All-solid-state sodium metal battery

Abstract

The utility model provides an all-solid-state sodium metal battery and belongs to the technical field of solid-state batteries. The solid-state battery comprises a shell, a positive pole piece and a negative pole piece, wherein the positive pole piece and the negative pole piece are arranged in the shell and are alternately laminated. Wherein the positive pole piece comprises a positive pole lug; the centers of the left and right sides of the positive current collector are contacted with the positive tab; the positive active material layers are coated on the upper and lower surfaces of the positive current collector; and the solid electrolyte layer is coated on the surface of one side, far away from the positive current collector, of the positive active material layer. The negative pole piece comprises a negative pole lug; the centers of the left and right sides of the negative current collector are in contact with the negative tabs; and the sodium metal covers the upper and lower surfaces of the negative current collector. The sodium metal solid-state battery provided by the utility model has good ionic conductivity, interface compatibility and stable cycle performance, can reduce internal resistance, inhibits sodium metal from forming dendritic crystals, and effectively prevents the occurrence of a short circuit phenomenon.

Description

Technical Field

[0001] The utility model relates to the technical field of sodium metal batteries, in particular to an all-solid-state sodium metal battery. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, but due to the limited supply and high cost of lithium resources, they will be unlikely to meet all future demand. Sodium-ion batteries have emerged as a potential alternative. However, sodium ions have a much larger mass and radius than lithium ions, resulting in a lower energy density for sodium-ion batteries. To further increase the energy density of sodium-ion batteries, sodium metal batteries, using sodium metal as the negative electrode, are an effective approach.

[0003] However, the spontaneous and irreversible reaction between the liquid electrolyte and sodium metal forms a rough and loose solid electrolyte interface layer. This unstable solid electrolyte layer is easily damaged by repeated charge and discharge, continuously consuming electrolyte and active sodium. The uneven solid electrolyte layer and surface cracks after damage lead to uneven sodium deposition, gradually forming "sodium dendrites" in the uneven areas. On the one hand, these sodium dendrites easily fall off and then enter the solid electrolyte layer, becoming "dead sodium" and dispersing near the electrolyte / anode interface, greatly increasing the interfacial impedance, consuming the amount of reversible sodium metal, and causing battery performance to deteriorate. On the other hand, because some sharp sodium dendrites continue to grow uncontrollably in the electrolyte, they are affected by the "tip effect", that is, the strong electric field is concentrated around their tips, promoting further growth of the dendrites. They will eventually penetrate the polymer separator and short-circuit the battery, causing thermal runaway, posing a safety hazard of fire and leakage. In addition, at low temperatures, the desolvation of sodium ions in traditional ester electrolytes is very difficult. Therefore, solid-state sodium metal batteries that use solid electrolytes instead of liquid electrolytes can operate safely and stably in a wider temperature range, and their higher mechanical strength can prevent dendrite penetration.

[0004] Some existing solid electrolytes have already exhibited sufficiently high ionic conductivity at room temperature, but the poor interfacial compatibility between the solid electrolyte and the electrode hinders the transport of sodium ions, increases the interfacial resistance, and limits the practical application of sodium metal batteries. Utility Model Content

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and in the abstract and title of the utility model to avoid obscuring the purpose of this section, the abstract and the title of the utility model, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the above problems in the prior art, the present utility model is proposed.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: an all-solid-state sodium metal battery, comprising: a positive electrode sheet and a negative electrode sheet, which are alternately stacked;

[0008] The positive electrode sheet includes: a positive electrode tab and a positive electrode current collector, and the centers of the left and right sides of the positive electrode current collector are in contact with the positive electrode tab;

[0009] A positive electrode active material layer coated on the upper and lower surfaces of the positive electrode current collector;

[0010] and a solid electrolyte layer coated on a surface of the positive electrode active material layer away from the positive electrode current collector;

[0011] The negative electrode sheet includes: a negative electrode tab and a negative electrode current collector, and the centers of the left and right sides of the negative electrode current collector are in contact with the negative electrode tab;

[0012] and sodium metal, which covers the upper and lower surfaces of the negative electrode current collector.

[0013] As a preferred solution of the all-solid-state sodium metal battery described in the present invention, the positive electrode current collector is aluminum foil.

[0014] As a preferred solution of the all-solid-state sodium metal battery described in the present invention, the width of the contact portion between the positive electrode current collector and the positive electrode tab is the same as the width of the positive electrode tab.

[0015] As a preferred embodiment of the all-solid-state sodium metal battery of the present invention, the active material in the positive electrode active material layer is selected from one of layered metal oxides, polyanion compounds and Prussian blue / white analogs.

[0016] As a preferred embodiment of the all-solid-state sodium metal battery of the present invention, the surface density of the positive electrode active material layer (201) is 2.5 mg / cm 2 Up to 50mg / cm 2 .

[0017] As a preferred solution of the all-solid-state sodium metal battery of the utility model, wherein: the surface density of the solid electrolyte layer (202) is 3 mg / cm 2 Up to 50mg / cm 2 .

[0018] As a preferred solution of the all-solid-state sodium metal battery described in the present invention, the negative electrode current collector is aluminum foil.

[0019] As a preferred solution of the all-solid-state sodium metal battery described in the present invention, the width of the contact portion between the negative electrode current collector and the negative electrode tab is the same as the width of the negative electrode tab (300).

[0020] As a preferred solution of the all-solid-state sodium metal battery described in the present invention, the outer layer of the battery is provided with a shell, which is any one of an aluminum-plastic film, an aluminum shell or a steel shell that wraps the positive electrode sheet and the negative electrode sheet.

[0021] The beneficial effects of the present invention are as follows: the present invention adopts a technical solution of coating the positive electrode active material and the solid electrolyte on the positive electrode sheet, which can effectively improve the interface compatibility between the solid electrolyte and the electrode, reduce the internal resistance, improve the ionic conductivity and cycle performance, inhibit the formation of sodium metal dendrites, and effectively prevent the occurrence of short circuit phenomena. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. Among them:

[0023] Figure 1 This is a schematic cross-sectional view of the positive and negative electrode sheets of an all-solid-state sodium metal battery proposed in the present invention. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below with reference to the accompanying drawings.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] Furthermore, this utility model is described in detail with schematic diagrams. For ease of illustration, when describing embodiments of this utility model, cross-sectional views of device structures may be partially enlarged and not to scale. Furthermore, these schematic diagrams are merely illustrative and should not limit the scope of protection of this utility model. Furthermore, in actual production, the three-dimensional dimensions of length, width, and depth should be included.

[0028] Reference Figure 1 , which is an embodiment of the present invention, provides an all-solid-state sodium metal battery, the metal battery comprising: a positive electrode sheet and a negative electrode sheet, and the two are alternately stacked;

[0029] The positive electrode sheet includes: a positive electrode tab 100 and a positive electrode current collector 200, and the centers of the left and right sides of the positive electrode current collector (200) are in contact with the positive electrode tab 100;

[0030] The positive electrode active material layer 201 is coated on the upper and lower surfaces of the positive electrode current collector 200 ; and the solid electrolyte layer 202 is coated on the surface of the positive electrode active material layer 201 away from the positive electrode current collector 200 .

[0031] The negative electrode sheet includes: a negative electrode tab 300, a negative electrode current collector 400, and the centers of the left and right sides of the negative electrode current collector (400) are in contact with the negative electrode tab 300; and sodium metal 401, which covers the upper and lower surfaces of the negative electrode current collector 400.

[0032] The materials of each layer can be but are not limited to existing materials, and the process can be but are not limited to existing processes.

[0033] Specifically, in the present invention, both the positive electrode current collector and the negative electrode current collector are aluminum foil, and the aluminum foil can be single-sided rough aluminum foil or double-sided rough aluminum foil to ensure good interface compatibility between the active material and the current collector.

[0034] In the present invention, the positive electrode active material includes but is not limited to layered metal oxides, polyanionic materials, Prussian blue / white analogs. Specifically, for example, NaNi x Fe y Mn z O2、NaNi x Fe y Mn z O2、NaNi x Mn y O2、NaFe x Mn y O2、Na3V2PO 43 , NaFeP2O7, NaFeSiO4, NaFeSO4 and A x M[M'CN6] 1-y ·□y nH2O, etc. Among them, x, y, and z are positive numbers. x Fe y Mn z In O2, x+y+z=1; in NaNi x Mn y O2 and NaFe x Mn y In O2, x+y=1; in A x M[M'CN6] 1-y ·□ y In nH2O, A is an alkali metal, x≤2, M and M' are metals in high-spin and low-spin states, respectively, and □ is a vacancy created by water occupying a position that should have been C≡N.

[0035] In the present invention, the positive electrode active material layer is formed by coating the prepared positive electrode slurry on the positive electrode current collector. After coating the positive electrode active material layer, the solid electrolyte layer slurry is coated along the positive electrode active material layer. Part of the slurry is mixed in the middle part of the positive electrode active material layer and the solid electrolyte, which can improve the interface compatibility between the electrolyte and the positive electrode sheet, reduce the interface resistance, and improve the ion conduction efficiency.

[0036] In the present invention, solid electrolytes include but are not limited to inorganic solid electrolytes Na3Zr2Si2PO 12 , Na3PS4, β-Al2O3, polymer solid electrolytes and composite solid electrolytes. The polymer solid electrolyte consists of a polymer solvent and a sodium salt soluble in the polymer. In order to synthesize a high-conductivity polymer solid electrolyte, the sodium salt should have good solubility, thermal stability and electrochemical stability, including but not limited to NaTFSI, NaPF6, NaClO4, NaBF4 and NaFSI; polymers include but are not limited to polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl pyrrolidone, polyvinyl alcohol, polymethyl acrylate and polyacrylonitrile. Polymer solid electrolytes have the characteristics of simple processing, strong film forming ability and low interfacial resistance, which contribute to the safety and electrochemical performance of solid-state sodium metal batteries. Composite solid electrolytes combine the high electronic conductivity of inorganic electrolytes with the toughness of polymer solid electrolytes, which can greatly improve the interfacial compatibility between the electrolyte and the electrode, inhibit the growth of dendrites and the occurrence of side reactions, and promote the transport of sodium ions.

[0037] As an illustration of this embodiment, the steps of this embodiment can be implemented using the following technical solutions:

[0038] S1: Prepare positive electrode material slurry.

[0039] The positive electrode active material, a certain amount of binder (including but not limited to polyvinylidene fluoride), and a conductive agent (including but not limited to conductive carbon black) are added to nitrogen methyl polypropane ketone (commonly known as NMP), and then mixed evenly in a blender to obtain a positive electrode material slurry.

[0040] S2: coating of positive electrode material.

[0041] The prepared positive electrode material slurry is coated on the upper and lower surfaces of the positive electrode current collector 200 by a coating machine, and dried in a drying machine to form the positive electrode active material layer 201 .

[0042] S3: coating a solid electrolyte layer 202 .

[0043] The solid electrolyte, organic polymer, sodium salt and binder are dissolved in NMP, stirred and mixed evenly in a vacuum environment, and the obtained solution is coated on the positive electrode active material layer 201 on both surfaces of the positive electrode plate.

[0044] S4: Prepare the negative electrode sheet.

[0045] Sodium metal 401 is coated on the upper and lower surfaces of the negative electrode current collector 400 and integrally rolled in a vacuum environment or an inert atmosphere.

[0046] After the positive electrode sheet and the negative electrode sheet are prepared, they are further integrated by roll-forming. The roll-forming is performed in an inert atmosphere.

[0047] It can be seen from the above that the sodium metal solid-state battery prepared by the process of this embodiment can not only solve the problem of poor interface compatibility between the solid electrolyte and the electrode, but also inhibit the growth of sodium dendrites and solve the problem of solid-state battery failure caused by puncture.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the claims of the present invention.

Claims

1. An all-solid-state sodium metal battery, characterized in that: include: Positive electrode sheets and negative electrode sheets, which are alternately stacked; The positive electrode sheet comprises: a positive electrode tab (100) and a positive electrode current collector (200), and the centers of the left and right sides of the positive electrode current collector (200) are in contact with the positive electrode tab (100); A positive electrode active material layer (201) coated on the upper and lower surfaces of the positive electrode current collector (200); and a solid electrolyte layer (202) coated on a surface of the positive electrode active material layer (201) away from the positive electrode current collector (200); The negative electrode plate comprises: a negative electrode tab (300) and a negative electrode current collector (400), and the centers of the left and right sides of the negative electrode current collector (400) are in contact with the negative electrode tab (300); and sodium metal (401), which covers the upper and lower surfaces of the negative electrode current collector (400).

2. The all-solid-state sodium metal battery according to claim 1, characterized in that: The positive electrode current collector (200) is aluminum foil.

3. The all-solid-state sodium metal battery according to claim 1, characterized in that: The width of the contact portion between the positive electrode current collector (200) and the positive electrode tab (100) is the same as the width of the positive electrode tab (100).

4. The all-solid-state sodium metal battery according to claim 1, characterized in that: The surface density of the positive electrode active material layer (201) is 2.5 mg / cm 2 Up to 50mg / cm 2 .

5. The all-solid-state sodium metal battery according to claim 1, characterized in that: The surface density of the solid electrolyte layer (202) is 3 mg / cm 2 Up to 50mg / cm 2 .

6. The all-solid-state sodium metal battery according to claim 1, characterized in that: The negative electrode current collector (400) is aluminum foil.

7. The all-solid-state sodium metal battery according to claim 1, characterized in that: The width of the contact portion between the negative electrode current collector (400) and the negative electrode tab (300) is the same as the width of the negative electrode tab (300).

8. The all-solid-state sodium metal battery according to claim 1, characterized in that: The outer layer of the battery is provided with a shell, which is any one of an aluminum-plastic film, an aluminum shell or a steel shell that wraps the positive electrode sheet and the negative electrode sheet.

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