Secondary battery and electric device

Abstract

The invention provides a secondary battery, the secondary battery comprises a positive pole piece, the positive pole piece comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprises a softening agent, and the softening agent comprises an acrylate polymer. The acrylate polymer comprises a large number of ester groups, and the ester groups have good compatibility with the surface of the positive electrode active material, so that the coating of the acrylate polymer on the surface of the positive electrode active material is facilitated. The acrylic polymer coating the surface of the positive electrode active material can improve the sliding capacity of the positive electrode active material in the cold pressing process through the flexibility of the acrylic polymer, and reduce the damage to the surface of a current collector and the stretching degree in the cold pressing process, so that the achievable limit compaction density of the pole piece is improved on the premise of not sacrificing the safety of the pole piece; the energy density of the battery is improved.

Description

Technical Field

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

[0002] 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 electrochemical performance, such as energy density. Summary of the Invention

[0003] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a secondary battery having a high packing density and an energy density.

[0004] In a first aspect, the present application provides a secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, the positive electrode film layer comprising a softener, and the softener comprising an acrylic polymer.

[0005] Acrylate polymers contain a large number of ester groups, which have good compatibility with the surface of positive electrode active materials, facilitating their coating. Acrylate polymers coated on the surface of positive electrode active materials can reduce sedimentation and agglomeration of the positive electrode active materials in the slurry, increasing the slurry's maximum solids content. Furthermore, their flexibility improves the slippage of the positive electrode active materials during cold pressing, reducing damage and stretching of the current collector during cold pressing. This increases the achievable ultimate compaction density of the electrode without sacrificing electrode safety, thereby improving the battery's energy density.

[0006] In any embodiment, the side chain of the acrylic polymer contains a polyether segment.

[0007] Polyether segments contain a large number of carbon-oxygen single bonds, which are more prone to internal rotation than carbon-carbon single bonds. This makes acrylic polymers containing polyether segments on the side chains more flexible, which can further increase the ultimate compaction density of the electrode and improve the energy density of the battery. At the same time, the polyether segments have high polarity and are highly compatible with positive electrode active materials. The main chain of acrylic ester polymers has low polarity and high compatibility with organic solvents. Therefore, the amphiphilic nature of the polymer not only increases flexibility but also plays a dispersing role, further increasing the solid content of the slurry, optimizing the electrode preparation process, and improving the electrode preparation efficiency.

[0008] In any embodiment, the acrylic polymer includes a structural unit derived from an acrylic acid ester monomer and a structural unit derived from an acrylic acid ester monomer containing a polyether segment.

[0009] In any embodiment, the acrylate monomer containing a polyether segment comprises a structure shown in Formula I,

[0010]

[0011] wherein R1, R2, and R3 are each independently hydrogen, substituted or unsubstituted C 1-5 Alkyl, R4 including C 1-5 Alkylene, n is 10-50.

[0012] In any embodiment, R1, R2, and R3 each independently include at least one of hydrogen, methyl, and ethyl, R4 includes at least one of methylene, ethylene, and propylene, and n is 15-40.

[0013] In any embodiment, the acrylate monomer comprises a structure shown in Formula II,

[0014]

[0015] wherein R5, R6, and R7 are each independently hydrogen or substituted or unsubstituted C 1-5 Alkyl, R8 includes C 1-5 alkyl.

[0016] In any embodiment, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0017] In any embodiment, the end groups of the polyether segments include residues of silane coupling agents.

[0018] Silane coupling agents are organosilicon monomers with two or more different reactive groups within their molecules. They can chemically bond or couple with organic and inorganic materials, increasing the adhesion between the two materials. Silane coupling agents readily undergo hydrolysis reactions with polyether segments. The portion of the silane coupling agent bonded to the polyether segments after the reaction is called the silane coupling agent residue. The silane coupling agent residue in the flexibilizer can further hydrolyze with the hydroxyl groups on the surface of the positive electrode active material and / or the positive electrode current collector, forming covalent bonds. This effectively improves both the cohesion of the positive electrode film and the adhesion between the positive electrode film and the positive electrode current collector.

[0019] In any embodiment, the silane coupling agent comprises a structure represented by formula III,

[0020] YSiX3 formula Ⅲ

[0021] Where X includes C 1-5 One or more of alkoxy, aryloxy, chloro, Y includes C 1-5 Alkyl, C 2-5 One or more of alkenyl, amino, epoxy, mercapto, and acryloyloxy.

[0022] The X group in the silane coupling agent can undergo a hydrolysis reaction with the terminal hydroxyl groups of the polyether chain segments on the acrylic polymer, causing the acrylic polymer to dehydrogenate and chemically react with the silicon atoms in the silane coupling agent to form silicon-oxygen bonds. During the slurry mixing process, the X group in the flexibilizer can continue to undergo a hydrolysis reaction with the hydroxyl groups on the surface of the positive electrode active material and / or the positive electrode current collector, forming a covalent bond, which effectively improves the cohesive force of the positive electrode film layer and the adhesion between the positive electrode film layer and the positive electrode current collector.

[0023] The addition of a flexibilizer to the positive electrode film often means a decrease in the binder content in the positive electrode film, which in turn results in an increase in electrode flexibility at the expense of adhesion performance. Unlike flexibilizers in the prior art, the embodiments of this application improve electrode flexibility and increase electrode compaction density while also enhancing electrode adhesion, thus balancing the overall performance of battery energy density and cycling stability.

[0024] In any embodiment, the silane coupling agent includes one or more of methyltrimethoxysilane, methyltriethoxysilane, diethoxydiaminosilane, and vinyltriethoxysilane.

[0025] In any embodiment, the molar ratio of the structural unit derived from acrylic acid ester to the structural unit derived from acrylic acid ester containing a polyether segment is 1:1-10:1, and can be optionally 1:1-5:1.

[0026] The molar ratio of the structural units derived from acrylate to the structural units derived from acrylate containing a polyether segment within the above range can effectively increase the ultimate compaction density while taking into account the manufacturing cost.

[0027] In any embodiment, the ratio of the residual mass of the silane coupling agent to the total mass of the structural units of the acrylic polymer is 1:500-1:10, and can be optionally 1:200-1:50.

[0028] The ratio of the residual mass of the silane coupling agent to the total mass of the structural units of the acrylic polymer within the above range can not only effectively improve the bonding strength of the electrode, but also minimize the influence of the silicon base on the electrochemical stability of the electrode.

[0029] In any embodiment, the weight average molecular weight of the acrylic polymer is 500,000 to 3,000,000.

[0030] In any embodiment, the weight average molecular weight of the acrylic polymer is 1 million to 2 million.

[0031] Acrylate polymers with a weight average molecular weight within the above range can simultaneously achieve the functions of softening, dispersing and bonding, thereby comprehensively improving the electrochemical performance of secondary batteries.

[0032] In any embodiment, based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.1%-1.0%.

[0033] In any embodiment, based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.2%-0.5%.

[0034] The positive electrode film layer with the softener proportion within the above range can simultaneously take into account the effects of softening, dispersion and bonding, and comprehensively improve the electrochemical performance of the secondary battery.

[0035] In any embodiment, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered metal oxide. Optionally, the composition of the layered metal oxide is as shown in Formula IV:

[0036] Na x Mn a Fe b Ni c O2 Formula IV

[0037] Among them, 0.66≤x≤1, 0<a≤0.70, 0<b≤0.70, 0<c≤0.23.

[0038] The layered metal oxide has a high voltage window, which is conducive to further improving the energy density of the battery.

[0039] In any embodiment, the ultimate compaction density of the positive electrode film is greater than or equal to 2.9 g / cm 3 .

[0040] The high ultimate compaction density of the positive electrode film layer is conducive to further improving the battery energy density.

[0041] In any embodiment, the secondary battery is a sodium secondary battery.

[0042] A second aspect of the present application provides an electrical device comprising the secondary battery of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic diagram of a secondary battery according to one embodiment of the present application;

[0044] Figure 2 yes Figure 1An exploded view of a secondary battery according to an embodiment of the present application is shown;

[0045] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0046] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0047] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0048] Figure 6 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0049] Description of reference numerals:

[0050] 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

[0051] 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.

[0052] " 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.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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).

[0058] Increasing the compaction density of battery electrodes helps boost the energy density of secondary batteries. However, during the cold pressing process, the surface damage and stretching of the current collector caused by the compaction of active materials in the electrode film increases significantly with increasing compaction density. Consequently, electrodes with high compaction density are often more susceptible to brittle fracture, leading to battery failure. How to increase the compaction density of electrode electrodes while ensuring battery safety is a pressing technical challenge for those skilled in the art.

[0059] [Secondary battery]

[0060] Based on this, the present application proposes a sodium secondary battery, which includes a positive electrode plate, the positive electrode plate includes a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, the positive electrode film layer includes a softener, and the softener includes an acrylic polymer.

[0061] Herein, the positive electrode also refers to the cathode in a secondary battery.

[0062] Herein, the positive current collector refers to any conductive substrate capable of conducting current to the positive electrode during discharge or charge of a secondary battery.

[0063] In this article, the positive electrode film layer refers to the coating formed after the positive electrode slurry is applied and dried.

[0064] In this article, the softener refers to an additive that can improve the flexibility of the positive electrode.

[0065] Acrylate polymers refer to polymers produced by homopolymerization of acrylate monomers or copolymerization with other organic monomers. These can be homopolymers or copolymers. Polymers include, on the one hand, chemically homogeneous aggregates of macromolecules produced by polymerization reactions, but varying in degree of polymerization, molar mass, and chain length. The term also includes derivatives of such aggregates of macromolecules formed by polymerization reactions, i.e., compounds or mixtures that can be obtained by reactions of functional groups in the aforementioned macromolecules, such as addition or substitution, and can be chemically homogeneous or chemically heterogeneous.

[0066] Acrylate refers to a general term for esters of acrylic acid and its homologues, and includes, by way of example, but not limited to, methyl acrylate, ethyl acrylate, methyl 2-methacrylate, and ethyl 2-methacrylate.

[0067] Acrylate polymers contain a large number of ester groups, which have good compatibility with the surface of positive electrode active materials, facilitating their coating. Acrylate polymers coated on the surface of positive electrode active materials can reduce sedimentation and agglomeration of the positive electrode active materials in the slurry, increasing the slurry's maximum solids content. Furthermore, their flexibility improves the slippage of the positive electrode active materials during cold pressing, reducing damage and stretching of the current collector during cold pressing. This increases the achievable ultimate compaction density of the electrode without sacrificing electrode safety, thereby improving the battery's energy density.

[0068] In some embodiments, the acrylic polymer contains a polyether segment on its side chain.

[0069] A polyether segment refers to an organic segment including an ether bond, and a segment refers to the smallest unit in a polymer chain that can move independently.

[0070] Polyether segments contain a large number of carbon-oxygen single bonds, which are more prone to internal rotation than carbon-carbon single bonds. This makes acrylic polymers containing polyether segments on the side chains more flexible, which can further increase the ultimate compaction density of the electrode and improve the energy density of the battery. At the same time, the polyether segments have high polarity and are highly compatible with positive electrode active materials. The main chain of acrylic ester polymers has low polarity and high compatibility with organic solvents. Therefore, the amphiphilic nature of the polymer not only increases flexibility but also plays a dispersing role, further increasing the solid content of the slurry, optimizing the electrode preparation process, and improving the electrode preparation efficiency.

[0071] In some embodiments, the acrylic polymer comprises structural units derived from acrylic acid ester monomers and structural units derived from acrylic acid ester monomers containing a polyether segment.

[0072] A structural unit refers to the combination of atoms that constitutes a polymer chain and determines how the polymer structure is connected in a certain way.

[0073] In some embodiments, the acrylate monomer containing a polyether segment comprises a structure shown in Formula I,

[0074]

[0075] wherein R1, R2, and R3 are each independently hydrogen, substituted or unsubstituted C 1-5 Alkyl, R4 including C 1-5 Alkylene, n is 10-50.

[0076] “C 1-5“Alkyl” refers to a monovalent hydrocarbon group having 1 to 5 carbon atoms. The monovalent hydrocarbon group may be unbranched or branched, and includes, by way of example, but is not limited to, methyl, ethyl, propyl, isopropyl, 2-methyl-1-propyl, 2-methyl-2-propyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, and the like.

[0077] “C 1-5 “Alkylene” refers to a divalent hydrocarbon group having 1 to 5 carbon atoms. The divalent hydrocarbon group may be unbranched or branched, and includes, by way of example, but is not limited to, 1,2-ethylene, 1,2-propylene, 1,3-propylene, 1,3-butylene, 1,4-butylene, 2-methyl-1,3-propylene, 1,1-dimethyl-1,2-ethylene, 1,4-pentylene, 1,5-pentylene, 2-methyl-1,4-butylene, 2,2-dimethyl-1,3-propylene, and the like.

[0078] The term "substituted" refers to a compound or chemical moiety in which at least one hydrogen atom is replaced by another chemical moiety. Examples of substituents include, but are not limited to, halogen, alkyl, alkenyl, alkynyl, aryl, heteroalkyl, heteroaryl, hydroxyl, alkoxy, amine, nitro, sulfhydryl, cyano, amide, carboxyl, cycloalkyl, and the like. These substituents may be further substituted with substituents selected from these groups. Unless otherwise indicated, all chemical groups disclosed herein may be substituted.

[0079] In some embodiments, n can be selected from 10, 15, 20, 25, 30, 35, 40, 45, 50, or any integer therebetween.

[0080] In some embodiments, R1, R2, and R3 each independently include at least one of hydrogen, methyl, and ethyl, R4 includes at least one of methylene, ethylene, and propylene, and n is 15-40.

[0081] In some embodiments, the acrylate monomer comprises a structure shown in Formula II,

[0082]

[0083] wherein R5, R6, and R7 are each independently hydrogen or substituted or unsubstituted C 1-5 Alkyl, R8 includes C 1-5 alkyl.

[0084] In some embodiments, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0085] In some embodiments, the end groups of the polyether segments include residues of silane coupling agents.

[0086] Silane coupling agents are organosilicon monomers with two or more different reactive groups within their molecules. They can chemically bond or couple with organic and inorganic materials, increasing the adhesion between the two materials. Silane coupling agents readily undergo hydrolysis reactions with polyether segments. The portion of the silane coupling agent bonded to the polyether segments after the reaction is called the silane coupling agent residue. The silane coupling agent residue in the flexibilizer can further hydrolyze with the hydroxyl groups on the surface of the positive electrode active material and / or the positive electrode current collector, forming covalent bonds. This effectively improves both the cohesion of the positive electrode film and the adhesion between the positive electrode film and the positive electrode current collector.

[0087] In some embodiments, the silane coupling agent comprises a structure represented by Formula III,

[0088] YSiX3 formula Ⅲ

[0089] Where X includes C 1-5 One or more of alkoxy, aryloxy, chloro, Y includes C 1-5 Alkyl, C 2-5 One or more of alkenyl, amino, epoxy, mercapto, and acryloyloxy.

[0090] In some embodiments, the silane coupling agent includes one or more of methyltrimethoxysilane, methyltriethoxysilane, diethoxydiaminosilane, and vinyltriethoxysilane.

[0091] The X group in the silane coupling agent can undergo a hydrolysis reaction with the terminal hydroxyl groups of the polyether chain segments on the acrylic polymer, causing the acrylic polymer to dehydrogenate and chemically react with the silicon atoms in the silane coupling agent to form silicon-oxygen bonds. The specific reaction process is shown below:

[0092]

[0093] Here, R'H represents an acrylic acid ester polymer.

[0094] During the slurry mixing process, the X group in the softener can continue to undergo hydrolysis reaction with the hydroxyl groups on the surface of the positive electrode active material and / or the positive electrode current collector to produce covalent bond connections, thereby effectively improving the cohesive force of the positive electrode film layer and the bonding force between the positive electrode film layer and the positive electrode current collector.

[0095] The addition of a flexibilizer to the positive electrode film often means a decrease in the binder content in the positive electrode film, which in turn results in an increase in electrode flexibility at the expense of adhesion performance. Unlike flexibilizers in the prior art, the embodiments of this application improve electrode flexibility and increase electrode compaction density while also enhancing electrode adhesion, thus balancing the overall performance of battery energy density and cycling stability.

[0096] In some embodiments, the molar ratio of the structural unit derived from acrylate to the structural unit derived from acrylate containing a polyether segment is 1:1-10:1, and can be optionally 1:1-5:1.

[0097] In some embodiments, the molar ratio of the structural units derived from acrylate to the structural units derived from acrylate containing a polyether segment can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any range therebetween.

[0098] The molar ratio of the structural units derived from acrylate to the structural units derived from acrylate containing a polyether segment within the above range can effectively increase the ultimate compaction density while taking into account the manufacturing cost.

[0099] In some embodiments, the ratio of the residual mass of the silane coupling agent to the total mass of the structural units of the acrylic polymer is 1:500, 1:400, 1:300, 1:200, 1:100, 1:90, 1:80, 1:70, 1:60, 1:50, 1:40, 1:30, 1:20, 1:10 or any range therebetween.

[0100] The ratio of the residual mass of the silane coupling agent to the total mass of the structural units of the acrylic polymer within the above range can not only effectively improve the bonding strength of the electrode, but also minimize the influence of the silicon base on the electrochemical stability of the electrode.

[0101] In some embodiments, the weight average molecular weight of the acrylic polymer is 500,000 to 3,000,000.

[0102] In some embodiments, the weight average molecular weight of the acrylic polymer is 1 million to 2 million.

[0103] As used herein, the term "weight average molecular weight" refers to the sum of the weight fractions of molecules of different molecular weights in a polymer multiplied by their corresponding molecular weights.

[0104] The weight-average molecular weight can be tested by any method in the art. As an example, a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141) is used. A polystyrene solution sample with a mass fraction of 3.0% is used as a reference, and a matching chromatographic column is selected (oily: Styragel HT5 DMF7.8*300mm+Styragel HT4). Use purified N-methylpyrrolidone (NMP) solvent to prepare a 3.0% polymer glue to be tested. The prepared solution is allowed to stand for one day for use. During the test, first use a syringe to draw tetrahydrofuran, rinse, and repeat several times. Then draw 5 ml of the experimental solution, expel the air in the syringe, and wipe the needle tip dry. Finally, slowly inject the sample solution into the injection port. Acquire the data after the reading stabilizes.

[0105] In some embodiments, the weight average molecular weight of the acrylic polymer can be selected to be 500,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, or any range therebetween.

[0106] Acrylate polymers with a weight average molecular weight within the above range can simultaneously achieve the functions of softening, dispersing and bonding, thereby comprehensively improving the electrochemical performance of secondary batteries.

[0107] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.1%-1.0%.

[0108] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.2%-0.5%.

[0109] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the softener can be selected to be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any numerical range therebetween.

[0110] The positive electrode film layer with the softener proportion within the above range can simultaneously take into account the effects of softening, dispersion and bonding, and comprehensively improve the electrochemical performance of the secondary battery.

[0111] In some embodiments, the positive electrode film layer includes a positive electrode active material.

[0112] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: Prussian blue analogs, 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 the positive electrode active material of the battery 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 analog 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.

[0113] In some embodiments, the positive electrode active material includes a layered metal oxide. Optionally, the composition of the layered metal oxide is as shown in Formula IV,

[0114] Na x Mn a Fe b Ni c O2 Formula IV

[0115] where 0.66 ≤ x ≤ 1, 0 < a ≤ 0.70, 0 < b ≤ 0.70, 0 < c ≤ 0.23.

[0116] This layered metal oxide has a high voltage window, which is beneficial to further improving the energy density of the battery.

[0117] In some embodiments, the ultimate compaction density of the positive electrode film layer is greater than or equal to 2.9 g / cm 3 .

[0118] The ultimate compacted density is measured by any known method. As an example, a single-sided film weighing 350 mg / 1540.25 mm 2 Cut the double-sided electrode into test specimens of 20mm*100mm size for later use. Bend the electrode, fold it in half and fix it, and use a 2kg rolling roller to roll it once to check whether the folded part of the electrode is light-transmissive or metal-leaking. If not, fold the electrode in half and fix it, and roll it again using the same method to check whether the folded part of the electrode is light-transmissive or metal-leaking. If it is not light-transmissive or metal-leaking after three times, increase the pressure and reduce the thickness of the electrode to increase the compaction density by 0.02g / cm 3 Repeat the test until the positive electrode sheet shows light transmission and metal leakage after being folded and rolled three times. The compaction density of the positive electrode sheet that shows no light transmission or metal leakage is taken as the maximum compaction density. The compaction density is the single-sided areal density of the positive electrode film layer divided by the single-sided thickness of the positive electrode film layer.

[0119] In some embodiments, the ultimate compaction density of the positive electrode film layer can be selected to be 2.9 g / cm 3 , 3g / cm 3 、3.1g / cm 3 、3.2g / cm 3 or any range of values between them.

[0120] The high ultimate compaction density of the positive electrode film layer is conducive to further improving the battery energy density.

[0121] In some embodiments, the bonding strength of the positive electrode film layer is greater than or equal to 19 N / m.

[0122] In some embodiments, the bonding strength of the positive electrode film layer is 19 N / m-40 N / m.

[0123] In some embodiments, the bonding strength of the positive electrode film layer may be selected as 19 N / m, 20 N / m, 21 N / m, 22 N / m, 23 N / m, 24 N / m, 25 N / m, 26 N / m, 27 N / m, 28 N / m, 29 N / m, 30 N / m, 31 N / m, 32 N / m, 33 N / m, 34 N / m, 35 N / m, 36 N / m, 37 N / m, 38 N / m, 39 N / m, 40 N / m or any range therebetween.

[0124] The bonding strength of the positive electrode film layer can be tested by any method known in the art. As an example, take a cold-pressed double-sided electrode, cut a sample with a width of 30mm and a length of 100-160mm with a blade, and stick a special double-sided tape on the steel plate. The tape is 20mm wide and 90-150mm long. Stick the positive electrode film layer of the electrode sample cut earlier on the double-sided tape, and then roll it three times in the same direction with a 2kg roller. Fix a paper tape with a width equal to the electrode and a length of 250mm on the electrode current collector and fix it with wrinkle glue. Turn on the power of the Sansi tensile testing machine (sensitivity is 1N), the indicator light is on, adjust the limit block to the appropriate position, and fix the end of the steel plate without the electrode with the lower clamp. Fold the paper tape upwards so that the angle between it and the steel plate is 90°, fix it with the upper clamp, and use the "up" and "down" buttons on the manual controller attached to the tensile testing machine to adjust the position of the upper clamp. Then perform the test and read the value. The force when the electrode is under force balance divided by the width of the tape is used as the bonding force of the electrode per unit length to characterize the bonding strength between the positive electrode film layer and the current collector.

[0125] 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.

[0126] 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.).

[0127] 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.

[0128] 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.

[0129] 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 the softener, 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.

[0130] [Negative electrode]

[0131] 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.

[0132] 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.

[0133] 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.).

[0134] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: hard carbon, artificial graphite, natural graphite, soft carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon 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.

[0135] 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).

[0136] 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.

[0137] In some embodiments, the negative electrode film layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0138] 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.

[0139] In some embodiments, the sodium secondary battery is a sodium metal battery.

[0140] Sodium metal batteries are secondary batteries made by pre-depositing sodium metal or its alloys on the negative electrode during the battery manufacturing process. Using sodium metal as the negative electrode active material creates a low potential, which helps increase the usable capacity of sodium secondary batteries within their usable voltage range.

[0141] In some embodiments, the sodium secondary battery is a negative electrode-less battery.

[0142] A negative electrode-free sodium secondary battery refers to a battery in which a negative electrode active material layer is not actively provided on the negative electrode side during the battery manufacturing process. For example, a sodium metal or carbonaceous active material layer is not provided on the negative electrode through a coating or deposition process to form a negative electrode active material layer during the battery manufacturing process. During the first charge, sodium ions gain electrons on the anode side, and metallic sodium is deposited on the current collector surface to form a sodium metal phase. During discharge, the metallic sodium can be converted into sodium ions and return to the positive electrode, achieving cyclic charge and discharge. Compared to other sodium secondary batteries, negative electrode-free sodium secondary batteries can achieve higher energy density due to the lack of a negative electrode active material layer.

[0143] In some embodiments, to improve battery performance, the negative electrode side of the negative electrode-free sodium secondary battery may be provided with some conventional substances that can be used as negative electrode active materials, such as carbonaceous materials, metal oxides, alloys, etc. Although these materials have a certain capacity, due to the small amount of these materials, they are not used as the main negative electrode active materials in the battery and are therefore not considered to form a negative electrode active material layer that plays a sodium intercalation role. The sodium secondary battery thus constructed can still be considered a negative electrode-free sodium secondary battery.

[0144] [Electrolyte]

[0145] In some embodiments, the secondary battery further includes an electrolyte.

[0146] In some embodiments, the electrolyte includes an electrolyte salt selected from at least one of NaPF6, NaBF4, NaN(SO2F)2(NaFSI), NaClO4, NaAsF6, NaB(C2O4)2(NaBOB), NaBF2(C2O4)(NaDFOB), NaN(SO2RF)2, and NaN(SO2F)(SO2RF), wherein RF is represented by C b F 2b+1 , b is an integer between 1 and 10, and can be optionally an integer between 1 and 3.

[0147] In some embodiments, the electrolyte salt is selected from one or more of NaPF6, NaN(SO2F)2, NaN(CF3SO2)2, NaB(C2O4)2, and NaBF2(C2O4). In some embodiments, the electrolyte salt is selected from one or more of NaPF6, NaN(SO2RF)2, and NaBF2(C2O4). In some embodiments, RF is -CF3, -C2F5, or -CF2CF2CF3.

[0148] In some embodiments, the electrolyte includes a solvent, and the solvent includes at least one of a chain carbonate, a chain carboxylate, a cyclic carbonic acid, an ether solvent, a sulfone solvent, and a nitrile solvent. In some embodiments, the chain carbonate includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and dibutyl carbonate. In some embodiments, the chain carbonate includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC). In some embodiments, the chain carboxylate includes at least one of methyl formate (MF), ethyl formate (EF), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA). In some embodiments, the linear carboxylic acid ester includes at least one of methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA). In some embodiments, the ether solvent includes at least one of dioxolane (DOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me-THF), tetrahydropyran (THP), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (DG), 1,2-diethoxyethane, and 1,2-dibutoxyethane.

[0149] [Isolation film]

[0150] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0151] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0152] 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.

[0153] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0154] 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.

[0155] In this application, the shape of the sodium secondary battery is not limited to cylindrical, square or other arbitrary shapes. For example, Figure 1 The sodium secondary battery 5 is a square structure as an example.

[0156] In some embodiments, reference Figure 2 The outer packaging 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 form 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 impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the sodium secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0157] In some embodiments, sodium secondary batteries can be assembled into a battery module. The number of sodium 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.

[0158] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of sodium secondary batteries 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. The plurality of sodium secondary batteries 5 can further be fixed by fasteners.

[0159] Optionally, the battery module 4 may further include a housing having a housing space, and the plurality of sodium secondary batteries 5 are housed in the housing space.

[0160] 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.

[0161] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0162] In addition, the present application also provides an electrical device, which includes at least one of the sodium secondary battery, battery module, or battery pack provided in the present application. The sodium secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical 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.

[0163] As an electrical device, a sodium secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0164] Figure 6 This is 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 sodium secondary batteries, a battery pack or battery module can be used.

[0165] 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 sodium secondary battery as a power source.

[0166] Example

[0167] 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.

[0168] 1. Preparation method

[0169] Example 1:

[0170] 1) Preparation of polymer

[0171] Step 1:

[0172] The equipment required to build the reaction vessel: a stirrer, a condenser, a constant pressure dropping funnel and a four-necked flask. The entire reaction process must be carried out under a nitrogen-protected atmosphere. First, add 150g of dispersant Mg(OH)2, adjust the pH to 7.5 with NaHCO3, add 60g of initiator azobisisobutyronitrile AIBN and 7000g of distilled water, heat in a water bath to 60°C, and stir and mix for 30 minutes. Then add 540g of monomers methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (OEGMA) in a molar ratio of 4:1, and react for 6 hours. After the reaction is completed, add a small amount of ethanol, stir to room temperature, filter, wash, and vacuum dry to obtain polyether-modified polyacrylate. Among them, the structural formula of poly(ethylene glycol) methacrylate is shown in Formula I:

[0173]

[0174] Wherein, R1 and R2 are H, R3 is methyl, R4 is ethylene, and n is 25.

[0175] Step 2:

[0176] At room temperature, add 500 g of the polyether-modified polyacrylate prepared in step 1 and 5 g of methyltriethoxysilane to a flask in a mass ratio of 100:1. After stirring thoroughly, heat to 90°C in a water bath and react for 5 hours. After the reaction is complete, cool to room temperature to obtain a polyester polymer with a molecular weight of 1.5 million.

[0177] The polyester polymer includes structural units derived from methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (OEGMA), methyltriethoxysilane undergoes a hydrolysis reaction with the H end group in the poly(ethylene glycol) methacrylate, and the residue of the methyltriethoxysilane is connected to the end of the polyether segment.

[0178] 2) Preparation of positive electrode slurry

[0179] Layered oxide positive electrode active material NaMn 0.34 Fe 0.33 Ni 0.33 O2, conductive agent carbon black, carbon nanotubes, PVDF binder, and the above-synthesized polyester polymer are mixed evenly in a mass ratio of 96.2:1.5:0.5:1.5:0.3, and then N-methylpyrrolidone (NMP) is added as a solvent. The mixture is stirred under the action of a vacuum mixer until the system becomes uniform to obtain a positive electrode slurry with a solid content of 65wt%.

[0180] 3) Preparation of positive electrode sheet

[0181] The positive electrode slurry was evenly coated on both surfaces of the aluminum foil with a thickness of 13 μm to obtain a single-sided film with a weight of 200 mg / 1540.25 mm 2 The electrode (excluding the substrate) was dried at 105° C. for 24 h and cold pressed to obtain the positive electrode.

[0182] 4) Preparation of negative electrode sheet

[0183] The negative electrode plate is a metal sodium plate.

[0184] 5) Preparation of electrolyte

[0185] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), equal volumes of ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain an organic solvent, and then NaClO4 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0186] 6) Isolation film

[0187] A porous polyethylene film was used as the separator.

[0188] 7) Preparation of batteries

[0189] The positive electrode sheet, separator, 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 layer. The prepared electrolyte is added to obtain the button battery of Example 1.

[0190] Example 2

[0191] Example 2 is substantially the same as Example 1, except that R1 in poly(ethylene glycol) methacrylate (OEGMA) is methyl, R2 is H, R3 is methyl, R4 is ethylene, and n is 25.

[0192] Example 3

[0193] Example 3 is substantially the same as Example 1, except that n in poly(ethylene glycol) methacrylate (OEGMA) is 35.

[0194] Example 4

[0195] Example 4 is substantially the same as Example 1, except that n in poly(ethylene glycol) methacrylate (OEGMA) is 50.

[0196] Example 5

[0197] Example 5 is substantially the same as Example 1, except that the molar ratio of methyl methacrylate (MMA) to poly(ethylene glycol) methacrylate (OEGMA) is 1:1.

[0198] Example 6

[0199] Example 6 is substantially the same as Example 1, except that the molar ratio of methyl methacrylate (MMA) to poly(ethylene glycol) methacrylate (OEGMA) is 5:1.

[0200] Example 7

[0201] Example 7 is substantially the same as Example 1, except that the mass ratio of methyltriethoxysilane to polyether-modified polyacrylate added in step 2 is 1:10.

[0202] Example 8

[0203] Example 8 is basically the same as Example 1, except that the mass ratio of methyltriethoxysilane and polyether-modified polyacrylate added in step 2 is 1:50.

[0204] Example 9

[0205] Example 9 is substantially the same as Example 1, except that the mass ratio of methyltriethoxysilane to polyether-modified polyacrylate added in step 2 is 1:200.

[0206] Example 10

[0207] Example 10 is substantially the same as Example 1, except that the preparation of the polymer does not include step 2.

[0208] Example 11

[0209] Example 11 is substantially the same as Example 10, except that in step 1, only methyl methacrylate monomer is added instead of poly(ethylene glycol) methacrylate.

[0210] Comparative Example 1

[0211] The method is basically the same as Example 1, except that no polymer is added to the preparation of the positive electrode slurry, and the PVDF binder content is increased to 1.8%.

[0212] 2. Performance Testing

[0213] 1. Maximum solid content of slurry

[0214] The maximum solid content of the positive electrode slurry refers to the maximum solid content of the slurry that meets the shipping viscosity between 4000 and 35000 mPa.s and does not gel after the slurry is left to stand for 24 hours. The slurry solid content test method is: take the slurry weight as m0, place it in the weight loss rate test instrument; evaporate the solvent of the slurry until the weight loss rate is less than 0.3%, and record the remaining weight as m1; solid content = m1 / m 0* 100%.

[0215] 3. Analysis of test results of various embodiments and comparative examples

[0216] 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.

[0217] Table 1

[0218]

[0219] Table 2

[0220]

[0221]

[0222] Comparison of the Examples and Comparative Examples demonstrates that the inclusion of an acrylic polymer flexibilizer in the positive electrode film layer can increase the maximum solids content of the slurry and improve the ultimate compaction density of the electrode. The inclusion of polyether segments in the side chains of the acrylic polymer further enhances electrode flexibility and improves the ultimate compaction density. The inclusion of silane coupling agent residues in the end groups of the polyether segments in the acrylic polymer further improves the bonding properties of the electrode.

[0223] 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, characterized in that: The secondary battery includes a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes a softener, which includes an acrylic polymer.

2. The secondary battery according to claim 1, wherein The side chain of the acrylic ester polymer contains a polyether segment. 3 . The secondary battery according to claim 1 , wherein the acrylic acid ester polymer comprises a structural unit derived from an acrylic acid ester monomer and a structural unit derived from an acrylic acid ester monomer containing a polyether segment.

4. The secondary battery according to claim 3, wherein The acrylate monomer containing a polyether segment includes a structure shown in Formula I, wherein R1, R2, and R3 are each independently hydrogen, substituted or unsubstituted C 1-5 Alkyl, R4 including C 1-5 Alkylene, n is 10-50.

5. The secondary battery according to claim 3 or 4, characterized in that: R1, R2, and R3 each independently include at least one of hydrogen, methyl, and ethyl; R4 includes at least one of methylene, ethylene, and propylene; and n is 15-40.

6. The secondary battery according to any one of claims 3 to 5, characterized in that The acrylate monomer includes the structure shown in Formula II, wherein R5, R6, and R7 are each independently hydrogen or substituted or unsubstituted C 1-5 Alkyl, R8 includes C 1-5 alkyl.

7. The secondary battery according to any one of claims 3 to 6, characterized in that The acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

8. The secondary battery according to any one of claims 2 to 7, characterized in that The end groups of the polyether segments include residues of silane coupling agents.

9. The secondary battery according to claim 8, characterized in that The silane coupling agent includes the structure shown in formula III, YSiX3 formula Ⅲ Where X includes C 1-5 One or more of alkoxy, aryloxy, chloro, Y includes C 1-5 Alkyl, C 2-5 One or more of alkenyl, amino, epoxy, mercapto, and acryloyloxy.

10. The secondary battery according to claim 8 or 9, characterized in that The silane coupling agent includes one or more of methyltrimethoxysilane, methyltriethoxysilane, diethoxydiaminosilane, and vinyltriethoxysilane.

11. The secondary battery according to any one of claims 3 to 10, characterized in that: The molar ratio of the structural unit derived from acrylic acid ester to the structural unit derived from acrylic acid ester containing a polyether segment is 1:1-10:

1.

12. The secondary battery according to any one of claims 3 to 11, characterized in that The ratio of the residual mass of the silane coupling agent to the total mass of the structural units of the acrylic polymer is 1:500-1:

10.

13. The secondary battery according to any one of claims 1 to 12, characterized in that: The weight average molecular weight of the acrylic polymer is 500,000-3,000,000.

14. The secondary battery according to any one of claims 1 to 13, characterized in that The weight average molecular weight of the acrylic polymer is 1 million to 2 million.

15. The secondary battery according to any one of claims 1 to 14, characterized in that Based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.1%-1.0%.

16. The secondary battery according to any one of claims 1 to 15, characterized in that Based on the total mass of the positive electrode film layer, the mass proportion of the softener is 0.2%-0.5%.

17. The secondary battery according to any one of claims 1 to 16, characterized in that: The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered metal oxide. The composition of the layered metal oxide is shown in Formula IV. Na x Mn a Fe b Ni c O2 formula Ⅳ Among them, 0.66≤x≤1, 0<a≤0.70, 0<b≤0.70, 0<c≤0.

23.

18. The secondary battery according to any one of claims 1 to 17, characterized in that The ultimate compaction density of the positive electrode film is greater than or equal to 2.9 g / cm 3 .

19. The secondary battery according to any one of claims 1 to 18, characterized in that The secondary battery is a sodium secondary battery.

20. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 18.

Images