Sodium ion battery monomer, battery and electric device

Abstract

The sodium ion battery monomer disclosed by the invention comprises a positive pole piece and a negative pole piece which are oppositely arranged, the positive pole piece contains sodium layered metal oxide, the negative pole piece contains hard carbon, and the distance between the positive pole piece and the negative pole piece is 15-45 microns. According to the sodium ion battery monomer, the distance between the positive pole piece and the negative pole piece in the sodium ion battery monomer is set to be 15-45 microns, the negative pole piece containing hard carbon can transmit a small amount of heat to the positive pole piece after heating by utilizing the distance range, and the transmitted heat has small influence on the stability of a sodium layered metal oxide material in the positive pole piece; meanwhile, the negative pole piece is not easy to accumulate heat quickly, so that thermal runaway is not easy to occur between the positive pole piece and the negative pole piece, and the safety performance of the sodium ion battery can be improved.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and particularly relates to a sodium-ion battery cell, a battery, and an electrical device. Background Art

[0002] A sodium-ion battery (SIB) is a new type of secondary battery, and its positive electrode material is a sodium-ion compound. Sodium-ion batteries have a relatively high energy density and lower costs, and thus have attracted much attention in the battery field. In recent years, sodium-ion batteries have been increasingly used in electric transportation and energy storage systems.

[0003] Generally, in a lithium-ion battery (LIB) system, thermal runaway is usually caused by three reasons: oxygen release from the positive electrode, lithium deposition on the negative electrode, and melting and collapse of the separator. However, there is less research on the thermal runaway mechanism of sodium-ion batteries. People only know that if the battery undergoes thermal runaway, it is likely to cause safety problems. Summary of the Invention

[0004] In view of the above problems, this application provides a sodium-ion battery cell, a battery module, a battery pack, and an electrical device, aiming to solve the technical problem of how to reduce the thermal runaway risk of sodium-ion batteries at low cost to improve their safety performance.

[0005] In a first aspect, an embodiment of this application provides a sodium-ion battery cell, including a positive electrode tab and a negative electrode tab arranged oppositely. The positive electrode tab contains sodium layered metal oxide, and the negative electrode tab contains hard carbon; the distance between the positive electrode tab and the negative electrode tab is 15 - 45 μm.

[0006] This application discovers that when the sodium-ion battery cell is charged to more than 50% SOC, the heat accumulated from the reaction between sodium metal in the negative electrode tab and the electrolyte will continuously increase the temperature, which may trigger the oxygen release reaction of the sodium layered metal oxide material in the positive electrode tab, accelerating the thermal runaway of the sodium-ion battery cell; therefore, this application sets the distance between the positive electrode tab and the negative electrode tab to 15 - 45 μm. Using this distance range, a small amount of heat can be transferred from the heated negative electrode tab to the positive electrode tab, making it difficult for thermal runaway to occur between the positive electrode tab and the negative electrode tab, and improving the safety performance of the sodium-ion battery.

[0007] In some embodiments, the sodium deintercalation specific capacity of the sodium layered metal oxide is 100 - 200 mAh / g, and the coating areal density of the sodium layered metal oxide is 0.01 - 0.04 g / cm 2 .

[0008] In some embodiments, the sodium storage capacity of the hard carbon is 200-400 mAh / g, and the coating areal density of the hard carbon is 0.005-0.02 g / cm 2 .

[0009] In some embodiments, the sodium extraction capacity of the sodium layered metal oxide is 140-170 mAh / g, and the sodium storage capacity of the hard carbon is 300-370 mAh / g.

[0010] The sodium-ion battery monomer formed by combining the positive electrode sheet formed by the sodium layered metal oxide with the above-mentioned sodium extraction capacity and the negative electrode sheet formed by the hard carbon with the above-mentioned sodium storage capacity can endow the battery with better charge and discharge performance and safety performance.

[0011] In some embodiments, a separator is provided between the positive electrode sheet and the negative electrode sheet, and the thickness of the separator is less than or equal to the distance between the positive electrode sheet and the negative electrode sheet.

[0012] By providing a separator with a certain thickness between the positive electrode sheet and the negative electrode sheet, the required distance between the positive electrode sheet and the negative electrode sheet can be maintained.

[0013] In some embodiments, the sodium-ion battery monomer further includes an electrolyte, and the electrolyte includes a carbonate solvent.

[0014] The carbonate solvent has low toxicity, is environmentally friendly, has good oxidation resistance, and has good stability when contacting the negative electrode sheet. Therefore, such an electrolyte has good electrochemical stability when used in the sodium-ion battery monomer. Combined with the minimum distance between the positive electrode sheet and the negative electrode sheet in the present application, the battery life can be further extended.

[0015] In a second aspect, an embodiment of the present application provides a battery, including at least two sodium-ion battery monomers provided in the first aspect of the present application.

[0016] Due to the adoption of the sodium-ion battery monomer of the embodiment of the present application, such a battery is not prone to thermal runaway, and thus has good safety performance.

[0017] In a third aspect, an embodiment of the present application provides an electrical device, which includes the sodium-ion battery monomer provided in the first aspect of the present application, or the battery provided in the second aspect of the present application.

[0018] By adopting the sodium-ion battery monomer or battery provided in the embodiment of the present application, such an electrical device is not prone to thermal runaway, has good safety, and can work for a longer time.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically given below. Description of the Drawings

[0020] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0021] Figure 1 is a schematic structural diagram of an embodiment of a sodium-ion battery cell of this application;

[0022] Figure 2 is Figure 1 a decomposition schematic diagram of the shown sodium-ion battery cell;

[0023] Figure 3 is a schematic structural diagram of an embodiment of a battery module of this application;

[0024] Figure 4 is a schematic structural diagram of an embodiment of a battery pack of this application;

[0025] Figure 5 is Figure 4 a decomposition structural diagram of the shown battery pack;

[0026] Figure 6 is a schematic diagram of an embodiment of an electrical device including the sodium-ion battery cell of this application as a power source.

[0027] Description of the Reference Numerals:

[0028] 10 - Sodium-ion battery cell; 11 - Housing; 12 - Top cover assembly; 13 - Electrode assembly; 20 - Battery module; 30 - Battery pack; 31 - Upper box body; 32 - Lower box body. Detailed Embodiments

[0029] The embodiments of the technical solution of this application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0032] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0033] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0034] In the description of the embodiments of this application, the term "a plurality" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces). "At least one kind" refers to more than one kind (including one kind, two kinds, three kinds, etc.).

[0035] In the description of the embodiments of this application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of this application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of this application.

[0036] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0037] With the increasing reduction of traditional energy resources, the development of new energy storage devices has received more and more attention. Among them, secondary batteries have attracted much attention due to their high energy density, high theoretical capacity, good cycle stability and environmental protection characteristics. Secondary batteries can not only be applied to energy storage power systems such as hydraulic, thermal, wind and solar power stations, but also be widely used in electric vehicles such as electric bicycles, electric motorcycles and electric vehicles. With the continuous expansion of the application field of secondary batteries as power batteries, the market demand is also continuously increasing, and at the same time, the performance requirements for batteries such as cycle performance are also getting higher and higher.

[0038] As a type of secondary battery, lithium-ion batteries have the characteristics of high energy density, long service life, energy conservation and environmental protection. However, due to the limitation of global lithium resources and the increase in cost, there are challenges in using lithium-ion batteries for large-scale energy storage. Based on the advantages of sodium-ion batteries such as the abundant global reserves of sodium, low cost and unique battery safety characteristics, they have become important candidates for large-scale energy storage systems. Therefore, the development of sodium-ion batteries without resource limitations and low cost has greater development potential in the energy storage field.

[0039] The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, and both achieve charge and discharge through ion exchange between the positive electrode and the negative electrode. For example, a sodium-ion battery includes a positive electrode and a negative electrode, as well as an electrolyte and a separator located between the positive electrode and the negative electrode. For sodium-ion batteries, with different choices of material systems, the heat generated due to different energies per unit volume is different. Due to the increase in the weight of sodium, the energy density of sodium-ion batteries is usually lower than that of lithium-ion batteries. In order to further improve the energy density of sodium-ion batteries, when the energy density of the selected material system is large, the heat generation is large, and the heat transfer between the electrodes is likely to get out of control, thus causing safety problems.

[0040] At present, there are few studies on the thermal runaway mechanism of sodium-ion batteries, while people know that the thermal runaway of lithium-ion battery systems is mainly caused by three reasons: oxygen release from the positive electrode, lithium deposition at the negative electrode, and collapse of the diaphragm. For normal or fresh lithium-ion batteries, lithium deposition rarely occurs at the negative electrode, so this factor has little effect on normal lithium-ion batteries. For the positive electrode, if a ternary positive electrode material is used, it is found through a 200°C thermal abuse test that the positive electrode will release a large amount of oxygen and heat under the thermal abuse temperature condition. At the same time, the solid electrolyte interphase (SEI) film of the negative electrode is almost destroyed by heat, causing the lithium metal and the electrolyte to react. However, it should be noted that because the negative electrode of the lithium-ion battery is a lithium embedding mechanism, when the SEI film is destroyed, the lithium metal generally does not melt out quickly to react with the electrolyte, that is, the negative electrode reaction is relatively not very intense. As for the separator, safety is very important. If it melts due to heat, it is easy to cause the positive and negative electrodes to overlap and increase heat generation.

[0041] While studying sodium-ion batteries, the inventors of the present application discovered that the factors affecting thermal runaway are very different from those of lithium-ion batteries. Although the mechanism has not been fully clarified, part of the reason is that after charging, especially when the sodium-ion battery is in a charging state greater than 50% SOC (State of Charge), a large amount of metallic sodium at the negative electrode fills pores in the hard carbon. When the battery rises to a certain temperature (about 130°C), the SEI film formed on the surface of the negative electrode begins to break down, and the heat will accumulate and heat up rapidly, triggering a chemical reaction on the positive electrode side. Therefore, it is necessary to dissipate the heat generated by the negative electrode as much as possible as soon as possible.

[0042] Based on the above understanding, in order to solve the safety problem of sodium ion batteries, the embodiment of the present application combines theoretical calculation with experiment, and based on the sodium storage mechanism of the negative electrode sheet, sets a minimum interval between the negative electrode sheet and the positive electrode sheet in the sodium ion battery, which can not only dissipate part of the heat generated by the negative electrode sheet as soon as possible, but also effectively avoid the influence of the heat on the negative electrode side on the positive electrode, so as to achieve the safety of sodium ions at a low cost. Therefore, the following technical solution is proposed.

[0043] Sodium ion battery cells

[0044] In a first aspect, an embodiment of the present application provides a sodium-ion battery cell, which includes a positive electrode sheet and a negative electrode sheet arranged opposite to each other. Among them, the sodium-ion battery cell of the embodiment of the present application has the following two characteristics: (1) The positive electrode sheet contains sodium layered metal oxide, and the negative electrode sheet contains hard carbon; based on the difference in the sodium storage mechanism of the negative electrode sheet of the sodium-ion battery and the lithium intercalation mechanism of the negative electrode of the lithium-ion battery, and the melting point of sodium metal is about 97 °C, and the SEI film of the negative electrode sheet generally starts to be damaged basically from 130 °C. Therefore, the sodium metal stored in the negative electrode sheet of the sodium-ion battery after charging can melt out and react with the electrolyte under the condition of above 130 °C. (2) Based on the above characteristics, the distance between the positive electrode sheet and the negative electrode sheet is set to be 15-45 μm. When the sodium-ion battery is abnormal and the negative electrode sheet starts to heat up, part of the heat of the negative electrode sheet can be transferred to the positive electrode sheet by using this distance range, and the transferred heat is less, which has little impact on the sodium layered metal oxide. At the same time, the negative electrode sheet is not easy to quickly accumulate heat, so that thermal runaway is not easy to occur between the positive electrode sheet and the negative electrode sheet, thereby improving the safety performance of the sodium-ion battery.

[0045] It should be noted that the distance between the positive electrode sheet and the negative electrode sheet mentioned in the embodiment of the present application refers to the distance between adjacent positive electrode sheets and negative electrode sheets in the electrode assembly, that is, the distance between two opposite surfaces of adjacent positive electrode sheets and negative electrode sheets. And the electrode assembly can be in various forms such as winding type and / or stacking type. The distance between adjacent positive electrode sheets and negative electrode sheets is at least 15 μm, for example, it can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 45 μm, etc.

[0046] In the embodiment of the present application, the thickness between adjacent positive electrode sheets and negative electrode sheets of the sodium-ion battery cell is 15-45 μm, so that the sodium-ion battery cell has both good safety performance and high volumetric energy density. The positive active material of the positive electrode sheet includes sodium layered metal oxide, and the negative active material of the negative electrode sheet includes hard carbon. Sodium layered metal oxide is used as the positive active material of the sodium-ion battery, which has the characteristics of high specific capacity and high tap density. However, abnormal heat generation in the sodium-ion battery easily causes the sodium metal oxide to release lattice oxygen, and these lattice oxygen react with hydrogen ions in the battery to generate water molecules, and the water molecules are easy to react with the elemental sodium generated by the negative electrode sheet to release heat. Hard carbon is used as the negative active material of the sodium-ion battery, which has the advantages of low working potential and high capacity. Moreover, in the sodium-ion battery, the sodium storage mechanism of hard carbon includes a large amount of sodium metal filling pores, which is significantly different from the lithium intercalation mechanism of the negative electrode of the lithium-ion battery. For example, when the sodium-ion battery is higher than 50% SOC, the sodium storage mechanism of hard carbon is mainly the filling pore mechanism (that is, a large amount of sodium metal fills the pores).

[0047] Based on this, in the embodiments of the present application, sodium layered metal oxide is used as the positive active material of the positive electrode sheet of the sodium-ion battery, and hard carbon is used as the negative active material of the negative electrode sheet of the sodium-ion battery. At the same time, a certain distance (i.e., 15 - 45 μm) is maintained between the positive electrode sheet and the negative electrode sheet. In this way, not only can the advantages of the above-mentioned active materials be fully utilized, but also thermal runaway is not likely to occur between the positive electrode sheet and the negative electrode sheet, and it has good safety.

[0048] In some embodiments, the sodium extraction specific capacity of the sodium layered metal oxide is 100 - 200 mAh / g, and the coating areal density of the sodium layered metal oxide is 0.01 - 0.04 g / cm 2 . The sodium storage specific capacity of the hard carbon is 200 - 400 mAh / g, and the coating areal density of the hard carbon is 0.005 - 0.02 g / cm 2 .

[0049] Exemplarily, the sodium extraction specific capacity of the sodium layered metal oxide can be 100 mAh / g, 150 mAh / g, 170 mAh / g, 200 mAh / g, etc., and the coating areal density can be 0.01 g / cm 2 , 0.02 g / cm 2 , 0.03 g / cm 2 , 0.04 g / cm 2 etc. The sodium storage specific capacity of the hard carbon can be 200 mAh / g, 250 mAh / g, 3000 mAh / g, 400 mAh / g, etc., and the coating areal density can be 0.005 g / cm 2 , 0.01 g / cm 2 , 0.015 g / cm 2 , 0.02 g / cm 2 etc.

[0050] The areal capacity of the positive electrode sheet of the sodium-ion battery monomer is equal to the sodium extraction specific capacity of the sodium layered metal oxide multiplied by the coating areal density of the sodium layered metal oxide. The sodium extraction specific capacity is the sodium extraction capacity per unit weight of the positive active material during the charge and discharge of the sodium-ion battery monomer. The coating areal density is the weight of the positive active material of the sodium-ion battery coated on a single surface of the positive current collector per unit area. And the areal capacity of the negative electrode sheet is equal to the sodium storage specific capacity of the hard carbon multiplied by the coating areal density of the hard carbon; the storage specific capacity is the sodium storage capacity per unit weight of the negative active material during the charge and discharge of the sodium-ion battery monomer, and the coating areal density is the weight of the negative active material coated on a single surface of the negative current collector per unit area.

[0051] The product of the de-sodiation gram capacity and the coating areal density can yield the capacity per unit area of the corresponding electrode sheet, and the value of the capacity per unit area of the electrode sheet is related to the heat generation energy of the sodium-ion battery monomer. Therefore, the above-mentioned de-sodiation gram capacity and coating areal density parameters can be set for the sodium layered metal oxide of the positive electrode sheet, and the above-mentioned sodium storage gram capacity and coating areal density parameters can be set for the hard carbon of the negative electrode sheet. This not only improves the charge and discharge performance of the battery, but also makes the sodium-ion battery with the above parameters not easily thermally out of control, endowing the battery with good safety.

[0052] In some embodiments, the de-sodiation gram capacity of the sodium layered metal oxide is 140-170 mAh / g, and the sodium storage gram capacity of the hard carbon is 300-370 mAh / g. The sodium-ion battery monomer formed by matching the positive electrode sheet formed by the sodium layered metal oxide with the above de-sodiation gram capacity and the negative electrode sheet formed by the hard carbon with the above sodium storage gram capacity can endow the battery with better charge and discharge performance and safety performance.

[0053] In some embodiments, a separator is provided between the positive electrode sheet and the negative electrode sheet, and the thickness of the separator is less than or equal to the distance between the positive electrode sheet and the negative electrode sheet.

[0054] Specifically, the separator is stacked between the positive electrode sheet and the negative electrode sheet, and the thickness of the separator is 15-45 μm. The sodium-ion battery monomer has good safety performance, low internal resistance and high energy density.

[0055] Among them, the material of the separator can be a single-layer separator or a composite separator. The material of the separator can be one or several of polyethylene, polypropylene, polyvinylidene fluoride, cellulose, fluoropolymer, etc. and their multi-layer composite films. The surface of the separator can have a coating or can be without a coating, as long as the above-mentioned required distance between the positive electrode sheet and the negative electrode sheet can be achieved. That is, by setting a separator with a certain thickness between the positive electrode sheet and the negative electrode sheet, the required distance between the positive electrode sheet and the negative electrode sheet can be maintained.

[0056] In some embodiments, the sodium-ion battery monomer is injected with an electrolyte, and the electrolyte includes a carbonate solvent. The carbonate solvent has low toxicity, is environmentally friendly, and at the same time has good oxidation resistance and good stability when contacting the negative electrode sheet. Therefore, such an electrolyte has good electrochemical stability when used in the sodium-ion battery monomer. Combining the minimum distance between the positive electrode sheet and the negative electrode sheet in this application can further extend the life of the battery.

[0057] Specifically, the electrolyte includes an electrolyte sodium salt and a carbonate solvent. The electrolyte sodium salt plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The electrolyte sodium salt can be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorophosphate, and sodium difluoro(oxalato)borate. The carbonate solvent in the electrolyte can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, and fluoroethylene carbonate.

[0058] In some embodiments, the electrolyte may optionally further include additives. For example, the additives can include film-forming additives, and can also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0059] In some embodiments, the positive electrode plate of the sodium-ion battery monomer includes a positive electrode current collector and a positive electrode active material layer bonded to at least one surface of the positive electrode current collector.

[0060] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0061] In some embodiments, the positive electrode active material layer includes a sodium-ion battery positive electrode active material. Specifically, it is a sodium layered metal oxide, mainly including sodium layered metal oxides (Na x MO2, where M = Fe, Mn, Ni, Co, Cr and their combinations), such as layered sodium nickel cobalt aluminum oxide (NCA), sodium nickel cobalt manganese oxide (NCM), and sodium iron phosphate (NASICON), etc. By selecting the sodium-ion battery positive electrode active material, it has a certain capacity per unit area and is also beneficial to prevent its thermal runaway within the parameter range set in the embodiments of the present application.

[0062] In some embodiments, the positive electrode active material layer may further optionally include a binder and a conductive agent. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0063] In some embodiments, the negative electrode sheet of the sodium ion battery monomer includes a negative electrode current collector and a negative electrode active material layer bonded to at least one surface of the negative electrode current collector.

[0064] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.

[0065] In some embodiments, the negative electrode active material layer includes a negative electrode active material. Specifically, it mainly includes hard carbon. By selecting the negative electrode active material of the sodium ion battery, it has a certain capacity per unit area.

[0066] In some embodiments, the negative electrode active material layer may further optionally include a binder and a conductive agent. As an example, the binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] It should be noted that the positive current collector and the negative current collector each have two surfaces opposite to each other in their own thickness directions. The positive active material layer is disposed on either one or both of the two opposite surfaces of the positive current collector, and the negative active material layer is disposed on either one or both of the two opposite surfaces of the negative current collector. Each parameter (such as specific capacity, areal density, capacity per unit area, etc.) given in the embodiments of the present application refers to the parameter of the active material layer on one side of the positive current collector or the negative current collector. For example, it can be the parameter of the active material layer opposite to the separator. When the positive active material layer is disposed on both sides of the positive current collector, the parameter of the positive active material layer on either side satisfies the present application, and it is considered to fall within the protection scope of the present application. When the negative active material layer is disposed on both sides of the negative current collector, the parameter of the negative active material layer on either side satisfies the present application, and it is considered to fall within the protection scope of the present application.

[0068] In some embodiments, a sodium-ion battery cell refers to a battery cell including a battery case and an electrode assembly encapsulated in the battery case. The shape of the sodium-ion battery cell is not particularly limited, and it can be cylindrical, square, or any other shape. As Figure 1 shown, the square-structured sodium-ion battery cell 10.

[0069] In some embodiments, as Figure 2 shown, the outer package of the sodium-ion battery cell 10 may include a case 11 and a top cover assembly 12. The case 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The case 11 has an opening communicating with the receiving cavity, and the top cover assembly 12 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the separator, and the negative electrode sheet included in the sodium-ion battery cell of the embodiments of the present application can form an electrode assembly 13 through a winding process and / or a stacking process. The electrode assembly 13 is encapsulated in the receiving cavity. For a liquid sodium-ion battery cell, the electrolyte is infiltrated in the electrode assembly 13. The number of the electrode assemblies 13 included in the sodium-ion battery cell 10 can be one or more, and can be adjusted according to actual needs.

[0070] The preparation method of the sodium-ion battery cell 10 is well-known. In some embodiments, taking a liquid sodium-ion battery cell as an example, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form the sodium-ion battery cell 10. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly 13 through a winding process or a stacking process, the electrode assembly 13 is placed in the outer package, dried, and then the electrolyte is injected, and after processes such as vacuum packaging, standing, formation, and shaping, the sodium-ion battery cell 10 is obtained.

[0071] In a second aspect, an embodiment of the present application provides a battery, including the sodium-ion battery monomer provided in the first aspect of the embodiment of the present application. Based on the adoption of the sodium-ion battery monomer of the embodiment of the present application, such a battery is not easily thermally out of control, and thus has good safety performance.

[0072] In some embodiments, the battery of the embodiment of the present application is a secondary battery, and the secondary battery may include any one of a battery monomer, a battery module, and a battery pack.

[0073] The battery module refers to being assembled by the sodium-ion battery monomer 10, that is, it may contain a plurality of the sodium-ion battery monomers 10, and the specific number may be adjusted according to the application and capacity of the battery module.

[0074] In some embodiments, Figure 3 is a schematic diagram of a battery module 20 as an example. As Figure 3 shown, in the battery module 20, a plurality of sodium-ion battery monomers 10 may be arranged in sequence along the length direction of the battery module 20. Of course, they may also be arranged in any other manner. Further, the plurality of sodium-ion battery monomers 10 may be fixed by fasteners. Optionally, the battery module 20 may further include a housing having an accommodation space, and the plurality of sodium-ion battery monomers 10 are accommodated in the accommodation space.

[0075] The battery pack refers to being assembled by the sodium-ion battery monomer 10 above, that is, it may contain a plurality of sodium-ion battery monomers 10. Among them, the plurality of sodium-ion battery monomers 10 may be assembled into the battery module 20 above. The specific number of the sodium-ion battery monomers 10 or battery modules 20 contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0076] As in the embodiment, Figure 4 and Figure 5 are schematic diagrams of a battery pack 30 as an example. The battery pack 30 may include a battery box and a plurality of battery modules 20 disposed in the battery box. The battery box includes an upper box body 31 and a lower box body 32. The upper box body 31 is used to cover the lower box body 32 and form a closed space for accommodating the battery module 20. The plurality of battery modules 20 may be arranged in the battery box in any manner.

[0077] Power-consuming device

[0078] In a third aspect, an embodiment of the present application further provides a power-consuming device, which includes the sodium-ion battery monomer or the battery of the above embodiment of the present application. The sodium-ion battery monomer or the battery may be used as the power supply of the power-consuming device or as the energy storage unit of the power-consuming device. Based on the advantages of the sodium-ion battery of the embodiment of the present application, such a power-consuming device is not easily thermally out of control, has good safety, and can work for a longer time.

[0079] The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc. The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0080] Figure 6 It is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module can be adopted.

[0081] The electrical device as another example can be a mobile phone, a tablet computer, a laptop computer, etc. The electrical device usually requires being thin and light, and a sodium-ion battery can be adopted as the power source.

[0082] Embodiment

[0083] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific techniques or conditions noted in the embodiments, the techniques or conditions described in the literature in this field or according to the product specification are followed. For the reagents or instruments without the producer noted, they are all conventional products that can be obtained through commercial purchase.

[0084] Embodiment 1

[0085] A battery cell, which is a liquid sodium-ion battery cell, includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. The specific preparation steps are as follows:

[0086] Preparation of the positive electrode plate:

[0087] Using N-methylpyrrolidone (NMP) as a solvent, layered sodium nickel cobalt aluminum oxide, conductive carbon black, and polyvinylidene fluoride binder are mixed and dissolved in the solvent at a mass ratio of 95:2:3 to form a positive electrode slurry; the positive electrode slurry is uniformly coated on an aluminum foil, and double-sided coating is carried out. After sufficient vacuum drying, cold pressing, and slitting, a positive electrode plate is obtained. The areal density of the layered sodium nickel cobalt aluminum oxide on each single side is 0.02 g / cm 2 , and the sodium extraction capacity of the layered sodium nickel cobalt aluminum oxide is 150 mAh / g.

[0088] Preparation of the negative electrode plate:

[0089] Using water as the solvent, a negative electrode slurry is prepared by mixing hard carbon active material, conductive carbon black, and carboxymethyl cellulose binder in a mass ratio of 95:2:3 and dissolving them in the solvent. The negative electrode slurry is uniformly coated on aluminum foil, and double-sided coating is carried out. After sufficient vacuum drying, cold pressing, and slitting, the positive electrode sheet is obtained. The areal density of the hard carbon active material on each side is 0.01 g / cm 2 , and the sodium intercalation capacity of the hard carbon active material is 330 mAh / g.

[0090] Electrolyte: At room temperature, ethylene carbonate (EC) / diethyl carbonate (DEC) are mixed in a volume ratio of 1:1, and NaPF6 is added to the mixed solution to obtain a solution with a concentration of 1 mol / L as the electrolyte.

[0091] Separator: Polypropylene separator with a thickness of 20 μm.

[0092] Secondary battery assembly: In a constant temperature room, in an argon atmosphere glove box, the positive and negative electrode sheets prepared above are stacked in the order of "positive electrode - separator - negative electrode", filled with electrolyte, and assembled into a button-type sodium-ion battery monomer. The full charge voltage K is 4 V, and the capacity per unit area of the negative electrode sheet is the larger capacity per unit area X = 3.3 mAh / cm 2 .

[0093] Example 2

[0094] The difference from Example 1 is that:

[0095] The thickness of the separator is 30 μm, and the others are the same as in Example 1.

[0096] Example 3

[0097] The difference from Example 1 is that:

[0098] The thickness of the separator is 40 μm, and the others are the same as in Example 1.

[0099] Example 4

[0100] The difference from Example 1 is that:

[0101] The thickness of the separator is 45 μm, and the others are the same as in Example 1.

[0102] Example 5

[0103] The difference from Example 1 is that:

[0104] The sodium deintercalation capacity of the layered sodium nickel cobalt aluminum oxide is 170 mAh / g, and the areal density is 0.02 g / cm 2 ; the sodium intercalation capacity of the hard carbon active material is 350 mAh / g, and the areal density is 0.01 g / cm 2; The capacity per unit area of the negative electrode plate is a relatively large capacity per unit area X = 3.5 mAh / cm 2 ; The thickness of the separator is 21 μm, and the others are the same as in Example 1.

[0105] Example 6

[0106] The difference from Example 5 is that:

[0107] The thickness of the separator is 30 μm, and the others are the same as in Example 5.

[0108] Example 7

[0109] The difference from Example 5 is that:

[0110] The thickness of the separator is 35 μm, and the others are the same as in Example 5.

[0111] Example 8

[0112] The difference from Example 5 is that:

[0113] The thickness of the separator is 45 μm, and the others are the same as in Example 5.

[0114] Example 9

[0115] The difference from Example 1 is that:

[0116] The sodium extraction capacity per gram of the layered sodium nickel cobalt aluminum oxide is 100 mAh / g, and the surface density is 0.01 g / cm 2 ; The sodium insertion capacity per gram of the hard carbon active material is 200 mAh / g, and the surface density is 0.01 g / cm 2 ; The capacity per unit area of the negative electrode plate is a relatively large capacity per unit area X = 2 mAh / cm 2 ; The thickness of the separator is 15 μm, and the others are the same as in Example 1.

[0117] Example 10

[0118] The difference from Example 1 is that:

[0119] The sodium extraction capacity per gram of the layered sodium nickel cobalt aluminum oxide is 200 mAh / g, and the surface density is 0.02 g / cm 2 ; The sodium insertion capacity per gram of the hard carbon active material is 200 mAh / g, and the surface density is 0.006 g / cm 2 ; The capacity per unit area of the negative electrode plate is a relatively large capacity per unit area X = 2.4 mAh / cm 2 ; The thickness of the separator is 15 μm, and the others are the same as in Example 1.

[0120] Comparative Example 1

[0121] The difference from Example 1 is that:

[0122] The thickness of the separator membrane is 14 μm, and the others are the same as in Example 1.

[0123] Comparative Example 2

[0124] The difference from Example 1 is that:

[0125] The thickness of the separator membrane is 14 μm, and the others are the same as in Example 5.

[0126] Comparative Example 3

[0127] The difference from Example 5 is that:

[0128] The thickness of the separator membrane is 14 μm, and the others are the same as in Example 9.

[0129] Comparative Example 4

[0130] The difference from Example 5 is that:

[0131] The thickness of the separator membrane is 14 μm, and the others are the same as in Example 10.

[0132] Performance Test

[0133] The sodium-ion battery monomers of the above Examples and Comparative Examples were tested separately.

[0134] The safety test steps include:

[0135] Apply an 80 W (heating resistor) heat source to the electrode assembly of the sodium-ion battery monomer; detect the valve opening time; among them, detect the valve opening time of the explosion-proof valve of the electrode assembly under the thermal abuse test temperature condition of 200 °C. This time reflects the severity of the gas generation during the internal thermal runaway of the battery. The longer the time, the safer.

[0136] The test results of the above sodium-ion batteries are shown in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] It can be seen from Table 1 that for sodium-ion battery monomers, under certain conditions of unit area capacity and full charge voltage, when the thickness of the separator membrane laminated between the positive electrode plate and the negative electrode plate is 15 - 45 μm, it is not easy to have thermal runaway, and the safety of the sodium-ion battery is good.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A sodium-ion battery cell, comprising a positive electrode plate and a negative electrode plate arranged opposite to each other, characterized in that, The positive electrode sheet contains sodium layered metal oxide, and the negative electrode sheet contains hard carbon; The distance between the positive electrode sheet and the negative electrode sheet is 15 - 45 μm.

2. The sodium-ion battery cell according to claim 1, characterized in that, The sodium deintercalation capacity of the sodium layered metal oxide is 100 to 200 mAh / g, and the coating surface density of the sodium layered metal oxide is 0.01 to 0.04 g / cm 2 .

3. The sodium-ion battery cell according to claim 1 or 2, characterized in that, The sodium storage capacity of the hard carbon is 200 to 400 mAh / g, and the coating surface density of the hard carbon is 0.005 to 0.02 g / cm 2 .

4. The sodium-ion battery cell according to claim 3, characterized in that, The sodium extraction specific capacity of the sodium layered metal oxide is 140 - 170 mAh / g, and the sodium storage specific capacity of the hard carbon is 300 - 370 mAh / g.

5. The sodium-ion battery cell according to any one of claims 1-4, characterized in that, A separator is provided between the positive electrode sheet and the negative electrode sheet, and the thickness of the separator is less than or equal to that of the positive electrode sheet.

6. The sodium-ion battery cell according to any one of claims 1-5, characterized in that, The sodium ion battery cell further includes an electrolyte, and the electrolyte includes a carbonate solvent.

7. A battery, characterized in that, It includes at least two sodium ion battery cells according to any one of claims 1 - 6.

8. An electrical device, characterized in that, The electrical device includes the sodium ion battery cell according to any one of claims 1 - 6, or the battery according to claim 7.

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