Sodium ion battery monomer, battery and power utilization device

Abstract

The invention discloses a sodium ion battery monomer, a battery and a power utilization device. The sodium ion battery cell comprises a shell, a pressure relief mechanism and an electrode assembly. The shell has an accommodating cavity. The pressure relief mechanism is arranged on the shell. The electrode assembly is accommodated in the accommodating cavity and comprises a main body part and a tab; the tab is led out from the end part of the main body part along the first direction; the rated energy of the sodium ion battery monomer is En, the sectional area, perpendicular to the first direction, of the accommodating cavity is S1, the sectional area, perpendicular to the first direction, of the main body part is S2, the number of the electrode assemblies is k, and k is a positive integer. The unit of En is Wh, and the units of S1 and S2 are both mm < 2 >. En, S1, k, and S2 satisfy 0.3 Wh / mm < 2 > < = En / (S1-k * S2) < = 7 Wh / mm < 2 >.

Description

Technical Field

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

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. At present, lithium-ion batteries still occupy the core position of batteries, and lithium-ion batteries also face great challenges, such as the increasing shortage of lithium resources. Sodium resources are far more abundant than lithium resources, are more widely distributed, and have a much lower cost than lithium. Therefore, sodium-ion batteries have become a new generation of electrochemical systems with great potential to replace lithium-ion batteries.

[0003] How to improve the reliability of sodium-ion batteries is an important research direction in the industry. Summary of the invention

[0004] The present application provides a sodium ion battery cell, a battery and an electrical device, which can improve reliability.

[0005] In a first aspect, the present application provides a sodium ion battery cell, which includes a shell, a pressure relief mechanism and an electrode assembly. The shell has a accommodating cavity. The pressure relief mechanism is arranged on the shell. The electrode assembly is accommodated in the accommodating cavity and includes a main body and a pole ear, and the pole ear is led out from the end of the main body along a first direction. The rated energy of the sodium ion battery cell is En, the cross-sectional area of ​​the accommodating cavity perpendicular to the first direction is S1, the cross-sectional area of ​​the main body perpendicular to the first direction is S2, and the number of electrode assemblies is k, where k is a positive integer. The unit of En is Wh, and the units of S1 and S2 are both mm 2 . En, S1, k and S2 meet: 0.3Wh / mm 2 ≤En / (S1-k×S2)≤7Wh / mm 2 .

[0006] The embodiment of the present application limits the value of En / (S1-k×S2) to less than or equal to 7Wh / mm 2 , in order to increase the gas discharge rate when the sodium ion battery cell experiences thermal runaway, reduce the risk of rupture and explosion of the sodium ion battery cell, and improve the reliability of the sodium ion battery cell. The embodiment of the present application also limits the value of En / (S1-k×S2) to be greater than or equal to 0.3Wh / mm 2 , in order to reduce the loss of space utilization of sodium-ion battery cells while reducing the risk of explosion of sodium-ion battery cells, and balance the reliability and energy density of sodium-ion battery cells.

[0007] In some embodiments, En, S1, k, and S2 satisfy: 0.9Wh / mm 2 ≤En / (S1-k×S2)≤5Wh / mm 2 , in order to further balance the reliability and energy density of sodium-ion battery cells, reduce the risk of battery cell shell rupture, allow gas to be discharged from a set area, and reduce the loss of energy density.

[0008] In some embodiments, the area of ​​the pressure relief mechanism is S3. (S1-k×S2) / S3 is 0.5-7. The embodiments of the present application can improve the efficiency of gas discharge from the pressure relief mechanism, limit the range of gas after being ejected from the pressure relief mechanism, and reduce the risk of heat spread.

[0009] In some embodiments, (S1-k×S2) / S3 is 0.8-6.5.

[0010] In some embodiments, the housing includes a shell and an end cover, the end of the shell along the first direction has an opening, and the end cover covers the opening. The pressure relief mechanism is disposed on the end cover.

[0011] The pressure relief mechanism can be opposite to the main body along the first direction, so that the reaction time of the pressure relief mechanism can be shortened when the sodium ion battery cell thermally runs away, the pressure can be relieved in time, and the reliability of the sodium ion battery cell can be improved.

[0012] In some embodiments, the electrode assembly is a winding structure. The main body includes a straight area and two bending areas, and the two bending areas are respectively located on both sides of the straight area along a second direction, and the second direction is perpendicular to the first direction.

[0013] In the second direction, a channel can be formed between the shell and the bending area to facilitate gas flow when the sodium ion battery cell is in thermal runaway. By setting the bending area, the flow capacity of the channel can be enhanced.

[0014] In some embodiments, the electrode assembly includes a first pole piece, a second pole piece, and a separator, the first pole piece and the second pole piece have opposite polarities, the separator insulates the first pole piece and the second pole piece, and the first pole piece, the second pole piece, and the separator are wound. The first pole piece and the second pole piece each include a plurality of bending layers located in a bending zone. In the bending zone, at least two bending layers from the outside to the inside are first bending layers provided with through holes.

[0015] When the main body generates gas internally due to thermal runaway, the gas can be discharged through the through hole to the channel between the bending area and the outer shell, thereby exhausting the gas in time, reducing the risk of fire and explosion of the battery cell and improving reliability.

[0016] In some embodiments, the bending area is provided with a recessed portion, which is sunken from the outer surface of the bending area and penetrates at least two bending layers. By providing the recessed portion, when the main body generates gas internally due to thermal runaway, the gas inside the main body can be discharged in time, thereby reducing the risk of fire and explosion of the battery cell and improving reliability.

[0017] In some embodiments, the dimension of the main body along the first direction is h. In the first direction, the minimum distance between the recess and one end of the main body is D1, and 1 / 3h≤D1≤2 / 3h.

[0018] When thermal runaway occurs, the area close to the end of the bending zone along the first direction can be vented through the end without setting a recess; setting the recess in the middle area of ​​the bending zone along the first direction can not only allow the middle area of ​​the bending zone to be vented outwardly through the recess, but also reduce the number of recesses, reduce the loss of pole piece strength, and reduce the risk of deformation of the bending zone.

[0019] In some embodiments, the total number of bending layers in the bending zone is m1, the number of first bending layers is m2, and m2 / m1≥0.5. The first bending layer with through holes has more layers, and can also be quickly exhausted when the short-circuit point of the main body is close to the inside.

[0020] In some embodiments, in the straight region, the first pole piece and the second pole piece are stacked along a third direction, the third direction being perpendicular to the first direction and the second direction. In the third direction, a distance D2 between adjacent first pole pieces and second pole pieces is 10 μm-40 μm.

[0021] Limiting D2 to be greater than or equal to 10 μm can increase the spacing between the first pole piece and the second pole piece, reduce the heat transfer rate, and reduce the gas generation of the electrode assembly in thermal runaway. Limiting D2 to be less than or equal to 40 μm can reduce the difficulty of ion migration and reduce the risk of sodium precipitation on the pole piece surface.

[0022] In some embodiments, the isolating member is provided with a convex portion in the straight region. By providing the convex portion on the isolating member, the distance between the first pole piece and the second pole piece can be increased.

[0023] In some embodiments, the electrode assembly includes a first pole piece, a second pole piece and a separator, the first pole piece and the second pole piece have opposite polarities, and the separator insulates the first pole piece and the second pole piece. A surface of at least one of the first pole piece, the second pole piece and the separator is provided with a high temperature resistant coating.

[0024] By providing a high-temperature resistant coating, the heat transfer after the pole piece combustion can be slowed down to a certain extent, the heat resistance of the pole piece or the separator can be enhanced, the gas production can be reduced, and the risk of explosion of the sodium-ion battery cell can be reduced.

[0025] In some embodiments, the electrode assembly includes a positive electrode active material, and the positive electrode active material includes at least one of a Prussian blue-based positive electrode material, a layered oxide-based positive electrode material, or a polyanion-based positive electrode material.

[0026] In some embodiments, k is 2-4, so as to reduce the loss of space utilization of the sodium ion battery monomer and balance the reliability and energy density of the sodium ion battery monomer while reducing the risk of explosion of the sodium ion battery monomer.

[0027] In a second aspect, an embodiment of the present application provides a battery comprising a plurality of sodium ion battery cells provided by any embodiment of the first aspect.

[0028] In a third aspect, an embodiment of the present application provides an electrical device, which includes a battery provided according to the second aspect, and the battery is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0030] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0031] Figure 2 An exploded schematic diagram of a battery provided in some embodiments of the present application;

[0032] Figure 3 An explosion diagram of a sodium ion battery cell provided in some embodiments of the present application;

[0033] Figure 4 A schematic cross-sectional view of a sodium ion battery cell provided in some embodiments of the present application;

[0034] Figure 5 A schematic diagram of an electrode assembly of a sodium ion battery cell provided in some embodiments of the present application;

[0035] Figure 6 for Figure 5 Schematic diagram of the cross section along the AA direction;

[0036] Figure 7 for Figure 6 An enlarged schematic diagram at the circle frame;

[0037] Figure 8 A partial cross-sectional schematic diagram of an electrode assembly of a sodium ion battery cell provided in some embodiments of the present application;

[0038] Fig. 9 A schematic cross-sectional view of a first pole piece of a sodium ion battery cell provided in some embodiments of the present application.

[0039] The following are the descriptions of the reference numerals:

[0040] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodation space; 6. Sodium ion battery cell;

[0041] 10. electrode assembly; 11. main body; 11a. straight area; 11b. bending area; 11c. concave portion; 12. pole ear; 121. positive pole ear; 122. negative pole ear; 13. first pole piece; 131. first current collector; 132. first active material layer; 14. second pole piece; 15. separator; 151. convex portion; 152. concave cavity; 16. bending layer; 16a. first bending layer; 16b. through hole; 17. high temperature resistant coating;

[0042] 20. housing; 20a. accommodating chamber; 21. shell; 22. end cover;

[0043] 30. Pressure relief mechanism;

[0044] 40. Electrode terminal;

[0045] Z, first direction; X, second direction; Y, third direction. DETAILED DESCRIPTION

[0046] Below, the embodiments of the sodium ion battery cell, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0047] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0049] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0051] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0052] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0053] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0054] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0055] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured by various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0056] A battery cell may be the smallest unit that can independently realize the functions of charging and discharging.

[0057] A battery cell generally includes an electrode assembly, which includes a positive electrode and a negative electrode. Taking a sodium-ion battery cell as an example, during the charge and discharge process of the battery cell, sodium ions are inserted and removed back and forth between the positive electrode and the negative electrode.

[0058] In some embodiments, the electrode assembly further includes an isolating member disposed between the positive electrode and the negative electrode. The isolating member can prevent the positive and negative electrodes from short-circuiting while allowing sodium ions to pass through.

[0059] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a polygonal battery, such as a hexagonal battery, etc. There is no special limitation in this application.

[0060] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0061] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0062] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0063] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0064] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0065] The development of battery technology must take into account many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate and other performance parameters. In addition, battery reliability must also be considered.

[0066] The pressure relief mechanism on the battery cell has an important impact on the reliability of the battery cell. For example, when a short circuit or overcharge occurs, thermal runaway may occur inside the battery cell, causing a sudden increase in pressure. In this case, the pressure relief mechanism can be activated to release the internal pressure to the outside, thereby reducing the risk of battery cell explosion and fire.

[0067] Sodium-ion battery cells produce gas more violently during thermal runaway, and the gas inside the battery cells is prone to poor flow, resulting in the gas being unable to be discharged from the pressure relief mechanism in a timely manner, causing the risk of rupture of the battery cell shell and causing heat spread, affecting the reliability of the battery.

[0068] In view of this, an embodiment of the present application provides a technical solution, which adjusts the rated energy of the sodium-ion battery cell and the internal space of the sodium-ion battery cell to reduce the risk of battery cell rupture and explosion when the battery cell thermal runaways and improve the reliability of the battery cell.

[0069] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application.

[0070] like Figure 1 As shown, a battery 2 is disposed inside the vehicle 1, and the battery 2 may be disposed at the bottom, head, or tail of the vehicle 1. The battery 2 may be used to power the vehicle 1, for example, the battery 2 may be used as an operating power source for the vehicle 1.

[0071] The vehicle 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery 2 to supply power to the motor 4 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1 .

[0072] In some embodiments of the present application, the battery 2 can not only serve as an operating power source for the vehicle 1, but also serve as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0073] Figure 2 Schematic diagram of an explosion of a battery provided in some embodiments of the present application. Figure 2 As shown, the battery 2 includes a housing 5 and a sodium-ion battery cell 6 , and the sodium-ion battery cell 6 is accommodated in the housing 5 .

[0074] The box 5 is used to accommodate the sodium ion battery monomer 6, and the box 5 can be a variety of structures. In some embodiments, the box 5 can include a first box portion 5a and a second box portion 5b, the first box portion 5a and the second box portion 5b cover each other, and the first box portion 5a and the second box portion 5b jointly define a storage space 5c for accommodating the sodium ion battery monomer 6. The second box portion 5b can be a hollow structure with one end open, the first box portion 5a is a plate-like structure, and the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c; the first box portion 5a and the second box portion 5b can also be a hollow structure with one side open, and the open side of the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c. Of course, the first box portion 5a and the second box portion 5b can be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0075] In order to improve the sealing performance after the first box body part 5a and the second box body part 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body part 5a and the second box body part 5b.

[0076] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box.

[0077] In the battery 2, the sodium ion battery cell 6 can be one or more. If there are more than one sodium ion battery cell 6, the more than one sodium ion battery cell 6 can be connected in series, in parallel, or in mixed connection. Mixed connection means that the more than one sodium ion battery cell 6 is connected in series and in parallel. The more than one sodium ion battery cell 6 can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the more than one sodium ion battery cell 6 is accommodated in the box 5; of course, the more than one sodium ion battery cell 6 can be first connected in series, in parallel, or in mixed connection to form a battery module, and then the more than one battery module is connected in series, in parallel, or in mixed connection to form a whole, and then accommodated in the box 5.

[0078] Figure 3 Schematic diagram of an explosion of a sodium ion battery cell provided in some embodiments of the present application, Figure 4 A schematic cross-sectional view of a sodium ion battery cell provided in some embodiments of the present application.

[0079] like Figure 3 and Figure 4 As shown, an embodiment of the present application provides a sodium ion battery cell 6, which includes a housing 20 and an electrode assembly 10, wherein the housing 20 has a receiving cavity 20a, and the electrode assembly 10 is received in the receiving cavity 20a of the housing 20.

[0080] The electrode assembly 10 is a component where electrochemical reactions occur in the sodium ion battery cell 6. One or more electrode assemblies 10 may be contained in the housing 20.

[0081] The electrode assembly 10 may be a wound structure, a laminated structure, or other structures.

[0082] The housing 20 is a hollow structure, and a space for accommodating the electrode assembly 10 and the electrolyte is formed therein. The shape of the housing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a rectangular parallelepiped structure, a rectangular housing can be selected; if the electrode assembly 10 is a cylindrical structure, a cylindrical housing can be selected.

[0083] The housing 20 may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing) or an aluminum-plastic film.

[0084] As an example, the housing 20 includes a shell 21 and an end cover 22 . The shell 21 has an opening, and the end cover 22 is used to cover the opening.

[0085] The housing 21 is a component used to cooperate with the end cover 22 to form an internal cavity of the sodium ion battery cell 6. The formed internal cavity can be used to accommodate the electrode assembly 10, electrolyte and other components.

[0086] The housing 21 and the end cap 22 may be independent components. For example, an opening may be provided on the housing 21, and the end cap 22 may cover the opening to form an internal cavity of the sodium ion battery cell 6.

[0087] The shell 21 can be in various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism shape, etc. Specifically, the shape of the shell 21 can be determined according to the specific shape and size of the electrode assembly 10. The shell 21 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0088] The shape of the end cap 22 can be adapted to the shape of the housing 21 to match the housing 21. The material of the end cap 22 can be the same as or different from the material of the housing 21. Optionally, the end cap 22 can be made of a material with a certain hardness and strength (e.g., copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.), so that the end cap 22 is not easily deformed when squeezed and collided, so that the sodium ion battery cell 6 can have a higher structural strength and the reliability performance can also be improved.

[0089] The end cover 22 is connected to the housing 21 by welding, bonding, clamping or other methods.

[0090] The housing 21 may be open at one end or at both ends. In some examples, the housing 21 may be a structure with an opening at one end, and an end cap 22 is provided and covers the housing 21. In other examples, the housing 21 may be a structure with openings at both ends, and two end caps 22 are provided, and the two end caps 22 cover the two openings of the housing 21 respectively.

[0091] In some embodiments, the sodium ion battery cell 6 further includes a pressure relief mechanism 30 disposed on the housing 20 .

[0092] Exemplarily, the pressure relief mechanism 30 may refer to an element or component that is actuated to release internal gas when the internal pressure or temperature of the sodium ion battery cell 6 reaches a predetermined threshold. The threshold design varies according to different design requirements. The threshold may depend on one or more materials of the positive electrode sheet, negative electrode sheet, electrolyte and separator in the sodium ion battery cell 6.

[0093] The "actuation" mentioned in this application means that the pressure relief mechanism 30 is in action or activated to a certain state, so that the internal pressure of the sodium-ion battery cell 6 can be released. The action produced by the pressure relief mechanism 30 may include but is not limited to: at least a part of the pressure relief mechanism 30 is broken, shattered, torn or opened, etc. When the pressure relief mechanism 30 is actuated, the high-temperature and high-pressure substances inside the sodium-ion battery cell 6 will be discharged from the actuated part as emissions. In this way, the sodium-ion battery cell 6 can be depressurized under controllable pressure, thereby avoiding potential more serious accidents.

[0094] The emissions from the sodium-ion battery cells 6 mentioned in the present application include, but are not limited to: electrolytes, dissolved or split positive and negative electrode sheets, separator fragments, high-temperature and high-pressure gases produced by the reaction, flames, and the like.

[0095] The internal pressure of the sodium ion battery cell 6 may be the internal pressure of the housing 20, and the internal temperature of the sodium ion battery cell 6 may be the internal temperature of the housing 20. In some embodiments, the actuation of the pressure relief mechanism 30 may be triggered only by the internal pressure of the housing 20, may be triggered only by the internal temperature of the housing 20, or may be triggered jointly by the internal pressure and internal temperature of the housing 20.

[0096] As an example, when the sodium ion battery cell 6 is in thermal runaway, as the gas in the housing 20 continues to accumulate, the internal pressure of the housing 20 may reach or even exceed the pressure threshold. When the internal pressure of the housing 20 reaches the threshold, the pressure relief mechanism 30 is actuated and forms an exhaust port to communicate the internal space of the housing 20 with the external space, and the gas inside the housing 20 may be discharged through the exhaust port, thereby reducing the risk of explosion of the sodium ion battery cell 6.

[0097] As an example, when the electrolyte and the active material react and release heat quickly, the internal temperature of the housing 20 will increase, and the temperature increase will also cause the internal pressure of the housing 20 to increase. When the internal temperature of the housing 20 reaches a threshold, the pressure relief mechanism 30 can be actuated under the action of temperature and pressure to form an exhaust port, so that the internal space of the housing 20 is connected to the external space, and the gas inside the housing 20 can be discharged through the exhaust port, thereby reducing the risk of explosion of the sodium ion battery cell 6.

[0098] In some embodiments, the housing 20 includes a wall portion, and the pressure relief mechanism 30 is disposed on the wall portion. As an example, the wall portion may be the end cover 22 or a wall of the housing 21 .

[0099] As an example, the shape of the wall portion may be circular, rectangular, oval, or other shapes.

[0100] In some examples, the pressure relief mechanism 30 and the wall portion are independently formed components, and the two can be connected by welding, bonding or other methods. For example, the wall portion is provided with a pressure relief hole, the pressure relief hole passes through the wall portion, and the pressure relief mechanism 30 is installed on the wall portion and covers the pressure relief hole to separate the space on both sides of the wall portion. In an alternative embodiment, the pressure relief mechanism 30 and the wall portion can also be an integrally formed structure.

[0101] In some embodiments, the electrode assembly 10 includes a main body 11 and a tab 12 , wherein the tab 12 is led out from an end of the main body 11 along a first direction Z.

[0102] As an example, the electrode assembly 10 includes a positive electrode sheet and a negative electrode sheet. The main body 11 includes a portion of the positive electrode sheet having a positive active material and a portion of the negative electrode sheet having a negative active material.

[0103] The tab 12 may include a positive tab 121 and a negative tab 122 ; the positive tab 121 may include a portion of the positive electrode sheet without positive active material, and the negative tab 122 may include a portion of the negative electrode sheet without negative active material.

[0104] The positive electrode tab 121 and the negative electrode tab 122 may be led out from the same end of the main body 11 along the first direction Z, or may be led out from two ends of the main body 11 along the first direction Z respectively.

[0105] During the charge and discharge process of the sodium ion battery cell 6 , the positive electrode active material and the negative electrode active material of the main body portion 11 react with the electrolyte.

[0106] In some embodiments, the sodium ion battery cell 6 further includes an electrode terminal 40 , which is disposed on the housing 20 and electrically connected to the tab 12 .

[0107] In some embodiments, the rated energy of the sodium ion battery cell 6 is En, the cross-sectional area of ​​the accommodating cavity 20a perpendicular to the first direction Z is S1, the cross-sectional area of ​​the main body 11 perpendicular to the first direction Z is S2, and the number of electrode assemblies 10 is k, where k is a positive integer. The unit of En is Wh, and the units of S1 and S2 are both mm 2 .

[0108] En, S1, k and S2 meet: 0.3Wh / mm 2 ≤En / (S1-k×S2)≤7Wh / mm 2 .

[0109] Exemplarily, the rated capacity of the sodium-ion battery cell 6 is E1, the rated voltage of the sodium-ion battery cell 6 is E2, and the rated energy En of the sodium-ion battery cell 6 is E1×E2.

[0110] En is related to the severity of gas generation during thermal runaway of the sodium-ion battery cell 6. For example, the larger En is, the more severe the gas generation of the sodium-ion battery cell 6 during thermal runaway is, and the higher the gas generation rate is.

[0111] k×S2 can be used to characterize the space filled by the main body 11 of the accommodating cavity 20a; S1-k×S2 can be used to characterize the size of the channel inside the housing 20 for gas flow when the sodium ion battery cell 6 is in thermal runaway. The larger S1-k×S2 is, the smoother the gas flows in the housing 20 when the sodium ion battery cell 6 is in thermal runaway, and the gas can be discharged from the pressure relief mechanism 30 more quickly. For example, the end of the main body 11 along the first direction Z needs to lead out the pole ear 12, so there will be a gap at both ends of the main body 11 along the first direction Z; when the main body 11 has an unexpected situation such as a short circuit, the gas generated inside the main body 11 can be ejected from both ends of the main body 11 along the first direction Z through the gap; the channel between the outer peripheral surface of the main body 11 and the housing 20 can connect the space on both sides of the main body 11 along the first direction Z, and the flow capacity of the channel is positively correlated with S1-k×S2. The larger S1-k×S2 is, the easier it is for the gas to flow and gather to the pressure relief mechanism 30, so that the gas is discharged faster.

[0112] Of course, the larger S1-k×S2 is, the lower the internal space utilization of the housing 20 is, and the lower the energy density of the battery cell is.

[0113] In view of this, the embodiment of the present application limits the value of En / (S1-k×S2) to less than or equal to 7Wh / mm 2 , so as to increase the gas discharge rate when the sodium ion battery cell 6 has thermal runaway, reduce the risk of rupture and explosion of the sodium ion battery cell 6, and improve the reliability of the battery cell. The embodiment of the present application also limits the value of En / (S1-k×S2) to be greater than or equal to 0.3Wh / mm 2 , so as to reduce the loss of space utilization of the sodium ion battery cell 6 while reducing the risk of explosion of the sodium ion battery cell 6, and balance the reliability and energy density of the sodium ion battery cell 6.

[0114] In some embodiments, En / (S1-k×S2) may be 0.3Wh / mm 2 , 0.4Wh / mm 2 , 0.5Wh / mm 2 , 0.6Wh / mm 2 , 0.7Wh / mm 2 , 0.8Wh / mm 2 , 0.9Wh / mm 2 , 1Wh / mm 2 , 1.3Wh / mm 2 , 1.5Wh / mm 2, 1.6Wh / mm 2 , 1.8Wh / mm 2 , 2Wh / mm 2 , 2.2Wh / mm 2 , 2.5Wh / mm 2 , 2.8Wh / mm 2 , 3Wh / mm 2 , 3.3Wh / mm 2 、3.5Wh / mm 2 、3.8Wh / mm 2 , 4Wh / mm 2 , 4.3Wh / mm 2 , 4.5Wh / mm 2 , 4.8Wh / mm 2 , 5Wh / mm 2 、5.3Wh / mm 2 , 5.5Wh / mm 2 、5.8Wh / mm 2 , 6Wh / mm 2 、6.3Wh / mm 2 、6.4Wh / mm 2 、6.5Wh / mm 2 、6.7Wh / mm 2 、6.8Wh / mm 2 、6.9Wh / mm 2 or 7Wh / mm 2 .

[0115] In some embodiments, En, S1, k, and S2 satisfy: 0.9Wh / mm 2 ≤En / (S1-k×S2)≤5Wh / mm 2 The embodiment of the present application can further balance the reliability and energy density of the sodium ion battery cell 6, reduce the risk of rupture of the battery cell housing 20, discharge gas from a set area (ie, the area corresponding to the pressure relief mechanism 30), and reduce the loss of energy density.

[0116] In some embodiments, the area of ​​the pressure relief mechanism 30 is S3. (S1-k×S2) / S3 is 0.5-7. The embodiment of the present application can improve the efficiency of gas discharge from the pressure relief mechanism 30, limit the range of gas after being ejected from the pressure relief mechanism 30, and reduce the risk of heat spread.

[0117] Exemplarily, (S1-k×S2) / S3 may be 0.5, 0.6, 0.7, 0.8, 0.9, 0.1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, 6.2, 6.3, 6.5, 6.6, 6.8, 6.9 or 7.

[0118] In some embodiments, (S1-k×S2) / S3 is 0.8-6.5.

[0119] In some embodiments, the housing 20 includes a shell 21 and an end cover 22 . The shell 21 has an opening at an end along the first direction Z, and the end cover 22 covers the opening.

[0120] The embodiment of the present application can release pressure in time when thermal runaway occurs in the sodium ion battery cell 6, thereby reducing the risk of the end cover 22 being separated from the shell 21 under pressure and improving reliability.

[0121] In some embodiments, the pressure relief mechanism 30 is disposed on the end cover 22. The pressure relief mechanism 30 can be opposite to the main body 11 along the first direction Z, so that the reaction time of the pressure relief mechanism 30 can be shortened when the sodium ion battery cell 6 is thermally runaway, and the pressure can be relieved in time, thereby improving the reliability of the sodium ion battery cell 6.

[0122] In other embodiments, the pressure relief mechanism 30 may also be disposed on the housing 21. For example, the pressure relief mechanism 30 may be disposed on the bottom wall of the housing 21 opposite to the end cover 22, or may be disposed on the side wall of the housing 21 connected to the end cover 22.

[0123] In some embodiments, the shape of the electrode assembly 10 can be cylindrical, flat, or polygonal.

[0124] Figure 5 A schematic diagram of an electrode assembly of a sodium ion battery cell provided in some embodiments of the present application; Figure 6 for Figure 5 Schematic diagram of the cross section along the AA direction.

[0125] Please refer to Figures 4 to 6 In some embodiments, the electrode assembly 10 includes a first electrode sheet 13 and a second electrode sheet 14 with opposite polarities. One of the first electrode sheet 13 and the second electrode sheet 14 is a positive electrode sheet, and the other is a negative electrode sheet.

[0126] In some embodiments, the electrode assembly 10 is a laminate structure.

[0127] As an example, a plurality of the first pole pieces 13 and a plurality of the second pole pieces 14 may be provided respectively, and the plurality of first pole pieces 13 and the plurality of first pole pieces 13 may be alternately stacked.

[0128] As an example, a plurality of first pole sheets 13 may be provided, and the second pole sheet 14 may be folded to form a plurality of stacked folded segments, with one first pole sheet 13 being sandwiched between adjacent folded segments.

[0129] As an example, the first pole piece 13 and the second pole piece 14 are both folded to form a plurality of stacked folded segments.

[0130] In some embodiments, the electrode assembly 10 is a winding structure. Exemplarily, the first electrode sheet 13 and the second electrode sheet 14 are wound.

[0131] In some embodiments, the main body 11 includes a straight area 11 a and two bending areas 11 b , and the two bending areas 11 b are respectively located on both sides of the straight area 11 a along the second direction X, and the second direction X is perpendicular to the first direction Z.

[0132] In the second direction X, a channel may be formed between the housing 20 and the bending area 11b to facilitate gas flow when the sodium ion battery cell 6 is in thermal runaway. By providing the bending area 11b, the flow capacity of the channel may be enhanced.

[0133] In some embodiments, the size of the accommodation cavity 20a along the second direction X is L1, and the size of the accommodation cavity 20a along the third direction Y is H1. The first direction Z, the second direction X, and the third direction Y are perpendicular to each other.

[0134] The size of the straight area 11a along the second direction X is L2, and the size of the straight area 11a along the third direction Y is H2. The bending area 11b is substantially semicircular, and the radius r of the bending area 11b is H2 / 2. Exemplarily, H1 is approximately equal to k×H2.

[0135] Exemplarily, S1 = H1 × L1. It is noted here that the fillet of the inner wall of the housing 21 has a small effect on the area and is therefore ignored.

[0136] S2=L2×H2+π×r 2 . S1-k×S2=(L1-L2)×H1-k×π×r 2 .

[0137] In some embodiments, the pressure relief mechanism 30 may also be disposed on a side wall of the housing 21 opposite to the bending area 11 b along the second direction X.

[0138] In some embodiments, the electrode assembly 10 further includes an isolating member 15 , which insulates and isolates the first electrode piece 13 from the second electrode piece 14 .

[0139] As an example, a plurality of spacers 15 may be provided, each spacer 15 being provided between any adjacent first pole pieces 13 or second pole pieces 14 .

[0140] As an example, the spacer 15 may be disposed continuously, and disposed between any adjacent first pole pieces 13 or second pole pieces 14 by folding or winding.

[0141] In some embodiments, k is 2 to 4. Exemplarily, k electrode assemblies 10 are stacked along the third direction Y.

[0142] In some embodiments, the electrode assembly 10 is a wound structure.

[0143] For example, under the premise that L1, L2+2×r, and H1 are constant, the larger k is, the smaller r is, and the larger L2 is. Correspondingly, the larger k is, the smaller S1-k×S2 is. By reasonably allocating the number of electrode assemblies 10, the current capacity of the channel and the energy density of the battery cell can be balanced.

[0144] In the embodiment of the present application, k is limited to 2-4, which can reduce the loss of space utilization of the sodium ion battery cell 6 while reducing the risk of explosion of the sodium ion battery cell 6, and balance the reliability and energy density of the sodium ion battery cell 6.

[0145] In some embodiments, the electrode assembly 10 includes a first electrode sheet 13, a second electrode sheet 14 and a separator 15. The first electrode sheet 13 and the second electrode sheet 14 have opposite polarities. The separator 15 insulates and isolates the first electrode sheet 13 and the second electrode sheet 14. The first electrode sheet 13, the second electrode sheet 14 and the separator 15 are wound. The first electrode sheet 13 and the second electrode sheet 14 each include a plurality of bending layers 16 located in the bending area 11b. In the bending area 11b, at least two bending layers 16 from the outside to the inside are first bending layers 16a provided with through holes 16b.

[0146] In the bending area 11 b , only a portion of the bending layers 16 may be the first bending layers 16 a , or all of the bending layers 16 may be the first bending layers 16 a .

[0147] When the main body 11 generates gas internally due to thermal runaway, the gas can be discharged through the through hole 16b to the channel between the bending area 11b and the outer shell 20, thereby exhausting the gas in time, reducing the risk of fire and explosion of the battery cell and improving reliability.

[0148] In some embodiments, the through holes 16b of adjacent first bending layers 16a are opposite to each other along the radial direction of the bending area 11b, which can shorten the gas flow path and improve the exhaust efficiency.

[0149] In some embodiments, the isolating member 15 may be provided with a through hole in the bending region 11b. In other embodiments, the isolating member 15 may not be provided with a through hole in the bending region 11b; when thermal runaway occurs, the isolating member 15 may melt under high temperature to reduce the degree of blocking of the isolating member 15 on the through hole 16b of the first bending layer 16a, so as to facilitate the passage of gas through the through hole 16b. In the bending region 11b, the isolating member 15 is not provided with a through hole, which can improve the insulation isolation effect of the isolating member 15 and reduce the risk of short circuit.

[0150] In some embodiments, in the winding direction of the electrode assembly 10, the arc length of the first bending layer 16a is W, and the size of the through hole 16b is 0.25W-0.5W. Figure 6 The winding direction is counterclockwise.

[0151] In some embodiments, the first bending layer 16a may be provided with a plurality of through holes 16b. At least two through holes 16b of the first bending layer 16a are provided along the winding direction.

[0152] In some embodiments, the angle between the axial direction of the through hole 16b of the first bending layer 16a and the second direction X is 30°-60°. Optionally, the angle between the axial direction of the through hole 16b of the first bending layer 16a and the second direction X is 45°.

[0153] In some embodiments, the bending region 11 b is provided with a recess 11 c , which is recessed from the outer surface of the bending region 11 b and passes through at least two bending layers 16 .

[0154] The bending layer 16 penetrated by the concave portion 11c is the first bending layer 16a. The position where the first bending layer 16a is penetrated by the concave portion 11c forms a through hole 16b.

[0155] In the bending region 11 b , the recess 11 c penetrates at least one layer of the isolation member 15 .

[0156] The recess 11c may be provided in only one bending region 11b, or in both bending regions 11b. There may be one or more recesses 11c on the bending region 11b.

[0157] By providing the recess 11 c , when the main body 11 generates gas internally due to thermal runaway, the gas inside the main body 11 can be discharged in time, thereby reducing the risk of fire and explosion of the battery cell and improving reliability.

[0158] In some embodiments, the total number of layers of the bending layer 16 of the bending zone 11 b is m1, the number of layers of the first bending layer 16 a is m2, and m2 / m1≥0.5.

[0159] The first bending layer 16a having the through hole 16b has a large number of layers, and can also be quickly exhausted when the short-circuit point of the main body 11 is located inward.

[0160] In some embodiments, all bending layers 16 of the bending region 11 b are first bending layers 16 a. In other words, m2=m1.

[0161] The embodiments of the present application can further improve the exhaust efficiency.

[0162] In some embodiments, the dimension of the main body 11 along the first direction Z is h. In the first direction Z, the minimum distance between the recess 11 c and one end of the main body 11 is D1, and 1 / 3h≤D1≤2 / 3h.

[0163] Optionally, D1 is 1 / 3h, 1 / 2h or 2 / 3h.

[0164] When thermal runaway occurs, the area close to the end of the bending zone 11b along the first direction Z can be vented through the end without setting the recess 11c; setting the recess 11c in the middle area of ​​the bending zone 11b along the first direction Z can not only allow the middle area of ​​the bending zone 11b to be vented outwardly through the recess 11c, but also reduce the number of recesses 11c, reduce the loss of pole piece strength, and reduce the risk of deformation of the bending zone 11b.

[0165] Figure 7 for Figure 6 Enlarged diagram of the circle.

[0166] like Figure 7 As shown, in some embodiments, in the straight region 11a, the first pole piece 13 and the second pole piece 14 are stacked along a third direction Y, and the third direction Y is perpendicular to the first direction Z and the second direction X. In the third direction Y, the distance D2 between adjacent first pole pieces 13 and second pole pieces 14 is 10 μm-40 μm.

[0167] In the embodiment of the present application, D2 is limited to be greater than or equal to 10 μm, which can increase the spacing between the first pole piece 13 and the second pole piece 14, reduce the heat transfer rate, and reduce the gas generation of the thermal runaway electrode assembly 10. In the embodiment of the present application, D2 is limited to be less than or equal to 40 μm, which can reduce the difficulty of ion migration and reduce the risk of sodium precipitation on the pole piece surface.

[0168] Optionally, D2 is 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm or 40 μm.

[0169] Optionally, D2 is 15 μm-35 μm.

[0170] In some embodiments, the distance D2 between the first pole piece 13 and the second pole piece 14 can be increased by increasing the thickness of the isolating member 15. In other embodiments, a certain thickness of alumina ceramic powder can be sprayed on the surface of the isolating member 15 to increase the distance D2 between the first pole piece 13 and the second pole piece 14.

[0171] Figure 8 A partial cross-sectional schematic diagram of an electrode assembly of a sodium ion battery cell provided in some embodiments of the present application.

[0172] In some embodiments, Figure 8 As shown, in the straight region 11a, the isolation member 15 is provided with a convex portion 151. By providing the convex portion 151 on the isolation member 15, the distance D2 between the first pole piece 13 and the second pole piece 14 can be increased.

[0173] In some embodiments, the spacer 15 is provided with a cavity 152 at a position corresponding to the convex portion 151. For example, the spacer 15 may be pressed to form a concave-convex structure on the spacer 15.

[0174] Fig. 9 A schematic cross-sectional view of a first pole piece of a sodium ion battery cell provided in some embodiments of the present application.

[0175] like Figure 6 and Fig. 9 As shown, in some embodiments, the electrode assembly 10 includes a first pole piece 13, a second pole piece 14 and a separator 15, the first pole piece 13 and the second pole piece 14 have opposite polarities, and the separator 15 insulates the first pole piece 13 and the second pole piece 14. A high temperature resistant coating 17 is provided on the surface of at least one of the first pole piece 13, the second pole piece 14 and the separator 15.

[0176] By providing the high temperature resistant coating 17 , the heat transfer after the pole piece is burned can be slowed down to a certain extent, the heat resistance of the pole piece or the separator 15 can be enhanced, the gas production can be reduced, and the risk of explosion of the sodium ion battery cell 6 can be reduced.

[0177] In some embodiments, the high temperature resistant coating 17 may include an aluminum oxide coating or a nano ceramic coating.

[0178] In some embodiments, the high temperature resistant coating 17 may be disposed on the first pole piece 13 , the second pole piece 14 and the isolation member 15 at the same time.

[0179] In some embodiments, the first electrode sheet 13 includes a first current collector 131 and a first active material layer 132 disposed on a surface of the first current collector 131 .

[0180] Exemplarily, the first pole piece 13 may be a positive pole piece, and the first current collector 131 is a positive current collector. Optionally, the positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, titanium, silver surface treated aluminum or stainless steel, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0181] Exemplarily, the first pole piece 13 may be a negative pole piece, and the first current collector 131 is a negative current collector. Optionally, the negative current collector may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, stainless steel, copper, aluminum, nickel, carbon electrode, aluminum or stainless steel treated with carbon, nickel, titanium, silver, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0182] In some embodiments, a high temperature resistant coating 17 is disposed on a side of the first active material layer 132 facing away from the first current collector 131 .

[0183] In some embodiments, the electrode assembly 10 includes a positive electrode active material, and the positive electrode active material includes at least one of a Prussian blue-based positive electrode material, a layered oxide-based positive electrode material, or a polyanion-based positive electrode material.

[0184] Exemplarily, the first electrode sheet 13 may be a positive electrode sheet, and the first active material layer 132 includes a positive electrode active material.

[0185] An embodiment of the present application also provides a battery, which includes a plurality of sodium ion battery cells 6 provided in any of the aforementioned embodiments.

[0186] According to some embodiments of the present application, the present application further provides an electric device, comprising a battery in any of the above embodiments, the battery is used to provide electric energy to the electric device. The electric device can be any of the above-mentioned devices or systems using the battery.

[0187] Reference Figures 3 to 6 An embodiment of the present application provides a square sodium-ion battery cell 6 , which includes a housing 20 , an electrode assembly 10 and a pressure relief mechanism 30 .

[0188] The housing 20 includes a housing 21 and an end cap 22. The housing 21 has an opening at one end along the first direction Z, and the end cap 22 is used to cover the opening. The pressure relief mechanism 30 is disposed on the end cap 22. The electrode assembly 10 is accommodated in the housing 20 and includes a main body 11 and a tab 12. The tab 12 is led out from the end of the main body 11 along the first direction Z.

[0189] The electrode assembly 10 includes a first electrode sheet 13, a second electrode sheet 14 and an isolating member 15. The first electrode sheet 13 and the second electrode sheet 14 have opposite polarities. The isolating member 15 insulates the first electrode sheet 13 and the second electrode sheet 14. The first electrode sheet 13, the second electrode sheet 14 and the isolating member 15 are wound.

[0190] The main body 11 of the electrode assembly 10 includes a straight area 11 a and two bending areas 11 b . The two bending areas 11 b are respectively located on both sides of the straight area 11 a along a second direction X. The second direction X is perpendicular to the first direction Z.

[0191] The rated energy of the sodium ion battery cell 6 is En, the cross-sectional area of ​​the accommodating cavity 20a perpendicular to the first direction Z is S1, the cross-sectional area of ​​the main body 11 perpendicular to the first direction Z is S2, and the number of electrode assemblies 10 is k, where k is a positive integer greater than 1. En, S1, k and S2 satisfy: 0.3Wh / mm 2 ≤En / (S1-k×S2)≤7Wh / mm 2 The k electrode assemblies 10 are stacked along a third direction Y. The third direction Y is perpendicular to the first direction Z and the second direction X.

[0192] Example

[0193] The following examples describe the disclosure of the present application in more detail, and these examples are only for illustrative purposes, as it is obvious to those skilled in the art that various modifications and variations can be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0194] Example 1

[0195] (i) Preparation of positive electrode sheet

[0196] The positive electrode active material NaMnKFe(CN)6, the conductive agent acetylene black, and the binder carboxymethyl cellulose are fully stirred and mixed in a proper amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to form a uniform positive electrode slurry; the positive electrode slurry is 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 175 μm is obtained.

[0197] (ii) Preparation of negative electrode sheet

[0198] The negative electrode active material artificial graphite, the conductive agent acetylene black, and the binder carboxymethyl cellulose are mixed in a mass ratio of 94:5:1, and are fully stirred in an appropriate amount of deionized water to form a uniform negative electrode slurry; the negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, and after drying, cold pressing, and die-cutting, a negative electrode sheet is obtained.

[0199] (iii) Spacers

[0200] A polyethylene film with a thickness of 9 μm was used.

[0201] (iv) Preparation of electrolyte

[0202] The sodium salt solvent, sodium hexafluorophosphate and additive are stirred and mixed in a mass ratio of 85:10:5 to obtain a sodium salt electrolyte.

[0203] (v) Preparation of electrode assembly

[0204] Forming an electrode assembly by winding the positive electrode sheet, the separator and the negative electrode sheet;

[0205] (vi) Preparation of sodium ion battery monomers

[0206] The electrode assembly is placed in the shell, and the shell and the end cover are welded; after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a sodium ion battery monomer is obtained.

[0207] For example, refer to Figure 4 , the dimensions of the prepared electrode assembly are as follows: the dimension H2 of the straight area along the third direction is 24mm, that is, the radius r of the bending area is 12mm, and the dimension L2 of the straight area along the second direction is 152mm; the dimension L1 of the accommodating cavity along the second direction is 193.3mm, and the dimension H1 of the accommodating cavity along the second direction is 48mm. The dimension of the battery cell along the first direction is 146mm, and the dimension of the main body of the electrode assembly along the first direction is 136mm. After calculation, S1 = 193.3mm × 48mm = 9278mm 2 , S2=24mm×152mm+π×12 2 mm 2 =4100mm 2. S1-2×S2=1078mm 2 .

[0208] There are two electrode assemblies inside the sodium ion battery cell. The rated capacity of the sodium ion battery cell is 108Ah and the rated voltage is 3V. The rated energy En of the sodium ion battery cell is 405Wh. En / (S1-k×S2)=1Wh / mm 2 .

[0209] Embodiment 2-8

[0210] The preparation method of the sodium ion battery monomer of Examples 2-8 can refer to Example 1. The differences between Examples 2-8 and Example 1 are shown in Table 1. For example, S1, S2 and En of the sodium ion battery monomer can be changed by changing the forming method (winding or lamination) of the electrode assembly, the number k of the electrode assembly, the size of the shell, the size of the electrode assembly or the composition of the active material.

[0211] Comparative Examples 1-4

[0212] The preparation methods of the sodium ion battery cells of Comparative Examples 1-4 can refer to Example 1. The differences between Comparative Examples 1-4 and Example 1 are shown in Table 1. For example, S1, S2 and En of the sodium ion battery cell can be changed by changing the forming method (winding or lamination) of the electrode assembly, the number k of the electrode assembly, the size of the shell, the size of the electrode assembly or the composition of the active material.

[0213] Test Section

[0214] Use a 3mm diameter steel needle to vertically penetrate the center of the large surface of the sodium ion battery cell at a speed of 5mm / s until the sodium ion battery cell catches fire. Observe whether the sodium ion battery cell is cracked in the area near the connection between the shell and the end cover.

[0215] Table 1

[0216]

[0217] Referring to Examples 1-8 and Comparative Examples 1-2, the value of En / (S1-k×S2) is limited to be greater than or equal to 0.3Wh / mm 2 , in order to reduce the loss of space utilization of sodium ion battery cells and improve energy density while reducing shell cracking and explosion. Referring to Examples 1-8 and Comparative Examples 3-4, the value of En / (S1-k×S2) in this application example is limited to less than or equal to 7Wh / mm 2, so as to increase the gas discharge rate when thermal runaway occurs in the sodium-ion battery monomer, reduce the risk of shell rupture and sodium-ion battery monomer explosion, and improve the reliability of the sodium-ion battery monomer.

[0218] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A sodium ion battery cell, characterized in that: include: A housing having a receiving cavity; A pressure relief mechanism, disposed on the housing; An electrode assembly, contained in the containing cavity and comprising a main body and a tab, wherein the tab is led out from an end of the main body along a first direction; The rated energy of the sodium ion battery cell is En, the cross-sectional area of ​​the accommodating cavity perpendicular to the first direction is S1, the cross-sectional area of ​​the main body perpendicular to the first direction is S2, and the number of the electrode assemblies is k, where k is a positive integer; The unit of En is Wh, and the unit of S1 and S2 is mm 2 ; En, S1, k and S2 meet: 0.3Wh / mm 2 ≤En / (S1-k×S2)≤7Wh / mm 2 .

2. The sodium ion battery cell according to claim 1, characterized in that: En, S1, k and S2 satisfy: 0.9Wh / mm 2 ≤En / (S1-k×S2)≤5Wh / mm 2 。 3. The sodium ion battery cell according to claim 1 or 2, characterized in that: The area of ​​the pressure relief mechanism is S3; (S1-k×S2) / S3 is 0.5-7.

4. The sodium ion battery cell according to claim 3, characterized in that: (S1-k×S2) / S3 is 0.8-6.

5.

5. The sodium ion battery cell according to any one of claims 1 to 4, characterized in that: The housing comprises a shell and an end cover, the shell has an opening at an end along the first direction, and the end cover covers the opening; The pressure relief mechanism is arranged on the end cover.

6. The sodium ion battery cell according to any one of claims 1 to 5, characterized in that: The electrode assembly is a winding structure; the main body includes a straight area and two bending areas, and the two bending areas are respectively located on both sides of the straight area along a second direction, and the second direction is perpendicular to the first direction.

7. The sodium ion battery cell according to claim 6, characterized in that: The electrode assembly comprises a first pole piece, a second pole piece and a separator, the first pole piece and the second pole piece have opposite polarities, the separator insulates the first pole piece and the second pole piece, and the first pole piece, the second pole piece and the separator are wound; The first pole piece and the second pole piece both include a plurality of bending layers located in the bending area; in the bending area, at least two of the bending layers from the outside to the inside are first bending layers provided with through holes.

8. The sodium ion battery cell according to claim 7, characterized in that: The bending zone is provided with a concave portion, which is sunken from the outer surface of the bending zone and passes through at least two of the bending layers.

9. The sodium ion battery cell according to claim 8, characterized in that: The dimension of the main body along the first direction is h; In the first direction, a minimum distance between the recess and one end of the main body is D1, and 1 / 3h≤D1≤2 / 3h.

10. The sodium ion battery cell according to any one of claims 7 to 9, characterized in that: The total number of the bending layers in the bending zone is m1, the number of the first bending layers is m2, and m2 / m1≥0.

5.

11. The sodium ion battery cell according to any one of claims 7 to 10, characterized in that: In the straight region, the first pole piece and the second pole piece are stacked along a third direction, and the third direction is perpendicular to the first direction and the second direction; In the third direction, the distance between adjacent first pole pieces and second pole pieces is 10 μm-40 μm.

12. The sodium ion battery cell according to claim 11, characterized in that: The isolating member is provided with a convex portion in the flat region.

13. The sodium ion battery cell according to any one of claims 1 to 12, characterized in that: The electrode assembly comprises a first pole piece, a second pole piece and a separator, the first pole piece and the second pole piece have opposite polarities, and the separator insulates the first pole piece and the second pole piece; A high temperature resistant coating is provided on a surface of at least one of the first pole piece, the second pole piece and the isolation member.

14. The sodium ion battery cell according to any one of claims 1 to 13, characterized in that: The electrode assembly includes a positive electrode active material, and the positive electrode active material includes at least one of a Prussian blue-based positive electrode material, a layered oxide-based positive electrode material, or a polyanion-based positive electrode material.

15. The sodium ion battery cell according to any one of claims 1 to 14, characterized in that: k is 2-4.

16. A battery, characterized in that: It comprises a plurality of sodium ion battery cells according to any one of claims 1 to 15.

17. An electrical device, characterized in that: A battery according to claim 16, for providing electrical energy.

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