Negative electrode sheet, electrode assembly, battery cell, battery, and electric device

Abstract

The application discloses a negative electrode sheet, an electrode assembly, a battery monomer, a battery and an electric equipment. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector. The negative electrode active material layer comprises a dispersing agent and halloysite nanotubes. The dispersing agent is a cellulose dispersing agent. The mass content of the halloysite nanotubes is 0.05% to 1.00% based on the mass of the negative electrode active material layer. In the application, the ion conductivity of the negative electrode sheet can be improved, the direct current impedance of the battery can be reduced, the capacity retention rate of the battery can be improved, and the short-term performance and the cycle performance of the battery can be significantly improved by adding the cellulose dispersing agent and the halloysite nanotubes with the mass content in the range.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a negative electrode sheet, electrode assembly, battery cell, battery, and electrical device. Background Technology

[0002] In recent years, with the increasing demand for clean energy and the rapid development of the new energy field, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in battery technology, higher requirements have been placed on their electrochemical performance and other aspects.

[0003] To further meet user needs and improve user experience, improving the short-term and cycle performance of batteries has become an urgent technical problem to be solved. Summary of the Invention

[0004] In view of the above problems, this application provides a negative electrode sheet, electrode assembly, battery cell, battery, and electrical device, which can improve the short-term performance and cycle performance of the battery.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, embodiments of this application provide a negative electrode sheet, including a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a dispersant and halloysite nanotubes. The dispersant is a cellulose-based dispersant, wherein the mass content of halloysite nanotubes is 0.05%-1.00% based on the mass of the negative electrode active material layer.

[0007] In the technical solution of this application, the cellulose-based dispersant can decompose into positively charged cations and negatively charged anions in solution, which attach to the surface of halloysite nanotubes. This causes mutual repulsion between the halloysite nanotubes due to electrical interactions, reducing the possibility of agglomeration. The well-dispersed halloysite nanotubes can form a broad ion-conducting network in the negative electrode, shortening the transport paths of lithium ions in multiple directions within the negative electrode. This is more conducive to the adsorption and transport of lithium ions in the ion-conducting network, improving lithium ion mobility, thereby increasing the ionic conductivity of the negative electrode, improving the DC impedance and capacity retention of the battery cell, and thus significantly improving the short-term and long-term performance of the battery cell.

[0008] In some embodiments, the halloysite nanotube content is 0.10%-0.40% based on the mass of the negative electrode active material layer. In this embodiment, the halloysite nanotubes within the above-mentioned mass content range, under the dispersing effect of the cellulose dispersant, are beneficial to the formation of the ion-conducting network in the negative electrode sheet, thereby improving the short-term performance and cycle performance of the battery cell.

[0009] In some embodiments, the porosity of the negative electrode sheet is 19%-26%. In this embodiment, halloysite nanotubes have a nanotube structure, and well-dispersed halloysite nanotubes can increase the porosity of the negative electrode sheet, which is beneficial for accelerating the transport of lithium ions in the negative electrode sheet, thereby improving the short-term performance and cycle performance of the battery cell.

[0010] In some embodiments, the ionic conductivity of the negative electrode is 0.05-0.30 S / m. In this embodiment, halloysite nanotubes have a nanotubular structure with a positive internal charge and a negative external charge, which can facilitate the adsorption and transport of lithium ions and effectively improve the ionic conductivity of the negative electrode, thus improving the short-term performance and cycle performance of the battery cell.

[0011] In some embodiments, the average diameter of halloysite nanotubes is 10-20 nm.

[0012] In some embodiments, the average length of halloysite nanotubes is 200-500 nm.

[0013] In some embodiments, the volume average particle size Dv50 of halloysite nanotubes is 5-10 μm.

[0014] In the above embodiments, halloysite nanotubes whose average diameter, average length, and volume average particle size meet the above range can improve the lithium-ion transport efficiency, thus benefiting the short-term performance and cycle performance of battery cells.

[0015] In some embodiments, the mass content of the dispersant is 0.50%-1.50% based on the mass of the negative electrode active material layer. In this embodiment, the mass content of the dispersant meets a certain lower limit requirement to avoid adding too little dispersant, thus ensuring sufficient dispersion of halloysite nanotubes in the negative electrode sheet and forming a wide-ranging ion-conducting network. The mass content of the dispersant also meets a certain upper limit requirement to avoid adding too much dispersant, because further increasing the amount of dispersant will have limited effect on improving the dispersion of halloysite nanotubes, and will reduce the effect on reducing the DC resistance of the battery cell and improving the capacity retention of the battery cell.

[0016] In some embodiments, the cellulose dispersant includes at least one of carboxymethyl, carboxyethyl, and carboxypropyl groups. In this embodiment, when the cellulose dispersant includes groups within the above range, it is beneficial for dispersing halloysite nanotubes in the negative electrode sheet.

[0017] In some embodiments, the cellulose dispersant includes at least one selected from carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxyethyl carboxymethyl cellulose, sodium hydroxyethyl carboxymethyl cellulose, lithium hydroxyethyl carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose, lithium hydroxypropyl carboxymethyl cellulose, and sodium hydroxypropyl carboxymethyl cellulose. In this embodiment, using a cellulose dispersant within the above range can effectively improve the dispersion of halloysite nanotubes in the negative electrode, which is beneficial for the formation of the ion-conducting network.

[0018] In some embodiments, a solution of 1% by mass of a cellulose dispersant has a viscosity of 3000-5000 mPa·s at a temperature of 25°C. In this embodiment, a cellulose dispersant with a solution viscosity within the above range can effectively disperse halloysite nanotubes in the negative electrode sheet.

[0019] In some embodiments, the weight-average molecular weight (Mw) of the cellulose dispersant is 600,000-800,000 Da. In this embodiment, the cellulose dispersant with a weight-average molecular weight (Mw) within the above range can have a certain viscosity, which is beneficial for the dispersion of halloysite nanotubes in the negative electrode 221.

[0020] Secondly, embodiments of this application provide an electrode assembly, including a negative electrode sheet as described in the above embodiments.

[0021] Thirdly, embodiments of this application provide a battery cell including the electrode assembly as described in the above embodiments.

[0022] Fourthly, embodiments of this application provide a battery, including a battery cell as described in the above embodiments.

[0023] Fifthly, embodiments of this application provide an electrical device, including a battery cell as described in the above embodiments or a battery as described in the above embodiments.

[0024] 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, the following are specific embodiments of this application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0027] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0028] Figure 3 Exploded views of a single battery cell provided in some embodiments of this application;

[0029] Figure 4 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0030] Figure 5 This is a schematic diagram of the structure of a first type of negative electrode sheet provided in some embodiments of this application;

[0031] Figure 6 This is a schematic diagram of the structure of a second negative electrode sheet provided in some embodiments of this application.

[0032] icon:

[0033] 1000 - Vehicles;

[0034] 100 - Battery; 200 - Controller; 300 - Motor;

[0035] 10-Box body; 11-First part; 12-Second part; 13-Accommodation space;

[0036] 20-Battery cell; 21-Casing; 22-Electrode assembly; 23-Electrode terminal; 24-Pressure relief structure;

[0037] 211-Shell; 212-Cover; 213-Sealed space;

[0038] 221 - Negative electrode; 222 - Positive electrode; 223 - Separator;

[0039] 2211 - Negative electrode current collector; 2212 - Negative electrode active material layer. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0043] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0044] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not 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.

[0045] In the description of the embodiments of this application, the technical term "and / or", such as "feature 1 and / or feature 2", refers to three cases: feature 1 alone, feature 2 alone, and feature 1 plus feature 2.

[0046] In the description of the embodiments of this application, unless otherwise stated, "multiple" in "one or more" means two or more.

[0047] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0050] Currently, power batteries still suffer from high impedance, especially under fast charging conditions. Taking lithium-ion batteries as an example, high impedance degrades both short-term and cycle performance. DCR (Discharge-Resistant Component Analysis) analysis of the battery revealed that the resistance of the negative electrode accounts for approximately 30% of the total internal resistance of the battery.

[0051] For negative electrode sheets, reducing the impedance is mainly achieved by increasing the ionic conductivity. In some technical solutions, the morphology of the negative electrode active material is altered by changing its synthesis method, thereby increasing the ionic conductivity. However, the steps involved in changing the material morphology in these solutions are generally quite complex. Complex production steps and processes reduce production efficiency and increase production costs, hindering large-scale deployment.

[0052] Based on the above considerations, adding high-conductivity ion-additives to the negative electrode is relatively simple and easy to implement. In some technical solutions, halloysite nanotubes are added to the negative electrode. Halloysite nanotubes can promote the transport of lithium ions in the electrolyte, thereby reducing DC impedance and improving capacity retention. However, in the above technical solutions, the dispersion of halloysite nanotubes in the negative electrode is poor. Due to their special nano-linear tubular structure, they are prone to agglomeration and difficult to disperse fully, thus failing to maximize the effect of halloysite nanotubes on improving the ionic conductivity of the negative electrode.

[0053] Building upon this foundation, the applicant's in-depth research revealed that adding cellulose-based dispersants and halloysite nanotubes to the negative electrode sheet allows the cellulose-based dispersants to decompose into positively charged cations and negatively charged anions in solution. These anions adhere to the surface of the halloysite nanotubes, creating a repulsive force between them due to electrical properties, thus reducing the likelihood of agglomeration. The well-dispersed halloysite nanotubes can form a broad ion-conducting network within the negative electrode sheet, shortening the transport paths of lithium ions in multiple directions within the sheet. This facilitates the adsorption and transport of lithium ions within the ion-conducting network, improving lithium ion mobility and consequently enhancing the ionic conductivity of the negative electrode sheet. This, in turn, improves the DC impedance and capacity retention of the battery cell, significantly enhancing both the short-term and long-term performance of the battery cell.

[0054] Based on this, embodiments of this application provide a negative electrode sheet, wherein the active material layer of the negative electrode sheet includes a cellulose-based dispersant and halloysite nanotubes, which can form a wide-ranging ion-conducting network in the negative electrode sheet, improve the ionic conductivity of the negative electrode sheet, and thereby reduce the DC impedance of the negative electrode sheet, thereby effectively improving the impedance and performance of the battery (e.g., short-term performance and cycle performance).

[0055] From a market perspective, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of the application areas of power batteries, the market demand is also constantly increasing.

[0056] For ease of explanation, the following embodiments use a vehicle as an example of an electrical device according to an embodiment of this application.

[0057] See Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 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 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0058] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0059] In this application, battery 100 refers to a single physical module comprising multiple battery cells 20 to provide higher voltage and capacity, which may be in the form of a battery pack, battery module, etc. Battery 100 may include a housing 10 for encapsulating the multiple battery cells 20, the housing 10 preventing liquids or other foreign objects from affecting the charging or discharging of the battery cells 20.

[0060] See Figure 2 , Figure 2 This is an exploded view of a battery 100 provided in some embodiments of this application. The battery 100 includes a housing 10 and a plurality of battery cells 20, which are housed within the housing 10. The housing 10 is used to house the battery cells 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, defining a receiving space 13 for accommodating the battery cells 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, overlapping the open side of the second portion 12 to form a housing 10 with the receiving space 13; alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, overlapping the open side of the second portion 12 to form a housing 10 with the receiving space 13. Of course, the first portion 11 and the second portion 12 can have various shapes, such as cylinders, cuboids, etc.

[0061] In battery 100, multiple battery cells 20 can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, parallel, or in a mixed configuration to form modules, and then these modules can be connected in series, parallel, or in a mixed configuration to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed configurations of the multiple battery cells 20.

[0062] The battery cell 20 refers to the smallest unit that makes up the battery pack. The battery cell 20 can be a secondary battery 100 or a primary battery 100; it can also be a lithium-sulfur battery 100, a sodium-ion battery 100 or a magnesium-ion battery 100, but is not limited to these.

[0063] See Figure 3 The battery cell 20 may include a housing 21, an electrode assembly 22 and an electrolyte, with the electrode assembly 22 and the electrolyte both housed within the housing 21.

[0064] The outer casing 21 may include a housing 211 and a cover 212. The housing 211 is an assembly that fits with the cover 212 to form an internal sealed space 213 of the battery cell 20, wherein the formed sealed space 213 can be used to accommodate the electrode assembly 22, electrolyte, and other components. The cover 212 is a component that covers the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 may be adapted to the shape of the housing 211 to fit the housing 211, and functional components such as electrode terminals 23 and pressure relief structures 24 may also be provided on the cover 212. A sealing ring may be provided between the opening of the housing 211 and the cover 212 to achieve a seal between the housing 211 and the cover 212.

[0065] The housing 211 and cover 212 can be of various shapes and sizes, such as cuboids, cylinders, and hexagonal prisms. Specifically, the shapes of the housing 211 and cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing 211 and cover 212 can be various, such as, but not limited to, metals like copper, iron, aluminum, stainless steel, and aluminum alloys. The materials of the sealing ring can be various, such as, but not limited to, materials resistant to electrolyte corrosion, high toughness, and fatigue resistance, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A plating layer can be formed on the outer surface of the housing 211, and the plating layer material can be various, such as, but not limited to, corrosion-resistant materials like Ni and Cr.

[0066] See Figure 4 The electrode assembly 22 can be composed of a negative electrode 221, a positive electrode 222, and a separator 223. The battery cell 20 mainly operates by the movement of metal ions between the negative electrode 221 and the positive electrode 222. The negative electrode 221 includes a negative current collector 2211 and a negative active material layer 2212 disposed on the surface of the negative current collector 2211. The material of the negative current collector 2211 can be copper, and the material of the negative active material layer 2212 can be carbon, silicon, etc. The positive electrode 222 includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The material of the positive current collector can be aluminum, and the material of the positive active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganese oxide, lithium-rich manganese-based materials, lithium-sulfur, etc. Furthermore, the electrode assembly 22 can be a wound structure or a stacked structure; the embodiments of this application are not limited to these.

[0067] The negative electrode sheet proposed in the embodiments of this application will be described in detail below.

[0068] See Figure 5 and Figure 6 In a first aspect, embodiments of this application provide a negative electrode sheet 221, including a negative electrode current collector 2211 and a negative electrode active material layer 2212 disposed on at least one side of the negative electrode current collector 2211. The negative electrode active material layer 2212 includes a dispersant and halloysite nanotubes. The dispersant is a cellulose-based dispersant. The mass content of halloysite nanotubes is 0.05%-1.00% based on the mass of the negative electrode active material layer 2212.

[0069] In the negative electrode sheet 221, a negative electrode active material layer 2212 can be formed on one side surface of the negative electrode current collector 2211, such as... Figure 5 As shown; alternatively, negative electrode active material layers 2212 can be respectively provided on both sides of the negative electrode current collector 2211, such as Figure 6 As shown.

[0070] The negative electrode active material can be a carbon-containing active material, a silicon-containing active material, or an active material containing both carbon and silicon.

[0071] A dispersant can be a material that can perform a dispersing function.

[0072] Cellulose dispersants are dispersants whose chemical structure contains a cellulose structure. The cellulose structure can include -C6H... 10 O5-.

[0073] Halloysite nanotubes are tubular aluminosilicate natural nanomaterials. The chemical formula of halloysite nanotubes can be Al₂O₃·2SiO₂·nH₂O (n = 0 or 2). Halloysite nanotubes can include a bilayer structure, consisting of an inner layer and an outer layer. The inner layer can be alumina, and the outer layer can be silicon oxide. The inner alumina layer can be octahedral and may contain a certain amount of hydroxyl groups, making it positively charged. The outer silicon oxide layer can be tetrahedral and may contain a small amount of Si-OH groups, making it negatively charged.

[0074] Based on the mass of the negative electrode active material layer 2212, the mass content of halloysite nanotubes can be the mass percentage of halloysite nanotubes added during the preparation of the negative electrode slurry 221, expressed as a percentage. As an example, the mass content of halloysite nanotubes can be, for example, but not limited to, any one of 0.05%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, and 1.00%, or a range between any two.

[0075] Halloysite nanotubes have a unique nano-linear tubular structure and an electrical difference between the inner and outer layers, which can shorten the transport path of lithium ions in the electrolyte in the negative electrode 221, accelerate the transport of lithium ions, and thus improve the ionic conductivity of the negative electrode 221.

[0076] However, due to its unique nano-linear tubular structure, halloysite nanotubes tend to agglomerate in the negative electrode 221, making it difficult to disperse them fully and thus failing to maximize their effect of improving ionic conductivity.

[0077] In the technical solution of this application, the cellulose-based dispersant can decompose into positively charged cations and negatively charged anions in solution, which attach to the surface of halloysite nanotubes. This causes mutual repulsion between the halloysite nanotubes due to electrical interactions, reducing the possibility of agglomeration. The well-dispersed halloysite nanotubes can form a wide-ranging ion-conducting network within the negative electrode 221, shortening the transport paths of lithium ions in multiple directions within the negative electrode 221. This is more conducive to the adsorption and transport of lithium ions in the ion-conducting network, improving lithium ion mobility, and thus increasing the ionic conductivity of the negative electrode 221. This improves the DC impedance and capacity retention of the battery cell 20, thereby significantly enhancing the short-term and long-term performance of the battery cell 20.

[0078] In some embodiments, the mass content of halloysite nanotubes is 0.10%-0.40% based on the mass of the negative electrode active material layer 2212.

[0079] Based on the mass of the negative electrode active material layer 2212, the mass content of halloysite nanotubes can be the mass percentage of halloysite nanotubes added during the preparation of the negative electrode slurry 221, expressed as a percentage. As an example, the mass content of halloysite nanotubes can be, for example, but not limited to, any one of 0.10%, 0.20%, 0.30%, and 0.40%, or a range between any two.

[0080] In this embodiment, under the dispersing effect of cellulose-based dispersants, halloysite nanotubes within the above-mentioned mass content range are beneficial to the formation of the ion-conducting network in the negative electrode 221, thereby improving the short-term performance and cycle performance of the battery cell 20.

[0081] In some embodiments, the porosity of the negative electrode 221 is 19%-26%.

[0082] The porosity of the negative electrode 221 can be expressed as the ratio of the volume of pores in the negative electrode 221 to its total volume, expressed in percentage (%). The porosity of the negative electrode 221 can be measured using test methods known in the art. For example, it can be measured using the AccuPyc II 1340 true density meter according to the WI-PCA-080 true density method, as per national standard GB / T 24586-2009.

[0083] As an example, the porosity of the negative electrode 221 may be, for example, but not limited to, a point value of 19%, 20%, 21%, 22%, 23%, 24%, 25%, and 26%, or a range of any two.

[0084] In this embodiment, halloysite nanotubes have a nanotube structure. The well-dispersed halloysite nanotubes can increase the porosity of the negative electrode 221, which is beneficial to accelerate the transport of lithium ions in the negative electrode 221, thereby improving the short-term performance and cycle performance of the battery cell 20.

[0085] In some embodiments, the ionic conductivity of the negative electrode 221 is 0.05-0.30 S / m.

[0086] The ionic conductivity of the negative electrode 221 can be a physical quantity characterizing the ability of ions to conduct electricity, with units of S / m. The ionic conductivity of the negative electrode 221 can be measured using test methods known in the art. As an example, it can be measured using electrochemical impedance spectroscopy with a VMP3 electrochemical co-workstation, referring to standard WI-ATC-2013.

[0087] As an example, the ionic conductivity of the negative electrode 221 may be, for example, but not limited to, any one of 0.05 S / m, 0.10 S / m, 0.15 S / m, 0.20 S / m, 0.25 S / m and 0.30 S / m or a range between any two.

[0088] In this embodiment, halloysite nanotubes have a nanotube-like structure with a positive charge inside and a negative charge outside, which can facilitate the adsorption and transport of lithium ions and effectively improve the ionic conductivity of the negative electrode 221. Therefore, it is beneficial to improve the short-term performance and cycle performance of the battery cell 20.

[0089] In some embodiments, the average diameter of halloysite nanotubes is 10-20 nm.

[0090] The average diameter of halloysite nanotubes can be the average of the diameters of multiple halloysite nanotubes, measured in nm. The average diameter of halloysite nanotubes can be measured using methods known in the art. For example, the average diameter can be obtained by statistically analyzing and calculating the results from SEM and TEM tests using Nano Measurer software.

[0091] As an example, the average diameter of halloysite nanotubes can be, for example, but not limited to, a point value of any one of 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm and 20 nm, or a range of any two.

[0092] In this embodiment, the average diameter of the halloysite nanotubes meets a certain lower limit requirement to prevent the average diameter from being too small, which could accelerate the lithium-ion transport rate. The average diameter of the halloysite nanotubes also meets a certain upper limit requirement to prevent the average diameter from being too large. If the average diameter of the halloysite nanotubes increases further, the number of halloysite nanotubes per unit area decreases, reducing the effectiveness of improving the ionic conductivity of the negative electrode 221, thereby affecting the reduction of the DC impedance of the battery cell 20 and the improvement of the capacity retention rate of the battery cell 20.

[0093] In some embodiments, the average length of halloysite nanotubes is 200-500 nm.

[0094] The average length of halloysite nanotubes can be the average of the lengths of multiple halloysite nanotubes, measured in nm. The average length of halloysite nanotubes can be measured using methods known in the art. For example, the average length can be obtained by statistically analyzing and calculating the results from SEM and TEM tests using Nano Measurer software.

[0095] As an example, the average length of halloysite nanotubes can be, for example, but not limited to, any one of 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range between any two.

[0096] In this embodiment, the average length of the halloysite nanotubes meets a certain lower limit requirement to prevent the average length from being too small, which could accelerate the lithium-ion transport rate. The average length of the halloysite nanotubes also meets a certain upper limit requirement to prevent the average length from being too large. If the average length of the halloysite nanotubes further increases, the lithium-ion transport path will also increase accordingly, reducing the effectiveness of improving the ionic conductivity of the negative electrode 221, thereby affecting the reduction of the DC impedance of the battery cell 20 and the improvement of the capacity retention rate of the battery cell 20.

[0097] In some embodiments, the volume average particle size Dv50 of halloysite nanotubes is 5-10 μm.

[0098] The volume average particle size (Dv50) of halloysite nanotubes can be defined as the particle size corresponding to a cumulative volume percentage of 50% for halloysite nanotube materials, expressed in μm. The volume average particle size (Dv50) of halloysite nanotubes can be measured using methods known in the art. For example, it can be measured using a Malvern laser particle size analyzer, such as the Malvern Mastersizer-3000, in accordance with GB / T 19077-2016.

[0099] As an example, the volume average particle size Dv50 of halloysite nanotubes can be, for example, but not limited to, any one of 5 μm, 6 μm, 7 μm, 8 μm, 9 μm and 10 μm or a range of any two.

[0100] In this embodiment, the volume average particle size Dv50 of halloysite nanotubes meets the above range, which can shorten the lithium ion transport path, improve the lithium ion transport efficiency, and help improve the short-term performance and cycle performance of the battery cell 20.

[0101] In some embodiments, the mass content of the dispersant is 0.50%-1.50% based on the mass of the negative electrode active material layer 2212.

[0102] Based on the mass of the negative electrode active material layer 2212, the mass content of the dispersant can be the mass percentage of the dispersant added during the preparation of the negative electrode slurry 221, expressed as a percentage. As an example, the mass content of the dispersant can be, for example, but not limited to, any one of 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 1.10%, 1.20%, 1.30%, 1.40%, and 1.50%, or a range between any two.

[0103] In this embodiment, the mass content of the dispersant meets a certain lower limit requirement to avoid insufficient addition of the dispersant, so that the halloysite nanotubes are sufficiently dispersed in the negative electrode 221, forming a wide-ranging ion-conducting network. The mass content of the dispersant also meets a certain upper limit requirement to avoid excessive addition of the dispersant, because further increasing the amount of dispersant will have limited effect on improving the dispersion of halloysite nanotubes, and will reduce the effect on reducing the DC resistance of the battery cell 20 and improving the capacity retention of the battery cell 20.

[0104] In some embodiments, the cellulose dispersant includes at least one of carboxymethyl, carboxyethyl, and carboxypropyl.

[0105] The chemical structure of carboxymethyl groups can be -CH2COO-.

[0106] The chemical structural formula of carboxyethyl can be -CH2CH2COO-.

[0107] The chemical structural formula of carboxypropyl can be -CH2CH2CH2COO-.

[0108] In this embodiment, when the cellulose dispersant includes groups within the above-mentioned range, it is beneficial to disperse halloysite nanotubes in the negative electrode 221.

[0109] In some embodiments, the cellulose dispersant includes at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxyethyl carboxymethyl cellulose, sodium hydroxyethyl carboxymethyl cellulose, lithium hydroxyethyl carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose, lithium hydroxypropyl carboxymethyl cellulose, and sodium hydroxypropyl carboxymethyl cellulose.

[0110] The cations dissolved in water by cellulose dispersants may include at least one of hydrogen ions, lithium ions, and sodium ions.

[0111] In this embodiment, the use of cellulose-based dispersants within the above-mentioned range can effectively improve the dispersion of halloysite nanotubes in the negative electrode 221, which is beneficial to the formation of the ion-conducting network.

[0112] In some embodiments, a solution of 1% by mass of a cellulose dispersant has a viscosity of 3000-5000 mPa·s at a temperature of 25°C.

[0113] The solution viscosity of cellulose dispersants can be a physical quantity that measures the viscosity of the cellulose dispersant fluid, and the unit is mPa·s. The solution viscosity of cellulose dispersants can be measured using test methods known in the art. As an example, the viscosity can be measured using a DV-2TLV instrument, as per the national standard GB / T 10247-2008.

[0114] As an example, the viscosity of a 1% by mass solution of a cellulose dispersant at a temperature of 25°C can be, for example, but not limited to, any one of 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4500 mPa·s, and 5000 mPa·s, or a range between any two.

[0115] In this embodiment, cellulose-based dispersants with solution viscosity within the above-mentioned range can achieve a good dispersion effect on halloysite nanotubes in the negative electrode 221.

[0116] In some embodiments, the weight-average molecular weight (Mw) of the cellulose dispersant is 600,000-800,000 Da.

[0117] The weight-average molecular weight (Mw) of cellulose dispersants can be the average molecular weight calculated by weight, i.e., the molecular weight obtained on average per unit weight, and the unit is Da. The weight-average molecular weight of cellulose dispersants can be determined using test methods known in the art. As an example, the national standard GB / T 21863-2008 can be referred to for standard testing using gel permeation chromatography, such as using an ultra-high performance polymer chromatograph (model: ACQUITY APC).

[0118] As an example, the weight-average molecular weight of a cellulose dispersant may be, for example, but not limited to, any one of 600,000 Da, 650,000 Da, 700,000 Da, 750,000 Da, and 800,000 Da, or a range between any two.

[0119] In this embodiment, the cellulose-based dispersant with a weight-average molecular weight Mw within the above range can have a certain viscosity, which is beneficial to the dispersion of halloysite nanotubes in the negative electrode 221.

[0120] Secondly, embodiments of this application provide an electrode assembly 22, including a negative electrode sheet 221 as described in the above embodiments.

[0121] Thirdly, embodiments of this application provide a battery cell 20, including an electrode assembly 22 as described in the above embodiments.

[0122] Fourthly, embodiments of this application provide a battery 100, including a battery cell 20 as described in the above embodiments.

[0123] Fifthly, embodiments of this application provide an electrical device, including a battery cell 20 as described in the above embodiments or a battery 100 as described in the above embodiments.

[0124] According to some embodiments of this application, the negative electrode 221 includes a negative electrode current collector 2211 and a negative electrode active material layer 2212 disposed on at least one side of the negative electrode current collector 2211. The negative electrode active material layer 2212 includes a dispersant and halloysite nanotubes. The dispersant is a cellulose-based dispersant. The mass content of halloysite nanotubes is 0.05-1.00% based on the mass of the negative electrode active material layer 2212.

[0125] Based on the negative electrode 221 provided in the embodiments of this application, the material composition and morphology can be confirmed by inductively coupled plasma (ICP), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS), and the dispersant and halloysite nanotubes and their mass content in the negative electrode 221 can be calculated in reverse.

[0126] The following specific embodiments are provided to better illustrate this application.

[0127] I. Preparation of battery cells

[0128] Preparation of the negative electrode sheet

[0129] The negative electrode active material, artificial graphite, conductive agent, carbon black, binder, styrene-butadiene rubber (SBR), cellulose dispersant, and halloysite nanotubes are dissolved in deionized water in a certain mass ratio (in some comparative examples, if there is no cellulose dispersant and / or halloysite nanotubes, they are not added). After being mixed evenly, a negative electrode slurry is prepared. The negative electrode slurry is uniformly coated on copper foil once or multiple times and dried at 90°C. After cold pressing and slitting, a negative electrode sheet is obtained.

[0130] Preparation of the positive electrode sheet

[0131] The positive electrode active material, ternary material lithium nickel cobalt manganese oxide (NCM622), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were prepared in a mass ratio of 97:2:1, dissolved in N-methylpyrrolidone (NMP), stirred for 4 hours, and the viscosity was adjusted to 10000 mPa·s with NMP. After mixing evenly, a positive electrode slurry was prepared. The positive electrode slurry was uniformly coated on aluminum foil once or multiple times and dried at 90°C. After cold pressing and slitting, the positive electrode sheet was obtained.

[0132] Preparation of Electrolyte

[0133] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3 / 7. 12.5% ​​LiPF6 lithium salt is added and dissolved in the organic solvent and stirred evenly to obtain the electrolyte.

[0134] [Preparation of the separating membrane]

[0135] Polyethylene film is used as the separation membrane.

[0136] Preparation of lithium-ion battery cells

[0137] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. Then, the electrodes are wound, tabs are welded, and the cells are housed in an aluminum casing. The casing is then baked at 105°C to remove moisture, followed by the injection of electrolyte and sealing to obtain a single, uncharged battery cell. This uncharged battery cell then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain a lithium-ion battery cell.

[0138] II. Testing Methods

[0139] Porosity Test

[0140] You can refer to the national standard GB / T 24586-2009 and use the AccuPycⅡ1340 true density meter to conduct the test according to the WI-PCA-080 true density method.

[0141] Electrode porosity testing utilizes the displacement method of a small-molecule diameter inert gas (helium), combined with Archimedes' principle and Bohr's law (PV = nRT), to accurately measure the true volume of the material being tested, thereby obtaining the porosity of the sample.

[0142] Calculation formulas: Apparent volume V2 = S * H ​​* A; Porosity P = (V2 - V1) / V2 * 100%

[0143] Where: S - area, cm 2 H - Thickness, cm; A - Number of samples, EA; V1 - True volume of the sample, cm³ 3 V2 – Apparent volume of the sample, cm³ 3 P—Porosity of the sample, %.

[0144] [Ion Conductivity Test]

[0145] Electrochemical impedance spectroscopy can be performed using the VMP3 electrochemical co-workstation, referring to the standard WI-ATC-2013.

[0146] The specific testing method is as follows: (1) Bake the aluminum-plastic film, electrode, and separator at 60°C for 4 hours before use; (2) Prepare the die, 23*35*2mm; (3) Cut the electrode into small pieces slightly larger than the die size with ceramic scissors and place them on the die for punching. Take out the punched electrode with tweezers for later use; (4) Then make the electrode into a single-layer symmetrical cell; (5) Place the symmetrical cell in an electrochemical workstation to test EIS, set the frequency to 0.5Hz-200kHz, and the disturbance voltage to 10mV; (6) Calculate the ionic resistance Rion of the electrode through the intersection of the two straight lines of EIS; (7) Electrode ionic conductivity = d (electrode thickness) / (Rion * A (electrode area)).

[0147] [Average Diameter and Average Length Test]

[0148] Based on the SEM and TEM test results, the Nano Measurer software was used to statistically analyze and calculate the results to obtain the average diameter and length.

[0149] SEM testing was conducted in accordance with the testing standards of JY / T 010-1996, using a Sigma 300 scanning electron microscope and energy dispersive spectroscopy (EDS) instrument, and following the WI-PCA-053 standard guidelines for surface micro-area morphology analysis.

[0150] TEM testing was performed according to GB / T 34002-2017, using a 200kV field emission scanning transmission electron microscope JEOL JEM-F200. The STEM-HAADF resolution was 0.16nm@200kV; the EDS energy resolution was MnKa 133eV, and the accelerating voltages were 200kV and 80kV.

[0151]

Volume Average Particle Size Dv50 Test

[0152] The national standard GB / T 19077-2016 can be referenced, and a Malvern laser particle size analyzer can be used for characterization testing, such as the Malvern Mastersizer-3000.

[0153] Viscosity Test

[0154] The viscosity can be measured using a DV-2TLV instrument, referring to the national standard GB / T 10247-2008. The measurement accuracy is ±1% of the full scale. The full scale range is related to the rotor and rotation speed. The specific test steps are as follows: (1) Pretreatment: Pour the sample into a special sample cup and keep it at the temperature to be measured; (2) Test: Select the corresponding rotor speed according to the approximate range of the sample viscosity, select the Multi Point data acquisition mode, and start automatic detection.

[0155] [Weight-average molecular weight test]

[0156] The test can be performed using gel permeation chromatography, referring to the national standard GB / T 21863-2008.

[0157] Specifically, the test can be performed as follows: Use an ultra-high performance polymer chromatograph: ACQUITY APC; Detector: ACQUITY differential refractive index detector. The test steps are as follows: (1) Preheating: Install the chromatographic column and tubing, turn on the control panel, test the power supply, etc., and open the test software Empower; (2) Parameter settings: Injection volume: 0μL to 50μL (depending on the sample concentration); Pump flow rate: 0.2mL / min; Mobile phase: 30mol / L LiBr NMP solution; Sealing cleaning solution: isopropanol; Pre-column: PL gel 10um MiniMIX-B Guard (size: 50mm×4.6mm×2); Analytical phase: PL gel 10um MiniMIX-B (size: 250mm×4.6mm); Standard: polystyrene sleeve; Run time: 30min; Detector: ACQUITY differential refractive index (RI) detector; Column oven temperature: 90℃; Detector temperature: 55℃. (3) Sample testing: a. Preparation of standard and test samples: Weigh 0.002g to 0.004g of standard / test sample and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard and place it in the refrigerator for >8h; b. Standard / sample testing: Edit the sample group to be tested, select the established sample group method, and after the baseline stabilizes, click the run queue to start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, establish a calibration curve using a chemical workstation, perform integral quantification on the sample spectrum, and the chemical workstation automatically generates molecular weight and molecular weight distribution results.

[0158] DC Impedance Reduction Rate Test

[0159] At 25°C, the capacity of the above lithium-ion battery was tested at a charging rate of 0.33C and a discharging rate of 0.33C. Then, the cell was adjusted to 50% SOC and charged and discharged at a 4C rate for 60 seconds. The DC resistance of the first 30 seconds of each discharge was extracted.

[0160] The rate of decrease in DC impedance of a lithium-ion battery = [(DC resistance - DC resistance of Comparative Example 1) / DC resistance of Comparative Example 1] × 100%.

[0161] In the embodiments and comparative examples of this application, the greater the DC impedance reduction rate, the better the short-term performance of the battery cell.

[0162] [Capacity Retention Rate Test]

[0163] At 25°C, the lithium-ion battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, it was discharged at a rate of 1 / 3C to 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion battery was subjected to the above steps for charge-discharge cycle testing, and the discharge capacity of the 800th cycle was recorded.

[0164] The capacity retention rate of a lithium-ion battery after 800 cycles = (discharge capacity of the 800th cycle / discharge capacity of the first cycle) × 100%.

[0165] In the embodiments and comparative examples of this application, a higher capacity retention rate means better cycle performance of the battery cell.

[0166] III. Experimental Conditions and Test Results

[0167] The types, mass content, morphology, and performance test results of the additives used in the negative electrode active material layer of each experimental group are shown in Tables 1 and 2. Among them, the performance test results of the battery cells include the DC impedance reduction rate and capacity retention rate of the battery cells.

[0168] Table 1

[0169]

[0170]

[0171] Table 2

[0172]

[0173] According to Tables 1 and 2:

[0174] In Examples 1-26, the negative electrode active material layer all included a cellulose-based dispersant and halloysite nanotubes at a mass content of 0.05%-1.00%. Compared with Comparative Example 1, which did not include a cellulose-based dispersant and halloysite nanotubes in its negative electrode active material layer, the ionic conductivity and porosity of the negative electrode sheet were significantly improved, and the DC impedance reduction rate and capacity retention rate of the battery cell were also significantly improved. This indicates that the battery cells in Examples 1-26 have significantly improved short-term performance and cycle performance. In Comparative Example 2, no halloysite nanotubes were added to the negative electrode active material layer, but sodium carboxymethyl cellulose was added at the same mass content as in Examples 1-11. However, the ionic conductivity and porosity of the negative electrode sheet were still much lower than in Examples 1-11, and the resulting battery cell had poor DC impedance and capacity retention rate. This indicates that adding a cellulose-based dispersant alone to the negative electrode active material layer has limited effect on improving the short-term performance and cycle performance of the battery cell. In Comparative Example 3, the negative electrode active material layer included 1.00% sodium carboxymethyl cellulose and 1.50% halloysite nanotubes. Under the influence of cellulose-based dispersants, the excessive amount of halloysite nanotubes (relatively in the range of 0.05%-1.00%) did not further improve the DC impedance reduction rate and capacity retention of the battery cells; in fact, the effect worsened. In Comparative Example 4, the negative electrode active material layer included 0.10% halloysite nanotubes but no dispersant. Compared to Example 2, the halloysite nanotubes were difficult to disperse fully in the negative electrode sheet, resulting in poorer ionic conductivity and porosity. The effect of adding halloysite nanotubes alone to the negative electrode active material layer on improving the DC impedance and capacity retention of the battery cells was also limited.

[0175] In Examples 1-11, the negative electrode active material layer all included sodium carboxymethyl cellulose, and the mass content of sodium carboxymethyl cellulose was 1.00% in all examples. Specifically, in Examples 1 and 2, when the mass content of halloysite nanotubes was in the range of 0.05%-0.10%, the ionic conductivity and porosity of the negative electrode gradually increased with the gradual increase of the halloysite nanotube mass content, and the DC impedance reduction rate and capacity retention rate of the battery cell also gradually improved. In Examples 3-11, when the mass content of halloysite nanotubes was in the range of 0.20%-1.00%, although the ionic conductivity and porosity of the negative electrode decreased to some extent with the gradual increase of the halloysite nanotube mass content, the resulting battery cell still exhibited a significantly improved DC impedance reduction rate and capacity retention rate. In Examples 2-5, when the mass content of halloysite nanotubes was in the range of 0.10%-0.40%, the battery cell exhibited further improved short-term performance and cycle performance.

[0176] In Examples 2, 12, and 13, the mass content of halloysite nanotubes in the negative electrode active material layer was 0.10%, and the mass content of cellulose dispersant was in the range of 0.05%-1.50%. The resulting battery cells exhibited good DC impedance reduction rate and capacity retention rate, demonstrating superior short-term performance and cycle performance.

[0177] In Examples 2 and 14-16, the negative electrode active material layer includes halloysite nanotubes with a mass content of 0.10% and different types of cellulose dispersants with a mass content of 1.00%. The resulting battery cells all have good short-term performance and cycle performance.

[0178] In Examples 17-26, the negative electrode active material layer comprised 0.10% halloysite nanotubes and 1.00% sodium carboxymethyl cellulose by mass. In Examples 18-20, when the average diameter of the halloysite nanotubes was in the range of 10-20 nm and the volume average particle size Dv50 was in the range of 6.3-8.9 μm, the resulting battery cells exhibited better DC impedance reduction and capacity retention. In Examples 23-25, when the average length of the halloysite nanotubes was in the range of 200-500 nm and the volume average particle size Dv50 was in the range of 6.4-8.2 μm, the resulting battery cells showed even more significant improvements in DC impedance reduction and capacity retention.

[0179] It should be noted that this application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments that have the same structure and achieve the same effect as the technical concept within the scope of this application are all included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, characterized in that, The negative electrode active material layer includes a dispersant and halloysite nanotubes. The dispersant is a cellulose-based dispersant, wherein the mass content of the halloysite nanotubes is 0.05%-1.00% based on the mass of the negative electrode active material layer.

2. The negative electrode sheet according to claim 1, characterized in that, Based on the mass of the negative electrode active material layer, the mass content of the halloysite nanotubes is 0.10%-0.40%.

3. The negative electrode sheet according to claim 1 or 2, characterized in that, The porosity of the negative electrode sheet is 19%-26%.

4. The negative electrode sheet according to any one of claims 1-3, characterized in that, The ionic conductivity of the negative electrode is 0.05-0.30 S / m.

5. The negative electrode sheet according to any one of claims 1-4, characterized in that, The halloysite nanotubes have an average diameter of 10-20 nm.

6. The negative electrode sheet according to any one of claims 1-5, characterized in that, The halloysite nanotubes have an average length of 200-500 nm.

7. The negative electrode sheet according to any one of claims 1-6, characterized in that, The volume average particle size Dv50 of the halloysite nanotubes is 5-10 μm.

8. The negative electrode sheet according to any one of claims 1-7, characterized in that, Based on the mass of the negative electrode active material layer, the mass content of the dispersant is 0.50%-1.50%.

9. The negative electrode sheet according to any one of claims 1-8, characterized in that, The cellulose dispersant includes at least one of carboxymethyl, carboxyethyl, and carboxypropyl.

10. The negative electrode sheet according to any one of claims 1-9, characterized in that, The cellulose dispersant includes at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxyethyl carboxymethyl cellulose, sodium hydroxyethyl carboxymethyl cellulose, lithium hydroxyethyl carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose, lithium hydroxypropyl carboxymethyl cellulose, and sodium hydroxypropyl carboxymethyl cellulose.

11. The negative electrode sheet according to any one of claims 1-10, characterized in that, A solution of the cellulose dispersant with a mass fraction of 1% has a viscosity of 3000-5000 mPa·s at a temperature of 25°C.

12. The negative electrode sheet according to any one of claims 1-11, characterized in that, The weight-average molecular weight (Mw) of the cellulose dispersant is 600,000-800,000 Da.

13. An electrode assembly, characterized in that, Includes the negative electrode sheet as described in any one of claims 1-12.

14. A single battery cell, characterized in that, Includes the electrode assembly as described in claim 13.

15. A battery, characterized in that, Includes the battery cell as described in claim 14.

16. An electrical appliance, characterized in that, This includes the battery cell as described in claim 14 or the battery as described in claim 15.

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