Battery cells, battery cell preparation methods, battery devices, and electrical devices.

Abstract

This application belongs to the field of battery technology, specifically disclosing a battery cell, a method for preparing the battery cell, a battery device, and an electrical device. The battery cell provided in this application includes a positive electrode sheet, which includes a positive electrode active material. The positive electrode active material includes a sulfur-carbon composite material, which includes a porous carbon material and a sulfur-containing active material supported on the porous carbon material. The sulfur-containing active material includes any one or more of elemental sulfur, sodium sulfide, or sodium polysulfide. The porous carbon material has micropores and mesopores, which are interconnected to form a tortuous pore structure. The negative electrode sheet includes a sodium metal sheet. The battery cell provided in this application improves battery capacity by reducing the loss of positive electrode active material during battery cycling.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a battery cell, a method for preparing the battery cell, a battery device, and an electrical device. Background Technology

[0002] With the development of new energy technologies, batteries are being used more and more widely, such as in mobile phones, laptops, electric vehicles, electric cars, energy storage devices, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. This places increasingly higher demands on battery performance. Summary of the Invention

[0003] In view of the above problems, this application provides a battery cell, a method for preparing the battery cell, a battery device, and an electrical device. The battery cell provided by this application improves battery capacity by reducing the loss of positive electrode active material during cycling.

[0004] In one aspect, this application provides a battery cell, including a negative electrode, a separator, and a positive electrode;

[0005] The aforementioned positive electrode includes a positive current collector and a positive electrode film layer located on at least one side surface of the aforementioned positive current collector;

[0006] The aforementioned positive electrode film includes a positive electrode active material;

[0007] The aforementioned positive electrode active material includes a sulfur-carbon composite material, which includes a porous carbon material and a sulfur-containing active material supported on the porous carbon material.

[0008] The aforementioned sulfur-containing active materials include any one or more of elemental sulfur, sodium sulfide, or sodium polysulfide;

[0009] The aforementioned porous carbon material possesses micropores and mesopores, with the micropores and mesopores interconnected to form a tortuous pore structure;

[0010] The aforementioned negative electrode includes a sodium metal sheet.

[0011] The porous carbon material of this application refers to a carbon material with a well-developed pore structure, a large specific surface area, and excellent electrical conductivity. This porous carbon material possesses both micropores and mesopores, which are interconnected to form a tortuous pore structure. Here, micropores refer to pores with a diameter less than 2 nm, and mesopores refer to pores with a diameter between 2 nm and 50 nm. Utilizing its own volume effect, this porous carbon material reduces the probability of sulfur-containing active materials generating intermediate products—polysulfides (highly soluble and readily reacting)—during battery cycling, and also reduces the probability of these intermediate products being eluted from the positive electrode reaction zone. By reducing the loss of positive electrode active material during battery cycling, it improves the specific capacity of the battery.

[0012] In some embodiments, the pore size of the micropores is less than 2 nm, and the pore size of the mesopores is 2 nm to 50 nm.

[0013] The average pore size of the above porous carbon materials is 1.6 nm to 2.0 nm.

[0014] The average pore size of the porous carbon material in this application is within the above-mentioned range to further reduce the probability of sulfur-containing active materials generating intermediate products—polysulfides (highly soluble and easily reacted) during battery cycling and to reduce the probability of intermediate products being eluted out of the positive electrode reaction zone.

[0015] In some embodiments, the specific surface area of ​​the porous carbon material is 700 m². 2 / g~1087m 2 / g;

[0016] The pore volume of the above porous carbon materials is 0.35 mL / g to 0.6 mL / g.

[0017] In addition to the above-mentioned average pore size, the porous carbon material of this application also has a specific surface area and pore volume within the above-mentioned numerical range, which is beneficial to further exert the volume effect of the porous carbon material and reduce the probability of intermediate products being eluted out of the positive electrode reaction zone.

[0018] In some embodiments, the porous carbon material comprises nitrides, including any one or more of cobalt nitride, iron nitride, nickel nitride, zinc nitride, and yttrium nitride.

[0019] This application selects non-metallic heteroatoms (nitrogen atoms) as dopants in porous carbon materials. This generates abundant defect sites on the porous carbon material, enhancing the attraction to the intermediate product—polysulfides—and promoting its transformation into sodium sulfide. This application also selects metal atoms, which primarily act as catalysts to promote the transformation of the intermediate product—polysulfides—into sodium sulfide.

[0020] In some embodiments, the sulfur-containing active material accounts for 20% to 80% of the total mass percentage of the sulfur-carbon composite material.

[0021] The sulfur-containing active material in this application, within the above-mentioned numerical range, is beneficial for directly improving the specific capacity of the battery.

[0022] In some embodiments, the compaction density of the above-mentioned positive electrode film is 1.40 g / cm³. 3 ~1.65g / cm 3 .

[0023] The compaction density of the positive electrode film layer in this application is within this range, which is beneficial for maximizing the capacity of the positive electrode active material.

[0024] In some embodiments, the positive electrode film layer includes a conductive agent, which includes one or more of carbon black, graphene, and carbon nanotubes.

[0025] The above-mentioned conductive agent has a mass percentage content of 10% to 20% in the positive electrode film layer.

[0026] The conductive agent of this application can exhibit good conductivity with a relatively small amount of usage, and indirectly increase the amount of active material used to improve the specific capacity of the battery.

[0027] In some embodiments, the specific surface area of ​​the carbon black is 100 m². 2 / g~500m 2 / g;

[0028] and / or;

[0029] The specific surface area of ​​the graphene mentioned above is 400 m². 2 / g~1000m 2 / g;

[0030] and / or;

[0031] The specific surface area of ​​the aforementioned carbon nanotubes is 300 m². 2 / g~1500m 2 / g.

[0032] In some embodiments, the battery cell includes an electrolyte, which includes an ether component;

[0033] The above-mentioned positive electrode film has a saturation absorption rate of 80% to 120% for the ether component.

[0034] In this application, the electrolyte is the carrier of ion transport in the battery, and plays the role of conducting ions between the positive and negative electrodes of the battery. The type of electrolyte affects the cycle stability of the battery.

[0035] The electrolyte in this application includes an ether component, which refers to an organic ether compound. This organic ether compound typically does not react with the sulfur-containing active material during battery cycling to form intermediate products—polysulfides. Simultaneously, the ether component reacts with the active material to form a solid electrolyte interface film that covers the surface of the sodium metal sheet at the negative electrode, further reducing the probability of side reactions. Therefore, the design method provided in this application also helps improve the cycle stability of the battery.

[0036] In some embodiments, the electrolyte includes an ionic liquid additive, wherein the cation of the ionic liquid additive comprises one or more of nitrogen-containing ions and phosphorus-containing ions, and the anion of the ionic liquid additive comprises one or more of halide ions, phosphate ions, borate ions, and sulfonylimide anions.

[0037] The ionic liquid additives in this application refer to salts added to the electrolyte in relatively small amounts, composed entirely of cations and anions, and which are liquid at or near room temperature, where room temperature is defined as 25°C ± 5°C. This application chooses to add ionic liquid additives to the electrolyte to further improve the stability of the solid electrolyte interface film formed on the sodium metal sheet surface, thereby improving the cycle stability of the battery.

[0038] In some embodiments, the thickness of the sodium metal sheet is 1 mm to 5 mm;

[0039] and / or;

[0040] At least one side of the sodium metal sheet is coated with a sodium bromide coating, the thickness of which is 2 μm to 12 μm.

[0041] In some embodiments, this application also discloses forming a sodium bromide coating on at least one side of the sodium metal sheet. Compared to the original sodium metal sheet, the formation of the sodium bromide coating reduces the interfacial ion transport activity of the negative electrode, that is, reduces the probability of side reactions, which is beneficial to improving the cycle stability of the battery.

[0042] In some embodiments, the aforementioned separator includes a base film and a coating located on at least one surface of the base film;

[0043] The above coatings include any one or more of organic coatings and inorganic coatings.

[0044] The separator of this application contains an inorganic or organic coating, which is beneficial to improving the interfacial adhesion between the separator and the sodium metal negative electrode sheet, thereby suppressing the growth of sodium dendrites and improving the cycle stability of the battery.

[0045] The second aspect of this application is to provide a method for preparing the battery cell described in the first aspect, comprising the following steps:

[0046] Preparation of sulfur-carbon composite material: Sulfur-containing active material is dissolved in a first solvent, and then porous carbon material is added. After thorough mixing, the mixture is heat-treated until the first solvent is completely evaporated to obtain a mixture. The mixture is then sintered in an inert atmosphere to obtain the sulfur-carbon composite material.

[0047] Preparation of positive electrode sheet: The sulfur-carbon composite material is dispersed in a second solvent to obtain an electrode slurry, and the electrode slurry is coated on the surface of the positive current collector to form a positive electrode film layer;

[0048] Battery cell preparation: Assemble the positive electrode, negative electrode and separator to form a battery cell.

[0049] In some embodiments, the sintering temperature is 150°C to 1200°C, and the time is 3 hours to 12 hours.

[0050] In some embodiments, the median particle size of the porous carbon material is 0.8 μm to 1.5 μm.

[0051] In some embodiments, the total mass of the sulfur-containing active material and the porous carbon material accounts for 10% to 100% of the mass of the first solvent.

[0052] In some embodiments, the first solvent includes one or more of ethanol, water, acetone, and tetrahydrofuran;

[0053] The second solvent mentioned above includes N-methylpyrrolidone.

[0054] A third aspect of this application is to provide a battery device comprising the battery cell described in the first aspect or the battery cell prepared by the preparation method described in the second aspect.

[0055] A fourth aspect of this application is to provide an electrical device, including the battery device described in the third aspect.

[0056] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0058] Figure 1 This is a schematic diagram of the battery structure of some embodiments of this application;

[0059] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0060] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0061] Figure 4 This is a schematic diagram of the battery pack structure according to some embodiments of this application;

[0062] Figure 5 This is a structural schematic diagram showing the positional relationship between the positive electrode, the separator, and the negative electrode in some embodiments of this application;

[0063] Figure 6This is a schematic diagram of the structure of the positive electrode sheet in some embodiments of this application;

[0064] Figure 7 , Figure 8 , Figure 9 , Figure 10 These are test diagrams of some embodiments and preparation examples of this application; wherein Figure 10 A is a scanning electron microscope image of the porous carbon material in the preparation example. Figure 10 B is a scanning electron microscope image of the sulfur-carbon composite material in the example.

[0065] The reference numerals in the detailed embodiments are as follows:

[0066] 10000, vehicles;

[0067] 1000, Battery; 2000, Controller; 3000, Motor;

[0068] 100. Battery cell;

[0069] 200. Box body; 210. First part; 220. Second part;

[0070] 10. Secondary batteries;

[0071] 101. Housing; 102. Electrode assembly; 103. Cover plate;

[0072] 1. Negative electrode sheet; 11. Negative electrode current collector; 12. Negative electrode active material layer;

[0073] 2. Positive electrode sheet; 21. Negative electrode current collector; 22. Positive electrode active material layer;

[0074] 3. Isolation components;

[0075] x-axis: direction of electrode stacking or thickness;

[0076] The y-axis represents the width or length of the electrode. Detailed Implementation

[0077] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, the method for preparing the battery cell, the battery device, and the power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0078] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is also expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0079] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0080] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0081] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0082] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0083] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0084] Unless otherwise specified, in this application, the terms "first," "second," etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0085] Unless otherwise specified, in this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more (including two sets), and "multiple pieces" means two or more (including two pieces).

[0086] Unless otherwise specified, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0087] Batteries, with their advantages of high energy density, long cycle life, and safety and reliability, have been widely used in various products. In recent years, with the significant increase in demand for batteries as an energy source, higher requirements have been placed on battery performance, such as energy density.

[0088] Based on the above considerations, in order to improve the energy density of the battery, this application conducted relevant experimental research and obtained a battery cell, a method for preparing the battery cell, a battery device, and an electrical device.

[0089] First, this application discloses a battery cell, which includes a negative electrode, a separator, and a positive electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a sulfur-carbon composite material, which includes a porous carbon material and a sulfur-containing active material supported on the porous carbon material. The sulfur-containing active material includes any one or more of elemental sulfur, sodium sulfide, or sodium polysulfide. The porous carbon material has micropores and mesopores, and the micropores and mesopores are interconnected to form a tortuous pore structure. The negative electrode includes a sodium metal sheet.

[0090] The battery cell provided in this application belongs to the sodium-sulfur battery. The positive electrode active material of the sodium-sulfur battery includes a porous carbon material loaded with sulfur-containing active material. The porous carbon material, by means of its own volume effect, reduces the probability of the sulfur-containing active material generating intermediate products—polysulfides (which are highly soluble in the electrolyte and easily react) during battery cycling. On the other hand, it reduces the probability of intermediate products being washed out of the positive electrode reaction zone. By reducing the loss of positive electrode active material during battery cycling, the battery capacity is improved.

[0091] Therefore, the battery cell provided in this application is beneficial to improving the user experience.

[0092] Electrode assembly

[0093] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0094] Battery device

[0095] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0096] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0097] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0098] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0099] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0100] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0101] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0102] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0103] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0104] The battery cell of this application may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte composed of the aforementioned battery cell. The outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of the battery cell can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, including but not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0105] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 10.

[0106] According to some embodiments of this application, reference is made to Figure 2 The outer packaging may include a housing 101 and a cover plate 103. The housing 101 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 101 has an opening communicating with the receiving cavity, and the cover plate 103 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 102 by a winding process or a stacking process. The electrode assembly 102 is encapsulated within the receiving cavity. The electrolyte is immersed in the electrode assembly 102. The secondary battery 10 may contain one or more electrode assemblies 102, which can be selected by those skilled in the art according to specific practical needs.

[0107] The electrode assembly 102 provided in this application is beneficial to improving the performance of a battery cell when applied in a battery cell. The battery cell can be used as a power source for an electrical device or as an energy storage unit for an electrical device. The electrical device is used in the power field, such as mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited to the above fields.

[0108] For ease of explanation, some embodiments of this application are illustrated using a vehicle as an example of an electrical device.

[0109] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 10000 provided in some embodiments of this application. The vehicle 10000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 1000 is disposed inside the vehicle 10000, and the battery 10000 can be located at the bottom, front, or rear of the vehicle 10000. The battery 10000 can be used to power the vehicle 10000; for example, the battery 10000 can serve as the operating power source for the vehicle 10000. The vehicle 10000 may also include a controller 2000 and a motor 3000. The controller 2000 is used to control the battery 10000 to supply power to the motor 3000, for example, to meet the power needs of the vehicle 10000 during startup, navigation, and driving.

[0110] In some embodiments of this application, the battery 1000 can not only serve as the operating power source for the vehicle 10000, but also as the driving power source for the vehicle 10000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 10000.

[0111] Please refer to Figure 4 , Figure 4 This is an exploded view of a battery 1000 provided in some embodiments of this application. The battery 1000 includes a housing 200 and a battery cell 100. A conventional battery cell includes a primary battery or a secondary battery. This application specifically protects a secondary battery 10. The battery cell 100 is housed within the housing 200. The housing 200 provides space for the battery cell 100, and the housing 200 can adopt various structures.

[0112] In some embodiments, the housing 200 may include a first portion 210 and a second portion 220, which overlap each other, and together define a receiving space for accommodating the battery cell 100. The second portion 220 may be a hollow structure with one open end, and the first portion 210 may be a plate-like structure, with the first portion 210 covering the open side of the second portion 220 so that the first portion 210 and the second portion 220 together define the receiving space; alternatively, the first portion 210 and the second portion 220 may both be hollow structures with one open side, with the open side of the first portion 210 covering the open side of the second portion 220. Of course, the housing 200 formed by the first portion 210 and the second portion 220 may be of various shapes, such as a cylinder, a cuboid, etc.

[0113] In battery 1000, there can be multiple battery cells 100, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 100 are connected in both series and parallel configurations. Multiple battery cells 100 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 100 is housed within housing 200. Alternatively, battery 1000 can also be composed of multiple battery cells 100 first connected in series, parallel, or in a mixed manner to form battery modules, and then these modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within housing 200. Battery 1000 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 100.

[0114] battery cell

[0115] This application discloses a battery cell in some embodiments, the battery cell including a negative electrode, a separator, and a positive electrode; the positive electrode includes a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector; the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a sulfur-carbon composite material, the sulfur-carbon composite material including a porous carbon material and a sulfur-containing active material supported on the porous carbon material; the sulfur-containing active material includes any one or more of elemental sulfur, sodium sulfide, or sodium polysulfide; the porous carbon material has micropores and mesopores, the micropores and the mesopores are interconnected and form a tortuous pore structure; the negative electrode includes a sodium metal sheet.

[0116] The battery cell in this application can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. The battery cell in this application is a sodium-sulfur battery. The high current, high power discharge, and low price of sodium-sulfur batteries give them unique advantages in the energy storage field. The working principle of a sodium-sulfur battery includes: during discharge, metallic sodium at the negative electrode is oxidized, producing sodium ions and electrons. Sodium ions migrate to the positive electrode through the internal electrolyte, and electrons migrate to the positive electrode through the external circuit, thereby generating current. At the same time, the sodium ions received at the positive electrode react with sulfur to form sodium sulfide (Na2S). During charging, the discharge products on the positive electrode side lose electrons and become elemental sulfur, while sodium ions return to the negative electrode through the electrolyte and are reduced to metallic sodium.

[0117] The current collector in this application refers to a structure or component that collects current, enabling it to gather the current generated by the battery's active materials to form a larger current output, while having sufficiently low internal resistance.

[0118] The positive electrode, separator, and negative electrode of this application can be formed into a single battery cell using winding or stacking processes. Specifically, this application... Figure 5 The diagram illustrates a stacking method used to form a single battery cell, combined with... Figure 5 It is known that a negative electrode 1 or a positive electrode 2 is placed between two adjacent separators 3, and the negative electrode 1 and the positive electrode 2 are alternately arranged along the stacking direction (coordinate axis x direction). The number and size of the negative electrode 1 and / or the positive electrode 2 can be selected according to the actual situation, and this application will not elaborate on them. Furthermore, this application... Figure 5 The image only illustrates one type of lamination method; other lamination or winding methods are within the scope of protection of this application.

[0119] like Figure 6 The diagram illustrates that the positive electrode 2 includes a positive current collector 21 and a positive electrode film 22 located on at least one side surface of the positive current collector 21. Figure 6 The diagram illustrates a positive electrode film 22 disposed on either side of the surface of the positive electrode current collector 21. The positive electrode film 22 may also be located on both sides of the positive electrode current collector 21. The formation of the positive electrode film 22 on the surface of the positive electrode current collector 21 can be any method conventional in the art, such as coating, deposition, etc.

[0120] The sulfur-carbon composite material of this application is a mixture, comprising porous carbon material and sulfur-containing active material loaded on the porous carbon material.

[0121] The porous carbon material of this application refers to a carbon material with a well-developed pore structure, a large specific surface area, and excellent electrical conductivity. This porous carbon material possesses both micropores and mesopores, which are interconnected to form a tortuous pore structure. Here, micropores refer to pores with a diameter less than 2 nm, and mesopores refer to pores with a diameter between 2 nm and 50 nm. Utilizing its own volume effect, this porous carbon material reduces the probability of sulfur-containing active materials generating intermediate products—polysulfides (highly soluble and readily reacting)—during battery cycling, and also reduces the probability of these intermediate products being eluted from the positive electrode reaction zone. By reducing the loss of positive electrode active material, it improves battery capacity.

[0122] The characterization method of sulfur-carbon composite materials at the level of battery cells in this application includes: disassembling the battery cells, obtaining the positive electrode film layer, and performing X-ray diffraction (XRD) analysis on the positive electrode film layer. Characterization can be performed based on the characteristic peaks of porous carbon materials and sulfur-containing active materials. Subsequent embodiments will describe this in detail.

[0123] This application further characterizes the pore structure of porous carbon materials, including calcining the positive electrode film sample at high temperature (>450℃) to remove sulfur from the sulfur-containing active material, leaving porous carbon. The porous carbon is then subjected to scanning electron microscopy (SEM) or transmission electron microscopy (TEM) to obtain its pore structure and pore size. Furthermore, when the sulfur-containing active material contains sodium sulfide or sodium polysulfide, since the discharge products include elemental sulfur, the positive electrode film is obtained after fully discharging the battery cell, and the pore structure of the porous carbon material is then characterized using the same method described above.

[0124] In addition to carbon, the porous carbon material of this application contains other non-metallic heteroatoms. Using these non-metallic heteroatoms as dopants in the porous carbon material generates abundant defect sites, which on the one hand enhances the attraction to the intermediate product—polysulfides—and on the other hand promotes the transformation of the intermediate product—polysulfides—into sodium sulfide. Therefore, it further reduces the loss of positive electrode active material to improve the specific capacity of the battery.

[0125] This application discloses in these embodiments that the aforementioned non-metallic heteroatoms include nitrogen atoms.

[0126] In addition to carbon and the aforementioned non-metallic heteroatoms, the porous carbon material of this application may also contain metal atoms. These metal atoms mainly act as catalysts to promote the conversion of intermediate products—polysulfides—into sodium sulfide, thereby further reducing the loss of positive electrode active material and improving battery capacity.

[0127] The detection methods for each element in the porous carbon material of this application include any conventional methods in the field, such as ICP testing (inductively coupled plasma atomic emission spectrometry). The testing method can be found in EPA 6010D-2014, and the testing instrument is an iCAP 7400 inductively coupled plasma atomic emission spectrometer.

[0128] The detection methods for sulfur-containing active materials in this application include any methods conventional in the art, such as X-ray diffraction analysis (XRD). For example, the X-ray diffraction analyzer used in this application has a Cu-Ka radiation source and a wavelength of [wavelength missing]. The operating voltage is 40kV, the scanning range is 10°~80°, and the scanning speed is 6° / min.

[0129] The methods for preparing porous carbon materials in this application include one or more of the following: template method, direct carbonization method, and activation method. The template method in this application involves generating porous carbon materials using template molecules. The direct carbonization method in this application refers to a high-temperature pyrolysis method. The activation method in this application includes physical activation and chemical activation methods.

[0130] The sulfur-containing active material in this application refers to a positive electrode active material containing sulfur, specifically including one or more of elemental sulfur, sodium sulfide, or sodium polysulfide.

[0131] The chemical formula of elemental sulfur in this application is S. In the subsequent embodiments of this application, commercial elemental sulfur is used as the reaction raw material.

[0132] The chemical formula of sodium sulfide in this application is Na2S. In the subsequent embodiments of this application, commercial sodium sulfide is used as the reaction raw material.

[0133] The chemical formula of the sodium polysulfide in this application is Na₂S. n , 2≤n≤4; the sodium polysulfide of this application can be a reaction raw material, or it can be generated by the reaction of elemental sulfur or sodium sulfide.

[0134] The reverse detection methods for the proportion of sulfur-containing active materials in this application include thermogravimetric analysis.

[0135] In summary, the battery cell provided in this application improves the specific capacity of the battery by reducing the loss of positive electrode active material.

[0136] In some embodiments, the pore size of the micropores is less than 2 nm, and the pore size of the mesopores is 2 nm to 50 nm.

[0137] The average pore size of the above porous carbon materials is 1.6 nm to 2.0 nm.

[0138] The average pore size of the porous carbon material in this application is within the above-mentioned range to further reduce the probability of sulfur-containing active materials generating intermediate products—polysulfides (highly soluble and easily reacted) during battery cycling and to reduce the probability of intermediate products being eluted out of the positive electrode reaction zone.

[0139] The method for determining the average pore size of porous carbon materials in this application includes any conventional method in the art, such as nitrogen adsorption-desorption analyzers and mercury porosimeter analyzers. Specifically, an ASAP2460 physical adsorption analyzer is used. The dried and degassed material sample is placed in liquid nitrogen, and the amount of nitrogen adsorbed is measured by adjusting different test pressures. Adsorption and desorption isotherms are then plotted. The pore shape is determined based on the shape of the hysteresis loop, and the pore distribution is calculated according to different pore models. The pore size distribution curve is fitted using the BJH model to obtain the average pore size.

[0140] In these embodiments, this application discloses that the average pore size of the porous carbon material is any one of 1.6 nm, 1.8 nm, 1.9 nm, 2.0 nm, or any one of the above two ranges.

[0141] In some embodiments, the specific surface area of ​​the porous carbon material is 700 m². 2 / g~1087m 2 / g;

[0142] The pore volume of the above porous carbon materials is 0.35 mL / g to 0.6 mL / g.

[0143] In addition to the above-mentioned average pore size, the porous carbon material of this application also has a specific surface area and pore volume within the above-mentioned numerical range, which is beneficial to further exert the volume effect of the porous carbon material and reduce the probability of intermediate products being eluted out of the positive electrode reaction zone.

[0144] The method for determining the specific surface area of ​​porous carbon materials in this application includes any conventional method in the art, such as the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2004, and the calculation of the specific surface area of ​​the porous carbon material using the BET (Brunauer Emmett Teller) method. The testing instrument can be a TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0145] This application discloses in these embodiments that the porous carbon material has a specific surface area of ​​700 m². 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g, 1000m2 / g, 1050m 2 / g、1087m 2 Any one of / g or any one of the ranges of the above two.

[0146] The method for determining the pore volume of porous carbon materials in this application includes any method conventional in the art, such as testing the pore volume of porous carbon materials according to GB / T21650.2-2008. The testing instrument can be a TRISTARII 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0147] In these embodiments, this application discloses that the pore volume of the porous carbon material is any one of 0.35 mL / g, 0.38 mL / g, 0.40 mL / g, 0.45 mL / g, 0.50 mL / g, 0.55 mL / g, 0.60 mL / g, or any one of the above two ranges.

[0148] In some embodiments, the porous carbon material comprises a nitride, which includes one or more of cobalt nitride, iron nitride, nickel nitride, zinc nitride, and yttrium nitride.

[0149] As described above, this application selects non-metallic heteroatoms as dopants for porous carbon materials, which can generate abundant defect sites on the porous carbon materials. On the one hand, this enhances the interaction force with the intermediate product—polysulfides; on the other hand, it can also promote the transformation of the intermediate product—polysulfides—into sodium sulfide. This application selects metal atoms, which mainly act as catalysts to promote the transformation of the intermediate product—polysulfides—into sodium sulfide.

[0150] This application provides examples of substances that simultaneously contain the aforementioned non-metallic heteroatoms and metallic atoms in some embodiments. The mass percentage content of this nitride in the porous carbon material is 0.01% to 0.1%. This content refers to the content during the preparation process; this application ignores losses during battery cycling.

[0151] The porous carbon material containing nitrides in this application is prepared by adding nitrogen-containing compounds and reacting them during the material preparation process.

[0152] In some embodiments, the mass percentage content of the sulfur-containing active material in the sulfur-carbon composite material is 20% to 80%.

[0153] The types of sulfur-containing active materials in this application can be characterized and determined using the above-mentioned X-ray diffraction (XRD) analysis. The content determination method includes any conventional method in the art, such as thermogravimetric analysis (TGA). The specific determination method includes: introducing nitrogen gas into the thermogravimetric analyzer, with a temperature range of 50℃ to 600℃ and a heating rate of 10℃ / min. The mass percentage content of elemental sulfur in the sulfur-carbon composite material can be calculated using the mass of sulfur lost.

[0154] The sulfur-containing active material in this application, within the above-mentioned numerical range, is beneficial for directly improving the specific capacity of the battery.

[0155] In these embodiments, this application discloses that the mass percentage content of the sulfur-containing active material in the above-mentioned sulfur-carbon composite material is any one of 20%, 30%, 40%, 50%, 60%, 70%, 80%, or any one of the above ranges.

[0156] In some embodiments, the compaction density of the above-mentioned positive electrode film is 1.40 g / cm³. 3 ~1.65g / cm 3 .

[0157] The compaction density of the positive electrode film layer in this application can be used to characterize the energy density of the material. The compaction density of the positive electrode film layer = the areal density of the positive electrode film layer / the thickness of the positive electrode film layer. The thickness of the positive electrode film layer includes the distance between the two end faces of the positive electrode film layer along the thickness direction. The areal density of the positive electrode film layer = the weight of a single-sided positive electrode film layer / the area of ​​a single-sided positive electrode film layer. The weight of a single-sided positive electrode film layer can be obtained by weighing, and the area of ​​a single-sided positive electrode film layer can be obtained by using the area calculation formula according to the shape of the film layer. The test method for the compaction density of the positive electrode film layer is given in the test method of the following specific embodiments of this application, and will not be repeated here.

[0158] The compaction density of the positive electrode film layer in this application is within this range, which is beneficial for maximizing the capacity of the positive electrode active material.

[0159] In these embodiments, this application discloses that the compaction density of the above-mentioned positive electrode film is 1.40 g / cm³. 3 1.41 g / cm 3 1.42g / cm 3 1.43 g / cm 3 1.44 g / cm 3 1.45g / cm 3 1.46 g / cm 3 1.47 g / cm 3 1.48g / cm 3 1.49 g / cm 3 1.50g / cm3 1.51g / cm 3 1.52g / cm 3 1.53g / cm 3 1.54g / cm 3 1.55g / cm 3 1.56g / cm 3 1.57g / cm 3 1.58g / cm 3 1.59g / cm 3 1.60g / cm 3 1.61 g / cm 3 1.62g / cm 3 1.63g / cm 3 1.64 g / cm 3 1.65g / cm 3 It can be any one of the above or any one of the range values ​​of any two of the above.

[0160] In some embodiments, the positive electrode film layer includes a conductive agent, which includes one or more of carbon black, graphene, and carbon nanotubes.

[0161] The conductive agent has a mass percentage content of 10% to 20% in the positive electrode film. The conductive agent in this application refers to a substance with conductivity that plays a role in collecting microcurrents between positive electrode active materials and between positive electrode active materials and positive electrode current collectors, thereby reducing the contact resistance of the electrodes and accelerating the movement rate of electrons.

[0162] The carbon black in this application refers to an industrial product whose main component is elemental carbon, and contains small amounts of oxygen, hydrogen and sulfur.

[0163] The graphene in this application refers to graphene made from sp 2 A planar sheet, one atom thick, composed of bonded carbon atoms, where the carbon atoms are tightly stacked in a honeycomb lattice.

[0164] The carbon nanotubes of this application refer to carbon allotropes, which include cylindrical layers of one or more carbon atoms, wherein the carbon atoms are covalently bonded to form a hexagonal tiling pattern (i.e., graphene sheet), which forms a hollow tube structure with a diameter of up to several hundred nanometers.

[0165] The carbon nanotubes of this application have good electron mobility and mainly function as conductive agents in the positive electrode film.

[0166] The carbon nanotubes in this application include any one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0167] The single-walled carbon nanotubes of this application refer to a single cylindrical layer of carbon atoms, while the multi-walled carbon nanotubes of this application refer to two or more layers of carbon atoms connected by intermolecular forces, or a single layer of carbon atoms that is rolled around a hollow cylindrical core several times.

[0168] The carbon nanotubes of this application may be substituted with functional groups or other defects, depending on their production and purification methods, particularly at the ends of the tubes. For example, carbon nanotubes may include oxygen, sulfur, nitrogen, fluorine, or other substituent atoms, and may include, for example, carbonyl, hydroxyl, thiol, amine, and / or amide functional groups. Amorphous carbon and residual catalysts, such as iron or nickel, may also be present, among other impurities. Exemplary carbon nanotube synthesis processes include arc discharge, laser ablation, chemical vapor deposition (CVD), and high-pressure carbon monoxide dismutation (HiPCO). Some common post-synthesis treatments or modifications of carbon nanotubes include ozone treatment, ozone and hydrogen peroxide treatment, hydrochloric acid treatment, sodium hydroxide / potassium hydroxide treatment, and / or thermal treatment.

[0169] The carbon nanotubes of this application can be characterized using various techniques available in the art. For example, X-ray photoelectron spectroscopy (XPS) can be used to measure the content of nitrogen, oxygen, sulfur, or fluorine / halogen, and can indicate the level of impurities and functionalization. Raman spectroscopy can be used to indicate the purity level of the graphene sheets that make up the carbon nanotubes, i.e., their cleanliness. BET measurements can be used to measure the surface area of ​​the carbon nanotubes, and these measurements are affected by the properties of the carbon nanotube structure (e.g., single-walled versus multi-walled nanotubes) and the functionalization and defects of the nanotube structure, which may modify the measured values ​​relative to theoretical values. Finally, scanning electron microscopy can also be used to analyze the surface of the carbon nanotubes, as well as the shape and size of the particles.

[0170] In some embodiments, this application discloses conductive agents including carbon black, graphene, and carbon nanotubes. Carbon black is mainly used as a dot-shaped conductive agent, graphene as a sheet-like conductive agent, and carbon nanotubes as a one-dimensional tubular conductive agent. This facilitates the formation of a conductive network with a dot-line-plane structure, thereby improving the conductivity of the conductive agent. Therefore, the conductive agent of this application can exhibit good conductivity with relatively small usage amounts, and indirectly increases the amount of active material used to improve the specific capacity of the battery.

[0171] In these embodiments, this application discloses that the mass percentage content of the conductive agent in the positive electrode film layer is any one of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any one of the ranges of both above.

[0172] In some embodiments, the specific surface area of ​​the carbon black is 100 m². 2 / g~500m 2 / g;

[0173] In some embodiments, the specific surface area of ​​the graphene described above is 400 m². 2 / g~1000m 2 / g;

[0174] In some embodiments, the specific surface area of ​​the carbon nanotubes is 300 m². 2 / g~1500m 2 / g.

[0175] The definition and measurement method of the specific surface area of ​​various types of conductive agents in this application are the same as those described above, and will not be repeated here.

[0176] This application selects carbon black that meets the above-mentioned specific surface area, which is beneficial for the carbon black to be well coated on the surface of the positive electrode active material so as to exert good conductivity.

[0177] In these embodiments, this application discloses that the specific surface area of ​​the carbon black is 100 m². 2 / g, 150m 2 / g、200m 2 / g、250m 2 / g、300m 2 / g, 350m 2 / g、400m 2 / g、450m 2 / g、500m 2 Any one of / g or any one of the ranges of the above two.

[0178] The specific surface area of ​​the graphene in this application meets the above-mentioned numerical range, which is beneficial to the conductivity of sheet graphene.

[0179] This application discloses in these embodiments that the specific surface area of ​​graphene is 400 m². 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g, 1000m 2 Any one of / g or any one of the ranges of the above two.

[0180] The specific surface area of ​​the carbon nanotubes in this application meets the above-mentioned numerical range, which is beneficial to the conductivity of the one-dimensional tubular carbon nanotubes.

[0181] This application discloses in these embodiments that the specific surface area of ​​carbon nanotubes is 300 m². 2 / g, 350m 2 / g、400m 2 / g、450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g, 1000m 2 / g, 1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g, 1350m 2 / g, 1400m 2 / g, 1450m 2 / g, 1500m 2 Any one of / g or any one of the ranges of the above two.

[0182] In some embodiments, the battery cell described above includes an electrolyte, which includes an ether component;

[0183] The positive electrode film has a saturation absorption rate of 80% to 120% for the above-mentioned ether components.

[0184] In this application, the electrolyte is the carrier of ion transport in the battery, and plays the role of conducting ions between the positive and negative electrodes of the battery. The type of electrolyte affects the cycle stability of the battery.

[0185] The electrolyte in this application includes an ether component, which refers to an organic ether compound. This organic ether compound typically does not react with the sulfur-containing active material during battery cycling to form intermediate products—polysulfides. Simultaneously, the ether component reacts with the active material to form a solid electrolyte interface film that covers the surface of the sodium metal sheet at the negative electrode, further reducing the probability of side reactions. Therefore, the design method provided in this application also helps improve the cycle stability of the battery.

[0186] The ether components of this application include any type conventional in the art, such as one or more of chain ethers and cyclic ethers. Chain ethers refer to ether compounds containing chain-like alkanes, a certain number of carbon atoms, and a certain chain length. Cyclic ethers of this application refer to ether compounds containing a certain number of carbon atoms and a ring structure formed by the combination of the first and last atoms, such as ether compounds with three or more membered rings. This application further selects chain ethers including one or more of ethylene glycol dimethyl ether (DME), dimethoxymethane (DMM), 1,2-dimethoxypropane (DMP), and triethylene glycol dimethyl ether (DG). Cyclic ethers include one or more of 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane (4MeDOL), tetrahydrofuran (THF), and 2-methyltetrahydrofuran (2MeTIF).

[0187] The positive electrode active material of this application, as described above, contains a porous structure, enabling the positive electrode film layer to possess a certain liquid absorption capacity for ether components. The saturation absorbance rate of this application refers to the maximum absorption capacity of the positive electrode film layer for ether components, primarily used to reflect the wettability of the positive electrode film layer for ether components. Specific measurement methods are detailed below.

[0188] The positive electrode film layer of this application has the above-mentioned saturated liquid absorption rate for ether components, so that the ether components are fully wetted inside and outside the positive electrode active material.

[0189] In some embodiments, the electrolyte includes an ionic liquid additive, wherein the cation of the ionic liquid additive comprises one or more of nitrogen-containing ions and phosphorus-containing ions, and the anion of the ionic liquid additive comprises one or more of halide ions, phosphate ions, borate ions, and sulfonylimide anions.

[0190] The ionic liquid additives in this application refer to salts added to the electrolyte in relatively small amounts, composed entirely of cations and anions, and which are liquid at or near room temperature, where room temperature is defined as 25°C ± 5°C. This application chooses to add ionic liquid additives to the electrolyte to further improve the stability of the solid electrolyte interface film formed on the sodium metal sheet surface, thereby improving the cycle stability of the battery.

[0191] In some embodiments, the thickness of the sodium metal sheet is 1 mm to 5 mm;

[0192] In some embodiments, at least one side surface of the sodium metal sheet is formed with a sodium bromide coating, the thickness of which is 2 μm to 12 μm.

[0193] The thickness in this application refers to the distance between two opposing surfaces along the stacking direction of each component of the battery cell.

[0194] In these embodiments, this application discloses that the thickness of the sodium metal sheet is any one of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or any one of the above two ranges.

[0195] In some embodiments, this application also discloses forming a sodium bromide coating on at least one side of the sodium metal sheet. Compared to the original sodium metal sheet, the formation of the sodium bromide coating reduces the interfacial ion transport activity of the negative electrode, that is, reduces the probability of side reactions, which is beneficial to improving the cycle stability of the battery.

[0196] In these embodiments, this application discloses that the thickness of the sodium bromide coating is any one of 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm or any one of the above ranges.

[0197] In some embodiments, the aforementioned separator includes a base film and a coating located on at least one side surface of the base film;

[0198] The coating includes one or more of inorganic and organic coatings.

[0199] The isolation element in this application refers to a structural element located between the positive electrode and the negative electrode, which isolates the positive and negative electrodes to prevent internal short circuits, but allows ions to pass through.

[0200] The separator of this application contains an inorganic or organic coating, which is beneficial to improving the interfacial adhesion between the separator and the sodium metal negative electrode sheet, thereby suppressing the growth of sodium dendrites and improving the cycle stability of the battery.

[0201] Preparation method of battery cell

[0202] According to some embodiments of this application, the preparation process of a single battery cell is as follows:

[0203] Preparation of sulfur-carbon composite material: Sulfur-containing active material is dissolved in a first solvent, and then porous carbon material is added. After thorough mixing, the mixture is heat-treated until the first solvent is completely evaporated to obtain a mixture. The mixture is then sintered in an inert atmosphere to obtain the sulfur-carbon composite material.

[0204] Preparation of positive electrode sheet: The sulfur-carbon composite material is dispersed in a second solvent to obtain an electrode slurry, and the electrode slurry is coated on the surface of the positive current collector to form a positive electrode film layer;

[0205] Battery cell preparation: Assemble the positive electrode, negative electrode and separator to form a battery cell.

[0206] In some embodiments, the sintering temperature is 150°C to 1200°C and the sintering time is 3h to 12h.

[0207] The sintering temperature range of this application is wide because the sulfur-containing active materials each possess different properties. For example, in some embodiments of this application, the sulfur-containing active material contains elemental sulfur, and the sintering temperature is 150°C to 300°C. In other embodiments, the sulfur-containing active material contains sodium sulfide, and the sintering temperature is 850°C to 1200°C. In some embodiments, the median particle size of the above-mentioned porous carbon material is 0.8 μm to 1.5 μm.

[0208] The median particle size of the porous carbon material affects its pore volume or specific surface area. In these embodiments, this application discloses that the median particle size of the porous carbon material is any one of 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, and 1.5 μm, or any one of the above two ranges.

[0209] In some embodiments, the total mass of the sulfur-containing active material and the porous carbon material accounts for 10% to 100% of the mass of the first solvent.

[0210] To ensure thorough mixing of the sulfur-containing active material and the porous carbon material, this application employs a first solvent method. In these embodiments, this application discloses that the total mass of the sulfur-containing active material and the porous carbon material accounts for any one of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% of the mass of the first solvent, or any one of the above two ranges.

[0211] In some embodiments, the first solvent mentioned above includes any one or more of ethanol, water, acetone, and tetrahydrofuran;

[0212] The second solvent mentioned above includes N-methylpyrrolidone.

[0213] This application discloses, in some embodiments, a method for preparing sulfur-carbon composite materials from elemental sulfur and porous carbon materials, including the following preparation process:

[0214] Elemental sulfur (Dv50 = 4.6 μm) was dissolved in ethanol solvent, and porous carbon material was added to form mixture A1. Elemental sulfur / (elemental sulfur + porous carbon) = 20 wt%–80 wt%, (elemental sulfur + porous carbon) / ethanol solvent = 10 wt%–100 wt%. The prepared mixture A1 was heated and magnetically stirred until the solvent was completely evaporated, or magnetically stirred at room temperature for 5–10 hours, and then placed in a drying oven for high-temperature drying to obtain dried mixture B1. Mixture B1 was calcined at a temperature of 150℃–300℃ for 3–12 hours with argon gas purging throughout, and then allowed to cool naturally to obtain sulfur-carbon composite material C1.

[0215] This application discloses, in some embodiments, a method for preparing a sulfur-carbon composite material from sodium sulfide and porous carbon materials, including the following preparation process:

[0216] Commercial sodium sulfide (Dv50 = 9.5 μm) was dissolved in ethanol solvent, and porous carbon material was added to form mixture A2. Sodium sulfide / (sodium sulfide + porous carbon) = 20 wt%–80 wt%, (sodium sulfide + porous carbon) / ethanol solvent = 10 wt%–100 wt%. The prepared mixture A2 was heated and magnetically stirred until the solvent was completely evaporated, or magnetically stirred at room temperature for 5 to 10 hours, and then placed in a drying oven for high-temperature drying to obtain dried mixture B2. Mixture B2 was calcined at high temperature of 850℃–1200℃ for 3 to 12 hours with argon gas purging throughout, and then allowed to cool naturally to obtain sulfur-carbon composite material C2.

[0217] [Positive electrode plate]

[0218] According to some embodiments of this application, as described above, the positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector. The positive electrode film layer contains a positive electrode active material.

[0219] In some embodiments of this application, the positive electrode active material is as described above, and will not be repeated here.

[0220] According to some embodiments of this application, the positive electrode film layer also includes a conductive agent, a binder, etc. The conductive agent is as described above. The binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The positive electrode current collector in this application can be a metal foil or a composite current collector. The metal foil can be an aluminum foil, and 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. Composite current collectors can be formed by forming metallic materials, such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, on polymer substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0221] The method of forming the positive electrode film layer in this application includes mixing the above-mentioned raw materials with a solvent (such as N-methylpyrrolidone) in a certain mass ratio to form a positive electrode slurry, uniformly coating the positive electrode slurry on both sides of the current collector, controlling the coating weight on one side, and after drying, compacting it to a certain compaction density using a cold press to obtain a positive electrode sheet containing the positive electrode film layer.

[0222] [Isolation Component]

[0223] Some embodiments of this application disclose isolation elements. This application does not have any particular restrictions on the type of isolation element, and any known porous structure isolation element with good chemical and mechanical stability can be selected.

[0224] In some embodiments, the separator includes a substrate material layer and a coating disposed on the surface of the substrate material layer; the substrate material of the substrate material layer includes one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide; the coating includes an inorganic coating and / or an organic coating. The substrate material layer has good permeability to sodium ions, which is beneficial to the migration of sodium ions; the coating disposed on the surface of the substrate material layer can further improve the mechanical properties of the separator, and the coating can also increase the interfacial adhesion between the separator and the negative electrode. Further, the inorganic coating includes a ceramic coating, wherein the ceramic particles in the ceramic coating include one or more of SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2, and BaSO4.

[0225] In some embodiments, the organic coating includes a polymer coating, the polymer material of which includes one or more of polyethylene (PE), polypropylene (PP), poly(p-phenylene terephthalamide) (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI), and polyamide (PA). The polymer coating may be made of the same or different material as the substrate material layer, and the thicknesses of the polymer coating and the substrate material layer may be different; furthermore, the thickness of the polymer coating is less than the thickness of the substrate material layer.

[0226] In other embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0227] [Electrolytes]

[0228] Electrolytes are disclosed in some embodiments of this application. The electrolyte in this application can be liquid, solid, or gel-like. Solid state refers to a solid electrolyte, liquid state to a liquid electrolyte, and gel-like state to a gel electrolyte. The sodium-ion battery in this application uses a liquid electrolyte, i.e., an electrolyte solution. This electrolyte solution contains an electrolyte salt and an organic solvent. The electrolyte salt can be any type conventional in the art, including, but not limited to, inorganic metal salts such as RClO4, RAsF6, RPF6, RBF4, RSbF6, RSO3F, RN(FSO2)2, etc.; fluorinated organometallic salts such as RCF3SO3, RN(FSO2)(CF3SO2), RN(CF3SO2)2, RN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonyl imide sodium, cyclic 1,2-tetrafluoroethane disulfonyl imide sodium, RN(CF3SO2)(C4F9S O2), RC(CF3SO2)3, RPF4(CF3)2, RPF4(C2F5)2, RPF4(CF3SO2)2, RPF4(C2F5SO2)2, RBF2(CF3)2, RBF2(C2F5)2, RBF2(CF3SO2)2, RBF2(C2F5SO2)2, etc.; and metal salts containing dicarboxylic acid complexes, such as sodium bis(oxalate)borate, sodium difluorooxalate borate, sodium tri(oxalate)phosphate, sodium difluorobis(oxalate)phosphate, sodium tetrafluoro(oxalate)phosphate, etc. Here, both the metal and R contain sodium ions.

[0229] According to some embodiments of this application, the concentration of the electrolyte salt in the electrolyte is 0.1 mol / L to 4 mol / L. In these embodiments, this application discloses that the concentration of the electrolyte salt is any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the above ranges.

[0230] As mentioned above, organic solvents include ether components, which will not be elaborated upon here.

[0231] According to some embodiments of this application, the electrolyte further comprises a film-forming stabilizer, which includes a negative electrode film-forming stabilizer. The negative electrode film-forming stabilizer comprises one or more of sodium boron salts, phosphorus-containing sodium salts, and sulfur-containing sodium salts. The sodium boron salts include one or more of sodium tetrafluoroborate (NaBF4), sodium bis(oxalate-borate)borate (NaBOB), and sodium bis(oxalate-borate)borate (NaDFOB). The sodium phosphorus salts include one or more of sodium difluorophosphate (NaPO2F2), sodium fluorophosphate (Na2PO3F), and sodium phosphate (Na3PO4). The sulfur-containing sodium salts include one or more of sodium fluorosulfonate (NaFSO3), sodium sulfate (Na2SO4), and sodium aminosulfonate (NaSO3NH2).

[0232] In some embodiments, the electrolyte further includes an ionic liquid additive, wherein the cation of the ionic liquid additive comprises any one or more of nitrogen-containing ions and phosphorus-containing ions, and the anion of the ionic liquid additive comprises any one or more of halide ions, phosphate ions, borate ions, and sulfonamide anions.

[0233] In this application, the electrolyte serves as the carrier for ion transport in the battery, acting as a conductor between the positive and negative electrodes. The type of electrolyte affects battery safety. Ionic liquid additives refer to salts added to the electrolyte in relatively small amounts, composed entirely of cations and anions, and existing in a liquid state at or near room temperature (25℃ ± 5℃). Ionic liquid additives possess high thermal stability and low volatility. Furthermore, they can improve the stability of the negative electrode by forming a solid electrolyte interphase (SEI) film and enhancing its stability, thereby improving the battery's cycle stability.

[0234] In some embodiments, the cation of the ionic liquid additive comprises 1-butyl-3-methylimidazolium ([Bmin]). + ), 1-benzyl-3-methylimidazolium ([Bzmin)) + ), 3-methyl-1-ethoxycarbonylmethylimidazolium ([Etmim) + ), 1-alkyl-3-methylimidazolium ([Cnmim) + ), 1-[(trimethylsilyl)methyl]benzotriazineonium ([SiMBIM) + N-alkyl-N-methylpiperidinium ([CnC1pip)) + ), 5-aza-onium-spiro[4.4]nonane([AS[mn]) + ), trihexyl(tetradecyl)phosphine ion ([Tf₂N) + ), tetrabutylphosphine ion ([Pnnnn) + ), n-Butyl-N-methylpyrrolidone ([Pyr14 ] + One or more of the following, optionally tetrabutylphosphine ion or n-butyl-N-methylpyrrolidineonium.

[0235] In some embodiments, the anion of the ionic liquid additive includes chloride ions ([Cl-)). - ), bromide ions ([Br]) - ), iodide ions ([I) - ), hexafluorophosphate ([PF6]) - Tetrafluoroborate ([BF4]) - ), dicyandiamide anion ([N(CN)2)) - ), bis(fluorosulfonyl)imine anion ([FSI) - ), bis(trifluoromethanesulfonyl)imide ([TFSI) - One or more of the following, selected as hexafluorophosphate or bis(fluorosulfonyl)imine anions.

[0236] In some embodiments, the ionic liquid additive includes one or more of tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imine, n-butyl-N-methylpyrrolidine hexafluorophosphate, n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imine, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imine, 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imine, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imine, and 1-benzyl-3-methylimidazolium bis(fluorosulfonyl)imine, optionally tetrabutylphosphine hexafluorophosphate, tetrabutylphosphine bis(fluorosulfonyl)imine, n-butyl-N-methylpyrrolidine hexafluorophosphate, and n-butyl-N-methylpyrrolidine bis(fluorosulfonyl)imine.

[0237] In some embodiments, the ionic liquid additive has a mass percentage content of 0.005% to 0.01% in the organic solvent.

[0238] The secondary battery of this application will be described in detail below with reference to specific embodiments.

[0239] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0240] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0241] This application may employ conventional inorganic chemistry techniques within the art. In the following examples, efforts have been made to ensure the accuracy of the figures used (including quantities, temperatures, reaction times, etc.), but some experimental errors and biases should be considered. Temperatures (in degrees Celsius) used in the following examples are expressed in °C, and pressures are at or near atmospheric pressure. All reagents were purchased from AR-grade suppliers, and all reactions were carried out under argon protection. Unless otherwise stated, all reagents were obtained commercially.

[0242] Experimental materials:

[0243] Elemental sulfur, sodium sulfide, porous carbon materials: commercially available.

[0244] Preparation Example 1

[0245] A method for preparing a sulfur-carbon composite material is provided, comprising the following preparation process:

[0246] Elemental sulfur (Dv50 = 4.6 μm) was dissolved in ethanol solvent, and porous carbon material (as shown in Table 1-1) was added to form mixture A1. Elemental sulfur / (elemental sulfur + porous carbon) = 40 wt%, (elemental sulfur + porous carbon) / ethanol solvent = 20 wt%. The prepared mixture A1 was magnetically stirred at room temperature for 5-10 hours, then dried in a drying oven at high temperature to obtain dried mixture B1. Mixture B1 was calcined at 155℃ for 6 hours, followed by a holding time at 200℃ for 30 minutes, with argon gas purging throughout. After calcination, the mixture was allowed to cool naturally to obtain sulfur-carbon composite material C1-1.

[0247] Preparation Example 2

[0248] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation example 1 above in that the porous carbon material is different (as shown in Table 1-1, 1-2). All other aspects are the same as in preparation example 1, and the sulfur-carbon composite material C1-2 is obtained.

[0249] Preparation Example 3

[0250] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation example 1 above in that the porous carbon material is different (as shown in Table 1-1, 1-3). Otherwise, the method is the same as the preparation example 1, and the sulfur-carbon composite material C1-3 is obtained.

[0251] Preparation Example 4

[0252] A method for preparing a sulfur-carbon composite material is provided. The method differs from the preparation example 1 above in that the porous carbon material contains cobalt nitride (as shown in Table 1-1, 1-4), and the mass percentage content of cobalt nitride is 0.05%. All other aspects are the same as in preparation example 1, and the sulfur-carbon composite material C1-4 is obtained.

[0253] Preparation Example 5-1

[0254] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation example 1 described above in that the mass percentage content of elemental sulfur in the sulfur-carbon composite material is 20%. The specific preparation process is as follows:

[0255] Elemental sulfur (Dv50 = 4.6 μm) was dissolved in ethanol solvent, and porous carbon material (as shown in Table 1-1) was added to form mixture A1. Elemental sulfur / (elemental sulfur + porous carbon) = 20 wt%, (elemental sulfur + porous carbon) / ethanol solvent = 20 wt%. The prepared mixture A1 was magnetically stirred at room temperature for 5-10 hours, then dried in a drying oven at high temperature to obtain dried mixture B1. Mixture B1 was calcined at 150℃ for 6 hours, followed by a 30-minute holding at 180℃, with argon gas purging throughout. After calcination, the mixture was allowed to cool naturally to obtain sulfur-carbon composite material C1-5-1.

[0256] Preparation Example 5-2

[0257] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation example 1 described above in that the mass percentage content of elemental sulfur in the sulfur-carbon composite material is 60%. The specific preparation process is as follows:

[0258] Elemental sulfur (Dv50 = 4.6 μm) was dissolved in ethanol solvent, and carbon materials (as shown in Table 1-1) were added to form mixture A1. Elemental sulfur / (elemental sulfur + porous carbon) = 60 wt%, (elemental sulfur + porous carbon) / ethanol solvent = 20 wt%. The prepared mixture A1 was magnetically stirred at room temperature for 5-10 hours, then dried in a drying oven at high temperature to obtain dried mixture B1. Mixture B1 was calcined at 180℃ for 6 hours, followed by a holding time at 300℃ for 30 minutes, with argon gas purging throughout. After calcination, the mixture was allowed to cool naturally to obtain sulfur-carbon composite material C1-5-2.

[0259] Preparation Example 6-1

[0260] A method for preparing a sulfur-carbon composite material is provided, the method comprising the following steps:

[0261] Commercial sodium sulfide (Dv50 = 9.5 μm) was dissolved in ethanol, and porous carbon material (same as in Preparation Example 1, 1-1 in Table 1-1) was added to form mixture A2. Sodium sulfide / (sodium sulfide + porous carbon) = 40 wt%, (sodium sulfide + porous carbon) / ethanol solvent = 20 wt%. The prepared mixture A2 was heated and magnetically stirred until the solvent was completely evaporated, resulting in a dry mixture B2. Mixture B2 was then calcined at a high temperature of 1000 °C for 6 hours under argon gas purging throughout, followed by natural cooling to obtain the sulfur-carbon composite material C2.

[0262] Comparative Preparation Example 1

[0263] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation method described in Example 1 above in that the porous carbon material is different (as shown in Table 1-1, 1-5), while all other aspects remain the same as in Example 1.

[0264] Comparative Preparation Example 2

[0265] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation method described in Example 1 above in that the porous carbon material is different (as shown in Table 1-1, 1-6). Otherwise, the method remains the same as that in Example 1.

[0266] Comparative preparation example 3

[0267] A method for preparing a sulfur-carbon composite material is provided. This method differs from the preparation example 6-1 above in that the porous carbon material is different (same as the comparative preparation example 1, 1-5 in Table 1-1), while all other aspects are the same as the preparation example 6-1.

[0268] Table 1-1 Performance List of Porous Carbon Materials

[0269]

[0270] Table 1-2 Performance List of Sulfur-Carbon Composite Materials

[0271] Serial Number sulfur-containing active materials (mass percentage content) Preparation Example 1 40 Preparation Example 2 40 Preparation Example 3 40 Preparation Example 4 40 Preparation Example 5-1 20 Preparation Example 5-2 60 Preparation Example 6-1 40 Comparative Preparation Example 1 40 Comparative Preparation Example 2 40 Comparative preparation example 3 40

[0272] To further verify the adhesion of sulfur-containing active materials to porous carbon materials, this application employs X-ray diffraction (XRD) analysis. The specific testing method includes: the X-ray source of the X-ray diffractometer is Cu-Ka, and the wavelength is [wavelength missing]. The operating voltage was 40 kV, the scanning range was 10°–80°, and the scan rate was 6° / min. XRD patterns of elemental sulfur, porous carbon materials (shown in Table 1-1), the sulfur-carbon composite material prepared in Preparation Example 1, and the sulfur-carbon composite material prepared in Preparation Example 5-2 were obtained, as shown below. Figure 7 Indication, combined Figure 7 It can be seen that by comparing the characteristic peaks of porous carbon and the sulfur-carbon composite material of Preparation Example 1, the peak positions of the two are not significantly different, and there are no additional characteristic peaks of elemental sulfur. Further comparison of the characteristic peaks of the sulfur-carbon composite material obtained in Preparation Example 5-2 with those of Preparation Example 1 clearly shows that Preparation Example 5-2 has more characteristic peaks of elemental sulfur. It can be inferred that in the sulfur-carbon composite material obtained in Preparation Example 5-2, some elemental sulfur adheres to the outside of the pores of the porous carbon and is thus detected, while the elemental sulfur inside the porous carbon is not detected.

[0273] This application also describes the preparation of commercial sodium sulfide in Example 6-1 and the resulting sulfur-carbon composite material by XRD, yielding... Figure 8 , combined Figure 8 It is known that sodium sulfide can partially adhere to the pores of porous carbon, but due to the large size of sodium sulfide particles, the amount of sodium sulfide adhering to the pores of porous carbon materials is limited.

[0274] This application further describes thermogravimetric analysis (TGA) of the sulfur-carbon composite material prepared in Example 1. The specific steps include: introducing nitrogen gas into a thermogravimetric analyzer at a temperature range of 50°C to 600°C at a heating rate of 10°C / min; and calculating the mass percentage of elemental sulfur in the sulfur-carbon composite material using the lost sulfur mass. Figure 9 , combined Figure 9 It can be seen that for the sulfur-carbon composite material prepared in Example 1, about 40% of the elemental sulfur is located inside the pores of the porous carbon, which is consistent with the amount added during preparation.

[0275] This application also obtained scanning electron microscope images of the porous carbon material prepared in Example 1 and the resulting sulfur-carbon composite material, and obtained... Figure 10 The testing steps included: placing each sample on the sample stage, immersing it in the electron microscope chamber, evacuating the vacuum, turning on the electron beam, and setting appropriate parameters for characterization: morphology observation parameters were 3kV, aperture 30μm, and working distance 5mm–6mm. Figure 10 It can be seen that the surface roughness of the sulfur-carbon composite material is increased compared to that of the porous carbon material, and the size of the sulfur-carbon composite material within the field of view does not change significantly.

[0276] Example 1

[0277] A method for preparing a battery cell is provided, comprising the following preparation process:

[0278] Preparation of positive electrode sheet:

[0279] The sulfur-carbon composite material prepared in Example 1 above, and conductive carbon black (specific surface area of ​​453 m²) were used. 2 PVDF and PVDF are mixed in a ratio of 70%:20%:10%, and then stirred with N-methylpyrrolidone solvent to form a positive electrode slurry. This slurry is then coated onto both surfaces of the positive electrode current collector aluminum foil and dried using a multi-section oven at sequential temperatures of 120℃ / 100℃ / 90℃. Finally, it is compacted using a cold press to obtain a positive electrode film with a compaction density of 1.57 g / cm³. 3 .

[0280] Preparation of negative electrode sheet:

[0281] Sodium metal sheets with a thickness of 2.0 mm and a diameter of 16 mm are provided.

[0282] Provide isolation components:

[0283] A porous polypropylene (PP) membrane with a thickness of 13 μm was used as the separator.

[0284] Provide electrolytes:

[0285] Sodium hexafluorophosphate was dispersed in ethylene glycol dimethyl ether to form a 1 mol / L solution in an argon atmosphere glove box with a water content of <10 ppm.

[0286] Assemble individual battery cells (button cells):

[0287] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The stacked bare cells are then assembled to form a battery cell. The battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained.

[0288] Example 2

[0289] A method for preparing a battery cell is provided. The difference between Example 2 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Example 2, while the rest is the same as in Example 1.

[0290] Example 3

[0291] A method for preparing a battery cell is provided. The difference between Example 3 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material prepared in Example 3, while the rest is the same as in Example 1.

[0292] Example 4

[0293] A method for preparing a battery cell is provided. The difference between Example 4 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Example 4, while the rest is the same as in Example 1.

[0294] Example 5-1

[0295] A method for preparing a battery cell is provided. The difference between Example 5-1 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material prepared in Example 5-1, while the rest is the same as in Example 1.

[0296] Example 5-2

[0297] A method for preparing a battery cell is provided. The difference between Example 5-2 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Example 5-2, while the rest is the same as in Example 1.

[0298] Example 6-1

[0299] A method for preparing a battery cell is provided. The difference between Example 6-1 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material prepared in Example 6-1, while the rest is the same as in Example 1.

[0300] Comparative Example 1

[0301] A method for preparing a battery cell is provided. The difference between Comparative Example 1 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Comparative Example 1, while the rest is the same as in Example 1.

[0302] Comparative Example 2

[0303] A method for preparing a battery cell is provided. The difference between Comparative Example 2 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Comparative Example 2, while the rest is the same as in Example 1.

[0304] Comparative Example 3

[0305] A method for preparing a battery cell is provided. The difference between Comparative Example 3 and Example 1 is that the positive electrode active material is the sulfur-carbon composite material obtained in Comparative Example 3, while the rest is the same as in Example 1.

[0306] Example 7

[0307] A method for preparing a battery cell is provided, which differs from Example 1 in that the conductive agent includes carbon black (with a specific surface area of ​​453 m²). 2 / g, 7wt%) and graphene (specific surface area of ​​664m²) 2 / g, 2wt%) and carbon nanotubes (specific surface area of ​​1204m²) 2 / g, 1wt%), otherwise the same as in Example 1.

[0308] Example 8

[0309] A method for preparing a battery cell is provided. The difference between this method and Example 1 is that the electrolyte contains an ionic liquid additive, which is sodium tetrabutylphosphine hexafluorophosphate. The mass percentage of sodium tetrabutylphosphine hexafluorophosphate in the ether component is 0.01%, and the rest is the same as in Example 1.

[0310] Example 9

[0311] A method for preparing a battery cell is provided, which differs from Example 1 in that a sodium bromide coating with a thickness of 5 μm is formed on both sides of the sodium metal sheet.

[0312] Example 10

[0313] A method for preparing a battery cell is provided, which differs from Example 1 in that an aluminum oxide coating is formed on both sides of the base film of the separator (the thickness of the aluminum oxide coating on one side is 1.5 μm).

[0314] [Positive Electrode Film Performance Test]

[0315] (1) Measure the compaction density of the positive electrode film:

[0316] The thickness H of the positive electrode film was obtained using a micrometer.

[0317] Take a positive electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated electrode sheet, the electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S0, weigh it, and record its weight as M1; then wipe off the electrode film layer of the positive electrode sheet after weighing it, weigh the current collector, and record it as M0. The surface density of the positive electrode film layer is D = (M1 - M0) / S0.

[0318] Then the compaction density of the positive electrode film is equal to the surface density D of the positive electrode film / the thickness H of the positive electrode film.

[0319] (2) Measure the saturation liquid absorption rate of the positive electrode film for the ether component.

[0320] The electrolyte solvent was selected from the non-aqueous organic solvent in Example 1: ethylene glycol dimethyl ether. The following test procedures were used to measure the electrolyte at room temperature:

[0321] Step 1: Cut a piece of the positive electrode sheet with an area of ​​1540.25 cm² from the top, middle, and bottom. 2 Weigh the three small circular pieces and subtract the weight of the substrate aluminum foil from each; record the weights as m. 上 m 中 m 下 ;

[0322] Step 2: Take three 100ml beakers and pour in 50g of the above electrolyte solvent. Place the three small discs into one beaker respectively. Record the weight of the small discs every 10 minutes until it no longer changes. Then subtract the weight of the substrate aluminum foil and record it as M. 上 M 中 M 下 ;

[0323] Step 3, Calculation formula for saturated liquid absorption rate = ((M 上 -m 上 ) / m 上 +(M 中 -m 中 ) / m 中 +(M 下 -m 下 ) / m 下 ) / 3.

[0324] [Battery Performance Test]

[0325] (3) Measure the charging and discharging capacity of the battery cells in the first cycle:

[0326] 3.1 The sulfur-containing active material is elemental sulfur:

[0327] At 25°C, the battery prepared above was charged to 2.8V at a constant current of 0.2C (1C=1675mA / g). At this point, the battery was fully charged, and the charging capacity was recorded, which is the first charging capacity. After the battery was left to stand for 5 minutes, it was discharged to 0.5V at a constant current of 0.2C. This is one cycle of charging and discharging, and the discharge capacity was recorded.

[0328] 3.2 The sulfur-containing active material is sodium sulfide:

[0329] At 25°C, the battery prepared above was charged to 3.0V at a constant current of 0.2C (1C=686mA / g). At this time, the battery was fully charged, and the charging capacity at this time was recorded, which is the charging capacity of the first cycle. After the battery was left to stand for 5 minutes, it was discharged to 1.0V at a constant current of 0.2C. This is one cycle of charging and discharging, and the discharge capacity at this time was recorded.

[0330] (4) Measure the capacity retention rate of individual battery cells after 200 cycles:

[0331] 4.1 The sulfur-containing active material is elemental sulfur:

[0332] At 25℃, the battery prepared above was charged at a constant current of 0.2C (1C = 1675mA / g) to 2.8V. At this point, the battery was fully charged, and the charging capacity was recorded, which is the first charge capacity. After the battery was left to stand for 5 minutes, it was discharged at a constant current of 0.2C to 0.5V. This is one charge-discharge cycle, and the discharge capacity was recorded, which is the first discharge capacity. The battery was subjected to cyclic charge-discharge tests in the above manner until 200 cycles were completed. The battery capacity retention rate (%) after 200 cycles at 25℃ is calculated as: (Discharge capacity after 200 cycles / Discharge capacity of the first cycle) × 100%.

[0333] 4.2 The sulfur-containing active material is sodium sulfide:

[0334] At 25℃, the battery prepared above was charged at a constant current of 0.2C (1C = 686mA / g) to 3.0V. At this point, the battery was fully charged, and the charging capacity was recorded, which is the first charge capacity. After the battery was left to stand for 5 minutes, it was discharged at a constant current of 0.2C to 1.0V. This is one charge-discharge cycle, and the discharge capacity was recorded, which is the first discharge capacity. The battery was subjected to cyclic charge-discharge tests in the above manner until 200 cycles were completed. The battery capacity retention rate (%) after 200 cycles at 25℃ is calculated as: (Discharge capacity after 200 cycles / Discharge capacity of the first cycle) × 100%.

[0335] The battery performance is shown in Table 2 below.

[0336] Table 2 Battery Performance List

[0337]

[0338] Based on the above Examples 1, 2, 3, and 4, as well as Comparative Examples 1 and 2, it can be seen that the average pore size, specific surface area, and pore volume of the porous carbon material of this application have a significant impact on the specific capacity and capacity retention rate of the battery.

[0339] As can be seen from the above embodiments 1 and 7, the present application can directly increase the compaction density of the positive electrode film and further improve the specific capacity of the battery by selecting a conductive agent with strong conductivity in the positive electrode film layer.

[0340] As can be seen from the above Examples 1 and 8, adding a certain amount of ionic liquid additives to the electrolyte in this application is beneficial to improving the cycle stability of the battery.

[0341] As can be seen from the above embodiments 1 and 9, the selection of sodium metal sheets with a certain coating in this application is also beneficial to improving the cycle stability of the battery.

[0342] Therefore, the battery cell provided in this application improves the specific capacity of the battery by reducing the loss of positive electrode active material during battery cycling, and also improves the cycle stability of the battery.

[0343] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This 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 battery cell, characterized by: The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer on at least one side surface of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material. The positive electrode active material comprises a sulfur-carbon composite material, which comprises a porous carbon material and a sulfur-containing active material loaded on the porous carbon material. The sulfur-containing active material comprises any one or more of elemental sulfur, sodium sulfide or sodium polysulfide. The porous carbon material has micropores and mesopores, and the micropores and the mesopores are interconnected and form a tortuous pore structure. The negative electrode sheet comprises a sodium metal sheet. The micropores have a pore size of less than 2 nm, and the mesopores have a pore size of 2 nm to 50 nm.

2. The battery cell of claim 1, wherein: The average pore size of the porous carbon material is 1.6 nm to 2.0 nm. The pore volume of the porous carbon material is 0.35 mL / g to 0.6 mL / g.

3. The battery cell of any one of claims 1-2, wherein: The specific surface area of the porous carbon material is 700 m 2 / g ~ 1087 m 2 / g; The porous carbon material comprises a nitride, which comprises any one or more of cobalt nitride, iron nitride, nickel nitride, zinc nitride or yttrium nitride.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The mass percentage of the sulfur-containing active material in the sulfur-carbon composite material is 20% to 80%.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The positive electrode film layer comprises a conductive agent, which comprises any one or more of carbon black, graphene or carbon nanotubes.

6. The battery cell of any one of claims 1-5, wherein: The compacted density of the positive electrode film layer is 1.40 g / cm 3 ~ 1.65 g / cm 3 .

7. The battery cell of any one of claims 1-6, wherein: The mass percentage of the conductive agent in the positive electrode film layer is 10% to 20%.

8. The battery cell according to claim 7, wherein: and / or; The specific surface area of the carbon black is 100 m 2 / g to 500 m 2 / g; and / or; The specific surface area of the graphene is 400 m 2 / g ~ 1000 m 2 / g; The battery cell comprises an electrolyte, and the electrolyte comprises an ether component. The specific surface area of the carbon nanotubes is 300 m 2 / g to 1500 m 2 / g.

9. The battery cell of any one of claims 1-8, wherein: The saturation liquid absorption rate of the positive electrode film layer to the ether component is 80% to 120%. The electrolyte comprises an ionic liquid additive, and the cation of the ionic liquid additive comprises any one or more of a nitrogen-containing onium ion and a phosphorus-containing onium ion, and the anion of the ionic liquid additive comprises any one or more of a halogen ion, a phosphate ion, a borate ion and a sulfonimide anion.

10. The battery cell of any one of claims 1-9, wherein: The thickness of the sodium metal sheet is 1 mm to 5 mm.

11. The battery cell of any one of claims 1-10, wherein: and / or; At least one side surface of the sodium metal sheet is formed with a sodium bromide coating layer, and the thickness of the sodium bromide coating layer is 2 μm to 12 μm. The separator comprises a base film and a coating layer on at least one side surface of the base film.

12. The battery cell of any one of claims 1-11, wherein: The coating layer comprises any one or more of an organic coating layer and an inorganic coating layer. The process comprises the following steps:

13. A method of producing the battery cell of claim 1, characterized by: Preparation of a sulfur-carbon composite material: dissolving a sulfur-containing active material in a first solvent, adding a porous carbon material, uniformly mixing, heat treating until the first solvent is completely evaporated, obtaining a mixture, sintering the mixture in an inert atmosphere to obtain the sulfur-carbon composite material; Preparation of a positive electrode sheet: dispersing the sulfur-carbon composite material in a second solvent to obtain an electrode slurry, coating the electrode slurry on the surface of a positive electrode current collector to form a positive electrode film layer; Preparation of a battery cell: assembling the positive electrode sheet, a negative electrode sheet and a separator to form a battery cell. The sintering temperature is 150°C to 1200°C, and the time is 3 h to 12 h.

14. The method of claim 13, wherein: The median particle size of the porous carbon material is 0.8 μm to 1.5 μm.

15. The method of any one of claims 13-14, wherein: The total mass of the sulfur-containing active material and the porous carbon material accounts for 10% to 100% of the mass of the first solvent.

16. The method of any one of claims 13-15, wherein: ​ 17. The method of any one of claims 13-16, wherein: The first solvent includes any one or more of ethanol, water, acetone, tetrahydrofuran; The second solvent includes N-methylpyrrolidone.

18. A battery device, characterized by: A battery cell comprising the battery cell of any one of claims 1 to 12 or the battery cell produced by the method of any one of claims 13 to 17.

19. An electrical device, comprising: A battery device comprising the battery cell of claim 18.

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