Secondary battery and electric device

Abstract

A secondary battery (5) and an electric device. The secondary battery (5) comprises a separator, the separator comprises a base film and a non-woven fabric provided on at least one side of the base film, and the secondary battery (5) comprises a gel electrolyte. The separator can improve the strength of the gel electrolyte, thereby improving the cycle stability of a gel electrolyte battery.

Description

Secondary batteries and electrical devices

[0001] Cross-references

[0002] This application refers to Chinese Patent Application No. 2024103534470, filed on March 26, 2024, entitled “Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and an electrical device. Background Art

[0004] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the widespread use of secondary batteries, higher requirements have been placed on their cycle performance and service life.

[0005] Gel electrolytes are beneficial for improving battery safety performance. However, gel electrolytes have low mechanical strength, and conventional isolation membranes cannot provide support for gel electrolytes, resulting in poor cycle performance of gel electrolyte batteries.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery whose separator can improve the mechanical strength of the gel electrolyte and enhance the cycle stability of the gel electrolyte battery.

[0008] A first aspect of the present application provides a secondary battery including a separator including a base film and a non-woven fabric provided on at least one side of the base film, and the secondary battery includes a gel electrolyte.

[0009] The non-woven fabric has a large pore size and high porosity. The separator includes a base membrane and a non-woven fabric disposed on at least one side of the base membrane, which allows the gel electrolyte to be distributed in the pores of the non-woven fabric. The non-woven fabric serves as a framework for the gel electrolyte and can provide support and system strength for the gel electrolyte, so that the gel electrolyte maintains good mechanical stability during storage, transportation, and circulation, is not prone to shaking off, falling off, or breaking, and is evenly distributed between the positive and negative electrodes, thereby improving the cycle stability of the gel electrolyte battery. Since gel electrolytes are prone to defects, the base membrane in the separator can prevent lithium dendrites or sodium dendrites formed during the charge and discharge process of the gel electrolyte battery from passing through the separator through the defects in the gel electrolyte, causing safety issues such as the positive and negative electrodes being connected and the battery having an internal short circuit. The separator composed of the base membrane and the non-woven fabric disposed on at least one side of the base membrane can improve the mechanical strength of the gel electrolyte and improve the cycle stability and safety performance of the battery.

[0010] In any embodiment, the non-woven fabric includes one or more of polyethylene terephthalate non-woven fabric, polyimide non-woven fabric, polyamide non-woven fabric, polypropylene non-woven fabric, polyvinylidene fluoride non-woven fabric, polyacrylonitrile non-woven fabric, and cellulose non-woven fabric.

[0011] In any embodiment, the porosity of the nonwoven fabric is 50% to 80%.

[0012] In any embodiment, the pore size of the nonwoven fabric is 1 μm to 50 μm.

[0013] The porosity and pore size of the non-woven fabric are within the above ranges, and the isolation membrane can take into account both the load-bearing capacity of the gel electrolyte and the improvement of the mechanical strength of the gel electrolyte. The gel electrolyte battery has good energy density and cycle stability.

[0014] In any embodiment, the nonwoven fabric has a thickness of 9 μm to 15 μm.

[0015] When the thickness of the non-woven fabric is within the above range, the separator can improve the mechanical strength of the gel electrolyte, and the gel electrolyte battery has good energy density and cycle stability.

[0016] In any embodiment, the base film includes one or more of a polyethylene film, a polypropylene film, and a polyimide film.

[0017] In any embodiment, the porosity of the base film is 35% to 45%.

[0018] In any embodiment, the base membrane has a pore size of 5 nm to 80 nm.

[0019] In any embodiment, the base film has a thickness of 3 μm to 15 μm.

[0020] When the porosity, pore size and thickness of the base film are within the above ranges, the separator has good electrochemical properties and can reduce the risk of internal short circuit in the battery, and the gel electrolyte battery has good cycle stability and safety performance.

[0021] In any embodiment, a bonding layer is further included between the base film and the non-woven fabric.

[0022] In any embodiment, the bonding layer includes a bonding agent, and the bonding agent includes one or more of polyhexafluoroethylene and ethylene propylene diene monomer rubber.

[0023] In any embodiment, the preparation method of the gel electrolyte includes an in-situ polymerization method.

[0024] The in-situ polymerization method prepares a gel electrolyte by in-situ initiating the polymerization of a liquid polymer precursor directly inside the battery. This allows the liquid precursor to fully wet the electrode, forming continuous contact and good interfacial compatibility between the electrode and the gel electrolyte. The in-situ polymerization method is also compatible with the existing battery manufacturing industry system, simplifying the assembly process of the gel electrolyte battery. The gel electrolyte prepared by the in-situ polymerization method is evenly dispersed in the non-woven fabric. The non-woven fabric serves as the framework of the gel electrolyte, providing support and system strength for the gel electrolyte, allowing the gel electrolyte to maintain good mechanical stability during storage, transportation and circulation. The gel electrolyte is not easily shaken off, detached or broken, which would cause uneven distribution of the gel electrolyte, thus improving the cycle stability of the gel electrolyte battery.

[0025] In any embodiment, the gel electrolyte includes an organic polymer and / or an organic-inorganic composite polymer.

[0026] In any embodiment, the organic polymer includes one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, and cellulose.

[0027] In any embodiment, the organic-inorganic composite polymer includes one or more of pentaerythritol tetraacrylate-SiO2, polyvinylidene fluoride-hexafluoropropylene-β-Al2O3, and polyvinylidene fluoride-hexafluoropropylene-amine functionalized boron nitride nanosheets.

[0028] In any embodiment, the gel electrolyte includes an ether solvent.

[0029] In any embodiment, the ether solvent includes one or more of ethylene glycol dimethyl ether, cyclopentane, dimethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, and 1,2-methoxypropane.

[0030] In any embodiment, the gel electrolyte includes an electrolyte salt, and the electrolyte salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, and sodium trifluoromethanesulfonate.

[0031] A second aspect of the present application further provides an electrical device comprising the secondary battery of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0033] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0034] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0035] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0036] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0037] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0038] Description of reference numerals:

[0039] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0040] Below, the embodiments of the secondary battery and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0046] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0047] Gel electrolytes have the advantages of preventing electrolyte leakage, low reactivity, and adaptability to new positive and negative electrode materials, which can improve battery safety and energy density. However, gel electrolytes have the disadvantage of low mechanical strength, making it difficult to form a self-supporting electrolyte membrane. Traditional separators (such as polyethylene separators and polypropylene separators) cannot provide support for gel electrolytes. This leads to uneven distribution of gel electrolytes during storage, transportation, and circulation of gel electrolyte batteries, which are prone to shaking, shedding, and breaking, thereby seriously deteriorating the cycle stability of the battery.

[0048] [Secondary battery]

[0049] Based on this, the present application proposes a secondary battery including a separator, the separator including a base film and a non-woven fabric disposed on at least one side of the base film, and the secondary battery including a gel electrolyte.

[0050] In this article, the term "non-woven fabric" refers to non-woven fabric, which refers to a new type of isolation membrane made by using non-woven manufacturing processes such as electrospinning, wet non-woven process, melt blowing, etc. to orient or randomly arrange evenly dispersed fibers to form a three-dimensional network structure, and then reinforced by physical or chemical methods.

[0051] In this article, the term "gel electrolyte" refers to an electrolyte in which a solution containing a polymer matrix, a solvent of electrolyte salts and additives is solidified, and the liquid component is dispersed as a filling medium in the polymer macromolecular space network. This electrolyte contains liquid components but has no fluidity and is called a gel electrolyte.

[0052] In some embodiments, the nonwoven fabric includes one or more of polyethylene terephthalate nonwoven fabric, polyimide nonwoven fabric, polyamide nonwoven fabric, polypropylene nonwoven fabric, polyvinylidene fluoride nonwoven fabric, polyacrylonitrile nonwoven fabric, and cellulose nonwoven fabric.

[0053] In some embodiments, the base film includes one or more of a polyethylene film, a polypropylene film, and a polyimide film.

[0054] In some embodiments, the non-woven fabric is disposed on a side of the base film close to the positive electrode of the battery.

[0055] In some embodiments, the non-woven fabric is disposed on a side of the base film close to the negative electrode of the battery.

[0056] In some embodiments, nonwoven fabrics are disposed on both sides of the base film.

[0057] The non-woven fabric has a large pore size and high porosity. The separator includes a base membrane and a non-woven fabric disposed on at least one side of the base membrane, which allows the gel electrolyte to be distributed in the pores of the non-woven fabric. The non-woven fabric serves as a framework for the gel electrolyte and can provide support and system strength for the gel electrolyte, so that the gel electrolyte maintains good mechanical stability during storage, transportation, and circulation, is not prone to shaking off, falling off, or breaking, and is evenly distributed between the positive and negative electrodes, thereby improving the cycle stability of the gel electrolyte battery. Since gel electrolytes are prone to defects, the base membrane in the separator can prevent lithium dendrites or sodium dendrites formed during the charge and discharge process of the gel electrolyte battery from passing through the separator through the defects in the gel electrolyte, causing safety issues such as the positive and negative electrodes being connected and the battery having an internal short circuit. The separator composed of the base membrane and the non-woven fabric disposed on at least one side of the base membrane can improve the mechanical strength of the gel electrolyte and improve the cycle stability and safety performance of the battery.

[0058] In some embodiments, the nonwoven fabric has a porosity of 50% to 80%.

[0059] In this application, the porosity of a nonwoven fabric can be tested using methods known in the art, such as the gas displacement method, as described in GB / T 24586-2009. The specific process is to use tweezers to select >20 discs of the sample to be tested that are in good appearance and have no powder falling off the edges and place them into a sample cup. The number of discs is recorded and the apparent volume V1 is calculated. The sample cup containing the sample to be tested is then placed in a true density tester, the test system is sealed, and helium is introduced according to the program. The pressure of the gas in the sample chamber and the expansion chamber is detected, and the true volume V2 is calculated according to Bohr's law (PV=nRT). The percentage of the pore volume of the sample to be tested to the total volume of the sample to be tested is the porosity of the sample to be tested. The porosity calculation formula is porosity = (V1-V2) / V1×100%, where V1 is the apparent volume and V2 is the true volume.

[0060] In some embodiments, the nonwoven fabric has a porosity of 50%, 53%, 56%, 59%, 62%, 65%, 68%, 71%, 74%, 77%, 80%, or any value therebetween.

[0061] In some embodiments, the pore size of the nonwoven fabric is 1 μm to 50 μm.

[0062] In the present application, the pore size of the non-woven fabric can be tested by methods known in the art. For example, the following steps are used for testing: (1) Sample preparation: Use scissors to cut a 5mm*5mm non-woven fabric and stick it face up on a sample table with conductive glue, and spray gold (platinum) for 30s; (2) Parameter setting: Use a scanning electron microscope, mode: Optiplan, voltage: 500V, current: 13pA, probe: T1, working distance: 4.5mm; (3) Test process: Move the sample about 100 times to confirm the overall condition of the sample, select the closed hole and focus on 30K, 10K, 5K, 3K, 1K, 500 shots in a group, 30K, 10K, 5K, 3K, 1K, 500 shots in a group at the normal position, take 3 pictures at a small magnification of 200 times, select a 10K picture, measure the pore size, and the pore size of the non-woven fabric can be obtained.

[0063] In some embodiments, the pore size of the nonwoven fabric is 1 μm, 8 μm, 15 μm, 22 μm, 29 μm, 36 μm, 43 μm, 50 μm, or any value therebetween.

[0064] The porosity and pore size of the non-woven fabric are within the above ranges, and the isolation membrane can take into account both the load-bearing capacity of the gel electrolyte and the improvement of the mechanical strength of the gel electrolyte. The gel electrolyte battery has good energy density and cycle stability.

[0065] In some embodiments, the nonwoven fabric has a thickness of 9 μm to 15 μm.

[0066] In this application, the thickness of a nonwoven fabric can be measured using methods known in the art. For example, prepare a nonwoven fabric sample and ensure it is in a safe condition. Place the probe of a thickness gauge on the surface of the nonwoven fabric and record the measurement results. Repeat these steps to measure the thickness of the nonwoven fabric at multiple locations to obtain more accurate data and calculate the average thickness of the nonwoven fabric.

[0067] In some embodiments, the nonwoven fabric has a thickness of 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value therebetween.

[0068] When the thickness of the non-woven fabric is within the above range, the separator can improve the mechanical strength of the gel electrolyte, and the gel electrolyte battery has good energy density and cycle stability.

[0069] In some embodiments, the base film has a porosity of 35% to 45%.

[0070] In some embodiments, the base film has a porosity of 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any value therebetween.

[0071] In some embodiments, the base membrane has a pore size of 5 nm to 80 nm.

[0072] In some embodiments, the pore size of the basement membrane is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, or any value therebetween.

[0073] In some embodiments, the base film has a thickness of 3 μm to 15 μm.

[0074] In some embodiments, the base film has a thickness of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any value therebetween.

[0075] The porosity, pore size and thickness of the base membrane are within the above ranges, the isolation membrane has good electrochemical properties, and the isolation membrane can reduce the probability of lithium dendrites or sodium dendrites passing through the isolation membrane to connect the positive and negative electrodes, and the battery has good cycle stability and safety performance.

[0076] In some embodiments, the separator includes a non-woven fabric sequentially disposed on at least one side of the base film.

[0077] In some embodiments, the base film and the non-woven fabric are thermally laminated to obtain the isolation film.

[0078] In some embodiments, a bonding layer is further included between the base film and the non-woven fabric.

[0079] In some embodiments, the isolation film includes an adhesive layer and a non-woven fabric sequentially disposed on at least one side of the base film.

[0080] In some embodiments, the adhesive layer includes an adhesive, and the adhesive includes one or more of polyhexafluoroethylene and ethylene propylene diene monomer rubber.

[0081] In some embodiments, the preparation method of the gel electrolyte includes an in-situ polymerization method.

[0082] In this article, the term "in situ polymerization method" refers to a preparation method in which a liquid electrolyte containing polymer monomers or prepolymers is injected into a battery, and under certain conditions, a polymerization reaction occurs to form a polymer, thereby converting the liquid electrolyte into a gel electrolyte.

[0083] The in-situ polymerization method prepares a gel electrolyte by in-situ initiating the polymerization of a liquid polymer precursor directly inside the battery. This allows the liquid precursor to fully wet the electrode, forming continuous contact and good interfacial compatibility between the electrode and the gel electrolyte. The in-situ polymerization method is also compatible with the existing battery manufacturing industry system, simplifying the assembly process of the gel electrolyte battery. The gel electrolyte prepared by the in-situ polymerization method is evenly dispersed in the non-woven fabric. The non-woven fabric serves as the framework of the gel electrolyte, providing support and system strength for the gel electrolyte, allowing the gel electrolyte to maintain good mechanical stability during storage, transportation and circulation. The gel electrolyte is not easily shaken off, detached or broken, which would cause uneven distribution of the gel electrolyte, thus improving the cycle stability of the gel electrolyte battery.

[0084] In some embodiments, the gel electrolyte includes an organic polymer and / or an organic-inorganic composite polymer.

[0085] In this context, the term "polymer" includes, on the one hand, a collection of chemically uniform macromolecules prepared by polymerization reactions, but differing in degree of polymerization, molar mass and chain length; on the other hand, it also includes derivatives of such a collection of macromolecules formed by polymerization reactions, i.e. polymers that can be obtained by reactions of functional groups in the above-mentioned macromolecules, such as addition or substitution, and which can be chemically uniform or chemically heterogeneous.

[0086] As used herein, the term "organic-inorganic polymer" refers to a polymer formed by combining organic and inorganic materials in some manner.

[0087] In some embodiments, the organic polymer includes one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, and cellulose.

[0088] As used herein, the term "polyethylene oxide" refers to polymers of varying degrees of polymerization prepared by ring-opening polymerization of ethylene oxide.

[0089] As used herein, the term "polyacrylonitrile" refers to a polymer obtained by free radical polymerization of the monomer acrylonitrile.

[0090] As used herein, the term "polymethyl methacrylate" refers to a polymer obtained by free radical polymerization of the monomer methyl methacrylate.

[0091] As used herein, the term "polyvinylidene fluoride" refers to a polyvinylidene fluoride obtained by free radical polymerization of the monomer 1,1-difluoroethylene.

[0092] As used herein, the term "polyvinylidene fluoride-hexafluoropropylene" refers to a copolymer of vinylidene fluoride monomers and hexafluoropropylene monomers.

[0093] As used herein, the term "polyimide" refers to a class of polymers containing an imide ring (-CO-NR-CO-) in the main chain.

[0094] In some embodiments, the organic-inorganic composite polymer includes one or more of pentaerythritol tetraacrylate-SiO2, polyvinylidene fluoride-hexafluoropropylene-β-Al2O3, and polyvinylidene fluoride-hexafluoropropylene-amine functionalized boron nitride nanosheets.

[0095] In this article, the term "boron nitride nanosheets" refers to a nanometer-sized sheet structure composed of boron nitride (BN) atoms. Amine-functionalized boron nitride nanosheets refer to boron nitride nanosheets modified with -NH2 groups or NHR groups.

[0096] In some embodiments, the gel electrolyte includes an ether solvent.

[0097] As used herein, the term "ether" refers to a product in which the hydrogen of the hydroxyl group of an alcohol or phenol is replaced by a hydrocarbon group, and has the general formula RO-R', where R and R' may be the same or different.

[0098] In some embodiments, the ether solvent includes one or more of ethylene glycol dimethyl ether, cyclopentane, dimethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, and 1,2-methoxypropane.

[0099] In some embodiments, the gel electrolyte includes an electrolyte salt, and the electrolyte salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, and sodium trifluoromethanesulfonate.

[0100] In some embodiments, the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.

[0101] [Positive electrode tab]

[0102] The positive electrode tab generally includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material.

[0103] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0104] In some embodiments, the positive electrode active material may adopt the positive electrode active materials known in the art for batteries. As an example, the positive electrode active material may include at least one of the following materials: Prussian blue analogues, sodium-containing phosphates, sodium-containing transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, the Prussian blue analogue is Na x P[R(CN)6] δ ·zH2O, where P and R are each independently selected from at least one of transition metal elements, 0 < x ≤ 2, 0 < δ ≤ 1 and 0 ≤ z ≤ 10; the sodium-containing phosphate is Na b Me c (PO4) d O2X, where A is one or more of H, Li, Na, K and NH4, Me is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X is one or more of F, Cl and Br, 0 < b ≤ 4, 0 < c ≤ 2, 1 ≤ d ≤ 3; the sodium-containing transition metal oxide is Na a M b N c Fe d Mn e O2, M and N include at least one of Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb, 0.05 ≤ b ≤ 0.2, 0.2 ≤ c ≤ 0.3, 0.2 ≤ d ≤ 0.3, 0.3 ≤ e ≤ 0.4, 0.75 ≤ a / (b + c + d + e) ≤ 1.

[0105] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0107] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0109] [Negative electrode]

[0110] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.

[0111] In some embodiments, the negative electrode film layer includes a negative electrode active material. In other embodiments, the negative electrode film layer substantially does not contain a negative electrode active material and may include a small amount of carbon material, but the carbon material forms a thin coating and cannot function as a negative electrode active material.

[0112] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0113] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil or aluminum foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0114] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0115] In some embodiments, the negative electrode film layer may further include a binder. For example, 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).

[0116] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, 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.

[0117] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0118] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0119] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0120] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0121] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0122] In this application, the shape of the secondary battery includes but is not limited to cylindrical, square or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0123] In some embodiments, referring to FIG2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0124] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0125] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0126] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0127] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0128] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0129] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0130] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0131] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0132] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0133] Example

[0134] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0135] 1. Preparation method

[0136] Example 1:

[0137] 1) Preparation of isolation membrane

[0138] Using a polyethylene film as the base film, a 10% solids solution of polyhexafluoroethylene in deionized water is sprayed on both sides to form an adhesive layer. The solvent in the adhesive layer is then removed by drying. The base film with the adhesive layer is then dried again. After drying, a non-woven fabric is laminated on both sides of the base film. The base film is 7μm thick, has a porosity of 40%, and a pore size of 35nm. The non-woven fabric on each side is 12μm thick and made of polyethylene terephthalate (PET) with a porosity of 60% and a pore size of 30μm.

[0139] 2) Preparation of electrolyte

[0140] In an argon-filled glove box with a water content of <1 ppm, diethylene glycol dimethyl ether and tetrahydrofuran were mixed in a mass ratio of 1:3, sodium hexafluorophosphate (NaPF6) was added, and after stirring evenly, an electrolyte with a NaPF6 concentration of 1.0 mol / L was obtained.

[0141] Polymethyl methacrylate (5% by mass of the electrolyte) was added to the above electrolyte, and the mixture was stirred evenly to obtain an electrolyte containing a curing agent.

[0142] 3) Preparation of negative electrode sheet

[0143] The negative electrode active material hard carbon, the conductive agent carbon black, and the binder sodium carboxymethyl cellulose are fully stirred and mixed in a deionized water solvent system in a mass ratio of 90:5:5 to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; the copper foil is dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet.

[0144] 4) Preparation of positive electrode sheet

[0145] 10 wt% of polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, 10 wt% of carbon black conductive agent and 80 wt% of positive electrode active material Na4Fe3(PO4)2(P2P7) were added and dispersed evenly to prepare positive electrode slurry. The positive electrode slurry was evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting and cutting, the positive electrode sheet was obtained.

[0146] 5) Preparation of batteries

[0147] The positive electrode sheet, the isolation film, and the negative electrode sheet are stacked in order, so that the isolation film is placed in the middle of the positive and negative electrode sheets to isolate the positive and negative electrode sheets. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer package, and the prepared electrolyte containing a curing agent is injected into the dried battery cell. After standing, forming, and fully discharging at a rate of 0.33C to a voltage of 1.5V, it is cured at 70±5°C for 12 hours, and then the prepared electrolyte is injected. After shaping, capacity testing and other processes, the secondary battery product of Example 1 is obtained.

[0148] Example 2

[0149] The preparation method of the secondary battery of Example 2 is substantially the same as that of Example 1, except that the base film of the isolation film is a polyimide film.

[0150] Comparative Example 1

[0151] The preparation method of the secondary battery of Comparative Example 1 is substantially the same as that of Example 1, except that the separator is made of polyethylene alone.

[0152] Comparative Example 2

[0153] The preparation method of the secondary battery in Comparative Example 2 is substantially the same as that in Example 1, except that the separator is a separate non-woven fabric.

[0154] 2. Battery performance test

[0155] 1. Gel electrolyte shaking off

[0156] Vibration standard test: Charge the battery at a constant current of 1C to 3.65V, then charge it at a constant voltage of 3.65V until the current is less than 0.05C. The fully charged battery is subjected to a vibration test at a temperature of 20±5°C using a high-frequency battery vibration tester (Maike Instrument LJ-5020) with an amplitude of 0.8mm and a vibration frequency of 1 Hz / min, ranging from 10-55Hz, in three mutually perpendicular directions (the long side of the battery is the X-axis, the short side of the battery is the Y-axis, and the normal position of the battery is the Z-axis). Each axis is tested for 90 minutes. Disassemble the battery cell and observe the distribution of the gel electrolyte. If the gel electrolyte accumulates at the bottom of the cell, it is judged to have failed the vibration test and the test result is N, indicating that the gel electrolyte has shaken off. If there is no accumulation of gel electrolyte at the bottom of the cell, it is judged to have passed the vibration test and the test result is Y, indicating that the gel electrolyte has not shaken off.

[0157] 2. Battery cycle number

[0158] Batteries from each of the aforementioned examples and comparative examples were tested in parallel. Each battery cell was charged at 0.33C to a voltage of 3.65V at 25°C, then discharged at 0.33C to a voltage of 1.5V. The reversible capacity (C0) was measured. This charge and discharge cycle was repeated until the discharge capacity (Cn / C0) at a given cycle was ≤80%. The total number of cycles was recorded as X-Cycle. Cn is the reversible capacity at the nth cycle.

[0159] 3. Analysis of test results of various embodiments and comparative examples

[0160] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in the table below.

[0161] Table 1

[0162] As can be seen from Examples 1 and 2, the secondary battery of the embodiment includes a separator, and the separator includes a base film and a non-woven fabric provided on at least one side of the base film.

[0163] It can be seen from Examples 1 and 2 that the gel electrolyte of the secondary battery does not fall off after the vibration test, and the battery has good cycle stability.

[0164] From the comparison between Examples 1 and 2 and Comparative Examples 1 and 2, it can be seen that the separator obtained by compounding the base film and the non-woven fabric can improve the strength of the gel electrolyte and enhance the cycle stability and safety performance of the battery.

[0165] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery comprising a separator, characterized in that: The separator includes a base film and a non-woven fabric disposed on at least one side of the base film, and the secondary battery includes a gel electrolyte.

2. The secondary battery according to claim 1, wherein The non-woven fabric includes one or more of polyethylene terephthalate non-woven fabric, polyimide non-woven fabric, polyamide non-woven fabric, polypropylene non-woven fabric, polyvinylidene fluoride non-woven fabric, polyacrylonitrile non-woven fabric, and cellulose non-woven fabric.

3. The secondary battery according to claim 1 or 2, characterized in that The porosity of the non-woven fabric is 50%-80%; and / or, The pore size of the non-woven fabric is 1 μm-50 μm; and / or, The non-woven fabric has a thickness of 9 μm-15 μm.

4. The secondary battery according to any one of claims 1 to 3, characterized in that The base film includes one or more of a polyethylene film, a polypropylene film, and a polyimide film.

5. The secondary battery according to any one of claims 1 to 4, characterized in that The porosity of the base film is 35%-45%; and / or, The pore size of the basement membrane is 5nm-80nm; and / or, The base film has a thickness of 3 μm-15 μm.

6. The secondary battery according to any one of claims 1 to 5, characterized in that An adhesive layer is further included between the base film and the non-woven fabric.

7. The secondary battery according to claim 6, characterized in that The bonding layer includes a bonding agent, and the bonding agent includes one or more of polyhexafluoroethylene and ethylene propylene diene monomer rubber.

8. The secondary battery according to any one of claims 1 to 7, characterized in that The preparation method of the gel electrolyte includes an in-situ polymerization method.

9. The secondary battery according to any one of claims 1 to 8, characterized in that The gel electrolyte comprises an organic polymer and / or an organic-inorganic composite polymer; The organic polymer includes one or more of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, and cellulose; the organic-inorganic composite polymer includes one or more of pentaerythritol tetraacrylate-SiO2, polyvinylidene fluoride-hexafluoropropylene-β-Al2O3, and polyvinylidene fluoride-hexafluoropropylene-amine functionalized boron nitride nanosheets.

10. The secondary battery according to any one of claims 1 to 9, characterized in that The gel electrolyte includes an ether solvent; The ether solvent includes one or more of ethylene glycol dimethyl ether, cyclopentane, dimethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, and 1,2-methoxypropane.

11. The secondary battery according to any one of claims 1 to 10, characterized in that The gel electrolyte includes electrolyte salt, and the electrolyte salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, and sodium trifluoromethanesulfonate.

12. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 11.

Images