Separator membrane for sodium metal battery without negative electrode, Sodium metal battery without negative electrode

Abstract

The application relates to a separator film for a sodium metal battery without a negative electrode, which realizes uniform deposition of sodium by arranging a support layer on part of the separator film and adopting a material containing a sodium-philic functional group as the support material, so that the cycle life of the sodium metal battery without a negative electrode is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a separator for a sodium metal battery without a negative electrode, a sodium metal battery without a negative electrode, a battery module, a secondary battery pack, and an electrical device. Background Technology

[0002] The reaction mechanism of a cathode-free sodium metal battery is a deposition mechanism. In this battery, a current collector serves as the negative electrode. During charging, sodium ions released from the positive electrode deposit onto the current collector to form a sodium metal negative electrode. Because there is no negative electrode active material layer, the cell's mass and volume can be significantly reduced, increasing the battery's energy density. However, the relatively short cycle life of cathode-free sodium metal batteries hinders their practical application.

[0003] Therefore, it is necessary to further improve the cycle life of sodium metal batteries without negative electrodes. Summary of the Invention

[0004] In view of the problems existing in the background art, this application provides a separator for a non-negative electrode sodium metal battery, which can improve the cycle life of the non-negative electrode sodium metal battery.

[0005] The first aspect of this application provides a separator for a sodium metal battery without a negative electrode. At least one surface of the separator is provided with a support layer, which covers a portion of the surface. The support layer includes a support material containing sodium-loving functional groups.

[0006] This application achieves uniform sodium deposition by setting a support layer on a portion of the separator and using a material containing sodium-loving functional groups as the support layer material, thereby improving the cycle life of the anode-free sodium metal battery.

[0007] In some embodiments, according to the first aspect, a first example of the first aspect is proposed, wherein the sodium-loving functional group includes one or more of C=O, OH, and C≡N.

[0008] Optimizing the types of sodium-loving functional groups can help improve the uniformity of sodium deposition and increase the cycle life of sodium metal batteries without a negative electrode.

[0009] In some embodiments, according to the first aspect, a second example of the first aspect is provided, wherein the thickness of the support layer is 10-50 μm. Preferably, the thickness of the support layer is 12-20 μm.

[0010] Optimizing the thickness of the support layer can improve the cycle life of sodium metal batteries without negative electrodes, and also improve the energy density of the battery.

[0011] In some embodiments, according to the first aspect, a third example of the first aspect is provided, wherein the support material comprises a polymer containing sodium-functional groups. Preferably, the polymer comprises one or more of carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate. Alternatively, the support material comprises a polymer modified with sodium-functional groups. Preferably, the polymer comprises one or more of polyvinylidene fluoride and styrene-butadiene rubber.

[0012] Choosing polymers as the support layer material can not only provide effective support, but also facilitate the modification of sodium-loving functional groups, thereby improving the uniformity of sodium deposition.

[0013] In some embodiments, according to the first aspect, a fourth example of the first aspect is proposed, wherein the support layer further includes an inorganic material. Preferably, the inorganic material includes one or more of Al2O3, SiO2, and Mg(OH)2.

[0014] Adding inorganic materials to the support layer can improve its support effect, which in turn can improve the uniformity of sodium deposition, thereby increasing the cycle life of the anode-free sodium metal battery.

[0015] In some embodiments, according to the first aspect, a fifth example of the first aspect is provided, wherein the support layer further includes an elastic material to make the support layer elastic. Preferably, the elastic material includes one or more of styrene thermoplastic elastomer, ethylene propylene diene monomer (EPDM) rubber, thermoplastic EPDM dynamically vulcanized elastomer, polyolefin thermoplastic elastomer, and thermoplastic polyester elastomer.

[0016] By adding an elastic material to the support layer material, the support layer becomes elastic. When the gap between the negative electrode and the separator is filled with deposited sodium metal, sodium ions can continue to deposit due to the elasticity of the support layer. Subsequently, the sodium metal layer will be subjected to a certain pressure, which is beneficial to the shaping of the sodium metal deposition, thereby helping to obtain a denser and more uniform metal deposition layer and improving the cycle life of the negative electrode-free sodium metal battery.

[0017] In some embodiments, according to the first aspect, a sixth example of the first aspect is proposed, wherein the elastic material accounts for 15% to 30% of the mass of the support layer.

[0018] By optimizing the amount of elastic material used, the support layer can be made both elastic and supportive, thereby improving the uniformity of sodium deposition.

[0019] In some embodiments, according to the first aspect, a seventh example of the first aspect is provided, wherein the areal density of the support layer is 3.25 × 10⁻⁶. -4 ~3.25×10 -3 mg / mm 2 .

[0020] Controlling the areal density within a certain range can help improve the uniformity of sodium deposition.

[0021] In some embodiments, according to the first aspect, an eighth example of the first aspect is proposed, wherein the support layer is distributed on the isolation membrane in a raised, grid-like, or striped manner.

[0022] Optimizing the distribution pattern of the support layer can help improve the uniformity of sodium deposition.

[0023] In some embodiments, according to the first aspect, a ninth example of the first aspect is proposed, wherein the protrusion is island-shaped.

[0024] The support layer is distributed in an island-like pattern, which is more conducive to improving the uniformity of sodium deposition.

[0025] In some embodiments, according to the first aspect, a tenth example of the first aspect is provided, wherein the shape of any single island structure is cylindrical, hemispherical, or spherical. The diameter of any single island structure is 5-50 μm.

[0026] Optimizing the shape and diameter of individual island structures helps prevent them from becoming too thin and piercing the isolation membrane, or from collapsing and losing their supporting function.

[0027] A second aspect of this application provides a sodium metal battery without a negative electrode, comprising a negative electrode sheet and a separator. The separator is the same as that of the first aspect of this application. A support layer exists between at least the negative electrode sheet and the separator.

[0028] A third aspect of this application provides a battery module, including the negative electrode-free sodium metal battery of the second aspect of this application.

[0029] The fourth aspect of this application provides a secondary battery pack, including a negative electrode-free sodium metal battery of the second aspect of this application or a battery module of the third aspect of this application.

[0030] The fifth aspect of this application provides an electrical device, including at least one of the following: a negative electrode-free sodium metal battery of the second aspect of this application, a battery module of the third aspect of this application, and a secondary battery pack of the fourth aspect of this application.

[0031] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a separator for a sodium metal battery without a negative electrode according to one embodiment of this application.

[0033] Figure 2This is a schematic diagram of a separator for a sodium metal battery without a negative electrode, according to another embodiment of this application.

[0034] Figure 3 This is a schematic diagram of a separator for a sodium metal battery without a negative electrode, according to another embodiment of this application. Detailed Implementation

[0035] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion.

[0037] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0038] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more (including two).

[0039] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists, A and B exist simultaneously, and B exists.

[0040] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.

[0041] The reaction mechanism of a cathode-free sodium metal battery is a deposition mechanism. In this battery, a current collector serves as the negative electrode, and sodium ions released from the positive electrode during charging are deposited onto the current collector to form a sodium metal negative electrode. Because there is no negative electrode active material layer, the cell's mass and volume can be significantly reduced, increasing the battery's energy density. However, the short cycle life of cathode-free sodium metal batteries hinders their practical application. Therefore, further improvements in the cycle life of cathode-free sodium metal batteries are needed.

[0042] Research has found that during the cell manufacturing process, cold pressing or hot pressing is required, which causes the separator and the negative electrode to stick together, leaving no gaps between them. This is not conducive to the uniform deposition of sodium metal. Furthermore, the diffusion rate of sodium ions near the electrode and electrolyte interface also affects the uniformity of sodium deposition, thus affecting the cycle life of the cell.

[0043] Based on this, this application designs a separator for a negative electrode-free sodium metal battery. A support layer is provided on a portion of the separator, and a material containing sodium-loving functional groups is used as the support layer material. This provides a deposition space for sodium ions while improving the adsorption capacity of the support layer material for sodium ions, significantly accelerating the diffusion of sodium ions near the interface between the negative electrode and the electrolyte, eliminating ion concentration polarization, and achieving uniform sodium deposition, thereby improving the cycle life of the negative electrode-free sodium metal battery.

[0044] The technical solutions described in this application are applicable to separators for non-negative-electrode sodium metal batteries, and are also applicable to non-negative-electrode sodium metal batteries using the separator, battery modules using non-negative-electrode sodium metal batteries, secondary battery packs using non-negative-electrode sodium metal batteries or battery modules, and electrical devices using at least one of non-negative-electrode sodium metal batteries, battery modules, and secondary battery packs.

[0045] In a first aspect, according to some embodiments of this application, this application provides a separator for a sodium metal battery without a negative electrode. At least one surface of the separator is provided with a support layer, the support layer covering a portion of the surface. The support layer includes a support material. The support material contains sodium-loving functional groups.

[0046] In some embodiments, the sodium-loving functional group may include one or more of C=O, OH, and C≡N.

[0047] Optimizing the types of sodium-loving functional groups can help improve the uniformity of sodium deposition and increase the cycle life of sodium metal batteries without a negative electrode.

[0048] In some embodiments, the thickness of the support layer may be 10-50 μm. Preferably, the thickness of the support layer may be 12-20 μm.

[0049] Optimizing the thickness of the support layer can improve the cycle life of a negative electrode-less sodium metal battery and also increase its energy density. If the support layer is too thin, it cannot provide sufficient deposition space for sodium ions. If the support layer is too thick, the gap between the negative electrode and the separator will be too large, allowing sodium metal to deposit freely. This results in a loose and disordered metal layer structure, which is detrimental to the uniformity of the sodium metal layer. Furthermore, it can easily form dendrites, piercing the separator and causing a short circuit within the cell.

[0050] In some specific embodiments, the thickness of the support layer can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm. The thickness of the support layer can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0051] In some embodiments, the support material comprises a polymer containing sodium-loving functional groups. Preferably, the polymer comprises one or more of carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate.

[0052] Choosing polymers containing sodium-loving functional groups as support materials can achieve effective support and improve the uniformity of sodium deposition.

[0053] In some specific embodiments, the polyacrylate may include one or more of polybutyl acrylate, polypentyl acrylate, polyhexyl acrylate, polyhedral acrylate, and polyoctyl acrylate.

[0054] In some embodiments, the support material comprises a polymer modified with sodium-loving functional groups. Preferably, the polymer comprises one or more of polyvinylidene fluoride and styrene-butadiene rubber.

[0055] Choosing polymers modified with sodium-loving functional groups as support materials can achieve effective support and improve the uniformity of sodium deposition.

[0056] This application does not limit the methods for modifying polymers with sodium-philic functional groups; any conventional methods for modifying polymers with sodium-philic functional groups can be used in this application.

[0057] In some embodiments, the support layer also includes inorganic materials.

[0058] In some specific embodiments, the inorganic material may include heat-resistant inorganic ceramic particles, such as one or more of Al2O3, SiO2, and Mg(OH)2.

[0059] In some specific embodiments, the mass ratio of the support material (such as polymer support material) to the inorganic material can be (0.2 to 0.5):1, for example, 0.2:1, 0.3:1, 0.4:1 or 0.5:1.

[0060] Inorganic materials are relatively hard. Adding inorganic materials to the support layer can improve the support effect of the support layer, which in turn can improve the uniformity of sodium deposition and thus improve the cycle life of the anode-free sodium metal battery.

[0061] In some embodiments, the support layer may also include an elastic material to make the support layer elastic.

[0062] By adding an elastic material to the support layer material, the support layer becomes elastic. When the gap between the negative electrode and the separator is filled with deposited sodium metal, sodium ions can continue to deposit due to the elasticity of the support layer. Subsequently, the sodium metal layer will be subjected to a certain pressure, which is beneficial to the shaping of the sodium metal deposition, thereby helping to obtain a denser and more uniform metal deposition layer and improving the cycle life of the negative electrode-free sodium metal battery.

[0063] In some specific embodiments, the elastic material may include one or more of the following: styrene thermoplastic elastomer (SBS), ethylene propylene diene monomer (EPDM), thermoplastic ethylene propylene diene monomer dynamically vulcanized elastomer (TPV), polyolefin thermoplastic elastomer (TPO), and thermoplastic polyester elastomer (TPEE).

[0064] In some embodiments, the elastic material may account for 15% to 30% of the mass of the support layer.

[0065] By optimizing the amount of elastic material used, the support layer can be made both elastic and supportive, thereby improving the uniformity of sodium deposition.

[0066] In some specific embodiments, the mass percentage of the elastic material in the support layer can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%. The mass percentage of the elastic material in the support layer can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0067] In some embodiments, the areal density of the support layer may be 3.25 × 10⁻⁶. -4 ~3.25×10 -3 mg / mm 2 .

[0068] Controlling the areal density within a certain range is beneficial for improving the uniformity of sodium deposition. If the areal density is too high, the support layer cannot provide enough deposition space for sodium metal, resulting in poor deposition uniformity. If the areal density is too low, the support effect of the support layer is too poor, and it will collapse during the cold pressing process, causing the separator and the negative electrode to stick together, which also cannot provide enough deposition space and is not conducive to uniform sodium deposition.

[0069] In some specific embodiments, the areal density of the support layer may be 3.25 × 10⁻⁶. -4 mg / mm 2 5×10 -4 mg / mm 2 8×10 -4 mg / mm 2 1×10 -3 mg / mm 2 1.5×10 -3 mg / mm 2 2×10 -3 mg / mm 2 2.5×10 -3 mg / mm 2 3×10 -3 mg / mm 2 Or 3.25×10 -3 mg / mm 2 The areal density of the support layer can be within a range defined by any two of the values ​​listed above as endpoints.

[0070] In some embodiments, the support layer is distributed on the isolation membrane in a raised, grid-like, or striped pattern.

[0071] Optimizing the distribution pattern of the support layer can help improve the uniformity of sodium deposition.

[0072] In some embodiments, the protrusions are island-shaped.

[0073] When the support layer is distributed in an island-like pattern, the island structure can serve as a nucleation site for metal deposition, which is more conducive to improving the uniformity of sodium deposition.

[0074] In some embodiments, the shape of any single island structure is cylindrical, hemispherical, or spherical. The diameter of any single island structure can be 5-50 μm.

[0075] Optimizing the shape of individual island structures to ensure a flat bottom prevents puncture of the separator membrane. Optimizing the diameter of individual island structures helps prevent them from becoming too thin and puncturing the separator membrane, or collapsing and losing their supporting function. Larger island structures occupy a larger area on the separator membrane, which is detrimental to the uniformity of sodium metal deposition.

[0076] In some specific embodiments, the diameter of any single island structure can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm. The diameter of any single island structure can be within a numerical range formed by using any two of the values ​​listed above as endpoints.

[0077] In some embodiments, the separator includes a substrate layer, which is a nonwoven fabric, membrane, or composite membrane with a porous structure. In some specific embodiments, the material of the substrate layer may include at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyimide. In some specific embodiments, the material of the substrate layer may include a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.

[0078] In some embodiments, a surface treatment layer may be provided on at least one surface of the substrate layer. In some specific embodiments, the surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials. In some specific embodiments, the polymer layer may contain a polymer. The polymer material may include at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene). In some specific embodiments, the inorganic layer may include inorganic particles and a binder. In some specific embodiments, the inorganic particles may include one or more combinations of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. In some specific embodiments, the adhesive may include one or more combinations of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0079] A second aspect of this application provides a sodium metal battery without a negative electrode, comprising a negative electrode sheet and a separator. The separator is the same as that of the first aspect of this application. A support layer exists between at least the negative electrode sheet and the separator.

[0080] The negative electrode sheet of this application is a negative current collector, and its surface does not have a negative active material layer.

[0081] In some embodiments, the negative electrode current collector used may include at least one of metal foil current collectors, metal foam current collectors, metal mesh current collectors, carbon felt current collectors, carbon cloth current collectors, and carbon paper current collectors. Sodium ions do not form alloys with aluminum; therefore, for cost and weight reduction considerations, aluminum-based current collectors are preferred. The aluminum-based current collector can be any one of aluminum foil, aluminum alloy foil, and aluminum-based composite current collectors. The aluminum-based composite current collector includes a polymer base film and aluminum foil and / or aluminum alloy foil formed on both sides of the polymer base film. Specifically, the aluminum-based composite current collector has a "sandwich" structure, with the polymer base film in the middle and aluminum foil or aluminum alloy foil on both sides. Alternatively, one side of the polymer base film may have aluminum foil, and the other side may have aluminum alloy foil. The polymer base film may include any one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate. Preferably, the aluminum-based composite current collector selected in this invention has better ductility, which is beneficial for maintaining the integrity of the electrode during sodium deposition / removal.

[0082] In some embodiments, the surface of the negative electrode current collector may be provided with a conductive coating. The conductive coating may include a conductive agent and a binder. The conductive agent may include one or more of hard carbon, conductive carbon black, graphite, carbon fiber, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and fullerene. The binder may include one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium polyacrylate, polytetrafluoroethylene, polyimide, and polyurethane.

[0083] A third aspect of this application provides a battery module, including the negative electrode-free sodium metal battery of the second aspect of this application.

[0084] The fourth aspect of this application provides a secondary battery pack, including a negative electrode-free sodium metal battery of the second aspect of this application or a battery module of the third aspect of this application.

[0085] The fifth aspect of this application provides an electrical device, including at least one of the following: a negative electrode-free sodium metal battery of the second aspect of this application, a battery module of the third aspect of this application, and a secondary battery pack of the fourth aspect of this application.

[0086] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all reagents used in the embodiments are commercially available or synthesized by conventional methods, and the instruments used in the embodiments are commercially available.

[0087] Example 1

[0088] (1) Preparation of a support layer on the isolation membrane

[0089] Polyvinylidene fluoride (PVDF) was added to a high-concentration NaOH solution (15 mol / L) for alkalization for 10 h. After filtration, PVDF containing hydroxyl groups was obtained. The PVDF containing hydroxyl groups was mixed with the solvent N-methylpyrrolidone to obtain a support slurry, which was then coated onto one surface of a separating membrane (porous polyethylene film). After drying, a 20 μm thick support layer was formed. The support layer was distributed in an island-like pattern on the separating membrane, covering part of the membrane surface. Each individual island-like structure was cylindrical with a diameter of 5 μm. Figure 1 As shown.

[0090] (2) Preparation of negative electrode sheet

[0091] Prepare hard carbon and binder polyvinylidene fluoride (PVDF) in a mass ratio of 60:40. The Dv50 of the hard carbon is 500 nm. Dissolve the hard carbon and binder in deionized water to obtain a conductive coating slurry. Prepare a current collector (copper foil). Coat the current collector with the conductive coating slurry. After drying, the coating thickness is 2 μm. The negative electrode sheet is obtained through processes such as compaction.

[0092] (3) Preparation of positive electrode sheet

[0093] The positive electrode active material NaFePO4, the conductive agent acetylene black, and the binder carboxymethyl cellulose were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to form a uniform positive electrode slurry. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die cutting, a positive electrode sheet with a thickness of 200 μm was obtained.

[0094] (4) Preparation of electrolyte

[0095] In an argon-filled glove box with a water content of <1ppm, diethylene glycol dimethyl ether and tetrahydrofuran were mixed at a mass ratio of 1:3, and sodium hexafluorophosphate (NaPF6) with a concentration of 1.0mol / L was added. After stirring evenly, an electrolyte was obtained.

[0096] (5) Preparation of a negative electrode-free sodium metal battery

[0097] The positive electrode, separator, and negative electrode obtained in the above steps are stacked in sequence, such that the separator is located between the positive and negative electrode and can isolate the positive and negative electrode, and there is a support layer between the negative electrode and the separator; then the stacked components are wound to obtain an electrode assembly; the electrode assembly is placed in the housing, dried, and then injected with electrolyte; after formation, settling and other processes, a sodium metal battery without a negative electrode is obtained.

[0098] Example 2

[0099] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that a support layer slurry was coated on both surfaces of the separator, and finally an island-shaped support layer was formed on both surfaces.

[0100] Example 3-Example 4

[0101] Anode-free sodium metal batteries were prepared according to the method of Example 1. The difference is that the support materials of Examples 3-4 are different from those of Example 1, and the sodium-loving functional groups contained are different from those of Example 1, as shown in Table 1 below.

[0102] Table 1

[0103]

[0104]

[0105] Examples 5-7

[0106] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that inorganic matter was mixed into the support slurry. The mass ratio of PVDF containing hydroxyl groups to inorganic matter was 0.3:1, as shown in Table 2 below.

[0107] Table 2

[0108] Example 5 <![CDATA[Al2O3]]> Example 6 <![CDATA[SiO2]]> Example 7 <![CDATA[Mg(OH)2]]>

[0109] Examples 8-12

[0110] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that the thickness of the support layer in Examples 8-12 was different from that in Example 1, as shown in Table 3 below.

[0111] Table 3

[0112]

[0113]

[0114] Example 13

[0115] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that an elastic material, namely styrene thermoplastic elastomer (SBS), was mixed into the support slurry of Example 1, so that the mass ratio of the elastic material in the support layer was 15%.

[0116] Examples 14-15

[0117] A negative electrode-free sodium metal battery was prepared according to the method of Example 13, except that the mass ratio of elastic material in the support layer was different, as shown in Table 4 below.

[0118] Table 4

[0119]

[0120] Examples 16-19

[0121] A negative electrode-free sodium metal battery was prepared according to the method of Example 13, except that the elastic material mixed in was different, as shown in Table 5 below.

[0122] Table 5

[0123]

[0124] Examples 20-24

[0125] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, and the areal density of the support layer was further controlled as shown in Table 6 below.

[0126] Table 6

[0127] Example 20 <![CDATA[3×10 -4 ]]> Example 21 <![CDATA[3.25×10 -4 ]]> Example 22 <![CDATA[2×10 -3 ]]> Example 23 <![CDATA[3.25×10 -3 ]]> Example 24 <![CDATA[3.5×10 -3 ]]>

[0128] Example 25

[0129] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that a grid-like support layer was formed on one surface of the separator, such as... Figure 2 As shown.

[0130] Example 26

[0131] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that a striped support layer was formed on one surface of the separator, such as... Figure 3 As shown.

[0132] Examples 27-29

[0133] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that the diameter of the individual island structure was different from that in Example 1, as shown in Table 7 below.

[0134] Table 7

[0135] Example 27 cylindrical 10 Example 28 cylindrical 30 Example 29 cylindrical 50

[0136] Example 30

[0137] A sodium metal battery without a negative electrode was prepared according to the method of Example 1, except that the shape of the individual island structure was hemispherical.

[0138] Example 31

[0139] A sodium metal battery without a negative electrode was prepared according to the method of Example 1, except that the shape of the individual island structure was spherical.

[0140] Example 32

[0141] A sodium metal battery without a negative electrode was prepared according to the method of Example 1, except that the PVDF in step (1) was replaced with styrene-butadiene rubber for alkalization.

[0142] Examples 33-34

[0143] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that the supporting material used was different, that is, the PVDF containing hydroxyl groups was replaced with the materials listed in Table 8 below.

[0144] Table 8

[0145] Example 33 Carboxymethyl cellulose Example 34 Polybutyl acrylate

[0146] Comparative Example 1

[0147] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that the separator was a porous polyethylene polymer film without a support layer.

[0148] Comparative Example 2

[0149] A negative electrode-free sodium metal battery was prepared according to the method of Example 1, except that PVDF was directly mixed with a solvent to prepare a support slurry, and the PVDF was not alkalized.

[0150] Characterization test

[0151] 1. Thickness test of the support layer

[0152] The porous polyethylene polymer film used in Example 1 is laid flat on a horizontal surface and folded N times. It is then measured multiple times using a micrometer (e.g., a Mitutoyo digital micrometer). The total thickness is denoted as Da. The prepared separator film with a support layer is laid flat on a horizontal surface and folded N times. It is then measured multiple times using a micrometer (e.g., a Mitutoyo digital micrometer). The total thickness is denoted as Db. Then, the thickness of the support layer is d1 = (Db - Da) / 2N.

[0153] 2. Mass percentage test of elastic material in the support layer

[0154] The square coated isolation membrane with a size of 10cm*10cm (the isolation membrane with a support layer prepared in Examples 12-14) was weighed to obtain its mass M1. The square isolation membrane base film with a size of 10cm*10cm was weighed to obtain its mass M2. M3 = M1-M2, which is the total weight of the support layer. The support layer was dispersed in anhydrous ethanol solution, and the elastic material particles were filtered out and weighed to obtain its mass M4. The ratio of M4 / M3 is the mass proportion of the elastic material in the support layer.

[0155] 3. Areal density test of the support layer

[0156] Weigh a square isolation membrane with a support layer measuring 10cm*10cm to obtain its mass, and then divide it by its area to obtain its areal density.

[0157] 4. Diameter test of a single island structure

[0158] The prepared isolation membrane with the support layer was cut into samples. Using an X-Max energy dispersive spectrometer (EDS) from Oxford Instruments (UK) combined with a Sigma-02-33 scanning electron microscope (SEM) from ZEISS (Germany), a suitable cylindrical island structure was selected on the cut sample to measure its diameter.

[0159] Battery performance test

[0160] 1. Cyclic life test

[0161] Five battery cells from each of the above embodiments and comparative examples were used for parallel experiments. Each battery cell was charged at room temperature at a rate of 0.33C to a voltage of 3.65V, and then discharged at a rate of 0.33C to a voltage of 2.5V. The reversible capacity was measured as C0. This charging and discharging process was repeated until the discharge capacity Cn / C0 ≤ 80% in a certain cycle. The total number of cycles was recorded as X-Cycle. Here, Cn is the reversible capacity at the nth cycle. The results are shown in Table 9 below.

[0162] Table 9

[0163]

[0164]

[0165]

[0166] As can be seen from the examples and comparative examples, this application achieves uniform sodium deposition by setting a support layer on a portion of the separator and using a material containing sodium-loving functional groups as the support material, thereby improving the cycle life of the negative electrode-free sodium metal battery.

[0167] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A sodium metal battery without a negative electrode, comprising a negative electrode current collector and a separator, characterized in that, At least one surface of the separator is provided with a support layer, the support layer covering a portion of the surface; wherein the support layer comprises a support material containing sodium-loving functional groups, and the support layer exists at least between the negative electrode current collector and the separator; The thickness of the support layer is 12-20 μm; the areal density of the support layer is 3.25 × 10⁻⁶. -4 ~3.25×10 -3 mg / mm 2 The support layer is distributed on the isolation membrane in a raised, grid-like, or striped pattern. The support layer also includes an elastic material to make the support layer elastic. The elastic material includes one or more of styrene thermoplastic elastomer, ethylene propylene diene monomer (EPDM) rubber, thermoplastic EPDM dynamically vulcanized elastomer, polyolefin thermoplastic elastomer, and thermoplastic polyester elastomer. The elastic material accounts for 15% to 30% of the mass of the support layer.

2. The sodium metal battery without a negative electrode according to claim 1, characterized in that, The sodium-loving functional group includes one or more of C=O, OH, and C≡N.

3. The sodium metal battery without a negative electrode according to claim 1 or 2, characterized in that, The support material comprises a polymer containing the sodium-loving functional groups.

4. The sodium metal battery without a negative electrode according to claim 3, characterized in that, The polymer includes one or more of carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, and polyacrylate.

5. The sodium metal battery without a negative electrode according to claim 1 or 2, characterized in that, The support material comprises a polymer modified with the sodium-loving functional groups.

6. The sodium metal battery without a negative electrode according to claim 5, characterized in that, The polymer includes one or more of polyvinylidene fluoride and styrene-butadiene rubber.

7. The sodium metal battery without a negative electrode according to claim 1 or 2, characterized in that, The support layer also includes inorganic materials.

8. The sodium metal battery without a negative electrode according to claim 7, characterized in that, The inorganic substances include one or more of Al2O3, SiO2, and Mg(OH)2.

9. The sodium metal battery without a negative electrode according to claim 1, characterized in that, The protrusions are island-shaped.

10. The sodium metal battery without a negative electrode according to claim 9, characterized in that, The shape of any single island structure is cylindrical, hemispherical, or spherical; the diameter of any single island structure is 5-50 μm.

11. A battery module, characterized in that, Including the sodium metal battery without a negative electrode as described in any one of claims 1-10.

12. A secondary battery pack, characterized in that, Includes the negative electrode-free sodium metal battery according to any one of claims 1-10 or the battery module according to claim 11.

13. An electrical appliance, characterized in that, It includes at least one of the following: the negative electrode-free sodium metal battery according to any one of claims 1-10, the battery module according to claim 11, and the secondary battery pack according to claim 12.

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