Positive electrode sheet, battery cell, battery and electrical device

Abstract

Provided are a positive electrode sheet, a battery cell, a battery, and an electrical device. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, and the positive electrode film layer comprises a positive electrode active material, a sodium supplement and a first conductive agent, wherein the specific surface area of the first conductive agent is not less than 600 m2 / g. The technical solution can improve the coulombic efficiency and the cycle performance of a battery.

Description

Positive electrode sheet, battery cell, battery and electrical device

[0001] Cross-references

[0002] This application claims priority to the Chinese application filed with the Patent Office of China on June 14, 2023, with application number 202310705837.5 and invention name “Positive electrode sheet, battery cell, battery and electrical device”, all contents of which are incorporated into this application by application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a positive electrode sheet, a battery cell, a battery, and an electrical device. Background Art

[0004] In recent years, with the gradual development and application of lithium-ion batteries, from portable electronic devices to high-power electric vehicles, large-scale energy storage power stations, and smart grids, the demand for lithium metal has increased across various industries. However, with the decline in lithium metal reserves and the increasing difficulty of mining, the current lithium metal resources can no longer meet the needs of the lithium battery industry. Sodium, which is in the same main group as lithium, has similar chemical properties and abundant reserves. Therefore, sodium-ion batteries, which operate on similar principles to lithium-ion batteries, are currently being developed and are expected to serve as an important supplement to lithium-ion batteries in large-scale energy storage applications.

[0005] Therefore, how to improve the cycle performance and coulombic efficiency of sodium-ion batteries is an urgent problem that needs to be solved.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode plate, a battery cell, a battery and an electrical device, which can improve the cycle performance and coulombic efficiency of the battery.

[0008] The first aspect of the present application provides a positive electrode sheet, comprising: a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector; the positive electrode film layer comprises a positive electrode active material, a sodium supplement, a first conductive agent and a second conductive agent; wherein the specific surface area of ​​at least one of the first conductive agent and the second conductive agent is not less than 600m 2 / g.

[0009] In the embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer, and the positive electrode film layer includes a positive electrode active material, a sodium supplement, and a first conductive agent; further, the specific surface area of ​​the first conductive agent is not less than 600m 2 / g. Adding a sodium supplement to the positive electrode film layer can effectively supplement the sodium ion loss caused by some irreversible reactions in the battery, and help form a better and more stable SEI film in the battery, thereby improving the coulombic efficiency and cycle performance of the battery. By adding a first conductive agent to the positive electrode film layer, wherein the specific surface area of ​​the first conductive agent is not less than 600m 2 / g, the first conductive agent or the second conductive agent with a high specific surface area can have more contact sites with the sodium supplement agent, thereby reducing the charge transfer and polarization resistance, and then reducing the oxidation voltage of the sodium supplement agent so that the effective voltage of the sodium supplement agent is compatible with the normal operating voltage of the battery, thereby effectively improving the cycle performance and coulombic efficiency of the battery.

[0010] In one possible embodiment, the specific surface area of ​​the first conductive agent is 600-1600 m 2 / g, optionally, the specific surface area of ​​the first conductive agent is 1200-1500m 2 / g.

[0011] In the embodiment of the present application, the sodium supplement agent and the conductive agent with high specific surface area are used together, so that the effective voltage of the sodium supplement agent can be matched with the battery operating voltage, thereby improving the coulombic efficiency and cycle performance of the battery. 2 / g, especially 1200-1500m 2 / g, which can further ensure that the first conductive agent and the sodium supplement agent have more contact sites, and help to further reduce the oxidation voltage of the sodium supplement agent.

[0012] In one possible embodiment, the first conductive agent includes at least one of a chain-shaped conductive agent or a grape-shaped conductive agent; optionally, the first conductive agent includes at least one of conductive carbon black and conductive graphite; optionally, the conductive carbon black includes at least one of acetylene black and Ketjen black.

[0013] In the embodiment of the present application, by using at least one of a chain-shaped conductive agent or a grape-shaped conductive agent as the first conductive agent, the contact form between the first conductive agent and the sodium supplementer is point-to-point, which can ensure that the first conductive agent and the sodium supplementer have more contact sites, thereby improving the effect of the first conductive agent on the sodium supplementer; further, using at least one of conductive carbon black and conductive graphite, which are relatively easy to obtain, as the first conductive agent, especially acetylene black or Ketjen black as the first conductive agent, is conducive to wide application in industry.

[0014] In a possible implementation, when the first conductive agent includes conductive carbon black, the volume average particle size Dv50 of the first conductive agent is 20-60 nm. Optionally, the volume average particle size Dv50 of the first conductive agent is 30-50 nm.

[0015] In the embodiment of the present application, when conductive carbon black is used as the first conductive agent, by limiting the first conductive agent, that is, the volume average particle size Dv50 of these three materials to 20-60nm, especially 30-50nm, the smaller particle size can make the first conductive agent contact with the sodium supplement more evenly.

[0016] In a possible implementation, when the first conductive agent includes conductive graphite, the volume average particle size Dv50 of the first conductive agent is 3-4 μm. Optionally, the volume average particle size Dv50 of the first conductive agent is 3.2-3.6 μm.

[0017] In the embodiment of the present application, when conductive graphite is used as the first conductive agent, by limiting the first conductive agent, that is, the volume average particle size Dv50 of the conductive graphite to 3-4 μm, especially 30-50 nm, the first conductive agent can be in more uniform contact with the sodium supplement.

[0018] In a possible embodiment, the positive electrode film layer further includes a second conductive agent, and the second conductive agent includes at least one of carbon fiber, carbon nanotube, ordered dielectric porous carbon, and graphene.

[0019] In the embodiment of the present application, when the specific surface area is 600-1600m 2 / g, especially 1200-1500m 2 When a first conductive agent of 1000 ng / g is added to a positive electrode film layer including a sodium supplement, the first conductive agent can reduce the oxidation potential of the sodium supplement, allowing the sodium supplement to function properly. By adding at least one of carbon fibers, carbon nanotubes, ordered dielectric porous carbon, and graphene to the positive electrode film layer, the second conductive agent and the sodium supplement are in point-line contact, which helps further achieve voltage compatibility between the sodium supplement and the battery, thereby further improving the battery's cycle performance and coulombic efficiency.

[0020] In a possible embodiment, when the second conductive agent includes carbon nanotubes, the carbon nanotubes have a length of 0.5-30 μm, a diameter of 2-15 nm, and a specific surface area of ​​not less than 200 m 2 / g. Optionally, the carbon nanotubes have a length of 0.5-10 μm, a diameter of 2-6 nm, and a specific surface area of ​​400-600 m 2 / g.

[0021] In one possible embodiment, when the second conductive agent includes ordered mesoporous carbon, the ordered mesoporous carbon has a pore size of 2-50 nm and a specific surface area of ​​500-1500 m 2 / g, optionally, the ordered mesoporous carbon has a pore size of 3.2-6.6 nm and a specific surface area of ​​800-1300 m2 / g.

[0022] In a possible implementation, when the second conductive agent includes graphene, the graphene has a thickness of 0.6-4 nm and a sheet diameter of 0.5-5 μm. Optionally, the graphene has a thickness of 1.5-3.2 nm and a sheet diameter of 0.5-3 μm.

[0023] In the embodiment of the present application, when the first conductive agent and the second conductive agent are used together to reduce the oxidation potential of the sodium supplement, the cycle performance and coulombic efficiency of the battery can be further improved. 2 By limiting the performance parameters of the second conductive agent to the above range, the second conductive agent with better conductivity can better assist the first conductive agent, thereby further improving the performance of the battery.

[0024] In a possible implementation manner, the mass ratio of the first conductive agent to the second conductive agent is 1-49. Optionally, the mass ratio of the first conductive agent to the second conductive agent is 4-9.

[0025] In the embodiments of the present application, to further improve battery performance, a mixed first and second conductive agents are used in the battery membrane layer to reduce the effective voltage of the sodium supplement. By limiting the mass ratio of the first and second conductive agents to 1-49, particularly 4-9, the possibility of insufficiently reducing the effective voltage of the sodium supplement due to insufficient addition of the first conductive agent can be reduced.

[0026] In one possible embodiment, based on 100 parts by weight of the positive electrode film layer, the sum of the weight parts of the first conductive agent and the second conductive agent is 0.1-5 parts by weight. Optionally, the sum of the weight parts of the first conductive agent and the second conductive agent is 0.5-3 parts by weight.

[0027] In the embodiment of the present application, by limiting the conductive agent, that is, the sum of the masses of the first conductive agent and the second conductive agent, to 0.1%-5%, especially 0.5%-3%, of the positive electrode film layer, the effective voltage of the sodium supplement can be effectively reduced so that the sodium supplement can improve the cycle performance and coulombic efficiency of the battery, and the energy density of the battery will not be affected by the excessive proportion of the first conductive agent and the second conductive agent.

[0028] In a possible embodiment, based on 100 parts by weight of the positive electrode film layer, the weight of the sodium supplement is 0.5-20 parts by weight. Optionally, the weight of the sodium supplement is 1-5 parts by weight.

[0029] In the embodiment of the present application, by limiting the sodium supplement to 0.5%-20%, especially 1%-5% of the positive electrode film layer, the sodium loss in the battery can be effectively compensated without affecting the mass proportion of the positive electrode active material due to excessive proportion.

[0030] In a possible embodiment, the sodium supplement includes at least one of the following inorganic sodium supplements or organic sodium supplements, the inorganic sodium supplement includes NaN3, Na2O2, Na2O, Na2CO3, NaNO2, NaBH4, NaNH2, Na2NiO2, NaCrO2, Na3P, Na2S, the organic sodium supplement includes CH3COONa, C7H6NNaO2, C 10 H 12 N2Na4O8、C 14 H 18 N3Na5O 10 、Na a C b H c O d , 1≤a≤2, 2≤b≤6, 0≤c≤2, 2≤d≤6, optionally, the sodium supplement includes Na2C2O4.

[0031] In the embodiments of the present application, when at least one of the above-mentioned inorganic sodium supplement or organic sodium supplement is used as the sodium supplement, the sodium supplement can compensate for the irreversible sodium ion loss during the battery cycle, while also not affecting the potential of the positive electrode active material, thereby improving the coulombic efficiency and cycle performance of the battery. In particular, when the sodium supplement includes Na2C2O4, Na2C2O4 decomposes and releases sodium ions and gas during battery formation and charging. The gas produced by the decomposition can be removed during the formation stage, and the sodium ions produced by the decomposition can effectively solve the problems of low battery energy density and poor cycle stability caused by irreversible sodium ion consumption, that is, it can both improve battery performance and have no adverse effects on the environment and the battery.

[0032] In one possible embodiment, the compaction density of the positive electrode sheet is 1.2-2.8 g / cm 3 Optionally, the compaction density of the positive electrode sheet is 1.6-2.3 g / cm 3 .

[0033] In the embodiment of the present application, the compaction density of the positive electrode sheet is limited to 1.2-2.8 g / cm 3 , especially 1.6-2.3g / cm 3 , which helps to further improve the energy density of the battery.

[0034] In a possible implementation, the thickness of the positive electrode plate is 50-90 μm. Optionally, the thickness of the positive electrode plate is 65-80 μm.

[0035] In the embodiment of the present application, by limiting the thickness of the positive electrode sheet to 50-90 μm, especially 65-80 μm, it helps to further improve the energy density of the battery.

[0036] In one possible embodiment, the coating weight of the positive electrode sheet is 3.5-35 mg / cm 2 Optionally, the coating weight of the positive electrode sheet is 10-25 mg / cm 2 .

[0037] In the embodiment of the present application, the coating weight of the positive electrode sheet is limited to 3.5-35 mg / cm 2 , especially 10-25 mg / cm 2 , which helps to further improve the energy density of the battery.

[0038] In one possible embodiment, the positive electrode active material includes Na x R y (PO4) z (P2O7) k , wherein 1≤x≤7, 1≤y≤4, 1≤z≤2, 1≤k≤4, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, and Pb.

[0039] In the embodiments of the present application, the use of the above materials as positive electrode active materials helps to further improve the energy density of the battery.

[0040] A second aspect of the present application provides a battery cell comprising the positive electrode sheet according to any one of the embodiments in the first aspect of the present application.

[0041] In a possible embodiment, the battery cell further includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a conductive agent.

[0042] A third aspect of the present application provides a battery, comprising a battery cell according to any one of the embodiments in the second aspect of the present application.

[0043] The fourth aspect of the present application provides an electrical device comprising the battery according to the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0045] FIG1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0046] FIG2 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0047] FIG3 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0048] FIG4 is a schematic diagram of a battery according to an embodiment of the present application;

[0049] FIG5 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0050] FIG6 is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0051] The following describes in detail embodiments of the positive electrode sheet, battery cell, battery, and electrical device of the present application, 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. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0052] " 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 specific 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.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0054] 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.

[0055] Unless otherwise specified, all steps of the present application may be performed sequentially, randomly, or optionally 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.

[0056] The terms "above", "below", "greater than" or "less than" as used in this application are inclusive of the number, for example, "at least one" means one or more, and "at least one of A and B" means "A", "B" or "A and B".

[0057] The working principle of sodium batteries is similar to that of lithium batteries, that is, they utilize the intercalation and deintercalation of sodium ions between the positive and negative electrodes to achieve charging and discharging. Compared with lithium batteries, sodium batteries have the following advantages: (1) the reserves of metallic sodium are more abundant than metallic lithium, which has a significant price advantage; (2) at the same concentration, the conductivity of sodium salt is higher than that of lithium salt, so a lower concentration of electrolyte can be used, and the battery manufacturing cost is relatively low.

[0058] Similar to lithium batteries, the cycle life of sodium batteries is related to the stability of the interface (such as the electrode-electrolyte interface). The formation of the interface is often accompanied by the irreversible consumption of sodium ions, especially the interface between the negative electrode and the electrolyte. This is because the SEI film formed during the first charge and discharge of the battery consumes sodium ions, and this consumption is irreversible. However, if too much sodium ion is consumed, it will have a significant impact on the performance of the battery. Therefore, how to reduce the irreversible consumption of limited sodium ions is the key to restricting the cycle stability and coulombic efficiency of sodium batteries.

[0059] To address these issues, currently common methods include spraying sodium powder, spraying organic sodium solutions, and adding positive electrode sodium supplements. Adding sodium supplements to the positive electrode has attracted attention due to its effectiveness and ease of use. However, some current sodium supplements have high oxidation potentials that are incompatible with the battery system, rendering them ineffective. Therefore, achieving voltage compatibility between the sodium supplement and the battery system, thereby improving the battery's coulombic efficiency and cycle performance, is a pressing issue.

[0060] In view of this, the present application provides 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. The positive electrode film layer includes a sodium supplement and a first conductive agent. Furthermore, the specific surface area of ​​the first conductive agent is not less than 600m 2 / g, sodium supplement helps improve the cycle performance and coulombic efficiency of the battery, and the specific surface area is not less than 600m 2 / g of the first conductive agent can reduce the effective voltage of the sodium supplement agent, achieve voltage compatibility between the sodium supplement agent and the battery system, and thus effectively improve the cycle performance and coulombic efficiency of the battery.

[0061] The positive electrode sheet, battery cell, battery and electrical device of the present application are described below with reference to the accompanying drawings.

[0062] In addition, the technical solution of the present application is applicable to sodium ion batteries or sodium metal batteries, and the present application does not limit this; for the convenience of description, the following description will take sodium ion batteries as an example.

[0063] [Positive electrode]

[0064] The first aspect of the present application provides a positive electrode sheet. FIG1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application. As shown in FIG1 , the positive electrode sheet 121 includes a positive electrode current collector 122 and a positive electrode film layer 123 disposed on at least one side of the positive electrode current collector 122. The positive electrode film layer 123 includes a positive electrode active material, a sodium supplement, and a first conductive agent; wherein the specific surface area of ​​the first conductive agent is not less than 600 m 2 / g.

[0065] A first conductive agent is added to the positive electrode film layer 123, and the specific surface area of ​​the first conductive agent is not less than 600m 2 / g, which can reduce the effective voltage of the sodium supplement and achieve voltage compatibility between the sodium supplement and the battery, thereby improving the coulombic efficiency and cycle performance of the battery.

[0066] Typically, a battery cell consists of a positive electrode sheet 121, a separator, a negative electrode sheet, and an electrolyte. During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0067] It should be noted here that the “positive electrode sheet” and “negative electrode sheet” mentioned in the embodiments of the present application refer to the positive electrode sheet 121 and the negative electrode sheet as a whole including active materials, current collectors or other additives.

[0068] The positive electrode sheet 121 includes a positive electrode current collector 122 and a positive electrode film layer 123 provided on at least one surface of the positive electrode current collector 122. The positive electrode film layer 123 includes a sodium supplement and a first conductive agent. The specific surface area of ​​the first conductive agent is not less than 600 m2 / g.

[0069] As an example, the positive electrode current collector 122 has two opposite surfaces in its thickness direction, and the positive electrode film layer 123 is disposed on either or both of the two opposite surfaces of the positive electrode current collector 122 .

[0070] The sodium supplement is a substance that can supplement the sodium ions in the sodium ion battery. Specifically, the sodium supplement can be some organic or inorganic substances containing sodium ions, for example, sodium oxides or sodium salts.

[0071] In the above scheme, the positive electrode sheet 121 includes a positive electrode current collector 122 and a positive electrode film layer 123. The positive electrode film layer 123 includes a positive electrode active material, a sodium supplement, and a first conductive agent. Furthermore, the specific surface area of ​​the first conductive agent is not less than 600m2 / g. The sodium supplement is added to the positive electrode film layer 123. The sodium supplement can effectively supplement the sodium ion loss caused by some irreversible reactions in the battery, and help to form a better and more stable SEI film in the battery, thereby improving the coulombic efficiency and cycle performance of the battery. By adding the first conductive agent to the positive electrode film layer 123, wherein the specific surface area of ​​the first conductive agent is not less than 600m2 / g, the battery can be effectively supplemented by the sodium supplement. 2 / g, the first conductive agent with a high specific surface area can have more contact sites with the sodium supplement agent, thereby reducing the charge transfer and polarization resistance, and then reducing the oxidation voltage of the sodium supplement agent so that the effective voltage of the sodium supplement agent is compatible with the normal operating voltage of the battery, thereby effectively improving the cycle performance and coulombic efficiency of the battery.

[0072] In some embodiments, the specific surface area of ​​the first conductive agent is 600-1600 m 2 / g, optionally, the specific surface area of ​​the first conductive agent is 1200-1500m 2 / g.

[0073] In the above scheme, the sodium supplement agent and the conductive agent with high specific surface area are used together, so that the effective voltage of the sodium supplement agent can be matched with the battery operating voltage, thereby improving the coulombic efficiency and cycle performance of the battery. 2 / g, especially 1200-1500m 2 / g, which can further ensure that the first conductive agent and the sodium supplement agent have more contact sites, and help to further reduce the oxidation voltage of the sodium supplement agent.

[0074] In some embodiments, the first conductive agent includes at least one of a chain-shaped conductive agent or a grape-shaped conductive agent; optionally, the first conductive agent includes at least one of conductive carbon black and conductive graphite; optionally, the conductive carbon black includes at least one of acetylene black and Ketjen black.

[0075] It should be noted here that grape-shaped conductive agent refers to a conductive agent whose microscopic particles are in the shape of bunches of grapes, such as conductive carbon black.

[0076] In the above scheme, by using at least one of a chain-shaped conductive agent or a grape-shaped conductive agent as the first conductive agent, the contact form between the first conductive agent and the sodium supplementer is point-to-point, which can ensure that the first conductive agent and the sodium supplementer have more contact sites, thereby improving the effect of the first conductive agent on the sodium supplementer; further, using at least one of conductive carbon black and conductive graphite, which are relatively easy to obtain, as the first conductive agent, especially acetylene black or Ketjen black as the first conductive agent, is conducive to wide application in industry.

[0077] In some embodiments, when the first conductive agent includes conductive carbon black, the volume average particle size Dv50 of the first conductive agent is 20-60 nm. Optionally, the volume average particle size Dv50 of the first conductive agent is 30-50 nm.

[0078] In the above scheme, when conductive carbon black is used as the first conductive agent, by limiting the first conductive agent, that is, the volume average particle size Dv50 of these three materials to 20-60nm, especially 30-50nm, the smaller particle size can make the first conductive agent contact with the sodium supplement more uniformly.

[0079] In some embodiments, when the first conductive agent includes conductive graphite, the volume average particle size Dv50 of the first conductive agent is 3-4 μm. Optionally, the volume average particle size Dv50 of the first conductive agent is 3.2-3.6 μm.

[0080] In the above solution, when conductive graphite is used as the first conductive agent, by limiting the volume average particle size Dv50 of the first conductive agent, ie, the conductive graphite, to 3-4 μm, especially 30-50 nm, the first conductive agent can be in more uniform contact with the sodium supplement.

[0081] In some embodiments, the positive electrode film layer 123 further includes a second conductive agent, and the second conductive agent includes at least one of carbon fiber, carbon nanotube, ordered dielectric porous carbon, and graphene.

[0082] In the above scheme, when the specific surface area is 600-1600m 2 / g, especially 1200-1500m 2 When a first conductive agent of 1000 ng / g is added to a positive electrode film layer including a sodium supplement, the first conductive agent can reduce the oxidation potential of the sodium supplement, allowing the sodium supplement to function properly. By adding at least one of carbon fibers, carbon nanotubes, ordered dielectric porous carbon, and graphene to the positive electrode film layer, the second conductive agent and the sodium supplement are in point-line contact, which helps further achieve voltage compatibility between the sodium supplement and the battery, thereby further improving the battery's cycle performance and coulombic efficiency.

[0083] In some embodiments, when the second conductive agent includes carbon nanotubes, the carbon nanotubes have a length of 0.5-30 μm, a diameter of 2-15 nm, and a specific surface area of ​​not less than 200 m 2 / g. Optionally, the carbon nanotubes have a length of 0.5-10 μm, a diameter of 2-6 nm, and a specific surface area of ​​400-600 m 2 / g.

[0084] In some embodiments, when the second conductive agent comprises ordered mesoporous carbon, the ordered mesoporous carbon has a pore size of 2-50 nm and a specific surface area of ​​500-1500 m 2 / g, optionally, the pore size of the ordered mesoporous carbon is 3.2-6.6 nm, and the specific surface area is 800-1300 m 2 The ordered mesoporous carbon may include CMK-3 ordered mesoporous carbon and CMK-8 ordered mesoporous carbon.

[0085] In some embodiments, when the second conductive agent includes graphene, the graphene has a thickness of 0.6-4 nm and a sheet diameter of 0.5-5 μm. Alternatively, the graphene has a thickness of 1.5-3.2 nm and a sheet diameter of 0.5-3 μm.

[0086] It should be noted that the graphene thickness herein may refer to the total thickness of multiple layers of graphene. Graphene is a layered material, and the thickness of a single layer of graphene is generally 0.3-0.4 nm. This application does not particularly limit the number of layers or thickness of the single layers of graphene in the graphene; it is sufficient to ensure that the final graphene thickness falls within the above range. For example, the final graphene form may contain 2-10 layers of single layers of graphene.

[0087] In the above scheme, when the first conductive agent and the second conductive agent are used to jointly reduce the oxidation potential of the sodium supplement agent, the cycle performance and coulombic efficiency of the battery can be further improved. 2 By limiting the performance parameters of the second conductive agent to the above range, the second conductive agent with better conductivity can better assist the first conductive agent, thereby further improving the performance of the battery.

[0088] In some embodiments, the mass ratio of the first conductive agent to the second conductive agent is 1-49. Optionally, the mass ratio of the first conductive agent to the second conductive agent is 4-9.

[0089] In the above solution, to further improve battery performance, a mixed first and second conductive agents are used in the battery membrane layer 123 to reduce the effective voltage of the sodium supplement. By limiting the mass ratio of the first and second conductive agents to 1-49, particularly 4-9, the possibility of insufficiently reducing the effective voltage of the sodium supplement due to insufficient addition of the first conductive agent can be reduced.

[0090] In some embodiments, based on 100 parts by weight of the positive electrode film 123 , the sum of the weight parts of the first conductive agent and the second conductive agent is 0.1-5 parts by weight. Optionally, the sum of the weight parts of the first conductive agent and the second conductive agent is 0.5-3 parts by weight.

[0091] In the above scheme, by limiting the conductive agent, that is, the sum of the masses of the first conductive agent and the second conductive agent, to 0.1%-5%, especially 0.5%-3%, of the positive electrode film layer 123, the effective voltage of the sodium supplement can be effectively reduced so that the sodium supplement can improve the cycle performance and coulombic efficiency of the battery, and the energy density of the battery will not be affected by the excessive proportion of the first conductive agent and the second conductive agent.

[0092] In some embodiments, based on 100 parts by weight of the positive electrode film layer 123 , the weight of the sodium supplement is 0.5-20 parts by weight. Optionally, the weight of the sodium supplement is 1-5 parts by weight.

[0093] In the above solution, by limiting the sodium supplement to 0.5%-20%, especially 1%-5%, of the positive electrode film layer 123, the sodium loss in the battery can be effectively compensated without affecting the mass proportion of the positive electrode active material due to an excessively high proportion.

[0094] In some embodiments, the sodium supplement comprises at least one of the following inorganic sodium supplements or organic sodium supplements, wherein the inorganic sodium supplement comprises NaN3, Na2O2, Na2O, Na2CO3, NaNO2, NaBH4, NaNH2, Na2NiO2, NaCrO2, Na3P, Na2S, and the organic sodium supplement comprises CH3COONa, C7H6NNaO2, C 10 H 12 N2Na4O8、C 14 H 18 N3Na5O 10 、Na a C b H c O d , 1≤a≤2, 2≤b≤6, 0≤c≤2, 2≤d≤6, optionally, the sodium supplement includes Na2C2O4.

[0095] In the above scheme, when at least one of the inorganic or organic sodium supplements is used as the sodium supplement, the sodium supplement can compensate for the irreversible sodium ion loss during the battery cycle while not affecting the potential of the positive electrode active material, thereby improving the battery's coulombic efficiency and cycle performance. In particular, when the sodium supplement includes Na2C2O4, Na2C2O4 decomposes and releases sodium ions and gas during battery formation and charging. The gas produced by the decomposition can be removed during the formation stage, while the sodium ions produced by the decomposition can effectively address the low battery energy density and poor cycle stability caused by the irreversible loss of sodium ions. This improves battery performance while having no adverse effects on the environment or the battery.

[0096] In some embodiments, the compacted density of the positive electrode sheet 121 is 1.2-2.8 g / cm 3 Optionally, the compaction density of the positive electrode sheet 121 is 1.6-2.3 g / cm 3 .

[0097] In the embodiment of the present application, the compaction density of the positive electrode sheet 121 is limited to 1.2-2.8 g / cm 3 , especially 1.6-2.3g / cm 3 , which helps to further improve the energy density of the battery.

[0098] In a possible implementation, the thickness of the positive electrode plate 121 is 50-90 μm. Optionally, the thickness of the positive electrode plate 121 is 65-80 μm.

[0099] In the embodiment of the present application, by limiting the thickness of the positive electrode sheet 121 to 50-90 μm, especially 65-80 μm, it helps to further improve the energy density of the battery.

[0100] In one possible embodiment, the coating weight of the positive electrode sheet 121 is 3.5-35 mg / cm 2 Optionally, the coating weight of the positive electrode sheet 121 is 10-25 mg / cm 2 .

[0101] In the embodiment of the present application, the coating weight of the positive electrode sheet 121 is limited to 3.5-35 mg / cm 2 , especially 10-25 mg / cm 2 , which helps to further improve the energy density of the battery.

[0102] In some embodiments, the positive electrode active material includes Na x R y (PO4) z (P2O7) k, wherein 1≤x≤7, 1≤y≤4, 1≤z≤2, 1≤k≤4, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, and Pb.

[0103] In the above scheme, by using the above materials as the positive electrode active material, it helps to further improve the energy density of the battery.

[0104] It should be noted here that during the charge and discharge process of the battery, as Na ions are continuously deintercalated and consumed, the molar content of Na in the battery is different when it is discharged to different states. The above limitation of x includes the molar content of Na in different charge and discharge states of the battery.

[0105] In some embodiments, the positive electrode current collector 122 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 layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode active material may further include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, this application is not limited to these materials; other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0107] In some embodiments, the transition metal in the sodium transition metal oxide may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0108] In some embodiments, the polyanionic compound may be a compound having sodium ions, transition metal ions, and tetrahedral (YO4)n-anion units. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be at least one of P, S, and Si; n represents (YO4)n-anion units. n - valence.

[0109] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n - A class of compounds of anion units and halogen anions. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y may include at least one of P, S and Si, and n represents (YO4) n - valence state; the halogen may include at least one of F, Cl and Br.

[0110] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n - Anion unit, polyhedron unit (ZO y ) m + and an optional halogen anion. Y may include at least one of P, S and Si, and n represents (YO4) n - valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZO y ) m + valence state; halogen may include at least one of F, Cl and Br.

[0111] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0112] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). Transition metals can include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0113] In some embodiments, the positive electrode film 123 may further 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.

[0114] In some embodiments, the positive electrode sheet 121 can be prepared by the following method: the components for preparing the positive electrode sheet 121, such as the positive electrode active material, the first conductive agent, the second conductive agent, the sodium supplement, 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 collector 122, and after drying, cold pressing and other processes, the positive electrode sheet 121 can be obtained.

[0115] The positive electrode plate 121 of the present application does not exclude other additional functional layers in addition to the positive electrode film layer 122. For example, in some embodiments, the positive electrode plate 121 of the present application further includes a conductive primer layer disposed on the surface of the positive electrode current collector 122 and sandwiched between the positive electrode current collector 122 and the positive electrode film layer 123. In other embodiments, the positive electrode plate 121 of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0116] [Negative electrode]

[0117] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0118] 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 is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0119] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), or a current collector that combines support capabilities with functional elements, such as carbon cloth, carbon film, carbonaceous, porous current collector, alloyed modified current collector, sodium-philic modified current collector.

[0120] In some embodiments, the negative electrode plate can be a rolled metal foil or a surface coated with an inert layer of metal powder coated on the current collector; it can be a functional coating negative electrode, such as a carbon material coating (including single-arm, multi-arm conductive carbon tubes, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, soft carbon and hard carbon, etc.), lithium-philic / sodium-philic metal composite coating, etc.

[0121] In some embodiments, the negative electrode plate is an alkali metal negative electrode. The alkali metal negative electrode can be a current collector with an alkali metal layer pre-applied thereon, or it can be a negative electrode current collector that forms an alkali metal layer on the negative electrode current collector during charge and discharge. This application is not limited to this.

[0122] 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.

[0123] In some embodiments, the negative electrode film layer may further include a binder. 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).

[0124] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0125] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0126] 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.

[0127] [Electrolytes]

[0128] 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.

[0129] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0130] In some embodiments, the electrolyte salt may be, for example, a sodium salt, including but not limited to at least one of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3. One of the sodium salts may be used alone, or two or more may be used simultaneously.

[0131] In some embodiments, as an example, the organic solvent includes but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE). The above organic solvents can be used alone or in combination. Alternatively, two or more organic solvents are used in combination.

[0132] In some embodiments, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0133] In some embodiments, as an example, the additive includes but is not limited to at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), diethylene sulfate (DTD), propylene sulfate, vinyl sulfite (ES), 1,3-propane sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN), adiponitrile (AND), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) borate (TMSB).

[0134] The electrolyte solution can be prepared according to conventional methods in the art. For example, an organic solvent, a sodium electrolyte salt, and optional additives can be uniformly mixed to obtain the electrolyte solution. The order in which the materials are added is not particularly limited. For example, the sodium electrolyte salt and the optional additives can be added to the organic solvent and mixed uniformly to obtain the electrolyte solution; alternatively, the sodium electrolyte salt can be first added to the organic solvent, and then the optional additives can be added to the organic solvent and mixed uniformly to obtain the electrolyte solution.

[0135] [Isolation film]

[0136] In some embodiments, the secondary battery further includes a separator. This separator is positioned between the positive electrode sheet 121 and the negative electrode sheet, primarily preventing short circuits between the positive and negative electrodes while allowing active ions to pass through. This application does not specifically limit the type of separator; any known porous separator with good chemical and mechanical stability may be used.

[0137] 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.

[0138] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0139] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0140] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG2 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0141] Figure 3 is a schematic structural diagram of a battery cell according to an embodiment of the present application. In some embodiments, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 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 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet 121, the negative electrode sheet and the isolation film can be formed into an electrode assembly 12 by a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The number of electrode assemblies 12 contained in the battery cell 100 may be one or more, and those skilled in the art can select according to specific actual needs.

[0142] In some embodiments, the battery cells 100 may be assembled into a battery module. The battery module may contain one or more battery cells 100. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0143] Figure 4 is a schematic diagram of a battery according to one embodiment of the present application, and Figure 5 is a schematic diagram of the structure of a battery according to one embodiment of the present application. Referring to Figures 4 and 5, a battery 400 may include a battery box and a plurality of battery cells 100 disposed within the battery box. The battery box includes an upper box body 401 and a lower box body 402. The upper box body 401 can be placed over the lower box body 402 to form an enclosed space for accommodating the battery cells 100. The plurality of battery cells 100 can be arranged in any manner within the battery box.

[0144] In addition, the present application also provides an electric device, which includes at least one of the positive electrode sheet 121, battery cell 100 or battery provided in the present application. The positive electrode sheet 121, battery cell 100, or battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric 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.

[0145] For example, Figure 6 is a structural diagram of a vehicle according to an embodiment of the present application. As shown in Figure 6, vehicle 1 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 500, a controller 600 and a battery 400 can be provided inside the vehicle 1, and the controller 600 is used to control the battery 400 to supply power to the motor 500. For example, a battery 400 can be provided at the bottom, front or rear of the vehicle 1. The battery 400 can be used to power the vehicle 1. For example, the battery 400 can be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 400 can not only serve as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0146] As the electrical device, the positive electrode sheet 121 , the battery cell 100 or the battery 400 can be selected according to its usage requirements.

[0147] The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0148] In order to meet the requirements of the electrical device for high power and high energy density of the battery, the battery cell 100 or the battery 400 may be used.

[0149] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use the battery cell 100 as a power source.

[0150] [Example]

[0151] 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.

[0152] [Example 1]

[0153] 1) Preparation of sodium ion batteries

[0154] 1.1) Preparation of the positive electrode: The positive electrode active material Na4Fe3(PO4)2(P2O7), the sodium supplement Na2C2O4, the first conductive agent conductive carbon black, the second conductive agent carbon nanotubes, acetylene black, and the binder polyvinylidene fluoride (PVDF) are weighed in a mass ratio of 90%: 3%: 4%: 0.5%: 1%: 1.5%, and then N-methylpyrrolidone (NMP) is added to adjust it into a slurry. Use a scraper to evenly coat it on the surface of the positive electrode current collector Al foil, place it in a vacuum drying oven at 110°C and dry it for 5-6 hours, then dry it, cold press it, and cut it to obtain the positive electrode sheet. Among them, the specific surface area of ​​the first conductive agent conductive carbon black is 1000m2 / g, the weight of the first conductive agent is 4 parts by weight, and the volume average particle size Dv50 is 30nm; the length of the second conductive agent carbon nanotube is 2μm, the diameter is 3nm, and the specific surface area is 400m 2 / g, the weight portion of the second conductive agent is 0.5 weight portion, and the mass ratio of the first conductive agent to the second conductive agent is 8; the sodium supplement agent is Na2C2O4, and the weight portion of the sodium supplement agent is 3 weight portions.

[0155] 1.2) Preparation of the negative electrode: artificial graphite, a conductive agent, acetylene black, a binder, styrene-butadiene rubber (SBR), and a thickener, sodium carboxymethyl cellulose (CMC), are mixed in a suitable amount of deionized water solvent system at a weight ratio of 97.5%:0.7%:1.8%:1% to obtain the negative electrode active material. The negative electrode active material is coated on a Cu foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0156] 1.3) Preparation of diaphragm: PE porous polymer film is used as the isolation membrane.

[0157] 1.4) Electrolyte: Dissolve EC / EMC / DMC in 1M NaPF6 at a volume ratio of 1:1:1 and stir evenly.

[0158] 1.5) Assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide separation. Winding is done to form an electrode assembly, and electrolyte is added. The lithium-ion battery is then hot-pressed at 100°C and 250 MPa for 2 minutes.

[0159] [Example 2]

[0160] The preparation of the sodium ion battery of Example 2 is basically the same as that of Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 600 m 2 / g.

[0161] [Example 3]

[0162] The preparation of the sodium ion battery of Example 3 is basically the same as that of Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 1200 m 2 / g.

[0163] [Example 4]

[0164] The preparation of the sodium ion battery of Example 4 is basically the same as that of Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 1500 m 2 / g.

[0165] [Example 5]

[0166] The preparation of the sodium ion battery of Example 5 is basically the same as that of Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 1600 m 2 / g.

[0167] [Example 6]

[0168] The preparation of the sodium ion battery of Example 6 is basically the same as that of Example 1, except that the first conductive agent is Ketjen black.

[0169] [Example 7]

[0170] The preparation of the sodium ion battery of Example 7 is basically the same as that of Example 1, except that the first conductive agent is conductive graphite.

[0171] [Example 8]

[0172] The preparation of the sodium ion battery of Example 8 is basically the same as that of Example 7, except that the specific surface area of ​​the first conductive agent is 1200 m 2 / g.

[0173] [Example 9]

[0174] The preparation of the sodium ion battery of Example 9 is basically the same as that of Example 1, except that there is no second conductive agent in the positive electrode plate, and the mass ratio of the positive electrode active material Na4Fe3(PO4)2(P2O7), the sodium supplement Na2C2O4, the first conductive agent conductive carbon black, acetylene black, and the binder polyvinylidene fluoride (PVDF) is 90.5%:3%:4%:1%:1.5%.

[0175] [Example 10]

[0176] The preparation of the sodium ion battery of Example 10 is basically the same as that of Example 1, except that the parameters of the second conductive agent carbon nanotubes are different. The parameters of the second conductive agent are: length: 2 μm, diameter: 3 nm, BET: 500 m 2 / g.

[0177] [Example 11]

[0178] The preparation of the sodium ion battery of Example 11 is basically the same as that of Example 1, except that the second conductive agent is CMK-3 ordered mesoporous carbon, wherein the parameters of the second conductive agent are: pore size: 5nm, BET: 600m 2 / g.

[0179] [Example 12]

[0180] The preparation of the sodium ion battery of Example 12 is basically the same as that of Example 1, except that the weight ratio of the first conductive agent is 2 parts by weight; the mass ratio of Na4Fe3(PO4)2(P2O7), sodium supplement Na2C2O4, first conductive agent conductive carbon black, second conductive agent carbon nanotubes, acetylene black, and binder polyvinylidene fluoride (PVDF) is 92%:3%:2%:0.5%:1%:1.5%, wherein the weight ratio of the first conductive agent to the second conductive agent is 4.

[0181] [Example 13]

[0182] The preparation of the sodium ion battery of Example 13 is basically the same as that of Example 1, except that the weight part of the second conductive agent is 1 weight part; the mass ratio of Na4Fe3(PO4)2(P2O7), sodium supplement Na2C2O4, first conductive agent conductive carbon black, second conductive agent carbon nanotubes, acetylene black, and binder polyvinylidene fluoride (PVDF) is 91.5%:3%:2%:1%:1%:1.5%, wherein the weight ratio of the first conductive agent to the second conductive agent is 2.

[0183] [Example 14]

[0184] The preparation of the sodium ion battery of Example 14 is basically the same as that of Example 1, except that the positive electrode active material Na4Fe3(PO4)2(P2O7) is replaced by Na4Mg3(PO4)2(P2O7).

[0185] [Example 15]

[0186] The preparation of the sodium ion battery of Example 15 is basically the same as that of Example 1, except that the positive electrode active material Na4Fe3(PO4)2(P2O7) is replaced by Na3V2(PO4)3.

[0187] [Example 16]

[0188] The preparation of the sodium ion battery of Example 16 is basically the same as that of Example 1, except that the sodium supplement is Na2C4O4.

[0189] [Example 17]

[0190] The preparation of the sodium ion battery of Example 17 is basically the same as that of Example 1, except that the weight portion of the sodium supplement is 0.5 weight portion, and the mass ratio of Na4Fe3(PO4)2(P2O7), sodium supplement Na2C2O4, first conductive agent conductive carbon black, second conductive agent carbon nanotubes, acetylene black, and binder polyvinylidene fluoride (PVDF) is 92.5%:0.5%:4%:0.5%:1%:1.5%.

[0191] [Example 18]

[0192] The preparation of the sodium ion battery of Example 18 is basically the same as that of Example 1, except that the weight portion of the sodium supplement is 6 parts by weight, and the mass ratio of Na4Fe3(PO4)2(P2O7), sodium supplement Na2C2O4, first conductive agent conductive carbon black, second conductive agent carbon nanotubes, acetylene black, and binder polyvinylidene fluoride (PVDF) is 87%:6%:4%:0.5%:1%:1.5%.

[0193] [Comparative Example 1]

[0194] The preparation of the sodium ion battery of Comparative Example 1 is basically the same as that of Example 1, except that the components of the positive electrode plate are Na4Fe3(PO4)2(P2O7), the first conductive agent conductive carbon black, acetylene black, and the binder polyvinylidene fluoride (PVDF). The mass ratio is 93.5%:4%:1%:1.5%; and the specific surface area of ​​the first conductive agent conductive carbon black is 400m 2 / g.

[0195] [Comparative Example 2]

[0196] The preparation of the sodium ion battery of Comparative Example 2 is basically the same as that of Comparative Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 1000 m 2 / g.

[0197] [Comparative Example 3]

[0198] The preparation of the sodium ion battery of Comparative Example 3 is basically the same as that of Example 1, except that the components of the positive electrode plate are Na4Fe3(PO4)2(P2O7), sodium supplement Na2C2O4, first conductive agent conductive carbon black, acetylene black, and binder polyvinylidene fluoride (PVDF). The mass ratio is 90.5%:3%:4%:1%:1.5%; and the specific surface area of ​​the first conductive agent conductive carbon black is 400m 2 / g.

[0199] [Comparative Example 4]

[0200] The preparation of the sodium ion battery of Comparative Example 4 is basically the same as that of Example 1, except that the specific surface area of ​​the first conductive agent, the conductive carbon black, is 400 m 2 / g, the parameters of the second conductive agent carbon nanotube are: length: 0.4μm, diameter: 1nm, BET: 100m 2 / g.

[0201] 2. Performance characterization of sodium ion battery positive electrode

[0202] 2.1) Measurement of material specific surface area: Refer to GB / T 19587-2004 "Gas adsorption BET method for determination of specific surface area of ​​solid substances", GB / T 13390-2004 "Metal powders - Determination of specific surface area - Nitrogen adsorption method" or GB / T 7702.20-2008 "Test method for coal-based granular activated carbon - Determination of specific surface area", and use any BET tester available on the market.

[0203] 2.2) Measurement of volume average particle size Dv50: Particle size distribution laser diffraction method according to GB / T 19077-2016 can be used for testing using a laser particle size analyzer (e.g., Master Size 3000).

[0204] 2.3) Compacted density measurement: Refer to GB / T 24533-2009 for details. A certain amount of powder is placed in a compaction mold. The mold is then placed on a compaction density instrument. The powder is weighed (m) and the pressure is set to 400 kN. The instrument reads the thickness (after unloading) and volume (v) of the powder. The compacted density is calculated using the equation ρ = m / v.

[0205] Table 1 Specific experimental parameters of Examples 1-18 and Comparative Examples 1-4

[0206] 3. Performance Characterization of Sodium Ion Batteries

[0207] 3.1) Initial Coulombic Efficiency Test: At room temperature, charge the battery to 3.9V at a constant current of 1 / 3C, then charge at a constant voltage of 3.9V until the current drops to 0.05C to obtain the initial charge capacity Cc1. Discharge the battery to 1.5V at a constant current of 1 / 3C to obtain the initial discharge capacity Cd1. The battery's initial Coulombic efficiency = Cd1 / Cc1. Please refer to Table 2 for the measurement results.

[0208] 3.2) Cycling performance test: At 45°C, maintain the battery charge and discharge voltage range between 1.5-3.9V, cycle at a current density of 1C, and record the capacity retention rate after 200 cycles. See Table 2 for the test results.

[0209] Table 2 Performance of Examples 1-18 and Comparative Examples 1-4

[0210] According to Comparative Examples 1 and 3, adding a sodium supplement to the battery can improve the cycle performance and coulombic efficiency of the battery to a certain extent.

[0211] According to Examples 1-16 and Comparative Examples 1-3, it is known that adding sodium supplement and adding a specific surface area of ​​not less than 600m2 in the battery 2 / g of the first conductive agent, the first conductive agent enables the sodium supplement agent to fully play its role, and can significantly improve the cycle performance and coulombic efficiency of the battery.

[0212] According to Examples 1-5, 7-8 and Comparative Examples 3-4, it is known that when a specific surface area of ​​600-1600 m 2 / g, especially 1200-1500m 2 / g of the first conductive agent is beneficial to improving the cycle performance and coulombic efficiency of the battery.

[0213] According to Examples 1, 6, and 7, the specific surface area is not less than 600 m 2 / g of various conductive agents can play the role of sodium supplement to improve the cycle performance and coulombic efficiency of the battery.

[0214] According to Examples 1 and 9, adding a second conductive agent to the battery is beneficial to further improve the coulombic efficiency of the battery.

[0215] According to Examples 1, 9-11, it can be seen that a variety of second conductive agents with good conductivity can assist the first conductive agent to further improve the cycle performance and coulombic efficiency of the battery.

[0216] According to Examples 1, 12-13, appropriately increasing the weight ratio of the first conductive agent to the second conductive agent, especially limiting the ratio of the first conductive agent to the second conductive agent to 4-9, is beneficial to further improving the cycle performance and coulombic efficiency of the battery.

[0217] According to Examples 1, 14-15, a variety of positive electrode active materials are applicable to the technical solution of this application.

[0218] According to Examples 1 and 16, various sodium supplements can improve the cycle performance and coulombic efficiency of the battery.

[0219] According to Examples 1 and 17-18, maintaining the weight of the sodium supplement in the range of 0.5-20 parts by weight, particularly 1-5 parts by weight, can enable the battery to have both good cycle performance and coulombic efficiency.

[0220] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, any implementation method having substantially the same structure as the technical concept and exerting the same effect is included in the technical scope of the present application. In addition, without departing from the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode sheet, characterized in that: include: 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, a sodium supplement agent, and a first conductive agent; Wherein, the specific surface area of ​​the first conductive agent is not less than 600m 2 / g.

2. The positive electrode sheet according to claim 1, characterized in that: The specific surface area of ​​the first conductive agent is 600-1600m 2 / g, optionally, the specific surface area of ​​the first conductive agent is 1200-1500m 2 / g.

3. The positive electrode sheet according to claim 2, characterized in that: The first conductive agent includes at least one of a chain-shaped conductive agent or a grape-shaped conductive agent; Optionally, the first conductive agent includes at least one of conductive carbon black and conductive graphite; Optionally, the conductive carbon black includes at least one of acetylene black and Ketjen black.

4. The positive electrode sheet according to claim 2 or 3, characterized in that: In the case where the first conductive agent includes conductive carbon black, the volume average particle size Dv50 of the first conductive agent is 20-60 nm. Optionally, the volume average particle size Dv50 of the first conductive agent is 30-50 nm.

5. The positive electrode sheet according to claim 3 or 4, characterized in that: In the case where the first conductive agent includes conductive graphite, the volume average particle size Dv50 of the first conductive agent is 3-4 μm. Optionally, the volume average particle size Dv50 of the first conductive agent is 3.2-3.6 μm.

6. The positive electrode sheet according to any one of claims 2 to 5, characterized in that: The positive electrode film layer also includes a second conductive agent, which includes at least one of carbon fiber, carbon nanotube, ordered mesoporous carbon, and graphene.

7. The positive electrode sheet according to claim 6, characterized in that: The second conductive agent satisfies at least one of the following conditions: (1) In the case where the second conductive agent includes the carbon nanotube, the carbon nanotube has a length of 0.5-30 μm, a diameter of 2-15 nm, and a specific surface area of ​​not less than 200 m 2 / g, optionally, the carbon nanotubes have a length of 0.5-10 μm, a diameter of 2-6 nm, and a specific surface area of ​​400-600 m 2 / g; (2) When the second conductive agent includes the ordered mesoporous carbon, the pore size of the ordered mesoporous carbon is 2-50 nm, and the specific surface area is 500-1500 m 2 / g, optionally, the ordered mesoporous carbon has a pore size of 3.2-6.6 nm and a specific surface area of ​​800-1300 m 2 / g; (3) When the second conductive agent includes the graphene, the graphene has a thickness of 0.6-4 nm and a sheet diameter of 0.5-5 μm. Optionally, the graphene has a thickness of 1.5-3.2 nm and a sheet diameter of 0.5-3 μm.

8. The positive electrode sheet according to claim 6 or 7, characterized in that: The mass ratio of the first conductive agent to the second conductive agent is 1-49. Optionally, the mass ratio of the first conductive agent to the second conductive agent is 4-9.

9. The positive electrode sheet according to any one of claims 6 to 8, characterized in that: Based on 100 parts by weight of the positive electrode film layer, the sum of the weight of the first conductive agent and the second conductive agent is 0.1-5 parts by weight. Optionally, the sum of the weight of the first conductive agent and the second conductive agent is 0.5-3 parts by weight.

10. The positive electrode sheet according to any one of claims 1 to 9, characterized in that: Based on 100 parts by weight of the positive electrode film layer, the weight of the sodium supplement is 0.5-20 parts by weight. Optionally, the weight of the sodium supplement is 1-5 parts by weight.

11. The positive electrode sheet according to any one of claims 1 to 10, characterized in that: The sodium supplement includes at least one of the following inorganic sodium supplements or organic sodium supplements, wherein the inorganic sodium supplement includes NaN3, Na2O2, Na2O, Na2CO3, NaNO2, NaBH4, NaNH2, Na2NiO2, NaCrO2, Na3P, and Na2S, and the organic sodium supplement includes CH3COONa, C7H6NNaO2, C 10 H 12 N2Na4O8、C 14 H 18 N3Na5O 10 、Na a C b H c O d , 1≤a≤2, 2≤b≤6, 0≤c≤2, 2≤d≤6, optionally, the sodium supplement includes Na2C2O4.

12. The positive electrode sheet according to any one of claims 1 to 11, characterized in that: The compaction density of the positive electrode sheet is 1.2-2.8 g / cm 3 Optionally, the compaction density of the positive electrode sheet is 1.6-2.3 g / cm 3 .

13. The positive electrode sheet according to any one of claims 1 to 12, characterized in that: The thickness of the positive electrode plate is 50-90 μm. Optionally, the thickness of the positive electrode plate is 65-80 μm.

14. The positive electrode sheet according to any one of claims 1 to 13, characterized in that: The coating weight of the positive electrode sheet is 3.5-35 mg / cm 2 Optionally, the coating weight of the positive electrode sheet is 10-25 mg / cm 2 .

15. The positive electrode sheet according to any one of claims 1 to 14, characterized in that: The positive electrode active material includes Na x R y (PO4) z (P2O7) k , wherein 1≤x≤7, 1≤y≤4, 1≤z≤2, 1≤k≤4, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb.

16. A battery cell, characterized in that: Comprising the positive electrode sheet as claimed in any one of claims 1 to 15.

17. The battery cell according to claim 16, characterized in that: The battery cell further comprises a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer comprises a conductive agent.

18. A battery, characterized in that: Comprising the battery cell as claimed in claim 16 or 17.

19. An electrical device, characterized in that: Comprising the battery of claim 18.

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