Composite separator and sodium-ion battery

Abstract

This application discloses a composite separator and a sodium-ion battery, relating to the field of sodium-ion battery technology, and aims to solve the problem of poor cycle stability and safety performance of sodium-ion batteries caused by gas-generating side reactions resulting from the dissolution of the cathode material and oxygen release. The composite separator includes a substrate layer and a functional layer. The functional layer covers at least one surface of the substrate layer, wherein the material of the functional layer includes cyclic amine compounds.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, and more particularly to a composite separator and a sodium-ion battery. Background Technology

[0002] In sodium-ion batteries, when the interfacial stability between the positive electrode material and the electrolyte is poor, if the positive electrode material contains transition metal elements, these elements can dissolve from the positive electrode material and migrate to the negative electrode. This causes an increase in local impedance at the negative electrode, making it prone to side reactions such as sodium deposition and the generation of reducing gases (H2, alkanes, alkenes, etc.). Furthermore, the positive electrode material may also undergo oxygen release side reactions. Singlet oxygen / oxygen radicals have high reactivity and can cause side reactions that oxidize the electrolyte, generating oxidizing gases (such as carbon dioxide). These gas-generating side reactions reduce the cycle stability of sodium-ion batteries. Simultaneously, oxygen release side reactions also reduce the thermal stability of sodium-ion batteries, deteriorating their safety performance. Summary of the Invention

[0003] The purpose of this application is to provide a composite separator and a sodium-ion battery, which aims to solve the problem of poor cycle stability and safety performance of sodium-ion batteries caused by the dissolution of the positive electrode material and the gasification side reaction caused by oxygen release.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] In a first aspect, this application provides a composite membrane, comprising: a base layer and a functional layer.

[0006] A functional layer is coated on at least one surface of the substrate layer, wherein the material of the functional layer includes cyclic amine compounds.

[0007] In the composite separator provided in this application embodiment, the cyclic amine compounds in the functional layer have the ability to adsorb singlet oxygen / reactive oxygen free radicals. By adsorbing singlet oxygen / reactive oxygen free radicals through cyclic amine compounds, the oxidative decomposition of the electrolyte can be effectively suppressed, thereby reducing the generation of oxidizing gases and improving the cycle stability of the sodium-ion battery. It can also suppress the oxidation reaction of the cathode material at higher temperatures, improving the thermal stability of the sodium-ion battery and thus enhancing its safety performance. The reduction in gas can also prevent deformation or damage to the sodium-ion battery due to gas expansion, improving the internal structural stability of the sodium-ion battery and further enhancing its safety performance.

[0008] Furthermore, when the cathode material includes transition metal elements, cyclic amine compounds can also capture the transition metal dissolved in the electrolyte, reducing the migration and deposition of transition metals from the cathode material to the anode surface. This avoids the generation of reducing gases (H2, alkanes, alkenes, etc.) on the anode, prevents transition metals from migrating to the anode surface and increasing impedance, and prevents sodium deposition, further improving the cycle stability and safety performance of sodium-ion batteries.

[0009] In some embodiments, the cyclic amine compound includes at least one of the structures shown in general formulas (I), (II), (III), and (IV) below;

[0010]

[0011] Among them, R1~R4, R 11 ~R 14 and R 17 ~R 25 They may be the same or different, and are independently selected from hydrogen and any one of C1 to C5 alkyl chains;

[0012] R5, R6, R8~R 10 R 15 and R 16 Whether the two are the same or different, they are independently selected from hydrogen and any one of the C1 to C3 alkyl chains;

[0013] R7 is selected from hydrogen and any of the C1-C3 alkylene chains.

[0014] In some embodiments, the cyclic amine compounds include at least one of piperazine and its derivatives, 1,4-dimethylpiperazine and its derivatives, triethylenediamine and its derivatives, hexamethylenetetramine and its derivatives, and N,N,4-trimethylpiperazine-1-ethylamine and its derivatives.

[0015] In some embodiments, the material of the functional layer further includes a first metal. A cyclic amine compound is coordinated to the first metal.

[0016] In some embodiments, the first metal is formed as a metal cluster and / or a metal ion.

[0017] In some embodiments, the first metal includes at least one of Ti, Zn, V, Zr, Cu, Fe, Mg, Al, Co, Mn, Ni, Nb, Sc, La, Sm, Yb, Ce, Cd, Cr, Dy, Er, Eu, Gd, Lu, Ca, and Bi.

[0018] In some embodiments, the material of the functional layer further includes a first ligand material, which is liganded to a first metal.

[0019] In some embodiments, at least one polycarboxylic compound.

[0020] In some embodiments, the first ligand material includes at least one of pyromellitic acid, 2,6-naphthalenedicarboxylic acid, and terephthalic acid.

[0021] In some embodiments, the thickness of the functional layer ranges from 0.1 μm to 10 μm.

[0022] In some embodiments, the substrate material includes at least one selected from polypropylene, polyethylene, ethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, polyimide, polyetherimide, polycarbonate, polyaramid, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, polycarbonate, polysulfate, and cellulose.

[0023] In some embodiments, the thickness of the substrate layer ranges from 5 μm to 20 μm.

[0024] Secondly, this application provides a sodium-ion battery, comprising: a positive electrode, a negative electrode, and a composite separator as described in any of the above embodiments. The negative electrode and the positive electrode are disposed opposite to each other. The composite separator is located between the positive electrode and the negative electrode.

[0025] It is understood that the beneficial effects of the sodium-ion battery provided in the above embodiments of this application can be referred to the beneficial effects of the composite separator mentioned above, and will not be repeated here.

[0026] In some embodiments, the composite separator is disposed at least on the surface of the substrate layer opposite to the positive electrode.

[0027] In some embodiments, the material of the positive electrode includes a transition metal element.

[0028] In some embodiments, the positive electrode material includes oxygen.

[0029] In some embodiments, the positive electrode material includes a transition metal oxide. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0032] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0033] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0034] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0035] Sodium-ion batteries, as a new type of rechargeable battery technology, have advantages such as abundant raw materials, low price, high safety and wide operating temperature range, and can be applied in electric new energy vehicles, smart grid energy storage and home energy storage systems.

[0036] Embodiments of this application provide a sodium-ion battery, comprising: a positive electrode, a negative electrode, and a separator. The negative electrode and the positive electrode are disposed opposite to each other. The separator is located between the positive electrode and the negative electrode.

[0037] During charging and discharging, sodium ions repeatedly insert and extract between the two electrodes. During charging, sodium ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode. At the same time, the compensating charge of electrons is supplied to the negative electrode through the external circuit to ensure the charge balance between the positive and negative electrodes. During discharging, the opposite occurs: sodium ions extract from the negative electrode, pass through the electrolyte, and insert into the positive electrode.

[0038] For example, the negative electrode material can be at least one of hard carbon, soft carbon, silicon-based, sodium metal, transition metal sulfide, or phosphide.

[0039] The separator is located between the positive and negative electrodes, and serves to isolate the positive and negative electrodes and prevent the battery from short-circuiting.

[0040] In some embodiments, the sodium-ion battery further includes an electrolyte.

[0041] The electrolyte, as the medium for electrochemical reactions, is a key factor determining the thermodynamic and kinetic processes of interfacial reactions in electrode materials.

[0042] For example, the electrolyte can be an ester or an ether.

[0043] In some embodiments, the positive electrode material includes: Na x TmO2, where Tm is a transition metal element and x ranges from 0.4 to 1.

[0044] In some sodium-ion batteries, poor interfacial stability between the cathode material and the electrolyte can lead to oxygen release side reactions. Singlet oxygen / oxygen radicals exhibit high reactivity and readily oxidize the electrolyte, generating oxidizing gases (such as carbon dioxide). These oxygen release side reactions also reduce the thermal stability of the sodium-ion battery, degrading its safety performance. Furthermore, when the cathode material contains transition metals, these elements can migrate to the anode, generating reducing gases (H2, alkanes, alkenes, etc.). These oxidizing and reducing gases increase the internal pressure of the sodium-ion battery, further affecting its safety. Moreover, when the cathode material contains transition metals, these elements may migrate and deposit on the anode surface, increasing surface impedance, potentially leading to sodium dendrite growth and membrane damage, resulting in short circuits in the sodium-ion battery.

[0045] Based on this, embodiments of this application provide a composite membrane, comprising: a base layer and a functional layer.

[0046] A functional layer is coated on at least one surface of the substrate layer, wherein the material of the functional layer includes cyclic amine compounds.

[0047] As the main component of the composite separator, the base layer provides basic mechanical strength and isolates the positive and negative electrodes to ensure that the positive and negative electrodes inside the sodium-ion battery do not come into direct contact, thereby preventing short circuits.

[0048] Cyclic amines are organic compounds that contain cyclic amines in their molecules; among them, cyclic amines are cyclic structures in which the ring atoms include two or more nitrogen atoms.

[0049] The cyclic amine compounds in the functional layer have the ability to adsorb singlet oxygen / reactive oxygen radicals. By adsorbing singlet oxygen / reactive oxygen radicals through cyclic amine compounds, the oxidative decomposition of the electrolyte can be effectively suppressed, thereby reducing the generation of oxidizing gases and improving the cycle stability of sodium-ion batteries. They can also suppress oxidation reactions of the cathode material at higher temperatures, improving the thermal stability of sodium-ion batteries and thus enhancing their safety performance. The reduction in gas can also prevent deformation or damage to the sodium-ion battery due to gas expansion, improving the internal structural stability of the sodium-ion battery and further enhancing its safety performance.

[0050] Furthermore, when the cathode material includes transition metal elements, cyclic amine compounds can also capture the transition metal dissolved in the electrolyte, reducing the migration and deposition of transition metals from the cathode material to the anode surface. This avoids the generation of reducing gases (H2, alkanes, alkenes, etc.) on the anode, prevents transition metals from migrating to the anode surface and increasing impedance, and prevents sodium deposition, further improving the cycle stability and safety performance of sodium-ion batteries.

[0051] In some examples, the functional layer is wrapped around a surface of the base layer.

[0052] In other examples, the functional layer covers both surfaces of the base layer.

[0053] In some embodiments, the cyclic amine compound includes at least one of the structures shown in general formulas (I), (II), (III), and (IV) below;

[0054]

[0055] Among them, R1~R4, R 11 ~R 14 and R 17 ~R 25 They may be the same or different, and are independently selected from hydrogen and any one of C1 to C5 alkyl chains;

[0056] R5, R6, R8~R 10 R 15 and R 16 They may be the same or different, and are independently selected from hydrogen and any one of the C1 to C3 alkyl chains.

[0057] R7 is selected from hydrogen and any of the C1-C3 alkylene chains.

[0058] Understandably, when the material of the functional layer includes at least one of the structures shown in general formulas (I), (II), (III), and (IV) above, the functional layer includes a cyclic amine compound. This cyclic amine compound can adsorb singlet oxygen / reactive oxygen radicals, thereby inhibiting the oxidative decomposition of the electrolyte, reducing gas generation, and thus improving the stability of the internal structure of the sodium-ion battery. Furthermore, it can capture transition metals in the cathode material, preventing dendrite growth in the sodium-ion battery and improving its performance. Moreover, the structures shown in general formulas (I), (II), (III), and (IV) above have the advantages of simple structure and easy availability.

[0059] In some embodiments, the cyclic amine compounds include at least one of piperazine and its derivatives, 1,4-dimethylpiperazine and its derivatives, triethylenediamine and its derivatives, hexamethylenetetramine and its derivatives, and N,N,4-trimethylpiperazine-1-ethylamine and its derivatives.

[0060] Piperazine is a diamine with a six-membered ring containing two nitrogen atoms. The structural formula of piperazine is: The structural formula of 1,4-dimethylpiperazine is: The cyclic structure of triethylenediamine contains two nitrogen atoms. The structural formula of triethylenediamine is: The cyclic structure of hexamethylenetetramine has four nitrogen atoms. The structural formula of hexamethylenetetramine is: N,N,4-Trimethylpiperazine-1-ethylamine is a derivative of piperazine, in which one hydrogen atom of nitrogen atom is replaced by an ethyl group, and the two hydrogen atoms of the other nitrogen atom are each replaced by a methyl group. The structural formula of N,N,4-trimethylpiperazine-1-ethylamine is [insert structural formula here].

[0061] Understandably, when the material of the functional layer includes at least one of the above-mentioned piperazine and its derivatives, 1,4-dimethylpiperazine and its derivatives, triethylenediamine and its derivatives, hexamethylenetetramine and its derivatives, and N,N,4-trimethylpiperazine-1-ethylamine and its derivatives, the material of the functional layer can adsorb singlet oxygen / reactive oxygen free radicals, thereby inhibiting the oxidative decomposition of the electrolyte, reducing gas generation, improving the cycle stability and safety performance of the sodium-ion battery, and capturing transition metals in the cathode material to prevent dendrite growth in the sodium-ion battery, further improving the cycle stability and safety performance of the sodium-ion battery.

[0062] In some embodiments, the material of the functional layer further includes a first metal. A cyclic amine compound is coordinated to the first metal.

[0063] In cyclic amine compounds, nitrogen atoms can act as electron donors, with their lone pairs of electrons distributed in the holes formed by the macrocycles. This results in a high electron cloud density in the center of the holes, enhancing the coordination ability of cyclic amine compounds with metal ions. Consequently, cyclic amine compounds can form stable metal complexes with the primary metal (e.g., MOF materials). MOF materials, through their porous structure and high specific surface area, provide favorable channels and sites for the insertion and extraction of sodium ions, thereby improving the specific capacity and cycle stability of sodium-ion batteries.

[0064] Moreover, the first metal can adsorb the transition metal in the positive electrode material, further reducing the migration and deposition of transition metal in the positive electrode material to the negative electrode surface, preventing the increase of negative electrode surface resistance and the occurrence of sodium precipitation side reactions, and improving the cycle stability and safety performance of sodium-ion batteries.

[0065] Furthermore, cyclic amine compounds can form stable metal complexes (such as MOF materials) with the first metal, which improves the mechanical strength of the composite membrane and prevents polymer shrinkage; and the metal complexes have abundant ion transport channels, which can improve the ion transport rate of sodium-ion batteries and enhance the performance of sodium-ion batteries, for example, it can improve the ion transport rate of sodium-ion batteries compared with ordinary ceramic layers.

[0066] In some embodiments, the first metal is formed as a metal cluster and / or a metal ion.

[0067] Metal clusters can provide more reaction sites, which is beneficial for the insertion and extraction of sodium ions. At the same time, metal clusters can also increase the ability to capture transition metals, thereby improving the performance of sodium-ion batteries.

[0068] Metal ions can form ordered structures in metal complexes (such as MOF materials), providing channels for the migration of sodium ions, enabling sodium ions to migrate more quickly and efficiently in sodium-ion batteries.

[0069] In some embodiments, the first metal includes at least one of Ti, Zn, V, Zr, Cu, Fe, Mg, Al, Co, Mn, Ni, Nb, Sc, La, Sm, Yb, Ce, Cd, Cr, Dy, Er, Eu, Gd, Lu, Ca, and Bi.

[0070] Understandably, when the first metal includes at least one of Ti, Zn, V, Zr, Cu, Fe, Mg, Al, Co, Mn, Ni, Nb, Sc, La, Sm, Yb, Ce, Cd, Cr, Dy, Er, Eu, Gd, Lu, Ca, and Bi, the first metal can form a metal complex with cyclic amine compounds, thereby improving the mechanical strength of the composite membrane and increasing the ion transport channels of the composite membrane, thus improving the stability of the sodium-ion battery.

[0071] In some embodiments, the material of the functional layer further includes a first ligand material. The first ligand material is ligated to the first metal.

[0072] Understandably, the coordination of the first ligand material with the first metal can make the metal complex more stable, increase the structural stability of the functional layer, help the sodium-ion battery maintain structural integrity during charging and discharging, and improve the cycle stability of the sodium-ion battery.

[0073] In some embodiments, at least one polycarboxylic compound.

[0074] Understandably, a polycarboxylated compound is a compound whose structural formula includes at least two carboxyl groups. The carboxyl groups can provide additional coordination sites, thereby enhancing the binding ability of the first ligand to the first metal and improving the stability of the functional layer material.

[0075] In some embodiments, the first ligand material includes at least one of pyromellitic acid, 2,6-naphthalenedicarboxylic acid, and terephthalic acid.

[0076] Understandably, pyromellitic acid and 2,6-naphthalenedicarboxylic acid terephthalic acid both contain groups that can form coordinate bonds with the first metal, thereby coordinating and combining with the first metal to form a more stable metal-organic framework (MOF) material. This further enhances the mechanical strength of the composite membrane and increases the ion transport channels of the composite membrane, thereby improving the stability of the sodium-ion battery.

[0077] In some embodiments, the thickness of the functional layer ranges from 0.1 μm to 10 μm.

[0078] For example, the thickness of the functional layer can be 0.1μm, 1μm, 3μm, 5μm, 7μm or 10μm, etc., and there is no limitation here.

[0079] The above configuration provides the functional layer with numerous active sites, enabling it to capture transition metal elements and adsorb singlet oxygen / reactive oxygen radicals. Furthermore, this configuration allows for a relatively thin functional layer, minimizing the increase in internal resistance of the sodium-ion battery and thus preventing this increase from negatively impacting its capacity.

[0080] In some embodiments, the substrate material includes at least one selected from polypropylene, polyethylene, ethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, polyimide, polyetherimide, polycarbonate, polyaramid, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, polycarbonate, polysulfate, and cellulose.

[0081] Understandably, polypropylene (PP) and polyethylene (PE) possess excellent mechanical strength, chemical stability, and cost-effectiveness. Ethylene oxide and polypropylene oxide have specific chemical and physical properties that can be used to control the permeability of materials. Polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) exhibit good chemical stability and high-temperature performance. Polymethyl methacrylate (PMMA) can be used in membranes requiring optical transparency. Polyacrylonitrile (PAN) has high strength and good thermal stability. Polyimide (PI) and polyetherimide (PEI) possess high-temperature stability and chemical inertness. Polycarbonate (PC) has good transparency and impact strength. Polyaramid fibers possess excellent mechanical strength and thermal stability. Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) have good mechanical properties and thermal stability. Polysulfate has good ionic conductivity. Cellulose has good biocompatibility and biodegradability. Using at least one of the above-mentioned base layer materials in the composite separator can improve the performance of sodium-ion batteries.

[0082] In some embodiments, the thickness of the substrate layer ranges from 5 μm to 20 μm.

[0083] For example, the thickness of the substrate layer can be 0.1μm, 1μm, 3μm, 5μm, 7μm or 10μm, etc., and there is no limitation here.

[0084] Understandably, the above configuration allows the composite membrane to have good mechanical strength, good thermal conductivity and chemical stability, which helps to promote sodium ion conduction.

[0085] Applying the composite separator described in any of the above embodiments to sodium-ion batteries can improve the stability of the internal structure of sodium-ion batteries.

[0086] In some embodiments, the composite separator is disposed at least on the surface of the substrate layer opposite to the positive electrode.

[0087] Understandably, the composite membrane can adsorb singlet oxygen / reactive oxygen radicals and transition metals dissolved in the electrolyte, and these singlet oxygen / reactive oxygen radicals and transition metals come from the cathode material. Therefore, through the above arrangement, the adsorption path can be shortened, resulting in better adsorption effect and further improving the structural stability of the sodium-ion battery.

[0088] In some embodiments, the positive electrode material includes a transition metal oxide.

[0089] For example, the positive electrode material as described above includes: Na x T m O2, T mIt is a transition metal element, and the value of x ranges from 0.4 to 1.

[0090] For example, transition metal oxides have layered or tunnel-type structures; among them, layered transition metal oxides (layered oxides) have the highest energy density, and the synthesis process is simple, with good compatibility between the production line and lithium battery ternary materials. Layered oxides can be lithium cobalt oxide, lithium nickel oxide, etc., and are not limited here.

[0091] Understandably, using the aforementioned transition metal oxides as cathode materials can enable sodium-ion batteries to have better capacity and electrochemical performance.

[0092] For example, layered oxides, due to their structural characteristics, have poor interfacial stability and are prone to transition metal dissolution and oxygen release side reactions, leading to decreased cycle performance and safety risks related to gas generation. A common approach is to modify the cathode material, but this involves complex processes and increases material costs. The composite separator of this application is at least disposed on the surface of the substrate layer opposite the cathode, a simpler and more convenient method that can improve production efficiency.

[0093] The invention will be further described in detail below through several specific experiments as examples.

[0094] Example 1

[0095] Example 1 provides a sodium-ion battery, comprising:

[0096] Positive electrode: The positive electrode material is a layered oxide.

[0097] Negative electrode: Hard carbon is selected as the negative electrode material.

[0098] Electrolyte: Carbonate-based electrolytes are selected.

[0099] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn and triethylenediamine, and the functional layer thickness is 4μm.

[0100] Example 2

[0101] Example 2 provides a sodium-ion battery, comprising:

[0102] Positive electrode: The positive electrode material is a layered oxide.

[0103] Negative electrode: Hard carbon is selected as the negative electrode material.

[0104] Electrolyte: Carbonate-based electrolytes are selected.

[0105] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and pyromellitic acid, and the functional layer thickness is 4μm.

[0106] Example 3

[0107] Example 3 provides a sodium-ion battery, comprising:

[0108] Positive electrode: The positive electrode material is a layered oxide.

[0109] Negative electrode: Hard carbon is selected as the negative electrode material.

[0110] Electrolyte: Carbonate-based electrolytes are selected.

[0111] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal cluster Cu, triethylenediamine and pyromellitic acid, and the functional layer thickness is 4μm.

[0112] Example 4

[0113] Example 4 provides a sodium-ion battery, comprising:

[0114] Positive electrode: The positive electrode material is a layered oxide.

[0115] Negative electrode: Hard carbon is selected as the negative electrode material.

[0116] Electrolyte: Carbonate-based electrolytes are selected.

[0117] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10 μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, 1,4-dimethylpiperazine and pyromellitic acid, and the functional layer thickness is 4 μm.

[0118] Example 5

[0119] Example 5 provides a sodium-ion battery, comprising:

[0120] Positive electrode: The positive electrode material is a layered oxide.

[0121] Negative electrode: Hard carbon is selected as the negative electrode material.

[0122] Electrolyte: Carbonate-based electrolytes are selected.

[0123] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and terephthalic acid, and the functional layer thickness is 4μm.

[0124] Example 6

[0125] Example 6 provides a sodium-ion battery, comprising:

[0126] Positive electrode: The positive electrode material is a layered oxide.

[0127] Negative electrode: Hard carbon is selected as the negative electrode material.

[0128] Electrolyte: Carbonate-based electrolytes are selected.

[0129] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and pyromellitic acid, and the functional layer thickness is 2μm.

[0130] Example 7

[0131] Example 7 provides a sodium-ion battery, comprising:

[0132] Positive electrode: The positive electrode material is a layered oxide.

[0133] Negative electrode: Hard carbon is selected as the negative electrode material.

[0134] Electrolyte: Carbonate-based electrolytes are selected.

[0135] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and pyromellitic acid, and the functional layer thickness is 8μm.

[0136] Example 8

[0137] Example 8 provides a sodium-ion battery, comprising:

[0138] Positive electrode: The positive electrode material is a layered oxide.

[0139] Negative electrode: Hard carbon is selected as the negative electrode material.

[0140] Electrolyte: Carbonate-based electrolytes are selected.

[0141] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and pyromellitic acid, and the thickness of the functional layer is 0.05μm.

[0142] Example 9

[0143] Example 9 provides a sodium-ion battery, comprising:

[0144] Positive electrode: The positive electrode material is a layered oxide.

[0145] Negative electrode: Hard carbon is selected as the negative electrode material.

[0146] Electrolyte: Carbonate-based electrolytes are selected.

[0147] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn, triethylenediamine and pyromellitic acid, and the functional layer thickness is 12μm.

[0148] Comparative Example 1

[0149] Comparative Example 1 provides a sodium-ion battery, comprising:

[0150] Positive electrode: The positive electrode material is a layered oxide.

[0151] Negative electrode: Hard carbon is selected as the negative electrode material.

[0152] Electrolyte: Carbonate-based electrolytes are selected.

[0153] Diaphragm: The diaphragm is made of polyethylene (PP) with a thickness of 10μm.

[0154] Comparative Example 2

[0155] Comparative Example 2 provides a sodium-ion battery, comprising:

[0156] Positive electrode: The positive electrode material is a layered oxide.

[0157] Negative electrode: Hard carbon is selected as the negative electrode material.

[0158] Electrolyte: Carbonate-based electrolytes are selected.

[0159] Composite membrane: The base layer material of the composite membrane is polyethylene (PP) with a thickness of 10μm; the functional layer material of the composite membrane includes MOF material formed by metal clusters Zn and pyromellitic acid, and the functional layer thickness is 4μm.

[0160] Performance testing

[0161] 1. Capacity testing of sodium-ion batteries in the examples and comparative examples: The assembled pouch batteries were subjected to capacity testing at 25°C, and the results are shown in Table 1.

[0162] 2. Cyclic testing of sodium-ion batteries in the examples and comparative examples: The sodium-ion batteries after capacity testing were subjected to 1C cycle testing in an environment of 25°C. The cell volume before the test and after 1000 cycles was recorded, and the volume of gas produced was calculated. The results are shown in Table 1.

[0163] 3. Gas testing: Gas was extracted from sodium ions in the examples and comparative examples after cycling, and the gas composition was analyzed using GC-MS. The proportion of oxidizing gas CO2 was calculated, and the results are shown in Table 1.

[0164] 4. Transition metal test: Disassemble the empty-charge sodium-ion batteries of the examples and comparative examples after cycling, clean and collect the negative electrode coating and perform ICP test, calculate the total content of transition metal elements, and the results are shown in Table 1.

[0165] 5. Thermal Stability Test: The thermal stability of the sodium-ion batteries in the examples and comparative examples was measured using an adiabatic calorimeter (ARC). Specifically, a fully charged sodium-ion battery was placed in an adiabatic chamber under an argon atmosphere and heated at 10°C / min. After the sodium-ion battery temperature stabilized, it was observed whether there was any self-heating phenomenon. If so, the temperature change of the sodium-ion battery was tracked until the sodium-ion battery reached a thermal runaway state.

[0166] Table 1. Performance test results of sodium-ion batteries in the examples and comparative examples.

[0167]

[0168] As shown in Table 1, the capacity retention rate of the sodium-ion batteries in Examples 1 to 9 after 1000 cycles is significantly greater than that of the sodium-ion battery in Comparative Example 1 after 1000 cycles, indicating that the introduction of cyclic amine compounds into the functional layer in this application can significantly improve the cycle stability of sodium-ion batteries.

[0169] The capacity of the sodium-ion batteries in Examples 1 to 9 was not significantly reduced compared to that of the sodium-ion battery in Comparative Example 1. This means that the functional layer does not significantly affect the capacity performance of the composite separator or increase its impedance, indicating that the introduction of cyclic amine compounds into the functional layer does not affect the capacity performance of the sodium-ion battery.

[0170] The gas volume, CO2 content, and transition metal content of the sodium-ion battery in Example 1 were significantly lower than those of the sodium-ion battery in Comparative Example 2. This is attributed to the introduction of cyclic amine compounds into the functional layer of the composite separator in the sodium-ion battery of Example 1. This enhances the capture of transition metal elements while increasing the adsorption of singlet oxygen / reactive oxygen radicals, avoiding the decomposition of the electrolyte into gas (the main source of gas production), reducing the proportion of oxidizing gas CO2, and further improving cycle stability.

[0171] Furthermore, the gas volume and transition metal content of the sodium-ion batteries in Examples 1 to 9 are significantly less than those of the sodium-ion battery in Comparative Example 1. This is attributed to the fact that introducing MOF material into the functional layer can adsorb a small amount of gas. More importantly, MOF can effectively capture the transition metal elements dissolved on the positive electrode side, avoiding the increase in impedance and sodium precipitation side reaction caused by the deposition of transition metals on the negative electrode side. Compared with the sodium-ion battery in Comparative Example 1 (without a functional layer in the separator), the cycle stability is significantly improved.

[0172] Furthermore, the specific charging capacity and specific discharging capacity of the sodium-ion batteries in Examples 1 to 8 are higher than those in Example 9. This is attributed to the fact that the thickness of the functional layer of the composite separator in the sodium-ion batteries of Examples 1 to 8 is in the range of 0.1 μm to 10 μm. The relatively small thickness of the functional layer can reduce the increase in the internal resistance of the sodium-ion battery, thereby avoiding the increase in internal resistance affecting the capacity of the sodium-ion battery. Although the sodium-ion battery of Example 9 has better results in terms of gas volume, CO2 content, and transition metal content, the thicker functional layer will increase the internal resistance of the sodium-ion battery, leading to a decrease in the capacity of the sodium-ion battery.

[0173] The maximum thermal runaway temperature and the highest self-heating rate of the sodium-ion batteries in Examples 1 to 9 are lower than those of the sodium-ion batteries in Comparative Examples 1 and 2. This is attributed to the fact that during the thermal stability test, the adsorption of singlet oxygen / reactive oxygen radicals by the cyclic amines inhibited the oxidation reaction of the cathode material at higher temperatures, thus reducing the maximum thermal runaway temperature and the highest self-heating rate that the sodium-ion batteries in the examples could reach when thermal runaway occurred, thereby improving the safety performance of the sodium-ion batteries.

[0174] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A composite separator, characterized by, include: basal layer; A functional layer, covering at least one surface of the base layer; The material of the functional layer includes cyclic amine compounds.

2. The composite separator of claim 1, wherein The cyclic amine compounds include at least one of the structures shown in general formulas (I), (II), (III), and (IV); wherein R1to R4, R 11 to R 14 and R 17 to R 25 are the same or different, each independently selected from hydrogen and any one of C1to C5alkyl chain; R5, R6, R8~R 10 , R 15 and R 16 are the same or different, each independently selected from the group consisting of hydrogen and any one of C1~C3 alkyl chain; R7 is selected from hydrogen and any of the C1-C3 alkylene chains.

3. The composite separator of claim 1, wherein The cyclic amine compounds include at least one of piperazine and its derivatives, 1,4-dimethylpiperazine and its derivatives, triethylenediamine and its derivatives, hexamethylenetetramine and its derivatives, and N,N,4-trimethylpiperazine-1-ethylamine and its derivatives.

4. The composite separator according to any one of claims 1 to 3, characterized in that, The material of the functional layer also includes a first metal; the cyclic amine compound is coordinated to the first metal.

5. The composite separator of claim 4, wherein The first metal formation is: metal clusters, and / or, metal ions.

6. The composite separator of claim 5, wherein The first metal includes at least one of the following: Ti, Zn, V, Zr, Cu, Fe, Mg, Al, Co, Mn, Ni, Nb, Sc, La, Sm, Yb, Ce, Cd, Cr, Dy, Er, Eu, Gd, Lu, Ca, and Bi.

7. The composite separator of claim 4, wherein The material of the functional layer further includes: a first ligand material, wherein the first ligand material is ligated to the first metal.

8. The composite diaphragm according to claim 7, characterized in that, The first ligand material includes at least one polycarboxylic acid compound.

9. The composite diaphragm according to claim 8, characterized in that, The first ligand material includes at least one of pyromellitic acid, 2,6-naphthalenedicarboxylic acid, and terephthalic acid.

10. The composite diaphragm according to claim 1, characterized in that, The thickness of the functional layer ranges from 0.1 μm to 10 μm.

11. The composite diaphragm according to any one of claims 1 to 10, characterized in that, The base layer material includes at least one of the following: polypropylene, polyethylene, ethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, polyimide, polyetherimide, polycarbonate, polyaramid, polyethylene terephthalate, polybutylene terephthalate, polyacrylonitrile, polycarbonate, polysulfate, and cellulose.

12. The composite diaphragm according to claim 1, characterized in that, The thickness of the substrate layer ranges from 5 μm to 20 μm.

13. A sodium-ion battery, characterized in that, include: positive electrode; The negative electrode is disposed opposite to the positive electrode; and, The composite separator according to any one of claims 1 to 12, wherein the composite separator is located between the positive electrode and the negative electrode.

14. The sodium-ion battery according to claim 13, characterized in that, The composite membrane is disposed at least on the surface of the substrate layer opposite to the positive electrode.

15. The sodium-ion battery according to claim 13, characterized in that, The positive electrode material includes: transition metal oxides.

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