Positive active material, positive electrode sheet, battery cell, sodium metal battery and electric device of sodium metal battery

Abstract

The application provides a positive electrode active material of a sodium metal battery, a positive electrode sheet, a battery monomer, a sodium metal battery and an electric device, the positive electrode active material comprising a sodium transition metal oxide and a polyanion compound; wherein the specific surface area of the sodium transition metal oxide satisfies: 0.4m 2 / g≤BET1≤4m 2 / g, and the specific surface area of the polyanion compound satisfies: 10m 2 / g≤BET2≤20m 2 / g. The positive electrode active material helps to realize a high-power sodium metal battery while improving the energy density of the sodium metal battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, and more particularly, to a positive electrode active material of a sodium metal battery, a positive electrode sheet, a battery monomer, a sodium metal battery and an electric device. BACKGROUND

[0002] In recent years, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc., thereby obtaining great development.

[0003] The sodium metal battery is a secondary battery that directly uses metal sodium as a negative electrode active material. Due to the abundant reserves of sodium element on the earth, the sodium metal battery has become a highly potential energy storage device. Therefore, how to improve the energy density of the sodium metal battery has become a technical problem to be solved. SUMMARY

[0004] The present application is made in view of the above technical problem, and aims to provide a positive electrode active material of a sodium metal battery, a positive electrode sheet, a battery monomer, a sodium metal battery and an electric device, which can improve the energy density of the sodium metal battery when applied to the sodium metal battery.

[0005] In a first aspect, a positive electrode active material of a sodium metal battery is provided, comprising: a sodium transition metal oxide and a polyanion compound; wherein the specific surface area of the sodium transition metal oxide satisfies: 0.4 m 2 / g≤BET1≤4.0 m 2 / g, and the specific surface area of the polyanion compound satisfies: 10 m 2 / g≤BET2≤20 m 2 / g.

[0006] In the embodiments of the present application, the positive electrode active material comprises a sodium transition metal oxide and a polyanion compound, wherein the sodium transition metal oxide has a higher capacity and the polyanion compound has better power performance. By compounding the sodium transition metal oxide in the polyanion compound, the sodium metal battery has a higher capacity and a higher power. By controlling the specific surface areas of the two materials within a suitable range, the powder compaction density of the compounded positive electrode active material can be improved, thereby improving the energy density of the sodium metal battery while also helping to improve the capacity and power performance of the sodium metal battery.

[0007] In some embodiments, the powder compaction density of the positive electrode active material under a pressure of 29400 N satisfies: 1.8 g / cm 3 ≤p≤2.8 g / cm 3 .

[0008] In some embodiments, a ratio of a mass m1 of the sodium transition metal oxide to a mass m2 of the polyanionic compound in the positive electrode active material satisfies: 1 / 9≤m1 / m2≤1.

[0009] In some embodiments, a ratio of the mass m1 of the sodium transition metal oxide to a mass m of the positive electrode active material satisfies: 0.1≤m1 / m≤0.5.

[0010] In some embodiments, a ratio of the mass m2 of the polyanionic compound to the mass m of the positive electrode active material satisfies: 0.5≤m2 / m≤0.9, and 0<(m1+m2) / m≤1.

[0011] In some embodiments, the anion in the polyanionic compound comprises at least one of a phosphate, a pyrophosphate, a fluoropyrophosphate, a sulfate.

[0012] In some embodiments, the polyanionic compound comprises Na x M1 y P m O n ; wherein M1 represents a metal element, the metal element comprises at least one of Mn, Fe, Co, Cu, Al, Ti, V, 1≤x≤2, 0

[0013] In some embodiments, the sodium transition metal oxide comprises Na a M2 b O c ; wherein M2 represents a transition metal element, 0.3≤a≤1.2, 0

[0014] In some embodiments, the transition metal element comprises at least one of Ni, Mn, Fe, Co, Cu, Ti, Cr, V, Zn.

[0015] In a second aspect, a positive electrode tab of a sodium metal battery is provided, the positive electrode tab comprising the positive electrode active material according to any one of the first aspect.

[0016] In a third aspect, a battery cell of a sodium metal battery is provided, the battery cell comprising the positive electrode tab according to any one of the second aspect.

[0017] In a fourth aspect, a sodium metal battery is provided, the sodium metal battery comprising the battery cell according to any one of the third aspect.

[0018] In a fifth aspect, there is provided a power consuming device comprising the battery cell of any one of the third aspect, and / or the sodium metal battery of any one of the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0020] Figure 1 A schematic diagram of a battery cell of a sodium metal battery according to an embodiment of the present application.

[0021] Figure 2 A schematic diagram of a battery module of a sodium metal battery according to an embodiment of the present application.

[0022] Figure 3 A schematic diagram of a sodium metal battery according to an embodiment of the present application.

[0023] Figure 4 Another schematic diagram of a sodium metal battery according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] Hereinafter, specific embodiments of the positive electrode active material, the positive electrode sheet, the battery cell, the sodium metal battery and the power consuming device of the present application will be specifically described with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0025] "ranges" disclosed herein are defined by both a lower and an upper limit, and the particular range is defined by selecting a lower limit and an upper limit that defines the boundaries of the range. Ranges defined by the endpoints can or can not include the endpoints, and ranges can be combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any combination of the numbers a and b, in which a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand for listing all of those numbers. Also, when a parameter is stated to be an integer > 2, it is equivalent to state that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] In the description of the present application, it is necessary to explain that, unless otherwise specified, the meaning of "a plurality of" is more than two; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like is merely for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0027] If not specifically stated, "including" and "comprising" mentioned in the present application means open-ended, and can also be closed-ended. For example, "including" and "comprising" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0028] If not specifically stated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or A and B are both true (or present).

[0029] If not otherwise specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0030] If not otherwise specified, all embodiments of the present application and optional embodiments can be combined to form new technical solutions.

[0031] If not otherwise specified, all technical features of the present application and optional technical features can be combined to form new technical solutions.

[0032] If not otherwise specified, the following terms have the following meanings. Any undefined terms have their art-recognized meanings.

[0033] “Sodium metal battery” refers to a sodium ion battery with a metal sodium as the negative active material.

[0034] “Sodium transition metal oxide” refers to a compound composed of sodium and an oxide containing transition metal elements, for example, one or more of Fe, Co, Ni, Cu, Zn, V, Cr, Mn. Structurally, the sodium transition metal oxide can have a layered structure, a tunnel structure, etc.

[0035] “Polyanionic compound” refers to a series of compounds containing tetrahedral or octahedral anion units. According to the type of anion, it can be divided into a variety of different systems. For example, phosphate system, pyrophosphate system, fluoropyrophosphate system, sulfate system, mixed anion system, etc.

[0036] In one example, the polyanionic compound can be a compound having sodium ions, transition metal ions, and tetrahedral anion units (YO4) d- The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y can be one or more of P, S, and Si, and d represents the valence of (YO4) d- .

[0037] In one example, the polyanionic compound can be a compound having sodium ions, transition metal ions, tetrahedral anion units (YO4) d-and halide anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y can be one or more of P, S, and Si, d represents the valence of (YO4) d- , and halide can be one or more of F, Cl, and Br.

[0038] In another example, the polyanionic compound can also be a compound having sodium ions, tetrahedral anionic units (YO4) d- , polyhedral units (ZO f ) g+ , and optional halide anions. Y can be one or more of P, S, and Si, d represents the valence of (YO4) d- , Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, g represents the valence of (ZO f ) g+ , and halide can be one or more of F, Cl, and Br.

[0039] Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge of the battery cell, active ions are reversibly intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet and functions to prevent short circuiting between the positive and negative electrodes, while allowing the active ions to pass through. In some embodiments, the battery cell described above is also referred to as a secondary battery.

[0040] Similar to lithium-ion batteries, sodium-ion batteries rely on the electrochemical reactions of sodium ions deintercalating and intercalating between the positive and negative electrodes to achieve charge and discharge. During the charging of a sodium-ion battery, sodium ions deintercalate from the positive active material, move and intercalate into the negative active material, while electrons flow from the positive electrode to the negative electrode through an external circuit; and during the discharging, sodium ions deintercalate from the negative active material, move and intercalate into the positive active material, while electrons flow from the negative electrode to the positive electrode through an external circuit.

[0041] It should be understood that the "intercalation" process described herein refers to the process of sodium ions intercalating into the positive active material and the negative active material due to electrochemical reactions, and the "deintercalation" process described herein refers to the process of sodium ions deintercalating from the positive active material and the negative active material due to electrochemical reactions.

[0042] Sodium metal battery is a special kind of sodium ion battery, in which sodium metal is directly used as the negative active material. In traditional sodium ion battery, hard carbon is usually used as the negative active material, which has a low theoretical capacity. Sodium metal has a theoretical capacity of 1166 mAh / g, which enables the battery system with sodium metal as the negative electrode to have a higher energy density. In addition, compared with ordinary sodium ion battery, sodium metal battery has higher voltage, longer cycle life and higher charge and discharge rate, so sodium metal battery becomes a new generation of secondary battery with great development potential.

[0043] Currently, the research on sodium metal battery focuses on the negative active material and the electrolyte, and the positive active material is usually directly borrowed from the positive active material of sodium ion battery. In fact, due to the high theoretical capacity of sodium metal, the positive active material in sodium ion battery usually cannot provide corresponding energy density, which limits the capacity of sodium metal battery and affects the development of sodium metal battery.

[0044] Therefore, the present application provides a positive active material for sodium metal battery, which can contribute to a higher energy density for sodium metal battery, and help to improve the capacity and power performance of sodium metal battery.

[0045] Next, the electrode material, the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte in the sodium metal battery are introduced in detail.

[0046] [Positive electrode sheet]

[0047] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive active material.

[0048] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer can be disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0049] Optionally, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0050] The embodiment of the present application first provides a positive active material for sodium metal battery, which includes sodium transition metal oxide and polyanion compound, wherein the specific surface area of the sodium transition metal oxide satisfies: 0.4 m2 / g ≤ BET1 ≤ 4.0 m 2 / g, the specific surface area of the polyanionic compound satisfies: 10 m 2 / g ≤ BET2 ≤ 20 m 2 / g.

[0051] Specifically, BET1 can be 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.2 m 2 / g, 1.4 m 2 / g, 1.6 m 2 / g, 1.8 m 2 / g, 2.0 m 2 / g, 2.2 m 2 / g, 2.4 m 2 / g, 2.6 m 2 / g, 2.8 m 2 / g, 3.0 m 2 / g, 3.2 m 2 / g, 3.4 m 2 / g, 3.6 m 2 / g, 3.8 m 2 / g, 4.0 m 2 / g or a range of values obtained by any two numerical combinations above. BET2 can be 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g, 19 m 2 / g, 20 m 2 / g, or a range of values obtained by any two numerical combinations above.

[0052] Generally speaking, sodium transition metal oxides have higher capacity, but when used alone as the positive active material, their structural stability is poor, which is not conducive to the long cycle of the battery. Polyanionic compounds have stable structure and high working voltage, and can provide high power for the battery, but when used alone as the positive active material, their capacity is very limited, which cannot meet the energy density requirement of the sodium metal battery. In the embodiment, by compounding sodium transition metal oxides in polyanionic compounds as the positive active material, the sodium metal battery can have both high capacity and high power. Moreover, by controlling the specific surface area of the two different materials within the above numerical range, the powder compaction density of the compounded material can be improved, so that the sodium metal battery with high capacity and high power can be realized, and the energy density of the sodium metal battery is improved.

[0053] Optionally, the powder compaction density of the positive active material under a pressure of 29400 N satisfies: 1.8 g / cm 3 ≤ p ≤ 2.8 g / cm 3 .

[0054] Specifically, the powder compaction density p of the positive active material under a pressure of 29400 N can be 1.8 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 , 2.1 g / cm 3 , 2.2 g / cm 3 , 2.3 g / cm 3 , 2.4 g / cm 3 , 2.5 g / cm 3 , 2.6 g / cm 3 , 2.7 g / cm 3 , 2.8 g / cm 3 , or a numerical range within the range obtained by any two of the above numerical combinations.

[0055] Optionally, in the positive active material, the ratio of the mass m1 of the sodium transition metal oxide to the mass m2 of the polyanionic compound satisfies: 1 / 9 ≤ m1 / m2 ≤ 1.

[0056] Specifically, m1 / m2 can be 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, 1 / 4, 1 / 3, 1 / 2, 1, or a numerical range within the range obtained by any two of the above numerical combinations.

[0057] Optionally, the ratio of the mass m1 of the sodium transition metal oxide to the mass m of the positive active material satisfies: 0.1 ≤ m1 / m ≤ 0.5.

[0058] Specifically, m1 / m can be 0.1, 0.2, 0.3, 0.4, 0.5, or a value range thereof within a range obtained by any two numerical combinations.

[0059] Optionally, a ratio of a mass m2 of the polyanionic compound to a mass m of the positive electrode active material satisfies: 0.5≤m2 / m≤0.9, and 0<(m1+m2) / m≤1.

[0060] Specifically, m2 / m can be 0.5, 0.6, 0.7, 0.8, 0.9, or a value range thereof within a range obtained by any two numerical combinations.

[0061] Optionally, the anion in the polyanionic compound includes at least one of a phosphate, a pyrophosphate, a fluoro-pyrophosphate, a sulfate.

[0062] Optionally, the polyanionic compound includes Na x M1 y P m O n ; wherein M1 represents a metal element, the metal element includes at least one of Mn, Fe, Co, Cu, Al, Ti, V, 1≤x≤2, 0

[0063] Optionally, the sodium transition metal oxide includes Na a M2 b O c ; wherein M2 represents a transition metal element, 0.3≤a≤1.2, 0≤b≤1, 2≤c≤2.1.

[0064] Optionally, the transition metal element includes at least one of Ni, Mn, Fe, Co, Cu, Ti, Cr, V, Zn.

[0065] Optionally, the positive electrode film layer further optionally includes a binder. As an example, the binder can 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.

[0066] Optionally, the positive electrode film layer includes a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., NMP) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and subjecting the positive electrode current collector to drying, cold pressing, or the like to obtain the positive electrode sheet.

[0068] [Anode sheet]

[0069] The anode sheet generally includes an anode current collector, or includes an anode current collector and an anode film layer disposed on at least one surface of the anode current collector, the anode film layer including an anode active material.

[0070] In some embodiments, the anode sheet of the sodium metal battery is an anode current collector, i.e., the anode current collector directly serves as the anode sheet, and this type of sodium metal battery can also be referred to as a "anode-free battery". During the charging process, sodium ions are deposited on the anode current collector to form a sodium metal anode, and the sodium metal in the sodium metal anode is the anode active material. In other embodiments, in order to ensure the normal use of the anode sheet or facilitate the deposition of sodium metal on the anode current collector, a conductive film layer can be disposed on the anode current collector.

[0071] As an example, the anode current collector has two opposite surfaces in the thickness direction of the anode current collector, and the anode film layer can be disposed on any one or both of the two opposite surfaces of the anode current collector.

[0072] Optionally, the anode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0073] Optionally, the anode active material can use an anode active material known in the art for a sodium metal battery. As an example, the anode active material can include at least one of the following materials: sodium metal, a carbon-based material or a metal on which sodium metal is deposited, an alloy material, a composite material containing sodium metal, an alloy material containing sodium metal, etc. However, the present application is not limited to these materials, and other materials that can be used as anode active materials for sodium metal batteries can also be used. These anode active materials can be used alone or in combination with two or more materials.

[0074] The above negative electrode sheet can be prepared according to a conventional method in the art. For example, a copper foil or a copper foil provided with a conductive film layer on at least one surface of the copper foil can be used as the negative electrode sheet. The conductive film layer can be provided on at least one surface of the negative current collector by a method such as physical vapor deposition (PVD), spin coating, electroplating, chemical vapor deposition (CVD), or the like.

[0075] [Electrolyte]

[0076] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application, and can be selected as needed. For example, the electrolyte can be in a liquid state, a gel state, or a solid state.

[0077] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0078] Optionally, the electrolyte salt includes NaPF6, NaBCl4, NaSO3CF3, Na(CH3)C6H4SO3, and the like.

[0079] Optionally, the solvent includes a carbonate or an ether solvent. The carbonate solvent includes cyclic carbonate solvents such as ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), and chain carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and the like; and the ether solvent includes ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 1,3-dioxolane, and the like.

[0080] Optionally, the electrolyte solution can further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, and the like.

[0081] [Separator]

[0082] In some embodiments, the sodium metal battery further includes a separator. The type of the separator is not particularly limited in the present application, and for example, the separator can be a separator film. The separator film can be any known porous structure separator film having good chemical stability and mechanical stability.

[0083] Optionally, the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the isolation film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0084] The embodiments of the present application also provide a sodium metal battery cell, which includes the positive electrode sheet according to any of the embodiments of the present application.

[0085] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the isolation film described above can be used to make an electrode assembly through a winding process or a stacking process.

[0086] In some embodiments, the battery cell can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above.

[0087] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0088] The shape of the battery cell is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 1 is a battery cell 100 of a sodium metal battery as an example of a square structure.

[0089] Figure 2 is a battery module 200 of a sodium metal battery as an example. Referring to Figure 2 In the battery module 200, a plurality of battery cells 100 can be arranged sequentially along the length direction of the battery module 200. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 100 can be fixed by fasteners.

[0090] Optionally, in an embodiment, the battery module 200 can further include a housing having an accommodation space, and the plurality of battery cells 100 are accommodated in the accommodation space.

[0091] Optionally, in an embodiment, the battery module 200 described above can also be assembled into a sodium metal battery, and the number of battery modules 200 contained in the sodium metal battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0092] Figure 3 and Figure 4 is a sodium metal battery 300 as an example. Referring to Figure 3 and Figure 4In the sodium metal battery 300, a battery case and a plurality of battery modules 200 disposed in the battery case can be included. The battery case includes an upper case 301 and a lower case 302, and the upper case 301 can be disposed on the lower case 302 to form an enclosed space for accommodating the battery modules 200. The plurality of battery modules 200 can be arranged in the battery case in any manner.

[0093] It should be understood that in other embodiments, the above-mentioned sodium metal battery 300 is also referred to as a sodium metal battery pack. The battery cells 100 can be first assembled into the battery modules 200, and the sodium metal battery 300 is assembled from the battery modules 200. The sodium metal battery 300 can also be directly assembled from the battery cells 100, and the intermediate form of the battery module 200 is omitted.

[0094] In addition, the present application also provides a power utilization device, which includes at least one of the battery cell 100 of the sodium metal battery, the battery module 200 of the sodium metal battery, or the sodium metal battery 300 provided by the present application. The battery cell 100, the battery module 200, or the sodium metal battery 300 can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0095] As the power utilization device, the number of the battery cell 100, the battery module 200, or the sodium metal battery 300 can be selected according to the use requirements thereof.

[0096] As an example of the power utilization device. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the secondary battery for the power utilization device, the sodium metal battery 300 or the battery module 200 can be used.

[0097] As another example of the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the battery cell 100 can be used as a power supply.

[0098] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained by purchase.

[0099] [Examples 1-11 and Comparative Examples 1-3]

[0100] Example 1

[0101] (1) Preparation of the positive electrode tab

[0102] The poly-anionic compound NaFePO4, sodium transition metal oxide Na 0.95 Mn 0.33 Ni 0.33 Fe 0.33 O2, conductive carbon black (Super P), and binder PVDF were fully stirred in an appropriate amount of NMP in a mass ratio of 45:45:5:5 to form a positive electrode slurry. The positive electrode slurry was coated on a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode tab was obtained.

[0103] (2) Preparation of the negative electrode tab

[0104] Carbon nanotubes and sodium alginate were added to deionized water and stirred to form a uniform slurry. The slurry was coated on a copper foil, and after drying and cold pressing, a "negative electrode-free" negative electrode tab was obtained. The areal density of the coating was 20 g / m 2 .

[0105] Alternatively, further, the "negative electrode-free" tab after drying and cold pressing was cut, and the tab was assembled with a positive electrode tab and a separator to form a battery monomer. The assembled battery monomer was charged at 0.5C constant current to 3.8V, so as to pre-deposit sodium metal on the tab; after the battery monomer was fully charged, the fully charged tab was taken out in a glove box as a negative electrode tab.

[0106] (3) Assembly of the battery monomer

[0107] The above positive electrode tab, glass fiber film, and negative electrode tab were stacked in order, and after winding, an electrode assembly was formed. The electrode assembly was loaded into a packaging shell, 1M NaPF6 electrolyte was added, and after packaging, formation, and standing processes, a sodium metal battery was obtained. The solvent of the electrolyte was dimethyl ether (Methoxymethane, DME).

[0108] In Example 1, the positive electrode active material includes NaFePO4and Na 0.95 Mn 0.33 Ni 0.33 Fe 0.33 O2. The specific surface area BET1of Na 0.95 Mn 0.33 Ni 0.33 Fe 0.33 O2is 0.4 m 2 / g; the specific surface area BET2of NaFePO4is 10 m 2 / g; and the specific surface area BET3of Na 0.95 Mn0.33 Ni 0.33 Fe 0.33 The ratio of the mass m1 of O2 to the mass m2 of NaFePO4: m1 / m2 = 1 / 4; the ratio of the mass m1 of O2 to the mass m of the positive active material: m1 / m = 1 / 5; the ratio of the mass m2 of NaFePO4 to the mass m of the positive active material: m2 / m = 4 / 5; the powder compaction density p of the positive active material under a pressure of 29400 N = 2.2 g / cm3. 0.95 Mn 0.33 Ni 0.33 Fe 0.33 The ratio of the mass m1 of O2 to the mass m2 of NaFePO4: m1 / m2 = 1 / 4; the ratio of the mass m1 of O2 to the mass m of the positive active material: m1 / m = 1 / 5; the ratio of the mass m2 of NaFePO4 to the mass m of the positive active material: m2 / m = 4 / 5; the powder compaction density p of the positive active material under a pressure of 29400 N = 2.2 g / cm3. 3 .

[0109] Example 2

[0110] In the sodium metal battery of Example 2, compared with Example 1, BET1 = 4.0 m 2 / g, BET2 = 20 m 2 / g, p = 1.9 g / cm 3 .

[0111] Example 3

[0112] In the sodium metal battery of Example 3, compared with Example 1, BET1 = 0.8 m 2 / g, BET2 = 12 m 2 / g, m1 / m2 = 1, m1 / m = 1 / 2, m2 / m = 1 / 2, p = 2.5 g / cm 3 .

[0113] Example 4

[0114] In the sodium metal battery of Example 4, compared with Example 1, BET1 = 2 m 2 / g, BET2 = 10 m 2 / g, p = 2.1 g / cm 3 .

[0115] Example 5

[0116] In the sodium metal battery of Example 5, compared with Example 1, BET1 = 2 m 2 / g, BET2 = 20 m 2 / g, p = 1.9 g / cm 3 .

[0117] Example 6

[0118] In the sodium metal battery of Example 6, compared with Example 1, m1 / m2 = 1 / 9, m1 / m = 1 / 10, m2 / m = 9 / 10, p = 2.1 g / cm 3 .

[0119] Example 7

[0120] In the sodium metal battery of Example 7, m1 / m2 = 1, m1 / m = 1 / 2, m2 / m = 1 / 2, and p = 2.6 g / cm 3 .

[0121] Example 8

[0122] In the sodium metal battery of Example 8, the positive active material further comprises a Prussian blue compound Na2Fe[Fe(CN)6], wherein BET1 = 0.4 m 2 / g, BET2 = 10 m 2 / g, m1 / m2 = 1, m1 / m = 2 / 7, m2 / m = 2 / 7, the ratio of the mass m3 of Na2Fe[Fe(CN)6] to the mass m of the positive active material: m3 / m = 3 / 7, and p = 2.8 g / cm 3 .

[0123] Example 9

[0124] In the sodium metal battery of Example 9, p = 1.8 g / cm 3 .

[0125] Example 10

[0126] In the sodium metal battery of Example 10, p = 2.8 g / cm 3 .

[0127] Example 11

[0128] In the sodium metal battery of Example 11, the positive active material comprises a sodium transition metal oxide NaMn 0.4 Fe 0.2 Ni 0.4 O2and a polyanionic compound Na2FeP2O7. Wherein, the specific surface area BET1 of NaMn 0.4 Fe 0.2 Ni 0.4 O2is 0.4 m 2 / g; the specific surface area BET2 of Na2FeP2O7 is 10 m 2 / g; the ratio of the mass m1 of NaMn 0.4 Fe 0.2 Ni 0.4 O2to the mass m2 of Na2FeP2O7: m1 / m2 = 1 / 4; the ratio of the mass m1 of Na2FeP2O7 to the mass m of the positive active material: m1 / m = 1 / 5; the ratio of the mass m1 of NaMn 0.4 Fe0.2 Ni 0.4 The ratio of the mass m2 of O2 to the mass m of the positive active material: m2 / m = 4 / 5; the powder compaction density p of the positive active material under a pressure of 29400 N = 2.7 g / cm3. 3 .

[0129] Comparative Example 1

[0130] In the sodium metal battery of Comparative Example 1, the positive active material only includes NaFePO4, i.e. m1 / m = 1, p = 1.6 g / cm3, as compared with Example 1. 3 .

[0131] Comparative Example 2

[0132] As compared with Example 1, BET1 = 10 m2 / g, BET2 = 30 m2 / g, p = 1.4 g / cm3. 2 . 2 3 .

[0133] Comparative Example 3

[0134] As compared with Example 1, BET1 = 5 m2 / g, BET2 = 30 m2 / g, p = 1.6 g / cm3. 2 . 2 3 .

[0135] Product parameters of Examples and Comparative Examples in Table 1

[0136]

[0137]

[0138] In Table 1, BET1 represents the specific surface area of the sodium transition metal oxide in the positive active material, BET2 represents the specific surface area of the polyanionic compound in the positive active material, m1 / m2 represents the ratio of the mass m1 of the sodium transition metal oxide to the mass m2 of the polyanionic compound in the positive active material, m1 / m represents the ratio of the mass m1 of the sodium transition metal oxide to the mass m of the positive active material, m2 / m represents the ratio of the mass m2 of the polyanionic compound to the mass m of the positive active material, and p represents the powder compaction density of the positive active material under a pressure of 29400 N.

[0139] The performance test results of the sodium metal batteries of Examples 1-11 and Comparative Examples 1-3 above are shown in Table 2.

[0140] Performance test results of batteries of different examples and comparative examples

[0141] ​​

[0142] The above Examples 1-11 all exhibit energy densities significantly better than Comparative Examples 1-3.

[0143] As can be seen from the performance comparison between Example 1 and Comparative Example 1, compared with using a polyanionic compound alone as the positive electrode active material, when the sodium transition metal oxide and the polyanionic compound are compounded as the positive electrode active material, the powder compaction density of the positive electrode active material in Example 1 is significantly increased compared with the powder compaction density of the positive electrode active material in Comparative Example 1, and the energy density of the sodium metal battery in Example 1 is also significantly higher than that in Comparative Example 1. Thus, it is shown that by compounding the sodium transition metal oxide and the polyanionic compound, the amount of active material that can be loaded on the electrode sheet per unit area is increased, thereby increasing the energy density of the sodium metal battery.

[0144] As can be seen from the performance comparison between Example 1 and Comparative Examples 2-3, compared with Example 1, the specific surface area of the sodium transition metal oxide in Comparative Example 2 is 10 m 2 / g, which is outside the range of 0.4 m 2 / g-4 m 2 / g; and the specific surface area of the polyanionic compound is 30 m 2 / g, which is also outside the range of 10 m 2 / g-20 m 2 / g. It can be seen that the powder compaction density of the positive electrode active material in Example 1 is significantly higher than that in Comparative Examples 2-3, and the energy density of the sodium metal battery in Example 1 is also significantly higher than that in Comparative Examples 2-3. Thus, it is shown that in the case of compounding the sodium transition metal oxide and the polyanionic compound, by controlling the specific surface areas of the two materials to be within the appropriate ranges respectively, the powder compaction density of the compounded positive electrode active material can be improved, thereby improving the energy density of the sodium metal battery. Without controlling the powder compaction density within the above ranges, the effect of improving the powder compaction density and the energy density cannot be achieved by simply compounding the two materials.

[0145] Further, as can be seen from Examples 1-5, controlling the specific surface areas of the sodium transition metal oxide and the polyanionic compound to be within the appropriate ranges respectively can all obtain sodium metal batteries with improved energy densities.

[0146] As can be seen from Examples 1, 6-7, adjusting the ratio of the transition metal oxide and the polyanionic compound in the positive electrode active material can also affect the energy density of the sodium ion battery. Under the same other conditions, by controlling the ratio of the two materials to be the same (Example 7), the highest energy density can be obtained.

[0147] Next, the test method of the physical parameters and performance parameters involved in the embodiments of the present application is introduced.

[0148] 1. Test method of BET

[0149] The test method refers to the standard GB / T 19587-2004 “Determination of the specific surface area of solid substances by gas adsorption BET method”.

[0150] 8g-15g of the sample to be tested is loaded into the sample tube, and the initial mass of the sample to be tested is recorded. The weighed sample to be tested is loaded into the device NOVA2000e. Then degassing is started, and the sample to be tested is heated to 200℃ and kept for 2h. Then the mass of the sample to be tested after degassing is recorded. Then the degassed sample to be tested is reloaded into the device, poured into liquid nitrogen for BET test. The nitrogen pressure is set to 0.08MPa-0.12MPa, and the heating temperature is set to 40℃-350℃. After the test is completed, the specific surface area is read from the test results.

[0151] 2. Test method of powder compaction density

[0152] The powder compaction density of the material can be tested by a method known in the art. For example, GB / T 24533-2009 can be referred to, and an electronic pressure testing machine (such as UTM7305) is used for testing: a certain amount of powder is placed on a compaction special mold, different pressures are set, and the thickness of the powder under different pressures can be read on the device, and the compaction density under different pressures can be calculated.

[0153] 3. Test method of battery energy density

[0154] At 25℃, under normal pressure, the sodium metal battery is charged at 0.2C constant current to 3.65V, then charged at 3.65V constant voltage until the current is less than or equal to 0.05C, then stand for 5min, record the charge capacity at this time, which is the first charge capacity; then discharged at 0.2C constant current to voltage less than or equal to 1.5V, record the discharge capacity at this time. Energy density = discharge capacity / mass of active material. Wherein, the active material refers to the positive active material and the negative active material.

[0155] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the present application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any way as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode active material of a sodium metal battery, characterized by, The positive electrode active material comprises: a sodium transition metal oxide and a polyanionic compound; wherein the specific surface area of the sodium transition metal oxide satisfies: 0.4 m 2 / g ≤ BET1 ≤ 4.0 m 2 / g, and the specific surface area of the polyanionic compound satisfies: 10 m 2 / g ≤ BET2 ≤ 20 m 2 / g; The positive electrode active material polyanionic compound includes Na x M1 y P m O n ; wherein M1 represents a metal element, the metal element including at least one of Mn, Fe, Co, Cu, Al, Ti, V, 1≤x≤2, 0 The sodium transition metal oxide includes Na a M2 b O c ; wherein M2 represents a transition metal element, 0.3≤a≤1.2, 0 The powder compaction density of the positive electrode active material at 29400 N pressure satisfies: 1.2 g / cm 3 ≤ p ≤ 2.8 g / cm 3 .

2. The positive electrode active material according to claim 1, characterized by In the positive electrode active material, a ratio of a mass m1 of the sodium transition metal oxide to a mass m2 of the polyanionic compound satisfies: 1 / 9≤m1 / m2≤1.

3. The positive electrode active material according to claim 1, characterized by A ratio of the mass m1 of the sodium transition metal oxide to a mass m of the positive electrode active material satisfies: 0.1≤m1 / m≤0.

5.

4. The positive electrode active material according to claim 1, characterized by A ratio of the mass m2 of the polyanionic compound to the mass m of the positive electrode active material satisfies: 0.5≤m2 / m≤0.9, and 0<(m1+m2) / m≤1.

5. The positive electrode active material according to any one of claims 1 to 4, characterized by, The anion in the polyanionic compound comprises at least one of a phosphate, a pyrophosphate, a fluoropyrophosphate, and a sulfate.

6. The positive electrode active material according to claim 1, characterized by The transition metal element comprises at least one of Ni, Mn, Fe, Co, Cu, Ti, Cr, V, and Zn.

7. A positive electrode sheet for a sodium metal battery, characterized by, The positive electrode tab comprises the positive electrode active material according to any one of claims 1-6.

8. A battery cell of a sodium metal battery, characterized by The battery cell comprises the positive electrode tab according to claim 7.

9. A sodium metal battery, characterized in that, The sodium metal battery comprises the battery cell according to claim 8.

10. An electrical device, characterized by The electric device comprises the battery cell according to claim 8 and / or the sodium metal battery according to claim 9.

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