Sodium ion battery with stable structure

Abstract

The utility model discloses a sodium ion battery with a stable structure, which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, the positive plate comprises a positive current collector and a plurality of positive material layers coated on the surface of the positive current collector, and the number of the positive material layers is at least three. Comprising a first positive electrode material layer, a second positive electrode material layer and a third positive electrode material layer, the negative plate comprises a negative current collector and at least two layers of negative material layers coated on the surface of the negative current collector, and the multiple layers of negative material layers comprise a first negative material layer and a second negative material layer which are different in material type. The sodium ion battery with the stable structure has the characteristics of high structural stability, strong processability and high energy density.

Description

Technical Field

[0001] The utility model relates to the technical field of sodium ion batteries, and specifically refers to a sodium ion battery with a stable structure. Background Art

[0002] The working principle of sodium ion battery is similar to that of lithium ion battery. During the charging and discharging process, Na + Insertion and extraction back and forth between the two electrodes: During charging, Na + It is deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte; the opposite happens during discharge.

[0003] During the charge and discharge process of sodium-ion batteries, the electrode undergoes a certain volume change, causing the battery cell to swell and bulge, which is particularly noticeable in soft-pack batteries. Furthermore, the volume expansion is particularly pronounced in the middle of the battery cell, which is completely enclosed and lacks buffer space.

[0004] To address this, Chinese utility model patent CN220209008U discloses a sodium-ion battery with a porous structure. The positive electrode sheet of this sodium-ion battery has current collector blanks at both ends. A sodium-ion positive electrode coating layer is applied to the inner side of the current collector blanks, near the center of the current collector. The outer surface of the positive electrode coating layer is provided with a plurality of holes.

[0005] In this sodium-ion battery, although the holes are set to solve the serious expansion problem in the middle of the battery cell during the charging and discharging process of the sodium-ion battery, it effectively suppresses volume expansion and improves battery stability.

[0006] However, in actual manufacturing, the provision of this hole structure presents a number of operational issues for the production and processing of electrode sheets. For example, to increase energy density, both the positive and negative electrode sheets need to be rolled to increase their compaction density. The presence of holes creates rolling stress points, which creates the risk of electrode breakage. The rolling process also compresses or fills the holes, making it impossible to achieve the effect of the holes in suppressing volume expansion. Furthermore, providing holes after rolling results in severe damage to the electrode sheets due to the hollowing operation. All of these factors fully demonstrate the low operability and feasibility of providing hole structures in electrode sheets. Utility Model Content

[0007] The purpose of the utility model is to provide a sodium ion battery with a stable structure, which has the characteristics of high structural stability, strong processability and high energy density.

[0008] The utility model can be realized by the following technical solutions:

[0009] The utility model discloses a sodium ion battery with a stable structure, comprising a positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a multilayer positive electrode material layer coated on the surface of the positive electrode current collector, wherein the multilayer positive electrode material layer is at least three layers, including a first positive electrode material layer, a second positive electrode material layer, and a third positive electrode material layer of different material types; the negative electrode sheet comprises a negative electrode current collector and a multilayer negative electrode material layer coated on the surface of the negative electrode current collector, wherein the multilayer negative electrode material layer is at least two layers, including a first negative electrode material layer and a second negative electrode material layer of different material types.

[0010] Furthermore, the first positive electrode material layer, the second positive electrode material layer, and the third positive electrode material layer are different types of layered oxide material layers or polyanion material layers. Specifically, they can be different types of materials or different materials of the same type, thereby forming a pore size / pore gradient at the layer contact interface and forming an expansion buffer space.

[0011] Furthermore, the first negative electrode material layer and the second negative electrode material layer are a hard carbon material layer and a soft carbon material layer. In a multi-layer composite structure, the two materials can be alternately stacked to form multiple thin layers and buffer gaps.

[0012] Furthermore, the first, second, and third positive electrode material layers are sequentially coated, and a conductive adhesive layer is formed by vapor coating at the interface between the first, second, and third positive electrode material layers. This provides a non-directional coating method for forming the conductive adhesive layer, achieving both adhesive contact between the different layers and a certain gap, effectively ensuring a buffer gap for volume expansion.

[0013] Furthermore, the first and second negative electrode material layers are sequentially coated, and a conductive carbon layer is formed by vapor coating at the interface between the first and second negative electrode material layers. The conductive carbon layer enhances the interlayer gradient and increases porosity, ensuring a buffer space.

[0014] Furthermore, the thickness of the positive electrode sheet follows a gradient, with a thinner center and thicker ends. The thickness includes at least a first head thickness region, a middle thickness region, and a tail thickness region, with the middle thickness region being thinner than the head and tail thickness regions. This gradient thickness variation effectively offsets the effects of significant expansion in the center of the positive electrode sheet.

[0015] Furthermore, the thickness of the negative electrode sheet follows a gradient, with a thinner center and thicker ends. The sheet includes at least a first head coating region, a middle coating region, and a tail coating region. The middle coating region is thinner than the head and tail coating regions. This gradient effectively offsets the effects of significant expansion in the center of the negative electrode sheet.

[0016] Furthermore, the polyanion material layer is a sodium iron sulfate material layer or a composite sodium iron phosphate material layer. Of course, it can also be other polyanion positive electrode materials, and only two more common types are listed here.

[0017] Furthermore, the positive electrode current collector and the negative electrode current collector are aluminum foil, aluminum mesh, copper foil or copper mesh, and different types of foils or meshes can meet actual use requirements.

[0018] Furthermore, the sodium ion battery is a cylindrical steel shell battery, a square soft pack battery or a square aluminum shell battery, and different types of batteries can be prepared according to actual needs.

[0019] The utility model provides a sodium ion battery with a stable structure, which has the following beneficial effects:

[0020] First, the structure is highly stable. The positive electrode sheet of the present invention adopts a multi-layer composite positive electrode material layer structure, forming multiple thin layers of positive electrode material layers. Each positive electrode material layer has different pore sizes and porosities, thereby forming a buffer space between layers and a number of buffer gaps between multiple layers, thereby reducing the impact of volume expansion of each layer and effectively improving structural stability. Based on this, the negative electrode sheet adopts such a structural design to prevent the impact of volume expansion on battery performance from the positive and negative electrode sheets as a whole.

[0021] Second, the processing is simple. Both the positive and negative electrode sheets adopt a multi-layer composite structure. During the coating process, only layer coating is required. Each material layer can use the existing coating and homogenization process, which improves the operability of the electrode coating. At the same time, since there are no holes, the electrode sheets will not be affected during the rolling process. The gap between the layers still exists after rolling, which will not affect the expansion performance.

[0022] Third, the energy density is high. By setting up a multi-layer composite structure, there is no need to process the hole structure in the middle of the electrode, which will not cause waste of the hole structure volume. After rolling, the positive electrode material layer and the negative electrode material layer fully utilize the space of the electrode and improve the energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Attachment Figure 1 This is a schematic structural diagram of a sodium ion battery with a stable structure according to the present invention;

[0024] The marks in the accompanying drawings include: 100, positive electrode sheet; 110, positive electrode current collector; 120, first positive electrode material layer; 130, second positive electrode material layer; 130, third positive electrode material layer; 200, separator; 300, negative electrode sheet; 310, negative electrode current collector; 320, first negative electrode material layer; 330, second negative electrode material layer. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in further detail below in conjunction with embodiments.

[0026] like Figure 1 As shown, the utility model discloses a sodium ion battery with stable structure, including a positive electrode sheet 100, a negative electrode sheet 300 and a separator 200 arranged between the positive electrode sheet 100 and the negative electrode sheet 300. The positive electrode sheet 100 includes a positive electrode collector 110 and a multilayer positive electrode material layer coated on the surface of the positive electrode collector 110. The multilayer positive electrode material layer is at least three layers, including a first positive electrode material layer 120, a second positive electrode material layer 130, and a third positive electrode material layer 140 of different material types; the negative electrode sheet 300 includes a negative electrode collector 310 and a multilayer negative electrode material layer coated on the surface of the negative electrode collector. The multilayer negative electrode material layer is at least two layers, including a first negative electrode material layer 320 and a second negative electrode material layer 330 of different material types. Figure 1 In the figure, only one cross-section or stacked structure is shown. This structure is applicable to both cylindrical wound batteries and laminated batteries, with only differences in display and explanation angles. Moreover, the negative and positive sides of the positive and negative current collectors are both provided with corresponding material layers, which is consistent with existing actual production. In addition, although the positive electrode sheet is only shown with three layers here, it is not limited to this in practice. The same is true for the negative electrode sheet. The core lies in forming a buffer space by forming a pore size / pore gradient through the material science of multiple thin layers.

[0027] In the present invention, to create a gap gradient in material selection, the first, second, and third positive electrode material layers are composed of different types of layered oxide material layers or polyanion material layers. Similarly, the first and second negative electrode material layers are composed of hard carbon material layers and soft carbon material layers. Specifically, the polyanion material layer is composed of sodium iron sulfate or composite sodium iron phosphate.

[0028] In the present invention, to create a buffer gap in the interlayer structure, a first positive electrode material layer, a second positive electrode material layer, and a third positive electrode material layer are sequentially coated, and a conductive adhesive layer is formed by vapor coating at the contact interface of the first, second, and third positive electrode material layers. Finally, a first negative electrode material layer and a second negative electrode material layer are sequentially coated, and a conductive carbon layer is formed by vapor coating at the contact interface of the first and second negative electrode material layers.

[0029] At the same time, the present invention also improves buffer space in terms of thickness structure control. The thickness of the positive electrode sheet varies in a gradient, with a thin center and thick ends, including at least a first head thickness region, a middle thickness region, and a tail thickness region. The middle thickness region is thinner than the head and tail thickness regions. Similarly, the thickness of the negative electrode sheet varies in a gradient, with a thin center and thick ends, including at least a first head coating region, a middle coating region, and a tail coating region. The middle coating region is thinner than the head and tail coating regions.

[0030] The utility model has no special limitation on the applicability of the current collector. Furthermore, the positive electrode current collector and the negative electrode current collector are aluminum foil, aluminum mesh, copper foil or copper mesh.

[0031] As mentioned above, Figure 1 According to the description, sodium-ion batteries are cylindrical steel-shell batteries, square soft-pack batteries or square aluminum-shell batteries.

[0032] In the description of the present invention, it should be understood that terms such as "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] Furthermore, 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 the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0034] In this utility model, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, indirect connection through an intermediate medium, internal communication between two components, or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on specific circumstances.

[0035] The above embodiments are merely specific embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art will be able to make various modifications and improvements without departing from the scope of the present invention, and these obvious alternatives are all within the scope of protection of the present invention.

Claims

1. A sodium ion battery with a stable structure, comprising a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet, characterized in that: The positive electrode sheet includes a positive electrode current collector and a multilayer positive electrode material layer coated on the surface of the positive electrode current collector, and the multilayer positive electrode material layer is at least three layers, including a first positive electrode material layer, a second positive electrode material layer, and a third positive electrode material layer of different material types; the negative electrode sheet includes a negative electrode current collector and a multilayer negative electrode material layer coated on the surface of the negative electrode current collector, and the multilayer negative electrode material layer is at least two layers, including a first negative electrode material layer and a second negative electrode material layer of different material types.

2. The structurally stable sodium ion battery according to claim 1, characterized in that: The first positive electrode material layer, the second positive electrode material layer, and the third positive electrode material layer are different types of layered oxide material layers or polyanion material layers.

3. The structurally stable sodium ion battery according to claim 2, characterized in that: The first negative electrode material layer and the second negative electrode material layer are a hard carbon material layer and a soft carbon material layer.

4. The structurally stable sodium ion battery according to claim 3, characterized in that: The first positive electrode material layer, the second positive electrode material layer and the third positive electrode material layer are coated in sequence, and a conductive adhesive layer is formed by vapor coating on the contact interface of the first positive electrode material layer, the second positive electrode material layer and the third positive electrode material layer.

5. The structurally stable sodium ion battery according to claim 4, characterized in that: The first negative electrode material layer and the second negative electrode material layer are coated in sequence, and a conductive carbon layer is formed by vapor coating at the contact interface between the first negative electrode material layer and the second negative electrode material layer.

6. The structurally stable sodium ion battery according to claim 5, characterized in that: The thickness of the positive electrode sheet changes in a gradient from thin in the middle to thick at both ends, and includes at least a first head thickness area, a middle thickness area and a tail thickness area, and the thickness of the middle thickness area is smaller than that of the head thickness area and the tail thickness area.

7. The structurally stable sodium ion battery according to claim 6, characterized in that: The thickness of the negative electrode sheet changes gradually from thin in the middle to thick at both ends, and includes at least a first head coating area, a middle coating area and a tail coating area. The thickness of the middle coating area is smaller than that of the head coating area and the tail coating area.

8. The structurally stable sodium ion battery according to claim 7, characterized in that: The polyanion material layer is a sodium iron sulfate material layer or a composite sodium iron phosphate material layer.

9. The structurally stable sodium ion battery according to claim 8, characterized in that: The positive electrode current collector and the negative electrode current collector are aluminum foil, aluminum mesh, copper foil or copper mesh.

10. The structurally stable sodium ion battery according to claim 9, characterized in that: The sodium ion battery is a cylindrical steel shell battery, a square soft pack battery or a square aluminum shell battery.

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