Binder, negative electrode and rechargeable battery including the same

Abstract

Provided are a binder for a rechargeable battery, a negative electrode comprising the binder, and a rechargeable battery comprising the binder. The binder comprises a copolymer comprising: a plurality of first components, each having a linear or branched structure, each comprising 1-1 units derived from a monovinyl aromatic monomer, 1-2 units derived from a conjugated diene monomer, and 1-3 units derived from an acrylate monomer; and a second component constituting a core node of the copolymer, derived from vinyl silsesquioxane or a derivative thereof. In the copolymer, the plurality of first components are respectively bonded to the vinyl groups of the second component.

Description

Technical Field

[0001] One or more embodiments of the present disclosure relate to a binder, and more particularly, to a binder for a rechargeable battery, a negative electrode including the binder, and a rechargeable battery including the binder. Background Art

[0002] Rechargeable lithium batteries (e.g., lithium-ion batteries) offer numerous advantages, including high energy density, long cycle life, high nominal voltage, low self-discharge rate, compact size, and light weight, making them widely used in consumer electronics. With the rapid development of electric vehicles and mobile electronic devices in recent years, demands for the safety and cycle performance of rechargeable lithium batteries are increasing, and the emergence of new rechargeable lithium batteries with comprehensively improved performance is highly anticipated.

[0003] Electrode binders are essential and crucial auxiliary functional materials in rechargeable lithium batteries. Although present in relatively low concentrations in the electrode, they are the primary contributor to the overall electrode's mechanical properties, significantly impacting both the electrode's production process and the battery's electrochemical performance, playing an irreplaceable role. Their primary function is to bond the electrode active material, conductive agent, and current collector together, shortening the lithium ion transport pathway and stabilizing the electrode material's structure.

[0004] Compared with ordinary binders, electrode binders, in addition to having bonding properties, are also required to be able to withstand the swelling and corrosion of the electrolyte, adapt to the volume changes of the electrode active material, and ensure that the lithium ion transmission pathway is not affected.

[0005] Therefore, relevant research on high-performance electrode binders is ongoing.

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute prior art. Summary of the Invention

[0007] Example embodiments of the present disclosure relate to a binder for a rechargeable battery that may improve battery performance.

[0008] Example embodiments of the present disclosure relate to a negative electrode including the binder.

[0009] Example embodiments of the present disclosure relate to a rechargeable battery including the binder.

[0010] However, the present disclosure is not limited to the above-mentioned aspects, but can be variously extended without departing from the technical spirit of the present disclosure.

[0011] Embodiments of the present disclosure provide a binder for a rechargeable battery, comprising a copolymer comprising: a plurality of first components, each having a linear or branched structure, each comprising 1-1 units derived from a monovinyl aromatic monomer, 1-2 units derived from a conjugated diene monomer, and 1-3 units derived from an acrylate monomer; and a second component constituting a core node of the copolymer, derived from vinyl silsesquioxane or a derivative thereof. In the copolymer, the plurality of first components are respectively bonded to the vinyl groups of the second component.

[0012] In an embodiment of the present disclosure, the number average molecular weight of the copolymer is in the range of about 200,000 to about 800,000.

[0013] In an embodiment of the present disclosure, the number average molecular weight of the first component is in the range of about 60,000 to about 140,000.

[0014] In an embodiment of the present disclosure, the number average molecular weight of the first component is in the range of about 80,000 to about 120,000.

[0015] In an embodiment of the present disclosure, the number average molecular weight of the first component is in the range of about 90,000 to about 110,000.

[0016] In an embodiment of the present disclosure, the first component includes block copolymers of 1-1 units, 1-2 units, and 1-3 units.

[0017] In an embodiment of the present disclosure, based on 100 wt% of the total weight of the 1-1 unit, the 1-2 unit and the 1-3 unit in the first component, the amount of the 1-1 unit is in the range of 25 wt% to 35 wt%, the amount of the 1-2 unit is in the range of 55 wt% to 65 wt%, and the amount of the 1-3 unit is in the range of 5 wt% to 15 wt%.

[0018] In an embodiment of the present disclosure, the monovinyl aromatic hydrocarbon monomer is selected from at least one of styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinyltoluene, vinylxylene, adamantylstyrene, vinylanthracene, vinylbiphenyl, and 1,1-diphenylethylene.

[0019] In an embodiment of the present disclosure, the monovinyl aromatic hydrocarbon monomer is styrene.

[0020] In an embodiment of the present disclosure, the conjugated diene monomer includes at least one of butadiene and isoprene.

[0021] In an embodiment of the present disclosure, the conjugated diene monomer is butadiene.

[0022] In an embodiment of the present disclosure, the conjugated diene monomer includes both butadiene and isoprene.

[0023] In an embodiment of the present disclosure, the content of the unit derived from the isoprene monomer may be 0 wt % to 25 wt % based on 100 wt % of the total weight of the 1-2 unit.

[0024] In an embodiment of the present disclosure, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethylhexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate.

[0025] In an embodiment of the present disclosure, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethylhexyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, and ethylhexyl (meth)acrylate.

[0026] In an embodiment of the present disclosure, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate.

[0027] In an embodiment of the present disclosure, the acrylic acid ester monomer is methyl (meth)acrylate.

[0028] In an embodiment of the present disclosure, the ratio of the amount of the first component to the amount of the second component in the copolymer is about 2:1 to about 8:1.

[0029] In an embodiment of the present disclosure, the ratio of the amount of the first component to the amount of the second component in the copolymer is about 2:1 to about 5:1.

[0030] In an embodiment of the present disclosure, the ratio of the amount of the first component to the amount of the second component in the copolymer is about 3:1 to about 4:1.

[0031] In an embodiment of the present disclosure, the ratio of the amount of the first component to the amount of the second component in the copolymer is about 3.5.

[0032] The binder further includes a cross-linking agent including units derived from aminosilsesquioxane or a derivative thereof.

[0033] In an embodiment of the present disclosure, the crosslinking agent is N-phenylamino-silsesquioxane or a derivative thereof.

[0034] In an embodiment of the present disclosure, the copolymer is cross-linked by a cross-linking agent to form a polymer having a semi-IPN structure.

[0035] In an embodiment of the present disclosure, the polymer having a semi-IPN structure includes: a network-structured polymer formed of a copolymer cross-linked by a cross-linking agent; and the copolymer independent of the network-structured polymer.

[0036] In an embodiment of the present disclosure, the weight of the cross-linking agent may be less than about 1.5% by weight of the copolymer.

[0037] In an embodiment of the present disclosure, the copolymer has a cross-linking degree of no greater than about 30%.

[0038] In an embodiment of the present disclosure, the binder does not include sodium carboxymethyl cellulose.

[0039] An embodiment of the present disclosure also provides a method for preparing a binder for a rechargeable battery, the method comprising the following steps: adding a monovinyl aromatic monomer to a solvent; adding an initiator to polymerize the monovinyl aromatic monomer to generate a chain segment composed of 1-1 units derived from the monovinyl aromatic monomer; adding a conjugated diene monomer to react with the chain segment composed of 1-1 units to generate a chain segment composed of 1-2 units derived from the conjugated diene monomer; adding an acrylate monomer to react with the chain segment composed of 1-2 units to generate a first component including 1-1 units, 1-2 units and 1-3 units derived from the acrylate monomer; adding vinyl silsesquioxane or a derivative thereof to react with the first component to generate a copolymer, the copolymer comprising multiple first components and a second component derived from vinyl silsesquioxane or a derivative thereof and constituting a core node of the copolymer, the multiple first components being respectively bonded to the vinyl groups of the one second component.

[0040] An embodiment of the present disclosure further provides a negative electrode, comprising the binder as described above.

[0041] An embodiment of the present disclosure further provides a rechargeable battery, comprising: a negative electrode as described above; a positive electrode; and a separator between the negative electrode and the positive electrode.

[0042] According to one or more embodiments, provided are a binder that can improve performance and safety of a battery, and a negative electrode and a rechargeable battery including the binder.

[0043] The effects of the present disclosure are not limited to the effects mentioned herein, and other effects will be clearly understood by those skilled in the art through the description of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are included to provide further explanation of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate example embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure.

[0045] Figure 1 is a schematic diagram showing the binding mechanism of the binder in the electrode.

[0046] Figure 2 is a schematic structural diagram illustrating a rechargeable battery according to an embodiment of the present disclosure.

[0047] Figure 3 is a schematic structural diagram illustrating an electrode assembly according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0048] The present disclosure can be modified in many alternative forms, and therefore specific embodiments will be illustrated in the drawings and described in more detail. However, it should be understood that the specific embodiments are not intended to limit the disclosure to the particular forms disclosed, but are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

[0049] Hereinafter, embodiments of the present disclosure are described in more detail. However, these embodiments are merely examples, and the present disclosure is not limited thereto, and the present disclosure is limited by the scope of the claims. The terms used herein are only used to describe the embodiments and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0050] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, when describing embodiments of the present disclosure, the use of "may" refers to "one or more embodiments of the present disclosure."

[0051] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than terms of degree, and are intended to take into account the inherent variations in measurements or calculations that those skilled in the art would recognize.

[0052] As used herein, the term "combination thereof" may refer to a mixture, laminate, composite, copolymer, alloy, blend, reaction product, or the like, of the components.

[0053] It should be understood that terms such as "include / its variations", "include / its variations" or "have / its variations" are intended to indicate the presence of the embodied features, quantities, steps, elements or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, quantities, steps, elements or combinations thereof.

[0054] In the accompanying drawings, the thickness of layers, films, panels, regions, etc. may be exaggerated for clarity, and throughout this disclosure, like reference numerals denote like elements, and for the sake of brevity, a repeated description thereof may not be provided. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element, or intervening elements may be present. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements therebetween.

[0055] "Thickness" can be measured, for example, with a micrometer or through images taken with an optical microscope (such as a scanning electron microscope).

[0056] In addition, any numerical range recited herein is intended to include all subranges of the same numerical precision contained within the recited range. For example, the range of "1.0 to 10.0" is intended to include all subranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (and including the recited minimum value of 1.0 and the recited maximum value of 10.0), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as 2.4 to 7.6. Any maximum numerical limit recited herein is intended to include all lower numerical limits contained therein, and any minimum numerical limit recited in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to amend this specification (including the claims) to explicitly recite any subranges contained within the ranges explicitly recited herein.

[0057] The "thickness" can be measured by images taken with an optical microscope or a scanning electron microscope.

[0058] Hereinafter, an adhesive according to an embodiment of the present disclosure will be described.

[0059] Embodiments of the present disclosure provide a binder for a rechargeable battery. The binder can be used in electrodes of rechargeable batteries, specifically, it can be a binder used in electrodes to adhere electrode active materials and conductive materials to current collectors. The binder can include a copolymer. That is, the main component of the binder can be solely the copolymer described below. In some embodiments, the main component of the binder can also further include other components (e.g., a crosslinker). It is understood that the binder can also include other minor components and unavoidable impurities. The copolymer includes a first component and a second component. Specifically, a copolymer macromolecule includes at least two first components and one second component. The first component has a linear or branched structure and constitutes the arms of the copolymer. The second component constitutes the core node of the copolymer. In other words, the copolymer can be a star-shaped copolymer with at least two arms. The first component includes 1-1 units derived from a monovinyl aromatic monomer, 1-2 units derived from a conjugated diene monomer, and 1-3 units derived from an acrylate monomer. The second component is derived from vinyl silsesquioxane or a derivative thereof. In some embodiments, the second component may be a moiety formed of a vinylsilsesquioxane molecule or a derivative thereof.

[0060] In some embodiments of the present disclosure, the monovinyl aromatic monomer may include at least one of styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinyltoluene, vinylxylene, adamantylstyrene, vinylanthracene, vinylbiphenyl, and 1,1-diphenylethylene.

[0061] In some embodiments of the present disclosure, the conjugated diene monomer may include butadiene and optionally isoprene.

[0062] In some embodiments of the present disclosure, the acrylic acid ester monomer may include at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethylhexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate.

[0063] In some embodiments of the present disclosure, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethylhexyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, and ethylhexyl (meth)acrylate.

[0064] In some embodiments of the present disclosure, the acrylic acid ester monomer includes at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate.

[0065] That is, the first component can be a copolymer of a monovinyl aromatic hydrocarbon, a conjugated diene, and an acrylate. The "copolymer" herein can be an alternating copolymer, a random copolymer, or a block copolymer. That is, the first component can include an alternating copolymer, a random copolymer, or a block copolymer of a monovinyl aromatic hydrocarbon, a conjugated diene, and an acrylate. In some embodiments of the present disclosure, the first component can be a block copolymer of a monovinyl aromatic hydrocarbon, a conjugated diene, and an acrylate.

[0066] The following description may involve theoretical foundations for the excellent effects of the adhesives according to some embodiments of the present disclosure. It should be understood that these theoretical foundations are merely intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure in any way. In other words, the effects of the adhesives of the present disclosure are not limited by these theoretical foundations, that is, they may not be based on these theoretical foundations, but may also be based on theoretical foundations other than these theoretical foundations.

[0067] In the prior art, conventional lithium ion electrode binders mainly include polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR) polymers, fluorinated rubber, polyurethane, polyacrylic acid etc. Wherein, SBR binder is widely used in lithium ion batteries due to stable performance and price advantage. The SBR used in this area is usually formed by free radical emulsion polymerization, and it is a random copolymer of styrene and butadiene.

[0068] However, SBR easily swells in electrolyte, and if SBR is used alone as a binding agent, it will be difficult to prepare slurry, because SBR does not have a suspension dispersion function, and slurry will settle. Therefore, sodium carboxymethyl cellulose (CMC) is usually used in conjunction with SBR in this area as an electrode binder. However, CMC has a larger defect of brittleness, including the electrode active material layer of the binding agent made using it is easy to crack during the charge and discharge of the battery. Especially when there is a larger volume change in electrode material during battery charge and discharge, the binding agent comprising CMC is more likely to cause an increase in the risk of electrode active material layer rupture.

[0069] In recent years, silicon-based anode materials (i.e., Si-based active materials) have attracted attention due to their higher theoretical capacity. However, while silicon-based anode materials can significantly increase the energy density of lithium batteries, they produce large volume changes associated with the insertion and deinsertion of lithium. As a result, the electrode active material layer will significantly expand and contract during charging and discharging, which can lead to degradation of electrode performance.

[0070] Therefore, if the CMC-SBR combination binder is applied to an electrode using a silicon-based negative electrode material, the risk of rupture of the electrode active material layer due to the greater brittleness of CMC will be more prominent when there is a relatively large volume change in the electrode active material layer. However, as mentioned above, if SBR is used alone as a binder, it will be difficult to prepare the slurry because SBR does not have the suspension and dispersion function and the slurry will settle. Moreover, SBR easily swells in the electrolyte. When the volume of the silicon-based negative electrode material expands, the volume of the electrode active material layer will also expand more significantly, which will cause the volume of the electrode assembly to increase significantly, affecting battery performance and posing a safety hazard.

[0071] In the embodiments of the present disclosure, a block copolymer of a monovinyl aromatic monomer, a conjugated diene monomer, and an acrylate monomer is formed by anionic polymerization. This block copolymer is then anionic polymerized with vinyl silsesquioxane or a derivative thereof to form a copolymer comprising a first component and a second component. The first component comprises 1-1 units derived from the monovinyl aromatic monomer, 1-2 units derived from the conjugated diene monomer, and 1-3 units derived from the acrylate monomer, while the second component is derived from vinyl silsesquioxane or a derivative thereof.

[0072] As a result, an acrylate with a polar group can be introduced into the first component of the copolymer. This acrylate can form strong hydrogen bonds with the electrode active material containing groups such as hydroxyl groups on its surface, thereby effectively suppressing the volume expansion of the silicon negative electrode material. In addition, the polar group can also promote the formation of a denser film in the electrode sheet, increasing the electrical contact between the active material and the current collector, thereby improving the electrical performance of the negative electrode.

[0073] In addition, the copolymer disclosed herein is a star-shaped copolymer with a first component as an arm and a second component as a core, wherein the first component includes 1-1 units derived from monovinyl aromatic monomers, 1-2 units derived from conjugated diene monomers, and 1-3 units derived from acrylate monomers, and the second component is derived from vinyl silsesquioxane or its derivatives.

[0074] In some embodiments of the present disclosure, the vinyl silsesquioxane or a derivative thereof may be, for example, octavinyl silsesquioxane or a derivative thereof.

[0075] Silsesquioxane refers to polyhedral oligomeric silsesquioxane, a new type of organic-inorganic hybrid nanomaterial. Its internal inorganic framework is a hexahedral cage structure composed of Si-O-Si or Si-O bonds. Each corner contains a Si atom, and each face is composed of a Si-O-Si octahedral ring. It has a strong structural symmetry. Each Si atom on the outside can carry a variety of organic groups. Therefore, the more typical molecular formula can be described as (CH3SiO 1.5 )n, n is usually 8, but can also be 10 and 12, and R can be H and active or inactive groups, such as epoxy, amino, carboxyl, alkenyl, alkyl, hydroxyl, aryl, etc. The structure of a typical cage-type polyhedral oligomeric silsesquioxane is shown in Formula 1 below.

[0076] [Formula 1]

[0077]

[0078] When R in Formula 1 is a vinyl group, it is vinyl silsesquioxane. Specifically, when all R groups are vinyl groups, it is octavinyl silsesquioxane. In an embodiment of the present disclosure, a portion (e.g., two or more) of R groups in Formula 1 may be vinyl groups, and the other R groups in Formula 1 may be H or other groups.

[0079] For the copolymer of monovinyl aromatic hydrocarbon monomers, conjugated diene monomers and acrylate monomers, the unsaturated double bond at the chain end can undergo addition reaction with the vinyl group of vinyl silsesquioxane in the presence of an anionic polymerization active center, thereby combining the chain copolymer of monovinyl aromatic hydrocarbon and conjugated diene monomers with vinyl silsesquioxane.

[0080] Therefore, in the embodiments disclosed herein, a monovinyl aromatic hydrocarbon, a conjugated diene, and an acrylate are first copolymerized via living anionic polymerization to form a first component, which will serve as an arm. Then, in the presence of an active center, the first component is subjected to an addition reaction with a vinyl silsesquioxane, which will serve as a second component, to form a copolymer comprising the first component and the second component. This preparation method will be described in further detail below.

[0081] In the following description, for the sake of simplicity, styrene is used as an example of a monovinyl aromatic hydrocarbon monomer, butadiene and / or isoprene are used as examples of a conjugated diene monomer, and methyl (meth)acrylate is used as an example of an acrylate monomer. It will be understood that the present disclosure is not limited thereto, and other types of monovinyl aromatic hydrocarbons and other types of acrylates as described above are also applicable to the inventive concept of the present disclosure.

[0082] The copolymer with the above structure can first improve the problem that SBR is easily swollen in the electrolyte. Since silsesquioxane has a solid three-dimensional structure, it can improve the volume stability and structural stability of the copolymer. In addition, since silsesquioxane has a more stable and solid structure, it can tightly connect multiple long-chain first components together, avoiding the problem that the chain segments of the first component are too long and easily broken or entangled under the same molecular weight, so the copolymer with vinyl silsesquioxane as the core can have a toughness better than that of simple chain SBR. Especially when applied to a silicon-based negative electrode with a large volume change, the copolymer with vinyl silsesquioxane as the core of the embodiment of the present disclosure can avoid the molecular chain breakage caused by the excessive length of the molecular chain segment.

[0083] Secondly, silsesquioxane has a cage structure, so the copolymer disclosed in the present invention can improve the electrolyte absorption capacity of the binder through the cage structure of silsesquioxane, thereby facilitating the migration of lithium ions in the electrode.

[0084] The main function of the binder in the electrode is to bind the electrode active material, conductive agent and other components in the electrode active material layer to the metal current collector. Figure 1 A schematic diagram of the binder mechanism is shown. Figure 1 As shown in Figure 2, the mechanism of action of the binder can be understood as follows: the chain-like polymer binder binds the spherical electrode active material like a "rope" and fixes it to the metal current collector. Figure 1 From a theoretical perspective, if the binder is simply a linear polymer, its ability to fix the electrode active material is relatively weak. In this application, the copolymer in the binder can be a star-shaped polymer comprising a first component and a second component. This copolymer structure, when spread over the electrode active material, can act like a "net," firmly fixing the electrode active material.

[0085] Although some linear polymers can generate some "binding points" with each other to form a network-like structure, such "binding points" are easily disconnected under the frequent volume changes of the electrode active material, resulting in degradation of the adhesion of the binder. In an embodiment of the present application, the bond between the first component and the second component that are mutually bonded by the addition reaction is relatively more stable and not easy to break. In addition, the second component derived from vinyl silsesquioxane has a strong three-dimensional structure, which can tightly connect the first component to which it is bonded like a "knot" and at the same time firmly fix the electrode active material to which it is attached. Therefore, compared with SBR binders and CMC-SBR binders, the binder disclosed in the present invention can have better stability, can prevent the electrode active material from undergoing excessive changes in structure and volume during the charge and discharge process, prevent the electrode active material from falling off, and improve the cycle stability of the electrode.

[0086] As described above, silsesquioxanes can have multiple (e.g., 12 or 8) reactive groups. Therefore, in the case of octavinylsilsesquioxane, theoretically, 8 first components can be combined with 1 second component. That is, in some embodiments of the present disclosure, the copolymer can include 2 to 8 first components and 1 second component. In other words, in some embodiments of the present disclosure, the ratio of the number of first components to the number of second components in the copolymer can be 2:1 to 8:1.

[0087] In some embodiments of the present disclosure, the ratio of the number of the first component to the second component in the copolymer can be 2:1 to 5:1. That is, the number of arms of the copolymer is in the range of 2 to 5. It will be understood that the range of 2:1 to 5:1 here refers to the ratio calculated by gel permeation chromatography (GPC) testing. That is, when a large number of copolymer macromolecules are used as a reference, the ratio of the number of the first component to the second component is 2:1 to 5:1. It will be understood that in some (very small) individual copolymer molecules, the ratio of the number of the first component to the second component may be outside the range of 2:1 to 5:1. For the vast majority of individual copolymer molecules, the ratio of the number of the first component to the second component is 2:1 to 5:1. That is, for the vast majority of individual copolymer molecules, they may have 2, 3, 4, or 5 arms, that is, the ratio of the number of the first component to the second component is 2, 3, 4, or 5. Of course, if calculated based on a large number of copolymer molecules, the ratio of the number of the first component to the second component can be any value between 2 and 5 (that is, it does not have to be an integer).

[0088] In some embodiments of the present invention, the ratio of the number of the first component to the second component in the copolymer is 2:1 to 5:1, specifically, 2.5:1 to 4.5:1, more specifically, 3:1 to 4:1, and more specifically, 3.5: 1. That is, in some embodiments of the present invention, the vast majority of copolymer macromolecules may have one second component and two to five first components, more specifically, one second component and three or four first components.

[0089] Copolymers with this structure can better exert structural stability while ensuring the electrical properties of the electrode. As mentioned above, the copolymer in the binder of the present invention can fix the electrode active material like a "net". In this case, if the number of first components in the copolymer is less than 2, the copolymer is more like a linear polymer, and it is difficult to achieve the "net" effect. On the contrary, if the number of first components in the copolymer is too much, that is, greater than 5, the movement space of the first component will be limited due to the steric effect, which will cause some chain-like first components to be difficult to wrap around the electrode active material well. On the one hand, this will make it difficult for this part of the first component to play its role as a binder, resulting in a waste of material; on the other hand, too many first components will hinder the lithium ion transmission channel, resulting in deterioration of the electrical properties of the electrode.

[0090] In addition, in order to ensure that the binder has good adhesion and is suitable for preparing active material slurry, the copolymer is required to have a suitable molecular weight and the chain-like first component is required to have a suitable length. Therefore, if the amount of the first component in the copolymer is too large, then in order to control the molecular weight of the copolymer from being too large, the length of the molecular chain of the first component must be shortened, which may lead to a decrease in the adhesion of the binder. On the contrary, if the appropriate length of the first component is met, the molecular weight of the copolymer will be too large, making it difficult to dissolve in the solvent during the preparation of the active material slurry, and the prepared electrode active material layer will also be prone to cracks.

[0091] In some embodiments of the present disclosure, the number average molecular weight Mn of the first component may be in the range of about 60,000 to about 140,000. When the number average molecular weight of the first component is within the above range, the copolymer comprising it may exhibit excellent bonding properties. If the number average molecular weight Mn of the first component is less than 60,000, the molecular chain formed thereby is shorter, and the entanglement effect on the electrode active material is weaker, and in particular, the viscosity of the copolymer formed thereby is too low, resulting in poor bonding of the binder. If the number average molecular weight Mn of the first component is greater than 140,000, the copolymer constituted thereby is difficult to dissolve in a solvent when preparing a slurry of the negative electrode active material composition, which increases the difficulty of the preparation process, and excessively long molecular chain segments also increase the internal resistance of the battery.

[0092] More specifically, in some embodiments of the present disclosure, the number average molecular weight Mn of the first component may be about 70,000 to about 130,000, about 80,000 to about 120,000, about 90,000 to about 110,000, or about 100,000.

[0093] In some embodiments of the present disclosure, the number average molecular weight Mn of the copolymer including the first component and the second component may be about 200,000 to about 800,000. When the number average molecular weight of the copolymer is within the above range, it may exhibit excellent bonding properties. If the number average molecular weight Mn of the copolymer is less than 200,000, the viscosity of the copolymer composed thereof is too low, resulting in poor bonding of the binder. If the number average molecular weight Mn of the copolymer is greater than 800,000, the copolymer composed thereof is difficult to dissolve in the solvent when preparing the slurry of the negative electrode active material composition, increasing the difficulty of the preparation process; and the electrode active material layer including the copolymer is prone to cracking.

[0094] More specifically, in some embodiments of the present disclosure, the number average molecular weight Mn of the copolymer including the first component and the second component can be about 200,000 to about 800,000, about 250,000 to about 600,000, about 300,000 to about 400,000, or about 350,000.

[0095] That is, in some embodiments of the present disclosure, by setting the molecular weight of the first component, the ratio of the number of the first component to the second component, and the molecular weight of the copolymer within appropriate ranges, the performance of the binder can be effectively improved. For example, in some embodiments of the present application, the ratio of the number of the first component to the second component in the copolymer is 3:1 to 4:1, the number average molecular weight Mn of the first component is about 90,000 to about 110,000, and the number average molecular weight Mn of the copolymer is about 300,000 to about 400,000. Within the above ranges, the binder can exhibit excellent bonding strength and other properties.

[0096] In some embodiments of the present disclosure, the first component includes a block copolymer of 1-1 units, 1-2 units and 1-3 units. In this case, the 1-1 unit derived from the monovinyl aromatic monomer forms a hard block to provide strength; the 1-2 unit derived from the conjugated diene monomer forms a soft block to provide elasticity and adhesion. In addition, the 1-3 unit derived from the acrylate monomer can form a strong hydrogen bond with the electrode active material containing groups such as hydroxyl groups on the surface, thereby effectively suppressing the volume expansion of the silicon negative electrode material. In addition, the polar group can also promote the formation of a denser film in the electrode sheet, increase the electrical contact between the active material and the current collector, and thus improve the electrical performance of the negative electrode.

[0097] As described above, the first component of the present invention is formed by living anionic polymerization. For example, a monovinyl aromatic hydrocarbon can be first homopolymerized, and then a conjugated diene monomer can be added to form a block copolymer of the monovinyl aromatic hydrocarbon homopolymer and the conjugated diene monomer. Then, an acrylate monomer can be added to form a block copolymer with the monovinyl aromatic hydrocarbon and the conjugated diene monomer.

[0098] Alternatively, the monovinyl aromatic hydrocarbon and the conjugated diene can be added simultaneously during polymerization. In this case, the order of polymerization of the monovinyl aromatic hydrocarbon and the conjugated diene will vary due to their different reactivity ratios. Typically, the monovinyl aromatic hydrocarbon will first react with the initiator to form an active center, and then the monovinyl aromatic hydrocarbon will polymerize into chains, forming blocks consisting essentially of the monovinyl aromatic hydrocarbon. Acrylic acid ester monomers are then added to form block copolymers with the monovinyl aromatic hydrocarbon and the conjugated diene.

[0099] Afterwards, vinyl silsesquioxane or its derivatives may be added while maintaining the active center, so that the first component undergoes an addition reaction with the first component to form a copolymer.

[0100] The first component having the above structure can further improve the mechanical properties of the copolymer, thereby making the adhesive of the present disclosure have better bonding properties.

[0101] In some embodiments of the present disclosure, based on 100 wt% of the total weight of the 1-1 unit, the 1-2 unit and the 1-3 unit in the first component, the amount of the 1-1 unit is in the range of 25 wt% to 35 wt%, the amount of the 1-2 unit is in the range of 55 wt% to 65 wt%, and the amount of the 1-3 unit is in the range of 5 wt% to 15 wt%.

[0102] When the contents of 1-1 units, 1-2 units, and 1-3 units in the first component are within the above ranges, the copolymer can have excellent adhesion, elasticity, and strength. If the content of 1-1 units is less than 25wt% or the content of 1-2 units is greater than 65wt%, the hard block content in the first component is too low, resulting in insufficient strength and poor structural stability of the electrode. If the content of 1-1 units is greater than 35wt% or the content of 1-2 units is less than 55wt%, the soft block content in the first component is too low, resulting in poor adhesion, excessive rigidity of the copolymer, and poor elasticity. If the content of 1-3 units is less than 5wt%, the effect of suppressing the volume expansion of the negative electrode and improving the electrical performance of the negative electrode by introducing acrylates cannot be well achieved. If the content of 1-3 units is greater than 15wt%, the toughness of the copolymer will deteriorate, resulting in poor windability of the electrode active material layer, leading to cracking and other phenomena during electrode manufacturing, increasing the difficulty of the preparation process.

[0103] In addition, since the monomers can be substantially completely reacted in the polymerization reaction of the present disclosure, the weight percentages of the above-mentioned 1-1 units, 1-2 units, and 1-3 units in the first component are substantially the same as the weight percentages of the 1-1 units, 1-2 units, and 1-3 units added when preparing the first component. In other words, throughout the present disclosure, the weight percentages of the various components or units in the copolymer can be regarded as being equal to the weight percentages of the various components or corresponding monomers added when preparing the copolymer.

[0104] In some embodiments of the present disclosure, the 1-2 unit may include a unit derived from a butadiene monomer and optionally a unit derived from an isoprene monomer. That is, the block formed by the 1-2 unit (i.e., the conjugated diene block) may be a block formed by butadiene, or a block formed by butadiene and isoprene, that is, a random chain, an alternating chain, or a block chain of butadiene and isoprene.

[0105] In some embodiments of the present disclosure, the content of the unit derived from isoprene monomer may be 0 wt% to 25% based on the total weight of the 1-2 units. If the content of the unit derived from isoprene monomer exceeds 25%, it will adversely affect the adhesion of the adhesive.

[0106] In some embodiments of the present disclosure, the binder may further include a crosslinking agent, and the crosslinking agent may include units of aminosilsesquioxane or its derivatives. For example, the crosslinking agent may be N-phenylamino-silsesquioxane or its derivatives.

[0107] The copolymer is cross-linked by a cross-linking agent to form a polymer having a semi-interpenetrating polymer network structure.

[0108] The polymer having a semi-interpenetrating polymer network structure includes: a network-structured polymer formed of a copolymer cross-linked by a cross-linking agent; and a copolymer independent of the network-structured polymer.

[0109] For example, the polymer having a semi-interpenetrating polymer network (semi-IPN) structure may include a network-structured polymer formed by cross-linking copolymers by a cross-linking agent, and a copolymer independent of the network-structured polymer.

[0110] Since the copolymer is cross-linked with the cross-linking agent to form a polymer having a semi-interpenetrating polymer network structure, the adhesion, mechanical properties, chemical resistance, swelling resistance, etc. of the adhesive can be improved compared with the existence of the copolymer alone.

[0111] In some embodiments of the present disclosure, the weight of the cross-linking agent can be less than about 1.5% by weight of the copolymer. Specifically, the weight of the cross-linking agent can be less than 1.2%, less than 1.0%, less than 0.8%, less than 0.6%, less than 0.4%, less than 0.2%, less than 0.1%, or less than 0.05% by weight of the copolymer.

[0112] In some embodiments of the present disclosure, the crosslinking degree of the copolymer (or binder) is not higher than about 40%. Since it is not necessary to use too much crosslinking agent, for example, as described above, the weight of the crosslinking agent can be less than 1.5% of the weight of the copolymer. Therefore, the crosslinking degree of the copolymer of the present disclosure is within the range of about 40% or less. If the crosslinking degree of the copolymer is higher than 40%, the stiffness of the binder is too high, making it difficult to prepare the negative electrode slurry.

[0113] In some embodiments of the present disclosure, the degree of crosslinking of the copolymer is in the range of about 5% to about 35%, in the range of about 10% to about 30%, in the range of about 15% to about 25%, in the range of about 18% to about 22%, or about 20%.

[0114] Furthermore, the inventors have discovered that when the ratio of the first component to the second component in the copolymer is in the range of 2:1 to 5:1 or in the range of 3:1 to 4:1, the binder comprising the copolymer and the crosslinker exhibits relatively superior performance. This may be because when the copolymer has a structure of 2 to 5 arms or 3 to 4 arms, it can more suitably form a semi-IPN structure with the crosslinker.

[0115] The disclosed embodiment also provides a method for preparing a binder for a rechargeable battery, the method comprising the following steps: adding a monovinyl aromatic monomer to a solvent; adding an initiator to polymerize the monovinyl aromatic monomer to generate a chain segment composed of 1-1 units derived from the monovinyl aromatic monomer; adding a conjugated diene monomer to react with the chain segment composed of 1-1 units to generate a chain segment composed of 1-2 units derived from the conjugated diene monomer; adding an acrylate monomer to react with the chain segment composed of 1-2 units to generate a first component including 1-1 units, 1-2 units and 1-3 units derived from the acrylate monomer; adding vinyl silsesquioxane or a derivative thereof to react with the first component to generate a copolymer, the copolymer comprising multiple first components and a second component derived from vinyl silsesquioxane or a derivative thereof and constituting a core node of the copolymer, the multiple first components being respectively bonded to the vinyl group of one second component.

[0116] Alternatively, the monovinylarene and conjugated diene monomers can be added simultaneously to a solvent, and then an initiator is added to initiate the polymerization reaction. In this case, the polymerization sequence of the monovinylarene and conjugated diene monomers may be different due to the difference in their reactivity ratios.

[0117] The copolymers in the adhesive disclosed herein can be prepared by living anionic polymerization. Specifically, living anionic polymerization can be carried out using a Schlenk system under anhydrous and anaerobic conditions. Anionic polymerization initiators and suitable solvents known in the art can be used. For example, monovinyl aromatic monomers are added to a solvent according to a predetermined ratio, maintained in anhydrous and anaerobic conditions, and then an appropriate amount of initiator can be added according to the desired molecular weight. Here, the appropriate amount of initiator includes the effective amount of initiator added as well as the amount of initiator used to remove residual water and oxygen in the reaction system. In other words, in this disclosure, "effective amount added" refers to the amount of initiator or monomer that ultimately participates in the polymerization reaction. At a suitable temperature, the monovinyl aromatic monomers and conjugated diene monomers undergo anionic polymerization under the initiator's priming to form a block copolymer, i.e., the first component. Acrylate monomers can then be added to the block copolymer of monovinyl aromatic monomers and conjugated diene monomers through anionic polymerization to form a three-component block copolymer, i.e., the first component. After the first reaction is complete, an appropriate amount of vinyl silsesquioxane or its derivative can be added as the second component, based on the predetermined ratio of the first component to the second component. Because the first component contains anionic active centers, the vinyl silsesquioxane or its derivative can continue to undergo an addition reaction with the first component to form a copolymer comprising the first and second components. After the reaction is complete, a terminator can be added to terminate the reaction.

[0118] In some embodiments of the present disclosure, the effective amount of the initiator is about 2 to about 8 times, about 2 to about 5 times, about 3 to about 4 times, or about 3.5 times the effective amount of vinyl silsesquioxane or its derivative.

[0119] In some embodiments of the present disclosure, when the binder further includes a crosslinking agent, the copolymer and the crosslinking agent may be mixed to obtain the binder. Specifically, the copolymer and the crosslinking agent may be mixed using interpenetrating network polymer preparation technology, and a suitable initiator may be added to partially crosslink the copolymer and the crosslinking agent to prepare the binder.

[0120] Hereinafter, a rechargeable battery according to an embodiment of the present disclosure will be described.

[0121] like Figure 2 As shown, embodiments of the present disclosure further provide a rechargeable battery 1, which may include an electrode assembly 10 comprising a positive electrode 20; a negative electrode 30; and a separator 40 disposed between the positive electrode 2 and the negative electrode 30; an electrolyte (not shown) in which the electrode assembly 10 is immersed; and a case 50 containing the electrode assembly 10 and the electrolyte. The rechargeable battery 1 may further include a battery cover 60 that seals the case 50.

[0122] like Figure 3 As shown, the negative electrode 30 includes a negative electrode current collector 31 and a negative electrode active material layer 32 formed on the negative electrode current collector 31. The positive electrode 20 includes a positive electrode current collector 21 and a positive electrode active material layer 22 formed on the positive electrode current collector 21. At least one of the negative electrode active material layer 32 and the positive electrode active material layer 22 includes the binder for rechargeable batteries described above. In some embodiments of the present disclosure, the negative electrode active material layer includes the binder for rechargeable batteries described above.

[0123] Hereinafter, a rechargeable battery according to an embodiment of the present disclosure will be further described.

[0124] According to an embodiment of the present disclosure, the negative electrode 30 for a rechargeable battery includes a negative electrode current collector 31 and a negative electrode active material layer 32 formed on the negative electrode current collector 31 .

[0125] The material of the negative electrode current collector 31 is not particularly limited, and may be, for example, copper foil.

[0126] The negative electrode active material layer 32 includes the binder described above, a negative electrode active material, and a conductive agent.

[0127] According to an embodiment of the present disclosure, based on the total weight of 100wt% of the negative electrode active material layer, the content of the binder can be in the range of about 0.5wt% to about 6wt%, further, in the range of about 0.65wt% to about 4wt%, further, in the range of about 0.8wt% to about 3wt%, further, in the range of about 1wt% to about 2.5wt%, further, in the range of about 1.5wt%. When the content of the binder is greater than or equal to greater than 0.5wt%, a negative electrode having excellent close contact properties and capable of suppressing the expansion of the negative electrode to have good cycle performance can be obtained. On the other hand, when the content of the binder is less than or equal to greater than 6wt%, the cycle performance of the battery can be improved without excessively increasing the electrode resistance.

[0128] The conductive agent may include at least one of the following: carbon materials such as carbon black, fine graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal materials such as copper, nickel, aluminum, or silver metal powders, metal fibers, or metal tubes; and conductive polymers such as polyphenylene derivatives. However, the present disclosure is not limited thereto, and any conductive agent may be used as long as it is commonly used in the art.

[0129] Based on the total weight of the negative electrode active material layer at 100 wt%, the content of the conductive agent can be in the range of about 1 wt% to about 10 wt%, and further, can be in the range of about 1 wt% to about 5 wt%. When the content of the conductive agent in the negative electrode active material layer is within the above range, the negative electrode can have improved conductivity, and a lithium battery including the negative electrode can have improved cycle characteristics.

[0130] The negative electrode active material can include an active material containing silicon atoms. Examples of the active material containing silicon atoms can include silicon microparticles, silicon oxide (SiO x (0 < x ≤ 2)), a composite material of silicon oxide and conductive carbon, a composite material of a silicon-containing material and conductive carbon, and an alloy containing silicon (for example, an alloy material of silicon and aluminum). That is, in some embodiments of the present application, the negative electrode active material can be a silicon-based negative electrode active material.

[0131] Based on the total weight of the negative electrode active material layer at 100 wt%, the content of the negative electrode active material can be in the range of about 82 wt% to about 98 wt%, and further, can be in the range of about 90 wt% to about 97 wt%, and still further, can be in the range of about 94 wt% to about 96 wt%.

[0132] When the content of the negative electrode active material is greater than or equal to about 82 wt%, the electrode resistance will not increase excessively, and a negative electrode with good cycle performance can be obtained. At the same time, when the content of the negative electrode active material is less than or equal to about 98 wt%, a negative electrode with excellent close contact properties and good cycle performance can be obtained.

[0133] For example, the negative electrode 30 can be manufactured by the following manufacturing method. The negative electrode active material, the conductive agent, and the binder are dry-mixed to prepare a negative electrode material mixture. Subsequently, the negative electrode material mixture is dispersed in a suitable organic solvent to prepare a negative electrode material mixture slurry, and the prepared negative electrode material mixture slurry is coated on the negative electrode current collector 31, and dried and pressed to prepare a negative electrode 30 including a negative electrode active material layer 32 and a negative electrode current collector 31.

[0134] The negative electrode for a rechargeable battery according to an embodiment of the present disclosure includes the above-mentioned binder and negative electrode active material. Therefore, a negative electrode with improved cycle characteristics while maintaining good close contact properties can be obtained.

[0135] According to an embodiment of the present disclosure, the positive electrode 20 for a rechargeable battery includes a positive electrode current collector 21 and a positive electrode active material layer 22 formed on the positive electrode current collector 21, and the positive electrode active material layer 22 includes a positive electrode active material, a conductive agent, and a binder.

[0136] The positive electrode active material is not particularly limited as long as it is a solid-solution oxide including lithium, for example, a material capable of electrochemically inserting and extracting lithium ions. The solid-solution oxide may include, for example, Li a Mn x Co y Ni z O2 (1.15≤a≤1.43, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), LiMn x Co y Ni z O2(0.3≤x≤0.85, 0.10≤y≤0.3, 0.10≤z≤0.3), LiMn 1.5 Ni 0.5 O4, etc.

[0137] The conductive agent may be the same as the conductive agent of the negative electrode described above.

[0138] The binder for the positive electrode may be, for example, polyvinylidene fluoride, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc. The positive electrode binder is not particularly limited as long as it can bind the positive electrode active material and the conductive agent to the positive electrode current collector.

[0139] For example, the positive electrode 20 can be manufactured by the following manufacturing method. A positive electrode active material, a conductive agent, and a positive electrode binder are dry-mixed to prepare a positive electrode material mixture. Subsequently, the positive electrode material mixture is dispersed in a suitable organic solvent to prepare a positive electrode material mixture slurry, and the prepared positive electrode material mixture slurry is coated on the positive electrode current collector 21, dried, and pressed to prepare a positive electrode including the positive electrode active material layer 22 and the positive electrode current collector 21.

[0140] The separator 40 is not particularly limited, and may be any separator commonly used in a rechargeable lithium battery, which can separate the positive electrode 20 from the negative electrode 30 and provide a transfer path for lithium ions.

[0141] For example, the diaphragm 40 can have low resistance to ion transport and excellent or suitable impregnation for the electrolyte solution. For example, in one or more embodiments, the diaphragm can be selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene or a combination thereof. In some embodiments, the diaphragm can have the form of a non-woven fabric or a woven fabric. For example, in some embodiments, in lithium-ion batteries, polyolefin polymers (such as polyethylene and polypropylene) diaphragms can be mainly used. In order to ensure heat resistance or mechanical strength, a coated diaphragm including a ceramic component or a polymer material can be used. In some embodiments, the diaphragm can have a single layer or multilayer structure.

[0142] The electrolyte is not particularly limited. The electrolyte may be, for example, an organic electrolyte. For example, an organic electrolyte is prepared by dissolving a lithium salt in an organic solvent.

[0143] As organic solvent, any organic solvent can be used as long as it is used in this area. The organic solvent can be, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, gamma-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, ethylene dichloride, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or its mixture.

[0144] As the lithium salt, any lithium salt can be used as long as it is used in the art. The lithium salt can be, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (1≤x≤20, 1≤y≤20), LiCl, LiI or a mixture thereof.

[0145] The adhesive of the present disclosure and the rechargeable battery including the adhesive will be further described below with reference to specific examples.

[0146] Example 1

[0147] (Preparation of Adhesive)

[0148] Prepare a dehydrated and deoxygenated environment using a Schlenk system. Add 300 g of cyclohexane, 10 g of tetrahydrofuran, and 9 g of styrene to a 2 L reaction flask with electromagnetic stirring. Stir evenly. Slowly add n-butyl lithium to the solution dropwise using a syringe until the solution turns slightly yellow and no longer disappears. Then, heat to 50 °C and add 0.3 × 10 -3 mol n-butyl lithium to initiate the polymerization reaction. After 1 hour of reaction, 18g of butadiene after impurity removal was introduced into the reaction solution, the temperature was maintained at 50°C, and the reaction was continued for 2 hours. 2g of 1,1-diphenylethylene was added, 2-(2-methoxyethoxy)ethoxylithium (LiOEEM) was added as a complexing agent, and 260g of tetrahydrofuran was added at the same time. The reaction system was cooled with liquid nitrogen, 3g of methyl (meth)acrylate after impurity removal was added, and the reaction was continued for 1 hour. Next, the temperature was raised to 70°C, and 0.086×10 -3 The octavinylsilsesquioxane after impurity removal was subjected to coupling reaction. After the reaction for 2 hours, isopropanol was added to terminate the reaction (the molar ratio of isopropanol to n-butyl lithium was 1:1) to obtain a copolymer.

[0149] The reaction solution was poured into ethanol for precipitation to obtain a white gel-like copolymer as a binder.

[0150] The molecular weight of the copolymer was measured by GPC. The number average molecular weight of the first component was about 99,000, the number average molecular weight of the copolymer was about 351,000, and the ratio of the first component to the second component in the copolymer was about 3.55.

[0151] (Manufacturing of negative electrode)

[0152] A silicon-based negative electrode active material (silicon content: 60 wt%), graphite, and the aforementioned binder were mixed with toluene in a weight ratio of 96:2:2 to form a negative electrode slurry with a solid content of 40 wt%, and stirred evenly. The negative electrode slurry was evenly coated on one surface of a 10 μm thick negative electrode current collector copper foil, dried at room temperature, and then vacuum-dried again at 120°C and pressed to prepare the negative electrode.

[0153] (Manufacturing of positive electrode)

[0154] LiNi 0.91 Co 0.05 Al 0.04 O2, acetylene black, and polyvinylidene fluoride were dispersed in N-methylpyrrolidone (NMP) solvent at a solid weight ratio of 97:1.4:1.6 to prepare a slurry with a solid content of 45wt%, and stirred evenly. The positive electrode slurry was evenly coated on one surface of a 10μm thick positive electrode current collector aluminum foil, dried at room temperature, and then dried again at 120°C under vacuum conditions and pressed to prepare the positive electrode.

[0155] (Manufacturing of diaphragms)

[0156] A polypropylene septum (Celgard 3510) was used as the septum.

[0157] (Manufacturing of Electrolyte)

[0158] 1.15 M LiPF6 was dissolved in ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and ethyl propionate (EP) (volume ratio of 3:1:1:3) to obtain an electrolyte.

[0159] (Manufacturing of coin-cell batteries)

[0160] A coin cell was fabricated using the positive and negative electrodes, separator, and electrolyte prepared as described above.

[0161] Example 2

[0162] In addition to adding 0.15×10 -3 A coin cell was manufactured in the same manner as in Example 1 except that 1 mol of octavinylsilsesquioxane was used for the coupling reaction.

[0163] Example 3

[0164] In addition to adding 0.1×10 -3 A coin cell was manufactured in the same manner as in Example 1 except that 1 mol of octavinylsilsesquioxane was used for the coupling reaction.

[0165] Example 4

[0166] In addition to adding 0.075×10 -3 A coin cell was manufactured in the same manner as in Example 1 except that 1 mol of octavinylsilsesquioxane was used for the coupling reaction.

[0167] Example 5

[0168] In addition to adding 0.06×10 -3 A coin cell was manufactured in the same manner as in Example 1 except that 1 mol of octavinylsilsesquioxane was used for the coupling reaction.

[0169] Example 6

[0170] In addition to adding 0.037×10 -3 A coin cell was manufactured in the same manner as in Example 1 except that 1 mol of octavinylsilsesquioxane was used for the coupling reaction.

[0171] Example 7

[0172] A coin cell was manufactured in the same manner as in Example 1, except that the amount of butadiene added was adjusted to 16.2 g, and 1.8 g of isoprene was added simultaneously with butadiene.

[0173] Example 8

[0174] A coin cell was manufactured in the same manner as in Example 1, except that the amount of butadiene added was adjusted to 13.5 g, and 4.5 g of isoprene was added simultaneously with butadiene.

[0175] Example 9

[0176] A coin cell was manufactured in the same manner as in Example 1 except that the amount of styrene added was adjusted to 7.5 g and the amount of butadiene added was adjusted to 19.5 g.

[0177] Example 10

[0178] A coin cell was manufactured in the same manner as in Example 1 except that the amount of styrene added was adjusted to 10.5 g and the amount of butadiene added was adjusted to 16.5 g.

[0179] Example 11

[0180] A coin cell was manufactured in the same manner as in Example 1 except that the added amounts of methyl (meth)acrylate, styrene, and butadiene were adjusted to 1.5 g, 9.5 g, and 19 g.

[0181] Example 12

[0182] A coin cell was manufactured in the same manner as in Example 1 except that the added amounts of methyl (meth)acrylate, styrene, and butadiene were adjusted to 4.5 g, 8.5 g, and 17 g.

[0183] Example 13

[0184] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.5×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.14×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0185] Example 14

[0186] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.375×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.1×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0187] Example 15

[0188] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.25×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.07×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0189] Example 16

[0190] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.214×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.06×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0191] Example 17

[0192] The difference from Example 3 is that the copolymer is mixed with N-phenylamino-silsesquioxane as a crosslinking agent, and 0.02×10 -3 The two are partially cross-linked using 1 mol palladium catalyst to prepare an adhesive, wherein the weight of N-phenylamino-silsesquioxane is 0.5% of the weight of the copolymer.

[0193] Example 18

[0194] The difference from Example 17 is that the weight of N-phenylamino-silsesquioxane is 1.0% by weight of the copolymer.

[0195] Example 19

[0196] The difference from Example 17 is that the weight of N-phenylamino-silsesquioxane is 1.5% of the weight of the copolymer.

[0197] Example 20

[0198] A coin cell was manufactured in the same manner as in Example 1 except that the weight ratio of the silicon-based negative electrode active material (silicon content: 60 wt %), graphite, and binder was adjusted to 96.5:2:1.5.

[0199] Comparative Example 1

[0200] The difference from Example 1 is that a combined binder of sodium carboxymethyl cellulose (CMC) and styrene-butadiene copolymer (SBR) is used instead of the binder in Example 1, and a negative electrode slurry is prepared by mixing silicon-based negative electrode active material (silicon content: 60 wt%), graphite, CMC and SBR in a weight ratio of 96:2:1.2:0.8.

[0201] Comparative Example 2

[0202] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.2×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.13×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0203] Comparative Example 3

[0204] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.75×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.125×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0205] Comparative Example 4

[0206] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.15×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.043×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0207] Comparative Example 5

[0208] In addition to adjusting the amount of n-butyl lithium added (effective amount) to 0.214×10 -3 mol, and the amount of octavinylsilsesquioxane added was adjusted to 0.033×10 -3 A coin cell was manufactured in the same manner as in Example 1 except for mol.

[0209] Comparative Example 6

[0210] A coin cell was manufactured in the same manner as in Example 1 except that the amount of styrene added was adjusted to 4.5 g and the amount of butadiene added was adjusted to 22.5 g.

[0211] Comparative Example 7

[0212] A coin cell was manufactured in the same manner as in Example 1 except that the amount of styrene added was adjusted to 13.5 g and the amount of butadiene added was adjusted to 13.5 g.

[0213] Comparative Example 8

[0214] A coin cell was manufactured in the same manner as in Example 1 except that the added amounts of methyl (meth)acrylate, styrene, and butadiene were adjusted to 1 g, 9.67 g, and 19.33 g.

[0215] Comparative Example 9

[0216] A coin cell was manufactured in the same manner as in Example 1 except that the added amounts of methyl (meth)acrylate, styrene, and butadiene were adjusted to 6 g, 8 g, and 16 g.

[0217] Comparative Example 10

[0218] The difference from Example 17 is that the weight of N-phenylamino-silsesquioxane is 2.0% by weight of the copolymer.

[0219] Evaluation of binders, anode slurries, anodes, and rechargeable batteries

[0220] (copolymer molecular weight)

[0221] The molecular weights of the copolymers of Examples 1 to 16 and Comparative Examples 2 to 10 were measured by gel permeation chromatography, and the analysis results of the number average molecular weight Mn of the first component in the copolymers and the number average molecular weight Mn of the copolymers are shown in Table 1.

[0222] (Viscosity)

[0223] The copolymers of Examples 1 to 16 and Comparative Examples 2 to 10 were dissolved in toluene, and the viscosities of the solutions having a solid content of 7 wt % were measured at 25° C. The results are shown in Table 1.

[0224] (Crosslinking degree test)

[0225] The crosslinking degree of the adhesives of Examples 17 to 19 and Comparative Example 10 was tested. The crosslinking degree of the adhesive was tested using the immersion dissolution method. 1 g of the adhesive sample was soaked in acetone or carbon tetrachloride for 7 days. The sample was then removed, dried, and weighed to obtain the mass of the soaked sample (w1). The crosslinking degree was calculated based on the weight change before and after soaking: crosslinking degree = w1 × 100%. The results are shown in Table 2.

[0226] (Coating performance)

[0227] The negative electrode slurries of Examples 1 to 20 and Comparative Examples 1 to 10 were respectively coated on copper foil and dried to obtain negative electrode active material layers. Whether the negative electrode active material layers were cracked was checked to evaluate coating performance. The results are shown in Table 3.

[0228] The coating performance evaluation was performed according to the following evaluation criteria.

[0229] ○: No cracks

[0230] ×: Cracks occurred

[0231] (Swelling test)

[0232] The adhesives of Examples 1 to 20 and Comparative Examples 1 to 10 were cut into samples of 10 mm × 20 mm, and the mass of the samples before immersion (w0) was weighed. The samples were then immersed in an electrolyte at 60°C for 48 hours. The solvent on the surface of the samples was wiped dry, and the mass of the samples after swelling (w2) was weighed. Each sample was weighed three times during the test, and the degree of swelling = (w2-w0) / w0×100%. The results are shown in Table 3.

[0233] (Adhesion)

[0234] The negative electrodes of Examples 1 to 20 and Comparative Examples 1 to 10 were dried in an oven at 60°C for 15 hours, cut into 10 mm × 20 mm strip samples, and adhered to a 30 mm × 60 cm steel plate with double-sided tape. The samples were rolled 8 times with a small stick, and the steel plate was fixed in the lower clamp of a tensile testing machine. The upper clamp clamped the sample and stretched 5 mm at a constant rate of 5 mm / min, where the angle between the pulled-up sample part and the steel plate in space was 180°. The average tensile force in the stable area was finally measured and recorded as the adhesion force of the negative electrode active material layer. The results are shown in Table 3.

[0235] (Negative electrode expansion rate after 100 cycles)

[0236] The metal lithium counter electrode cells of Examples 1 to 20 and Comparative Examples 1 to 10 were charged to 0.005 V at a constant current at a designed capacity of 0.1 CA (1 CA = 1 hour discharge rate) in a thermostat at 25°C, and then charged to 0.01 CA at a constant voltage at 0.005 V. Subsequently, the battery cells were disassembled to remove the negative electrode, and the thickness of the negative electrode was measured in microns and then compared with the thickness of the negative electrode before the first charge to evaluate the negative electrode expansion ratio after the first charge. The results are shown in Table 3.

[0237] Here, the negative electrode expansion rate is calculated according to [(negative electrode thickness after charge−negative electrode thickness before charge) / negative electrode thickness before charge]×100%.

[0238] (Peeling of the negative electrode active material layer after 100 cycles)

[0239] The negative electrodes of Examples 1 to 20 and Comparative Examples 1 to 10 were taken out after 100 cycles and visually inspected and evaluated according to the following criteria. The results are shown in Table 3.

[0240] ○: No separation of the negative electrode active material layer from the copper foil

[0241] △: Part of the negative electrode active material layer peeled off from the copper foil

[0242] ×: The entire negative electrode active material layer peeled off from the copper foil

[0243] (DC internal resistance (DR-IR))

[0244] At 25°C, the rechargeable lithium batteries of Examples 1 to 20 and Comparative Examples 1 to 10 were charged to full charge at a constant current of 0.7C, cut off at 0.02C, and allowed to stand for 10 minutes; discharged at a constant current of 0.5C for 30 seconds, charged at a constant current of 0.5C for 30 seconds, and allowed to stand for 10 minutes; discharged at a constant current of 1.0C for 30 seconds, charged at a constant current of 0.5C for 1 minute, and allowed to stand for 10 minutes; discharged at a constant current of 2.0C for 30 seconds, charged at a constant current of 0.5C for 2 minutes, and allowed to stand for 10 minutes; discharged at a constant current of 3.0C for 30 seconds, charged at a constant current of 0.5C for 3 minutes, and allowed to stand for 10 minutes; DC-IR (where R = ΔV / ΔI) was calculated based on the ratio of the average voltage change (ΔV) and the average current change (ΔI) during constant current discharge at each C rate, and the average value thereof was used as the measured value. The results are shown in Table 3.

[0245] (Cycle Characteristics)

[0246] The rechargeable battery cells of Examples 1 to 20 and Comparative Examples 1 to 10 were respectively charged to 4.3 V at a designed capacity of 0.1 CA at constant current in a 25° C. thermostat, and then charged to 0.05 CA at constant voltage at 4.3 V. The battery was then discharged to 2.5 V at a constant current of 0.1 CA.

[0247] Subsequently, in a 25° C. thermostat, under conditions of a charge cutoff voltage of 4.3 V and a discharge cutoff voltage of 2.5 V, the cell was charged at a constant current of 0.2 CA, charged at a constant voltage of 0.05 CA, and discharged at a constant current of 0.2 CA, which was regarded as one cycle and thus measured relative to the initial discharge capacity.

[0248] Subsequently, under the conditions of a charge cut-off voltage of 4.3 V and a discharge cut-off voltage of 2.5 V, the rechargeable battery cell was charged at a constant current of 0.5 CA at 25° C., the rechargeable battery cell was charged at a constant voltage of 0.05 CA, and the rechargeable battery cell was discharged at a constant current of 0.5 CA, and the cycle life test was repeated 100 times.

[0249] Subsequently, after 100 cycles, the battery was charged at a constant current of 0.2 CA, charged at a constant voltage of 0.05 CA, and discharged at 0.2 CA to measure the discharge capacity, and then, the discharge capacity was divided by the initial discharge capacity to obtain the capacity retention rate after 100 cycles. The results are shown in Table 3.

[0250] (Table 1)

[0251]

[0252]

[0253] In Table 1, the wt% of 1-1 units, 1-2 units, and 1-3 units are the weight percentages of 1-1 units, 1-2 units, and 1-3 units in the first component. The wt% of Ip is the weight percentage of isoprene in the 1-2 units. The molecular weights of the first component and the copolymer are number average molecular weights.

[0254] (Table 2)

[0255] Crosslinking agent content (%) Crosslinking degree (%) Example 17 0.5 11 Example 18 1.0 22 Example 19 1.5 36 Comparative Example 10 2.0 45

[0256] Table 2 shows the crosslinking agent content in the binders of Examples 17 to 19 and Comparative Example 10. The crosslinking agent content (%) refers to the percentage of the weight of the crosslinking agent to the weight of the copolymer. As can be seen from Table 2, as the crosslinking agent content increases, the degree of crosslinking increases. For Comparative Example 10, the degree of crosslinking has reached 45%.

[0257] (Table 3)

[0258]

[0259]

[0260] Table 3 shows some test properties of the binders, negative electrodes, and rechargeable batteries of Examples 1 to 20 and Comparative Examples 1 to 10.

[0261] As can be seen from Table 3, the binders of Examples 1 to 20 have lower swelling than the CMC-SBR combination binder of Comparative Example 1. Compared to the negative electrode of Comparative Example 1 using the CMC-SBR combination binder, the negative electrodes of Examples 1 to 20 using the binder according to the present disclosure exhibited lower expansion rates after 100 cycles. This demonstrates that the binder of the present disclosure has improved swelling resistance, and the resulting negative electrodes have improved volumetric and structural stability. Compared to the negative electrode of Comparative Example 1 using the CMC-SBR combination binder, the capacity retention of the negative electrodes of Examples 1 to 20 using the binder according to the present disclosure after 100 cycles is relatively low, indicating that the binder of the present disclosure also improves the lifespan of rechargeable batteries. Compared to the negative electrode of Comparative Example 1 using the CMC-SBR combination binder, the negative electrodes of Examples 1 to 5 exhibited relatively lower DC internal resistance, demonstrating that the use of the binder according to the present disclosure can improve lithium battery transmission efficiency and reduce internal resistance.

[0262] The adhesion of the negative electrodes of Comparative Examples 2 and 3 is poor, indicating that if the ratio of the first component to the second component in the copolymer is too low or the relative molecular weight of the first component is too low, the adhesion will deteriorate, which will in turn lead to the deterioration of the negative electrode expansion rate and capacity retention rate.

[0263] The negative electrode expansion rate, capacity retention rate, and DC internal resistance of Comparative Example 4 were poor. This may be because the relative molecular weight of the first component in its copolymer is too large, resulting in a long molecular chain. After multiple cycles, some molecular chains will break, resulting in an increase in the negative electrode expansion rate. At the same time, this also leads to a decrease in adhesion to the electrode active material, resulting in a decrease in the negative electrode capacity retention rate. In addition, the larger molecular weight of the first component hinders the transmission of lithium ions to a certain extent.

[0264] The binder of Comparative Example 5 cannot be used to manufacture a negative electrode because the relative molecular weight of its copolymer is too large, which makes it difficult to dissolve in the solvent when preparing the negative electrode slurry, making it difficult to prepare the negative electrode slurry.

[0265] The binder of Comparative Example 6 has a larger swelling degree and a higher expansion rate of the negative electrode because the 1-1 unit content in the first component is too low and the hard block content is low, resulting in poor volume stability of the negative electrode.

[0266] The adhesion of Comparative Example 7 is low because the content of the 1-2 unit in the first component is too low and the content of the soft block is low.

[0267] The expansion rate and DC internal resistance of the negative electrode of Comparative Example 8 are larger, and the capacity retention rate is lower. This may be because the 1-3 units in the copolymer of Comparative Example 8 are relatively few, and they cannot effectively play their role in inhibiting the volume expansion of the silicon negative electrode material and improving the electrical performance of the negative electrode.

[0268] The negative active material layer of Comparative Example 9 occasionally cracks. This is because the copolymer of Comparative Example 9 contains a large number of 1-3 units, which makes it difficult to prepare the electrode active material layer.

[0269] The binder of Comparative Example 10 contains too much cross-linking agent, resulting in excessive rigidity of the binder, making it difficult to prepare the negative electrode slurry.

[0270] Examples 17 to 19 showed higher adhesion because the addition of the cross-linking agent improved the adhesion of the adhesive.

[0271] Furthermore, a comparison of Examples 1 to 6 reveals that Example 6 exhibits relatively high DC internal resistance. This is due to the excessive amount of the first component in the copolymer, which, to some extent, obstructs the lithium ion transport pathway. The relatively low adhesion of Example 4 suggests that a copolymer containing approximately two first components has limited effect on adhesion.

[0272] Furthermore, in Example 20, a relatively low binder weight ratio (1.5 wt%) was used, and the binder, negative electrode, and rechargeable battery obtained therefrom also exhibited excellent swelling resistance, volume stability, capacity retention, and DC internal resistance. This demonstrates that the binder according to the present disclosure can improve battery performance even at relatively low usage levels.

[0273] According to an embodiment of the present disclosure, a binder for a rechargeable battery may include a copolymer comprising a plurality of first components and a second component bonded to the plurality of first components. The first component comprises 1-1 units derived from a monovinyl aromatic monomer, 1-2 units derived from a conjugated diene monomer, and 1-3 units derived from an acrylate monomer, and the second component is derived from vinyl silsesquioxane or a derivative thereof. The ratio of the first component to the second component may be 2 to 5. The binder may also include a crosslinking agent.

[0274] The binder may have at least improved swelling resistance, thereby improving volume stability and structural stability of an electrode including the binder.

[0275] While the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. A binder for a negative electrode of a rechargeable battery, characterized in that The binder comprises a copolymer comprising: a plurality of first components, each first component having a linear or branched structure, each first component comprising 1-1 units derived from a monovinyl aromatic monomer, 1-2 units derived from a conjugated diene monomer, and 1-3 units derived from an acrylate monomer; and a second component constituting the core node of the copolymer, derived from vinyl silsesquioxane or a derivative thereof, wherein, in the copolymer, the plurality of first components are respectively bonded to the vinyl group of the one second component, The ratio of the first component to the second component in the copolymer is 3:1 to 5:1, The number average molecular weight of the copolymer is in the range of 250,000 to 600,000, and Based on 100wt% of the total weight of the 1-1 unit, the 1-2 unit and the 1-3 unit in the first component, the amount of the 1-1 unit is in the range of 25wt% to 35wt%, the amount of the 1-2 unit is in the range of 55wt% to 65wt%, and the amount of the 1-3 unit is in the range of 5wt% to 15wt%.

2. The binder for a negative electrode of a rechargeable battery according to claim 1, wherein The monovinyl aromatic hydrocarbon monomer is at least one selected from styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinyltoluene, vinylxylene, adamantylstyrene, vinylanthracene, vinylbiphenyl, and 1,1-diphenylethylene.

3. The binder for a negative electrode of a rechargeable battery according to claim 1, wherein The conjugated diene monomer includes at least one of butadiene and isoprene.

4. The binder for a negative electrode of a rechargeable battery according to claim 1, wherein The acrylic acid ester monomers include at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, ethylhexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate.

5. The binder for a negative electrode of a rechargeable battery according to claim 1, wherein The binder further includes a cross-linking agent including units derived from aminosilsesquioxane or a derivative thereof.

6. A negative electrode, characterized in that The negative electrode includes the binder for a negative electrode of a rechargeable battery according to any one of claims 1 to 5.

7. A rechargeable battery, characterized in that: The rechargeable battery comprises: The negative electrode according to claim 6; a positive electrode; and An electrolyte is disposed between the negative electrode and the positive electrode.

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