Battery cell and preparation method thereof, battery device, and electrical device

Abstract

A battery cell (30) and preparation method thereof, a battery device (100), and an electrical device are provided. The battery cell (30) 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, and the negative electrode film layer comprises a negative electrode active material and a polymer. In the provided battery cell (30), the polymer has good elasticity and toughness. On the one hand, the polymer can buffer and absorb internal stress generated by volume changes, thereby reducing damage to the structure of the negative electrode active material. On the other hand, the polymer can be in close contact with the negative electrode active material, so that the negative electrode active material is not prone to excessive expansion, thereby effectively improving the overall stability of the negative electrode sheet. Based on this, the polymer with specific polymer structural units has a significantly effect in suppressing volume expansion of the negative electrode active material, thereby effectively prolonging the cycle life of the battery.

Description

A battery cell and its preparation method, a battery device, and an electrical device thereof.

[0001] This application claims priority to Chinese Patent Application No. 202411547240.3, filed on October 31, 2024, entitled "A Battery Cell and its Preparation Method, Battery Device, and Electrical Device", 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 battery cell and its preparation method, a battery device, and an electrical device. 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] As the core of modern energy storage systems, rechargeable batteries possess outstanding characteristics such as light weight, no pollution, and no memory effect, and are widely used in portable electronic devices, electric vehicles, and other fields. With the continuous expansion of the application scope of rechargeable batteries, correspondingly higher requirements are being placed on battery performance.

[0005] For example, as the application range of batteries continues to expand, cycle life is one of the important indicators for measuring battery performance. A longer cycle life means the battery can maintain high performance over more charge-discharge cycles, which not only extends battery lifespan but also promotes its widespread application. However, the cycle life of current batteries needs further improvement.

[0006] Application content

[0007] The purpose of this application is to provide a battery cell and its preparation method, a battery device, and an electrical device, including but not limited to solving the problem of unsatisfactory cycle life of the battery cell.

[0008] The technical solution adopted in the embodiments of this application is:

[0009] In a first aspect, a battery cell is provided, comprising a negative electrode sheet, the negative electrode sheet comprising 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 comprising a negative electrode active material and a polymer, the polymer having a polymeric structural unit as shown in Formula I:

[0010] Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - It consists of any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of R1, R2, and R3 has a -(CH2) group. nCOO - n is a natural number ≤ 10;

[0011] M includes any one of Li, Na, and K;

[0012] The amount of M, ax, is related to the -(CH2) content in the polymer. n COO - The ratio of their quantities is (0.9-1.1):1;

[0013] x is a positive integer ≤ 1000.

[0014] In this embodiment, the polymer and the negative electrode active material are used in the negative electrode film layer of the negative electrode sheet. The polymer has good elasticity and flexibility. On the one hand, when the negative electrode active material undergoes volume change due to the insertion and extraction of active ions, the polymer can effectively buffer and absorb the internal stress generated by the volume change, thereby reducing the damage to the structure of the negative electrode active material. On the other hand, the polymer can be in close contact with the negative electrode active material. Thus, when the negative electrode active material undergoes volume expansion due to the insertion of active ions, the polymer will generate an inward binding force, making it difficult for the negative electrode active material to expand excessively. This physical barrier effect keeps the volume expansion of the negative electrode active material within a relatively small range, thereby effectively improving the overall stability of the negative electrode sheet. Based on this, the polymer of the specific polymer structure unit plays a significant positive role in suppressing the volume expansion of the negative electrode active material, thereby effectively extending the cycle life of the battery.

[0015] In some embodiments, R1, R2, and R3 are each independently selected from -(CH2). n COO - It can be any one of alkyl groups and hydrogen atoms from C1 to C2, where n is a natural number ≤ 4.

[0016] These groups can improve the interaction between the polymer and the negative electrode active material, thus making it more conducive for the polymer to exert a binding effect on the negative electrode active material, reducing the volume expansion of the negative electrode sheet, and improving the cycle performance of the battery.

[0017] In some embodiments, the amount of M, ax, is related to the amount of -(CH2) in the polymer. n COO - The ratio of the quantities is (1.05-1.08):1.

[0018] Controlling the metal ions and -(CH2) groups in polymers n COO - The ratio of the quantities means that the amount of metal ions M in the polymer is excessive, so the polymer is alkaline, which in turn makes the negative electrode film alkaline, thereby improving the processing performance of the negative electrode film.

[0019] In some embodiments, the aggregate structural unit includes at least one of the structural units shown in Formula I-1 to Formula I-7:

[0020] In Equations I-1 to I-7, b is 0.9-1.1.

[0021] These polymers can effectively bind the negative electrode active material, making it less prone to excessive expansion and thus preventing the negative electrode active material from being crushed and detached, resulting in high cycle performance of the battery.

[0022] In some embodiments, the mass ratio of the negative electrode active material to the polymer is (93-97):(0.5-4).

[0023] By controlling the mass ratio of polymer to negative electrode active material within the above range, the volume change of negative electrode active material during charging and discharging can be effectively suppressed, resulting in higher cycle performance of the battery cell.

[0024] In some embodiments, at least a portion of the polymer is connected to the negative electrode active material via at least one chemical bond selected from ionic bonds and hydrogen bonds.

[0025] This bonding allows the negative electrode active material and the polymer to come into close contact, making it easier for the polymer to bind the negative electrode active material, limiting its excessive expansion, thereby reducing the shedding and fragmentation of the negative electrode active material and improving the battery's cycle performance and capacity retention.

[0026] In some embodiments, the negative electrode film layer further includes styrene-butadiene rubber, wherein the number average molecular weight of the styrene-butadiene rubber is 20,000-80,000.

[0027] When the number average molecular weight of styrene-butadiene rubber is within the above range, it means that the styrene-butadiene rubber molecular chain has sufficient length, thereby increasing the binding effect on the negative electrode active material and reducing the volume expansion of the negative electrode active material.

[0028] In some embodiments, the total mass of styrene-butadiene rubber and polymer in the negative electrode film layer is 1wt%-7wt%.

[0029] Styrene-butadiene rubber has good elasticity and flexibility, which can effectively buffer the volume expansion of the negative electrode active material caused by the insertion and extraction of active ions.

[0030] In some embodiments, the mass ratio of styrene-butadiene rubber to polymer is 1:(0.3-2).

[0031] By using styrene-butadiene rubber and polymers to compound the negative electrode active material, the stress generated during the volume expansion process can be distributed more evenly throughout the entire negative electrode system. This makes the negative electrode active material less prone to excessive expansion and damage, improving the overall stability of the negative electrode sheet structure. As a result, the battery cell exhibits higher cycle capability.

[0032] In some embodiments, the negative electrode active material includes at least one of carbon materials, silicon-based materials, and tin-based materials.

[0033] These negative electrode active materials can effectively accept and store active ions, and can also effectively release these active ions during charging, resulting in good electrochemical performance of the battery cells.

[0034] In some embodiments, the carbon material includes graphite, which has a BET specific surface area of ​​0.8-5 m². 2 / g.

[0035] Within the aforementioned specific surface area range, graphite has a relatively large number of active sites, which helps the polymer to exert its binding effect on it and reduce the volume expansion of graphite.

[0036] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the BET specific surface area of ​​the silicon-based material is 5-100 m². 2 / g.

[0037] Within the aforementioned specific surface area range, it means that silicon-based materials have more active sites, which not only helps polymers to exert a binding effect on them and reduce the free expansion of silicon-based materials, but also increases their ability to store active ions and improves their specific capacity.

[0038] In some embodiments, the negative electrode film layer further includes at least one of a dispersant and a conductive agent.

[0039] Adding the above components, such as dispersants and conductive agents, to the negative electrode film can improve the uniformity and conductivity of the negative electrode sheet.

[0040] In some embodiments, based on the total mass of the negative electrode film, the mass percentage of the dispersant is 0.3wt%-1.5wt%, and the mass percentage of the conductive agent is 0.3wt%-1.5wt%.

[0041] Within the aforementioned range, the components, such as dispersants and conductive agents, can fully exert their synergistic effect, thereby obtaining a negative electrode sheet with uniform distribution and good conductivity.

[0042] Secondly, this application provides a method for preparing a battery cell, comprising the following steps:

[0043] An aqueous negative electrode slurry containing polymeric monomers is prepared, and the aqueous negative electrode slurry is coated onto at least one side of a negative electrode current collector to form a negative electrode film layer, thereby preparing a negative electrode sheet; wherein, the general chemical formula of the polymeric monomer is shown in Formula II:

[0044] Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - It consists of any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of R1, R2, and R3 has a -(CH2) group. n COO - n is a natural number ≤ 10;

[0045] M includes any one of Li, Na, and K; a is related to -(CH2) in the polymer monomer. n COO - The ratio of their quantities is 1:1.

[0046] Battery cells are prepared using negative electrode sheets.

[0047] The method for preparing a battery cell provided in this application involves adding the polymeric monomer shown in Formula II to an aqueous negative electrode slurry, coating the aqueous negative electrode slurry onto the surface of a negative electrode current collector to form a negative electrode film, obtaining a negative electrode sheet, assembling the negative electrode sheet with a positive electrode sheet and a separator, and then performing a formation treatment to polymerize the polymeric monomer to form a polymer containing the polymeric structural unit shown in Formula I, thereby effectively preparing a battery cell with the performance described above.

[0048] In some embodiments, the polymeric monomer comprises at least one of the compounds represented by Formula II-1 to Formula II-7:

[0049] Wherein, in formulas II-1 to II-7: b is 0.9-1.1.

[0050] In the embodiments of this application, the polymer monomers shown in Formulas II-1 to II-7 can form polymers containing polymer structural units shown in Formula I during the formation stage, thereby fully exerting the binding effect on the negative electrode active material, limiting the excessive expansion of the negative electrode active material, and thus improving the overall stability of the negative electrode sheet structure, so that the battery exhibits high cycle performance.

[0051] In some embodiments, the aqueous solution of the polymeric monomer at a concentration of 20 wt% has a pH of 7-14.

[0052] The monomers are alkaline, which makes the negative electrode slurry also alkaline. This helps to improve the dispersibility of the components in the negative electrode slurry and obtain a uniformly dispersed negative electrode film.

[0053] In some embodiments, the pH value of the aqueous negative electrode slurry is 7-9.

[0054] Within the above range, it means that the components in the negative electrode slurry are relatively stable, which gives the negative electrode slurry better processing performance and obtains a negative electrode sheet with stable structure and uniform distribution.

[0055] In some embodiments, the preparation process of the polymeric monomer is as follows:

[0056] A compound with the general chemical formula shown in Formula III is reacted with an alkali metal hydroxide in an aqueous solution to obtain a polymeric monomer.

[0057] Among them, A1, A2, and A3 are each independently selected from -(CH2). n The atom is selected from COOH, an alkyl group (C1-C5), and a hydrogen atom, and at least one of A1, A2, and A3 has a -(CH2) group. n COOH, where n is a natural number ≤ 10.

[0058] The compound shown in Formula III reacts with an alkali metal hydroxide through an acid-base neutralization reaction to obtain the polymeric monomer shown in Formula II, thereby allowing the polymeric monomer to polymerize in the formation stage to obtain a polymer containing the polymeric structural unit shown in Formula I.

[0059] Thirdly, this application provides a battery device including the battery cell described in the above embodiments.

[0060] Fourthly, this application provides an electrical device, including a battery cell or a battery device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0061] 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:

[0062] Figure 1 is an exploded view of the battery device provided in an embodiment of this application;

[0063] Figure 2 is an exploded view of a single battery cell provided in an embodiment of this application;

[0064] Figure 3 shows a schematic diagram of an embodiment of an electrical device in which a single battery cell serves as a power source, according to an embodiment of this application.

[0065] Figure 4 is an infrared spectrum test diagram of the negative electrode sheet of Example 1 and Comparative Example 1 of this application.

[0066] 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

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0072] 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).

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0077] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] In the embodiments of this application, the term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, or combinations thereof. Phrases containing this term, such as "C1-C5 alkyl," refer to alkyl groups containing 1 to 5 carbon atoms, and each occurrence can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, or C5 alkyl.

[0082] In this embodiment of the application, the battery cell can be a secondary battery, which 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.

[0083] 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.

[0084] In battery structure, the negative electrode is a crucial component, profoundly impacting overall battery performance. During repeated charge-discharge cycles, the active material of the negative electrode undergoes volume changes due to the insertion and extraction of active ions, easily leading to structural collapse and pulverization. This results in rapid capacity decay and significantly shortens the battery's cycle life. Furthermore, these volume changes damage the SEI film. When the SEI film ruptures, new electrolyte comes into contact with the fresh surface of the negative electrode active material, causing SEI reformation and continuously consuming active lithium. Over time, this repeated SEI rupture and repair process leads to rapid capacity decay, further shortening the battery's cycle life. Therefore, in-depth research and optimization of the negative electrode are of great significance for the development of battery technology, especially for improving its cycle performance.

[0085] Based on this, this application provides a battery cell that effectively improves the cycle life of the battery by optimizing the negative electrode.

[0086] Next, we will provide a detailed introduction to the negative electrode, positive electrode, separator, and electrolyte components of a single battery cell.

[0087] [Negative electrode plate]

[0088] The negative electrode sheet 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, and the polymeric structural unit is shown in Formula I:

[0089] Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - It consists of any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of R1, R2, and R3 has a -(CH2) group. n COO - n is a natural number ≤ 10;

[0090] M includes any one of Li, Na, and K;

[0091] The amount of M, ax, is related to the -(CH2) content in the polymer. n COO - The ratio of their quantities is (0.9-1.1):1;

[0092] x is a positive integer ≤ 1000.

[0093] In this embodiment, a polymer containing the polymeric structural unit shown in Formula I is added to the negative electrode film layer. Since bonds can be formed between two or more polymers (such as metal ions M...),... + With -(CH2)n COO - (Forming MO bonds) thus obtains a polymer with a network structure. Due to the good elasticity and toughness of the polymer, on the one hand, when the volume of the negative electrode active material expands and contracts, the polymer can deform accordingly. In this way, the polymer can adapt well to the volume change of the negative electrode active material, thereby maintaining close contact with the negative electrode active material. Thus, the polymer can provide an effective buffering effect to reduce the internal stress of the negative electrode active material caused by volume change and reduce the free expansion degree of the negative electrode active material. On the other hand, the network structure of the polymer can form a strong physical constraint on the negative electrode active material, thereby limiting the excessive movement of the negative electrode active material during volume change, such as excessive diffusion and displacement, excessive contraction and separation. This effectively improves the overall structural stability of the negative electrode active material and effectively prevents the negative electrode active material from falling off and being lost during charging and discharging, which helps to improve the cycle performance of the battery.

[0094] In one embodiment, the polymer can coat the surface of the negative electrode active material. Due to its network structure, the polymer effectively suppresses the volume expansion of the negative electrode active material during charge and discharge, reducing direct contact between the negative electrode active material and the electrolyte, thereby reducing side reactions and improving battery cycle stability. In another embodiment, the polymer is embedded in the gaps between the negative electrode active material particles, interpenetrating with the negative electrode active material to form an interlocking structure. This structure helps the polymer provide effective buffering in local areas, reducing local stress concentration and making the overall structure of the negative electrode sheet less prone to damage. In yet another embodiment, the polymer exerts its binding properties, thereby automatically repairing cracks and defects in the active material when it expands in volume, helping to improve the structural integrity of the negative electrode sheet and positively contributing to improved battery cycle life and safety.

[0095] Based on this, adding the aforementioned polymer to the negative electrode film layer not only restrains the volume expansion of the negative electrode active material in multiple directions, limiting the free movement and expansion of the particles during volume expansion and thus reducing the magnitude of volume expansion, effectively enhancing the stability of the negative electrode sheet; but also, the polymer's tight bonding with the negative electrode active material provides targeted buffering for areas of greater expansion, thereby reducing local stress concentration and making the negative electrode sheet less prone to localized damage. This allows the stress generated by the intercalation and deintercalation of active ions in the negative electrode active material to be distributed relatively evenly across the negative electrode sheet, suppressing uneven volume expansion and excessive expansion. Therefore, the presence of the polymer enables the negative electrode active material to remain relatively stable during repeated cycling, effectively improving the battery's cycle life, reducing SEI film rupture and recombination, slowing electrolyte consumption, and further extending the battery's cycle life.

[0096] In this application's technical solution, the polymer contains metal ions, such as lithium ions, sodium ions, and potassium ions, which gives the polymer good ion conductivity, making charge transport in the negative electrode sheet smoother. This helps optimize the ion transport path, reduce the battery's internal resistance, and improve the battery's charge and discharge capabilities. Furthermore, these metal ions can optimize the formation of the SEI film, obtaining a stable and dense SEI film, thereby reducing direct contact between the negative electrode active material and the electrolyte, and reducing the occurrence of side reactions. This has a significant positive effect on improving battery safety and cycle performance.

[0097] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction. The negative electrode film layer can be disposed on one side of the negative electrode current collector along its own thickness direction, or it can be disposed on both surfaces of the negative electrode current collector along its own thickness direction.

[0098] 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 side 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.

[0099] 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.

[0100] 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.

[0101] In some embodiments, R1, R2, and R3 are each independently selected from -(CH2). n COO - It can be any one of alkyl groups and hydrogen atoms from C1 to C2, where n is a natural number ≤ 4.

[0102] For example, n can be a typical but non-restrictive value such as 0, 1, 3, 4, etc.

[0103] The polymer contains the group -(CH2). n COO -It can bond with metal ions M, thereby giving the polymer good ionic conductivity. This allows active ions to migrate more quickly between the negative electrode and the electrolyte during battery charging and discharging, reducing the battery's internal resistance and enabling the battery cell to exhibit high charging and discharging efficiency.

[0104] In some embodiments, the amount of M, ax, is related to the amount of -(CH2) in the polymer. n COO - The ratio of the quantities is (1.05-1.08):1.

[0105] Controlling the interaction between metal ion M and -(CH2) n COO - If the ratio of the quantities is within the above range, it means that the metal ions M in the polymer are relatively excessive. This makes the polymer more alkaline, which can improve the pH environment of the negative electrode film. This allows the components in the negative electrode film to exist in a relatively uniform form, improves the processing performance of the negative electrode film, and obtains a negative electrode sheet with uniform thickness and stable structure.

[0106] In some embodiments, the aggregate structural unit includes at least one of the structural units shown in Formula I-1 to Formula I-7:

[0107] In Equations I-1 to I-7, b is 0.9-1.1.

[0108] In the embodiments of this application, the polymer formed by the polymer structural units shown in Formulas I-1 to I-7 has good contact with the negative electrode material, thereby fully exerting the binding effect on the negative electrode active material, effectively limiting its expansion degree, and improving the cohesive force of the negative electrode sheet. As a result, the negative electrode active material is not easily damaged or crushed, and is not easily detached from the negative electrode current collector. This helps to improve the stability of the overall structure of the negative electrode sheet, so that the battery cell has high cycle performance and service life.

[0109] In some embodiments, the mass ratio of the negative electrode active material to the polymer is (93-97):(0.5-4). Exemplarily, the mass percentage of the polymer can be a typical but not limiting value such as 0.5, 1, 2, 3, or 4. The mass percentage of the negative electrode active material can be a typical but not limiting value such as 93, 94, 95, 96, or 97.

[0110] By controlling the mass ratio of the negative electrode active material to the polymer within the aforementioned range, a network structure can be formed between the polymers through bonding. This significantly inhibits the volume expansion of the negative electrode active material, making it less prone to excessive expansion and contraction. This effectively enhances the structural stability of the negative electrode sheet. Furthermore, this strong inhibition also improves the integrity of the SEI film, reducing repeated rupture and regeneration of the SEI film caused by volume changes in the negative electrode active material. This reduces the irreversible loss of active ions, which plays a significant positive role in improving the cycle performance and coulombic efficiency of the battery.

[0111] In some embodiments, at least a portion of the polymer is connected to the negative electrode active material via at least one chemical bond selected from ionic bonds and hydrogen bonds.

[0112] -(CH2) in the polymer n COO - M + The polymer 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 allows the polymer to be tightly bound to the negative electrode active material, which can not only limit the volume expansion of the negative electrode active material and improve the cohesive force of the negative electrode sheet, but also maintain the structural stability of the negative electrode sheet, reduce the shedding of the negative electrode active material and the damage to the electrode sheet, thereby extending the cycle life of the battery.

[0113] In addition, the bonds formed between the polymer monomers and the negative electrode active material can also serve as transport sites for active ions, enriching the transport channels for active ions and improving the charge and discharge efficiency of the battery.

[0114] In some embodiments, the negative electrode film layer further includes styrene-butadiene rubber, wherein the number average molecular weight of the styrene-butadiene rubber is 20,000-80,000.

[0115] Number-average molecular weight refers to the molecular weight averaged by the number of molecules. Specifically, it is the value obtained by dividing the total mass of all molecules in the system by the total number of molecules. As an example, the number-average molecular weight of styrene-butadiene rubber can be typical but not limiting values ​​such as 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, and 80,000.

[0116] In this paper, end-group analysis can be used to determine the number-average molecular weight of styrene-butadiene rubber. End-group analysis is a method to calculate the molecular weight of a polymer by measuring the number of functional groups at one or both ends of a molecule in a polymer sample.

[0117] Styrene-butadiene rubber (SBR) acts as a binder, tightly binding the negative electrode active material particles together. This helps improve the integrity of the negative electrode sheet and reduces capacity decay and performance degradation caused by the shedding of the negative electrode active material. In particular, SBR has good elasticity and toughness, effectively buffering the stress caused by volume changes in the negative electrode active material. This further reduces problems such as cracking and pulverization of the negative electrode active material caused by volume changes, thus significantly improving the battery's cycle life.

[0118] When the number-average molecular weight of styrene-butadiene rubber (SBR) is within the above range, it means that the SBR molecular chain has sufficient length, thereby providing high bonding performance and increasing the binding effect on the negative electrode active material, reducing the volume expansion of the negative electrode active material, and enabling the battery to exhibit high cycle performance.

[0119] In some embodiments, the total mass percentage of styrene-butadiene rubber and polymer in the negative electrode film layer is 1 wt% to 7 wt%. Exemplary examples show that the total mass percentage of styrene-butadiene rubber and polymer in the negative electrode film layer can be typical but not limiting values ​​such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, and 7 wt%.

[0120] Both polymers and styrene-butadiene rubber (SBR) possess good elasticity, which can synergistically mitigate the volume changes caused by the expansion and contraction of the negative electrode active material during charging and discharging. Specifically, the polymer has a network structure that can tightly encapsulate the negative electrode active material at the microscopic level, providing local elastic restraint. Meanwhile, SBR has good adhesion properties, which provide support and buffer for the entire negative electrode structure at the macroscopic level, making the negative electrode less prone to breakage due to volume changes. Thus, the combination of the two can effectively improve the volume expansion of the negative electrode active material, resulting in higher cohesion in the negative electrode. This has a significant positive effect on improving the integrity of the negative electrode structure and the cycle performance of the battery.

[0121] Furthermore, polymers contain the group -(CH2). n COO - The presence of metal ions (M) enables the polymer to form bonds with the negative electrode active material, and the polymer can also form hydrogen bonds with styrene-butadiene rubber (SBR). This improves the dispersion effect of SBR in the negative electrode active material and enhances the contact between SBR and the negative electrode active material. This, in turn, improves the adhesion properties of SBR and inhibits the volume expansion of the negative electrode active material.

[0122] By using styrene-butadiene rubber (SBR) and polymers in a compound, and controlling the total mass ratio of SBR and polymers within the aforementioned range, the stress generated by the negative electrode active material during volume expansion can be distributed more evenly throughout the entire negative electrode system. This makes the negative electrode active material less prone to excessive expansion and damage, improving the overall stability of the negative electrode sheet structure. As a result, the battery cell exhibits higher cycle life.

[0123] In some embodiments, the mass ratio of styrene-butadiene rubber to polymer is 1:(0.3-2). Exemplary examples include typical but non-limiting values ​​such as 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.5, and 1:2.

[0124] Controlling the mass ratio of styrene-butadiene rubber to polymer within the above range can not only significantly suppress the volume expansion of the negative electrode active material and improve the cohesive force of the negative electrode sheet, thus making the SEI film less prone to breakage during cycling, reducing the consumption of active ions, and giving the battery a higher cycle life and coulombic efficiency; it can also endow the negative electrode sheet with higher flexibility and mechanical strength, making the negative electrode sheet less prone to breakage or damage, and improving the reliability and durability of the battery.

[0125] In some embodiments, the mass ratio of styrene-butadiene rubber to polymer is 1:(0.8-1.5). Exemplary examples include typical but non-limiting values ​​such as 1:0.8, 1:1, 1:1.3, and 1:1.5.

[0126] By controlling the mass ratio of styrene-butadiene rubber (SBR) to polymer within the aforementioned range, on the one hand, SBR and polymer can bind the negative electrode active material. Specifically, the polymer can tightly encapsulate the negative electrode active material at the microscopic level, thereby effectively suppressing its volume expansion during the active ion insertion / extraction process. On the other hand, SBR enhances the overall mechanical strength of the negative electrode sheet at the macroscopic level, making it less prone to cracking or deformation. On the other hand, due to the network structure of the polymer and the hydrogen bond between the polymer and SBR, the polymer and SBR can tightly connect the negative electrode active material. Thus, the two work together to enhance their bonding ability, strengthening the adhesion between the negative electrode active materials and between the negative electrode active material and the current collector, further improving the cohesion and structural integrity of the negative electrode sheet, and significantly improving the reliability and cycle performance of the battery.

[0127] In some embodiments, the negative electrode active material includes at least one of carbon materials, silicon-based materials, and tin-based materials.

[0128] Carbon materials have high electrical conductivity, while silicon-based and tin-based materials have high theoretical specific capacity and suitable lithium intercalation potential. As negative electrodes, these materials can not only accept and store active ions well, but also release these active ions well during charging, resulting in good electrochemical performance of the battery cell.

[0129] In the embodiments of this application, specific surface area refers to the surface area per unit mass or unit volume of a material.

[0130] In this paper, the BET nitrogen adsorption method was used to test the comparative surface area.

[0131] In some embodiments, the carbon material includes graphite, which has a BET specific surface area of ​​0.8-5 m². 2 / g.

[0132] In some embodiments, the carbon material includes graphite, which has a BET specific surface area of ​​1.2-2.5 m². 2 / g.

[0133] For example, the specific surface area of ​​graphite can be 0.8 m². 2 / g, 1m 2 / g, 1.2m 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g and other typical but non-restrictive values.

[0134] Graphite within the aforementioned specific surface area range has a large number of active sites, which in turn provides the polymer with a large number of contact sites and a large contact area. This not only helps the polymer to be uniformly dispersed on the graphite surface, thereby exerting a physical binding effect on it and reducing its excessive expansion, but also effectively transfers stress, reduces local stress concentration, and makes the overall structure of the negative electrode sheet less prone to damage.

[0135] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the BET specific surface area of ​​the silicon-based material is 5-100 m². 2 / g.

[0136] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the BET specific surface area of ​​the silicon-based material is 5-50 m². 2 / g.

[0137] For example, the specific surface area of ​​silicon-based materials can be 5m². 2 / g, 10m 2 / g、20m2 / g、30m 2 / g、40m 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g, 100m 2 / g and other typical but non-restrictive values.

[0138] Silicon-based materials within the aforementioned specific surface area range have more active sites, thereby increasing the contact effect between the polymer and the material. This plays a significant positive role in enabling the polymer to exert its binding effect and reducing the volume expansion of the silicon-based material, thus significantly improving the cycle performance of the battery. Moreover, more active sites mean that, under the same mass, silicon-based materials can store more active ions, thereby effectively improving the energy density of the battery.

[0139] In some embodiments, the negative electrode film layer further includes at least one of a dispersant and a conductive agent.

[0140] Adding the above components, such as dispersants and conductive agents, to the negative electrode film can improve the uniformity and conductivity of the negative electrode sheet.

[0141] 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.

[0142] As an example, dispersants include, but are not limited to, sodium carboxymethyl cellulose.

[0143] In some embodiments, based on the total mass of the negative electrode film, the mass percentage of the dispersant is 0.3 wt%-1.5 wt%, and the mass percentage of the conductive agent is 0.3 wt%-1.5 wt%. Exemplarily, the mass percentage of the dispersant can be typical but not limiting values ​​such as 0.3 wt%, 0.5 wt%, 1 wt%, 1.2 wt%, and 1.5 wt%. The mass percentage of the conductive agent can be typical but not limiting values ​​such as 0.3 wt%, 0.5 wt%, 1 wt%, 1.2 wt%, and 1.5 wt%.

[0144] By controlling the mass ratio of negative electrode active material, dispersant, and conductive agent within the above range, the dispersant and conductive agent can fully exert their synergistic effect, thereby obtaining a negative electrode sheet with more uniform distribution of each component and excellent conductivity, thus improving the overall performance of the battery cell.

[0145] [Positive electrode plate]

[0146] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The aforementioned "positive electrode film layer disposed on at least one side of the positive current collector" means that the positive electrode film layer can be disposed on one side of the positive current collector along its own thickness direction, or it can be disposed on both surfaces of the positive current collector along its own thickness direction.

[0147] This application does not impose any particular limitation on the positive electrode current collector, as long as it achieves 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 side 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] [Isolation membrane]

[0153] 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.

[0154] 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.

[0155] 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.

[0156] [Electrolytes]

[0157] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0158] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] The second aspect of this application provides a method for preparing a battery cell, comprising the following steps:

[0163] Step S10: Prepare an aqueous negative electrode slurry containing polymeric monomers, and coat the aqueous negative electrode slurry onto at least one side of the negative electrode current collector to form a negative electrode film layer, thereby preparing a negative electrode sheet; wherein, the general chemical formula of the polymeric monomer is shown in Formula II:

[0164] Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - It consists of any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of R1, R2, and R3 has a -(CH2) group. n COO - n is a natural number ≤ 10;

[0165] M includes any one of Li, Na, and K; a is related to -(CH2) in the polymer monomer. n COO - The ratio of their quantities is (0.9-1.1):1.

[0166] Step S20: Prepare a battery cell using the above-mentioned negative electrode sheet.

[0167] The method for preparing a battery cell provided in this application involves adding the polymeric monomer shown in Formula II to a negative electrode slurry, coating the negative electrode slurry onto the surface of a negative electrode current collector to form a negative electrode film, obtaining a negative electrode sheet, assembling the negative electrode sheet with a positive electrode sheet, and performing a formation treatment to polymerize the polymeric monomer to form a polymer containing the polymeric structural unit shown in Formula I, thereby effectively preparing a battery cell with the properties described above.

[0168] In some embodiments, in step S10, the polymerizing monomer includes at least one of the compounds represented by formulas II-1 to II-7:

[0169] In Equations II-1 to II-7, b is 0.9-1.1.

[0170] In this embodiment, the polymeric monomers shown in Formulas II-1 to II-7 can form polymers containing polymeric structural units shown in Formula I during the formation stage. This network-structured polymer not only fully exerts its binding effect on the negative electrode active material, limiting its excessive expansion and thus improving the overall stability of the negative electrode sheet, resulting in higher cycle performance, but also possesses good ion transport capabilities, enabling active ions to transport rapidly within the negative electrode sheet, reducing the battery's internal resistance and improving its charge / discharge capacity. Furthermore, the polymers formed by these monomers can optimize the formation of the SEI film, thereby obtaining a stable and dense SEI film that is less prone to rupture during cycling, reducing the consumption of active ions. This significantly improves the battery's coulombic efficiency, safety, and cycle performance.

[0171] In some embodiments, the preparation process of the polymeric monomer in step S10 is as follows:

[0172] Step S11: React the compound with the chemical formula shown in Formula III with an alkali metal hydroxide in an aqueous solution to obtain a polymeric monomer;

[0173] Among them, A1, A2, and A3 are each independently selected from -(CH2). n It consists of any one of COOH, C1-C5 alkyl groups, and hydrogen atoms, and at least one of A1, A2, and A3 has a -(CH2) group. n COOH, where n is a natural number ≤ 10.

[0174] In the embodiments of this application, the compound represented by Formula III and an alkali metal hydroxide are neutralized by acid and base to form a polymeric monomer represented by Formula II. This polymeric monomer can polymerize during the formation stage to form a polymer containing polymeric structural units represented by Formula I.

[0175] In some embodiments, in step S11, the alkali metal hydroxide includes at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide.

[0176] In some embodiments, in step S11, the molar ratio of the compound with the general chemical formula as shown in Formula III to the alkali metal hydroxide is (0.9-1.1):1.

[0177] In some embodiments, in step S11, the molar ratio of the compound with the general chemical formula as shown in Formula III to the alkali metal hydroxide is (1.05-1.1):1.

[0178] By controlling the molar ratio within the above range, the compound shown in Formula III can react fully with the alkali metal hydroxide, thus obtaining the polymer monomer shown in Formula II.

[0179] In some embodiments, in step S10, an aqueous negative electrode slurry containing polymeric monomers is prepared, and the aqueous negative electrode slurry is coated on at least one side of the negative electrode current collector to form a negative electrode film layer, thereby obtaining a negative electrode sheet. The specific process is as follows:

[0180] The components for preparing the negative electrode sheet, such as polymeric monomers, styrene-butadiene rubber, negative electrode active material, conductive agent and dispersant, are dispersed in a solvent (e.g. deionized water) to form a negative electrode slurry. The negative electrode slurry is coated on 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.

[0181] In some embodiments, in step S10, the aqueous solution of the polymeric monomer at a concentration of 20 wt% has a pH value of 7-14.

[0182] In some embodiments, in step S10, the concentration of the polymeric monomer in the aqueous solution is 20 wt% and the pH value is 9-13.

[0183] As an example, when the concentration of the aqueous solution containing the polymeric monomer is 20 wt%, its pH value can be a typical non-limiting value such as 7, 8, 9, 10, 11, 12, 13, 14, etc.

[0184] The polymer monomers are alkaline, which makes the negative electrode slurry alkaline. This not only helps to improve the dispersion of the components in the negative electrode slurry and obtain a uniformly dispersed negative electrode film, but also optimizes the formation of the SEI film to obtain a stable and dense SEI film, so that the battery cell has a higher cycle life and safety.

[0185] In some embodiments, in step S10, the pH value of the aqueous negative electrode slurry is 7-9. Exemplarily, the pH value of the aqueous negative electrode slurry can be a typical but non-limiting value such as 7, 7.5, 8, 8.5, or 9.

[0186] Within the aforementioned pH range, the dispersibility of components such as negative electrode active material, conductive agent, and styrene-butadiene rubber in the negative electrode slurry is significantly improved, which helps to reduce particle agglomeration of negative electrode active material, obtain a stable and uniform negative electrode slurry, thereby effectively improving the processing performance of the negative electrode slurry and obtaining a negative electrode sheet with stable structure and uniform distribution.

[0187] In some embodiments, in step S20, 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 battery cell is obtained. The shape of the battery cell is not particularly limited; it can be cylindrical, square, or any other arbitrary shape.

[0188] A third aspect of this application provides a battery device including the battery cell described in the above embodiments.

[0189] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0190] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0191] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0192] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0193] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0194] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0195] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0196] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0197] 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.

[0198] A fourth aspect of this application provides an electrical device, including a battery cell or a battery device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0199] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, 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.

[0200] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery device, and power-consuming device provided in the embodiments of this application.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] Example

[0207] 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.

[0208] Example 1

[0209] This embodiment provides a single battery cell.

[0210] [Preparation of the negative electrode sheet]

[0211] The compound shown in Formula III-3 was added to deionized water at a molar ratio of 1:2.1 with lithium hydroxide to obtain an aqueous solution containing the polymer monomer of Formula II-3. Then, graphite active material (with a specific surface area of ​​2m²) was added. 2 The graphite active material, polymer monomer (Formula II-1), binder SBR (styrene-butadiene rubber), conductive agent carbon black, and dispersant (sodium carboxymethyl cellulose) are mixed in a weight ratio of 97:1:1:0.5:0.5. The mixture is stirred until the system is homogeneous to obtain the negative electrode slurry (solid content of 50%).

[0212] The negative electrode slurry is then uniformly coated onto one side of the negative electrode current collector copper foil to form a negative electrode film layer, which is dried at 120°C. The negative electrode slurry is then uniformly coated onto the other side of the negative electrode current collector copper foil to form a negative electrode film layer, which is dried at 120°C. The negative electrode film layer is then cold-pressed (with a thickness of 0.120 mm), slit, and cut into sheets (5 cm x 5 cm) to obtain the negative electrode sheet.

[0213] [Preparation of the positive electrode sheet]

[0214] 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.

[0215] [Isolation membrane]

[0216] Separator: A composite separator made of 9μm PE (polyethylene) + single-sided ceramic + double-sided adhesive, with a specification of 45mm×55mm.

[0217] Electrolyte

[0218] 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.

[0219] Preparation of battery cells: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes. They 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 moisture. 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 battery cell.

[0220] Examples 2-12

[0221] Examples 2-12 provide a battery cell, wherein the main difference between the battery cell and Example 1 is that the negative electrode sheet is different. Specifically, at least one of the following is different: the content of styrene-butadiene rubber, the content of polymeric monomer, and the mass ratio of styrene-butadiene rubber to polymeric monomer in the negative electrode sheet. See Table 1 for details.

[0222] Table 1

[0223] Example 13

[0224] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0225] The compound shown in Formula III-1 was added to deionized water at a molar ratio of 1:1.05 with lithium hydroxide to obtain a polymeric monomer containing Formula II-1.

[0226] Example 14

[0227] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0228] The compound shown in Formula III-2 was added to deionized water at a molar ratio of 1:1.05 with lithium hydroxide to react and obtain a polymeric monomer containing Formula II-2.

[0229] Example 15

[0230] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0231] The compound shown in Formula III-4 was added to deionized water at a molar ratio of 1:2.1 with lithium hydroxide to obtain a polymeric monomer containing Formula II-4.

[0232] Example 16

[0233] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0234] The compound shown in Formula III-5 was added to deionized water at a molar ratio of 1:2.1 with lithium hydroxide to obtain a polymeric monomer containing Formula II-5.

[0235] Example 17

[0236] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0237] The compound shown in Formula III-6 was added to deionized water at a molar ratio of 1:2.1 with lithium hydroxide to obtain a polymeric monomer containing Formula II-6.

[0238] Example 18

[0239] This embodiment provides a battery cell, which differs from Embodiment 6 in that the structural formula of the polymer monomer is different, specifically:

[0240] The compound shown in Formula III-7 was added to deionized water at a molar ratio of 1:2.1 with lithium hydroxide to obtain a polymeric monomer containing Formula II-7.

[0241] Comparative Example 1

[0242] This comparative example provides a single battery cell. The difference from Example 1 is that no polymeric monomer is added to the negative electrode sheet; specifically:

[0243] Negative electrode plate:

[0244] Graphite active material, SBR (styrene-butadiene rubber) binder, carbon black conductive agent, and dispersant (sodium carboxymethyl cellulose) were mixed in a weight ratio of 98:1:0.5:0.5. The mixture was stirred until homogeneous, and then added to deionized water 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 a copper foil current collector 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 copper foil current collector 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 a negative electrode sheet.

[0245] Performance testing

[0246] (1) Infrared spectroscopy test

[0247] Before assembling the battery cells, the material on the surface of the negative electrode sheet was peeled off to serve as the sample for infrared spectroscopy testing. Specifically, the infrared test results of the negative electrode sheets prepared in Example 1 and Comparative Example 1 are shown in Figure 4.

[0248] As can be seen from Figure 4, in Example 1, the wavelength was 1500cm. -1 -1600cm -1 The peak exhibits a distinct stretching vibration peak, which is a characteristic peak of carbon-carbon double bonds, indicating that a polymeric monomer was added in Example 1.

[0249] (2) Cohesion

[0250] The pressure-sensitive tape is bonded to the stainless steel plate, and then the negative electrode sheet is bonded to the pressure-sensitive tape. A layer of green adhesive is then bonded to the pressure-sensitive tape. After clamping the green adhesive, a tensile testing machine is used to peel it off at 180°.

[0251] (3) Loop test

[0252] The battery cells were placed in a 60°C hot box and subjected to 1C / 1C accelerated cycling at a test voltage of 2.5V-3.65V for 100% DOD (Depth of Discharge) cycling.

[0253] (4) Variation in electrode thickness

[0254] The change in thickness of the negative electrode sheet after cold pressing and after 600 cycles is used to evaluate its expansion force. The thickness of the copper foil is recorded as h0, the thickness of the negative electrode sheet after cold pressing is recorded as h1, and the thickness of the negative electrode sheet after 600 cycles is recorded as h2. The change in electrode sheet thickness is calculated with reference to formula (1).

[0255] The performance parameters of the battery cells provided in Examples 1-18 and Comparative Example 1 are shown in Table 2.

[0256] Table 2

[0257] Table 2, in conjunction with Example 1 and Comparative Example 1, clearly shows that the combination of polymer and styrene-butadiene rubber can significantly improve the cohesive force of the negative electrode sheet and reduce its thickness variation, thereby improving the cycle performance of the battery cell.

[0258] Table 2 shows that, in conjunction with Examples 1 and 3, and Examples 2 and 7, when the total proportion of styrene-butadiene rubber and polymer is the same, optimizing the mass ratio of styrene-butadiene rubber to polymer can reduce the thickness variation of the negative electrode sheet, thereby improving the cycle performance of the battery.

[0259] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized 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, and the polymeric structural unit is shown in Formula I: Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - The R1, R2, and R3 groups are any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of them is -(CH2). n COO - n is a natural number ≤ 10; M includes any one of Li, Na, and K; The quantity of M, ax, is related to the -(CH2) content in the polymer. n COO - The ratio of their quantities is (0.9-1.1):1; x is a positive integer ≤ 1000.

2. The battery cell as described in claim 1, characterized in that, R1, R2, and R3 are each independently selected from -(CH2). n COO - It can be any one of alkyl groups and hydrogen atoms from C1 to C2, where n is a natural number ≤ 4.

3. The battery cell as described in claim 1 or 2, characterized in that, The quantity of M, ax, is related to the -(CH2) content in the polymer. n COO - The ratio of the quantities is (1.05-1.08):

1.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The polymeric structural unit includes at least one of the structural units shown in Formula I-1 to Formula I-7: In Equations I-1 to I-7, b is 0.9-1.

1.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The mass ratio of the negative electrode active material to the polymer is (93-97):(0.5-4).

6. The battery cell according to any one of claims 1 to 5, characterized in that, At least a portion of the polymer is connected to the negative electrode active material via at least one chemical bond, namely ionic bonds or hydrogen bonds.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The negative electrode film layer also includes styrene-butadiene rubber, wherein the number average molecular weight of the styrene-butadiene rubber is 20,000-80,000.

8. The battery cell as described in claim 7, characterized in that, The total mass of the styrene-butadiene rubber and the polymer in the negative electrode film layer is 1wt%-7wt% by mass. And / or, the mass ratio of the styrene-butadiene rubber to the polymer is 1:(0.3-2).

9. The battery cell according to any one of claims 1 to 8, characterized in that, The negative electrode active material includes at least one of carbon-based materials, silicon-based materials, and tin-based materials.

10. The battery cell as described in claim 9, characterized in that, The carbon material includes graphite, and the BET specific surface area of ​​the graphite is 0.8-5 m². 2 / g; and / or, The negative electrode active material includes a silicon-based material, and the BET specific surface area of ​​the silicon-based material is 5-100 m². 2 / g.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The negative electrode film layer also includes at least one of a dispersant and a conductive agent.

12. The battery cell as described in claim 11, characterized in that, Based on the total mass of the negative electrode film, the dispersant accounts for 0.3wt%-1.5wt% of the mass, and the conductive agent accounts for 0.3wt%-1.5wt% of the mass.

13. A method for preparing a single battery cell, characterized in that, Includes the following steps: An aqueous negative electrode slurry containing a polymeric monomer is prepared, and the aqueous negative electrode slurry is coated on at least one side of a negative electrode current collector to form a negative electrode film layer, thereby preparing a negative electrode sheet; wherein, the general chemical formula of the polymeric monomer is shown in Formula II: Among them, R1, R2, and R3 are each independently selected from -(CH2). n COO - The R1, R2, and R3 groups are any one of C1 to C5 alkyl groups and hydrogen atoms, and at least one of them is -(CH2). n COO - n is a natural number ≤ 10; M includes any one of Li, Na, and K; a is related to -(CH2) in the polymer monomer. n COO - The ratio of their quantities is (0.9-1.1):

1. Battery cells are prepared using the aforementioned negative electrode sheet.

14. The method for preparing a single battery cell as described in claim 13, characterized in that, The polymeric monomer comprises at least one of the compounds shown in Formula II-1 to Formula II-7: Wherein, in formulas II-1 to II-7: b is 0.9-1.

1.

15. The method for preparing a battery cell as described in claim 13 or 14, characterized in that, The concentration of the polymer monomer in the aqueous solution is 20 wt% and the pH value is 7-14.

16. The method for preparing a battery cell according to any one of claims 13 to 15, characterized in that, The pH value of the aqueous negative electrode slurry is 7-9.

17. The method for preparing a battery cell according to any one of claims 13 to 16, characterized in that, The preparation process of the polymer monomer is as follows: The polymeric monomer is obtained by reacting a compound of general chemical formula III with an alkali metal hydroxide in an aqueous solution. Among them, A1, A2, and A3 are each independently selected from -(CH2). n The atom is selected from COOH, an alkyl group (C1-C5), and a hydrogen atom, and at least one of A1, A2, and A3 has a -(CH2) group. n COOH, where n is a natural number ≤ 10.

18. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1-12 or the battery cell prepared by the preparation method described in any one of claims 13-17.

19. An electrical appliance, characterized in that, This includes the battery cell as described in any one of claims 1-12, the battery cell prepared by the preparation method described in any one of claims 13-17, or the battery device as described in claim 18.

Images