Isolating membrane and preparation method thereof, secondary battery and electric device

Abstract

The embodiment of the invention provides an isolating membrane and a preparation method thereof, a secondary battery and an electric device. The isolating membrane comprises a first base membrane, a coating and a second base membrane, the coating is arranged between the first base membrane and the second base membrane, the coating comprises an ion trapping agent, and the reduction potential of the ion trapping agent relative to lithium metal is 0-2V. The cycle performance of the secondary battery containing the isolating membrane is improved.

Description

Separator and preparation method thereof, secondary battery and electric device Technical Field

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

[0002] In recent years, the application scope of secondary batteries has become increasingly wide. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] As secondary batteries have made great progress, higher requirements have been placed on their electrochemical and other performances. Therefore, how to provide a secondary battery with good performance is a technical problem that needs to be solved urgently.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned technical problems, and its purpose is to provide an isolation membrane and a preparation method thereof, a secondary battery and an electrical device, wherein the cycle performance of the secondary battery containing the isolation membrane is improved.

[0006] In a first aspect, an isolation membrane is provided, comprising a first base membrane, a coating and a second base membrane, wherein the coating is arranged between the first base membrane and the second base membrane, the coating comprises an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V.

[0007] In the embodiment of the present application, the isolation membrane includes an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V. The positive electrode material is an important component of the secondary battery and directly affects the performance of the secondary battery. The positive electrode material containing transition metals will inevitably undergo the phenomenon of transition metal ion dissolution in the electrochemical environment. On the one hand, the dissolved transition metal ions destroy the structural stability of the original positive electrode material and thus affect the life of the secondary battery. On the other hand, the dissolved transition metal ions will migrate and deposit on the surface of the negative electrode material, catalyzing the decomposition and regeneration of the electrolyte and the negative electrode interface film, continuously consuming reversible active metals, and ultimately leading to a decrease in the performance of the secondary battery. In the technical solution of the embodiment of the present application, the reduction potential of the ion capture agent in the isolation membrane relative to lithium metal is 0 to 2V, and the reduction potential of the transition metal ions relative to lithium metal is generally above 2V. Therefore, the ion capture agent can reduce the transition metal ions dissolved in the secondary battery into low-valent ions that are not easily dissolved, or reduce them to metal elements, thereby improving the situation where the transition metal ions catalyze the decomposition of the electrolyte and the negative electrode interface film, thereby improving the cycle performance of the secondary battery. In addition, due to H +The reduction potential of the ion scavenger relative to lithium metal is higher than that of the transition metal ion relative to lithium metal, so the ion scavenger can also convert the H + Reduction, that is, to remove acidic substances in the electrolyte (such as HF, organic acid RH + , H· free radicals, etc.), further improving the performance of the secondary battery. The coating is disposed between the first and second base films. This reduces the likelihood of the ion scavenger coming into direct contact with the positive and negative electrode active materials when the positive electrode sheet, separator, and negative electrode sheet are sequentially stacked and wound into an electrode assembly. This reduces the risk of the ion scavenger losing its redox activity and the risk of the ion scavenger affecting the performance of the positive and negative electrode active materials. Furthermore, the separator, which includes both the first and second base films, can further enhance its mechanical strength.

[0008] In a possible implementation, the ion capture agent includes at least one of an active metal and an alkali metal compound. Optionally, the active metal includes at least one of Li, Na, K, Rb, Cs, Fr, Mg, Ca, Sr, Ba, Al, Ti, or V; Optionally, the active metal includes at least one of Li, Na, Mg, Al, Ti, or V; Optionally, the alkali metal compound includes A 1 x B, A 2 y Ti5O 12 , and at least one of the compounds represented by formula (I), formula (II) or formula (III):

[0009] Among them, A 1 、A 2 、A 3 、A 4 、A 5 、A 6 Each independently includes at least one of Li, Na or K, B includes C, Si or Sn, x≥0.05, y>4, R, R1, R2, R3, and R4 independently include a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 2 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 6 to 7 carbon atoms, at least one of an aryl group having 1 to 26 carbon atoms, an aryl group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carboxyl group having 1 to 20 carbon atoms, a carboxyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carbonyl group having 1 to 20 carbon atoms, a carbonyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an aryloxy group having 6 to 26 carbon atoms, and an aryloxy group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group.

[0010] In a possible implementation, the A 1 x B includes Li 1 / 6 C, Na 1 / 6 C, K 1 / 8 C. Li 4.4 Si, or Li 4.4 At least one of Sn.

[0011] In a possible implementation, 5≤y≤7, the A 2 y Ti5O 12 Including Li7Ti5O 12 or Na7Ti5O 12 At least one of .

[0012] In one possible implementation, the compound represented by formula (I) includes at least one of n-butyllithium, naphthyllithium or biphenyllithium.

[0013] In one possible implementation, the compound represented by formula (II) comprises At least one of .

[0014] In one possible implementation, the compound represented by formula (III) comprises At least one of .

[0015] In a possible implementation, the mass of the ion capture agent per unit area of ​​the isolation membrane is 0.12 g / m 2 ~24g / m 2 Optionally, the mass of the ion capture agent per unit area of ​​the isolation membrane is 0.48 g / m 2 ~12g / m 2 .

[0016] If the mass of the ion capture agent per unit area of ​​the separator is too small, the content of the ion capture agent in the separator is too low, and the ion capture agent cannot effectively play the role of chemical reaction to reduce transition metal ions. If the mass of the ion capture agent per unit area of ​​the separator is too large, it will block more pores in the base membrane, resulting in a significant reduction in the migration channels of active metal ions in the separator, thereby significantly increasing the internal resistance of the secondary battery and deteriorating the performance of the secondary battery. For example, it will affect the cycle performance of the secondary battery and increase production costs. Therefore, setting the mass of the ion capture agent per unit area of ​​the separator within an appropriate range is beneficial to improving the performance of the secondary battery.

[0017] In a possible implementation, the mass proportion of the ion capture agent in the coating is 50% to 99%. Optionally, the mass proportion of the ion capture agent in the coating is 80% to 98%.

[0018] The mass proportion of the ion capture agent in the coating is within the given range, and the ion capture agent can play a good role in reducing transition metal ions, thereby further improving the cycle performance of the battery.

[0019] In one possible implementation, the first base film and the second base film independently include at least one of polyolefins and their derivatives, halogenated polyolefins and their derivatives, polyethers and their derivatives, polyetheretherketones and their derivatives, polyesters and their derivatives, polyimides and their derivatives, and polyvinyl alcohols and their derivatives; optionally, the halogenated polyolefins and their derivatives include at least one of polytetrafluoroethylene and their derivatives, polyvinyl fluoride and their derivatives, and polyvinylidene fluoride and their derivatives; optionally, the polyesters and their derivatives include at least one of polyethylene terephthalate and its derivatives, and polybutylene terephthalate and its derivatives.

[0020] In one possible implementation, the coating further includes a binder; optionally, the binder includes at least one of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, or cyanoethyl pullulan.

[0021] The ion capture agent in the coating layer can be bonded to the first base film and the second base film through the adhesive, so that there is good bonding force between the ion capture agent and the first base film and the second base film, thereby improving the overall structural strength of the isolation membrane.

[0022] In one possible implementation, the coating further includes a filler; optionally, the filler includes at least one of inorganic particles, organic particles, or an organic-metal framework material; optionally, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or greater or inorganic particles having ion conductivity but not storing ions; optionally, the organic particles include at least one of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifier, melamine resin, phenolic resin, polyester, silicone resin, polyimide, polyamideimide, polyaromatic amide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, or a copolymer of butyl acrylate and ethyl methacrylate; optionally, the organic-metal framework material includes at least one of a nitrogen-containing heterocyclic ligand building structure, an organic carboxylic acid ligand building structure, and a nitrogen-oxygen mixed ligand building structure.

[0023] In the second aspect, a method for preparing an isolation membrane is provided, comprising providing a first base membrane and a second base membrane; providing a coating slurry, wherein the coating slurry comprises an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2 V; coating the coating slurry on the first base membrane and / or the second base membrane; and compounding the first base membrane and the second base membrane to obtain an isolation membrane.

[0024] In a third aspect, a secondary battery is provided, comprising the isolation membrane in the first aspect and any possible implementation thereof.

[0025] In a fourth aspect, an electrical device is provided, comprising the secondary battery described in the third aspect.

[0026] An embodiment of the present application provides a separator, comprising a first base film, a coating, and a second base film, wherein the coating is disposed between the first base film and the second base film, and the coating comprises an ion scavenger, wherein the ion scavenger has a reduction potential of 0 to 2 V relative to lithium metal. Positive electrode materials are an important component of secondary batteries and directly affect the performance of secondary batteries. Transition metal-containing positive electrode materials inevitably experience the phenomenon of transition metal ion dissolution in an electrochemical environment. On the one hand, the dissolved transition metal ions destroy the structural stability of the original positive electrode material, thereby affecting the life of the secondary battery. On the other hand, the dissolved transition metal ions migrate and deposit on the surface of the negative electrode material, catalyzing the decomposition and regeneration of the electrolyte and the negative electrode interface film, continuously consuming reversible active metals, and ultimately leading to a decline in secondary battery performance. In the technical solution of the embodiment of the present application, the reduction potential of the ion capture agent in the isolation membrane relative to lithium metal is 0-2V, while the reduction potential of transition metal ions relative to lithium metal is generally above 2V. Therefore, the ion capture agent can reduce the transition metal ions dissolved in the secondary battery into low-valent ions that are difficult to dissolve, or reduce them to metal elements, thereby improving the situation where the transition metal ions catalyze the decomposition of the electrolyte and the negative electrode interface film, thereby improving the cycle performance of the secondary battery. In addition, due to H + The reduction potential of the ion scavenger relative to lithium metal is higher than that of the transition metal ion relative to lithium metal, so the ion scavenger can also convert the H + Reduction, that is, to remove acidic substances in the electrolyte (such as HF, organic acid RH + , H· free radicals, etc.), further improving the performance of the secondary battery. The coating is disposed between the first and second base films. This reduces the likelihood of the ion scavenger coming into direct contact with the positive and negative electrode active materials when the positive electrode sheet, separator, and negative electrode sheet are sequentially stacked and wound into an electrode assembly. This reduces the risk of the ion scavenger losing its redox activity and the risk of the ion scavenger affecting the performance of the positive and negative electrode active materials. Furthermore, the separator, which includes both the first and second base films, can further enhance its mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0028] FIG1 is a schematic diagram of an isolation membrane disclosed in one embodiment of the present application;

[0029] [Corrected 26.06.2023 in accordance with Article 91][Deleted]

[0030] [Corrected 26.06.2023 according to Rule 91] FIG2 is a schematic diagram of a method for preparing an isolation membrane disclosed in one embodiment of the present application;

[0031] [Corrected 26.06.2023 according to Rule 91] FIG3 is a schematic diagram of a battery cell disclosed in one embodiment of the present application;

[0032] [Corrected 26.06.2023 according to Rule 91] FIG4 is a schematic diagram of the exploded structure of a battery cell disclosed in one embodiment of the present application;

[0033] [Corrected 26.06.2023 according to Rule 91] FIG5 is a schematic diagram of the exploded structure of a battery disclosed in one embodiment of the present application;

[0034] [Corrected 26.06.2023 according to Rule 91] Figure 6 is a schematic diagram of an electrical device disclosed in an embodiment of the present application.

[0035] In the drawings, the drawings are not drawn to scale. DETAILED DESCRIPTION

[0036] Below, the embodiments of the separator, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0037] In the description of this application, it should be noted that, unless otherwise specified, "plurality" means more than two; terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are merely for the purpose of facilitating the description of this application and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting this application. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] " 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.

[0039] If not otherwise specified, the “include” and “comprising” mentioned in this application represent open-endedness. For example, the “include” and “comprising” may mean including or comprising other components not listed.

[0040] Unless otherwise specified, the term "and / or" is inclusive in this application. For example, the phrase "A and / or B" means "A, B, or both A and B." More specifically, the condition "A and / 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).

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] 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.

[0043] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0044] "Alkyl" refers to a monovalent saturated hydrocarbon group having one or more carbon atoms, optionally 1 to 20. For example, alkyl includes straight-chain and branched hydrocarbon groups, such as methyl (CH3-), ethyl (CH3CH2-), n-propyl (CH3CH2CH2-), isopropyl ((CH3)2CH-), n-butyl (CH3CH2CH2CH2-), isobutyl ((CH3)2CHCH2-), sec-butyl ((CH3)(CH3CH2)CH-), tert-butyl ((CH3)3C-), n-pentyl (CH3CH2CH2CH2CH2-), neopentyl ((CH3)3CCH2-), and the like.

[0045] "Alkenyl" refers to a straight or branched hydrocarbon group having one or more carbon atoms and at least one double bond unsaturated site, optionally with 2 to 20 carbon atoms, such as ethenyl (CH2=CH-), propenyl (CH3CH=CH-), allyl (CH2=CH-CH2-), n-butenyl (-CH3CH2CH=CH-), etc.

[0046] "Aryl" refers to an aromatic compound having a single ring or multiple condensed rings, optionally with 6 to 26 carbon atoms. Examples of aryl groups include phenyl, naphthyl, and indenyl. Aryl groups also include single rings fused to an aryl group, such as tetrahydronaphthyl and indanyl.

[0047] "Carboxyl" refers to a group having one or more carbon atoms and a -CO2H functional group, optionally with 1 to 20 carbon atoms.

[0048] "Carbonyl" refers to a group having one or more carbon atoms and a -CO- functional group, and optionally, the number of carbon atoms is 1 to 20.

[0049] "Aryloxy" refers to a group formed by linking at least one carbon atom on the aromatic ring of an aryl group to an oxygen atom, and optionally, the number of carbon atoms is 6 to 26.

[0050] "Sulfonic acid" refers to -SO3H.

[0051] "Sulfonyl" refers to RS(=O)2-, where R includes hydrogen, alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, heteroaryl, heterocyclic, and the like.

[0052] A secondary battery is a battery that can be recharged after discharge to reactivate its active materials and allow continued use. Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the charge and discharge process, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0053] In recent years, the application scope of secondary batteries has become increasingly wide. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0054] As secondary batteries have made great progress, higher requirements have been placed on their energy density, cycle performance, safety performance, service life, etc. Therefore, how to provide a secondary battery with good performance is a technical problem that needs to be solved urgently.

[0055] Positive electrode materials are one of the key materials that determine the performance of secondary batteries. They mainly include metal oxides and polyanion salts. Among them, layered metal oxides and spinel metal oxides containing transition metals are widely used as positive electrode materials. These transition metal-containing positive electrode materials have advantages such as high energy density and good cycle performance, which are beneficial to improving the performance of secondary batteries. However, transition metal-containing positive electrode materials inevitably experience the phenomenon of transition metal ion dissolution in the electrochemical environment. On the one hand, the dissolved transition metal ions destroy the structural stability of the original positive electrode material, thereby affecting the life of the secondary battery. On the other hand, the dissolved transition metal ions will migrate and deposit on the surface of the negative electrode material, catalyzing the decomposition and regeneration of the electrolyte and the negative electrode interface film, continuously consuming the reversible active metal, and ultimately leading to a decline in the performance of the secondary battery.

[0056] In view of this, an embodiment of the present application provides an isolation membrane, which includes a first base membrane, a coating and a second base membrane. The coating is arranged between the first base membrane and the second base membrane. The coating includes an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V, while the reduction potential of transition metal ions relative to lithium metal is generally above 2V. Therefore, the ion capture agent can reduce the transition metal ions dissolved in the secondary battery into low-valent ions that are not easily dissolved, or reduce them to metal elements, thereby improving the catalytic decomposition of the electrolyte and the negative electrode interface film by the transition metal ions, thereby improving the cycle performance of the secondary battery. In addition, due to H + The reduction potential of the ion scavenger relative to lithium metal is higher than that of the transition metal ion relative to lithium metal, so the ion scavenger can also convert the H +Reduction, that is, to remove acidic substances in the electrolyte (such as HF, organic acid RH + , H· free radicals, etc.), further improving the performance of the secondary battery. The coating is disposed between the first and second base films. This reduces the likelihood of the ion scavenger coming into direct contact with the positive and negative electrode active materials when the positive electrode sheet, separator, and negative electrode sheet are sequentially stacked and wound into an electrode assembly. This reduces the risk of the ion scavenger losing its redox activity and the risk of the ion scavenger affecting the performance of the positive and negative electrode active materials. Furthermore, the separator, which includes both the first and second base films, can further enhance its mechanical strength.

[0057] [Isolation film]

[0058] Figure 1 is a schematic diagram of an isolation membrane 1 according to one embodiment of the present application. As shown in Figure 1 , isolation membrane 1 includes a first base film 121, a second base film 122, and a coating layer 11, with coating layer 11 disposed between first base film 121 and second base film 122. The first base film 121, coating layer 11, and second base film 122 are disposed sequentially along the thickness direction of isolation membrane 1 (e.g., the z-direction in Figure 1 ). Coating layer 11 includes an ion scavenger, and the ion scavenger has a reduction potential of 0 to 2 V relative to lithium metal.

[0059] The ion scavengers described here are substances capable of consuming free transition metal ions in battery cells. The reduction potential of ion scavengers relative to lithium metal is 0-2V, while the reduction potential of transition metal ions relative to lithium metal is generally above 2V. Therefore, ion scavengers have a stronger reducing ability than transition metal ions. Ion scavengers can reduce free transition metal ions to low-valent ions that are insoluble in the electrolyte, or to elemental metals.

[0060] Positive electrode materials are an important component of secondary batteries and directly affect the performance of secondary batteries. Positive electrode materials containing transition metals will inevitably experience the dissolution of transition metal ions in the electrochemical environment. On the one hand, the dissolved transition metal ions destroy the structural stability of the original positive electrode material, thereby affecting the life of the secondary battery. On the other hand, the dissolved transition metal ions will migrate and deposit on the surface of the negative electrode material, catalyzing the decomposition and regeneration of the electrolyte and the negative electrode interface film, continuously consuming reversible active metals, and ultimately leading to a decline in the performance of the secondary battery.

[0061] For example, the positive electrode material may include a phosphate material with an olivine structure, a material with a spinel structure, or a transition metal oxide with a layered structure. Specifically, for example, lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LiMnFePO4), lithium manganese oxide (LiMn2O4), and ternary materials. The iron ions, nickel ions, and manganese ions in the above-mentioned positive electrode materials are all susceptible to dissolution from the positive electrode materials.

[0062] The isolation membrane provided by the embodiment of the present application includes an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V, while the reduction potential of transition metal ions relative to lithium metal is generally above 2V. Therefore, the ion capture agent can reduce the transition metal ions dissolved in the secondary battery into low-valent ions that are difficult to dissolve, or reduce them to metal elements, thereby improving the situation where the transition metal ions catalyze the decomposition of the electrolyte and the negative electrode interface film, thereby improving the cycle performance of the secondary battery. In addition, due to H + The reduction potential of the ion scavenger relative to lithium metal is higher than that of the transition metal ion relative to lithium metal, so the ion scavenger can also convert the H + Reduction, that is, to remove acidic substances in the electrolyte (such as HF, organic acid RH + , H· free radicals, etc.), further improving the performance of the secondary battery. The coating is disposed between the first and second base films. This reduces the likelihood of the ion scavenger coming into direct contact with the positive and negative electrode active materials when the positive electrode sheet, separator, and negative electrode sheet are sequentially stacked and wound into an electrode assembly. This reduces the risk of the ion scavenger losing its redox activity and the risk of the ion scavenger affecting the performance of the positive and negative electrode active materials. Furthermore, the separator, which includes both the first and second base films, can further enhance its mechanical strength.

[0063] It should be understood that in the embodiments of the present application, different types of ion capture agents can be selected according to different types of free transition metal ions dissolved in the secondary battery.

[0064] Alternatively, in some embodiments, the ion capture agent includes at least one of a compound of an active metal and an alkali metal.

[0065] Specifically, the active metal may include at least one of Li, Na, K, Rb, Cs, Fr, Mg, Ca, Sr, Ba, Al, Ti or V. Optionally, the active metal includes at least one of Li, Na, Mg, Al, Ti or V.

[0066] Optionally, the alkali metal compound includes A 1 x B, A 2 y Ti5O 12 , and at least one of the compounds represented by formula (I), formula (II) or formula (III):

[0067] Among them, A 1 、A 2 、A 3 、A 4 、A 5 、A 6Each independently includes at least one of Li, Na, and K, B includes C, Si, or Sn, x≥0.05, y>4, R, R1, R2, R3, and R4 each independently include a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 2 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 6 to 7 carbon atoms, at least one of an aryl group having 1 to 26 carbon atoms, an aryl group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carboxyl group having 1 to 20 carbon atoms, a carboxyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carbonyl group having 1 to 20 carbon atoms, a carbonyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an aryloxy group having 6 to 26 carbon atoms, and an aryloxy group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group.

[0068] In the embodiments of the present application, the dotted line in formula (II) indicates that R1 and R2 may be connected to form a ring or may not be connected; the dotted line in formula (III) indicates that R3 and R4 may be connected to form a ring or may not be connected.

[0069] Optionally, A 1 x B includes LiC6, NaC6, KC8, Li 4.4 Si, Li 4.4 Sn or Li 22 At least one of Si5.

[0070] In the embodiment of the present application, A 1 x The value of x in B is related to the specific substance selected for B. For example, when B is carbon (C), the upper limit of the value of x is 1 / 6; for another example, when B is silicon (Si) or tin (Sn), the upper limit of the value of x is 4.4.

[0071] Optionally, 5≤y≤7, A 2 y Ti5O 12 Including Li7Ti5O 12 or Na7Ti5O 12 At least one of .

[0072] Optionally, the compound represented by formula (I) includes at least one of n-butyllithium, naphthyllithium or biphenyllithium.

[0073] Optionally, the compound represented by formula (II) comprises At least one of .

[0074] Optionally, the compound represented by formula (III) comprises At least one of .

[0075] Optionally, in some embodiments, the mass of the ion capture agent per unit area of ​​the isolation membrane 1 is 0.12 g / m 2 ~24g / m 2 Optionally, the mass of the ion capture agent per unit area of ​​the isolation membrane 1 is 0.48 g / m 2 ~12g / m 2 .

[0076] Specifically, the mass of the ion capture agent per unit area of ​​the separator 1 can be 0.12 g / m 2 , 0.48g / m 2 , 1g / m 2 , 4g / m 2 , 8g / m 2 , 12g / m 2 , 16g / m 2 , 20g / m 2 , 24g / m 2 , or a value between any two of the above values.

[0077] If the mass of the ion capture agent per unit area of ​​the separator 1 is too small, the content of the ion capture agent in the separator 1 is too low, and the ion capture agent cannot effectively reduce the transition metal ions through chemical reactions. If the mass of the ion capture agent per unit area of ​​the separator 1 is too large, it will block more pores in the base film 12, resulting in a significant reduction in the migration channels of active metal ions in the separator 1, thereby significantly increasing the internal resistance of the secondary battery and deteriorating the performance of the secondary battery, for example, affecting the cycle performance of the secondary battery and increasing production costs. Therefore, setting the mass of the ion capture agent per unit area of ​​the separator 1 within an appropriate range is beneficial to improving the performance of the secondary battery.

[0078] Optionally, in some embodiments, the mass proportion of the ion capture agent in the coating 11 is 50% to 99%. Optionally, the mass proportion of the ion capture agent in the coating 11 is 80% to 98%.

[0079] Specifically, the mass proportion of the ion capture agent in the coating 11 can be 50%, 60%, 70%, 80%, 90%, 95%, 98%, 99%, or a value between any two of the above values.

[0080] The mass ratio of the ion capture agent in the coating 11 is within the given range, and the ion capture agent can play a good role in reducing transition metal ions, thereby further improving the cycle performance of the battery.

[0081] Optionally, in some embodiments, the first base film and the second base film each independently include at least one of polyolefins and their derivatives, halogenated polyolefins and their derivatives, polyethers and their derivatives, polyetheretherketones and their derivatives, polyesters and their derivatives, polyimides and their derivatives, and polyvinyl alcohols and their derivatives; optionally, the halogenated polyolefins and their derivatives include at least one of polytetrafluoroethylene and their derivatives, polyvinyl fluoride and their derivatives, and polyvinylidene fluoride and their derivatives; optionally, the polyesters and their derivatives include at least one of polyethylene terephthalate and its derivatives, and polybutylene terephthalate and its derivatives.

[0082] Optionally, in some embodiments, the coating further comprises a binder; optionally, the binder comprises at least one of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, or cyanoethyl pullulan.

[0083] The ion capture agent in the coating layer can be bonded to the first base film and the second base film through the adhesive, so that there is good bonding force between the ion capture agent and the first base film and the second base film, thereby improving the overall structural strength of the isolation membrane.

[0084] Optionally, in some embodiments, the coating further comprises a filler; optionally, the filler comprises at least one of inorganic particles, organic particles, or an organic-metal framework material.

[0085] Alternatively, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or greater or inorganic particles having ion conductivity but not storing ions.

[0086] Optionally, the organic particles include at least one of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifier, melamine resin, phenolic resin, polyester, silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, or a copolymer of butyl acrylate and ethyl methacrylate.

[0087] Optionally, the organic-metal framework material includes at least one of a nitrogen-containing heterocyclic ligand building structure, an organic carboxylic acid ligand building structure, and a nitrogen-oxygen mixed ligand building structure.

[0088] Unless otherwise specified, all raw materials used in the separator (eg, the first base film, the second base film, the adhesive, the filler, etc.) can be purchased commercially.

[0089] [Method for preparing isolation film]

[0090] FIG2 is a diagram illustrating a method for preparing an isolation film according to an embodiment of the present application. As shown in FIG2 , the method 200 includes the following steps.

[0091] Step 210: providing a first base film and a second base film.

[0092] Step 220 , providing a coating slurry.

[0093] The coating slurry includes an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V.

[0094] In step 230 , a coating slurry is applied on the first base film and / or the second base film.

[0095] In step 240 , the first base film and the second base film are compounded to obtain an isolation film.

[0096] The separator prepared by the above method can improve the cycle performance of a secondary battery when applied to the secondary battery.

[0097] [Positive electrode]

[0098] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0099] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0100] 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.).

[0101] In some embodiments, the positive electrode active material may be a positive electrode active material for lithium ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for lithium ion batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] [Negative electrode]

[0106] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0107] 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.

[0108] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper 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, 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.).

[0109] 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.

[0110] In some embodiments, the negative electrode film layer may further include a binder. The binder may include 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).

[0111] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0112] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0113] 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.

[0114] [Electrolytes]

[0115] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0116] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0117] 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0118] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0119] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0120] 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.

[0121] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0122] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0123] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG3 shows a battery cell 30 having a square structure as an example.

[0124] In some embodiments, referring to Figure 4, the outer packaging may include a shell 31 and a cover plate 33. The shell 31 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 31 has an opening connected to the receiving cavity, and the cover plate 33 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 32 through a winding process or a lamination process. The electrode assembly 32 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 32. The number of electrode assemblies 32 contained in the battery cell 30 can be one or more, and those skilled in the art can select according to specific actual needs.

[0125] In some embodiments, the battery 40 may include multiple battery cells 30. For example, FIG5 is a schematic diagram of the structure of a battery 40 according to one embodiment of the present application. The battery 40 may include multiple battery cells 30. The battery 40 may also include a housing 41 having a hollow interior and housing the multiple battery cells 30. For example, the multiple battery cells 30 may be connected in parallel, in series, or in a mixed combination and then placed in the housing 41.

[0126] Optionally, the battery 40 may also include other structures, which will not be described in detail here. For example, the battery 40 may also include a busbar component, which is used to achieve electrical connection between multiple battery cells 30, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component can achieve electrical connection between the battery cells 30 by connecting the electrode terminals of the battery cells 30. Furthermore, the busbar component can be fixed to the electrode terminals of the battery cells 30 by welding. The electrical energy of the multiple battery cells 30 can be further led out through the box 41 through a conductive mechanism. Optionally, the conductive mechanism may also belong to the busbar component.

[0127] The number of battery cells 30 can be set to any value based on different power requirements. Multiple battery cells 30 can be connected in series, parallel, or in a hybrid manner to achieve higher capacity or power. Since each battery 40 may include a large number of battery cells 30, for ease of installation, the battery cells 30 can be grouped, with each group of battery cells 30 forming a battery module. The number of battery cells 30 included in a battery module is not limited and can be set according to requirements. A battery can include multiple battery modules, which can be connected in series, parallel, or in a hybrid manner.

[0128] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules or batteries provided in the present application. The battery cells, battery modules or batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of 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 are not limited thereto.

[0129] As the electrical device, a battery cell, a battery module or a battery can be selected according to its usage requirements.

[0130] 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 battery cell, a battery or battery module can be used.

[0131] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0132] [Example]

[0133] 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.

[0134] 1. Preparation of isolation film

[0135] Isolation film 1:

[0136] A first base film is provided, wherein the material includes polypropylene (PP) and the thickness is 9 μm.

[0137] A second base film is provided, wherein the material includes polyethylene (PE) and the thickness is 7 μm.

[0138] Provide coating slurry: add ion capture agent Li7Ti5O 12 The binder polyvinylidene fluoride (PVDF) is dissolved in the solvent N-methylpyrrolidone (NMP) in a mass ratio of 90%:10%, and the mixture is stirred and mixed thoroughly to obtain a coating slurry; the coating slurry is then evenly coated on a PE base film to form a coating, and the PP base film and the PE base film are composited so that the coating is between the PP base film and the PE base film, and then dried to prepare an isolation membrane 1. The mass of the ion capture agent per unit area of ​​the prepared isolation membrane 1 is 4.8 g / m 2 .

[0139] Isolation membrane 2: The preparation of isolation membrane 2 is similar to that of isolation membrane 1, except that the mass of ion capture agent per unit area of ​​isolation membrane 2 is 0.12 g / m 2 .

[0140] Isolation membrane 3: The preparation of isolation membrane 3 is similar to that of isolation membrane 1, except that the mass of ion capture agent per unit area of ​​isolation membrane 3 is 0.48 g / m 2 .

[0141] Isolation membrane 4: The preparation of isolation membrane 4 is similar to that of isolation membrane 1, except that the mass of ion capture agent per unit area of ​​isolation membrane 4 is 12 g / m 2 .

[0142] Isolation membrane 5: The preparation of isolation membrane 5 is similar to that of isolation membrane 1, except that the mass of ion capture agent per unit area of ​​isolation membrane 5 is 24 g / m 2 .

[0143] Isolation film 6: The preparation of isolation film 6 is similar to that of isolation film 1. The difference is that in the preparation process of isolation film 6, the ion capture agent Li7Ti5O in the coating slurry is 12, the mass ratio of binder PVDF is 50%:50%.

[0144] Isolation film 7: The preparation of isolation film 7 is similar to that of isolation film 1. The difference is that in the preparation process of isolation film 7, the ion capture agent Li7Ti5O in the coating slurry is 12 , the mass ratio of binder PVDF is 80%:20%.

[0145] Isolation film 8: The preparation of isolation film 8 is similar to that of isolation film 1. The difference is that in the preparation process of isolation film 8, the ion capture agent Li7Ti5O in the coating slurry is 12 , the mass ratio of binder PVDF is 98%:2%.

[0146] Isolation film 9: The preparation of isolation film 9 is similar to that of isolation film 1. The difference is that in the preparation process of isolation film 9, the ion capture agent Li7Ti5O in the coating slurry is 12 , the mass ratio of binder PVDF is 99%:1%.

[0147] Isolation film 10: The preparation of isolation film 10 is similar to that of isolation film 1. The difference is that in the preparation process of isolation film 10, the ion capture agent Li7Ti5O in the coating slurry is 12 , the mass ratio of binder PVDF is 40%:60%.

[0148] Isolation membrane 11: The preparation of isolation membrane 11 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 11 is Na7Ti5O 12 .

[0149] Separator 12: The preparation of separator 12 is similar to that of separator 1, except that the ion capture agent in the coating of separator 12 is Li powder.

[0150] Isolation membrane 13: The preparation of isolation membrane 13 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 13 is Al powder.

[0151] Isolation membrane 14: The preparation of isolation membrane 14 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 14 is Li 1 / 6 C.

[0152] Isolation membrane 15: The preparation of isolation membrane 15 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 15 is Li 4.4 Si.

[0153] Separator 16: The preparation of separator 16 is similar to that of separator 1, except that the ion capture agent in the coating of separator 16 is n-butyl lithium.

[0154] Isolation membrane 17: The preparation of isolation membrane 17 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 17 is naphthyl lithium.

[0155] Isolation membrane 18: The preparation of isolation membrane 18 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 18 is

[0156] Isolation membrane 19: The preparation of isolation membrane 19 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 19 is

[0157] Isolation membrane 20: The preparation of isolation membrane 20 is similar to that of isolation membrane 1, except that the ion capture agent in the coating of isolation membrane 20 is

[0158] Isolation membrane 21: The preparation of isolation membrane 21 is similar to that of isolation membrane 1, except that the coating of isolation membrane 21 contains inorganic Al2O3 ceramic particles, wherein the ion capture agent Li7Ti5O 12 The mass ratio of inorganic Al2O3 ceramic particles and binder PVDF is 50%:40%:10%.

[0159] Separator 22: The preparation of separator 22 is similar to that of separator 1, except that the coating of separator 22 contains only the binder PVDF and does not contain an ion capture agent.

[0160] 2. Preparation of secondary batteries

[0161] [Example 1]

[0162] (1) Preparation of positive electrode sheet

[0163] Positive electrode sheet: The positive electrode active material lithium manganate (LiMn2O4), the conductive agent acetylene black, and the binder PVDF are dissolved in the solvent NMP in a mass ratio of 90%:5%:5%, and after being fully stirred and mixed, they are coated on Al foil, dried, and cold pressed to obtain the positive electrode sheet.

[0164] (2) Preparation of negative electrode sheet

[0165] The negative electrode active material artificial graphite, the conductive agent acetylene black, and the binder PVDF were fully stirred and mixed in an N-methylpyrrolidone solvent system in a mass ratio of 90%:5%:5%, and then coated on a Cu foil, dried, and cold pressed to obtain a negative electrode sheet.

[0166] (3) Isolation film

[0167] The isolation film used was the isolation film 1 prepared above.

[0168] (4) Preparation of electrolyte

[0169] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30%:70%, and 1M lithium hexafluorophosphate (LiPF6) electrolyte salt was dissolved therein to obtain an electrolyte solution.

[0170] (5) Assembly of secondary batteries

[0171] The above-mentioned positive electrode sheet, separator 1, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in a battery case, dried, and then injected with electrolyte, and then subjected to processes such as formation and standing to obtain a lithium-ion secondary battery 1, which is Example 1.

[0172] [Examples 2-21, Comparative Example 1]

[0173] The preparation methods of the secondary batteries of Examples 2-21 and Comparative Example 1 are similar to that of the secondary battery of Example 1, except that different isolation membranes are used (Examples 1-21 respectively use isolation membranes 1-21, and Comparative Example 1 uses isolation membrane 22). See Table 1 for details.

[0174] [Examples 22-25]

[0175] The preparation methods of the secondary batteries of Examples 22-25 are similar to those of the secondary battery of Example 1, except that different positive electrode sheets are used. The types of positive electrode active materials in the positive electrode sheets used in Examples 22-25 are lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNiO2), and lithium nickel cobalt manganese oxide (LiNiO2). 0.8 Co 0.1 Mn 0.1 O2), and lithium iron phosphate (LiFePO4), see Table 2-5 for details.

[0176] [Comparative Examples 2-5]

[0177] The preparation methods of the secondary batteries of Comparative Examples 2-5 are similar to those of the secondary batteries of the above-mentioned embodiments. The difference is that the separator 22 is used in Comparative Examples 2-5, and the types of positive electrode active materials in the positive electrode sheets used in Comparative Examples 2-5 are lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt manganese oxide (LiNiO2), and lithium nickel cobalt manganese oxide (LiNiO2). 0.8 Co 0.1 Mn 0.1 O2), and lithium iron phosphate (LiFePO4), see Table 2-5 for details.

[0178] Next, the battery performance testing process is described.

[0179] 3. Battery performance test

[0180] (1) Battery capacity retention test

[0181] At 45°C, charge a lithium-ion secondary battery at a constant current of 1C to the upper voltage limit, then charge it at a constant voltage at the upper voltage limit until the current is less than 0.05C. Then discharge it at a constant current of 1C to the lower voltage limit. This charge and discharge cycle is considered one cycle. Repeat this cycle, and calculate the capacity retention of the lithium-ion secondary battery after 500 cycles.

[0182] The capacity retention rate (%) of the lithium ion secondary battery after 500 cycles at 45° C. = (discharge capacity at the 500th cycle / discharge capacity at the first cycle)×100%.

[0183] (2) Negative electrode transition metal content test after 500 cycles at 45°C

[0184] The lithium-ion secondary battery after 500 cycles at 45°C was disassembled, the negative electrode was removed, and the total content of transition metals (such as Ni, Co, Mn or Fe) on the negative electrode was tested using inductively coupled plasma atomic emission spectrometry in accordance with EPA 6010D-2014.

[0185] The upper and lower limits of the voltage for the above lithium manganese oxide system are 3 to 4.3V; the upper and lower limits of the voltage for the lithium cobalt oxide system are 2.6 to 4.2V; the upper and lower limits of the voltage for the lithium nickel oxide system are 2.5 to 4.2V; the upper and lower limits of the voltage for the lithium nickel cobalt manganese oxide system are 2.8 to 4.25V; and the upper and lower limits of the voltage for the lithium iron phosphate system are 2 to 3.65V.

[0186] The battery performance tests of Comparative Examples 1-5 and Examples 1-25 prepared according to the above method were performed, and the results are shown in Tables 1-5.

[0187] Table 1: Product parameters and performance test results of Comparative Example 1 and Examples 1-21

[0188] From the comparison of the results of Comparative Example 1 and Examples 1-21, it can be seen that the ion capture agent included in the separator improves the cycle performance of the corresponding lithium manganese oxide battery and significantly reduces the transition metal content on the negative electrode. 12 、Na7Ti5O 12 , Metal Li (powder), Metal Al (powder), Li 1 / 6 C. Li 4.4 Si, n-butyllithium, naphthyllithium, When added to lithium manganese oxide batteries respectively, the cycle performance of lithium manganese oxide batteries is significantly improved, and the transition metal content on the negative electrode plate is also significantly reduced.

[0189] From the comparison of the results of Examples 1-5, it can be seen that within a certain range, the greater the mass of the ion capture agent per unit area of ​​the separator, the greater the improvement in the cycle performance of the lithium manganese oxide battery. Beyond a certain range, as the mass of the ion capture agent per unit area of ​​the separator increases, the cycle performance of the lithium manganese oxide battery no longer improves significantly. In the embodiment of the present application, under the same other conditions, the mass of the ion capture agent per unit area of ​​the separator is 0.48g / m 2 ~12g / m 2 Within this range, the cycle performance of lithium manganese oxide batteries is better.

[0190] From the comparison of the results of Examples 1, 6-10, it can be seen that within a certain range, the greater the mass proportion of the ion capture agent in the coating, the greater the improvement in the cycle performance of the lithium manganese oxide battery. Beyond a certain range, as the mass proportion of the ion capture agent in the coating increases, the cycle performance of the lithium manganese oxide battery no longer improves significantly. In the embodiments of the present application, under the same other conditions, the cycle performance of the lithium manganese oxide battery is better when the mass proportion of the ion capture agent in the coating is in the range of 50% to 99%.

[0191] Table 2: Product parameters and performance test results of Comparative Example 2 and Example 22

[0192] From the comparison of the results of Comparative Example 2 and Example 22, it can be seen that the ion capture agent Li7Ti5O 12 The cycle performance of the lithium cobalt oxide battery has been improved, and the transition metal content on the negative electrode has been significantly reduced.

[0193] Table 3: Product parameters and performance test results of Comparative Example 3 and Example 23

[0194] From the comparison of the results of Comparative Example 3 and Example 23, it can be seen that the ion capture agent Li7Ti5O 12 The cycle performance of the lithium nickel oxide battery has been improved, and the transition metal content on the negative electrode has been significantly reduced.

[0195] Table 4: Product parameters and performance test results of Comparative Example 4 and Example 24

[0196] From the comparison of the results of Comparative Example 4 and Example 24, it can be seen that the ion capture agent Li7Ti5O 12 The cycle performance of the nickel cobalt manganese oxide battery has been improved, and the transition metal content on the negative electrode has been significantly reduced.

[0197] Table 5: Product parameters and performance test results of Comparative Example 5 and Example 25

[0198] From the comparison of the results of Comparative Example 5 and Example 25, it can be seen that the ion capture agent Li7Ti5O 12 The cycle performance of the lithium iron phosphate battery has been improved, and the transition metal content on the negative electrode has been significantly reduced.

[0199] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A separation film, comprising: A first base film, a coating layer and a second base film, wherein the coating layer is disposed between the first base film and the second base film, the coating layer comprises an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V.

2. The isolation film according to claim 1, wherein: The ion capture agent includes at least one of active metal and alkali metal compounds; Optionally, the active metal includes at least one of Li, Na, K, Rb, Cs, Fr, Mg, Ca, Sr, Ba, Al, Ti or V. Optionally, the active metal includes at least one of Li, Na, Mg, Al, Ti or V. Optionally, the alkali metal compound comprises A 1 x B. A 2 y Ti5O 12 , at least one of the compounds represented by formula (I), formula (II) or formula (III): Among them, A 1 , A 2 , A 3 , A 4 , A 5 , A 6 Each independently includes at least one of Li, Na, or K, B includes C, Si, or Sn, x≥0.05, y>4, R, R1, R2, R3, and R4 each independently include a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 2 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an alkenyl group having 6 to 8 carbon atoms, The present invention further comprises at least one of an aryl group having 6 to 26 carbon atoms, an aryl group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carboxyl group having 1 to 20 carbon atoms, a carboxyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, a carbonyl group having 1 to 20 carbon atoms, a carbonyl group having 1 to 20 carbon atoms substituted by a sulfonic acid group or a sulfonyl group, an aryloxy group having 6 to 26 carbon atoms, and an aryloxy group having 6 to 26 carbon atoms substituted by a sulfonic acid group or a sulfonyl group.

3. The isolation film according to claim 2, wherein: The A 1 x B includes Li 1 / 6 C. Na 1 / 6 C.K 1 / 8 C. Li 4.4 Si or Li 4.4 At least one of Sn.

4. The isolation film according to claim 2 or 3, wherein: 5≤y≤7; Optionally, the A 2 y Ti5O 12 Including Li7Ti5O 12 or Na7Ti5O 12 At least one of .

5. The separator according to any one of claims 2 to 4, wherein: The compound represented by formula (I) includes at least one of n-butyllithium, naphthyllithium or biphenyllithium.

6. The separator according to any one of claims 2 to 5, wherein: The compounds represented by formula (II) include At least one of .

7. The separator according to any one of claims 2 to 6, wherein: The compounds represented by formula (III) include At least one of .

8. The separator according to any one of claims 1 to 7, wherein: The mass of the ion capture agent per unit area of ​​the isolation membrane is 0.12 g / m 2 ~24g / m 2 Optionally, the mass of the ion capture agent per unit area of ​​the isolation membrane is 0.48 g / m 2 ~12g / m 2 .

9. The separator according to any one of claims 1 to 8, wherein: The mass proportion of the ion capture agent in the coating is 50% to 99%. Optionally, the mass proportion of the ion capture agent in the coating is 80% to 98%.

10. The separator according to any one of claims 1 to 9, wherein: The first base film and the second base film each independently include at least one of polyolefins and derivatives thereof, halogenated polyolefins and derivatives thereof, polyethers and derivatives thereof, polyetheretherketones and derivatives thereof, polyesters and derivatives thereof, polyimides and derivatives thereof, and polyvinyl alcohols and derivatives thereof; Optionally, the halogenated polyolefin and its derivatives include at least one of polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, polyvinylidene fluoride and its derivatives; Optionally, the polyester and its derivatives include at least one of polyethylene terephthalate and its derivatives, polybutylene terephthalate and its derivatives.

11. The separator according to any one of claims 1 to 10, wherein: The coating also includes a binder; Optionally, the binder includes at least one of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinyl pyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, or cyanoethyl pullulan.

12. The separator according to any one of claims 1 to 11, wherein: The coating further comprises a filler; Optionally, the filler includes at least one of inorganic particles, organic particles, or organic-metal framework materials; Optionally, the inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or more or inorganic particles having ion conductivity but not storing ions; Optionally, the organic particles include at least one of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifier, melamine resin, phenolic resin, polyester, silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, or a copolymer of butyl acrylate and ethyl methacrylate; Optionally, the organic-metal framework material includes at least one of a nitrogen-containing heterocyclic ligand building structure, an organic carboxylic acid ligand building structure, and a nitrogen-oxygen mixed ligand building structure.

13. A method for preparing an isolation film, comprising: providing a first base film and a second base film; Providing a coating slurry, wherein the coating slurry includes an ion capture agent, and the reduction potential of the ion capture agent relative to lithium metal is 0 to 2V; Applying the coating slurry on the first base film and / or the second base film; The first base film and the second base film are compounded to obtain an isolation film. 14 . A secondary battery comprising the separator according to claim 1 .

15. An electric device comprising the secondary battery according to claim 14.

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