composite separators, secondary batteries, battery devices, and electrical devices still need to be improved. Summary of the invention

[0004] In view of the above problems, the present application provides a composite isolation membrane, a secondary battery and an electrical device.

[0005] In one aspect of the present application, the present application proposes a secondary battery. The secondary battery comprises: a composite separator, and a positive electrode active material layer located on one side of the composite separator, and a negative electrode active material layer located on the other side of the composite separator, the composite separator comprises a polymer layer, and a conductive structure located on both sides of the polymer layer, the conductive structure has a through hole, the porosity of the composite separator is 15-30%, and the average pore size of the polymer layer is 100nm-20μm. The secondary battery adopts a composite separator with a conductive function, and uses the electrolyte stored in the polymer layer to achieve the infiltration of the electrode active layer, which can alleviate the degradation of the cycle performance caused by poor electrolyte infiltration, and thus has good cycle performance and safety. That is to say, the present application improves the ability of the electrolyte to infiltrate the active material layer by providing a composite separator with a certain pore size and porosity and a conductive function, and releases the electrolyte stored in the polymer layer in the composite separator when the active material expands.

[0006] According to an embodiment of the present application, the polymer layer includes a first sublayer and a second sublayer, the first sublayer is located on a side close to the positive electrode active material layer, the second sublayer is located on a side close to the negative electrode active material layer, the first sublayer has a plurality of first pores, the second sublayer has a plurality of second pores, the average pore size of the first pores is 10nm-20μm, and the average pore size of the second pores is 500nm-20μm. Thus, the ability of the polymer layer to accommodate electrolytes can be further improved.

[0007] According to an embodiment of the present application, the average pore size of the first pores is the same as the average pore size of the second pores. Thus, the steps of preparing the polymer layer can be simplified and the production cost can be reduced.

[0008] According to an embodiment of the present application, the average pore size of the first pores is different from the average pore size of the second pores, the average pore size of the first pores is 10 nm-1 μm, and the average pore size of the second pores is 1 μm-20 μm. Thus, the ability of the polymer layer to accommodate electrolytes can be further improved.

[0009] According to an embodiment of the present application, the porosity of the first sublayer is 10-20%, and the porosity of the second sublayer is 20-30%. Thus, the mechanical properties of the membrane layer can be maintained to meet the requirements of the battery while maintaining a certain capacity of the polymer layer to accommodate electrolyte.

[0010] According to an embodiment of the present application, the material of the polymer layer includes at least one of epoxy resin, terephthalate, polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide and polyamide. The polymer layer formed by the above materials has appropriate mechanical properties.

[0011] According to an embodiment of the present application, the conductive structure includes a first conductive layer and a second conductive layer, the first conductive layer is in contact with the positive electrode active material, the second conductive layer is in contact with the negative electrode active material, the first conductive layer has a first through hole, the second conductive layer has a second through hole, and the average pore size of the first through hole and the second through hole are independently 500nm-20μm. Thus, the structure of the secondary battery can be further simplified.

[0012] According to an embodiment of the present application, the average pore diameters of the first through holes and the second through holes are independently 1 μm-10 μm, thereby further improving the electrolyte wettability of the composite isolation membrane.

[0013] According to an embodiment of the present application, the porosity of the first conductive layer and the second conductive layer is independently 15-30%, thereby further improving the electrolyte wettability of the composite isolation membrane.

[0014] According to an embodiment of the present application, the conductive structure includes at least one of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, silver and silver alloy, the positive electrode active material layer includes at least one of lithium phosphate and lithium transition metal oxide, and the negative electrode active material layer includes at least one of artificial graphite and natural graphite.

[0015] According to an embodiment of the present application, the secondary battery is a wound battery, the wound battery includes a plurality of the composite separators, the plurality of the composite separators are separated by insulating separators, the composite separators include a plurality of plane portions and a plurality of bends, and the adjacent plane portions are connected by the bends. Thus, the performance of the secondary battery can be further improved.

[0016] In another aspect of the present application, the present application proposes a composite isolation membrane. The composite isolation membrane includes: a polymer layer, and a conductive structure located on both sides of the polymer layer, the conductive structure has through holes, the porosity of the composite isolation membrane is 15-30%, and the average pore size of the polymer layer is 100nm-20μm. The composite isolation membrane has a good ability to preserve electrolyte and has the function of current collector. The conductive structure can be used to directly form an active material layer, so it can alleviate the degradation of cycle performance caused by poor electrolyte infiltration, and thus has good cycle performance and safety.

[0017] According to an embodiment of the present application, the polymer layer includes a first sublayer and a second sublayer, the first sublayer has a plurality of first pores, the second sublayer has a plurality of second pores, the average pore size of the first pores is 10nm-1μm, and the average pore size of the second pores is 1μm-20μm. Thus, the performance of the composite isolation membrane can be further improved.

[0018] According to an embodiment of the present application, the conductive structure includes a first conductive layer and a second conductive layer, the first conductive layer is located on one side of the first sub-layer, the second conductive layer is located on one side of the second sub-layer, the first conductive layer has a first through hole, the second conductive layer has a second through hole, the average pore size of the first through hole and the second through hole is independently 1-10 μm, and the porosity of the first conductive layer and the second conductive layer is independently 10-30%. Thus, the performance of the composite isolation membrane can be further improved.

[0019] In another aspect of the present application, the present application proposes an electric device. The electric device includes the secondary battery described above. Thus, the electric device has all the features and advantages of the secondary battery and the composite isolation membrane described above. In general, the electric device has good cycle performance and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0021] Figure 1 A schematic diagram showing the structure of a secondary battery according to an embodiment of the present application; Figure 2 A schematic diagram of the exploded structure of a secondary battery according to an embodiment of the present application is shown; Figure 3 A schematic diagram showing the structure of a composite isolation membrane according to an embodiment of the present application is shown; Figure 4 A schematic diagram showing the structure of a composite isolation membrane according to another embodiment of the present application is shown; Figure 5 A schematic diagram showing the structure of a secondary battery according to an embodiment of the present application is shown; Figure 6 A schematic diagram of the structure of an electric device according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0022] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the description and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0024] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0025] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0026] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0027] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "upper", "lower", "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0028] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0029] Lithium-ion batteries will expand in volume during the cycle process, especially for negative electrode active material systems such as graphite and silicon. This process will cause the electrolyte between the pole pieces inside the battery cell and inside the pole pieces to be squeezed out due to the volume expansion of the active materials, resulting in poor electrolyte infiltration in the pole pieces. Especially for wound batteries, the problem of poor electrolyte infiltration at the corners is particularly serious because the expansion force is greater and the stress is concentrated at the corners. Poor electrolyte infiltration will cause some lithium ions to be enriched on the surface of the negative electrode material, resulting in lithium precipitation, further leading to the formation of lithium dendrites, and may pierce the diaphragm to cause a short circuit between the positive and negative electrodes.

[0030] In some embodiments, the storage capacity of the electrode assembly for the electrolyte can be improved by introducing a hole structure into the current collector or increasing the thickness of the diaphragm, but the above improvements often require complicating the structure of the current collector.

[0031] In view of this, the present application proposes a composite isolation membrane and a secondary battery. By adopting a polymer layer with an appropriate average pore size and porosity, a sufficient amount of electrolyte can be stored inside the polymer layer, and through the conductive structure, it has the function of a current collector, so that the infiltration of the active material layer can be better achieved: the active material layer is formed on the conductive structure on both sides of the polymer layer. On the one hand, this structure can release the electrolyte stored in the polymer layer to improve the electrolyte infiltration on the surface of the electrode when the electrode active material expands, thereby alleviating the problems caused by poor electrolyte infiltration. On the other hand, it can also increase the integration of the internal structure of the battery and achieve the infiltration of the active layer using a simple structure.

[0032] In one aspect of the present application, the present application provides a secondary battery. The secondary battery includes a composite separator, a positive electrode active material layer and a negative electrode active material layer. The positive electrode active material layer is located on one side of the composite separator, and the negative electrode active material layer is located on the other side of the composite separator. Figure 3The composite isolation membrane includes a polymer layer 110 and a conductive structure located on both sides of the polymer layer 110, such as 120A and 120B shown in the figure. The polymer layer 110 has a pore structure (not shown in the figure), which can be used to absorb electrolyte and release the electrolyte when squeezed by the active material. The conductive structure has through holes (not shown in the figure) to provide a circulation path for the electrolyte stored in the polymer layer. The porosity of the composite isolation membrane is 15-30%, and the average pore size of the polymer layer is 100nm-20μm. The secondary battery adopts a composite isolation membrane with a pore structure with good liquid retention ability and conductive function, so it has a good ability to retain electrolyte and a simple structure with high integration, which can alleviate the degradation of cycle performance caused by poor electrolyte infiltration, so it has good cycle performance and safety.

[0033] Specifically, the secondary battery proposed in the present application adopts a composite separator to integrate the positive and negative current collectors on both sides of the polymer layer, and provides a path for the circulation of the electrolyte through a conductive structure with through holes, thereby realizing the conductive function and further simplifying the internal structure of the battery. In addition, the use of a polymer layer with an appropriate average pore size can play a role in separating the conductive structures carrying the positive and negative active materials, and at the same time, the above-mentioned pore size can be used to store a sufficient amount of electrolyte inside the polymer layer. At this time, even if the electrolyte on the electrode surface is squeezed out due to expansion of the positive and negative active materials during the cycle, the electrolyte loaded in the pore structure in the polymer layer can also be released by extrusion at this time, thereby maintaining the electrolyte infiltration condition of the entire surface of the composite separator in good condition.

[0034] Porosity In this application, porosity is used to evaluate the proportion of the physical structure and pores / through holes in the film layer. The greater the porosity, the higher the proportion of pores and / or through holes in the film layer structure. It can be understood by those skilled in the art that in the film layer structure of the same material and the same thickness, the greater the porosity, the lower the mechanical strength.

[0035] The porosity in this application can be measured by weighing. For example, first weigh the weight of the membrane layer with pores / through holes of volume V and record it as m 0 , completely immerse the weighed film layer in the n-hexadecane reagent for a period of time, such as 2 h. Then take out the film layer and wipe off the residual reagent on its surface with dust-free paper, and weigh the film layer and record it as m 1 , the porosity is calculated using the following formula:

[0036] In the above formula is the porosity, unit is %; is the density of n-hexadecane, in g / cm3 .

[0037] Average pore size In this application, the average pore size is used to evaluate the size of the physical structure and the pores / through-holes in the membrane layer. For the polymer layer, the average pore size is the average pore size of the pore structure; for the conductive structure, the average pore size is the average pore size of the through-holes. The average pore size in this application can be obtained by testing using the following method: The battery cells were placed in a 1.0 mol / L sodium hydroxide aqueous solution at room temperature for discharge treatment. After the discharge was completed, they were manually disassembled to obtain a composite isolation membrane loaded with active materials. A cryo-focused ion beam (FIB) was used to perform fine slices layer by layer at different thickness positions (the smallest scale could reach nanoscale thin slices), and the polymer layer was separated. Different area regions of the polymer layer were then cut to obtain multiple samples.

[0038] The test instrument used is ASAP2460-physical adsorption analyzer. The samples after drying and degassing are placed in liquid nitrogen, and different test pressures are adjusted to measure the adsorption amount of nitrogen respectively, and the adsorption and desorption isotherms are plotted. Then, the pore volume and specific surface area of ​​the porous carbon material are obtained according to the adsorption and desorption isotherms, and then the average pore size is calculated. The average value of multiple samples is taken to obtain the average pore size of the membrane layer to be tested.

[0039] According to an embodiment of the present application, when the overall porosity of the composite isolation membrane is 10-30%, it is beneficial to maintain the overall mechanical properties of the composite isolation membrane to meet the requirements of the battery, support the positive and negative active materials formed on the conductive structure, and maintain the overall mechanical structure of the composite isolation membrane structure stable during preparation, transportation and use. The average pore size of the polymer layer in the composite isolation membrane can be 100nm-20μm. When the average pore size is within the above range, the resistance of the electrolyte to enter the pore structure can be reduced, which is conducive to using the pore structure to store the electrolyte. In some embodiments, the average pore size of the pore structure can be 1μm-20μm. As a result, the resistance of the electrolyte to enter the pore structure can be further reduced.

[0040] In some embodiments, the pore structure of the polymer layer may be through-holes, that is, the electrolyte can flow from one side of the polymer layer to the other side of the polymer layer through the pore structure, thereby improving the ability of the polymer layer to release the electrolyte when squeezed.

[0041] According to the embodiments of the present application, the material forming the polymer layer is not particularly limited, and those skilled in the art may use a familiar polymer with insulating properties to form the polymer layer. For example, the polymer layer material may be formed by a polymer material having good stability in the electrolyte, and the polymer may not have the ability to swell in the electrolyte. As mentioned above, the polymer layer of the present application achieves the storage of the electrolyte through an open pore structure, and therefore, the polymer material itself may not have the ability to adsorb the electrolyte. The polymer layer formed by a polymer that does not have swelling properties can maintain a relatively stable volume during use, thereby improving the stability of the conductive structure loaded thereon and reducing the probability of the conductive structure peeling off from the polymer layer.

[0042] In some specific embodiments, the polymer layer can be formed using a commonly used secondary battery diaphragm material. The diaphragm material has good electrolyte stability and relatively low production cost. For example, the material forming the polymer layer may include at least one of epoxy resin, terephthalate, polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide and polyamide. For example, the following polymer materials can be used as the principle of forming the polymer layer: terephthalate, polyethylene, polypropylene, epoxy resin, polyamide, polyimide, polyester, polyolefin, polyacetylene, siloxane polymer, polyether, polyol, polysulfone, polysaccharide polymer, amino acid polymer, polysulfide polymer, aromatic ring polymer, any one or more thereof, and aromatic heterocyclic polymers, epoxy resins, phenolic resins, derivatives thereof, cross-linked products and / or copolymers. The polymer layer formed by the above materials has appropriate mechanical properties, which can further improve the performance of the composite isolation membrane.

[0043] In some examples, the secondary battery may be a wound battery. The wound battery includes a plurality of the composite isolation membranes, the plurality of the composite isolation membranes are separated by insulating membranes, the composite isolation membrane includes a plurality of plane portions and a plurality of bends, and the adjacent plane portions are connected by the bends. Since the composite isolation membrane proposed in the present application has a certain ability to store electrolyte, it can better alleviate the problem of high stress at the corners of the wound battery and severe extrusion of electrolyte.

[0044] Below, taking a secondary battery as a wound battery as an example, various structures of the secondary battery are described in detail. Those skilled in the art can understand that the following embodiments are only for illustrating the secondary battery proposed in this application, and cannot be understood as limiting the type of the secondary battery.

[0045] In this embodiment, the pore structure in the polymer layer in the composite separator may have different average pore sizes and / or distribution densities in different regions. For example, the region in the polymer layer corresponding to the corner of the wound battery may have a higher porosity to store more electrolyte, and the region corresponding to the large surface of the battery may have a lower porosity to provide better mechanical support. In this embodiment, the average pore size of the polymer may be the average of the pore sizes in all regions, and the porosity may also be the average porosity of all regions.

[0046] In other examples, the pore structure in the polymer layer can be evenly distributed, that is, the density of the pore structure at different positions of the polymer layer and the average pore size of the pores can be consistent. This can reduce the preparation cost of the polymer layer on the one hand, and on the other hand, make the entire polymer layer have more uniform mechanical properties, and when dealing with stress such as expansion generated by the active material, the stress can be more evenly distributed.

[0047] In some embodiments, reference Figure 4 , the polymer layer may include a first sublayer 110A and a second sublayer 110B. The first sublayer 110A is located on the side close to the positive electrode active material, and the second sublayer 110B is located on the side close to the negative electrode active material. The first sublayer 110A has a plurality of first holes, and the second sublayer 110B has a plurality of second holes. In this embodiment, the materials constituting the first sublayer 110A and the second sublayer 110B may be the same or different, and the average pore size and distribution density of the first and second holes may be the same or different. The polymer layer is composed of two sublayers, which can reduce the depth of the pores that form the pore structure that penetrates the entire polymer layer. On the one hand, it can reduce the probability that the pores do not penetrate the polymer due to the large pore depth, and the electrolyte can only enter and exit from one side of the polymer membrane. On the other hand, it can also reduce the difficulty in forming the pore structure.

[0048] According to an embodiment of the present application, the first sublayer and the second sublayer may be bonded and fixed by a binder. For example, a binder such as polyvinylidene fluoride (PVDF) may be mixed with deionized water to form a uniform slurry, and the slurry is used to bond the large surfaces of the two polymer sublayers together to achieve the fixation of the first sublayer and the second sublayer.

[0049] According to an embodiment of the present application, the first hole is close to one side of the positive electrode active material layer. During the battery cycle, the expansion of the positive electrode active material is relatively small, so the first hole can have a smaller average pore size, for example, the average pore size of the first hole can be 10nm-20μm. The second hole is close to one side of the negative electrode active material layer. During the battery cycle, the expansion of the negative electrode active material is relatively large, so the first hole can have a larger average pore size, for example, 500nm-20μm.

[0050] In some embodiments, the Young's modulus of the polymer layer can be adjusted to be 1 MPa to 100 MPa by adjusting the pore structure in the polymer layer. Thus, the film layer has appropriate rigidity and toughness, and is suitable for providing support for the conductive structure and the subsequent loaded electrode active materials.

[0051] In the present application, the definition and measurement method of Young's modulus may include any conventional method in the art. For example, Young's modulus can be measured by the following process: cut the sample to be tested into 15mm×200mm specimens, measure the thickness h (μm) of the specimen with a micrometer, and use a Gotech tensile machine to perform a tensile test at room temperature and pressure (25 degrees Celsius, 0.1MPa). Set the initial position so that the sample between the clamps is 50 mm long and the stretching speed is 5 mm / min. Record the tensile load L (N) and the equipment displacement y (mm) until the sample breaks, then calculate the stress ε (GPa) = L / (15×h), strain η = y / 50, draw a stress-strain curve, and take the initial linear region of the curve. The slope of the curve is the Young's modulus.

[0052] In some specific embodiments, the average pore size of the first pores may be 10 nm to 1 μm, and the porosity of the first sublayer 110A may be 10% to 20%. The average pore size of the second pores may be 1 μm to 20 μm, and the porosity of the second sublayer 110B may be 20% to 30%.

[0053] In some embodiments, when the average pore sizes of the first and second pores are inconsistent, in order to maintain more uniform mechanical properties of the polymer layer and reduce the probability of excessive local stress, the porosity of the first and second sub-layers can be made consistent by adjusting the pore content.

[0054] In some embodiments of the present application, the polymer layer and the pore structure therein can be prepared by a method commonly used in the art for forming a pore structure in a polymer material. For example, the polymer particles can be melted, mixed, molded and extruded to obtain an organic polymer sheet, the organic polymer sheet is stretched a certain multiple along the length direction using a bidirectional asynchronous stretching machine, and then stretched along the width direction of the organic polymer sheet, and the stretching multiples in the length and width directions are controlled to obtain a pore structure with different average pore sizes, thereby obtaining a polymer layer with appropriate porosity. When the polymer layer includes the first and second sublayers, the stretching multiples in the length and width directions when preparing the first and second sublayers can be determined according to the target pore size and porosity of each sublayer. When the prepared polymer layer needs to have different porosities and / or average pore sizes in different regions, the width or length direction can be stretched respectively for different regions of the polymer layer, and the stretching multiples when different regions are stretched in the same direction are different.

[0055] According to the embodiments of the present application, reference Figure 4The conductive structure may include a first conductive layer 120A and a second conductive layer 120B. The first conductive layer 120A is in contact with the positive electrode active material and is used to carry the positive electrode active material. The second conductive layer 120B is in contact with the negative electrode active material. The first conductive layer has a first through hole, as shown in FIG. Figure 4 , so that the electrolyte stored in the first sublayer 110A can penetrate the first conductive layer. The second conductive layer has a second through hole, as shown in FIG. Figure 4 , so that the electrolyte stored in the second sublayer 110B can pass through the second conductive layer. The sizes of the first through hole and the second through hole are independently 500nm-20μm. Thus, the performance of the composite isolation membrane can be further improved.

[0056] In some embodiments, the conductive structure may be formed of a material having electrical conductivity, such as a metal. For example, the metal includes any one or more of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, iron, iron alloy, titanium, titanium alloy, silver, and silver alloy. For example, aluminum metal may be used to form a first conductive layer in contact with the positive electrode active material layer, and copper metal may be used to form a second conductive layer in contact with the negative electrode active material layer.

[0057] In the present application, the size of the through-holes may be an average pore size determined by the aforementioned definition and measurement method.

[0058] According to an embodiment of the present application, similar to the first and second holes, the size of the first through hole and the second through hole, that is, the average pore size, may be the same or different. In some embodiments, the average pore size of the first through hole and the second through hole may be 1 μm-10 μm, respectively, and the porosity of the first conductive layer and the second conductive layer may be 15-30%, respectively. Thus, the electrolyte wettability of the composite isolation membrane can be further improved.

[0059] In some embodiments, when the composite isolation membrane includes a first sublayer and a second sublayer, the average pore size of the first through hole can be consistent with the average pore size of the first hole in the first sublayer, and the average pore size of the second through hole can be consistent with the average pore size of the second hole in the second sublayer. Similarly, the porosity of the first conductive layer can be consistent with the porosity of the first sublayer, and the porosity of the second conductive layer can be consistent with the porosity of the second sublayer. In this way, the consistency of the polymer sublayer and the conductive structure on the same side can be improved, which is convenient for the circulation of the electrolyte, and can also alleviate the uneven stress distribution during the cycle caused by the difference in the structures of the two, thereby affecting the overall structural stability of the composite isolation membrane.

[0060] For example, in some embodiments, a conductive structure can be formed on the surface of the polymer layer by, but not limited to, methods such as vapor deposition, electroless plating, evaporation plating, adhesion, etc. Specifically, the obtained polymer layer can be cleaned by pickling, alkali washing, etc., and then placed in a vacuum evaporation chamber. A mask plate is placed on the polymer surface, and a conductive metal is deposited on the surface of the polymer layer at an evaporation temperature of 1300°C to 2000°C. Alternatively, a metal layer can also be formed by deposition and other methods, and a through-hole can be formed by laser etching to obtain a conductive structure.

[0061] When the polymer layer includes a first and a second sub-layer, a first conductive layer can be first formed on the surface of the first sub-layer, and a second conductive layer can be formed on the surface of the second sub-layer. Subsequently, the sides of the two insulating sub-layers without the conductive structure can be bonded by adhesion.

[0062] In the present application, the thickness of the polymer layer can be adjusted according to the material and porosity of the formed polymer, as long as it can meet the requirements of mechanical properties, achieve self-support and be sufficient to load the conductive structure and the positive and negative active materials. Similarly, the thickness of the conductive structure can also be adjusted according to conditions such as the size and proportion of the through-holes, and the metal forming the conductive structure, etc., as long as it can load the positive and negative active materials and form a stable solid connection with the polymer layer. For example, in some embodiments of the present application, the thickness of the polymer layer can be 1μm to 10μm, and the thickness of the conductive structure can be 1μm to 10μm. Specifically, the thickness of the conductive structure can be lower than the thickness of the polymer layer. Specifically, the sum of the thicknesses of the conductive structures on both sides of the polymer layer does not exceed the thickness of the polymer layer.

[0063] It should be particularly noted here that when the polymer layer includes a first and a second sub-layer, the thickness of the polymer layer is the sum of the thicknesses of the two sub-layers, and the sum of the thicknesses of the two sub-layers can be 1μm to 10μm. The conductive structures are arranged on two opposite surfaces of the polymer layer, so the thickness of the conductive structure is the thickness of the conductive structure on the single-side surface of the polymer layer. That is to say, the thicknesses of the first conductive layer 120A and the second conductive layer 120B can be independently 1μm to 10μm respectively.

[0064] According to the embodiments of the present application, the specific methods for forming the positive electrode active material and the negative electrode active material on the conductive structure can be selected as common methods in the art, such as coating, deposition, etc. Coating includes any one or more of roll coating, extrusion coating, knife coating, and gravure coating. Deposition includes any one or more of physical deposition and chemical deposition.

[0065] According to an embodiment of the present application, the electrolyte may be a liquid electrolyte commonly used in the art. For example, the electrolyte may include solvents such as cyclic carbonates and chain carbonates, and may also have lithium salts, as well as additives having functions such as improving gas production and stabilizing SEI films. For example, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be selected from ether solvents. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether. The lithium salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalateborate, lithium dioxalateborate, lithium difluorodioxalatephosphate and lithium tetrafluorooxalatephosphate. The additive may include a negative electrode film-forming additive or a positive electrode film-forming additive. The additive may also include an additive capable of improving certain properties of the lithium ion secondary battery, such as an additive for improving the overcharge / fast charge performance of the lithium ion secondary battery, an additive for improving the high temperature performance of the lithium ion secondary battery, an additive for improving the low temperature performance of the lithium ion secondary battery, etc. For example, the additive may include at least one of cyclic sulfonate, 1,3-propane sultone, butylene carbonate (BC), fluoroethylene carbonate (FEC), 1,4-butyrolactone (GBL), cyclopentane sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0066] In some specific embodiments, the electrolyte may contain EC (ethylene carbonate), PC (polycarbonate), DMC (dimethyl carbonate), the additives may include VC, DTD, PS, etc., and the lithium salt may include lithium hexafluorophosphate.

[0067] According to an embodiment of the present application, the positive electrode active material layer includes at least one of a lithium-containing phosphate and a lithium transition metal oxide. In some embodiments, the lithium-containing phosphate and / or lithium transition metal oxide contained in the positive electrode active material may also include a modified lithium iron phosphate and / or lithium transition metal oxide, and at least one of lithium manganese phosphate and lithium-rich manganese-based materials, including but not limited to. The negative electrode active material layer includes at least one of a graphite negative electrode material and a silicon-based negative electrode material, for example, it may include at least one of artificial graphite and natural graphite.

[0068] According to the embodiments of the present application, reference Figure 5, there are further insulating membranes on both sides of the composite isolation membrane 100. Specifically, the insulating membrane can be a secondary battery membrane commonly used in the art, which is used to insulate and isolate the electrode active materials on the surfaces of the multiple composite isolation membranes. For example, referring to Figure 5 , may include a first separator 200 and a second separator 300 to achieve insulation between the positive electrode and the negative electrode when forming a wound battery or the like.

[0069] According to the embodiments of the present application, the secondary battery proposed in the present application can be a square shell battery or a cylindrical battery. According to the embodiments of the present application, the secondary battery can be a soft pack battery or a hard shell battery. Figure 1 2 is a secondary battery 10 having a square structure as an example. Figure 2 The secondary battery may have an outer package, and the outer package may include a shell 101 and a cover plate 103. The shell 101 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 101 has an opening connected to the receiving cavity, and the cover plate 103 can be covered on the opening to close the receiving cavity. One or more electrode assemblies 102 can be accommodated in the receiving cavity, and the electrolyte is infiltrated in the electrode assembly 102. The aforementioned composite isolation membrane can be sealed in the electrode assembly 102 by winding or the like.

[0070] In another aspect of the present application, the present application provides a composite isolation membrane. Figure 3 , the composite isolation membrane includes a polymer layer 110 and a conductive structure located on both sides of the polymer layer, such as 120A and 120B shown in the figure. The composite isolation membrane can be the composite isolation membrane in the aforementioned secondary battery. Specifically, the polymer layer has pores that can pass the electrolyte, and the conductive structure has through holes to provide a passage for the electrolyte to flow. The porosity of the composite isolation membrane is 15-30%, and the average pore size of the polymer layer is 10nm-20μm. The composite isolation membrane has an average pore size suitable for storing electrolytes and has the function of a current collector, which can alleviate the degradation of cycle performance due to poor electrolyte infiltration, and therefore has good cycle performance and safety.

[0071] According to the embodiments of the present application, reference Figure 4 , the polymer layer may include a first sublayer 110A and a second sublayer 110B, the first sublayer having a plurality of first pores, the second sublayer having a plurality of second pores, the average pore size of the first pores being 10nm-1μm, and the average pore size of the second pores being 1μm-20μm. Thus, the performance of the composite isolation membrane may be further improved. Similarly, the terms such as "first pore", "second pore", "average pore size" in the composite isolation membrane may also have the same meaning as the corresponding terms in the composite isolation membrane in the aforementioned secondary battery.

[0072] According to an embodiment of the present application, similarly, the conductive structure includes a first conductive layer 120A and a second conductive layer 120B, the first conductive layer is located on one side of the first sub-layer, the second conductive layer is located on one side of the second sub-layer, the first conductive layer has a first through hole, the second conductive layer has a second through hole, the average pore size of the first through hole and the second through hole is independently 1-10 μm, and the porosity of the first conductive layer and the second conductive layer is independently 10-30%. Thus, the performance of the composite isolation membrane can be further improved. Similarly, the size of the first and second through holes can be the average pore size of the through holes, the size of the first through hole can be consistent with the average pore size of the first hole in the first sub-layer, and the size of the second through hole can be consistent with the average pore size of the second hole in the second sub-layer.

[0073] In general, the polymer layer of the composite isolation membrane has an average pore size suitable for storing electrolyte, and the through-holes of the conductive structure allow the electrolyte to flow through the conductive structure. When the positive and negative active materials loaded by the composite isolation membrane, especially the negative active materials, expand during the cycle, the electrolyte stored in the pore structure of the polymer layer can be squeezed out to achieve the effect of wetting the surface of the composite isolation membrane. The overall porosity of the composite isolation membrane can ensure the overall mechanical properties of the composite membrane and meet the requirements of the secondary battery for the mechanical strength of the current collector and other properties. In another aspect of the present application, the present application provides a battery device. The battery device includes the secondary battery or the composite isolation membrane described above. Therefore, the battery device has all the characteristics and advantages of the aforementioned secondary battery and the composite isolation membrane. In general, the battery device has good cycle performance and safety.

[0074] In another aspect of the present application, the present application proposes an electric device. The electric device includes the battery device described above. Thus, the electric device has all the features and advantages of the secondary battery and the composite isolation membrane of the battery device described above. In general, the electric device has good cycle performance and safety.

[0075] In the present application, the electrical device may be, for example, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0076] Figure 6The power consumption device 2 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of the battery, a battery pack or a battery module can be used.

[0077] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a lithium-ion secondary battery may be used as a power source.

[0078] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0079] Example 1 Step 1: The organic polymer polypropylene particles are melted, mixed, and extruded to obtain an organic polymer casting sheet, and the casting sheet is stretched along the length and width directions using a bidirectional asynchronous stretching machine, and the first sublayer of the required size is obtained by die cutting; the second sublayer is obtained in the same way. The pore size and porosity of the polymer layer are tested, and the average pore size of the first sublayer of Example 1 is 100nm and the porosity is 12%; the average pore size of the second sublayer is 3μm and the porosity is 21%. A binder such as polyvinylidene fluoride (PVDF) is mixed with deionized water to form a uniform slurry, and the first polymer layer and the second polymer layer are bonded together using this slurry.

[0080] Step 2: Use a mask with a porosity of 20% and a pore size of 10 μm to cover the side of the first sublayer away from the second sublayer, and use a mask without gaps to cover the side of the second sublayer away from the first sublayer. Then, a porous aluminum-based conductive layer with a thickness of 3 μm is obtained on the side of the first sublayer away from the second sublayer by physical vapor deposition. In the same way, a porous copper-based conductive layer is obtained on the side of the second sublayer away from the first sublayer.

[0081] Step 3: Mix graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and binder sodium carboxymethyl cellulose (CMC) in a certain mass ratio, add solvent deionized water, and stir and mix thoroughly to obtain negative electrode slurry. 2 MnO 3 0.6LiNi 0.5 Mn 0.5 O 2, conductive agent acetylene black, and binder PVDF (polyvinylidene fluoride) are mixed in a weight ratio of 94:4:2, and solvent N-methylpyrrolidone is added, and the mixture is stirred and mixed to obtain positive electrode slurry. The negative electrode slurry is applied to the copper-based conductive layer of the composite isolation membrane on the side away from the second sublayer, and the positive electrode slurry is applied to the aluminum-based conductive layer of the composite fluid on the side away from the first sublayer, and then a pole piece with a positive electrode on one side and a negative electrode on the other side is formed through baking, cold pressing, die cutting and other processes.

[0082] Step 4: Provide an electrolyte. In an argon atmosphere glove box with a water content of <10 ppm, mix EC (ethylene carbonate), PC (polycarbonate), and DMC (dimethyl carbonate) in a weight ratio of EC:PC:DMC=3:3:3, and then add LiPF6, VC, DTD and PS. After stirring evenly, an electrolyte is obtained, wherein the concentration of LiPF6 in the lithium-ion battery electrolyte is 1 mol / L, and the mass percentages of VC, DTD, and PS are 3%, 1%, and 1%, respectively, to obtain an electrolyte.

[0083] Step 5: Form a bare cell by winding the die-cut multiple groups of membranes, each group of membranes is composed of a first diaphragm, a composite electrode, and a second diaphragm stacked in sequence. Put the bare cell into an outer package and inject the electrolyte, and then obtain a lithium-ion secondary battery through formation, aging and other processes.

[0084] Embodiment 2: The remaining operations are the same as those in Example 1, except that in step 1, the average pore size of the second sublayer is 10 μm, the porosity is 25%, and the other steps and conditions remain unchanged.

[0085] Embodiment 3: The difference from Example 1 is that in step 1, the average pore size of the second sublayer is 18 μm, the porosity is 28%, and the other steps and conditions remain unchanged.

[0086] Embodiment 4: The difference from Example 1 is that in step 1, the average pore size of the first sublayer is 500 nm, the porosity is 15%, and the other steps and conditions remain unchanged.

[0087] Embodiment 5: The difference from Example 2 is that in step 1, the average pore size of the first sublayer is 500 nm, the porosity is 15%, and the other steps and conditions remain unchanged.

[0088] Embodiment 6: The difference from Example 3 is that in step 1, the average pore size of the first sublayer is 500 nm, the porosity is 15%, and the other steps and conditions remain unchanged.

[0089] Embodiment 7: The difference from Example 1 is that in step 1, the average pore size of the first sublayer is 1 μm, the porosity is 19%, and the other steps and conditions remain unchanged.

[0090] Embodiment 8: The difference from Example 2 is that in step 1, the average pore size of the first sublayer is 1 μm, the porosity is 19%, and the other steps and conditions remain unchanged.

[0091] Embodiment 9: The difference from Example 3 is that in step 1, the average pore size of the first sublayer is 1 μm, the porosity is 19%, and the other steps and conditions remain unchanged.

[0092] Embodiment 10: The remaining operations are the same as those in Example 1. The difference from Example 1 is that in step 1, the average pore size of the first and second sub-layers are both 10 μm, and the porosity is both 25%. The other steps and conditions remain unchanged.

[0093] Embodiment 11: The remaining operations are the same as those in Example 1, except that in step 1, the average pore size of the second sublayer is 1 μm, and the porosity is 19%. The other steps and conditions remain unchanged.

[0094] Comparative Example 1: The difference from Example 1 is that it is not necessary to make holes on the first polymer layer, the second polymer layer and the conductive layer.

[0095] Comparative Example 2 The difference from Example 1 is that the average pore diameters of the first and second polymer layers are both 25 μm, the porosities are both 50%, and the other steps and conditions remain unchanged.

[0096] Comparative Example 3 The difference from Example 1 is that the average pore diameters of the first and second sub-layers are both 100 nm, the porosities are both 12%, and the other steps and conditions remain unchanged.

[0097] The composite isolation membrane and the secondary battery prepared in the above-mentioned embodiments and comparative examples were subjected to performance tests: Pore ​​size test of composite isolation membrane: The first polymer layer and the second polymer layer were sampled respectively, and photographs of the samples magnified 30,000 times were obtained by scanning electron microscopy, and the average pore size of the sample pores was obtained by combining software such as Nano Measurer and Origin.

[0098] Porosity test of composite isolation membrane: The porosity of the first polymer layer and the second polymer layer is measured by weighing method. First, the weight of the polymer layer with volume V is weighed and recorded as m 0The weighed polymer layer was completely immersed in the n-hexadecane reagent for 2 h, and then the polymer layer was taken out and the residual reagent on its surface was wiped off with dust-free paper. The weight of the polymer layer was recorded as m 1 , the porosity of the polymer layer is calculated using the following formula:

[0099] In the above formula is the porosity, unit is %; is the density of n-hexadecane, in g / cm 3 .

[0100] Electrode liquid retention rate test: Take 20 layers of composite isolation films with conductive structures (hereinafter referred to as pole pieces) prepared according to the method, with a size of 100mm*100mm, stack the pole pieces together and clamp them with two aluminum clamps, and weigh them and record the weight as m 0 Then, the fixture is immersed in the electrolyte for 2 hours and then taken out. When the electrolyte is dripping, the residual electrolyte on the surface of the aluminum fixture is wiped off with dust-free paper. The weight is recorded as m 1 ; Then use an automatic press to apply 3000N pressure on both sides of the fixture (simulating the state of the battery in the battery pack), keep it for 3 minutes, and then weigh the weight and record it as m 2 The liquid retention rate of the electrode is calculated according to the following formula:

[0101] In the above formula is the liquid retention rate, in %.

[0102] The test results of the above embodiments and comparative examples are shown in Table 1 below: Table 1

[0103] From the above results, it can be seen that the pore-forming design of the organic polymer layer and the conductive layer has a significant effect on improving the liquid retention rate of the electrode. From the results of the embodiment, when the pore size and porosity of the first sublayer remain unchanged, when the pore size of the second sublayer increases from 3μm to 10μm, the liquid retention rate of the electrode is significantly improved; but when the pore size of the second sublayer increases from 10μm to 18μm, the liquid retention rate of the electrode remains basically unchanged. When the pore size and porosity of the first polymer remain unchanged, as the pore size and porosity of the second polymer layer increase, the liquid retention rate of the electrode increases, but the increase is not large.

[0104] Lithium-ion secondary battery cycle performance test: At 25°C, the battery was charged to 4.4V at a constant current of 1C, then charged at a constant voltage of 4.4V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 1C. The first cycle discharge capacity (C d1 The charge and discharge are repeated in this way until the 500th cycle, and the discharge capacity after 500 cycles is recorded as C dn .

[0105] Capacity retention rate (%) = discharge specific capacity after 500 cycles (C dn ) / first week discharge capacity (C d1 ).

[0106] Lithium deposition test on corners of lithium-ion secondary batteries after cycling The lithium-ion secondary battery after 500 cycles was charged to 4.4V at a constant current of 1C, and then charged at a constant voltage of 4.4V until the current dropped to 0.05C. It was then disassembled to determine the lithium deposition at the corners of the anode electrode interface. The lithium deposition at the corners of the concave and convex surfaces of the anode were graded according to the judgment levels shown in Table 2 below.

[0107] The judgment level of lithium deposition at the interface of the anode corner of the lithium-ion secondary battery after 500 cycles is shown in Table 2 below, where JR is the number of electrode assemblies in the secondary battery: Table 2

[0108] The cycle capacity retention rate and corner lithium deposition level of the above embodiments and comparative examples are shown in Table 3 below: Table 3

[0109] From the perspective of cycle performance and lithium deposition level at the anode corner, as the pore size and porosity of the first and second polymer layers increase, the electrode liquid retention rate is improved, so the electrolyte infiltration at the battery corner is improved, which in turn improves the lithium deposition at the corner, and ultimately improves the battery cycle performance. However, when the pore size of the second sublayer is 10μm and 18μm; the corresponding pore size of the first sublayer is 500nm and 1μm, the lithium deposition level at the battery corner is level one.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A secondary battery, characterized in that: include: A composite separator, a positive electrode active material layer located on one side of the composite separator, and a negative electrode active material layer located on the other side of the composite separator, The composite isolation film includes a polymer layer and a conductive structure located on both sides of the polymer layer, wherein the conductive structure has a through hole. The porosity of the composite isolation membrane is 15-30%, and the average pore size of the polymer layer is 100nm-20μm.

2. The secondary battery according to claim 1, characterized in that: The polymer layer includes a first sublayer and a second sublayer, wherein the first sublayer is located on a side close to the positive electrode active material layer, and the second sublayer is located on a side close to the negative electrode active material layer. The first sublayer has a plurality of first pores, the second sublayer has a plurality of second pores, the average pore diameter of the first pores is 10 nm-20 μm, and the average pore diameter of the second pores is 500 nm-20 μm.

3. The secondary battery according to claim 2, characterized in that: The average pore size of the first pores is the same as the average pore size of the second pores.

4. The secondary battery according to claim 2, characterized in that: The average pore diameter of the first pores is different from the average pore diameter of the second pores. The average pore diameter of the first pores is 10 nm-1 μm, and the average pore diameter of the second pores is 1 μm-20 μm.

5. The secondary battery according to claim 4, characterized in that: The porosity of the first sublayer is 10-20%, and the porosity of the second sublayer is 20-30%.

6. The secondary battery according to any one of claims 1 to 5, characterized in that: The material of the polymer layer includes at least one of epoxy resin, terephthalate, polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide and polyamide.

7. The secondary battery according to claim 1, characterized in that: The conductive structure includes a first conductive layer and a second conductive layer, the first conductive layer is in contact with the positive electrode active material, and the second conductive layer is in contact with the negative electrode active material. The first conductive layer has a first through hole, and the second conductive layer has a second through hole. The average pore diameters of the first through-holes and the second through-holes are independently 500 nm to 20 μm.

8. The secondary battery according to claim 7, characterized in that: The average pore diameters of the first through holes and the second through holes are independently 1 μm to 10 μm.

9. The secondary battery according to claim 7, characterized in that: The porosity of the first conductive layer and the second conductive layer are independently 10-30%.

10. The secondary battery according to claim 1, characterized in that: The secondary battery is a wound battery, The wound battery comprises a plurality of the composite isolation membranes, which are separated by insulating membranes. The composite isolation membrane comprises a plurality of planar portions and a plurality of bending portions, and adjacent planar portions are connected via the bending portions.

11. A composite isolation membrane, characterized in that: include: A polymer layer, and conductive structures located on both sides of the polymer layer, wherein the conductive structures have through holes, The porosity of the composite isolation membrane is 15-30%, and the average pore size of the polymer layer is 100nm-20μm.

12. The composite isolation membrane according to claim 11, characterized in that: The polymer layer includes a first sublayer and a second sublayer, the first sublayer has a plurality of first holes, and the second sublayer has a plurality of second holes, The average pore size of the first pores is 10 nm-1 μm, and the average pore size of the second pores is 1 μm-20 μm.

13. The composite isolation membrane according to claim 12, characterized in that: The conductive structure includes a first conductive layer and a second conductive layer, the first conductive layer is located on one side of the first sub-layer, and the second conductive layer is located on one side of the second sub-layer. The first conductive layer has a first through hole, and the second conductive layer has a second through hole. The average pore diameters of the first through-hole and the second through-hole are independently 1-10 μm. The porosity of the first conductive layer and the second conductive layer are independently 10-30%.

14. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 10.

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