Secondary battery, manufacturing method for negative electrode sheet, and electric device

Abstract

The present application provides a secondary battery. The secondary battery comprises an electrode sheet, wherein the electrode sheet comprises a current collector and an active material layer arranged on at least one side of the current collector, the active material layer comprises a kinetic additive, the structure of the kinetic additive comprises a cavity, and the average diameter of the cavity is 0.8 to 1.5 nm.

Description

Preparation methods and electrical devices for secondary batteries and negative electrode sheets. Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a secondary battery and an electrical device. Background Technology

[0002] In recent years, secondary 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 many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] With the development of electrical devices, such as new energy vehicles, higher requirements are being placed on the rate performance of secondary batteries.

[0004] Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide a secondary battery with high kinetic performance, thereby improving the rate performance of the battery.

[0006] The first aspect of this application provides a secondary battery, the secondary battery including an electrode, the electrode including a current collector and an active material layer disposed on at least one side of the current collector, the active material layer including a kinetic additive, the kinetic additive including a cavity in its structure, the cavity having an average diameter of 0.8 nm-1.5 nm.

[0007] By utilizing the cavity of a certain diameter within the kinetic additive in the active material layer, the kinetic additive can act as a conductor of ions but not of solvent molecules in the active material layer, thereby improving the transport efficiency of active ions in the active material layer, reducing the DC resistance of the secondary battery, improving the kinetic performance of the secondary battery, and enhancing the electrochemical performance of the secondary battery at high rates.

[0008] In any embodiment, the diameter of the cavity is 0.9-1.5 nm.

[0009] Kinetic additives with cavity diameters within the above range can regulate the solvation structure of active ions, which is more conducive to desolvation and further improves the transport efficiency of active ions in the active material layer. At the same time, it reduces the probability of the cavity being blocked by the binder in the active material layer, and simultaneously reduces the DC internal resistance of the secondary battery, improving the kinetic performance of the secondary battery, especially the kinetic performance at low temperature, and improving the electrochemical performance of the secondary battery at high rates.

[0010] In any embodiment, the kinetic additive comprises cyclodextrin and its derivatives; the cyclodextrin comprises an X-membered glycocyclic molecule, wherein X comprises any integer from 7 to 12.

[0011] Cyclodextrin contains a large number of hydroxyl groups, which enables it to be effectively dispersed in slurry. It also has high affinity and compatibility with active materials and binders in the active material layer, which can effectively improve the active ion transport efficiency of the active material layer, reduce the DC resistance of the secondary battery, improve the kinetic performance of the secondary battery, and enhance the electrochemical performance of the secondary battery at high rates.

[0012] In any embodiment, the kinetic additive contains an active group, which may be one or more of a sulfonic acid group or a carboxyl group.

[0013] The aforementioned active groups can improve the affinity of the kinetic additive to the binder and active material in the film layer, so that the kinetic additive can be uniformly distributed on the surface of the active material.

[0014] In any embodiment, the kinetic additive contains an active metal-substituted active group, which may be one or more of lithium carboxylate, sodium carboxylate, lithium sulfonate, and sodium sulfonate.

[0015] Theoretical calculations show that the aforementioned functional groups can reduce the solvation energy of active ions, which is beneficial to improving the efficiency of active ion desolvation. Furthermore, the active metal-substituted active groups can further improve the replacement efficiency of active ions in the active material layer through the substitution of active ions, reducing the DC resistance of the secondary battery, improving the kinetic performance of the secondary battery, and enhancing the electrochemical performance of the secondary battery at high rates. Simultaneously, the lone pair electrons of the oxygen atoms in the cavity coordinate with the active ions, accelerating the transport of active ions. This, combined with the cavity of the kinetic additive, and leveraging the large specific surface area around the cavity, increases the replacement rate of active ions, which is beneficial to reducing the DC resistance of the secondary battery, improving its kinetic performance, and enhancing its electrochemical performance at high rates.

[0016] In any embodiment, the total molar content of unsubstituted and active metal-substituted active groups in the kinetic additive is calculated, wherein the molar content of active metal-substituted active groups is 20%-70%.

[0017] Kinetic additives with a molar percentage of active metal-substituted active groups within the above-mentioned range have the dual effect of improving the kinetic performance of secondary batteries and enhancing electrode flexibility.

[0018] In any embodiment, the kinetic additive includes one or more of lithium sulfonate cyclodextrin, lithium carboxyl cyclodextrin, sodium sulfonate cyclodextrin, and sodium carboxyl cyclodextrin.

[0019] In any embodiment, the mass content of the kinetic additive is 0.1%-1% based on the total mass of the active material layer.

[0020] When the mass content of the kinetic additive is within the above range, the secondary battery can have both good kinetic performance and cycle life.

[0021] In any embodiment, the active material layer further includes an adhesive, the adhesive comprising a linear polymer, the linear polymer comprising an acrylic polymer.

[0022] Acrylic polymers possess abundant polar groups, providing sufficient cohesive force and bonding strength as electrode binders. Furthermore, as linear polymers, their molecular chains extend within the slurry, allowing them to coat the surface of the active material in the film layer. This reduces exposed defects, effectively minimizing side reactions on the electrode surface and reducing the consumption of active ions, thus improving initial efficiency. However, the coating of active materials with acrylic polymers can negatively impact the kinetic performance of the secondary battery. By adding kinetic additives to the active material layer, these additives can coat the surface of the active material along with the binder, providing a dedicated fast channel for the transport of active ions. This allows the secondary battery to achieve both high initial efficiency and good kinetic performance.

[0023] In any embodiment, the mass content of the adhesive is 0.5%-2.5% based on the total mass of the active material layer.

[0024] In any embodiment, the active material layer further includes active material, and the mass content of the active material is 95%-98.5% based on the total mass of the active material layer.

[0025] The required content of conductive agent and binder in this active material layer is reduced compared to the active material layer in the prior art. Moreover, no additives are needed in this active material layer, which allows for a further increase in the mass content of the negative electrode active material, which is beneficial for further improving the energy density of the secondary battery.

[0026] In any embodiment, the unilateral density of the active material layer is 4.5-100 mg / cm³. 2 20-30 mg / cm³ is an option. 2 .

[0027] This secondary battery can achieve an extremely high areal density, which is beneficial for further improving the energy density of the secondary battery. However, the extremely high areal density increases the path of active ion solid-phase transport, which reduces the kinetic performance of the secondary battery. The kinetic additive in the embodiments of this application is suitable for electrodes with various coating methods, especially for thick-coated electrodes, so as to achieve a balance between the energy density and kinetic performance of the secondary battery.

[0028] In any embodiment, the secondary battery further includes an electrolyte comprising a first solvent and a second solvent, wherein the first solvent comprises ethylene carbonate (EC) and the second solvent comprises one or more of dimethyl carbonate (DMC) and propylene carbonate (PC).

[0029] Kinetic additives can regulate the solvation structure of active ions by means of their cavity diameter and surface active groups, resulting in lower solvation energy of the regulated active ions, which is more conducive to desolvation and further improves the transport efficiency of active ions in the active material layer. At the same time, it reduces the probability of the cavity being blocked by the binder in the active material layer. By means of the ion liquid phase conduction of the solvation structure, the kinetic performance of the secondary battery is improved, the DC resistance of the secondary battery is reduced, especially the DC resistance at low temperature, and the electrochemical performance of the secondary battery at high rate is improved.

[0030] The second aspect of this application provides a method for preparing a negative electrode sheet, the method comprising: providing a negative electrode slurry, rolling the negative electrode slurry into a film and then laminating it onto a negative electrode current collector; drying to form a negative electrode active material layer; the negative electrode slurry includes a kinetic additive, the structure of which includes a cavity with a diameter of 0.6-1.5 nm.

[0031] This preparation method can improve the coating effect of binders and kinetic additives on the surface of negative electrode active materials through roll forming, reduce lithium consumption, improve the first efficiency of secondary batteries, and improve the kinetic and rate performance of secondary batteries. It can also increase the solid content of negative electrode slurry, reduce the moisture content that needs to be volatilized during the slurry drying process, effectively reduce drying stress, reduce the risk of cracking, meet the requirements of thick electrode sheet manufacturing, increase the areal density of negative electrode active material layer, and break through the upper limit of energy density of secondary batteries in the existing technology.

[0032] In any embodiment, the solid content of the negative electrode slurry is 60%-90%.

[0033] This negative electrode slurry has a high solids content, which helps to reduce production energy consumption, improve production efficiency, improve membrane warping, and increase membrane thickness.

[0034] In any embodiment, the step of rolling the negative electrode slurry into a film and then laminating it onto the negative electrode current collector includes: mixing the binder and kinetic additive evenly, adding the active material to knead it into a ball, rolling it into a film, and then laminating it onto the negative electrode current collector.

[0035] Mixing the binder and kinetic additive uniformly beforehand helps improve the dispersibility of the kinetic additive in the binder, allowing them to co-coat the surface of the active material and improve the kinetic performance of the secondary battery.

[0036] A third aspect of this application provides an electrical device comprising a secondary battery of the first aspect or a secondary battery comprising a negative electrode sheet prepared by the preparation method of the second aspect. Attached Figure Description

[0037] Figure 1 is a schematic diagram of the structure of cyclodextrin according to an embodiment of this application;

[0038] Figure 2 is a schematic diagram of a secondary battery according to an embodiment of this application;

[0039] Figure 3 is an exploded view of the secondary battery according to an embodiment of this application shown in Figure 2;

[0040] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0041] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0042] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5;

[0043] Figure 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0044] Explanation of reference numerals in the attached diagram: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0045] The embodiments of the secondary battery and power-consuming device of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] 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 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 "ab" 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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] With the development of high-power electrical devices, such as new energy vehicles, higher requirements are being placed on the rate performance of secondary batteries. Rate performance refers to the battery's performance at high charge and discharge rates. The better the rate performance of a battery, the faster it can charge and discharge while maintaining a high capacity.

[0053] Based on this, this application provides a secondary battery, including an electrode, the electrode including a current collector and an active material layer disposed on at least one side of the current collector, the active material layer including a kinetic additive, the kinetic additive including a cavity in its structure, the average diameter of the cavity being 0.6-1.5 nm.

[0054] In some embodiments, the average diameter of the cavity may be selected as 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1.0nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, or any value range between the two.

[0055] The average diameter of the cavity in the kinetic additive can be characterized by any method known in the art or obtained by consulting reference books. For example, the kinetic additive can be observed by light scattering, small-angle X-ray scattering, nuclear magnetic resonance, or transmission electron microscopy. For instance, the average diameter of the cavity in the kinetic additive can be characterized using a JEM-2100F 200kV field emission transmission electron microscope. To characterize the cavity of the kinetic additive, the major axis is used as the diameter, and at least five samples are measured, with the average value taken as the average diameter.

[0056] The kinetic additives in this application can be tested using any known method. For example, the type of kinetic additive can be determined by infrared spectroscopy or by differential scanning calorimetry (DSC), and the cavity diameter of the kinetic additive can be obtained through theoretical calculations or by consulting reference books.

[0057] It is understandable that the electrode can be a negative electrode or a positive electrode.

[0058] The negative electrode includes a negative current collector. In some embodiments, the negative current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0059] By utilizing the cavity of a certain diameter within the kinetic additive in the active material layer, the kinetic additive can act as a conductor of ions but not of solvent molecules in the active material layer, thereby improving the transport efficiency of active ions in the active material layer, reducing the DC resistance of the secondary battery, improving the kinetic performance of the secondary battery, and enhancing the electrochemical performance of the secondary battery at high rates.

[0060] In some embodiments, the electrode is a negative electrode. Kinetic additives including cavities can more effectively improve the ion transport rate within the electrode, thereby enhancing the kinetic performance of the secondary battery and its electrochemical performance at high rates.

[0061] In some embodiments, the diameter of the cavity is 0.9-1.5 nm.

[0062] Kinetic additives with cavity diameters within the aforementioned range can regulate the solvation structure of active ions, resulting in lower solvation energy of the regulated active ions, which is more conducive to desolvation and further improves the transport efficiency of active ions in the active material layer. At the same time, it reduces the probability of the cavity being blocked by the binder in the active material layer, and simultaneously reduces the DC internal resistance of the secondary battery, improving the kinetic performance of the secondary battery, especially the kinetic performance at low temperatures, and improving the electrochemical performance of the secondary battery at high rates.

[0063] In some embodiments, the kinetic additive includes cyclodextrin and its derivatives, wherein the cyclodextrin comprises an X-membered glycocyclic molecule, wherein X comprises any integer from 7 to 12.

[0064] Cyclodextrins (CDs) are a collective term for a series of cyclic oligosaccharides produced from amylose by cyclodextrin glucosyltransferases generated by Bacillus. Cyclodextrin molecules have a slightly conical, hollow cylindrical three-dimensional cyclic structure, as shown in Figure 1. In its hollow structure, the upper outer end is composed of secondary hydroxyl groups at C2 and C3, and the lower end is composed of primary hydroxyl groups at C6, exhibiting hydrophilicity. The interior of the cavity, shielded by CH bonds, forms a hydrophobic region. Examples of cyclodextrins include α-cyclodextrin (a six-membered sugar ring molecule), β-cyclodextrin (a seven-membered sugar ring molecule), and γ-cyclodextrin (an eight-membered sugar ring molecule). α-Cyclodextrins and their derivatives include, but are not limited to, 2,4-dimethyl α-cyclodextrin, hydroxypropyl α-cyclodextrin, carboxypropyl α-cyclodextrin, sulfonic acid α-cyclodextrin, and their substituted derivatives. β-Cyclodextrins and their derivatives include, but are not limited to, sulfonic acid β-cyclodextrin, 1,5-hydroxypropyl β-cyclodextrin (B1), carboxypropyl β-cyclodextrin, and their substituted derivatives. Gamma cyclodextrins and their derivatives include, but are not limited to, sulfonic acid gamma cyclodextrin, 1,5-hydroxypropyl gamma cyclodextrin, carboxypropyl gamma cyclodextrin, and their substituted derivatives.

[0065] It should be noted that the kinetic additives in this application are not limited to cyclodextrins with 7 or 8 glucose molecules, such as β-cyclodextrin and its derivatives, γ-cyclodextrin and its derivatives, but also include cyclodextrins and their derivatives polymerized from 9, 10, 11, 12 glucose units.

[0066] Cyclodextrin contains a large number of hydroxyl groups, which enables it to be effectively dispersed in slurry. It also has high affinity and compatibility with active materials and binders in the active material layer, which can effectively improve the active ion transport efficiency of the active material layer, reduce the DC resistance of the secondary battery, improve the kinetic performance of the secondary battery, and enhance the electrochemical performance of the secondary battery at high rates.

[0067] In some embodiments, the kinetic additive contains an active group, which may be one or more of a sulfonic acid group or a carboxyl group.

[0068] The aforementioned active groups can improve the affinity of the kinetic additive to the binder and active material in the film layer, so that the kinetic additive can be uniformly distributed on the surface of the active material.

[0069] In some embodiments, the kinetic additive contains an active metal-substituted active group, which may be one or more of lithium carboxylate, sodium carboxylate, lithium sulfonate, and sodium sulfonate.

[0070] Theoretical calculations show that the aforementioned functional groups can reduce the solvation energy of active ions, which is beneficial to improving the efficiency of active ion desolvation. Furthermore, the active metal-substituted active groups can further improve the replacement efficiency of active ions in the active material layer through the substitution of active ions, reducing the DC resistance of the secondary battery, improving the kinetic performance of the secondary battery, and enhancing the electrochemical performance of the secondary battery at high rates. Simultaneously, the lone pair electrons of the oxygen atoms in the cavity coordinate with the active ions, accelerating the transport of active ions. This, combined with the cavity of the kinetic additive, and leveraging the large specific surface area around the cavity, increases the replacement rate of active ions, which is beneficial to reducing the DC resistance of the secondary battery, improving its kinetic performance, and enhancing its electrochemical performance at high rates.

[0071] In some embodiments, the molar content of the active metal-substituted active groups in the kinetic additive is calculated based on the total molar content of unsubstituted and active metal-substituted active groups, wherein the molar content of active metal-substituted active groups is 20%-70%.

[0072] In some embodiments, the molar content of the active metal-substituted and unsubstituted active groups in the kinetic additive is used as the basis, wherein the molar content of the active metal-substituted active groups can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range between the two.

[0073] Kinetic additives with a molar percentage of active metal-substituted active groups within the above-mentioned range have the dual effect of improving the kinetic performance of secondary batteries and enhancing electrode flexibility.

[0074] In some embodiments, the kinetic additive includes one or more of sulfonic acid β-cyclodextrin, 1,5-hydroxypropyl β-cyclodextrin, carboxypropyl β-cyclodextrin, sulfonic acid γ-cyclodextrin, 1,5-hydroxypropyl γ-cyclodextrin, carboxypropyl γ-cyclodextrin, 9-12 polysaccharide copolymer cyclodextrin, and their lithium-modified and sodium-modified materials.

[0075] In some embodiments, the kinetic additive includes one or more of lithium sulfonate cyclodextrin, lithium carboxyl cyclodextrin, and lithium carboxyl cyclodextrin.

[0076] In some embodiments, the mass content of the kinetic additive is 0.1%-1% based on the total mass of the active material layer.

[0077] In some embodiments, based on the total mass of the active material layer, the mass content of the kinetic additive can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any range between the two.

[0078] When the mass content of the kinetic additive is within the above range, the secondary battery can have both good kinetic performance and cycle life.

[0079] In some embodiments, the active material layer further includes an adhesive comprising a linear polymer, which in turn comprises an acrylic polymer.

[0080] Binders can be classified into linear polymers and particulate polymers based on their dispersion morphology in solvents. Linear polymers exhibit a linear morphology in solvents, enabling polymer chain extension and thus coating of active materials in the film layer. Examples include, but are not limited to, polyacrylic acid and polymethyl acrylate. Particulate polymers refer to binders that exhibit a dot-like morphology in solvents. These binders generally present a particulate distribution in both the solvent and the coating, often consisting of latex particles. Examples include, but are not limited to, styrene-butadiene rubber and styrene-acrylic rubber.

[0081] Acrylic polymers refer to polymers formed by homopolymerization or copolymerization of acrylic acid and its derivatives with other monomers. It can be understood that acrylic polymers may also include other monomers capable of polymerizing with acrylic monomers, such as acrylonitrile and propylene sulfonic acid.

[0082] Acrylic acid and its derivatives include, but are not limited to, acrylic acid, methacrylic acid, 2-ethylacrylic acid, 3,3-dimethylacrylic acid, 3-propylacrylic acid, trans-2-methyl-3-ethylacrylic acid, cis-2-methyl-3-ethylacrylic acid, 3-isopropylacrylic acid, trans-3-methyl-3-ethylacrylic acid, cis-3-methyl-3-ethylacrylic acid, 2-isopropylacrylic acid, trimethacrylic acid, 2-methyl-3,3-diethylacrylic acid, 3-butylacrylic acid, 2-butylacrylic acid, 2-pentylacrylic acid, 2-methyl-2-hexenoic acid, trans-3-methyl-2-hexenoic acid, 3-methyl-3-propylacrylic acid, 2-ethyl-3-propylacrylic acid, 2,3-diethylacrylic acid, 3,3-diethylacrylic acid, 3-methyl-3-hexylacrylic acid, 3-methyl-3-tert-butylacrylic acid, 2-methyl-3-pentylacrylic acid, 3-methyl-3-pentylacrylic acid, 4-methyl-2-hexenoic acid, 4-ethyl... 2-Hexenoic acid, 3-methyl-2-ethyl-2-hexenoic acid, 3-tert-butylacrylic acid, 2,3-dimethyl-3-ethylacrylic acid, 3,3-dimethyl-2-ethylacrylic acid, 3-methyl-3-isopropylacrylic acid, 2-methyl-3-isopropylacrylic acid, trans-2-octenenoic acid, cis-2-octenenoic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 3,3,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, n-tetradecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, methoxymethyl acrylate, methoxyethyl acrylate, ethoxymethyl acrylate, ethoxyethyl acrylate, perfluorooctyl acrylate.

[0083] Acrylic polymers possess abundant polar groups, providing sufficient cohesive force and bonding strength as electrode binders. Furthermore, as linear polymers, their molecular chains extend within the slurry, allowing them to coat the surface of the active material in the film layer. This reduces exposed defects, effectively minimizing side reactions on the electrode surface and reducing the consumption of active ions, thus improving initial efficiency. However, the coating of active materials with acrylic polymers can negatively impact the kinetic performance of the secondary battery. By adding kinetic additives to the active material layer, these additives can coat the surface of the active material along with the binder, providing a dedicated fast channel for the transport of active ions. This allows the secondary battery to achieve both high initial efficiency and good kinetic performance.

[0084] In some embodiments, the adhesive content is 0.5%-2.5% based on the total mass of the active material layer.

[0085] In some embodiments, the mass content of the adhesive, based on the total mass of the active material layer, can be selected as 0.5%, 1%, 1.5%, 2%, 2.5%, or any value range between the two.

[0086] In some embodiments, the active material layer further includes active material, the mass content of which is 95%-98.5% based on the total mass of the active material layer.

[0087] In some embodiments, the electrode is a negative electrode, and the active material is a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0088] In some embodiments, based on the total mass of the active material layer, the mass content of the active material can be selected as 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, or any range between the two.

[0089] The required content of conductive agent and binder in this active material layer is reduced compared to the active material layer in the prior art. Moreover, no additives are needed in this active material layer, which allows for a further increase in the mass content of the negative electrode active material, which is beneficial for further improving the energy density of the secondary battery.

[0090] In some embodiments, the active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the mass content of the conductive agent is 0.2% to 0.9% based on the total mass of the active material layer.

[0092] In some embodiments, the mass content of the conductive agent can be selected as 0.2%, 0.3%, 0.5%, 0.7%, 0.9%, or any value range between the two, based on the total mass of the active material layer.

[0093] The active materials in this secondary battery are tightly packed, which allows for a further reduction in the content of conductive agents.

[0094] In some embodiments, the unilateral density of the active material layer is 4.5-100 mg / cm³. 2 20-30 mg / cm³ is an option. 2 .

[0095] In some embodiments, the unilateral density of the active material layer may be selected as 4.5 mg / cm³. 2 10mg / cm 2 20mg / cm 2 30mg / cm 2 40mg / cm 2 50mg / cm 2 60mg / cm 2 70mg / cm 2 80mg / cm 2 90mg / cm 2 100mg / cm 2 Or the range of values ​​between any two.

[0096] This secondary battery can achieve an extremely high areal density, which is beneficial for further improving the energy density of the secondary battery. However, the extremely high areal density increases the path of active ion solid-phase transport, which reduces the kinetic performance of the secondary battery. The kinetic additive in the embodiments of this application is suitable for electrodes with various coating methods, especially for thick-coated electrodes, so as to achieve a balance between the energy density and kinetic performance of the secondary battery.

[0097] In some embodiments, the secondary battery further includes an electrolyte comprising a first solvent and a second solvent. Optionally, the first solvent comprises ethylene carbonate (EC), and the second solvent comprises one or more of dimethyl carbonate (DMC) and propylene carbonate (PC).

[0098] Kinetic additives can regulate the solvation structure of active ions by means of their cavity diameter and surface active groups, resulting in lower solvation energy of the regulated active ions, which is more conducive to desolvation and further improves the transport efficiency of active ions in the active material layer. At the same time, it reduces the probability of the cavity being blocked by the binder in the active material layer. By means of the ion liquid phase conduction of the solvation structure, the kinetic performance of the secondary battery is improved, the DC resistance of the secondary battery is reduced, especially the DC resistance at low temperature, and the electrochemical performance of the secondary battery at high rate is improved.

[0099] [Positive electrode plate]

[0100] The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes a positive active material, a conductive agent, and a binder as described in some embodiments or a binder prepared by a preparation method as described in some embodiments.

[0101] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0102] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0103] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0104] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0106] [Electrolytes]

[0107] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0108] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0109] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0110] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0111] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0112] The second aspect of this application provides a method for preparing a negative electrode sheet, the method comprising: providing a negative electrode slurry, rolling the negative electrode slurry into a film and then laminating it onto a negative electrode current collector; drying to form a negative electrode active material layer; the negative electrode slurry includes a kinetic additive, the structure of which includes a cavity with a diameter of 0.6-1.5 nm.

[0113] This preparation method can improve the coating effect of binders and kinetic additives on the surface of negative electrode active materials through roll forming, reduce lithium consumption, improve the first efficiency of secondary batteries, and improve the kinetic and rate performance of secondary batteries. It can also increase the solid content of negative electrode slurry, reduce the moisture content that needs to be volatilized during the slurry drying process, effectively reduce drying stress, reduce the risk of cracking, meet the requirements of thick electrode sheet manufacturing, increase the areal density of negative electrode active material layer, and break through the upper limit of energy density of secondary batteries in the existing technology.

[0114] In some embodiments, the solid content of the negative electrode slurry is 60%-90%.

[0115] In some embodiments, the solid content of the negative electrode slurry can be selected as 60%, 70%, 80%, 90%, or any value between the two.

[0116] In some embodiments, the step of rolling the negative electrode slurry into a film and then laminating it onto the negative electrode current collector includes: mixing the binder and kinetic additive evenly, adding the active material to knead it into a ball, rolling it into a film, and then laminating it onto the negative electrode current collector.

[0117] Mixing the binder and kinetic additive uniformly beforehand helps improve the dispersibility of the kinetic additive in the binder, allowing them to co-coat the surface of the active material and improve the kinetic performance of the secondary battery.

[0118] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0119] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0120] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows a square-structured secondary battery 5 as an example.

[0121] In some embodiments, referring to FIG3, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 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 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0122] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0123] Figure 4 shows a battery module 4 as an example. Referring to Figure 4, in the battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can be fixed in place using fasteners.

[0124] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0125] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0126] Figures 5 and 6 show a battery pack 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0127] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, 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.

[0128] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0129] Figure 7 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0130] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0131] Example

[0132] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0133] Example

[0134] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0135] I. Preparation Method

[0136] Example 1

[0137] 1) Preparation of negative electrode sheet

[0138] The kinetic additive β-cyclodextrin (CAS: 68168-23-0) and binder PAA (polyacrylic acid) were mixed evenly in an aqueous solvent. Then, the negative electrode active material graphite and the conductive agent SP were added, and the mixture was thoroughly stirred to ensure uniform mixing. The mass ratio of the negative electrode active material graphite, conductive agent SP, PAA, and cyclodextrin in the slurry was 98:0.7:1:0.3; the solid content of the slurry was 67%. After the slurry was evenly dispersed, it was kneaded into clumps, rolled into a flexible film using a roller press, and then laminated with a current collector. After drying, the electrode sheet exhibited excellent flexibility, yielding the negative electrode sheet. The one-sided density of the negative electrode sheet was 12 mg / cm³. 2 The compacted density is 1.6 g / cm³. 3 .

[0139] 2) Preparation of positive electrode sheet

[0140] Lithium iron phosphate (the positive electrode active material), acetylene black (the conductive agent), binder, and dispersant were thoroughly mixed in NMP at a ratio of 96:2:1.5:0.5. The mixture was then coated onto Al foil, dried, and cold-pressed to obtain the positive electrode sheet. The one-sided density of the positive electrode sheet was 25.97 mg / cm³. 2 The compacted density is 1.6 g / cm³. 3 .

[0141] 3) Separating membrane

[0142] Polypropylene film is used as the separator.

[0143] 4) Preparation of electrolyte

[0144] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC), dimethyl carbonate (DMC), and propylene carbonate (PC) were mixed evenly in a volume ratio of 1:1:1. LiPF6 lithium salt was added and dissolved in the organic solvent and stirred evenly to prepare a 1M LiPF6 EC / DMC solution to obtain the electrolyte.

[0145] 5) Battery manufacturing

[0146] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound up, and the bare cell is placed in the outer packaging. The prepared electrolyte is injected, and the cell is then sealed, filled with electrolyte, formed, and vented to obtain a secondary battery.

[0147] The preparation methods of Examples 2-4 are basically the same as those of Example 1, except that the kinetic additives in Example 1 are adjusted, as shown in Table 1.

[0148] In Example 2, the kinetic auxiliary agent was dodecyl polysaccharide cyclodextrin (12-CD). The preparation method was as follows: an appropriate amount of corn starch was weighed, soaked in a small amount of anhydrous ethanol, and a certain amount of dimethyl sulfoxide (DMSO) and tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer solution was added. The mixture was then heated in boiling water for about 20 min to dissolve the starch. The pH was adjusted to 7.0 with 2 mol / L dilute HCl. Pure enzyme solution (40 U / g starch) was added, and the mixture was reacted at 70 °C for 8 h. The reaction was terminated by heating in a boiling water bath for 20 min. γ-amylase (30 U / g starch) and pullulanase (100 U / g starch) were added to the reaction solution to remove unreacted amylose. After reacting at 50 °C for 8 h, the reaction was terminated by heating in a boiling water bath for 30 min. The mixture was centrifuged at 4000 r / min for 40 min and dried at 90 °C for 12 h to obtain dodecyl polysaccharide cyclodextrin (12-CD).

[0149] In Example 3, the kinetic auxiliary was a sulfonic acid-based twelve-membered ring cyclodextrin. The preparation method involved reacting the sample from Example 2 with concentrated sulfuric acid in an ice bath. The reaction solution was then poured into water, and calcium carbonate was added to neutralize excess sulfuric acid. The mixture was filtered, washed with water, and anhydrous ethanol was added to the filtrate. After standing for 12 hours, the mixture was filtered again. The pH of the filtrate was adjusted to 10.5 with sodium carbonate, filtered again, and the pH of the filtrate was adjusted to 7 with acetic acid. The filtrate was then evaporated and concentrated. Anhydrous ethanol was added, producing a white or pale yellow precipitate. This precipitate was filtered and dried under vacuum to obtain sulfonic acid-12-CD.

[0150] In Example 4, the kinetic auxiliary was lithium-ionized carboxymethyl 12-membered ring cyclodextrin. The preparation method was as follows: the sample in Example 2 was dissolved in deionized water to prepare a 1 mol / L solution, NaOH alkaline solution was added dropwise to adjust the pH to 10, monochloroacetic acid was added dropwise to carry out a substitution reaction, and after vacuum drying for 12 h, carboxymethyl-12-CD was obtained.

[0151] The preparation methods of Examples 5-7 are basically the same as those of Example 3, except that the kinetic agent in Example 3 was subjected to lithium treatment.

[0152] In Example 5, the degree of lithiation of the kinetic agent was 20%. The preparation method was as follows: 80 parts by mass of a 50% lithium hydroxide aqueous solution and 160 parts by mass of a 90% ethanol aqueous solution were mixed and cooled to 25°C to obtain alkali liquor; 100 parts by mass of the sulfonic acid-12-CD raw material from Example 3 were uniformly mixed with the alkali liquor and subjected to an alkalization reaction; at 30°C, 0.5 parts by mass of epichlorohydrin and 100 parts by mass of a 75% chloroacetic acid ethanol aqueous solution were mixed and then uniformly mixed with the product after the alkalization reaction. After stirring and mixing for 30 minutes, the mixture was sent to an etherification reactor, and the reaction temperature was controlled at 75-80°C for 120 minutes; the obtained product was washed with an 85% ethanol aqueous solution, centrifuged, and vacuum dried to obtain sulfonic acid-12-CD with a degree of lithiation of 20%.

[0153] In Example 6, the degree of lithium substitution of the kinetic agent was 50%, and the preparation method was basically the same as that in Example 5, except that the 80 parts by mass of the lithium hydroxide aqueous solution in Example 5 was replaced with 120 parts by mass.

[0154] In Example 7, the degree of lithium substitution of the kinetic agent was 70%, and the preparation method was basically the same as that in Example 5, except that the 80 parts by mass of the lithium hydroxide aqueous solution in Example 5 was replaced with 200 parts by mass.

[0155] The preparation methods of Example 8 and Example 6 are basically the same, except that the solvent composition in the electrolyte is adjusted. In Example 8, all solvents are EC solvents.

[0156] Example 9

[0157] The preparation method of the battery in Example 9 is basically the same as that in Example 2, except that the preparation method is as follows: weigh an appropriate amount of corn starch, soak it with a small amount of anhydrous ethanol, add a certain amount of dimethyl sulfoxide (DMSO) and Tris-HCl buffer solution, and heat it in boiling water for about 20 minutes to dissolve the starch. Adjust the pH to 7.0 with 2 mol / L dilute HCl, add pure enzyme solution (40 U / g starch), react at 70°C for 8 hours, heat in a boiling water bath for 20 minutes to terminate the reaction, add γ-amylase (30 U / g starch) and pullulanase (100 U / g starch) to the reaction solution to remove unreacted amylose, react at 50°C for 4 hours, heat in a boiling water bath for 15 minutes to terminate the reaction, centrifuge at 4000 r / min for 40 minutes, and dry at 90°C for 12 hours to obtain polycyclodextrin (11-CD) powder.

[0158] Example 10

[0159] The battery preparation method in Example 10 is basically the same as that in Example 4, except that the kinetic additive in Example 4 is further lithiated using a method similar to that in Example 6 to obtain a kinetic additive with a lithiation degree of 50%.

[0160] Comparative Example 1

[0161] The preparation methods of Comparative Example 1 and Example 1 are basically the same, except that the kinetic additive in Comparative Example 1 is α-cyclodextrin.

[0162] Comparative Example 2

[0163] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the kinetic additive in Comparative Example 2 is a polycyclodextrin with a cavity diameter of 2 nm. The preparation method of polycyclodextrin is as follows: weigh an appropriate amount of corn starch, soak it with a small amount of anhydrous ethanol, add a certain amount of dimethyl sulfoxide (DMSO) and Tris-HCl buffer solution, and heat it in boiling water for about 20 min to dissolve the starch. Adjust the pH to 7.0 with 2 mol / L dilute HCl, add pure enzyme solution (60 U / g starch), react at 70 °C for 8 h, and stop the reaction by heating in a boiling water bath for 20 min. Add γ-amylase (40 U / g starch) and pullulanase (120 U / g starch) to the reaction solution to remove unreacted amylose. After reacting at 50 °C for 6 h, stop the reaction by heating in a boiling water bath for 20 min, centrifuge at 4000 r / min for 40 min, and dry in vacuum at 90 °C for 12 h to obtain polycyclodextrin (14-CD) powder.

[0164] Comparative Example 3

[0165] The preparation methods of Comparative Example 3 and Comparative Example 2 are basically the same, except that the electrolyte in Comparative Example 3 only includes ethylene carbonate (EC).

[0166] Table 1

[0167] II. Performance Testing

[0168] 1. DCR Testing Method

[0169] HPPC was used for testing at 25℃. First, the cell was discharged at a 1C rate. Then, the cell was charged at a constant current rate of 0.33C to 3.65V, and then charged at a constant voltage rate to a current of 0.05C. After that, it was left to stand for 1 hour to restore electrochemical and thermal equilibrium. The open circuit voltage (OCV) at 100% SOC was recorded. Then, it was discharged at a constant current rate of 1C to 50% SOC, left to stand for 1 hour, and the OCV1 value at 50% SOC was recorded. Then, it was discharged at 3C for 30 seconds, and the OCV2 value was recorded. The DCR value was obtained by using the formula DCR = (OCV1 - OCV2) / I.

[0170] 2. Test methods for rate performance

[0171] Using an electrochemical workstation from Shenzhen Xinwei Electronics Co., Ltd., the battery was charged at a constant current rate of 3C to 4.2V at 25℃, then charged at a constant voltage of 4.2V to a current of 0.05C, rested for 5 minutes, and then discharged at 3C to 2.5V. The discharge capacity C1 was recorded. At 25℃, the battery was charged at a constant current rate of 1 / 3C to 4.2V, then charged at a constant voltage of 4.2V to a current of 0.05C, rested for 5 minutes, and then discharged at 1 / 3C to 2.5V. The discharge capacity C2 was recorded. The ratio of C1 to C2 was used as the battery's capacity retention rate to evaluate its 3C rate performance.

[0172] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0173] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2.

[0174] Table 2

[0175] As can be seen from the comparison between the examples and the comparative examples, by adding a kinetic additive to the active material layer of the electrode, the structure of the kinetic additive includes a cavity with a diameter of 0.8nm-1.5nm, which can reduce the DC resistance of the secondary battery and improve the rate performance of the secondary battery.

[0176] As can be seen from the comparison of Examples 3-8 and 10, the presence of lithium-containing active groups in cyclodextrin can further reduce the DC resistance of secondary batteries and improve their rate performance.

[0177] As can be seen from the comparison of Examples 1, 2, and 9, when the diameter of the cyclodextrin cavity is 0.9-1.5 nm, the DC resistance of the secondary battery is further reduced and the rate performance is further improved.

[0178] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are 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 secondary battery, characterized in that, The electrode includes a current collector and an active material layer disposed on at least one side of the current collector. The active material layer includes a kinetic additive, and the kinetic additive has a cavity in its structure, the cavity having an average diameter of 0.8 nm to 1.5 nm.

2. The secondary battery according to claim 1, characterized in that, The diameter of the cavity is 0.9-1.5 nm.

3. The secondary battery according to claim 1 or 2, characterized in that, The kinetic additive includes cyclodextrin and its derivatives; the cyclodextrin includes an X-membered glycocyclic molecule, wherein X includes any integer from 7 to 12.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The kinetic additive contains an active group, which may be one or more of sulfonic acid groups and carboxyl groups.

5. The secondary battery according to claim 3, characterized in that, The kinetic additive contains an active metal-substituted active group, which may be one or more of lithium carboxylate, sodium carboxylate, lithium sulfonate, and sodium sulfonate.

6. The secondary battery according to claim 5, characterized in that, Based on the total molar content of unsubstituted and active metal-substituted active groups in the kinetic additive, wherein the molar content of active metal-substituted active groups accounts for 20%-70%.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The kinetic additive includes one or more of lithium sulfonate cyclodextrin, lithium carboxyl cyclodextrin, sodium sulfonate cyclodextrin, and sodium carboxyl cyclodextrin.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, Based on the total mass of the active material layer, the mass content of the kinetic additive is 0.1%-1%.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The active material layer further includes an adhesive, which comprises a linear polymer, including an acrylic polymer.

10. The secondary battery according to claim 9, characterized in that, Based on the total mass of the active material layer, the mass content of the adhesive is 0.5%-2.5%.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, The active material layer further includes active material, and the mass content of the active material is 95%-98.5% based on the total mass of the active material layer.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The density of the active material layer on one side is 4.5-100 mg / cm³. 2 20-30 mg / cm³ is an option. 2 .

13. The secondary battery according to any one of claims 1 to 12, characterized in that, The secondary battery further includes an electrolyte, which includes a first solvent and a second solvent. The first solvent includes ethylene carbonate (EC), and the second solvent includes one or more of dimethyl carbonate (DMC) and propylene carbonate (PC).

14. A method for preparing a negative electrode sheet, characterized in that, The preparation method includes: A negative electrode slurry is provided, which is then rolled into a film and laminated onto a negative electrode current collector; after drying, a negative electrode active material layer is formed; the negative electrode slurry includes a kinetic additive, the structure of which includes a cavity with a diameter of 0.6-1.5 nm.

15. The preparation method according to claim 14, characterized in that, The solid content of the negative electrode slurry is 60%-90%.

16. The preparation method according to claim 14 or 15, characterized in that, The step of rolling the negative electrode slurry into a film and then laminating it onto the negative electrode current collector includes: mixing the binder and kinetic additive evenly, adding the active material to knead it into a ball, rolling it into a film, and then laminating it onto the negative electrode current collector.

17. An electrical device, characterized in that, The electrical device includes a secondary battery according to any one of claims 1 to 13 or a secondary battery including a negative electrode sheet prepared by the preparation method according to any one of claims 14 to 16.

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