Sodium battery, formation method of sodium battery and power utilization device

Abstract

The invention provides a sodium battery, a sodium battery formation method and a power utilization device. Based on the total volume of the gas in the sodium battery shell, the total volume of the inert gas accounts for 15%-50%. According to the sodium battery, after the electrolyte is injected for the first time and before the sodium battery is formed, the inert gas is introduced into the sodium battery shell, and the sodium battery is formed under the atmosphere of the inert gas in the sodium battery shell, so that the first coulombic efficiency of the sodium battery can be improved.

Description

Technical Field

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

[0002] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the widespread use of secondary 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 the low initial coulombic efficiency of sodium batteries limits their further application. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a sodium battery having a high first coulombic efficiency.

[0005] A first aspect of the present application provides a sodium battery, wherein the total volume of the inert gas accounts for 15%-50% based on the total volume of the gas in the sodium battery housing.

[0006] In any embodiment, based on the total volume of the gas in the sodium battery housing, the total volume of the inert gas accounts for 30%-45%.

[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 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, and the positive electrode active material includes a polyanion 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 ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

[0011] In any embodiment, the sodium battery includes anode-less sodium batteries and sodium metal batteries.

[0012] A second aspect of the present application provides a sodium battery formation method, comprising the following steps: injecting an electrolyte into a sodium battery shell; introducing an inert gas into the sodium battery shell; 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 shell is not included.

[0013] Studies have shown that during the first charge, i.e., formation, of a sodium battery, the active sodium released from the positive electrode active material is easily combined with reactive gases such as oxygen and carbon dioxide attached to the surface of the positive electrode active material, resulting in a partial loss of the released active sodium, which reduces the battery's first discharge capacity and thus deteriorates the first coulombic efficiency of the sodium battery. The formation method of a sodium battery of the present application introduces an inert gas into the battery housing after the electrolyte is injected and before the sodium battery is formed, so that the formation of the sodium battery is carried out in an atmosphere in which the gas in the battery housing includes an inert gas. The inert gas in the housing can dilute the concentration of the reactive gas adsorbed on the surface of the positive electrode active material, inhibit the active sodium released during the formation process from combining with the reactive gas, reduce the loss of active sodium, and thus improve the first 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 25KPa-100KPa.

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

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

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

[0019] In any embodiment, the inert gas is introduced for 1 to 6 hours after the electrolyte is injected.

[0020] After injecting electrolyte into the sodium battery shell, the positive active material of the sodium battery will be soaked by the electrolyte. With the electrolyte as the medium, oxygen adsorbed on the surface of the positive active material easily oxidizes the positive active material, causing the positive active material to transform into a desodiumed state, resulting in irreversible loss of active sodium that can contribute to capacity. As a result, the total amount of active sodium that can be released from the positive active material during the formation process of the sodium battery is reduced, resulting in a decrease in the initial charge capacity of the sodium battery, thereby deteriorating the initial coulombic efficiency of the sodium battery. Passing inert gas 1 to 6 hours after the electrolyte injection is completed can not only allow some of the gas adsorbed on the surface of the positive active material after the electrolyte injection to be discharged naturally, but also reduce the reaction between the positive active material and oxygen adsorbed on the surface of the positive active material under the condition of electrolyte as the medium, thereby reducing the loss of active sodium and improving 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 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 including a positive electrode active material, and the positive electrode active material including a polyanion 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 ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

[0024] After injecting electrolyte into the sodium battery casing, the above-mentioned positive electrode active material is easily oxidized to a desodiumed state by oxygen under the action of the electrolyte as a medium, resulting in irreversible loss of active sodium. Moreover, during the initial charging process, the active sodium released from the positive electrode active material easily combines with reactive gases, further irreversibly losing active sodium, thereby deteriorating the initial coulombic efficiency of the sodium battery. After the initial injection, an inert gas is introduced into the battery casing. The inert gas in 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 active sodium loss, which is beneficial to improving the initial coulombic efficiency of the sodium battery.

[0025] In any embodiment, the sodium battery includes anode-less sodium batteries and sodium metal batteries.

[0026] After the initial charge of anode-free sodium batteries and sodium metal batteries, the active sodium ions released from the positive electrode active material are reduced and deposited as a sodium metal layer on the negative electrode. The highly reducing sodium metal easily reacts with the oxygen in the sodium battery casing, causing irreversible loss of active sodium and severely degrading the battery's initial coulombic efficiency. After the electrolyte is injected, an inert gas is introduced into the battery casing, allowing the sodium battery formation to proceed in an atmosphere containing an inert gas. This can significantly improve the initial coulombic efficiency of anode-free sodium batteries and sodium metal batteries.

[0027] The third aspect of the present application further provides an electrical device, comprising the sodium battery of the first aspect or the sodium battery prepared by the formation method of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0033] Figure 6 Schematic diagram of an electrical device using a sodium battery according to one embodiment of the present application as a power source.

[0034] Description of reference numerals:

[0035] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Sodium battery; 5. Casing; 5. Electrode assembly; 5. Cover. DETAILED DESCRIPTION

[0036] Below, embodiments of the sodium battery, sodium battery formation method, and electrical device disclosed herein are described in detail, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to facilitate a thorough understanding of the present application by those skilled in the art and are not intended to limit the subject matter recited in the claims.

[0037] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0040] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

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

[0042] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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 the advantages of low cost, abundant resources, and good safety. However, they exhibit low coulombic efficiency during the initial charge and discharge cycle, which hinders their further application. The formation process is a key step in the manufacturing process of sodium batteries. During the formation process, gases such as oxygen and carbon dioxide present within the battery shell can cause irreversible loss of active sodium provided by the positive electrode active material, deteriorating the initial coulombic efficiency of the sodium battery.

[0044] [Sodium battery formation method]

[0045] Based on this, the present application proposes a sodium battery formation method, comprising the following steps: injecting an electrolyte into a sodium battery shell; introducing an inert gas into the sodium battery shell; 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 shell is not included.

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

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

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

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

[0050] In this article, the term "vacuuming" refers to extracting gas from a container or system to reduce the gas pressure in the container or system to a certain range, thereby achieving a vacuum state.

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

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

[0053] Studies have shown that during the first charge, i.e., formation, of a sodium battery, the active sodium released from the positive electrode active material is easily combined with reactive gases such as oxygen and carbon dioxide attached to the surface of the positive electrode active material, resulting in a partial loss of the released active sodium, which reduces the battery's first discharge capacity and thus deteriorates the first coulombic efficiency of the sodium battery. The formation method of a sodium battery of the present application introduces an inert gas into the battery housing after the electrolyte is injected and before the sodium battery is formed, so that the formation of the sodium battery is carried out in an atmosphere in which the gas in the battery housing includes an inert gas. The inert gas in the housing can dilute the concentration of the reactive gas adsorbed on the surface of the positive electrode active material, inhibit the active sodium released during the formation process from combining with the reactive gas, reduce the loss of active sodium, and thus improve the first coulombic efficiency of the sodium battery.

[0054] In some embodiments, injecting the electrolyte into the sodium battery housing includes: evacuating the sodium battery housing to a pressure of -5 KPa to 30 KPa, and injecting the electrolyte into the sodium battery housing.

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

[0056] In some embodiments, the pressure of the inert gas introduced is 25 KPa-100 KPa.

[0057] In some embodiments, the pressure of the inert gas introduced is 25 KPa, 40 KPa, 55 KPa, 70 KPa, 85 KPa, 100 KPa or any value therebetween.

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

[0059] In some embodiments, the inert gas is introduced for a time period of 2 seconds to 15 seconds.

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

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

[0062] In some embodiments, the inert gas is introduced 1 to 6 hours after the electrolyte is injected.

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

[0064] After injecting electrolyte into the sodium battery shell, the positive active material of the sodium battery will be soaked by the electrolyte. With the electrolyte as the medium, oxygen adsorbed on the surface of the positive active material easily oxidizes the positive active material, causing the positive active material to transform into a desodiumed state, resulting in irreversible loss of active sodium that can contribute to capacity. As a result, the total amount of active sodium that can be released from the positive active material during the formation process of the sodium battery is reduced, resulting in a decrease in the initial charge capacity of the sodium battery, thereby deteriorating the initial coulombic efficiency of the sodium battery. Passing inert gas 1 to 6 hours after the electrolyte injection is completed can not only allow some of the gas adsorbed on the surface of the positive active material after the electrolyte injection to be discharged naturally, but also reduce the reaction between the positive active material and oxygen adsorbed on the surface of the positive active material under the condition of electrolyte as the medium, thereby reducing the loss of active sodium and improving the initial coulombic efficiency of the sodium battery.

[0065] In some embodiments, the sodium battery formation method further comprises: standing for 6 to 36 hours.

[0066] In some embodiments, the formation method of a sodium battery comprises the following steps: injecting an electrolyte into a sodium battery shell; standing for 6 to 36 hours; introducing an inert gas into the sodium battery shell; 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 shell is not included.

[0067] In some embodiments, a sodium battery formation method comprises the following steps: injecting an electrolyte into a sodium battery shell; introducing an inert gas into the sodium battery shell; standing 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 shell 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 soak the positive electrode plate, the negative electrode plate, and the separator. Before the injection of the electrolyte is completed and before the long-term standing begins, an inert gas is introduced into the sodium battery housing, which can avoid the reaction between the positive electrode active material and the oxygen adsorbed on the surface of the positive electrode active material under the condition that the electrolyte is used as a medium due to 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, which includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0070] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for use in batteries. As an example, the positive electrode active material may 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 may also be used. These positive electrode active materials may 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.

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

[0072] As used herein, the term "polyanionic compound" refers to a general term for a series of compounds having a three-dimensional network structure formed by tetrahedral and polyhedral anionic structural units connected by strong covalent bonds.

[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 above-mentioned positive electrode active materials are easily oxidized to a desodiumized state by oxygen in the presence of the electrolyte, resulting in irreversible loss of active sodium. Furthermore, during the initial charge process, the active sodium released from the positive electrode active materials easily combines with reactive gases, further irreversibly losing active sodium, thereby deteriorating the initial coulombic efficiency of the sodium battery. After the initial injection, an inert gas is introduced into the battery casing. The inert gas in the casing can dilute the concentration of reactive gases adsorbed on the surface of the positive electrode active materials and inhibit the chemical reactions that lead to active sodium loss, thereby improving the initial coulombic efficiency of the sodium battery.

[0078] In some embodiments, sodium batteries include anode-less sodium batteries and sodium metal batteries.

[0079] In this article, the term "anode-free sodium battery" refers to a battery in which no negative electrode active material layer is actively applied to the negative electrode during the battery manufacturing process. For example, a sodium metal or carbonaceous active material layer is not applied to the negative electrode via a coating or deposition process to form a negative electrode active material layer. During the initial charge, sodium ions at the anode gain electrons, and metallic sodium is deposited on the current collector surface to form a sodium metal phase. During discharge, the metallic sodium is converted into sodium ions and returned to the positive electrode, completing the charge and discharge cycle.

[0080] As used herein, the term "sodium metal battery" refers to a secondary battery prepared by pre-depositing sodium metal or its alloy on the negative electrode during the battery manufacturing process.

[0081] After the initial charge of anode-free sodium batteries and sodium metal batteries, the active sodium ions released from the positive electrode active material are reduced and deposited as a sodium metal layer on the negative electrode. The highly reducing sodium metal easily reacts with the oxygen in the sodium battery casing, causing irreversible loss of active sodium and severely degrading the battery's initial coulombic efficiency. After the electrolyte is injected, an inert gas is introduced into the battery casing, allowing the sodium battery formation to proceed in an atmosphere containing an inert gas. This can significantly improve the initial coulombic efficiency of anode-free sodium batteries and sodium metal batteries.

[0082] [Sodium battery]

[0083] The present application also provides a sodium battery, wherein the total volume of the inert gas in the sodium battery shell accounts for 15%-50% based on the total volume of the gas in the sodium battery shell.

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

[0085] In the present application, the total volume proportion of inert gas in the sodium battery shell can be tested by methods known in the art, such as gas composition analysis-gas chromatography, and the detection basis is GB / T 9722-2006. Test principle: After the sample and its measured components are vaporized, they enter the chromatographic column simultaneously with the carrier gas (usually oxygen). The differences in the physicochemical properties of the measured components such as adsorption or dissolution, desorption or analysis between the gas-solid or gas-liquid phases are used to form differences in the migration speed of the components in the column and separate them. The separated components flow out of the chromatographic column one after another and enter the detector, and the chromatographic column and corresponding data are recorded by the data processing system. The retention value of each component and the chromatographic peak area or the corresponding peak height value are used as the basis for qualitative or quantitative analysis. Operation method: Sampling volume: 1 mL; split ratio: 5:1, using TCD (thermal conductivity detector), after balancing the instrument, use a gas injection needle to extract a certain amount of gas in the sodium battery shell, inject gas from the injection port, perform GC-TCD analysis, obtain the volume proportion of each inert gas, and calculate the total volume proportion of inert gas based on the total volume of gas in the sodium battery shell.

[0086] In some embodiments, the total volume of the inert gas in the sodium battery housing is 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value therebetween, based on the total volume of the gas in the sodium battery housing.

[0087] In any embodiment, based on the total volume of the gas in the sodium battery housing, the total volume of the inert gas accounts for 30%-45%.

[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 provided on at least one side of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0089] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. As an example, the positive electrode active material may 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, 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, sodium vanadium phosphate, and sodium iron pyrophosphate.

[0093] In some embodiments, sodium batteries include anode-less sodium batteries and sodium metal batteries.

[0094] [Positive electrode]

[0095] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

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

[0097] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

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

[0099] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, 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.

[0100] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0101] [Negative electrode]

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

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

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

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

[0106] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer can be provided 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material 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 for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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 further include a binder. For 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 layer may further include a conductive agent. For 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 layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0112] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0113] [Electrolytes]

[0114] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0115] In some embodiments, the electrolyte is an electrolyte solution comprising 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 is represented by C b F 2b+1 , b is an integer between 1 and 10, and can be optionally 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, and the solvent includes at least one of a chain carbonate, a chain carboxylate, a cyclic carbonic acid, an ether solvent, a sulfone solvent, and a nitrile solvent. In some embodiments, the chain carbonate includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl 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 of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC). In some embodiments, the chain carboxylate includes at least one of 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 linear carboxylic acid ester includes at least one of 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 of 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 further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0120] [Isolation film]

[0121] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and 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, non-woven 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 embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0124] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0126] In this application, the shape of the sodium battery is not limited to cylindrical, square or other arbitrary shapes. For example, Figure 1 A sodium battery 5 having a square structure is used as an example.

[0127] In some embodiments, reference Figure 2 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the sodium battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

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

[0129] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the multiple sodium batteries 5 can be arranged in sequence along the length of the battery module 4. Of course, they can also be arranged in any other manner. The multiple sodium batteries 5 can further be fixed by fasteners.

[0130] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of sodium batteries 5 are accommodated in the accommodation space.

[0131] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0132] Figure 4 and Figure 5The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0133] In addition, the present application also provides an electrical device, which includes at least one of the sodium battery, battery module, or battery pack provided in the present application. The sodium battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0134] As an electrical device, a sodium battery, battery module or battery pack can be selected according to its usage requirements.

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

[0136] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a sodium battery as a power source.

[0137] Example

[0138] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0139] 1. Preparation method

[0140] Example 1:

[0141] 1) Preparation of negative electrode sheet

[0142] Weigh 5g of sodium carboxymethylcellulose (CMC-Na) and dissolve it in 1000mL of water with stirring. Then, add 5g of single-walled carbon nanotubes and disperse them ultrasonically to prepare a slurry. This slurry is coated on the surface of the negative electrode current collector copper foil. After drying, slitting, and cutting, the negative electrode sheet is obtained.

[0143] 2) Preparation of positive electrode sheet

[0144] The positive electrode active material sodium ferric pyrophosphate, the conductive agent carbon nanotubes, and the binder hexafluorophosphate are fully stirred and 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 is coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and die-cutting, a positive electrode sheet with a thickness of 200 μm is 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 in a mass ratio of 1:3, sodium hexafluorophosphate (NaPF6) was added, and after stirring evenly, an electrolyte with a NaPF6 concentration of 1 mol / L was obtained.

[0147] 4) Isolation film

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

[0149] 5) Preparation of sodium batteries

[0150] The positive electrode sheet, separator, and negative electrode sheet prepared in the above steps are stacked in order, so that the separator is located between the positive electrode sheet and the negative electrode sheet and can isolate the positive electrode sheet from the negative electrode sheet; and then the stacked components are wound to obtain an electrode assembly;

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

[0152] After formation, the battery was left to stand, shaped, and then tested for capacity. The battery was discharged at a constant current of 0.33C until the voltage reached 1.5V to obtain the initial discharge capacity. The battery was then welded to the housing using sealing nails and subjected to a final helium test to obtain the negative electrode-free sodium battery of Example 1.

[0153] Examples 2-4

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

[0155] Example 5

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

[0157] Example 6

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

[0159] Example 7

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

[0161] Example 8

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

[0163] Example 9

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

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

[0166] Example 10

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

[0168] The prepared electrolyte was injected into the sodium battery shell. 12 hours after the injection was completed, argon gas with a pressure of 50 KPa was introduced into the shell for 5 seconds. After standing for 12 hours, the sodium battery was formed in an atmosphere of inert gas in the shell.

[0169] Example 11

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

[0171] The negative electrode active material hard carbon, the conductive agent carbon black, and the binder sodium carboxymethyl cellulose are fully stirred and mixed in a deionized water solvent system in a mass ratio of 90:5:5 to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; the copper foil is dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet.

[0172] Comparative Example 1

[0173] The sodium battery preparation method of Comparative Example 1 is basically the same as the preparation method of Example 1, except that, after the electrolyte is injected and before the sodium battery is formed, an inert gas is not introduced into the sodium battery housing. Specific parameters are shown in Table 1.

[0174] Comparative Example 2

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

[0176] Comparative Example 3

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

[0178] 2. Battery performance test

[0179] 1. First Coulomb efficiency test

[0180] During the preparation process of the sodium batteries of Examples 1-11 and Comparative Examples 1-3, the first coulombic efficiency test was carried out, wherein the charging capacity at the end of formation was taken as the first charging capacity C1, and the discharge capacity during the capacity test was taken as the first discharge capacity C2. The first coulombic efficiency of the battery = C2 / C1×100%.

[0181] 3. Analysis of test results of various embodiments and comparative examples

[0182] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Tables 1 and 2.

[0183] Table 1

[0184]

[0185] Table 2

[0186]

[0187] As can be seen from Examples 1-11, after injecting the electrolyte into the sodium battery, an inert gas is introduced into the sodium battery housing, and the sodium battery is formed in an atmosphere in which the gas in the sodium battery housing includes the inert gas. The sodium battery has an excellent first coulombic efficiency.

[0188] From the comparison of Examples 1-10 with Comparative Examples 1-2, Example 11 and Comparative Example 3, it can be seen that after the sodium battery is injected with the electrolyte, an inert gas is introduced into the sodium battery housing, and the sodium battery is formed in an atmosphere in which the gas in the sodium battery housing includes an inert gas, which is beneficial to improving the initial efficiency of the sodium battery.

[0189] It can be seen from Examples 1-4 that when the gas in the sodium battery shell includes an inert gas atmosphere, the sodium battery is formed, and the inert gas includes one or more of argon, helium, and nitrogen, the sodium battery has an excellent first effect.

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

[0191] It can be seen from Examples 1, 7, and 8 that when the time for introducing the inert gas into the sodium battery housing is 2s-15s, the sodium battery has an excellent first efficiency.

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

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

[0194] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A sodium battery, characterized in that: Based on the total volume of the gas in the sodium battery shell, the total volume of the inert gas accounts for 15%-50%.

2. The sodium battery according to claim 1, characterized in that Based on the total volume of gas in the sodium battery shell, the total volume of inert gas accounts for 30%-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 any one of claims 1 to 3, characterized in that The sodium battery includes a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a polyanion compound.

5. The sodium battery according to claim 4, characterized in that The polyanion compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanion 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 polyanion compound includes at least one of sodium ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

7. The sodium battery according to any one of claims 1 to 6, characterized in that The sodium battery includes a negative electrode-free sodium battery and a sodium metal battery.

8. A sodium battery formation method, characterized in that: The following steps are involved: injecting electrolyte into the sodium battery shell; introducing an inert gas into the sodium battery housing; Perform formation on sodium batteries; Wherein, after the completion of introducing the inert gas and before the start of forming the sodium battery, the step of evacuating the sodium battery shell is not included.

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

10. The chemical formation method according to claim 8 or 9, characterized in that: The inert gas pressure of the inert gas introduced is 25KPa-100KPa; and / or, The inert gas is introduced for a time of 2s-15s.

11. The chemical formation method according to any one of claims 8 to 10, characterized in that: Inert gas is introduced 1 to 6 hours after the electrolyte injection is completed.

12. The chemical formation method according to any one of claims 8 to 11, characterized in that The sodium battery includes a positive electrode plate, which includes a positive electrode collector and a positive electrode film layer disposed on at least one side of the positive electrode collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a polyanion compound.

13. The chemical formation method according to claim 12, characterized in that: The polyanion compound includes one or more of Na3M2(PO4)3, Na2XP2O7, phosphate and pyrophosphate mixed polyanion 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.

14. The chemical formation method according to claim 12 or 13, characterized in that: The polyanion compound includes at least one of sodium ferric pyrophosphate, sodium vanadium phosphate, and sodium ferric pyrophosphate.

15. The chemical formation method according to any one of claims 8 to 14, characterized in that The sodium battery includes a negative electrode-free sodium battery and a sodium metal battery.

16. An electrical device, characterized in that: A sodium battery comprising the sodium battery according to any one of claims 1 to 7 or a sodium battery prepared by the formation method of the sodium battery according to any one of claims 8 to 15.

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