Secondary battery and related apparatus

Abstract

The present application discloses a secondary battery and a related apparatus. The secondary battery provided by the present application comprises a negative electrode sheet. The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer comprises a negative electrode active substance and a polymer. The chemical general formula of a polymerizable monomer of the polymer is formula (I). According to the secondary battery provided by the present application, because a polymer formed by a polymerizable monomer having a specific structure is added, the problems of breakage of the negative electrode active substance and damage to the internal structure of the negative electrode sheet due to volume expansion of the negative electrode sheet are significantly reduced, thereby effectively prolonging the cycle life of a battery.

Description

A secondary battery and related devices

[0001] This application claims priority to Chinese Patent Application No. 202411493155.3, filed on October 24, 2024, entitled "A Secondary Battery, Related Devices, System and Charging Network", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a secondary battery and related devices. Background Technology

[0003] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0004] With the rapid development of technology and the continuous advancement of energy transition, lithium-ion batteries, as a key electrochemical energy storage technology, have expanded their application areas from portable electronic devices to multiple important fields such as electric vehicles, smart grids, and renewable energy storage. In these application scenarios, the performance of lithium-ion batteries is directly related to the operating efficiency and lifespan of related equipment, thus placing higher demands on the performance of lithium-ion batteries.

[0005] Application content

[0006] The purpose of this application is to provide a secondary battery and related devices, including but not limited to solving the problem of unsatisfactory battery cycle life.

[0007] The technical solution adopted in the embodiments of this application is:

[0008] In a first aspect, a secondary battery is provided, comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material and a polymeric monomer, the polymeric monomer being as shown in Formula I:

[0009] R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R2 includes a lithium-ionized acidic group, and n is a natural number ≤ 5.

[0010] In this embodiment, the alkynyl groups contained in the polymer monomer gain electrons during charging and undergo in-situ polymerization, thereby forming a network structure and an elastic polymer. Since the polymer monomer and the negative electrode active material are used in the negative electrode film layer of the negative electrode sheet, the polymer formed by the polymerization of the polymer monomer can be bound to the surface of the negative electrode active material. In this way, the network structure of the polymer can provide spatial confinement when the negative electrode active material is embedded with active ions, which greatly reduces the expansion degree of the negative electrode sheet. Based on this, the presence of polymers formed by polymer monomers with specific structures significantly reduces the problem of the negative electrode sheet cracking due to volume expansion and damage to the internal structure of the negative electrode sheet, thereby effectively extending the cycle life of the battery.

[0011] In some embodiments, R2 includes either -COOLi or -SO3Li.

[0012] These lithium-ionized acidic groups can participate in the formation of the SEI film, thereby effectively reducing the active lithium consumed in the formation of the SEI film during the formation stage, and thus effectively improving the first charge and discharge efficiency of the battery.

[0013] In some embodiments, R1 includes any one of hydrogen, amino-substituted C1-C4 alkyl, hydroxyl-substituted C1-C4 alkyl, and C1-C4 alkyl.

[0014] In the embodiments of this application, these groups can improve the interaction between the polymer monomer and the negative electrode active material, or increase the polarity of the polymer monomer, or help improve the hydrophobicity of the polymer monomer, thereby reducing the occurrence of side reactions, optimizing the formation of the SEI film, and thus improving the first efficiency and cycle performance of the battery.

[0015] In some embodiments, n is 0 or 1.

[0016] By controlling the number of methylene groups in the polymer monomer within the above range, the interaction between the polymer monomer and the negative electrode active material can be optimized, thereby giving the negative electrode a higher electrode reaction kinetics and improving the reaction rate of the negative electrode, thus improving the charge and discharge performance of the secondary battery.

[0017] In some embodiments, the polymeric monomer includes at least one of the compounds represented by Formula I-1 to Formula I-10:

[0018] In the embodiments of this application, the polymer monomers shown in Formulas I-1 to I-10 can be distributed in a relatively uniform manner between the negative electrode active materials. During the formation process, the alkynyl groups contained therein gain electrons to polymerize and form a network structure polymer. This polymer can combine with the negative electrode active material, thereby exerting a binding effect on the negative electrode active material, reducing the degree of expansion of the negative electrode active material when intercalating active ions, and thus preventing the pulverization and shedding of the negative electrode active material, so that the battery exhibits high cycle performance.

[0019] In some embodiments, at least a portion of the polymeric monomers are connected to the negative electrode active material via at least one chemical bond, namely ionic bonds or hydrogen bonds.

[0020] The lithium-ionized acidic groups in the polymer monomer can be linked to the negative electrode active material through ionic bonds and / or hydrogen bonds. This linkage helps to improve the structural integrity of the negative electrode active material, enabling it to better withstand the insertion and extraction of active ions during charging and discharging, reducing the shedding and degradation of the negative electrode active material, thereby improving the cycle performance and capacity retention of the battery.

[0021] In some embodiments, the mass ratio of the negative electrode active material to the polymer monomer is 100:(0.5-5).

[0022] In this embodiment, the content of the polymer monomer is controlled within the above-mentioned range, which can give full play to the role of the polymer monomer, thereby reducing the volume expansion of the negative electrode active material intercalating into active ions, and thus improving the cycle life of the battery.

[0023] In some embodiments, the negative electrode film layer further includes at least one of a binder, a dispersant, and a conductive agent.

[0024] Adding the above components, such as binders, dispersants and conductive agents, to the negative electrode film can improve the adhesion, uniformity and conductivity of the negative electrode sheet.

[0025] In some embodiments, the mass ratio of the negative electrode active material to the binder, dispersant, and conductive agent is 100:(0.5-2):(0.5-2):(0.1-2).

[0026] By controlling the mass ratio of the negative electrode active material, binder, dispersant, and conductive agent within the above range, the binder, dispersant, and conductive agent can fully exert their synergistic effect, thereby obtaining a negative electrode sheet with better adhesion, more uniform distribution of each component, and excellent conductivity.

[0027] In some embodiments, at least a portion of the surface of the negative electrode film is covered with an SEI film, the SEI film containing lithiated acidic groups.

[0028] Lithium-modified acidic groups can participate in the formation of the SEI film. As a result, the lithium-modified acidic groups can act as part of the SEI film, thereby synergistically with other components such as electrolyte decomposition products to enhance the stability of the SEI film, reduce side reactions between active materials and electrolyte, and help improve the cycle life of the battery.

[0029] Secondly, this application provides a method for preparing a secondary battery, comprising the following steps:

[0030] The compound with the general chemical formula shown in Formula II is reacted with lithium hydroxide in a solution system to prepare the polymer monomer;

[0031] R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R3 includes an acidic group, and n is a natural number ≤ 5;

[0032] A negative electrode slurry containing polymer monomers and negative electrode active materials is prepared, and the negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer, so as to prepare a negative electrode sheet.

[0033] The negative electrode and the positive electrode are assembled to prepare a secondary battery.

[0034] The method for preparing a secondary battery provided in this application involves neutralizing a compound of Formula II with lithium hydroxide to obtain a polymeric monomer of Formula I. A negative electrode slurry containing this monomer is then prepared and coated onto the surface of a negative electrode current collector to form a negative electrode film. The negative electrode film is then assembled with a positive electrode film, thereby effectively preparing a secondary battery with the performance described above. Furthermore, the method for preparing the secondary battery in this application is simple to operate, reliable, controllable, efficient, and saves production costs.

[0035] In some embodiments, R3 includes either a carboxyl group or a sulfonic acid group.

[0036] Carboxyl and sulfonic acid groups can form bonds with the negative electrode active material, which helps to further improve the structural stability of the negative electrode active material.

[0037] In some embodiments, the molar ratio of the compound represented by Formula II to lithium hydroxide is 1:(0.9-1.1).

[0038] By controlling the molar ratio within the above range, the compound shown in Formula II can react fully with lithium hydroxide, thereby effectively lithiating the acidic groups.

[0039] Thirdly, this application provides a battery device including a plurality of secondary batteries as described in the above embodiments.

[0040] Fourthly, this application provides an electrical device, including a secondary battery or a battery device as described in the above embodiments, wherein the secondary battery or battery device is used to store or provide electrical energy. Attached Figure Description

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0042] Figure 1 is an exploded view of the battery device provided in an embodiment of this application;

[0043] Figure 2 is an exploded view of a single battery cell provided in an embodiment of this application;

[0044] Figure 3 shows a schematic diagram of an embodiment of an electrical device in which a single battery cell is used as a power source, according to an embodiment of this application.

[0045] In the figure, the following reference numerals are used: 100, battery device; 10, housing; 11, first housing; 12, second housing; 20, battery cell assembly; 30, battery cell; 31, casing; 32, electrode assembly; 33, cover plate. Detailed Implementation

[0046] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0048] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0049] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0050] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0051] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0052] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0053] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0054] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0055] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0056] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0057] Unless otherwise specified, all steps of 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.

[0058] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0059] In the embodiments of this application, SEI film is short for "solid electrolyte interface", which refers to a solid electrolyte interface film with the characteristics of a solid electrolyte. That is, during the first charge and discharge process of a liquid lithium-ion battery, a passivation layer formed by the reaction between the electrode material and the electrolyte at the solid-liquid interface is formed and covers the surface of the negative electrode material.

[0060] In the embodiments of this application, the term "alkyl" refers to a saturated hydrocarbon containing a primary (normal) carbon atom, a secondary carbon atom, a tertiary carbon atom, a quaternary carbon atom, or a combination thereof. Phrases containing this term include, for example, "C1-C1...". 10"Alkyl" refers to an alkyl group containing 1 to 10 carbon atoms. Each time it appears, it can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, ... 10 alkyl.

[0061] In the embodiments of this application, the term "amino-substituted C1-C1" is used. 10 "Alkyl" refers to a straight-chain or branched saturated hydrocarbon group composed of carbon and hydrogen atoms, with a carbon chain length of 1 to 10 carbon atoms. Amino substitution refers to the substitution of the above C1-C2 groups. 10 On an alkyl group, one or more hydrogen atoms are replaced by an amino group. As an example, when a hydrogen atom on a methyl group (-CH3) is replaced by an amino group, methylamino (-CH2NH2) is formed.

[0062] In the embodiments of this application, the term "hydroxyl-substituted C1-C1" is used. 10 "Alkyl" refers to a straight-chain or branched saturated hydrocarbon group composed of carbon and hydrogen atoms, with a carbon chain length of 1 to 10 carbon atoms. Hydroxyl substitution refers to the substitution of the above C1 to C2 groups. 10 On an alkyl group, one or more hydrogen atoms are replaced by hydroxyl groups. As an example, when a hydrogen atom on a methyl group (-CH3) is replaced by a hydroxyl group, methylamino (-CH2OH) is formed.

[0063] In the embodiments of this application, the term "lithiated acidic group" refers to an acidic group that reacts with lithium (Li) under specific conditions, thereby introducing lithium element onto the acidic group. As examples, acidic groups include, but are not limited to, carboxylic acid groups (-COOH), sulfonic acid groups (-SO3H), phosphate groups (-PO4H2), and other oxyacid groups such as borate groups (-B(OH)2).

[0064] In this embodiment of the application, a secondary battery refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0065] From a market perspective, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars. As the application areas of power batteries continue to expand, people are placing higher demands on the lifespan of new energy vehicles. This demand translates into requirements for battery cycle performance.

[0066] In lithium-ion batteries, the negative electrode is a crucial component, its performance directly impacting the battery's cycle life, energy density, and power output. However, the volume expansion of the negative electrode active material is a significant issue affecting its performance, leading to its breakage and detachment. This volume change also damages the SEI film, especially when the SEI film ruptures, as new electrolyte comes into contact with the fresh surface of the negative electrode active material, causing SEI reformation. This process consumes active lithium, reducing the lithium stock in the battery and affecting cycle stability and energy density. Over time, this repeated SEI breakage and repair process leads to rapid capacity decay, thus shortening the battery's cycle life.

[0067] Based on this, embodiments of this application provide a secondary battery, including a negative electrode sheet, which includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material and a polymer, wherein the polymer monomer is shown in Formula I:

[0068] R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R2 includes a lithium-ionized acidic group, and n is a natural number ≤ 5.

[0069] In this embodiment, the alkynyl groups contained in the polymer monomers undergo in-situ polymerization during charging, thereby forming a network structure and an elastic polymer. Since the polymer monomers are distributed between the negative electrode active materials, it means that there is good contact between the polymer monomers and the negative electrode active materials. Thus, the polymer formed by the polymerization of the polymer monomers can bind to the surface of the negative electrode active materials. This network structure of polymer can provide spatial confinement when active ions are inserted into the negative electrode active materials, greatly reducing the expansion of the negative electrode sheet. This significantly reduces the problem of the negative electrode sheet cracking due to volume expansion and damage to the internal structure of the negative electrode sheet, thereby effectively extending the cycle life of the battery.

[0070] In one embodiment, the polymer formed by the polymerization of monomers during the formation stage can coat the surface of the negative electrode active material. Since the polymer has a network structure, it can tightly wrap the negative electrode active material and physically bind it from all directions. Thus, when the negative electrode active material undergoes volume changes due to the insertion and extraction of active ions during charging and discharging, the polymer network structure will limit the extent of its outward expansion, preventing it from expanding excessively.

[0071] In another embodiment, the polymer network structure is interwoven between the negative electrode active materials. Since there are gaps between the negative electrode active material particles, the polymer may enter these gaps during formation, interweaving with the negative electrode active materials to form an interlaced structure. In this way, the polymer may form a skeleton between the negative electrode active materials, connecting them together. The polymer may also fill the gaps between the negative electrode active materials. The polymer network structure, existing in the gaps between the negative electrode active material particles, occupies a certain space, which creates steric hindrance, hindering the free movement and expansion of the negative electrode active material particles during volume expansion, thereby reducing the magnitude of volume expansion. Furthermore, the polymer network structure can also provide mechanical support and constraint, effectively inhibiting the breakage and pulverization of the negative electrode active material particles, improving the structural integrity of the negative electrode active material, and thus limiting the degree of volume expansion.

[0072] Because polymers formed from monomers possess a certain degree of elasticity, they can undergo elastic deformation to some extent when the negative electrode active material expands in volume. This absorbs and disperses some of the stress generated by the volume change, preventing stress concentration on the negative electrode active material and thus avoiding structural cracking or damage. Consequently, it reduces the extent of volume expansion caused by structural failure. Furthermore, the network structure of the polymer allows for tight bonding with the negative electrode active material, enabling the stress generated during volume expansion to be distributed more evenly throughout the entire negative electrode system. This prevents excessive localized expansion or damage to the negative electrode active material due to excessive localized stress, contributing to improved overall structural stability of the negative electrode sheet and suppressing uneven and excessive volume expansion.

[0073] In addition, the polymer has a certain degree of adhesion, which allows the negative electrode active material particles to be firmly connected together and can fix the negative electrode active material on the surface of the negative electrode current collector. This can effectively prevent the negative electrode active material from falling off and breaking during battery charging and discharging.

[0074] Based on this, the alkynyl groups in the monomer undergo in-situ polymerization after gaining electrons to form a polymer. This polymer can effectively suppress the volume expansion of the negative electrode active material. This not only effectively improves the integrity of the overall structure of the negative electrode sheet, allowing the negative electrode active material to maintain a relatively stable structure during long-term cycling, thereby extending the cycle life of the battery; but also reduces the rupture and recombination of the SEI film, reduces the electrolyte consumption rate, and further extends the cycle life of the battery.

[0075] In the technical solution of this application, the lithiated acidic groups contained in the polymer monomer can, on the one hand, serve as channels or sites for lithium-ion transport, optimizing the transport kinetics of lithium-ions and enabling lithium-ions to be inserted into and extracted from the negative electrode active material more quickly, thereby improving the rate performance of the battery; on the other hand, the lithiated acidic groups can participate in the formation of the SEI film. Thus, the lithiated acidic groups can be part of the SEI film, thereby synergistically acting with other components such as the decomposition products of the electrolyte to enhance the stability of the SEI film, thereby reducing the side reactions between the active material and the electrolyte, and helping to improve the cycle life of the battery.

[0076] A negative electrode current collector refers to a structure or component in a battery used to collect current at the negative electrode. For example, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil can be copper foil. The composite current collector can be a polymer matrix material and a metal layer formed on at least one surface of the polymer matrix material. The composite current collector can be formed on the surface of the polymer matrix material using copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, or silver alloys. The polymer matrix material can be polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.

[0077] The negative electrode film layer refers to the film layer disposed on the negative electrode current collector and containing the negative electrode active material. The negative electrode active layer can be disposed on one side of the negative electrode current collector or on both sides of the negative electrode current collector.

[0078] Negative electrode active material refers to the material that can accept and store active ions during battery discharge and release these ions during charging. Specifically, during battery operation, the negative electrode active material undergoes an electrochemical reaction, achieving ion insertion and extraction through the gain and loss of electrons.

[0079] 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. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0080] In some embodiments, R2 includes either -COOLi or -SO3Li.

[0081] On the one hand, these lithium-ionized acidic groups can participate in the formation of the SEI film, thereby effectively reducing the active lithium consumed in the SEI film formation stage and thus effectively improving the battery's initial charge-discharge efficiency. On the other hand, these lithium-ionized acidic groups help form a stable SEI film, thereby suppressing side reactions and reducing electrolyte decomposition, thus improving the battery's cycle stability. Furthermore, these lithium-ionized acidic groups can optimize the wettability of the electrolyte to the negative electrode active material, thereby increasing the contact area between the negative electrode active material and the electrolyte. This provides more channels and shorter transport paths for the transport of active ions between the negative electrode and the electrolyte, promoting charge transfer reactions and thus improving the battery's cycle performance and rate performance.

[0082] In addition, the -COOLi and -SO3Li groups can form chemical bonds or other interactions with the negative electrode active material, thereby buffering the stress caused by volume changes during charging and discharging, helping to reduce the cracking and pulverization of the negative electrode active material, improving the structural integrity of the negative electrode sheet, and thus improving the cycle life of the battery.

[0083] In some embodiments, R1 includes any one of hydrogen, amino-substituted C1-C4 alkyl, hydroxyl-substituted C1-C4 alkyl, and C1-C4 alkyl.

[0084] Hydrogen atoms can form bonds with the negative electrode active material, which helps to enhance the interaction between the polymer monomer and the negative electrode active material. This can reduce the structural changes and damage of the negative electrode active material during charging and discharging, thereby improving the stability of the negative electrode sheet and enabling the battery to exhibit higher cycle performance.

[0085] Amino-substituted C1-C4 alkyl groups have a certain degree of polarity and can form hydrogen bonds with solvents or electrolyte salts in the electrolyte. This not only improves the transport efficiency of lithium ions between the negative electrode and the electrolyte, thereby improving the rate performance of the battery, but also helps to form a stable SEI film, thereby reducing electrolyte decomposition and improving the cycle performance of the battery.

[0086] Hydroxyl-substituted C1-C4 alkyl groups, wherein the hydroxyl group has high polarity and can react with the solvent in the electrolyte, optimize the formation of the SEI film, thereby obtaining a uniformly grown and dense and stable SEI film, thereby reducing electrolyte decomposition and lithium ion consumption, and improving the battery's initial efficiency and cycle stability.

[0087] The introduction of alkyl groups can optimize the molecular weight of the polymer monomers, thereby improving their solubility and migration in the electrolyte, and thus optimizing the formation of the SEI film, resulting in a stable and dense SEI film, which in turn gives the battery high cycle stability.

[0088] In some embodiments, n is 0 or 1.

[0089] Controlling the number of methylene groups in the polymer monomer within the aforementioned range can, on the one hand, optimize the interaction between the polymer monomer and the negative electrode active material, thereby giving the negative electrode sheet higher electrode reaction kinetics and increasing the reaction rate of the negative electrode sheet; on the other hand, it can give the polymer monomer appropriate flexibility, thereby improving the flexibility of the negative electrode active material in contact with it. This allows active ions to diffuse more smoothly inside the negative electrode sheet, optimizing the transport capacity of active ions and giving the battery higher charge and discharge performance.

[0090] In some embodiments, the polymeric monomer includes at least one of the compounds represented by Formula I-1 to Formula I-10:

[0091] In this embodiment, the polymer monomers represented by Formulas I-1 to I-10 can be distributed relatively uniformly among the negative electrode active materials. During formation, the alkynyl groups contained therein gain electrons and polymerize to form a network structure polymer. This polymer can bind to the negative electrode active material, thereby exerting a binding effect on the negative electrode active material, reducing the degree of expansion of the negative electrode active material when intercalating active ions, and thus preventing the negative electrode active material from being crushed and detached. Based on this, not only can the negative electrode active material maintain a relatively stable structure during long-term cycling, thereby extending the cycle life of the battery, but it can also reduce the rupture and recombination of the SEI film, reduce the consumption rate of electrolyte, and thus extend the cycle life of the battery.

[0092] In some embodiments, at least a portion of the polymeric monomers are connected to the negative electrode active material via at least one chemical bond, namely ionic bonds or hydrogen bonds.

[0093] The lithium-ionized acidic groups in the polymer monomer can be bonded to the hydroxyl groups on the surface of the negative electrode active material through ionic bonds and / or hydrogen bonds. This bonding helps to improve the structural integrity of the negative electrode active material, enabling it to better withstand the insertion and extraction of active ions during charging and discharging, reducing material breakage and shedding caused by volume expansion and contraction during charging and discharging, thereby extending the cycle life of the battery.

[0094] In addition, the bonding between the polymer monomer and the negative electrode active material helps to fix the negative electrode active material on the surface of the negative electrode current collector, thereby improving the adhesion between the negative electrode active material and the negative electrode current collector, reducing the shedding of the negative electrode active material during charging and discharging, and improving the integrity of the negative electrode sheet. As a result, the battery exhibits excellent cycle performance.

[0095] In some embodiments, the mass ratio of the negative electrode active material to the polymer monomer is 100:(0.5-5). Exemplary examples include typical but non-limiting values ​​such as 100:0.5, 100:1, 100:2, 100:3, 100:4, and 100:5.

[0096] In this embodiment, the content of the polymeric monomer is controlled within the above-mentioned range, which can give full play to the role of the polymeric monomer, so that it contains an appropriate amount of alkynyl groups to form an appropriate amount of polymer during the formation stage, thereby enhancing the binding of the negative electrode active material, limiting its outward expansion, and preventing it from expanding excessively. In this way, the negative electrode active material can easily maintain a relatively stable structure during long-term cycle use, thereby extending the cycle life of the battery. In addition, it can also reduce the rupture and recombination of the SEI film, reduce the consumption rate of electrolyte, and further extend the cycle life of the battery.

[0097] In some embodiments, the negative electrode film layer further includes at least one of a binder, a dispersant, and a conductive agent.

[0098] Adding the above components, such as binders, dispersants and conductive agents, to the negative electrode film can improve the adhesion, uniformity and conductivity of the negative electrode sheet.

[0099] As an example, the adhesive may include, but is not limited to, at least one of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, and carboxymethyl chitosan.

[0100] As an example, conductive agents may include, but are not limited to, at least one of superconducting carbon, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0101] As an example, dispersants include, but are not limited to, sodium carboxymethyl cellulose.

[0102] In some embodiments, the mass ratio of the negative electrode active material to the binder, dispersant, and conductive agent is 100:(0.5-2):(0.5-2):(0.1-2).

[0103] For example, the mass percentage of the adhesive can be typical but not limiting values ​​such as 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, etc.

[0104] For example, the mass percentage of the dispersant can be typical but not limiting values ​​such as 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, etc.

[0105] For example, the mass percentage of the conductive agent can be typical but not limiting values ​​such as 0.1, 0.3, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, etc.

[0106] By controlling the mass ratio of negative electrode active material, binder, dispersant and conductive agent within the above range, the binder, dispersant and conductive agent can fully exert their synergistic effect, thereby obtaining a negative electrode sheet with better adhesion, more uniform distribution of each component and excellent conductivity, thereby improving the overall performance of the secondary battery.

[0107] In some embodiments, at least a portion of the surface of the negative electrode film is covered with an SEI film, the SEI film containing lithiated acidic groups.

[0108] The polymer monomer provided in this application includes a lithium-ionized acidic group, which can participate in the formation of the SEI film. Thus, the lithium-ionized acidic group can be part of the SEI film, thereby synergistically interacting with other components such as the decomposition products of the electrolyte to enhance the stability of the SEI film, thereby reducing the side reactions between the active material and the electrolyte and helping to improve the cycle life of the battery.

[0109] In some embodiments, the polymer comprises one or more of the polymer segments shown in Formula III and the polymer segments shown in Formula IV;

[0110] Where a is 2-1000, b is 2-1000, and c is 2-1000.

[0111] Because the negative electrode film includes polymeric monomers, and these monomers contain alkynyl groups, these alkynyl groups gain electrons during the formation stage and undergo in-situ polymerization. This forms a polymer containing the aforementioned chain segments. This polymer can bind the negative electrode active material, thereby suppressing its volume expansion. This not only effectively improves the overall integrity of the negative electrode sheet, allowing the negative electrode active material to maintain a relatively stable structure during long-term cycling, thus extending the battery's cycle life, but also reduces the rupture and recombination of the SEI film, slowing down the electrolyte consumption rate and further extending the battery's cycle life.

[0112] In some embodiments, the secondary battery includes a positive electrode and a separator disposed between the positive and negative electrodes, in addition to the negative electrode. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0113] [Positive electrode plate]

[0114] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The aforementioned "positive electrode film layer disposed on at least one surface of the positive current collector" means that the positive electrode film layer can be disposed on one surface of the positive current collector along its own thickness direction, or it can be disposed on two surfaces of the positive current collector along its own thickness direction.

[0115] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. In some embodiments, the positive electrode 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0116] In some embodiments, the positive electrode film contains a positive electrode active material, which may include positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material of a lithium-ion secondary battery may include at least one of the following materials: lithium-containing 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 positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, nickel-cobalt-manganese-aluminum quaternary materials, lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium manganese oxide, and their modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. The weight ratio of the positive electrode active material in the positive electrode active layer is 80wt%-100wt%, based on the total weight of the positive electrode active layer.

[0117] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder in the positive electrode film layer may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder accounts for 0-20 wt% of the positive electrode film layer based on the total weight of the positive electrode active layer.

[0118] 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, carbon black (e.g., acetylene black or Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent comprises 0-20 wt% of the positive electrode film, based on the total weight of the positive electrode film.

[0119] 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 on the surface of the positive current collector, drying it and then cold pressing it through a cold rolling mill to form the positive electrode sheet.

[0120] [Isolation membrane]

[0121] The separator is used to separate the positive electrode and the negative electrode, prevent short circuits inside the secondary battery, allow electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process.

[0122] This application does not impose any particular restrictions on the separator membrane; as long as it can achieve the purpose of this application, any well-known porous separator membrane with good chemical and mechanical stability can be selected.

[0123] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0124] [Electrolytes]

[0125] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0126] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0127] Taking lithium-ion batteries as an example, 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.

[0128] 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.

[0129] 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.

[0130] The second aspect of this application provides a method for preparing a secondary battery, comprising the following steps:

[0131] Step S10: React the compound with the chemical formula shown in Formula II with lithium hydroxide in a solution system to prepare the polymer monomer;

[0132] R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R3 includes an acidic group, and n is a natural number ≤ 5;

[0133] Step S20: Prepare a negative electrode slurry containing polymer monomers and negative electrode active materials, and coat the negative electrode slurry on at least one side of the negative electrode current collector to form a negative electrode film layer to prepare a negative electrode sheet.

[0134] Step S30: Assemble the negative electrode and the positive electrode to prepare a secondary battery.

[0135] The method for preparing a secondary battery provided in this application involves neutralizing a compound of Formula II with lithium hydroxide to obtain a polymeric monomer of Formula I. A negative electrode slurry containing the polymeric monomer is then prepared and coated onto the surface of a negative electrode current collector to form a negative electrode film. The negative electrode film is then assembled with a positive electrode film, thereby effectively preparing a secondary battery with the performance described above. Furthermore, the method for preparing the secondary battery in this application is simple to operate, reliable, controllable, highly efficient, and saves production costs.

[0136] In some embodiments, in step S10, the molar ratio of the compound represented by Formula II to lithium hydroxide is 1:(0.9-1.1). Exemplary examples show that the molar ratio of the compound represented by Formula II to lithium hydroxide can be typical but non-limiting values ​​such as 1:0.9, 1:1, 1:1.1, etc.

[0137] By controlling the molar ratio within the above range, the compound shown in Formula II can react fully with lithium hydroxide, thereby effectively lithiating the acidic groups.

[0138] In some embodiments, in step S10, R3 includes either a carboxyl group or a sulfonic acid group.

[0139] Carboxyl and sulfonic acid groups can form bonds with the negative electrode active material, which helps to further improve the structural stability of the negative electrode active material.

[0140] In some embodiments, in step S10, n is a natural number ≤ 1. As an example, n is 0 or 1.

[0141] In some embodiments, in step S10, R1 includes any one of hydrogen, amino-substituted C1-C4 alkyl, hydroxyl-substituted C1-C4 alkyl, and C1-C4 alkyl.

[0142] In some embodiments, in step S20, a negative electrode slurry containing polymeric monomers and negative electrode active materials is prepared, and the negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer. The specific process is as follows:

[0143] The components for preparing the negative electrode sheet, such as polymeric monomers, negative electrode active materials, conductive agents, binders, and dispersants, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is coated onto a negative electrode current collector to form a negative electrode film layer. After drying, cold pressing, and other processes, the negative electrode sheet can be obtained.

[0144] In some embodiments, in step S30, the negative electrode sheet, separator, and positive electrode sheet can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a secondary battery is obtained. The shape of the secondary battery is not particularly limited; it can be cylindrical, square, or any other arbitrary shape.

[0145] A third aspect of this application provides a battery device including a plurality of secondary batteries described in the above embodiments.

[0146] The battery device mentioned in the embodiments of this application may include one or more secondary battery assemblies for providing voltage and capacity. The secondary battery assembly may include multiple secondary batteries, which are connected in series, parallel, or mixed connections via a busbar.

[0147] In some embodiments, the secondary battery assembly is typically formed by arranging multiple secondary batteries.

[0148] As an example, a secondary battery assembly can be a battery module, which consists of multiple secondary batteries arranged and fixed together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary batteries together with cable ties.

[0149] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more secondary battery components housed within the housing.

[0150] As an example, the secondary battery assembly can be a battery module, which can be housed in the housing by fixing the battery module in the housing.

[0151] As an example, a secondary battery assembly can also be housed in a housing by directly fixing multiple secondary batteries to the housing.

[0152] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the secondary battery assembly. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0153] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the secondary battery assembly.

[0154] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0155] A fourth aspect of this application provides an electrical device, including a secondary battery or a battery device as described in the above embodiments, wherein the secondary battery or battery device is used to store or provide electrical energy.

[0156] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use secondary batteries, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0157] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery device, and power consumption device provided in the embodiments of this application.

[0158] Figure 1 is an exploded view of a battery device 100 as an example. The battery device 100 includes a housing 10 and battery cell assemblies 20, the battery cell assemblies 20 being housed within the housing 10. The housing 10 provides a space for housing the battery cell assemblies 20, and the housing 10 can have various structures. In some embodiments, the housing 10 may include a first housing 11 and a second housing 12, which overlap each other, collectively defining a closed space for housing the battery cell assemblies 20. Of course, the housing 10 formed by the first housing 11 and the second housing 12 can have various shapes, such as a cylinder, a cuboid, etc. Multiple battery cell assemblies 20 can be arranged in any manner within the battery housing.

[0159] In the battery device 100, there can be one or more battery cell components 20. Multiple battery cell components 20 can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cell components 20 are connected in both series and parallel. Multiple battery cell components 20 can be directly connected in series, parallel, or in a mixed manner, and then the whole formed by multiple battery cell components 20 is housed in the housing 10. Of course, the battery device 100 can also be formed by first connecting multiple battery cell components 20 in series, parallel, or in a mixed manner to form a battery module, such as a battery module or battery pack. Multiple battery modules are then connected in series, parallel, or in a mixed manner to form a whole and housed in the housing 10.

[0160] The battery cell assembly 20 includes multiple battery cells 30. Figure 2 is an exploded view of a battery cell 30 as an example. The battery cell 30 includes a housing 31, a cover plate 33, an electrode assembly 32, and other functional components.

[0161] The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 is a hollow structure with an opening at one end, and the housing 31 is used to cooperate with the cover plate 33 to form an internal environment for accommodating the electrode assembly 32, electrolyte, and other functional components. The housing 31 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined according to the specific shape and size of the electrode assembly 32. The material of the housing 31 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here. The cover plate 33 is a component that covers the opening of the housing 31 to isolate the internal environment of the battery cell 30 from the external environment. The material of the cover plate 33 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0162] Figure 3 is a schematic diagram of an example electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0163] Example

[0164] 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.

[0165] Example 1

[0166] This embodiment provides a secondary battery.

[0167] [Preparation of the negative electrode sheet]

[0168] The compound shown in Formula II-1 and lithium hydroxide were added to deionized water at a molar ratio of 1:1 to obtain an aqueous solution containing the polymer monomer of Formula I-1. Then, graphite active material, binder SBR (styrene-butadiene rubber), conductive agent Super P and dispersant (sodium carboxymethyl cellulose) were added. The weight ratio of polymer monomer (Formula I-1), graphite active material, binder SBR (styrene-butadiene rubber), conductive agent Super P and dispersant (sodium carboxymethyl cellulose) was controlled to be 1:100:1:1:1. The mixture was stirred until the system was homogeneous to obtain a negative electrode slurry (solid content of 50%).

[0169] Then, the negative electrode slurry is uniformly coated onto one surface of the negative electrode current collector copper foil to form a negative electrode film layer, which is dried at 120°C. Then, the negative electrode slurry is uniformly coated onto the other surface of the negative electrode current collector copper foil to form a negative electrode film layer, which is dried at 120°C. After cold pressing (the thickness of the negative electrode film layer is 0.120mm), slitting, and cutting (the specification is 5cm*5cm) to obtain the negative electrode sheet.

[0170] [Preparation of the positive electrode sheet]

[0171] The positive electrode active material lithium iron phosphate, conductive agent Super P, and binder PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 97:1.5:1.5. NMP (N-methylpyrrolidone) solvent was added and stirred until the system was homogeneous to obtain a positive electrode slurry (solid content of 60%). The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cut into positive electrode sheets with a specification of 40mm×50mm.

[0172] [Isolation membrane]

[0173] Separator: A composite separator made of 9μm PE (polyethylene) + single-sided ceramic + double-sided adhesive, with a specification of 45mm×55mm.

[0174] Electrolyte

[0175] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixed solvent to obtain an electrolyte in which the concentration of lithium salt was 1 mol / L.

[0176] Preparation of the secondary battery: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes. The cells are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 100°C to remove water. Electrolyte is then injected and the casing is sealed to obtain a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation (0.02C current for 10 hours), shaping, and capacity testing to obtain the secondary battery.

[0177] Example 2

[0178] This embodiment provides a secondary battery. The difference from Embodiment 1 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 1 is 2:100:1:1:1.

[0179] Example 3

[0180] This embodiment provides a secondary battery. The difference from Embodiment 1 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 1 is 3:100:1:1:1.

[0181] Example 4

[0182] This embodiment provides a secondary battery. The difference from Embodiment 1 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 1 is 4:100:1:1:1.

[0183] Example 5

[0184] This embodiment provides a secondary battery. The difference from Embodiment 1 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 1 is 5:100:1:1:1.

[0185] Example 6

[0186] This embodiment provides a secondary battery. The difference from Embodiment 1 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-2, and the structural formula of the polymer monomer is as shown in Formula I-2.

[0187] Example 7

[0188] This embodiment provides a secondary battery. The difference from Embodiment 6 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 2 is 2:100:1:1:1.

[0189] Example 8

[0190] This embodiment provides a secondary battery. The difference from Embodiment 6 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 2 is 3:100:1:1:1.

[0191] Example 9

[0192] This embodiment provides a secondary battery. The difference from Embodiment 6 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 2 is 4:100:1:1:1.

[0193] Example 10

[0194] This embodiment provides a secondary battery. The difference from Embodiment 6 is that the proportions of the raw materials in the negative electrode slurry are different. Specifically, the weight ratio of the polymer monomer, graphite active material, binder, conductive agent, and dispersant prepared in Embodiment 2 is 5:100:1:1:1.

[0195] Example 11

[0196] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-3, and the structural formula of the polymer monomer is as shown in Formula I-3.

[0197] Example 12

[0198] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-4, and the structural formula of the polymer monomer is as shown in Formula I-4.

[0199] Example 13

[0200] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-5, and the structural formula of the polymer monomer is as shown in Formula I-5.

[0201] Example 14

[0202] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-6, and the structural formula of the polymer monomer is as shown in Formula I-6.

[0203] Example 15

[0204] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-7, and the structural formula of the polymer monomer is as shown in Formula I-7.

[0205] Example 16

[0206] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-8, and the structural formula of the polymer monomer is as shown in Formula I-8.

[0207] Example 17

[0208] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-9, and the structural formula of the polymer monomer is as shown in Formula I-9.

[0209] Example 18

[0210] This embodiment provides a secondary battery. The difference from Embodiment 3 is that the structural formula of the polymer monomer is different. Specifically, the compound shown in Formula II-1 is replaced with the compound shown in Formula II-10, and the structural formula of the polymer monomer is as shown in Formula I-10.

[0211] Comparative Example 1

[0212] This comparative example provides a secondary battery. The difference from Example 1 is that no polymeric monomer is added to the negative electrode; specifically:

[0213] Negative electrode plate:

[0214] Graphite active material, binder SBR (styrene-butadiene rubber), conductive agent Super P, and dispersant (sodium carboxymethyl cellulose) were mixed evenly in a weight ratio of 100:1:1:1. Deionized water was added as a solvent and stirred until the system was homogeneous to obtain a negative electrode slurry (solid content of 50%). The negative electrode slurry was then uniformly coated onto one surface of the negative electrode current collector copper foil to form a negative electrode film layer, which was dried at 120°C. The negative electrode slurry was then uniformly coated onto the other surface of the negative electrode current collector copper foil to form a negative electrode film layer, which was dried at 120°C. The film was then cold-pressed (with a negative electrode film thickness of 0.120 mm), slit, and cut into sheets (5 cm * 5 cm) to obtain the negative electrode sheet.

[0215] Performance testing

[0216] (1) Initial Coulomb efficiency test:

[0217] At 25℃, the charging capacity of the cell during activation is recorded as C1. After activation, the cell is charged to 3.65V at 0.5C and then charged to 0.05C at a constant voltage to obtain the charging capacity C2. It is then discharged to 2.5V at 0.5C and then discharged to 2.0V at 0.04C to obtain the discharge capacity D1.

[0218] Initial Coulomb efficiency = D1 / (C1+C2).

[0219] (2) Loop Test

[0220] The battery cell was placed in a 60°C hot box and subjected to 1C / 1C accelerated cycling for 800 cycles. The test voltage was 2.5V-3.65V, and the cycle was performed at 100% DOD (Depth of Discharge).

[0221] (3) Storage test

[0222] The battery cells were placed in a 60℃ hot box and removed after 90 days to test their discharge capacity at 25℃. The capacity testing procedure was as follows: at 25℃, the activated battery cells were discharged at 0.5C to 2.5V, then discharged at 0.04C to 2.0V; charged at 0.5C to 3.65V, then charged at a constant voltage to 0.05C to obtain the charging capacity; discharged at 0.5C to 2.5V, then discharged at 0.04C to 2.0V to obtain the discharge capacity.

[0223] The capacity retention rate is calculated as follows:

[0224] The 90d discharge capacity refers to the discharge capacity of a battery cell after it has been placed in a 60℃ hot box for 90 days and then tested at 25℃.

[0225] Initial discharge capacity refers to the discharge capacity of the battery cell before it undergoes storage testing.

[0226] The performance parameters of the secondary batteries provided in Examples 1-18 and Comparative Example 1 are shown in Table 1.

[0227] Table 1

[0228] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material and a polymer, wherein the polymer monomer is shown in Formula I. R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R2 includes a lithium-ionized acidic group, and n is a natural number ≤ 5.

2. The secondary battery as described in claim 1, characterized in that, The R2 includes either -COOLi or -SO3Li.

3. The secondary battery as described in claim 1 or 2, characterized in that, R1 includes any one of hydrogen, amino-substituted C1-C4 alkyl, hydroxy-substituted C1-C4 alkyl, and C1-C4 alkyl.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The value of n is 0 or 1.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The polymeric monomer comprises at least one of the compounds shown in Formula I-1 to Formula I-10:

6. The secondary battery as described in claims 1 to 5, characterized in that, At least a portion of the polymer monomers are connected to the negative electrode active material by at least one chemical bond, namely ionic bonds or hydrogen bonds.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The mass ratio of the negative electrode active material to the polymer is 100:(0.5-5).

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The negative electrode film layer also includes at least one of a binder, a dispersant, and a conductive agent.

9. The secondary battery as described in claim 8, characterized in that, The mass ratio of the negative electrode active material to the binder, the dispersant, and the conductive agent is 100:(0.5-2):(0.5-2):(0.1-2).

10. The secondary battery according to any one of claims 1 to 9, characterized in that, At least a portion of the surface of the negative electrode film is covered with an SEI film, the SEI film containing lithium-ionized acidic groups.

11. A method for preparing a secondary battery, characterized in that, Includes the following steps: The compound with the general chemical formula shown in Formula II is reacted with lithium hydroxide in a solution system to prepare the polymer monomer; R1 includes C1 to C1 substituted with hydrogen or amino groups. 10 Alkyl or hydroxyl substituted C1-C 10 Alkyl groups and C1-C 10 Any of the alkyl groups, R3 includes an acidic group, and n is a natural number ≤ 5; A negative electrode slurry containing the polymer monomer and the negative electrode active material is prepared, and the negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer, so as to prepare a negative electrode sheet. The negative electrode and the positive electrode are assembled to prepare a secondary battery.

12. The method for preparing a secondary battery as described in claim 11, characterized in that, The R3 includes either a carboxyl group or a sulfonic acid group.

13. The method for preparing a secondary battery as described in claim 11 or 12, characterized in that, The molar ratio of the compound represented by Formula II to the lithium hydroxide is 1:(0.9-1.1).

14. A battery device, characterized in that, This includes multiple secondary batteries as described in any one of claims 1-10 or secondary batteries prepared by the preparation method described in any one of claims 11-13.

15. An electrical appliance, characterized in that, This includes the secondary battery as described in any one of claims 1-10, the secondary battery prepared by the method described in any one of claims 11-13, or the secondary battery as described in claim 14.

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