Composite current collector, electrode plate, secondary battery and electric device

Abstract

The invention relates to the technical field of secondary batteries, and discloses a composite current collector, an electrode plate, a secondary battery and an electric device, and the composite current collector comprises a composite base membrane and metal conductive layers arranged on the surfaces of the two sides of the composite base membrane; wherein the composite base film comprises thermoplastic resin, thermosetting resin and inorganic particles, the adding proportion of the inorganic particles is a, and a is larger than or equal to 1% and smaller than or equal to 10% according to the total mass of the composite base film; the addition proportion of the thermosetting resin is b, and 8% < = b < = 35%; and 0.1 < = a / b < = 0.65. According to the invention, by simultaneously adding a specific amount of the thermosetting resin and the inorganic particles into the composite base film and limiting the proportional relation of the addition amounts of the thermosetting resin and the inorganic particles, the tensile strength and the ductility of the composite current collector are reduced, and the problem that the composite current collector is easy to deform in the processing process of an application end is solved. And meanwhile, the thermosetting resin is added, so that the thermal conductivity of the composite current collector can be further enhanced.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to a composite current collector, electrode plates, secondary battery, and electrical device. Background Technology

[0002] With the implementation of policies restricting the purchase and use of gasoline-powered vehicles, the development of the market for replacing gasoline with electricity, the driving force of environmental protection requirements, and the implementation of the "carbon peaking and carbon neutrality" policy, the new energy industry has developed rapidly, and the sales of new energy vehicles have achieved explosive growth. At the same time, higher demands have been placed on the energy density, cycle life, safety, and low cost of lithium-ion batteries.

[0003] Compared to traditional copper-aluminum foil as current collectors, composite current collectors (with an inner polymer layer (such as PET, PP, or PI) and two conductive metal layers (such as Al or Cu) on both sides) are more likely to disconnect during a battery short circuit due to their structural characteristics. This isolates the active material from the current collector, preventing further thermal runaway in lithium / sodium-ion batteries. Furthermore, the internal polymer layer generates infinite resistance, effectively reducing the likelihood of thermal runaway. In addition, composite current collectors significantly reduce weight by using an insulating support layer to replace some of the metal, thereby increasing battery energy density and reducing raw material costs. Therefore, the development of composite current collectors has received widespread attention in recent years.

[0004] Although composite current collectors can significantly improve battery safety, reduce costs, and increase energy density, there are still many technical challenges in large-scale production and application. The elongation and tensile strength of composite current collectors are significantly greater than those of metal current collectors, which cannot meet the requirements of secondary batteries. Summary of the Invention

[0005] This application provides a composite current collector, electrode sheet, secondary battery, and power supply device to solve problems such as excessively high tensile strength and large elongation of the composite current collector.

[0006] In a first aspect, this application provides a composite current collector, comprising: a composite base film and a metal conductive layer disposed on both sides of the composite base film;

[0007] The composite base film comprises: thermoplastic resin, thermosetting resin, and inorganic particles.

[0008] Based on the total mass of the composite base film, the addition ratio of the inorganic particles is a, where 1% ≤ a ≤ 10%; the addition ratio of the thermosetting resin is b, where 8% ≤ b ≤ 35%; and 0.1 ≤ a / b ≤ 0.65.

[0009] In some embodiments, the proportion of inorganic particles added is 3% ≤ a ≤ 8%;

[0010] And / or, the addition ratio of the thermosetting resin is 10% ≤ b ≤ 30%;

[0011] And / or, the composite base film further includes a conductive agent, wherein the addition ratio of the conductive agent is 0.2% to 2%.

[0012] In some embodiments, the metal conductive layer further includes doping elements, and the proportion of the doping elements added is c based on the total mass of the metal conductive layer, where 0.02% ≤ c ≤ 2.5%, and 0.02(a+b) ≤ c ≤ 0.05(a+b).

[0013] In some embodiments, the doping element includes at least one selected from Fe, Mg, Si, Mn, Ni, and Zn.

[0014] In some embodiments, the thermoplastic resin includes at least one of polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), and polyurethane;

[0015] And / or, the thermosetting resin includes at least one of phenolic resin, epoxy resin, and furan resin;

[0016] And / or, the inorganic particles include at least one of inorganic nanoparticles and inorganic micron particles;

[0017] And / or, the conductive agent includes at least one of conductive carbon black, carbon nanofibers, and graphene.

[0018] In some embodiments, the inorganic particles include at least one of silicon dioxide, titanium dioxide, aluminum oxide, and montmorillonite.

[0019] In some embodiments, the thickness of the composite base film is 1 μm to 10 μm;

[0020] And / or, the thickness of the metal conductive layer is 1 μm to 10 μm.

[0021] In some embodiments, the base element of the metal conductive layer is Al or Cu.

[0022] Secondly, this application provides an electrode sheet, comprising:

[0023] The composite current collector provided in the first aspect above, and

[0024] An active material layer disposed on at least one side of the composite current collector.

[0025] Thirdly, this application provides a secondary battery, including the electrode plates provided in the second aspect above.

[0026] Fourthly, this application provides an electrical device including the secondary battery provided in the third aspect above.

[0027] The technical solution of this application has the following advantages:

[0028] The composite current collector provided in this application includes: a composite base film and metal conductive layers disposed on both surfaces of the composite base film; wherein, the composite base film comprises: thermoplastic resin, thermosetting resin, and inorganic particles, and the addition ratio of the inorganic particles is a, 1% ≤ a ≤ 10% based on the total mass of the composite base film; the addition ratio of the thermosetting resin is b, 8% ≤ b ≤ 35%; and 0.1 ≤ a / b ≤ 0.65. This application reduces the tensile strength and elongation of the composite current collector by simultaneously adding specific amounts of thermosetting resin and inorganic particles to the composite base film and limiting the ratio of their addition, thus solving the problem of easy deformation of the composite current collector during application processing. Simultaneously, the addition of thermosetting resin further enhances the thermal conductivity of the composite current collector.

[0029] The composite current collector provided in this application has an inorganic particle addition ratio of 3% ≤ a ≤ 8%; and / or, a thermosetting resin addition ratio of 10% ≤ b ≤ 30%. By limiting the addition ratio of inorganic particles and thermosetting resin, this application can further improve the cycle performance of the composite current collector after it is used in secondary batteries.

[0030] The composite current collector provided in this application further includes dopant elements in the metal conductive layer. The addition ratio of the dopant elements, based on the total mass of the metal conductive layer, is c, where 0.02% ≤ c ≤ 2.5%, and 0.02(a+b) ≤ c ≤ 0.05(a+b). By adding a specific amount of dopant elements to the metal conductive layer and controlling the ratio between the dopant elements and the amounts of thermosetting resin and inorganic particles, this application enables the composite base film and the metal conductive layer to achieve almost the same elongation, resulting in optimal interfacial bonding between the two.

[0031] The secondary battery provided in this application includes the composite current collector provided in this application. Because the composite current collector has low tensile strength and elongation, it can avoid problems such as peeling and powdering of the active material on the surface of the composite current collector, thereby improving the overall cycle life of the secondary battery while maintaining safety.

[0032] In this application, by adding thermosetting resin and inorganic particles to the base thermoplastic resin, the rigidity of the base resin is improved, which effectively avoids the problem of soft cell caused by the material expansion stress acting on the electrode during battery cycling, thereby avoiding cycle degradation caused by poor contact at the cell electrode interface. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the composite current collector in Embodiment 1 of this application;

[0035] Figure label:

[0036] 1. Composite base film; 2. Metal conductive layer; 3. Inorganic particles; 4. Thermosetting resin. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0042] In the description of the embodiments of this application, the term "at least one" refers to two or more (including two).

[0043] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0044] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0045] While composite current collectors can significantly improve battery safety, reduce costs, and increase energy density, there are still many technical challenges in large-scale production and application. These challenges mainly stem from the high elongation and low strength of the internal polymer layer. During processing, the substrate often deforms under traction, resulting in a decrease in width and an increase in length. However, the elongation of the surface active material is inconsistent with that of the substrate, leading to problems such as the peeling off of the surface active material and powder shedding.

[0046] To address the problems existing in the prior art, according to a first aspect of this application, a composite current collector is provided, comprising: a composite base film and a metal conductive layer disposed on both sides of the composite base film;

[0047] The composite base film comprises: thermoplastic resin, thermosetting resin, and inorganic particles.

[0048] Based on the total mass of the composite base film, the addition ratio of the inorganic particles is a, where 1% ≤ a ≤ 10%; the addition ratio of the thermosetting resin is b, where 8% ≤ b ≤ 35%; and 0.1 ≤ a / b ≤ 0.65. For example, the addition ratio of the inorganic particles is 1%, 2%, 2.5%, 3%, 4%, 5%, 5.8%, 6.2%, 7%, 8%, 9%, 10%, or within any range of the above values; the addition ratio of the thermosetting resin is 8%, 9%, 12%, 15%, 18%, 20%, 24%, 26%, 30%, 33%, 35%, or within any range of the above values; a / b can be 0.1, 0.2, 0.25, 0.3, 0.38, 0.4, 0.42, 0.5, 0.55, 0.6, 0.65, or within any range of the above values.

[0049] This application reduces the strength and elongation of composite current collectors by simultaneously adding specific amounts of thermosetting resin and inorganic particles to the composite base film and limiting the ratio of their addition, thus solving the problem of easy deformation of composite current collectors during application processing. Simultaneously, the addition of thermosetting resin further enhances the thermal conductivity of the composite current collector. If the proportion of inorganic particles is higher than 10%, the composite base film will develop fracture points due to the excessive particle ratio; if the proportion of inorganic particles is lower than 1%, the low particle distribution will fail to achieve the desired modification effect. If the proportion of thermosetting resin is higher than 35%, the composite plastic will become brittle due to excessive plasticity; if the proportion of thermosetting resin is lower than 10%, the insufficient thermosetting properties will result in poor toughening effect. If the ratio of inorganic particles to thermosetting resin (a / b) is higher than 0.65, the particles will be too concentrated, leading to excessive brittleness; if a / b is lower than 0.1, the particles will not be uniformly distributed within the composite base film, resulting in uneven toughness distribution and poor consistency of the composite current collector.

[0050] In some embodiments, the proportion of inorganic particles added is 3% ≤ a ≤ 8%;

[0051] And / or, the addition ratio of the thermosetting resin is 10% ≤ b ≤ 30%;

[0052] And / or, the composite base film further includes a conductive agent, wherein the addition ratio of the conductive agent is 0.2% to 2%.

[0053] This application, by limiting the addition ratio of inorganic particles and thermosetting resin, can further improve the cycle performance of composite current collectors used in secondary batteries.

[0054] In some embodiments, the metal conductive layer further includes doping elements, and the proportion of the doping elements added is c based on the total mass of the metal conductive layer, where 0.02% ≤ c ≤ 2.5%, and 0.02(a+b) ≤ c ≤ 0.05(a+b).

[0055] In some embodiments, the conductive agent includes, but is not limited to, at least one of conductive carbon black, carbon nanofibers, graphene, etc.

[0056] This application achieves near-identical elongation of the composite base film and the metal conductive layer by adding specific amounts of dopant elements to the metal conductive layer and controlling the ratio between the dopant elements and the thermosetting resin and inorganic particles, resulting in optimal interfacial bonding. If the dopant element addition ratio exceeds 2.5%, severe metal lattice deformation leads to excessive changes in metallic properties; if the dopant element addition ratio is below 0.02%, insufficient dopant concentration results in no significant change in the alloy's mechanical properties; if c is below 0.02(a+b), the low tensile strength of the alloy leads to delamination between the metal conductive layer and the composite base film; if c is above 0.05(a+b), the low tensile strength of the composite base film also leads to delamination between the metal conductive layer and the composite base film.

[0057] In some embodiments, the doping element includes at least one selected from Fe, Mg, Si, Mn, Ni, and Zn.

[0058] In some embodiments, the thermoplastic resin includes, but is not limited to, at least one of polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), and polyurethane;

[0059] And / or, the thermosetting resin includes, but is not limited to, at least one of phenolic resin, epoxy resin, and furan resin;

[0060] And / or, the inorganic particles include at least one of inorganic nanoparticles and inorganic microparticles.

[0061] In some embodiments, the inorganic particles include at least one of silicon dioxide, titanium dioxide, aluminum oxide, and montmorillonite; in this application, the D of the inorganic nanoparticles... n 50 Particle size is between 1 nm and 100 nm; Inorganic micron particles D n 50. The particle size is between 1μm and 100μm.

[0062] In some embodiments, the thickness of the composite base film is 1 μm to 10 μm; for example, the thickness of the composite base film is 1 μm, 2 μm, 3 μm, 5 μm, 5.5 μm, 6.4 μm, 7 μm, 8 μm, 9 μm, 10 μm, or within any of the above values.

[0063] And / or, the thickness of the metal conductive layer is 1 μm to 10 μm. For example, the thickness of the metal conductive layer is 1 μm, 2 μm, 3 μm, 5 μm, 5.5 μm, 6.4 μm, 7 μm, 8 μm, 9 μm, 10 μm, or within any range of the above values.

[0064] In some embodiments, the base element of the metal conductive layer is Al or Cu.

[0065] In this application, the preparation method of the composite current collector is conventional in the art, and is hereby illustrated. The preparation method of the composite current collector includes the following steps:

[0066] a. After drying and purifying the thermoplastic resin and thermosetting resin, mix them with inorganic particles and conductive agent (if no conductive agent is present, do not add the conductive agent in this step) to form a uniform mixed system of raw materials.

[0067] b. Heat the raw materials mixed in step a to above 250°C to form a molten state, and then extrude them through a twin-screw extruder to form an initial composite base film with a thickness of <5mm.

[0068] c. The extruded composite base film is stretched simultaneously in the transverse and longitudinal directions. By setting a temperature gradient, such as three temperature ranges of 200℃, 150℃, and 100℃, the temperature of the equipment during the stretching process is adjusted. The film thickness is controlled between 1μm and 10μm by the stretching speed of the stretching machine, which is 5 to 90 m / min.

[0069] d. Cool the composite base film via a conveyor belt until it reaches room temperature below 30°C.

[0070] e. Place the above composite base film in a vacuum chamber, mix Al or Cu with the doped metal, heat to 700°C and melt (Cu is heated to 1100°C), cool the molten metal liquid and use it as a cathode target, and then spray the mixed metal onto the composite base film by magnetron sputtering to form a composite current collector.

[0071] Secondly, this application provides an electrode sheet, comprising:

[0072] The composite current collector provided in the first aspect above, and

[0073] An active material layer disposed on at least one side of the composite current collector.

[0074] In some embodiments, the electrode sheet is a positive electrode sheet or a negative electrode sheet.

[0075] Thirdly, this application provides a secondary battery, including the electrode plates provided in the second aspect above.

[0076] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0077] Taking a lithium-ion battery as an example, the secondary battery of the present application will be described below.

[0078] [Positive electrode plate]

[0079] The positive electrode plate includes the composite current collector (positive current collector) provided in the above first aspect and a positive electrode active material layer provided on at least one surface of the positive current collector, and the positive electrode active material layer includes a positive electrode active material.

[0080] As an example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive current collector.

[0081] The positive electrode active material layer includes a positive electrode active material. The positive electrode active material can be selected from materials that can absorb and release lithium. The specific type of the positive electrode active material is not specifically limited and can be selected according to requirements. As an example, the positive electrode active material may include at least one of the following materials: lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), lithium iron pyrophosphate (Li2FeP2O7), lithium cobalt oxide (LiCoO2), spinel-type lithium manganese oxide (LiMn2O4), spinel-type lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), layered lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeO2), lithium manganate (LiMgO2), lithium calcium oxide (LiCaO2), lithium copper oxide (LiCuO2), lithium zinc oxide (LiZnO2), lithium molybdate (LiMoO2), lithium tantalate (LiTaO2), lithium tungstate (LiWO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2O2, LiNi 0.8 Co 0.1 Mn 0.1 At least one of the following: O2, lithium-rich materials (e.g., lithium-rich nickel-cobalt-manganese oxide), manganese oxide (MnO2), vanadium oxide, sulfur oxide, silicate oxide, and their respective modified compounds. These materials may be used alone or in combination of two or more.

[0082] The modified compounds for the above-mentioned positive electrode active materials can be modified by doping, surface coating, or simultaneous doping and coating.

[0083] In some embodiments, the positive electrode active material layer may further include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0084] In some embodiments, the positive electrode active material layer may further include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0085] In some embodiments, 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 (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0086] [Negative electrode plate]

[0087] The negative electrode sheet includes the aforementioned composite current collector (negative electrode current collector) and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0088] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0089] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode 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, and lithium titanate, etc. 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. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0090] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0091] In some embodiments, the negative electrode active material layer may optionally include 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.

[0092] In some embodiments, the negative electrode active material layer may also include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0093] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0094] [Electrolytes]

[0095] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0096] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0097] In some embodiments, the electrolyte salt may be selected from 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0098] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0099] In some embodiments, the electrolyte may also include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0100] In some embodiments, the electrolyte is a solid electrolyte, which can be various lithium-ion solid electrolytes commonly used in the art. Examples of lithium-ion solid electrolytes are provided below, including but not limited to:

[0101] LISICON type: such as γ-Li3PO4, etc.;

[0102] NASICON type: for example, Li (1+x1) Q x1 M (2-x1) (PO4)3, 0≤x1<1, Q includes at least one of Al, Cr, Ba, Fe, Sc, In, Lu, Y, and La;

[0103] Garnet type: for example, Li (7-x2) La3Zr (2-x2) M x2 O 12 Etc., 0≤x2<1, M includes at least one of Sb, Nb, Ta, Te, and W;

[0104] LIPON type: for example, Li x3 PO y1 N z1 ;0 <x3≤1,0<y1≤1,0<z1≤1;

[0105] Perovskite type: for example, Li x4 Q (2 / 3-x4)such as MO3, 0.04 < x4 < 0.17, Q includes at least one of La, Sr, Ba, Nd, and M includes at least one of Al, Ti, Ge;

[0106] Anti-Perovskite type: such as Li3OCl, etc.;

[0107] Thio-LiSICON type: such as Li (3+x5) My2A (1-y2) Q (4-z2) T z2 , where -1 < x5 < 2, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, and T includes at least one of F, Cl, Br, I;

[0108] Sulfide solid electrolytes include: Thiophosphate type: such as Li3PS4, etc., Argyrodite type: Li6PS5Cl, Halide type: Li3InCl6, Hydride type: 0.7Li(CB9H 10 ) - 0.3Li(CB 11 H 12 ), etc.; such as Li (10+x6) M (1+y3) A (2-y3) Q (12-z3) H z3 type: where -2 < x6 < 2, 0 ≤ y3 ≤ 2, 0 ≤ z3 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo; A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, and H includes at least one of F, Cl, Br, I: (100 - x7)Li2S·x7M·y4Q type: where 20 ≤ x7 ≤ 30, 0 ≤ y4 ≤ 50, M includes at least one of B2S3, Al2S3, In2S3, SiS2, GeS2, SnS2, P2S5, As2S3, Sb2S5, Bi2S3, WS2, MoS2, and Q includes at least one of B2O3, Al2O3, In2O3, SiO2, GeO2, SnO2, P2O5, Sb2O5, Bi2O3, WO2, WO3, MoO2, MoO3, Fe2O3, ZnO, MgO, CuO, CaO, LiN, Li2O, LiF, LiCl, LiBr, LiI; Argyrodite type: Li (6+x8) M y5 A (1-y5) Q (5-z5) T(1+z5) , where -1 ≤ x8 ≤ 1, 0 ≤ y5 ≤ 1, -1 < z5 ≤ 1, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, T includes at least one of F, Cl, Br, I; Halide type: Li3MJ or Li2Sc 2 / 3 J, M includes at least one of Y, Er, In, Sc, Ga, and J includes at least one of F, Cl, Br, I.

[0109] When the above sulfide solid electrolyte is a sulfide-based solid electrolyte, it includes, but is not limited to: argyrodite electrolyte; binary sulfide-based solid systems such as Li2S-P2S5, Li2S-SiS2, Li2S-GeS, and Li2S-B2S3, and Li2S-Me-P2S5 ternary systems, where Me is selected from Si, Ge, Sn, or Al, etc.

[0110] Specifically, the above sulfide electrolyte is selected from at least one of Li2S-P2S5, Li2S-SiS2, Li2S-GeS, Li2S-B2S3, and Li2S-Me-P2S5.

[0111] [Separator film]

[0112] In some embodiments, the secondary battery further includes a separator film. The present application does not particularly limit the type of the separator film, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0114] Taking a sodium-ion battery as an example, the secondary battery of the present application will be described below.

[0115] [Positive electrode sheet]

[0116] The positive electrode sheet includes the above composite current collector (positive current collector) and a positive electrode active material layer provided on at least one surface of the positive current collector, and the positive electrode active material layer includes a positive electrode active material.

[0117] As an example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on either or both of the two opposite surfaces of the positive current collector.

[0118] In this application, the positive electrode active material is capable of reversibly inserting and de-inserting Na. + Compounds. For example, positive electrode active materials include transition metal oxides, polyanionic compounds, Prussian blue analogs, etc.

[0119] In some implementations, the positive electrode active material is a transition metal oxide. As an example, Na can be cited. x MO2 or Na y M₂O₄ (where M is a transition metal, 0≤x≤1, 0≤y≤2) represents sodium-containing complex oxides, spinel-like oxides, layered metal chalcogenides, olivine structures, etc. Examples include sodium cobalt oxides such as NaCoO₂, sodium manganese oxides such as NaMn₂O₄, sodium nickel oxides such as NaNiO₂, and Na… 4 / 3 Ti 5 / 3 Sodium titanium oxides such as O4, sodium manganese nickel composite oxides, sodium manganese nickel cobalt composite oxides; materials with olivine-type crystal structures such as NaMPO4 (M=Fe, Mn, Ni), etc.

[0120] In some embodiments, the positive electrode active material is a layered or spinel-like sodium-containing composite oxide, such as NaCoO2, NaMn2O4, NaNiO2, or NaNi 1 / 2 Mn 1 / 2 Sodium-manganese-nickel composite oxides, represented by O2, etc., with NaNi 1 / 3Mn 1 / 3 Co 1 / 3 O2, NaNi 0.6 Mn 0.2 Co 0.2 Sodium-manganese-nickel-cobalt composite oxides, represented by O2, or NaNi 1-x-y-z Co x Al y Mg z Sodium-containing composite oxides such as O2 (where 0≤x≤1, 0≤y≤0.1, 0≤z≤0.1, 0≤1-xyz≤1). Furthermore, sodium-containing composite oxides in which a portion of the constituent elements of the aforementioned sodium-containing composite oxides are replaced by additive elements such as Ge, Ti, Zr, Mg, Al, Mo, and Sn are also included within the scope of this application.

[0121] In some embodiments, the positive electrode active material is a polyanionic compound. As an example, the polyanionic compound may have sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4).n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, or Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0122] In some embodiments, the positive electrode active material is a Prussian blue analogue. As an example, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0123] In some embodiments, the positive electrode active material layer may further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0124] In some embodiments, the binder may optionally account for 0.1% to 3.5% of the total weight of the positive electrode active material layer, and optionally 0.5% to 2.5%.

[0125] In some embodiments, the positive electrode active material layer may further include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the conductive agent accounts for 0.05% to 5% of the total weight of the positive electrode active material layer, optionally 0.5% to 3%.

[0127] In some embodiments, 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 (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0128] [Negative electrode plate]

[0129] In a sodium-ion battery, the negative electrode typically includes a negative current collector (the aforementioned composite current collector) and a negative active material layer disposed on the negative current collector, wherein the negative active material layer includes a negative active material.

[0130] The negative electrode may also consist only of the negative current collector (the aforementioned composite current collector), i.e., without the negative electrode active material. The negative electrode may also include a metal phase pre-deposited on the negative current collector.

[0131] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0132] This application does not limit the specific type of the negative electrode active material. Any active material known in the art that can be used as a negative electrode in sodium-ion batteries can be used, and those skilled in the art can select according to actual needs. As an example, the negative electrode active material may include, but is not limited to, one or more of sodium metal, carbon materials, alloy materials, transition metal oxides and / or sulfides, phosphorus-based materials, and titanate materials. Specifically, the carbon material may include one or more of hard carbon, soft carbon, amorphous carbon, and nanostructured carbon materials; the alloy material may include alloys formed from one or more of Si, Ge, Sn, Pb, and Sb; the general formula of the transition metal oxides and sulfides is M. x N yM includes one or more of Fe, Co, Ni, Mn, Sn, Mo, Sb, and V, and N includes O or S; the phosphorus-based material may include one or more of red phosphorus, white phosphorus, and black phosphorus; the titanate material may include Na2Ti3O7 and Na2Ti6O7. 13 Na4Ti5O 12 Li4Ti5O 12 One or more of NaTi2(PO4)3. These materials are all commercially available.

[0133] The negative electrode active material layer typically also includes a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the conductive agent to the negative electrode current collector. This application does not specifically limit the types of conductive agents and binders, which can be selected according to actual needs.

[0134] As an example, conductive agents may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] As an example, the adhesive may include one or more of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0136] The negative electrode active material layer may also include a thickener, such as carboxymethyl cellulose (CMC). However, this application is not limited to this; other materials that can be used as thickeners for the negative electrode sheet of sodium-ion batteries may also be used.

[0137] [Isolation membrane]

[0138] This application does not impose any particular restrictions on the type of separator membrane. Any well-known porous structure separator membrane with electrochemical and mechanical stability can be selected according to actual needs. For example, it can be a single-layer or multi-layer film containing one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0139] [Electrolytes]

[0140] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0141] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0142] As an example, the electrolyte salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0143] As an example, the solvent may include ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (... MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran, methyltetrahydrofuran, 1,3-dioxopentane, 1,3-dioxane, 1,4-dioxane, tetrahydropyran, methyl ethyl sulfone (EMS), and diethyl sulfone (ESE) are one or more of these.

[0144] In some embodiments, the electrolyte also includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0145] In some embodiments, the electrolyte is a solid electrolyte, which can be various sodium-ion solid electrolytes commonly used in the art. Examples of sodium-ion solid electrolytes are provided below, including but not limited to:

[0146] NASICON type: Na (1+x9+2y5) Zr (2-y5) M y5 P (3-x9) Si x9 O 12 0≤x9≤3, 0≤y5≤1, M includes at least one of Zn, Mg, and Ca; Na-β-Alumina type: Na2O·2Al2O3 or Na2O·3Al2O3, etc.; Na (3+x10) M y6 A (1-y6) Q (4-z6) T z6Type, where -1 < x10 < 2, 0 ≤ y6 ≤ 1, 0 ≤ z6 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo; A includes at least one of P, As, Sb, Bi; Q includes at least one of S, Se; T includes at least one of F, Cl, Br, I; Na (11+x11) M (2-y7) A (1+y7) Q (12-z7) T z7 Type: where -1 < x11 < 1, 0 ≤ y7 ≤ 2, 0 ≤ z7 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo; A includes P, As, Sb, Bi; Q is at least one of S, Se; T includes at least one of F, Cl, Br, I; inverse perovskite type Na3OX, X includes at least one of Cl, Br, I, BH4.

[0147] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be made into a secondary battery by a winding process or a stacking process.

[0148] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0149] In some embodiments, the outer package of the secondary battery can be a hard shell, for example, a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, for example, a pouch soft package. The material of the soft package can be plastic, and as plastics, polypropylene, polybutylene terephthalate and polybutylene succinate can be listed, etc.

[0150] This application does not particularly limit the shape of the secondary battery, and it can be cylindrical, square or any other shape.

[0151] In some embodiments, the secondary batteries can be assembled into a battery module. The number of secondary batteries included in the battery module can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0152] In some embodiments, the above battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0153] Fourthly, this application provides an electrical device, including the secondary battery provided in the third aspect above.

[0154] In some embodiments, the aforementioned electrical device may also include a battery module or battery pack assembled from the aforementioned secondary batteries. The secondary batteries, battery modules, or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0155] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements. An example electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0156] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0157] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0158] The following is information on the source of some of the raw materials used in the embodiments and comparative examples of this application:

[0159] Table 1

[0160]

[0161] Example 1

[0162] This embodiment provides a composite current collector, the structural schematic diagram of which is shown below. Figure 1 As shown, it includes: a composite base film 1 and metal conductive layers 2 disposed on both sides of the composite base film 1; the composite base film 1 includes: thermoplastic resin, thermosetting resin 4 and inorganic particles 3; the specific preparation method is as follows:

[0163] a. After drying and purifying thermoplastic resin PET and phenolic resin PF, they are mixed evenly with silica particles and conductive agent SP to form a homogeneous mixture. The total mass of the mixture is calculated as follows: silica particles (D...) n The addition ratio of 50 (25nm, the same below) is 7%, the addition ratio of phenolic resin is 35%, and the addition amount of conductive agent SP is 0.5%.

[0164] b. Heat the raw materials mixed in step a to above 250°C to form a molten state, and then extrude them through a twin-screw extruder to form an initial composite base film with a thickness of <5mm.

[0165] c. The extruded composite base film is stretched simultaneously in the transverse and longitudinal directions. By setting a temperature gradient, with three temperature ranges of 200℃, 150℃, and 100℃, the temperature of the equipment during the stretching process is adjusted. The film thickness is controlled to be 10μm by the stretching speed of the stretching machine at 30m / min.

[0166] d. Cool the composite base film via a conveyor belt until it reaches room temperature below 30°C.

[0167] e. Place the above composite base film in a vacuum chamber, mix Cu with doped metal Zn and heat to 1100°C to melt. Cool the molten metal liquid and use it as a cathode target. Spray the mixed metal onto the composite base film by magnetron sputtering. Deposit a 10μm thick Cu conductive layer containing 2.0% doped element Zn on both sides of the base film to form a composite current collector.

[0168] Example 2

[0169] This embodiment provides a composite current collector. Compared with Embodiment 1, the only difference is that in step a, the thermoplastic resin is PP, the addition ratio of silica particles is 4%, and the addition ratio of phenolic resin is 10%; in step c, the thickness of the film is controlled to be 1μm, and the conductive layer is a Cu conductive layer containing 0.4% dopant element Mg.

[0170] Example 3

[0171] This embodiment provides a composite current collector, which differs from Embodiment 1 only in that, in step a, the thermoplastic resin is PE and the inorganic particles are titanium dioxide (D). n 50 is 25nm (the same below), the addition ratio is 10%, the thermosetting resin is furan resin, the addition ratio is 20%; in step c, the thickness of the film is controlled to be 4μm, and the conductive layer is a Cu conductive layer containing 0.9% dopant element Zn.

[0172] Example 4

[0173] This embodiment provides a composite current collector. Compared with embodiment 3, the only difference is that in step a, the thermoplastic resin is PET and the conductive layer is a Cu conductive layer containing 1.0% dopant element Mg.

[0174] Example 5

[0175] This embodiment provides a composite current collector. Compared with Embodiment 2, the only difference is that in step a, the addition ratio of silicon dioxide particles is 5% and the addition ratio of phenolic resin is 8%; in step c, the thickness of the film is controlled to be 5μm and the conductive layer is a Cu conductive layer containing 0.3% dopant element Zn.

[0176] Example 6

[0177] This embodiment provides a composite current collector. The only difference from Embodiment 1 is that, in step a, the thermosetting resin is epoxy resin.

[0178] Example 7

[0179] This embodiment provides a composite current collector, which differs from Embodiment 1 only in that, in step a, the inorganic particles are montmorillonite (particle size D). n 50 is 3000nm).

[0180] Example 8

[0181] This embodiment provides a composite current collector, which differs from Embodiment 2 only in that the proportion of silica particles added is 2%.

[0182] Example 9

[0183] This embodiment provides a composite current collector, which differs from Embodiment 5 only in that the addition ratio of phenolic resin is 12%.

[0184] Example 10

[0185] This embodiment provides a composite current collector, which differs from Embodiment 1 only in that the metal conductive layer does not include doping elements.

[0186] Example 11

[0187] This embodiment provides a composite current collector, which differs from Embodiment 2 only in that the metal conductive layer does not include doping elements.

[0188] Example 12

[0189] This embodiment provides a composite current collector, which differs from Embodiment 5 only in that the addition ratio of phenolic resin is 10%.

[0190] Example 13

[0191] This embodiment provides a composite current collector, which differs from Embodiment 5 only in that the addition ratio of phenolic resin is 30%.

[0192] Example 14

[0193] This embodiment provides a composite current collector, which differs from Embodiment 5 only in that the proportion of silica particles added is 3%.

[0194] Example 15

[0195] This embodiment provides a composite current collector, which differs from Embodiment 3 only in that the proportion of titanium dioxide particles added is 8%.

[0196] Comparative Example 1

[0197] This comparative example provides a composite current collector, which differs from Example 1 only in that the base film is composed of pure PET and does not include thermosetting resin and inorganic particles.

[0198] Comparative Example 2

[0199] This comparative example provides a composite current collector, which differs from Example 1 only in that inorganic particles are not added in step a.

[0200] Comparative Example 3

[0201] This comparative example provides a composite current collector, which differs from Example 1 only in that, in step a, an equal mass of thermoplastic resin PET is used instead of phenolic resin.

[0202] Comparative Example 4

[0203] This comparative example provides a composite current collector, which differs from Example 8 only in that, in step a, the addition ratio of silica particles is 0.5% and the addition ratio of phenolic resin is 6%.

[0204] Comparative Example 5

[0205] This comparative example provides a composite current collector. Compared with Example 8, in step a, the addition ratio of silica particles is 12% and the addition ratio of phenolic resin is 40%.

[0206] Comparative Example 6

[0207] This comparative example provides a composite current collector. Compared with Example 8, in step a, the addition ratio of silica particles is 8% and the addition ratio of phenolic resin is 10%.

[0208] Test Case

[0209] 1. Physical property testing of composite current collectors

[0210] The physical properties of the composite current collectors obtained in the various embodiments and comparative examples of this application were tested. The specific test methods are as follows:

[0211] Elongation: Tested according to the elongation test method in GB / T 29847-2013;

[0212] Current collector surface density: Weigh a disc with an area of ​​1540.25 mm². 2 The weight of the composite current collector is used as the surface density of the composite current collector;

[0213] Tensile strength: Tested according to the tensile strength test method in GB / T 29847-2013;

[0214] Performance testing: After 1200 cycles, the composite foil was disassembled to check for delamination between the surface layer and the base film. Specific test results are shown in the table below.

[0215] 2. Electrical performance testing

[0216] The sources of some raw materials used in the preparation of lithium-ion and sodium-ion batteries are as follows:

[0217] Table 2 Sources of Raw Materials

[0218] name Brand factory Artificial graphite FSN-1 Shanshan Technology Hard carbon type2 Kuraray conductive agent Super P French Erythrope dispersant Sodium carboxymethyl cellulose - Mac500 Nippon Paper adhesive 451B Japan Zeon

[0219] 2.1 Preparation of Lithium-ion Full Cells:

[0220] Prepare an 18650 cylindrical battery according to the following steps:

[0221] Negative electrode slurry: The artificial graphite, conductive agent, dispersant and binder are dispersed in water at a mass ratio of 96:1:1:2, with a solid content of 50%, and stirred to form a uniform negative electrode slurry;

[0222] Negative electrode preparation: The negative electrode slurry was coated onto the surface of the composite current collector provided in each embodiment and comparative example using a coater, and then placed in a vacuum oven to be vacuum dried at 120°C for 12 hours, and rolled to obtain a compaction density of 1.5 mg / mm². 3 Electrodes;

[0223] Positive electrode slurry: Lithium iron phosphate, conductive agent and binder are dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3, with a solid content of 70%, and ball milled to form a uniform positive electrode slurry;

[0224] Positive electrode preparation: The positive electrode slurry is coated onto the rough surface of a clean aluminum foil using a coater, and then placed in a vacuum oven and vacuum dried at 120℃ for 12 hours to obtain the electrode sheet with a compacted density of 3.45 g / cm³. 3 ;

[0225] Winding into the casing: The prepared positive and negative electrode plates and separators are stacked in sequence as separator, negative electrode plate, separator, and positive electrode plate and then wound into a core with a diameter of 17mm. Then, it is placed in the casing of the 18650 battery cell.

[0226] Solution injection: Dissolve LiPF6 in a mixed solvent of ethyl carbonate (EC) and diethyl carbonate (DMC) (volume ratio EC:DMC = 1:1) to obtain a LiPF6 solution with a concentration of 1 mol / L. Take 8g of the solution and inject it into the casing and seal it to obtain the finished 18650 battery cell.

[0227] Charging temperature rise test: Using a charge / discharge machine, the battery cell is charged and discharged between 2.5V and 3.65V, with a charging rate of 3C. An external temperature sensor is added during the charging process to detect the maximum temperature rise data of the battery cell during charging.

[0228] High-temperature cycle test: Using a charge / discharge machine, the temperature was controlled at 45℃. The battery cell was charged and discharged between 2.5V and 3.65V, with a charging rate of 1C and a discharging rate of 1C. The charge-discharge cycle test (2.5V to 3.65V) was continuously performed, and the ratio of the discharge capacity to the initial capacity at different number of cycles was measured. The specific test results are shown in Table 4 below.

[0229] 2.2 Preparation of sodium-ion battery:

[0230] Prepare an 18650 cylindrical battery according to the following steps:

[0231] Negative electrode slurry: The hard carbon, conductive agent, dispersant and binder are dispersed in water at a mass ratio of 96:1:1:2, with a solid content of 50%, and stirred to form a uniform negative electrode slurry;

[0232] Negative electrode preparation: The negative electrode slurry was coated onto the surface of the composite current collector provided in each embodiment and comparative example using a coater, and then placed in a vacuum oven to be vacuum dried at 120°C for 12 hours, and rolled to obtain a compaction density of 1.5 mg / cm³. 3 Electrodes;

[0233] Positive electrode homogenate: according to sodium nickel iron manganate (NaNi) 1 / 3 Fe 1 / 3 Mn 1 / 3 O2), conductive agent and binder are dispersed in N-methylpyrrolidone (NMP) in a mass ratio of 95:2:3, with a solid content of 70%, and ball milled to form a uniform positive electrode slurry;

[0234] Positive electrode preparation: The positive electrode slurry is coated onto the rough surface of a clean aluminum foil using a coater, and then placed in a vacuum oven and vacuum dried at 120℃ for 12 hours to obtain the electrode sheet with a compacted density of 3.45 g / cm³. 3 ;

[0235] Winding into the casing: The prepared positive and negative electrode plates and separators are stacked in sequence as separator, negative electrode plate, separator, and positive electrode plate and then wound into a core with a diameter of 17mm. Then, it is placed in the casing of the 18650 battery cell.

[0236] Solution injection: Dissolve NaPF6 in a mixed solvent of ethyl carbonate (EC) and diethyl carbonate (DMC) (volume ratio EC:DMC = 1:1) to obtain a LiPF6 solution with a concentration of 1 mol / L. Take 8g of the solution and inject it into the casing and seal it to obtain the finished 18650 battery cell.

[0237] Charging temperature rise test: Using a charge / discharge machine, the battery cell is charged and discharged between 1.5V and 3.95V, with a charging rate of 3C. An external temperature sensor is added during the charging process to detect the maximum temperature rise of the battery cell during charging.

[0238] High-temperature cycle test: Using a charge / discharge machine, the temperature was controlled at 45℃, and the battery cell was charged and discharged between 1.5V and 3.95V. The charging rate was 1C, and the discharging rate was also 1C. The charge / discharge cycle test (1.5V to 3.95V) was continuously performed, and the ratio of the discharge capacity to the initial capacity at different number of cycles was measured. The specific test results are shown in Table 5 below.

[0239] To facilitate comparison between data, some parameters of the composite current collectors provided in each embodiment and comparative example are listed in Table 3.

[0240] Table 3 Composition information of composite current collectors

[0241]

[0242] Table 4. Test Results of Lithium-ion Battery Full Cells

[0243]

[0244]

[0245] Table 5. Test results of sodium-ion battery full cells

[0246]

[0247] As can be seen from the data in Tables 4 and 5, the composite current collector of this application can achieve low tensile strength and elongation, reducing the difficulty of processing and manufacturing. By adding thermosetting resin and inorganic particles to the composite base film, the safety performance can be improved, the temperature rise during 3C rate charging is significantly reduced, and the capacity retention rate at 45℃ has a significant advantage. As can be seen from the comparison of Examples 10 and 11 with other examples, the doping of elements in the metal layer can improve the bonding ability between the surface layer and the base layer.

[0248] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A composite current collector, characterized in that, include: A composite base film and a metal conductive layer disposed on both sides of the composite base film; The composite base film comprises: thermoplastic resin, thermosetting resin, and inorganic particles. Based on the total mass of the composite base film, the addition ratio of the inorganic particles is a, where 1% ≤ a ≤ 10%; the addition ratio of the thermosetting resin is b, where 8% ≤ b ≤ 35%; and 0.1 ≤ a / b ≤ 0.

65.

2. The composite current collector according to claim 1, characterized in that, The composite base film also includes a conductive agent, and the addition ratio of the conductive agent is 0.2% to 2%. And / or, based on the total mass of the composite base film, the addition ratio of the inorganic particles is a, 3% ≤ a ≤ 8%; the addition ratio of the thermosetting resin is b, 10% ≤ b ≤ 30%; and 0.1 ≤ a / b ≤ 0.

65.

3. The composite current collector according to claim 1 or 2, characterized in that, The metal conductive layer also includes doping elements. The proportion of the doping elements added is c, based on the total mass of the metal conductive layer, where 0.02% ≤ c ≤ 2.5%, and 0.02(a+b) ≤ c ≤ 0.05(a+b).

4. The composite current collector according to claim 1 or 2, characterized in that, The thermoplastic resin includes at least one of polyethylene terephthalate, polypropylene, polyimide, and polyurethane; And / or, the thermosetting resin includes at least one of phenolic resin, epoxy resin, and furan resin; And / or, the inorganic particles include at least one of inorganic nanoparticles and inorganic micron particles; And / or, the conductive agent includes at least one of conductive carbon black, carbon nanofibers, and graphene.

5. The composite current collector according to claim 4, characterized in that, The inorganic particles include at least one of silicon dioxide, titanium dioxide, aluminum oxide, and montmorillonite.

6. The composite current collector according to claim 1 or 2, characterized in that, The thickness of the composite base film is 1 μm to 10 μm; And / or, the thickness of the metal conductive layer is 1 μm to 10 μm.

7. The composite current collector according to claim 1 or 2, characterized in that, The base element of the metallic conductive layer is Al or Cu.

8. The composite current collector according to claim 3, characterized in that, The doping element includes at least one of Fe, Mg, Si, Mn, Ni, and Zn.

9. An electrode sheet, characterized in that, include: The composite current collector according to any one of claims 1-8, and An active material layer disposed on at least one side of the composite current collector.

10. A secondary battery, characterized in that, Includes the electrode sheet as described in claim 9.

11. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 10.

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