Sodium battery, formation method of sodium battery, and electric device

Abstract

The application provides a sodium battery, a formation method of the sodium battery, and an electric device. Based on the total volume of the gas in the sodium battery shell, the total volume ratio of the inert gas is 15%-50%. After the first injection of the electrolyte is completed and before the sodium battery is started to be formed, the inert gas is introduced into the sodium battery shell, and the sodium battery is formed in the atmosphere of the gas including the inert gas in the sodium battery shell, so that the first coulomb efficiency of the sodium battery can be improved.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a sodium battery, a sodium battery formation method, and an electrical device. Background Technology

[0002] In recent years, rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the increasing application of rechargeable batteries, higher requirements have been placed on their cycle performance and service life.

[0003] Sodium batteries have the advantages of abundant resources, low cost, and good safety, but their low initial coulombic efficiency limits their further application. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its object is to provide a sodium battery having a high initial coulombic efficiency.

[0005] The first aspect of this application provides a sodium battery in which the total volume of inert gas accounts for 15%-50% of the total volume of gas inside the sodium battery casing.

[0006] In any embodiment, the total volume of inert gas accounts for 30%-45% of the total volume of gas inside the sodium battery casing.

[0007] In any embodiment, the inert gas includes one or more of argon, helium, and nitrogen.

[0008] In any embodiment, the sodium battery includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a polyanionic compound.

[0009] In any embodiment, the polyanionic compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanionic compounds, wherein M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb and Zr.

[0010] In any embodiment, the polyanionic compound includes at least one of sodium iron pyrophosphate, sodium vanadium phosphate, and sodium iron pyrophosphate.

[0011] In any embodiment, the sodium battery includes a negative electrode-free sodium battery and a sodium metal battery.

[0012] The second aspect of this application provides a method for forming a sodium battery, comprising the following steps: injecting an electrolyte into a sodium battery casing; introducing an inert gas into the sodium battery casing; and forming the sodium battery; wherein, after the introduction of the inert gas and before the formation of the sodium battery begins, the step of evacuating the sodium battery casing is not included.

[0013] Studies have shown that during the initial charging and formation process of sodium batteries, the active sodium released from the positive electrode active material easily combines with reactive gases such as oxygen and carbon dioxide adhering to the surface of the positive electrode active material, resulting in partial loss of the released active sodium. This reduces the initial discharge capacity of the battery and thus deteriorates the initial coulombic efficiency of the sodium battery. The sodium battery formation method of this application introduces an inert gas into the battery casing after electrolyte injection and before the start of formation. This allows the formation of the sodium battery to take place in an atmosphere containing an inert gas within the battery casing. The inert gas in the casing dilutes the concentration of reactive gases adsorbed on the surface of the positive electrode active material and inhibits the combination of the released active sodium with reactive gases during formation, reducing the loss of active sodium and thus improving the initial coulombic efficiency of the sodium battery.

[0014] In any embodiment, the inert gas includes one or more of argon, helium, and nitrogen.

[0015] In any embodiment, the pressure of the inert gas introduced is 25 kPa-100 kPa.

[0016] The inert gas pressure is within the above range, which ensures production efficiency while preventing cell deformation due to excessive gas pressure.

[0017] In any embodiment, the inert gas is introduced for 2s-15s.

[0018] When the inert gas introduction time is within the above range, the sodium battery exhibits good initial coulombic efficiency and production efficiency.

[0019] In any embodiment, an inert gas is introduced 1 to 6 hours after the electrolyte injection is completed.

[0020] After electrolyte is injected into the sodium battery casing, the positive electrode active material is wetted by the electrolyte. With the electrolyte as the medium, oxygen adsorbed on the surface of the positive electrode active material easily oxidizes it, causing it to transform into a desodium-free state. This results in irreversible loss of active sodium that can contribute to capacity, reducing the total amount of active sodium that can be removed from the positive electrode active material during the formation process. This leads to a decrease in the initial charging capacity of the sodium battery, thus worsening its initial coulombic efficiency. Introducing inert gas 1-6 hours after electrolyte injection allows some of the gas adsorbed on the surface of the positive electrode active material to escape naturally and reduces the reaction between the positive electrode active material and the oxygen adsorbed on its surface under electrolyte conditions. This reduces the loss of active sodium and improves the initial coulombic efficiency of the sodium battery.

[0021] In any embodiment, the sodium battery includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material including a polyanionic compound.

[0022] In any embodiment, the polyanionic compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanionic compounds, wherein M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb and Zr.

[0023] In any embodiment, the polyanionic compound includes at least one of sodium iron pyrophosphate, sodium vanadium phosphate, and sodium iron pyrophosphate.

[0024] After electrolyte is injected into the sodium battery casing, the aforementioned positive electrode active material is easily oxidized to a desodium state by oxygen under the action of the electrolyte as a medium, resulting in irreversible loss of active sodium. Furthermore, during the first charge, the active sodium released from the positive electrode active material easily combines with reactive gases, further leading to irreversible loss of active sodium and thus deteriorating the initial coulombic efficiency of the sodium battery. After the initial electrolyte injection, introducing an inert gas into the battery casing can dilute the concentration of reactive gases adsorbed on the surface of the positive electrode active material and inhibit the related chemical reactions that lead to the loss of active sodium, thereby improving the initial coulombic efficiency of the sodium battery.

[0025] In any embodiment, the sodium battery includes a negative electrode-free sodium battery and a sodium metal battery.

[0026] In electrodeless sodium batteries and sodium metal batteries, after the first charge, active sodium ions released from the positive electrode active material are reduced and deposited on the negative electrode as a sodium metal layer. The highly reducing sodium metal readily reacts with oxygen within the battery casing, causing irreversible loss of active sodium and severely degrading the battery's initial coulombic efficiency. After electrolyte injection, introducing an inert gas into the battery casing allows the sodium battery formation to occur within an atmosphere containing this inert gas, significantly improving the initial coulombic efficiency of electrodeless sodium batteries and sodium metal batteries.

[0027] A third aspect of this application also provides an electrical device, including a sodium battery of the first aspect or a sodium battery prepared using the formation method of the second aspect. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a sodium battery according to one embodiment of this application;

[0029] Figure 2 yes Figure 1 An exploded view of a sodium battery according to an embodiment of this application is shown.

[0030] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0031] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0032] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0033] Figure 6 This is a schematic diagram of an electrical device using a sodium battery as a power source according to one embodiment of this application.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Sodium battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0036] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the sodium battery, the method for forming the sodium battery, and the power-consuming device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0042] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0043] Sodium batteries offer advantages such as low cost, abundant resources, and good safety. However, they exhibit low coulombic efficiency during the first charge-discharge cycle, which hinders their further applications. The formation process is a crucial step in sodium battery manufacturing. During formation, gases such as oxygen and carbon dioxide present within the casing can cause irreversible loss of the active sodium provided by the positive electrode material, thus worsening the initial coulombic efficiency of the sodium battery.

[0044] [Formation method of sodium battery]

[0045] Based on this, this application proposes a sodium battery formation method, comprising the following steps: injecting electrolyte into the sodium battery casing; introducing inert gas into the sodium battery casing; and forming the sodium battery; wherein, after the introduction of inert gas is completed and before the formation of the sodium battery begins, the step of evacuating the sodium battery casing is not included.

[0046] In this article, the term "sodium battery casing" refers to the outer packaging of the electrode assembly consisting of the positive electrode, negative electrode, and separator.

[0047] In some embodiments, the housing includes a cylindrical housing, a square housing, or a soft housing.

[0048] In this article, the term "inert gas" refers to a gas that is chemically very stable and difficult to react with other substances.

[0049] In this article, the term "formation" refers to the process of initial charging after the electrode assembly and battery casing are assembled and the electrolyte is first injected into the sodium battery casing.

[0050] In this article, the term "vacuuming" refers to removing gas from a container or system, causing the gas pressure inside the container or system to drop to a certain range, thereby achieving a vacuum state.

[0051] In this paper, the term "first coulombic efficiency" refers to the ratio of the first discharge capacity to the first charge capacity of a full cell.

[0052] In some embodiments, the inert gas includes one or more of argon, helium, and nitrogen.

[0053] Studies have shown that during the initial charging and formation process of sodium batteries, the active sodium released from the positive electrode active material easily combines with reactive gases such as oxygen and carbon dioxide adhering to the surface of the positive electrode active material, resulting in partial loss of the released active sodium. This reduces the initial discharge capacity of the battery and thus deteriorates the initial coulombic efficiency of the sodium battery. The sodium battery formation method of this application introduces an inert gas into the battery casing after electrolyte injection and before the start of formation. This allows the formation of the sodium battery to take place in an atmosphere containing an inert gas within the battery casing. The inert gas in the casing dilutes the concentration of reactive gases adsorbed on the surface of the positive electrode active material and inhibits the combination of the released active sodium with reactive gases during formation, reducing the loss of active sodium and thus improving the initial coulombic efficiency of the sodium battery.

[0054] In some embodiments, injecting electrolyte into the sodium battery casing includes: evacuating the sodium battery casing to a vacuum of -5 kPa to 30 kPa, and then injecting electrolyte into the sodium battery casing.

[0055] Before injecting electrolyte into a sodium battery after evacuating the casing, the pressure difference between the inside and outside of the casing can drive the electrolyte into the casing. However, evacuation cannot remove reactive gases adsorbed on the surface of the positive electrode active material. After electrolyte injection and before the formation process begins, an inert gas is introduced into the battery casing. This allows the formation of the sodium battery to take place in an atmosphere containing inert gas within the casing. This dilutes the concentration of reactive gases and inhibits their reaction with the active sodium released from the positive electrode active material during formation. Compared to evacuation, introducing an inert gas into the sodium battery casing can improve the initial coulombic efficiency of the sodium battery.

[0056] In some implementations, the pressure of the inert gas introduced is 25 kPa to 100 kPa.

[0057] In some embodiments, the inert gas pressure is 25 kPa, 40 kPa, 55 kPa, 70 kPa, 85 kPa, 100 kPa or any value between these values.

[0058] The inert gas pressure is within the above range, which ensures production efficiency while preventing cell deformation due to excessive gas pressure.

[0059] In some implementations, the inert gas is introduced for 2-15 seconds.

[0060] In some embodiments, the inert gas is introduced for a time of 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 11s, 12s, 13s, 14s, 15s or any value between these values.

[0061] When the inert gas introduction time is within the above range, the sodium battery exhibits good initial coulombic efficiency and production efficiency.

[0062] In some implementations, an inert gas is introduced 1 to 6 hours after the electrolyte injection is completed.

[0063] In some embodiments, an inert gas is introduced 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours or any value in between after the electrolyte injection is completed.

[0064] After electrolyte is injected into the sodium battery casing, the positive electrode active material is wetted by the electrolyte. With the electrolyte as the medium, oxygen adsorbed on the surface of the positive electrode active material easily oxidizes it, causing it to transform into a desodium-free state. This results in irreversible loss of active sodium that can contribute to capacity, reducing the total amount of active sodium that can be removed from the positive electrode active material during the formation process. This leads to a decrease in the initial charging capacity of the sodium battery, thus worsening its initial coulombic efficiency. Introducing inert gas 1-6 hours after electrolyte injection allows some of the gas adsorbed on the surface of the positive electrode active material to escape naturally and reduces the reaction between the positive electrode active material and the oxygen adsorbed on its surface under electrolyte conditions. This reduces the loss of active sodium and improves the initial coulombic efficiency of the sodium battery.

[0065] In some embodiments, the formation method of sodium batteries also includes: standing for 6 to 36 hours.

[0066] In some embodiments, the formation method of a sodium battery includes the following steps: injecting an electrolyte into a sodium battery casing; allowing it to stand for 6 to 36 hours; introducing an inert gas into the sodium battery casing; and forming the sodium battery; wherein, after the introduction of the inert gas is completed and before the formation of the sodium battery begins, the step of evacuating the sodium battery casing is not included.

[0067] In some embodiments, the formation method of a sodium battery includes the following steps: injecting an electrolyte into a sodium battery casing; introducing an inert gas into the sodium battery casing; allowing it to stand for 6 to 36 hours; and forming the sodium battery; wherein, after the introduction of the inert gas is completed and before the formation of the sodium battery begins, the step of evacuating the sodium battery casing is not included.

[0068] After the electrolyte is first injected into the sodium battery housing, it needs to be left standing for a long time to allow the electrolyte to fully wet the positive electrode plate, the negative electrode plate, and the separator. Before the start of the long-term standing after the electrolyte injection is completed, an inert gas is introduced into the sodium battery housing to avoid the reaction between the positive active material and the oxygen adsorbed on the surface of the positive active material under the condition of the electrolyte as a medium caused by the long-term standing, reduce the loss of active sodium, and improve the first Coulomb efficiency of the sodium battery.

[0069] In some embodiments, the sodium battery includes a positive electrode plate, the positive electrode plate includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector, and the positive electrode film layer includes a positive active material.

[0070] In some embodiments, the positive active material can be a positive active material for batteries well-known in the art. As an example, the positive active material can include at least one of the following materials: Prussian blue analogs, sodium-containing phosphates, sodium-containing transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive active material of the battery can also be used. These positive active materials can be used alone or in combination of two or more. Among them, the Prussian blue analog is Na

[0072] , , ,

[0071] P[R(CN)6] δ ·zH2O, where P and R are each independently selected from at least one of the transition metal elements, 0 < x ≤ 2, 0 < δ ≤ 1 and 0 ≤ z ≤ 10; the sodium-containing phosphate is Na b Me c (PO4) d O2X, where A is one or more of H, Li, Na, K and NH4, Me is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X is one or more of F, Cl and Br, 0 < b ≤ 4, 0 < c ≤ 2, 1 ≤ d ≤ 3; the sodium-containing transition metal oxide is Na a M b N c Fe d Mn e O2, M and N include at least one of Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb, 0.05 ≤ b ≤ 0.2, 0.2 ≤ c ≤ 0.3, 0.2 ≤ d ≤ 0.3, 0.3 ≤ e ≤ 0.4, 0.75 ≤ a / (b + c + d + e) ≤ 1.

[0071] In some embodiments, the positive active material includes a polyanion compound.

[0072] In this paper, the term "polyanionic compound" refers to a group of compounds with a three-dimensional network structure formed by strong covalent bonds connecting tetrahedral and polyhedral anionic structural units.

[0073] In some embodiments, the polyanionic compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanionic compounds, wherein M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb and Zr.

[0074] In this article, the term "phosphate" refers to PO43-. - .

[0075] In this article, the term "pyrophosphate" refers to P2O7. 4- .

[0076] In some embodiments, the polyanionic compound includes at least one of sodium ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

[0077] The aforementioned positive electrode active material is easily oxidized to a desodium state by oxygen under the action of the electrolyte as a medium, leading to irreversible loss of active sodium. Furthermore, during the first charge, the active sodium released from the positive electrode active material easily combines with reactive gases, further resulting in irreversible loss of active sodium and thus deteriorating the initial coulombic efficiency of the sodium battery. After the initial electrolyte filling, an inert gas is introduced into the battery casing. The inert gas inside the casing can dilute the concentration of reactive gases adsorbed on the surface of the positive electrode active material and inhibit the related chemical reactions that lead to the loss of active sodium, thereby improving the initial coulombic efficiency of the sodium battery.

[0078] In some implementations, sodium batteries include negative electrode-free sodium batteries and sodium metal batteries.

[0079] In this article, the term "negative electrode-free sodium battery" refers to a battery in which a negative electrode active material layer is not actively deposited on the negative electrode side during the battery manufacturing process. For example, a negative electrode active material layer is not formed at the negative electrode through processes such as coating or deposition. During the first charge, sodium ions gain electrons on the anode side and deposit metallic sodium on the surface of the current collector to form a sodium metal phase. During discharge, the metallic sodium can be converted back into sodium ions and return to the positive electrode, achieving cyclic charging and discharging.

[0080] In this article, the term "sodium metal battery" refers to a secondary battery prepared by pre-depositing sodium metal or its alloy onto the negative electrode during the battery manufacturing process.

[0081] In electrodeless sodium batteries and sodium metal batteries, after the first charge, active sodium ions released from the positive electrode active material are reduced and deposited on the negative electrode as a sodium metal layer. The highly reducing sodium metal readily reacts with oxygen within the battery casing, causing irreversible loss of active sodium and severely degrading the battery's initial coulombic efficiency. After electrolyte injection, introducing an inert gas into the battery casing allows the sodium battery formation to occur within an atmosphere containing this inert gas, significantly improving the initial coulombic efficiency of electrodeless sodium batteries and sodium metal batteries.

[0082] Sodium batteries

[0083] This application also provides a sodium battery, wherein the total volume of inert gas inside the sodium battery casing accounts for 15%-50% of the total volume of the gas inside the sodium battery casing.

[0084] In some embodiments, the inert gas includes one or more of argon, helium, and nitrogen.

[0085] In this application, the total volume percentage of inert gas within the sodium battery casing can be tested using methods known in the art, such as gas composition analysis-gas chromatography, according to GB / T 9722-2006. The testing principle is as follows: After the sample and its analyte are vaporized, they simultaneously enter the chromatographic column along with the carrier gas (usually oxygen). The differences in the physicochemical properties of the analyte between the gas-solid or gas-liquid phases, such as adsorption, dissolution, desorption, or desorption, create differences in the migration rates of the components within the column, leading to separation. The separated components elute sequentially from the column and enter the detector. The data processing system records the chromatographic column and corresponding data. The retention values ​​and peak areas or corresponding peak heights of each component serve as the basis for qualitative or quantitative analysis, respectively. Operating procedure: Sample volume: 1 mL; split ratio: 5:1; TCD (thermal conductivity detector) is used. After balancing the instrument, a quantitative amount of gas is extracted from the sodium battery casing using a gas injection needle. The gas is then injected through the injection port for GC-TCD analysis to obtain the volume percentage of each inert gas. The total volume percentage of inert gases is calculated based on the total volume of gas inside the sodium battery casing.

[0086] In some embodiments, the total volume percentage of the inert gas inside the sodium battery casing is 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between these values, based on the total volume of the gas inside the sodium battery casing.

[0087] In any embodiment, the total volume of inert gas accounts for 30%-45% of the total volume of gas inside the sodium battery casing.

[0088] In some embodiments, the sodium battery includes a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material.

[0089] In some embodiments, the positive electrode active material can be a positive electrode active material for batteries well-known in the art. As an example, the positive electrode active material can include at least one of the following materials: Prussian blue analogs, sodium-containing phosphates, sodium-containing transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, the Prussian blue analog is Na x P[R(CN)6] δ ·zH2O, where P and R are each independently selected from at least one of transition metal elements, 0 < x ≤ 2, 0 < δ ≤ 1, and 0 ≤ z ≤ 10; the sodium-containing phosphate is Na b Me c (PO4) d O2X, where A is one or more of H, Li, Na, K, and NH4, Me is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X is one or more of F, Cl, and Br, 0 < b ≤ 4, 0 < c ≤ 2, 1 ≤ d ≤ 3; the sodium-containing transition metal oxide is Na a M b N c Fe d Mn e O2, M and N include at least one of Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, and Pb, 0.05 ≤ b ≤ 0.2, 0.2 ≤ c ≤ 0.3, 0.2 ≤ d ≤ 0.3, 0.3 ≤ e ≤ 0.4, 0.75 ≤ a / (b + c + d + e) ≤ 1.

[0090] In some embodiments, the positive electrode active material includes a polyanion compound.

[0091] In some embodiments, the polyanion compound includes one or more of Na3M2(PO4)3, Na2XP2O7, and a mixed polyanion compound of phosphate and pyrophosphate groups, where M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb, and Zr.

[0092] In some embodiments, the polyanion compound includes at least one of sodium iron pyrophosphate phosphate, sodium vanadium phosphate, and sodium iron pyrophosphate.

[0093] In some implementations, sodium batteries include negative electrode-free sodium batteries and sodium metal batteries.

[0094] [Positive electrode plate]

[0095] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0096] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0097] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0099] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0101] [Negative electrode plate]

[0102] In some implementations, the secondary battery is a negative electrode-less battery.

[0103] In some implementations, the negative electrode includes a negative current collector.

[0104] In some implementations, to improve battery performance, the negative electrode side of a negative electrode-free battery can be provided with materials that can be conventionally used as negative electrode active materials, such as carbonaceous materials, metal oxides, alloys, etc. Although these materials have a certain capacity, because the amount of these materials is small, they are not used as the main negative electrode active materials in the battery, and therefore are not considered to form a negative electrode active material layer that plays a role in lithium or sodium intercalation. The secondary battery constructed in this way can still be regarded as a negative electrode-free battery.

[0105] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0106] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer can be disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil or aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0109] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0110] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0112] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0113] [Electrolytes]

[0114] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0115] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0116] In some embodiments, the electrolyte includes an electrolyte salt selected from at least one of NaPF6, NaBF4, NaN(SO2F)2 (NaFSI), NaClO4, NaAsF6, NaB(C2O4)2 (NaBOB), NaBF2(C2O4) (NaDFOB), NaN(SO2RF)2, and NaN(SO2F) (SO2RF), wherein RF represents C b F 2b+1 b is an integer between 1 and 10, and can be an integer between 1 and 3.

[0117] In some embodiments, the electrolyte salt is selected from one or more of NaPF6, NaN(SO2F)2, NaN(CF3SO2)2, NaB(C2O4)2, and NaBF2(C2O4). In some embodiments, the electrolyte salt is selected from one or more of NaPF6, NaN(SO2RF)2, and NaBF2(C2O4). In some embodiments, RF is -CF3, -C2F5, or -CF2CF2CF3.

[0118] In some embodiments, the electrolyte includes a solvent, which includes at least one selected from chain carbonates, chain carboxylic esters, cyclic carbonates, ether solvents, sulfone solvents, and nitrile solvents. In some embodiments, the chain carbonate includes at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and dibutyl carbonate. In some embodiments, the chain carbonate includes at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and methyl propyl carbonate (MPC). In some embodiments, the chain carboxylic ester includes at least one selected from methyl formate (MF), ethyl formate (EF), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate (EB), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA). In some embodiments, the chain carboxylic ester includes at least one selected from methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA), and propyl acetate (PA). In some embodiments, the ether solvent includes at least one selected from dioxolane (DOL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2Me-THF), tetrahydropyran (THP), 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether (DG), 1,2-diethoxyethane, and 1,2-dibutoxyethane.

[0119] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0120] [Isolation membrane]

[0121] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0122] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0123] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0124] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0125] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0126] In this application, the shape of the sodium battery includes, but is not limited to, cylindrical, square, or other arbitrary shapes. For example, Figure 1 This is an example of a sodium battery with a square structure.

[0127] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The sodium battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0128] In some embodiments, sodium batteries can be assembled into battery modules, and the number of sodium batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0129] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple sodium batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple sodium batteries 5 can be fixed in place using fasteners.

[0130] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of sodium batteries 5 are housed.

[0131] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0132] Figure 4 and Figure 5This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0133] In addition, this application also provides an electrical device, which includes at least one of the sodium battery, battery module, or battery pack provided in this application. The sodium battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0134] As an electrical device, sodium batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0135] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of sodium batteries for this device, a battery pack or battery module can be used.

[0136] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use sodium batteries as their power source.

[0137] Example

[0138] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0139] I. Preparation Method

[0140] Example 1:

[0141] 1) Preparation of negative electrode sheet

[0142] 5g of sodium carboxymethyl cellulose (CMC-Na) was weighed and dissolved in 1000mL of water. Then, 5g of single-walled carbon nanotubes were added, and the mixture was ultrasonically dispersed to prepare a slurry. The slurry was coated onto the surface of the copper foil of the negative electrode current collector, and after drying, slitting, and cutting, the negative electrode sheet was obtained.

[0143] 2) Preparation of positive electrode sheet

[0144] The positive electrode active material sodium iron phosphate pyrophosphate, the conductive agent carbon nanotubes, and the binder metahexafluorophosphate were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to form a uniform positive electrode slurry. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die cutting, a positive electrode sheet with a thickness of 200 μm was obtained.

[0145] 3) Preparation of electrolyte

[0146] In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), diethylene glycol dimethyl ether and tetrahydrofuran were mixed at a mass ratio of 1:3, sodium hexafluorophosphate (NaPF6) was added, and the mixture was stirred evenly to obtain an electrolyte with a NaPF6 concentration of 1mol / L.

[0147] 4) Separating membrane

[0148] A 9μm porous polyethylene (PE) polymer film was used as the separator.

[0149] 5) Preparation of sodium batteries

[0150] The positive electrode, separator, and negative electrode obtained in the above steps are stacked in sequence, such that the separator is between the positive electrode and the negative electrode and can isolate the positive electrode and the negative electrode; then the stacked components are wound to obtain the electrode assembly.

[0151] The electrode assembly was placed in a square housing, hot-pressed and shaped, and subjected to a helium test. After the helium test, it was baked and dried, and the electrolyte prepared above was injected into the sodium battery housing. One hour after the electrolyte injection, argon gas at a pressure of 50 kPa was introduced into the housing for 5 seconds. After standing for 24 hours, the sodium battery was charged at a constant current of 0.33C to a voltage of 3.65V at 45°C in an atmosphere containing inert gas. Then, it was charged at a constant voltage until the current was less than 0.05C, and open-cell formation at atmospheric pressure was performed.

[0152] After formation, the battery was left to stand and reshape before undergoing capacity testing. It was then discharged at a constant current of 0.33C until the voltage reached 1.5V to obtain the initial discharge capacity. After sealing the casing with sealing nails and undergoing final helium testing, the negative electrode-free sodium battery of Example 1 was obtained.

[0153] Examples 2-4

[0154] The preparation methods of sodium batteries in Examples 2-4 are basically the same as those in Example 1, except that the types of inert gases introduced are different. Helium was introduced in Example 2, nitrogen was introduced in Example 3, and a mixed gas with a volume ratio of argon:helium:nitrogen of 1:1:1 was introduced in Example 4. The specific parameters are shown in Table 1.

[0155] Example 5

[0156] The preparation method of the sodium battery in Example 5 is basically the same as that in Example 1, except that the pressure of the introduced argon gas is 25 kPa. The specific parameters are shown in Table 1.

[0157] Example 6

[0158] The preparation method of the sodium battery in Example 6 is basically the same as that in Example 1, except that the pressure of the introduced argon gas is 100 kPa. The specific parameters are shown in Table 1.

[0159] Example 7

[0160] The preparation method of the sodium battery in Example 7 is basically the same as that in Example 1, except that the argon gas is continuously introduced for 2 seconds. The specific parameters are shown in Table 1.

[0161] Example 8

[0162] The preparation method of the sodium battery in Example 8 is basically the same as that in Example 1, except that the argon gas is continuously introduced for 15 seconds. The specific parameters are shown in Table 1.

[0163] Example 9

[0164] The preparation method of the sodium battery in Example 9 is basically the same as that in Example 1, except that:

[0165] The prepared electrolyte was injected into the sodium battery casing. Six hours after the injection was completed, argon gas at a pressure of 50 kPa was introduced into the casing for 5 seconds. After standing for 12 hours, the sodium battery was formed in an atmosphere containing inert gas inside the casing.

[0166] Example 10

[0167] The preparation method of the sodium battery in Example 10 is basically the same as that in Example 1, except that:

[0168] The prepared electrolyte was injected into the sodium battery casing. After 12 hours, argon gas at a pressure of 50 kPa was introduced into the casing for 5 seconds. After standing for 12 hours, the sodium battery was formed in an atmosphere containing inert gas inside the casing.

[0169] Example 11

[0170] The preparation method of the sodium battery in Example 11 is basically the same as that in Example 1, except that Example 11 is a hard carbon negative electrode sodium battery, and the preparation method of the negative electrode sheet is as follows:

[0171] Hard carbon, conductive carbon black, and sodium carboxymethyl cellulose binder were thoroughly mixed in a deionized water solvent system at a mass ratio of 90:5:5 to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto a copper foil current collector. After the copper foil was dried at room temperature, it was transferred to a 120°C oven to dry for 1 hour. Then, it was cold-pressed and slit to obtain a negative electrode sheet.

[0172] Comparative Example 1

[0173] The preparation method of sodium battery in Comparative Example 1 is basically the same as that in Example 1. The difference is that after the electrolyte is injected and before the sodium battery begins to form, no inert gas is introduced into the sodium battery casing. The specific parameters are shown in Table 1.

[0174] Comparative Example 2

[0175] The preparation method of the sodium battery in Comparative Example 2 is basically the same as that in Example 1, except that the battery casing is evacuated to a pressure of -30 kPa before the sodium battery is formed. The specific parameters are shown in Table 1.

[0176] Comparative Example 3

[0177] The preparation method of sodium battery in Comparative Example 3 is basically the same as that in Example 11. The difference is that after the electrolyte is injected and before the sodium battery begins to form, no inert gas is introduced. The specific parameters are shown in Table 2.

[0178] II. Battery Performance Testing

[0179] 1. First Coulomb efficiency test

[0180] The initial coulombic efficiency was tested during the preparation of sodium batteries in Examples 1-11 and Comparative Examples 1-3. The initial charge capacity C1 was taken as the charge capacity at the end of formation, and the initial discharge capacity C2 was taken as the discharge capacity at the time of capacity test. The initial coulombic efficiency of the battery was calculated as C2 / C1×100%.

[0181] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0182] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 1 and Table 2.

[0183] Table 1

[0184]

[0185] Table 2

[0186]

[0187] As can be seen from Examples 1-11, after injecting electrolyte into the sodium battery, an inert gas is introduced into the sodium battery casing. The sodium battery is formed in an atmosphere containing an inert gas inside the sodium battery casing, and the sodium battery exhibits excellent initial coulombic efficiency.

[0188] As can be seen from the comparison between Examples 1-10 and Comparative Examples 1-2, Example 11 and Comparative Example 3, after the electrolyte is injected into the sodium battery, an inert gas is introduced into the sodium battery casing. The sodium battery is formed in an atmosphere containing an inert gas, which is beneficial to improving the initial efficiency of the sodium battery.

[0189] As can be seen from Examples 1-4, when the sodium battery is formed in an atmosphere containing an inert gas, including one or more of argon, helium, and nitrogen, the sodium battery exhibits excellent initial efficiency.

[0190] As can be seen from Examples 1, 5, and 6, when the pressure of the inert gas introduced into the sodium battery casing is 25 kPa-100 kPa, the sodium battery has excellent initial efficiency.

[0191] As can be seen from Examples 1, 7, and 8, when the inert gas is introduced into the sodium battery casing for 2-15 seconds, the sodium battery exhibits excellent initial efficiency.

[0192] As can be seen from Examples 1 and 9, when an inert gas is introduced 1 to 6 hours after the electrolyte is injected into the sodium battery, the sodium battery exhibits excellent initial efficiency.

[0193] As can be seen from the comparison between Examples 1 and 9 and Example 10, introducing inert gas 1 to 6 hours after the sodium battery is injected with electrolyte is beneficial to improving the initial efficiency of the sodium battery.

[0194] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A sodium battery, comprising a negative electrode-free sodium battery and a sodium metal battery, characterized in that, Based on the total volume of gas inside the sodium battery casing, the inert gas accounts for 15% of the total volume. 50%, the inert gas is introduced after liquid injection and before formation.

2. The sodium battery according to claim 1, characterized in that, Based on the total volume of gas inside the sodium battery casing, the inert gas accounts for 30% of the total volume. 45%.

3. The sodium battery according to claim 1 or 2, characterized in that, The inert gas includes one or more of argon, helium, and nitrogen.

4. The sodium battery according to claim 1 or 2, characterized in that, The sodium battery includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a polyanionic compound.

5. The sodium battery according to claim 4, characterized in that, The polyanionic compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanionic compounds, wherein M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb and Zr.

6. The sodium battery according to claim 5, characterized in that, The polyanionic compound includes at least one of sodium ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

7. A method for forming a sodium battery, said sodium battery comprising a negative electrode-free sodium battery and a sodium metal battery, characterized in that, Includes the following steps: Electrolyte is injected into the sodium battery casing; An inert gas is introduced into the sodium battery casing. Based on the total volume of the gas inside the sodium battery casing, the total volume percentage of the inert gas is 15%. 50%; Formation of sodium batteries; The step of evacuating the sodium battery casing is not included after the inert gas is introduced and before the formation of the sodium battery begins.

8. The formation method according to claim 7, characterized in that, The inert gas includes one or more of argon, helium, and nitrogen.

9. The formation method according to claim 7 or 8, characterized in that, The pressure of the inert gas introduced is 25 kPa. 100 kPa; and / or, the inert gas is introduced for 2 seconds. 15s.

10. The formation method according to claim 7 or 8, characterized in that, 1 hour after the electrolyte injection is completed Inert gas was introduced after 6 hours.

11. The formation method according to claim 7 or 8, characterized in that, The sodium battery includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a polyanionic compound.

12. The formation method according to claim 11, characterized in that, The polyanionic compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanionic compounds, wherein M and X are each independently selected from one or more of Al, Ti, V, Fe, Cr, Mn, Co, Ni, Ca, Mg, Nb and Zr.

13. The formation method according to claim 11, characterized in that, The polyanionic compound includes at least one of sodium ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

14. The formation method according to claim 7 or 8, characterized in that, The sodium battery includes a negative electrode-free sodium battery and a sodium metal battery.

15. An electrical appliance, characterized in that, The sodium battery includes any one of claims 1 to 6 or a sodium battery prepared using the formation method of any one of claims 7 to 14.

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