Battery cell, method for manufacturing the same, battery device, energy storage device, power consumption device

Abstract

This application relates to the field of energy storage, providing a battery cell and its preparation method, battery device, energy storage device, and power consumption device. The battery cell of this application includes a casing, within which an electrode assembly, a gel polymer backbone, and an electrolyte are disposed. The electrode assembly includes stacked electrodes and a separator, and an interface layer is disposed on the surface of the electrodes. A first polymer backbone is disposed in the interface layer, and the polymer monomer of the first polymer backbone includes an ionic liquid containing unsaturated bonds, including at least one of vinyl, methacryl, or acryloyl groups. The gel polymer backbone is located between the electrodes and the separator, and is grafted to the first polymer backbone. The battery cell of this application can simultaneously achieve high ionic conductivity and low interfacial impedance, ensuring that the battery cell has both good rate performance, good cycle performance, and good safety performance.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery cell and its preparation method, a battery device, an energy storage device, and an electrical device. Background Technology

[0002] Currently, rechargeable batteries can be broadly classified into liquid batteries, semi-solid batteries, and solid batteries based on the electrolyte content. Liquid and semi-solid batteries are widely used in everyday life. Liquid batteries have high ionic conductivity, but they are prone to dendrite formation that can puncture the separator, posing a significant safety hazard, especially during high-rate charge / discharge cycles. Semi-solid batteries can improve the safety performance of rechargeable batteries; however, the gel-like polymer backbone in semi-solid batteries tends to form a dense layer on the electrode surface, hindering the rapid insertion / extraction of lithium ions, leading to increased interfacial impedance and severe electrode polarization, with significant performance degradation, particularly during high-rate charge / discharge cycles. Summary of the Invention

[0003] This application provides a battery cell and its preparation method, battery device, energy storage device, and power consumption device. The battery cell of this application can simultaneously achieve high ionic conductivity and low interfacial impedance, ensuring that the battery cell has both good rate performance, good cycle performance, and good safety performance.

[0004] The first aspect of this application provides a battery cell, comprising: an electrode assembly including electrodes and a separator stacked together, wherein an interface layer is disposed on the surface of the electrodes, and a first polymer backbone is disposed in the interface layer, wherein the polymer monomer of the first polymer backbone includes an ionic liquid, the ionic liquid containing unsaturated bonds, the unsaturated bonds including at least one of vinyl, methacryl, or acryloyl groups; a housing, wherein the electrode assembly is located within the housing; a gel polymer backbone, wherein the gel polymer backbone is located between the electrodes and the separator, and wherein the gel polymer backbone is grafted onto the first polymer backbone; and an electrolyte, wherein the electrolyte is located within the housing.

[0005] In one possible implementation, the polymeric monomers of the first polymer backbone further include a first polymeric monomer with a polymerization reactivity ratio r1; the polymeric monomers of the gel polymer backbone include a second polymeric monomer with a polymerization reactivity ratio r2; 0.8 ≤ r1·r2 ≤ 1, and 0 <r1≤1,0<r2≤1。

[0006] In one possible implementation, the first polymerizing monomer includes acrylate groups, methacrylate groups, or vinyl groups; and / or, the second polymerizing monomer includes acrylate groups, methacrylate groups, or vinyl groups.

[0007] In one possible implementation, the first polymerizing monomer comprises an acrylate monomer; and / or, the second polymerizing monomer comprises an acrylate monomer; the acrylate monomer comprises at least one of polyurethane acrylate prepolymer, epoxy acrylate, polyester acrylate, polydimethylsiloxane-methacrylate, butyl acrylate, perfluoropolyether acrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, or trimethylolpropane triacrylate.

[0008] In one possible implementation, the anion in the ionic liquid includes either bis(fluorosulfonyl)imide or bis(trifluoromethanesulfonyl)imide.

[0009] In one possible implementation, the ionic liquid includes at least one of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, or [2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethanesulfonyl)imide.

[0010] In one possible implementation, the thickness of the interface layer is 5μm to 15μm.

[0011] Secondly, this application provides a method for preparing a battery cell, comprising: obtaining an electrode assembly, the electrode assembly including electrodes and a separator stacked together; obtaining an interface layer precursor liquid, the interface layer precursor liquid including an ionic liquid and an electrolyte, the ionic liquid containing unsaturated bonds, the unsaturated bonds including at least one of vinyl, methacryl, or acryloyl groups; placing the interface layer precursor liquid and the electrode assembly in a housing, and heating at T1°C to form a first polymer skeleton; injecting the bulk precursor liquid into the housing, and heating at T2°C to form a gel polymer skeleton, wherein the gel polymer skeleton is grafted onto the first polymer skeleton, and T1 < T2.

[0012] In one possible implementation, 25≤T1≤40, 50≤T2≤70.

[0013] In one possible implementation, the interfacial layer precursor liquid further includes a first initiator comprising 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile); and / or, the bulk precursor liquid includes a second initiator comprising azobisisobutyronitrile.

[0014] In one possible implementation, the mass content of the ionic liquid is 5% to 10% based on the mass of the interface layer precursor liquid.

[0015] In one possible implementation, based on the total mass of the interface layer precursor liquid and the bulk precursor liquid, the mass content of the interface layer precursor liquid is 10%~15%, and the mass content of the bulk precursor liquid is 85%~90%.

[0016] Thirdly, this application provides a battery device, including a battery cell of the first aspect, or a battery cell prepared by the method of preparing a battery cell as described in the second aspect. The battery device includes one or more of the following: battery module, battery pack, battery cluster, and battery cell.

[0017] Fourthly, this application provides an energy storage device, including the battery device of the third aspect, the battery device being used to store electrical energy.

[0018] Fifthly, this application provides an electrical device, including the battery device of the third aspect, the battery device being used to provide electrical energy.

[0019] The technical solution provided in this application has at least the following advantages: In the battery cell of this application, the interface layer contains an ionic liquid fixed on a first polymer backbone, thus ensuring good and stable ion transport performance of the interface layer. This also makes it less likely for a dense layer to form on the electrode surface of the battery cell, reducing the interfacial impedance. The gel polymer backbone prevents dendrites from piercing the separator and causing a short circuit, thereby improving the safety performance of the battery cell. Furthermore, the gel polymer backbone is grafted onto the first polymer backbone, reducing the risk of delamination between the two. This further ensures that dendrites are less likely to pierce the separator and also improves ion transport performance to some extent. Moreover, the electrolyte can penetrate into the gaps between the two polymer backbones, further enhancing the ion transport performance of the battery cell. Therefore, through the synergistic effect of the first polymer backbone, the gel polymer backbone, and the electrolyte, the battery cell of this application can ensure that it has good rate performance, good cycle performance, and good safety performance. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of a single battery cell in an embodiment of this application; Figure 2 This is an exploded view of a single battery cell in an embodiment of this application; Figure 3 This is a process flow diagram of the battery cell manufacturing process in the embodiments of this application; Figure 4 This is the attenuated total reflection Fourier transform infrared spectrum of Embodiment 1 of this application.

[0022] Reference numerals: 10-casing; 11-top cover; 12-outer shell; 20-electrode assembly; 100-cell battery. Detailed Implementation

[0023] As mentioned in the background, current liquid batteries are prone to dendrite formation, affecting battery safety performance, especially under high-rate charge-discharge conditions, where safety performance is further challenged. While semi-solid-state batteries offer improved safety, the gel-like polymer backbone results in low ionic conductivity, particularly at high rates, where performance degradation is more pronounced. This is because the adsorption and accumulation of polymer segments in semi-solid-state batteries create ion transport "dead zones," with interfacial impedance reaching 5-10 times that of the bulk phase. Current attempts have focused on surface pretreatment techniques and high-concentration electrolyte gelation techniques to improve the interfacial impedance of semi-solid-state batteries. For example, surface pretreatment techniques include pre-coating the electrode surface with conductive polymers (such as polyaniline) or using plasma bombardment to improve wettability. However, these methods either introduce additional electronic insulating layers or have short-lasting effects, failing to fundamentally solve the ion transport efficiency problem. High-concentration electrolyte gelation techniques enhance ion supply at the interface by increasing lithium salt concentration (>2 mol / L), but high salt concentrations significantly reduce ion transport numbers, increase viscosity, and are costly, limiting practical applications.

[0024] In addition, the inventors also discovered that the gels in existing battery cells either pursue high ionic conductivity (sacrificing mechanical properties) or high strength (sacrificing conductivity), making it difficult to meet the dual requirements of rapid interfacial transport and stable bulk support. Even if gradient structure materials (such as ceramic electrolytes) are set in the battery cells, the process is complex and costly because such materials require high-temperature sintering or multiple depositions, making them unsuitable for large-scale battery manufacturing.

[0025] Based on this, this application provides a battery cell and its preparation method, battery device, energy storage device, and power consumption device. The battery cell of this application contains both a gel polymer backbone and a first polymer backbone, which are grafted together by chemical bonds. The first polymer backbone is located on the electrode surface, and the polymer monomer of the first polymer backbone includes ionic liquid. This can improve ionic conductivity while ensuring safety performance, and ensure that the battery cell has both good rate performance, good cycle performance, and good safety performance.

[0026] 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. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

[0027] 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.

[0028] 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 three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0029] 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," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of other elements or features. Therefore, the term "below" may cover both above and below orientation depending on the context in which the term is used, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0030] 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.

[0031] In the description of embodiments of this application, the terms "about," "approximately," "roughly," or "about" for referring to a specific parameter include numerical values, and those skilled in the art will understand that the deviation from the numerical value is within the acceptable tolerance of the specific parameter. For example, "about" or "about" for a numerical value may include additional numerical values ​​that are in the range of 90.0% to 110.0% of the numerical value, such as in the range of 95.0% to 105.0%, 97.5% to 102.5%, 99.0% to 101.0%, 99.5% to 100.5%, or 99.9% to 100.1%.

[0032] In the accompanying drawings corresponding to the embodiments of this application, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0033] In the description of embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be an intermediate component between the two components. Conversely, when describing a component on the surface of another component, or a component "directly" on another component, or a component surface on which another component is formed or disposed, it indicates that there is no intermediate component between the two components. For simplicity and clarity, various components may be drawn at any scale. In the drawings, some components may be omitted for simplicity.

[0034] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0035] The “components” mentioned above can refer to layers, membranes, regions, parts, plates, or structures, etc.

[0036] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0037] In a first aspect, embodiments of this application provide a battery cell, including a housing, with an electrode assembly, a gel polymer backbone, and an electrolyte disposed inside the housing. The electrode assembly includes electrodes and a separator stacked together, and an interface layer is disposed on the surface of the electrodes. A first polymer backbone is disposed within the interface layer, and the polymer monomer of the first polymer backbone includes an ionic liquid containing unsaturated bonds, including at least one of vinyl, methacryl, or acryloyl groups. The gel polymer backbone is located between the electrodes and the separator, and is grafted to the first polymer backbone.

[0038] In the battery cell of this application, since the polymer monomers of the first polymer skeleton include ionic liquids, when the ionic liquids polymerize with other polymer monomers through unsaturated bonds to form the first polymer skeleton, the first polymer skeleton can be guaranteed to have good and durable stable ion transport performance. The interface layer containing the first polymer skeleton has good ion transport performance, and since the interface layer is located on the electrode surface, it is less likely to form a dense layer on the electrode surface, thereby better improving the rapid insertion / extraction rate of ions and better reducing the interface impedance. The gel polymer skeleton can ensure that dendrites are not likely to pierce the separator and cause a short circuit, thereby improving the safety performance of the battery cell; moreover, the gel polymer skeleton is also grafted with the first polymer skeleton, which can reduce the risk of peeling between the gel polymer skeleton and the first polymer skeleton. This not only further ensures that dendrites are not likely to pierce the separator, but also improves the ion transport performance to a certain extent. In addition, since both the first polymer skeleton and the gel polymer skeleton are skeleton structures, the electrolyte can penetrate well into the gaps in the skeleton (at this time, the interface layer contains not only the first polymer skeleton but also the electrolyte), thereby further improving the ion transport performance of the battery cell.

[0039] Therefore, through the synergistic effect of the first polymer backbone, the gel polymer backbone and the electrolyte, the battery cell of the present application can ensure that the battery cell has good rate performance, as well as good cycle performance and safety performance.

[0040] It should be noted that the electrode of the present application can be either a positive electrode or a negative electrode, therefore, the surface of the positive electrode may comprise an interface layer, and the surface of the negative electrode may also comprise an interface layer. The specific structure of the positive electrode and the negative electrode will be specifically described later in the present application. Moreover, the "stacked arrangement" in the present application can be in a stacked form or a wound form, which is not particularly limited in the present application, as long as it can meet the purpose of the present application.

[0041] In some embodiments of the present application, in addition to ionic liquids, the polymerized monomers of the first polymer backbone further include a first polymerizable monomer; the first polymerizable monomer can polymerize with the ionic liquid to form the first polymer backbone, and can also form chemical bonds with the second polymerizable monomer of the gel polymer backbone, ensuring that the gel polymer backbone can be grafted with the first polymer backbone. Therefore, in order to ensure that the first polymerizable monomer can react with the second polymerizable monomer to form a chemical bond, in some embodiments of the present application, the reactivity ratio of the first polymerizable monomer is r1, and the reactivity ratio of the second polymerizable monomer is r2, 0.8≤r1·r2≤1, and 0<r1≤1, 0<r2≤1. It should be noted that r1·r2=1 corresponds to ideal random copolymerization. At this time, the probability of addition reaction between the growing radical of the second polymerizable monomer and the second polymerizable monomer, and between the growing radical and the residual double bond at the end of the first polymer backbone is comparable. Therefore, the second polymerizable monomer can fully undergo homopolymerization to form a bulk gel polymer backbone with sufficient crosslinking density, and can also be grafted with the first polymer backbone across layers; if r1·r2>1, the tendency of homopolymerization of the two polymerizable monomers respectively increases, the probability of cross-layer grafting decreases, and physical contact is easily degenerated between the two layers; if r1·r2<0.8, the tendency of alternating copolymerization is too strong, the second polymerizable monomer is preferentially consumed for cross addition with residual double bonds, the crosslinking density of the bulk gel polymer backbone is insufficient, and it is difficult to inhibit dendrites from piercing the separator. Therefore, 0.8≤r1·r2≤1 is a suitable window that takes into account bulk network formation and cross-layer grafting. In addition, in order to ensure that the first polymerizable monomer can well polymerize with the ionic liquid to form the first polymer backbone, the polymerizable group of the first polymerizable monomer comprises any one of acrylate group, methacrylate group or vinyl group; in this case, the polymerizable group in the second polymerizable monomer also comprises any one of acrylate group, methacrylate group or vinyl group.

[0042] Specifically, in some embodiments of this application, the first polymerizing monomer and / or the second polymerizing monomer includes acrylate monomers, which include at least one of polyurethane acrylate prepolymer, epoxy acrylate, polyester acrylate, polydimethylsiloxane-methacrylate, butyl acrylate, perfluoropolyether acrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, or trimethylolpropane triacrylate.

[0043] Furthermore, this application does not have specific requirements regarding the type of ionic liquid, as long as its molecule contains unsaturated bonds such as vinyl, methacryl, or acryloyl groups that can participate in free radical polymerization and can copolymerize with the first polymeric monomer to form the first polymer backbone. It should be noted that the carbon-carbon double bond on the imidazole ring is an aromatic conjugated double bond and cannot participate in free radical polymerization. Therefore, conventional ionic liquids such as 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, which do not contain the aforementioned unsaturated bonds, can only exist in free form in the electrolyte and cannot be grafted onto the first polymer backbone, and are not considered ionic liquids in this application. In some embodiments of this application, the anions in the ionic liquid include, but are not limited to, either bis(trifluoromethanesulfonyl)imide or bis(trifluoromethanesulfonyl)imide. These two anions have highly delocalized charges and react with Li... + The low binding energy is beneficial to Li + The dissociation and transport of [the substance], and the LiF in its reduction decomposition products can participate in the construction of a stable SEI film. Specifically, the ionic liquid includes 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide salt (molecular formula C […]). 11 H 15 F6N3O4S2, CAS No. 758716-72-2, can be abbreviated as "VBImTFSI"), 1-vinyl-3-butylimidazolium bis(fluorosulfonyl)imide salt (can be abbreviated as "VBImFSI"), 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt or [2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethanesulfonyl)imide salt (molecular formula C 11 H 18 At least one of F6N2O6S2 (which can be abbreviated as "METMA-TFSI").

[0044] In some embodiments of this application, the thickness of the interface layer is generally 5μm to 15μm, for example, it can be 5μm, 7μm, 8μm, 10μm, 12μm, 15μm, etc., or within a range consisting of any two of the above values. If the interface layer thickness is too small, it is difficult to completely cover the rough morphology of the electrode surface (the D50 of graphite anode particles is typically 8μm to 15μm), the interface layer coverage is discontinuous, and the uncovered areas will still directly contact the bulk gel polymer backbone and form a dense layer, resulting in insignificant improvement in interface impedance; moreover, when the interface layer is too thin, the total amount of residual active double bonds at its ends is insufficient, leading to inadequate grafting density with the gel polymer backbone. If the interface layer thickness is too large, Li... + As the transport path through the interface layer lengthens, the transport impedance of the interface layer itself increases. Simultaneously, the cross-linking density of the interface layer is lower than that of the bulk layer; an excessively thick interface layer weakens the overall mechanical support of the electrode assembly and occupies limited space within the casing, reducing the volumetric energy density of the individual cells. Therefore, a thickness of 5μm to 15μm for the interface layer achieves a balance between completely covering the electrode surface, ensuring grafting density, and controlling the transport path length.

[0045] This application does not impose any special requirements on the electrode assembly and electrolyte, as long as they meet the purpose of this application. As an example, this application provides a detailed description of the electrode assembly and electrolyte.

[0046] As described above in this application, the electrodes in the electrode assembly include a positive electrode and a negative electrode, and the surfaces of both the positive and / or negative electrodes may be provided with an interface layer containing a first polymer backbone. The separator is stacked with the electrodes, that is, the separator is located between adjacent electrodes to prevent short circuits.

[0047] In the electrode assembly, the positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector. Specifically, in this application, the positive active layer can be disposed on one surface or on two surfaces along the thickness direction of the positive current collector. Furthermore, in this application, the "surface of the positive current collector" can be the entire area of ​​the positive current collector or only a portion thereof; there are no particular limitations, as long as the purpose of this application is achieved.

[0048] The positive electrode active layer comprises a positive electrode active material, which can be any material capable of reversibly inserting and de-intercalating Li. + Na +Substances containing alkali metal ions are used to ensure the normal charging and discharging of secondary batteries. For example, the positive electrode active material includes lithium salts, which can be lithium-containing phosphates. Lithium-containing phosphates refer to phosphate materials containing lithium elements and can be detected by any method known in the art. For example, detection can be performed using a combination of X-ray diffraction and energy dispersive spectroscopy, or inductively coupled plasma mass spectrometry. As examples, lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate doped and modified materials, lithium iron phosphate coated and modified materials, lithium manganese phosphate, or lithium manganese iron phosphate. Lithium manganese iron phosphate, as an emerging high-voltage phosphate material, combines safety and high-voltage characteristics.

[0049] For example, the positive electrode active material can also be a high-voltage system with a working voltage greater than or equal to 4.3V, such as high-nickel ternary materials, high-voltage spinel materials, or lithium-rich manganese-based materials.

[0050] For example, high-nickel ternary materials such as LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA) and other compounds possess operating voltages of 4.3V~4.6V and high specific capacity, making them ideal cathode choices for high-voltage lithium metal batteries. High-voltage spinel LiNi... 0.5 Mn 1.5 O4 can operate at a voltage of up to 4.7V, matching its high voltage stability.

[0051] However, this application is not limited to the materials listed above, and other materials that can be used as positive electrode active materials in battery cells may also be used. These positive electrode active materials may be used alone, or two or more may be used in combination.

[0052] In some embodiments, the positive electrode active layer further includes a positive electrode conductive agent; this application does not limit the type of positive electrode conductive agent, and any known conductive material can be used. Specifically, the positive electrode conductive agent includes, but is not limited to, at least one of the following: acetylene black, Super-P carbon black, amorphous carbon such as needle coke, carbon nanotubes, or graphene.

[0053] In some embodiments, the positive electrode active layer generally also contains a positive electrode binder. There are no particular restrictions on the type of positive electrode binder used in the manufacture of the positive electrode active layer. In the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used in the electrode manufacturing process is acceptable. Positive electrode binders include, but are not limited to, any one or at least two of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene-styrene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ion conductivity of alkali metal ions (especially lithium ions).

[0054] In the positive electrode, there are no particular restrictions on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. The positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil may include, but is not limited to, aluminum foil. The composite current collector may include a base layer and a metal layer located on at least one surface of the base layer. For example, the base layer can be a polymer material base layer, including but not limited to polypropylene (PP) base layer, polyethylene terephthalate (PET) base layer, polybutylene terephthalate (PBT) base layer, polystyrene (PS) base layer, or polyethylene (PE) base layer. The material of the metal layer may include, but is not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. Furthermore, to reduce the electronic contact resistance between the positive electrode current collector and the positive electrode active layer, a conductive additive or conductive coating may be provided on the surface of the positive electrode current collector. Conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver. The conductive coating may be a mixture of inorganic oxides, conductive agents, and positive electrode binders.

[0055] In preparing the positive electrode, it can be either formulated into a positive electrode slurry, coated onto a positive electrode current collector, and dried to form a positive electrode active layer on the current collector, thus obtaining the positive electrode; or the components in the positive electrode active layer can be dry-mixed, formed into a sheet, and then pressed onto the positive electrode current collector to form the positive electrode active layer, thus obtaining the positive electrode. When using this method to prepare the positive electrode, there are no particular restrictions on the solvent in the positive electrode slurry, as long as it can dissolve or disperse the aforementioned components. Specifically, the solvent in the positive electrode slurry includes, but is not limited to, N-methylpyrrolidone (NMP) and ethylene carbonate (EC).

[0056] In the electrode assembly, the negative electrode includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector, wherein the composition of the negative electrode active layer includes a negative electrode active material. That is, in this application, the negative electrode active layer can be disposed on one surface or on two surfaces in the thickness direction of the negative electrode current collector. Furthermore, in this application, the "surface of the negative electrode current collector" can be the entire area of ​​the negative electrode current collector or a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved.

[0057] The negative electrode active layer generally contains a negative electrode active material, and this application does not impose any particular limitation on the negative electrode active material. Specifically, the negative electrode active material can be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material can be at least one of the following materials, including but not limited to: graphite, carbon materials, silicon-based materials, tin-based materials, or lithium titanate. Graphite can be artificial graphite or natural graphite. Carbon materials can be soft carbon or hard carbon. Silicon-based materials can be selected from at least one of elemental silicon, silicon-oxygen composites, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other materials that can be used as negative electrode active materials for battery cells can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0058] In some embodiments, the negative electrode active layer typically also contains a negative electrode conductive agent. This application does not particularly limit the type of negative electrode conductive agent, as long as it achieves the purpose of this application. For example, negative electrode conductive agents include, but are not limited to, at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon black, or graphene.

[0059] In some embodiments, the negative electrode active layer may also contain a negative electrode binder and a thickener. This application does not particularly limit the types of negative electrode binders and thickeners, as long as they can achieve the purpose of this application. For example, the negative electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, or acrylated styrene-butadiene rubber; the thickener in the negative electrode slurry may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0060] In the negative electrode, the negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil may include, but is not limited to, copper foil, and this application is not particularly limited. The composite current collector may include a base layer and a metal layer located on at least one surface of the base layer. For example, the base layer may be a polymer material base layer, including but not limited to polypropylene (PP) base layer, polyethylene terephthalate (PET) base layer, polybutylene terephthalate (PBT) base layer, polystyrene (PS) base layer, or polyethylene (PE) base layer. The material of the metal layer may include, but is not limited to, at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy.

[0061] Furthermore, in this application, there are no particular limitations on the thickness of the negative electrode current collector and the negative electrode active layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4μm to 12μm, and the thickness of the single-sided negative electrode active layer is 30μm to 160μm.

[0062] In preparing the negative electrode, the components of the aforementioned negative electrode active layer can be dissolved or dispersed in a liquid solvent to form a negative electrode slurry. This slurry is then coated onto a negative electrode current collector and dried to form the negative electrode active layer, thus obtaining the negative electrode. Alternatively, the components of the negative electrode active layer can be dry-mixed to form a sheet, which is then pressed onto the negative electrode current collector to form the negative electrode active layer, thereby obtaining the negative electrode. The solvent in the negative electrode slurry includes any one of aqueous or organic solvents. Aqueous solvents include, but are not limited to, mixtures of alcohol and water or water itself. Organic solvents include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. In some other embodiments, when using aqueous solvents, the negative electrode slurry composition may also include a thickener and styrene-butadiene rubber (SBR) emulsion to slurry the negative electrode slurry, thereby adjusting its viscosity. The types of thickeners in the positive electrode slurry include, but are not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts.

[0063] This application does not impose any particular limitations on the material and shape of the diaphragm in the electrode assembly, as long as it does not significantly impair the effectiveness of this application. The diaphragm material can be resin, glass fiber, inorganic materials, etc., formed from materials stable to the electrolyte of this application. In some embodiments, the diaphragm includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of resin or glass fiber diaphragm materials include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene (PE) or polypropylene (PP). In some embodiments, the polyolefin is polypropylene. The above-mentioned diaphragm materials can be used alone or in any combination.

[0064] Inorganic materials include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The forms of inorganic materials include, but are not limited to, particulate or fibrous forms.

[0065] The separator can be a single-layer film or a multi-layer composite film, without particular restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions. The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, three-layer separators formed by laminating polypropylene, polyethylene, and polypropylene in that order, ceramic-coated separators, high-strength polymer separators, or functionalized composite separators. PP and PE separators typically have a thickness of 12μm to 25μm and a porosity of 30% to 50%, exhibiting good mechanical strength and chemical stability. Ceramic-coated separators are made by coating polyolefin-based membranes with ceramic materials such as Al2O3, SiO2, and TiO2 (coating thickness 2μm to 5μm), improving high-temperature resistance (thermal shut-off temperature >160℃) and puncture resistance. High-strength polymer separators (such as polyimide PI, polyethylene terephthalate PET, and aramid nanofiber separators) have excellent mechanical properties and high-temperature resistance. Functionalized composite membranes (such as membranes with solid electrolyte coatings or lithiophilic coatings) can further improve the stability of lithium deposition.

[0066] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is 1 μm to 50 μm, specifically 5 μm to 40 μm, and more specifically 8 μm to 30 μm; for example, 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, 15 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., or within a range consisting of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the secondary battery can be ensured.

[0067] Electrolytes are used to transport ions, enabling individual battery cells to function properly. This application does not have specific requirements for the electrolyte, as long as it meets the objectives of this application. Typically, electrolyte components include lithium salts, organic solvents, additives, etc. As an example, a detailed description follows.

[0068] In some embodiments of this application, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide [LiN(SO2F)2], lithium bis(trifluoromethanesulfonyl)imide [LiN(SO2CF3)2], lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiODFP), and lithium tetrafluorooxalate phosphate (LiOTFP). This application does not impose any particular limitation on the content of the electrolyte salt in the electrolyte, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage content of the lithium salt is 8% to 15%.

[0069] This application does not impose any particular limitation on organic solvents, as long as they achieve the purpose of this application. For example, organic solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate, fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the solvent content in the electrolyte, as long as the purpose of this application is achieved.

[0070] In some embodiments of this application, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high temperature or low temperature performance of the battery cell, etc.

[0071] The battery cells in this application can be various packaging forms such as button cells, pouch cells, and hard-case cells. The operating voltage range of the battery cells can be set according to the positive and negative electrode systems used, and this application does not impose any particular limitation on this. For example, for the lithium iron phosphate / graphite system, the operating voltage range can be 2.50V~3.65V; for other positive and negative electrode systems, the operating voltage range can be adjusted accordingly based on the material platform. The operating temperature range can be -20℃~60℃.

[0072] This application does not impose any particular limitation on the overall shape of the battery cell, as long as it meets the purpose of this application. For example, it can be a square battery, a cylindrical battery, a pouch battery, etc. As an example, this application provides a structural schematic diagram of the battery cell, the overall structural schematic diagram of which is shown below. Figure 1 As shown, the exploded view is as follows Figure 2 As shown.

[0073] Specifically, the battery cell 100 includes a housing 10, an electrode assembly 20, and an electrolyte (not shown in the figure). The electrode assembly 20 is housed within the housing 10. The housing 10 provides a receiving space for the electrode assembly 20, and the housing 10 can adopt various structures. In some embodiments, the housing 10 may include a top cover 11 and a shell 12, with the top cover 11 and the shell 12 covering each other, and the top cover 11 and the shell 12 together defining a receiving space for accommodating the electrode assembly 20. The shell 12 may be a hollow structure with one end open, and the top cover 11 may be a plate-like structure, with the top cover 11 covering the open side of the shell 12, so that the top cover 11 and the shell 12 together define the receiving space, such as... Figure 2 As shown. The top cover 11 and the outer shell 12 can both be hollow structures with an opening on one side, with the opening side of the top cover 11 fitting over the opening side of the outer shell 12. Of course, the shell 10 formed by the top cover 11 and the outer shell 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0074] The battery cells provided in this application can be widely used in battery fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. The battery cells provided in this application can achieve large-capacity energy storage, comprehensively improving energy density, cycle life, and safety performance. They can meet the needs of long-term energy storage, achieving 4 hours or more of long-term energy storage, for example, in energy storage scenarios of 5 hours, 6 hours, and 8 hours. Long-term energy storage refers to the ability to continuously discharge at rated power for 4 hours or even longer, or to achieve large-scale, low-cost energy storage for several days or months.

[0075] Accordingly, another embodiment of this application also provides a method for preparing a battery cell, which can be used to manufacture the battery cell provided in the above embodiments, and its preparation process flow diagram is shown below. Figure 3As shown in the accompanying drawings, the manufacturing method of a battery cell according to another embodiment of this application will be described in detail below. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding description of the foregoing embodiment, which will not be described in detail below.

[0076] The method for preparing the battery cell of this application includes the following steps: S100. Obtain an electrode assembly, which includes electrodes and a diaphragm stacked together.

[0077] As described above in this application, the electrodes and the diaphragm can be arranged either in a wound manner or in a stacked manner. This application does not have any special requirements in this regard, as long as the purpose of this application can be met.

[0078] S200. Obtain an interface layer precursor solution, which includes an ionic liquid and an electrolyte. The ionic liquid contains unsaturated bonds, including at least one of vinyl, methacryl, or acryloyl groups.

[0079] In this step, the interface layer precursor solution can subsequently solidify to form an interface layer, specifically through the polymerization reaction of ionic liquids and other polymeric monomers to form a first polymer backbone. Additionally, corresponding to the foregoing description in this application, the interface layer precursor solution may also contain a first polymeric monomer. As an example, in some embodiments of this application, the first polymeric monomer in the interface layer precursor solution includes polyurethane acrylate prepolymer (PUA) and polyethylene glycol diacrylate (PEGDA), wherein PUA can adjust the elasticity and mechanical properties of the interface layer, and PEGDA can provide a flexible spacer and act as a reactive diluent and compatibilizer.

[0080] In this step, the amount of ionic liquid must be neither too much nor too little. If the amount is too low, the number of ion transport sites fixed on the first polymer backbone will be insufficient, resulting in a negligible improvement in the ion transport performance of the interface layer. If the amount is too high, the following adverse effects will occur: First, ionic liquids are mostly monofunctional polymeric monomers, existing primarily as side-attached structures in the first polymer backbone. Excessive dosage will dilute the crosslinking points of the first polymeric monomers, reducing the crosslinking density of the first polymer backbone and the absolute number of residual active double bonds at the ends, which is detrimental to subsequent grafting with the gel polymer backbone. Second, ionic liquids have high viscosity; excessive dosage will significantly increase the viscosity of the interface layer precursor solution, reducing its wetting rate and depth into the electrode pores. Third, imidazole cations have a negative electrode voltage of approximately 1.0V~1.5V (vs. Li / Li). + This means that reductive decomposition will occur and participate in the construction of the SEI film; excessive ionic liquid will consume more active lithium, leading to a decrease in initial coulombic efficiency and long-term cycling capacity retention; fourth, the larger organic cations will react with Li +Competition for migration channels actually reduces the lithium-ion migration number. As an example, in some embodiments of this application, the mass content of the ionic liquid is 5% to 10% based on the mass of the interface layer precursor liquid, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, or within a range of any two of the above values.

[0081] In addition, the monomers in the subsequent interface layer precursor solution will polymerize, so the interface layer precursor solution usually also contains a first initiator.

[0082] S300: Place the interface layer precursor liquid and electrode assembly in the housing and heat at T1℃ to form the first polymer skeleton.

[0083] In this step, the monomers in the interface layer precursor solution polymerize with each other after heating to form a first polymer backbone. It should be noted that the interface layer in this application is prepared using in-situ polymerization. That is, the electrode assembly is first installed in the housing, then the interface layer precursor solution is injected into the housing and wets the electrode assembly. Finally, it is heated inside the housing to polymerize in situ on the electrode surface, rather than pre-forming the first polymer backbone on the electrode before installing it into the housing. Using in-situ polymerization allows the interface layer to conformally fit the rough morphology and pores of the electrode surface, avoiding the introduction of pores and contact resistance at the interface by the pre-coating process. Furthermore, after the interface layer completes polymerization inside the housing, it can be directly injected into the bulk precursor solution for a second polymerization, allowing the residual active double bonds at its ends to participate in the subsequent grafting reaction in a state of non-air contact and non-deactivation. Moreover, considering that the first polymer backbone needs to be grafted onto the gel polymer backbone later, the ends of the first polymer backbone formed in this step will still retain unreacted polymeric groups, accounting for 15% to 30% of the total polymeric groups. Therefore, in some embodiments of this application, the temperature is typically set to 25 ≤ T1 ≤ 40, and the heating time is 4h to 8h. This ensures that the monomers in the interface layer precursor solution gel but do not react completely. Furthermore, considering the low reaction temperature in this step, the first initiator in the interface layer precursor solution is a low-temperature initiator, such as 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile) (referred to as "V-70", with a 10h half-life temperature of approximately 30°C). It should be noted that V-70 can decompose at a suitable rate to generate free radicals at 25°C to 40°C. If an initiator with a higher 10h half-life temperature is used (e.g., azobisisobutyronitrile with a 10h half-life temperature of approximately 65°C, and di-tert-butyl peroxide with a 10h half-life temperature of approximately 126°C), it will hardly decompose at T1°C and will not be able to initiate polymerization in the interface layer precursor solution.

[0084] It should be noted that, due to the abundance of catalytically active sites (including metal ions) on the electrode surface, the polymer monomers preferentially aggregate on the electrode surface, thereby forming an interface layer containing the first polymer backbone. Therefore, the interface layer can adhere relatively tightly to the electrode surface.

[0085] In addition, adjusting the amount of the interface layer precursor liquid can also adjust the thickness of the formed interface layer. The specific adjustment can be made according to actual needs, which will not be elaborated in this application.

[0086] After the first polymer backbone is formed, some electrolyte fills the gaps in the first polymer backbone. If the electrode assembly is removed for observation at this time, a semi-solid gel layer will be found on the surface of the electrode, and the electrode assembly contains liquid; the semi-solid gel is the first polymer backbone (i.e., the interface layer) filled with electrolyte in the gaps, and the liquid in the electrode assembly is the remaining electrolyte. Therefore, the interface layer of this application is actually also in a gel state. However, it should be noted that the first polymer backbone in the gel-state interface layer is not the same as the gel polymer backbone. Therefore, in order to distinguish between the two, the gel-state layer structure on the electrode surface is called the "interface layer".

[0087] S400. Inject the bulk precursor liquid into the shell and heat it at T2℃ to form a gel polymer skeleton. The gel polymer skeleton is grafted with the first polymer skeleton, and T1 < T2.

[0088] In this step, the bulk precursor solution, upon heating, generates a gel polymer backbone, which can be grafted onto the first polymer backbone. To ensure complete reaction of all monomers within the shell, T2 needs to be greater than T1; typically, 50 ≤ T2 ≤ 70, and the heating time is 6-12 hours. At T2, the second initiator fully decomposes, and the second monomers in the bulk precursor solution both homopolymerize to form the gel polymer backbone and undergo cross-addition with the residual active double bonds in the interfacial layer, thereby forming a continuous C-C main chain covalent bond network between the two layers.

[0089] In addition, in this step, the bulk precursor solution includes a second polymerization monomer, an electrolyte, and a second initiator. The electrolyte functions to dissolve or uniformly disperse the second polymerization monomer, and the second polymerization monomer is used to form a gel polymer skeleton. The present application does not require that the second polymerization monomer must be completely identical to the first polymerization monomer, as long as the two are compatible to form covalent bonding; specifically, to ensure compatibility between the first polymerization monomer and the second polymerization monomer, generally, the reactivity ratio of the first polymerization monomer is r1, and the reactivity ratio of the second polymerization monomer is r2, 0.8 ≤ r1·r2 ≤ 1, and 0 < r1 ≤ 1, 0 < r2 ≤ 1. In this way, when the polymerization reaction occurs at T2°C, the second polymerization monomers can not only homopolymerize among themselves, but also can graft with unreacted groups in the first polymer skeleton. For example, in some embodiments of the present application, the second polymerization monomer includes PUA, PEGDA and polydimethylsiloxane-methacrylate (PDMS-MA), wherein PDMS-MA can increase the flexibility of the gel polymer skeleton. The components and contents of each component of the electrolyte in the bulk precursor solution may be the same as or different from those in the interface layer precursor solution. Generally, to simplify the preparation process, the components and contents of each component of the electrolyte in the bulk precursor solution are the same as those in the interface layer precursor solution. In addition, considering that the polymerization temperature T2°C in this step is relatively high, the second initiator may include azobisisobutyronitrile (AIBN) and the like.

[0090] It should be noted that in the chemical material system, substances such as PUA, PDMS-MA and PEGDA are called "macromonomers" or "prepolymers". They are not final polymers that completely lose reactivity, but have unreacted carbon-carbon double bonds at the end or side chain of their polymer chains; at a suitable temperature and in the presence of free radicals, the unreacted carbon-carbon double bonds can still break and undergo free radical polymerization. Therefore, they participate in the reaction in the form of monomers with long-chain structures, and finally crosslink to form a three-dimensional gel network. Moreover, due to different molecular weights, the CAS numbers of PEGDA, PUA and PDMS-MA will also be different. In the case that the present application does not limit the molecular weights of PEGDA, PUA and PDMS-MA, it is also impossible to give a uniquely corresponding CAS number. Therefore, PEGDA, PUA and PDMS-MA in the present application are defined by chemical names in combination with the number average molecular weight Mn, and those skilled in the art can select commercially available products of corresponding grades according to the required crosslinking density and flexibility, as long as the purpose of the present application can be achieved.

[0091] Furthermore, the amount of bulk precursor liquid used should be greater than that of the interface layer precursor liquid, and the amount of the second polymerizing monomer should be greater than the sum of the amounts of the first polymerizing monomer and the ionic liquid. This ensures that the gel polymer skeleton formed in the bulk precursor liquid can effectively improve the safety performance of the battery cell and also guarantees that the gel polymer skeleton can form normally and graft onto the first polymer skeleton. As an example, in some embodiments of this application, based on the total mass of the interface layer precursor liquid and the bulk precursor liquid, the mass content of the interface layer precursor liquid is 10%~15%, and the mass content of the bulk precursor liquid is 85%~90%.

[0092] Electrolyte is also filled into the gaps in the gel polymer backbone. This electrolyte-filled gel polymer backbone can be referred to as the "bulk layer." It should be noted that in the embodiments of this application, based on the total mass of the electrolyte, the first polymer backbone, and the gel polymer backbone, the total mass ratio of the two polymer backbones is typically only 8% to 10%. Furthermore, since both polymer backbones have high swelling capacity, they do not completely bind the electrolyte within the network: the electrolyte bound by the network swelling still maintains near-liquid ion transport capabilities, while the electrolyte exceeding the gel's saturation swelling capacity exists in a free state, continuing to wet the pores of the electrode assembly, thereby ensuring the continuity of ion transport channels within the battery cell. Whether chemical bonding occurs between the two polymer backbones can be verified using ATR-FTIR (Attenuated Total Reflection Fourier Transform Infrared Spectroscopy). ATR-FTIR is used to analyze the interface region at 1725 cm⁻¹. -1 The absorption peak at the carbonyl C=O group of the ester at the interface is used as an internal standard. If the absorption peak at the interface is 1635 cm⁻¹, then... -1 The relative intensity of the acrylate C=C absorption peak at the interface is lower than that within any monolayer, indicating a higher double bond conversion rate at the interface and the occurrence of interlayer chemical bond grafting. Here, "relative intensity" refers to the intensity at 1635 cm⁻¹ in each layer structure (or interface layer). -1 Peak intensity at 1725 cm⁻¹ -1 The ratio of peak intensity at each location, expressed as "A". 1635 / A 1725 "Note; for example, this application provides the ATR-FTIR spectrum of the corresponding region in Embodiment 1, such as..." Figure 4 As shown. It should be noted that, Figure 4 The vertical axis has been normalized; therefore, the peak height of different spectral lines at the same horizontal axis does not necessarily represent the intensity of different spectral lines at that horizontal axis. A relative intensity (i.e., A) is required. 1635 / A 1725This can be used to determine whether the carbonyl C=O group in the region has been efficiently converted into acrylate C=C. Figure 4 There are three spectral lines in total: the absorbance lines of the interface layer, the bulk layer, and the interface / bulk layer boundary region after normalization. Each spectrum is labeled with A. 1635 / A 1725 The specific ratios are 0.38, 0.42, and 0.19, respectively. (From...) Figure 4 It can be seen that the interface layer / bulk layer boundary region in Example 1 is at 1635 cm. -1 The acrylate C=C absorption peak at the interface has the lowest relative intensity, which verifies that the double bond conversion rate is higher at the interface, indicating that cross-layer chemical bonding grafting has occurred. Of course, in some other embodiments of this application, it can also be verified by tensile testing. If the sample does not first undergo delamination and fracture at the interface during the tensile test, it can be proven that chemical bonding grafting has occurred.

[0093] After grafting the gel polymer backbone to the first polymer backbone, the battery cells are usually subjected to a formation treatment to ensure that the battery cells can be used normally. This application does not have special requirements for the formation treatment method, as long as it can meet the purpose of this application.

[0094] This application also provides a battery device, which includes the aforementioned battery cell, or a battery cell prepared by the aforementioned method. The battery device of this application can take the form of one or more of the following: battery module, battery pack, and energy storage battery.

[0095] In a battery device, a single battery cell can be used alone or in multiples. These cells can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple cells are connected in both series and parallel configurations. Multiple cells can be directly connected in series, parallel, or a combination thereof to form a whole, which is then housed within a casing. Alternatively, a battery device can consist of multiple cells first connected in series, parallel, or a combination thereof to form battery modules, which are then connected in series, parallel, or a combination thereof to form a whole, which is then housed within a casing.

[0096] The battery device may also include other structures, such as a busbar for electrical connection between multiple battery cells.

[0097] This application also provides an energy storage device, including the aforementioned battery device, wherein the battery device is used to store electrical energy. The energy storage device of this application includes, but is not limited to, residential energy storage cabinets, commercial energy storage cabinets, energy storage containers, energy storage racks, energy storage power stations, energy storage battery packs, or portable energy storage systems. The energy storage device may also include an energy management system (EMS), a battery management system (BMS), and a power conversion system (PCS).

[0098] This application also provides an electrical device, including the aforementioned battery device, wherein the battery device is used to provide electrical energy. The electrical devices of this application include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0099] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0100] Example 1 <Preparation of Electrolyte> In a dry argon-protected glove box, EC, EMC, and DMC were mixed in a volume ratio of 1:1:1 as the base solvent, and then LiPF6 was added and stirred to prepare the electrolyte. The LiPF6 content in the electrolyte was 1 mol / L.

[0101] <Preparation of interfacial layer precursor solution> The polymerizable ionic liquid VBImTFSI, the first polymerizable monomers PUA and PEGDA (M n =400 (also known as PEGDA-400), the first initiator V-70 is mixed with the electrolyte to form the interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of VBImTFSI is 8%, the content of PUA is 0.8%, the content of PEGDA-400 is 4%, the content of V-70 is 0.1%, and the remainder is electrolyte.

[0102] <Preparation of phase precursor solution> The second polymerization monomers PUA, PDMS-MA and PEGDA (M n=700, also known as PEGDA-700), the second initiator AIBN is mixed with the electrolyte to form a bulk precursor solution. Based on the total mass of the bulk precursor solution, the content of PUA is 2%, the content of PDMS-MA is 2%, the content of PEGDA-700 is 4.5%, the content of AIBN is 0.2%, and the remainder is electrolyte.

[0103] <Preparation of battery cells> A 4Ah soft-pack electrode assembly was formed by winding a stacked positive electrode, separator, and negative electrode. The positive electrode was a lithium iron phosphate system, and the negative electrode was a graphite system. The electrode assembly was first placed in a housing, and then an interface layer precursor solution (1.3 g / Ah) was injected into the housing. The assembly was allowed to stand for 30 minutes to allow the precursor solution to fully penetrate the electrode pores and spread on the electrode surface. The assembly was then heated and held at T1=40℃ for 6 hours to form the first polymer backbone. Next, a bulk precursor solution (9.5 g / Ah) was injected into the housing, allowed to stand for 1 hour, and then heated and held at T2=60℃ for 8 hours to form a gel polymer backbone grafted onto the first polymer backbone. Taking the total mass of the interface layer precursor solution and the bulk precursor solution as 100%, the mass percentage of the interface layer precursor solution was 12%, and the mass percentage of the bulk precursor solution was 88%. Afterwards, a low-current formation process (0.1C, 3 cycles), venting, and sealing were performed according to standard procedures, followed by aging at 45℃ for 48 hours.

[0104] Example 2 Compared to Example 1, the main difference lies in the different contents of each component in the interface layer precursor solution, as detailed below: <Preparation of interfacial layer precursor solution> A polymerizable ionic liquid, VBImTFSI, first polymerizable monomers PUA and PEGDA-400, and first initiator V-70 are mixed with an electrolyte to form an interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of VBImTFSI is 5%, the content of PUA is 1%, the content of PEGDA-400 is 5%, the content of V-70 is 0.1%, and the remainder is electrolyte.

[0105] Example 3 Compared to Example 1, the main difference lies in the different contents of each component in the interface layer precursor solution, as detailed below: <Preparation of interfacial layer precursor solution> A polymerizable ionic liquid, VBImTFSI, first polymerizable monomers PUA and PEGDA-400, and first initiator V-70 are mixed with an electrolyte to form an interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of VBImTFSI is 10%, the content of PUA is 0.5%, the content of PEGDA-400 is 3%, the content of V-70 is 0.1%, and the remainder is electrolyte.

[0106] Example 4 Compared to Example 1, the main difference lies in adjusting the mass content of the interface layer precursor liquid and the bulk precursor liquid. Specifically, in the preparation process of the battery cell, with the total mass of the interface layer precursor liquid and the bulk precursor liquid being 100%, the mass ratio of the interface layer precursor liquid is 10%, and the mass ratio of the bulk precursor liquid is 90%.

[0107] Example 5 Compared to Example 1, the main difference lies in adjusting the mass content of the interface layer precursor liquid and the bulk precursor liquid. Specifically, in the preparation process of the battery cell, with the total mass of the interface layer precursor liquid and the bulk precursor liquid being 100%, the mass ratio of the interface layer precursor liquid is 15%, and the mass ratio of the bulk precursor liquid is 85%.

[0108] Example 6 Compared to Example 1, the main difference lies in the different contents of each component in the bulk precursor solution, as detailed below: <Preparation of phase precursor solution> The second polymerization monomers PUA, PDMS-MA, and PEGDA-700, the second initiator AIBN, and the electrolyte were mixed to form a bulk precursor solution. Based on the total mass of the bulk precursor solution, the content of PUA was 3%, the content of PDMS-MA was 3%, the content of PEGDA-700 was 3%, the content of AIBN was 0.2%, and the remainder was electrolyte.

[0109] Example 7 Compared to Example 1, the main difference lies in the different contents of each component in the bulk precursor solution, as detailed below: <Preparation of phase precursor solution> The second polymerization monomers PUA, PDMS-MA, and PEGDA-700, the second initiator AIBN, and the electrolyte were mixed to form a bulk precursor solution. Based on the total mass of the bulk precursor solution, the content of PUA was 1%, the content of PDMS-MA was 1%, the content of PEGDA-700 was 6%, the content of AIBN was 0.2%, and the remainder was electrolyte.

[0110] Example 8 Compared to Example 1, the main difference lies in the different contents of each component in the interface layer precursor solution, as detailed below: <Preparation of interfacial layer precursor solution> A polymerizable ionic liquid, VBImTFSI, first polymerizable monomers PUA and PEGDA-400, and first initiator V-70 were mixed with an electrolyte to form an interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of VBImTFSI was 4%, the content of PUA was 1%, the content of PEGDA-400 was 5%, the content of V-70 was 0.1%, and the remainder was electrolyte.

[0111] Example 9 Compared to Example 1, the main difference lies in the different contents of each component in the interface layer precursor solution, as detailed below: <Preparation of interfacial layer precursor solution> A polymerizable ionic liquid, VBImTFSI, first polymerizable monomers PUA and PEGDA-400, and first initiator V-70 were mixed with an electrolyte to form an interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of VBImTFSI was 11%, the content of PUA was 0.5%, the content of PEGDA-400 was 3%, the content of V-70 was 0.1%, and the remainder was electrolyte.

[0112] Comparative Example 1 <Preparation of Electrolyte> In a dry argon-protected glove box, EC, EMC, and DMC were mixed in a volume ratio of 1:1:1 as the base solvent, and then LiPF6 was added and stirred to prepare the electrolyte. The LiPF6 content in the electrolyte was 1 mol / L.

[0113] <Preparation of battery cells> A 4Ah soft-pack electrode assembly is formed by winding a stacked positive electrode, a separator, and a negative electrode. The positive electrode is a lithium iron phosphate system, and the negative electrode is a graphite system. The electrode assembly and electrolyte are placed in a housing, allowing the electrolyte to enter the electrode assembly. Formation treatment is then performed.

[0114] That is, the battery cell in this comparative example does not contain a gel polymer backbone and an interface layer compared to the battery cell in Example 1, but the composition of the electrolyte is the same as that in Example 1.

[0115] Comparative Example 2 <Preparation of Electrolyte> In a dry argon-protected glove box, EC, EMC, and DMC were mixed in a volume ratio of 1:1:1 as the base solvent, and then LiPF6 was added and stirred to prepare the electrolyte. The LiPF6 content in the electrolyte was 1 mol / L.

[0116] <Preparation of phase precursor solution> The second polymerization monomers PUA, PDMS-MA, and PEGDA-700, the second initiator AIBN, and the electrolyte were mixed to form a bulk precursor solution. Based on the total mass of the bulk precursor solution, the content of PUA was 2%, the content of PDMS-MA was 2%, the content of PEGDA-700 was 4.5%, the content of AIBN was 0.2%, and the remainder was electrolyte.

[0117] <Preparation of battery cells> An electrode assembly was obtained, comprising a positive electrode, a separator, and a negative electrode stacked sequentially. The positive electrode is a lithium iron phosphate system, and the negative electrode is a graphite system. The electrode assembly was first placed in a housing, and then a bulk precursor solution was injected into the housing. Heating was performed at T2=60℃ to form a gel polymer framework. A formation process was then carried out.

[0118] That is, the polymer skeletons in the battery cells of this comparative example are the same, and none of them contain ionic liquids.

[0119] Comparative Example 3 <Preparation of Electrolyte> In a dry argon-protected glove box, EC, EMC, and DMC were mixed in a volume ratio of 1:1:1 as the base solvent, and then LiPF6 was added and stirred to prepare the electrolyte. The LiPF6 content in the electrolyte was 1 mol / L.

[0120] <Preparation of Precursor Solution> A precursor solution was formed by mixing polymerizable ionic liquid VBImTFSI, first monomers PUA, PDMS-MA, and PEGDA-700, second initiator AIBN, and electrolyte. Based on the total mass of the precursor solution, the content of VBImTFSI was 4%, PUA was 2%, PDMS-MA was 2%, PEGDA-700 was 4%, AIBN was 0.2%, and the remainder was electrolyte.

[0121] <Preparation of battery cells> An electrode assembly was obtained, comprising a positive electrode, a separator, and a negative electrode stacked sequentially. The positive electrode is a lithium iron phosphate system, and the negative electrode is a graphite system. The electrode assembly was first placed in a housing, and then a precursor solution was injected into the housing. Heating was then performed at T2=60℃ to form a gel polymer framework. A formation process was then carried out.

[0122] That is, the polymer skeletons in the battery cells of this comparative example are the same, and they all contain ionic liquids.

[0123] Comparative Example 4 Compared to Example 1, the main difference is that the interface layer precursor solution does not contain ionic liquid, as detailed below: <Preparation of interfacial layer precursor solution> The first polymerization monomers PUA and PEGDA-400, the first initiator V-70, and the electrolyte were mixed to form the interface layer precursor solution. Based on the total mass of the interface layer precursor solution, the content of PUA was 2%, the content of PEGDA-400 was 6%, the content of V-70 was 0.1%, and the remainder was electrolyte.

[0124] That is, the battery cell in this comparative example does not contain ionic liquid in the interface layer compared to the battery cell in Example 1.

[0125] Comparative Example 5 Compared to Example 1, the main difference is that the heating temperature is the same in both stages of battery cell preparation, as detailed below: <Preparation of battery cells> An electrode assembly was obtained, comprising a positive electrode, a separator, and a negative electrode stacked sequentially. The positive electrode is a lithium iron phosphate system, and the negative electrode is a graphite system. First, the electrode assembly was placed in a housing. Then, an interface layer precursor solution was injected into the housing, and heating was performed at T2=60℃ to form a first polymer framework. Next, a bulk precursor solution was injected into the housing, and heating and holding at T2=60℃ for 8 hours formed a gel polymer framework grafted onto the first polymer framework. Taking the total mass of the interface layer precursor solution and the bulk precursor solution as 100%, the mass percentage of the interface layer precursor solution was 12%, and the mass percentage of the bulk precursor solution was 88%. Subsequently, a formation process was performed.

[0126] In other words, compared to the battery cell of Example 1, the first polymer backbone in the interface layer of the battery cell in this comparative example is not grafted with the gel polymer backbone.

[0127] The battery cells in the above embodiments and comparative examples were subjected to performance tests. The test methods are as follows, and the test results are shown in Table 1.

[0128] Electrochemical Impedance Spectroscopy (EIS) Testing A 4Ah battery cell was charged to 50% SOC (State of Charge) at 25°C, allowed to stand for 2 hours, and then subjected to AC impedance testing using an electrochemical workstation. Frequency range: 100kHz~0.01Hz, amplitude: 10mV.

[0129] The interface impedance (Rf+Rct) is determined by the semicircle diameter in the high-frequency region of the Nyquist plot.

[0130] Ratio Performance Test The battery cells were discharged sequentially at 25°C at rates of 0.5C, 1C, 2C, 3C, and 5C to 2.5V, with each rate cycled 5 times. The average discharge capacity was recorded. Rate capacity retention rate = (5C discharge capacity / 0.5C discharge capacity) × 100%.

[0131] Cyclic performance test At 25°C, constant current charge-discharge cycles were performed at 1C / 1C, with cutoff voltages of 3.65V / 2.5V, for 500 cycles. Capacity retention and average coulombic efficiency were recorded.

[0132] Gradient structure representation After the battery cell was cycled, the negative electrode was cleaned with NMP, and the morphology and elemental distribution of the gel layer on the electrode surface were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). (F element represents TFSI in ionic liquids.) - (N element represents the imidazole ring).

[0133] Security performance test After charging the battery cell to 100% SOC at 0.33C and letting it stand for 4 hours, the high-temperature resistant steel needle with a diameter of 3mm was used to penetrate the battery cell at a speed of 25mm / s in a direction perpendicular to the electrode sheet, in accordance with the needle penetration method in GB / T 31485, and held for 1 hour. The highest temperature on the surface of the battery cell and whether fire or explosion occurred were recorded. Three samples were tested in each group. The test was considered passed if none of the samples caught fire or exploded.

[0134] The test results are shown in Table 1. Table 1

[0135] In addition, the inventors also tested the ionic conductivity of the polymer skeletons in Examples 1 to 3 and Comparative Examples 2 to 3. The test methods are as follows, and the results are shown in Table 2.

[0136] Layered conductivity test The two layer structures in this test are not connected; they are prepared separately and tested independently to characterize the intrinsic ionic conductivity of each layer. Specifically, following the formulations of the interface layer precursor solution in each embodiment and comparative example, the first polymer backbone was prepared by heating at T1=40℃ for 6 hours and then at 60℃ for 8 hours on a stainless steel substrate to achieve complete curing. Similarly, the gel polymer backbone was prepared by heating at T2=60℃ for 8 hours on a stainless steel substrate according to the formulations of the bulk phase precursor solution in each embodiment and comparative example. The thickness of both backbones was controlled to be 500 μm, and they were sandwiched between two stainless steel blocking electrodes. Their ionic conductivity was measured at 25℃ using AC impedance spectroscopy (frequency range 1MHz~1Hz, amplitude 10mV). The conductivity gradient ratio = interface layer conductivity / bulk layer conductivity.

[0137] Table 2

[0138] To facilitate understanding, the differences between the comparative examples and the embodiments are explained first: The battery cell of Comparative Example 1 does not contain any polymer backbone, but only liquid electrolyte, which is equivalent to a conventional liquid battery; the battery cell of Comparative Example 2 uses a homogeneous gel obtained by one-step polymerization and does not use ionic liquid as a polymer monomer; the battery cell of Comparative Example 3 also uses a homogeneous gel obtained by one-step polymerization, but the ionic liquid is uniformly distributed throughout the gel; the battery cell of Comparative Example 4 has a bilayer structure of an interface layer and a bulk layer, but the precursor solution of the interface layer does not contain ionic liquid; the battery cell of Comparative Example 5 also has a bilayer structure containing ionic liquid, but the polymerization temperature is the same for both polymerizations (60°C). The interface layer is completely solidified during the first polymerization and no longer has active double bonds at the ends. Therefore, there is no chemical bond grafting between the first polymer backbone in the interface layer and the gel polymer backbone in the bulk layer, and the two layers are only in physical contact.

[0139] Interfacial impedance and rate performance analysis: In the interfacial layers of the battery cells in Examples 1 to 9, the interfacial impedance is significantly lower than that in Comparative Examples 2 to 5 because ionic liquid was used in the first polymer backbone. Specifically, the interfacial impedance of the battery cells in Examples 1 to 9 is in the range of 10Ω to 18Ω, which is about 37% to 64% lower than that in Comparative Example 2 (28.7Ω), and close to the level of Comparative Example 1 (8.3Ω) with liquid electrolyte. This indicates that the interfacial ion transport performance of the battery cells in this application is good. In Comparative Examples 2 and 4, there is no ionic liquid as a polymer monomer in the interfacial region. The segments of the gel polymer backbone adsorb and accumulate on the electrode surface to form a dense layer, which constitutes a "dead zone" for ion transport, and therefore the interfacial impedance is significantly higher. In Comparative Example 3, both the interface layer and the bulk layer contain ionic liquids, but the interfacial impedance is still as high as 22.1 Ω. This is because: firstly, the ionic liquid is uniformly diluted throughout the bulk phase, resulting in a lower density of ion transport sites near the electrode surface compared to the embodiments of this application, making it impossible to construct high-conductivity fast channels on the electrode surface; secondly, during one-step polymerization, the gel still preferentially nucleates on the electrode surface and forms a dense layer, and the transport "dead zone" at the interface still exists; furthermore, the large number of imidazole cations distributed in the bulk phase react with Li... + Competition for migration pathways and increased bulk viscosity lead to a decrease in the bulk lithium-ion transference number. In Comparative Example 5, there is no chemical bonding between the interface layer and the bulk layer; Li... +The physical contact interface between the two layers requires additional desolvation and resolvation processes, resulting in significant resistance and an interfacial impedance as high as 19.5Ω. Furthermore, the 5C rate capacity retention of the embodiment is significantly higher than that of Comparative Examples 2 to 5, indicating that the combination of the interfacial layer and the bulk layer can effectively alleviate interfacial polarization under high current. The battery cell of Comparative Example 1 contains only liquid electrolyte, without the adsorption and accumulation of polymer segments, thus exhibiting superior interfacial impedance and 5C rate capacity retention. However, the battery cell of Comparative Example 1 lacks the mechanical barrier of a gel polymer skeleton, making it highly susceptible to dendrite formation; its 500-cycle capacity retention is only 78.2%, and all three samples ignited during the nail penetration test. While the battery cell of this application has slightly lower interfacial impedance and 5C rate capacity retention than Comparative Example 1, the difference is not significant and can be considered to be at the same level. Moreover, its cycle capacity retention and safety performance are far superior to Comparative Example 1. Therefore, it can be concluded that the battery cell of this application, compared to Comparative Example 1, possesses both good rate performance and good cycle performance and safety performance.

[0140] Cyclic stability analysis: Although the initial coulombic efficiency of the individual cells in the examples decreased slightly, the capacity retention after 500 cycles remained above 88% (all examples 1-7 were above 90%), indicating that the combination of the interface layer and the bulk layer did not sacrifice long-term stability. The initial coulombic efficiency decrease in the examples was due to TFSI in the ionic liquid. - This is due to participation in the formation of the SEI (Solid Electrolyte Interphase) film, while TFSI - The reduced LiF is beneficial for forming a dense and stable SEI film, thus resulting in better long-cycle performance. Furthermore, a comparison of Examples 1-3 with Examples 8 and 9 shows that when the mass content of the ionic liquid in the interface layer precursor solution is 5%-10% (Examples 1-3), the interfacial impedance, rate performance, and cycle performance of the battery cell are all superior. When the content is 4% (Example 8), there are insufficient fixed ion transport sites in the interface layer, the interface impedance rises to 17.6Ω, and the 5C rate capacity retention drops to 84.2%. When the content is 11% (Example 9), although the interface impedance remains at the same level as Examples 1-7 (13.9Ω), the crosslinking density of the first polymer backbone and the number of residual active double bonds decrease, and excessive imidazole cations participate in SEI film formation and react with Li... + Competition migration reduced the average coulombic efficiency to 99.80% and the capacity retention after 500 cycles to 88.4%, resulting in a significant decline in cycling performance. Therefore, based on the quality of the interface layer precursor solution, the mass content of the ionic liquid should ideally be 5%–10%.

[0141] Analysis of the necessity of grafting: Although Comparative Example 5 has a bilayer structure, it lacks chemical bonding (both layers are completely cured separately, with only physical contact at the interface), resulting in microscopic cracks at the interface and delamination during cycling (capacity retention of only 85.7% after 500 cycles, the lowest among all examples and comparative examples). This demonstrates the crucial importance of chemical bonding grafting. In the embodiments of this application, the design strategy of intentionally retaining 15%~30% of unreacted active double bonds at the ends of the first polymer backbone by controlling T1 < T2 is key to achieving chemical bonding between the two layers: initiation at a lower T1 temperature ensures that the interface layer preferentially forms a semi-solid gel on the electrode surface without complete curing, reserving active sites for subsequent copolymerization; when polymerization is initiated again at a higher T2 temperature to form a gel polymer backbone in the bulk phase layer, the active groups at the interface copolymerize with the second polymer monomer, forming a C-C main chain covalent bond network across layers. There is no physical interface between the two layers; instead, they share continuous polymer segments, fundamentally eliminating the risk of interlayer separation. Table 2 also shows that the interfacial layer conductivity of Examples 1-3 is 14.2 mS / cm~21.5 mS / cm, significantly higher than that of their bulk layer (8.9 mS / cm~9.1 mS / cm), with a conductivity gradient ratio of 1.58~2.42. In contrast, the gels of Comparative Examples 2 and 3 are homogeneous structures with a conductivity gradient ratio of 1.00, indicating no conductivity gradient. This gradient structure of "high interfacial conductivity and high bulk strength" is precisely why the battery cell of this application can simultaneously achieve low interfacial impedance and high safety performance: the interfacial layer is responsible for the rapid conduction of Li. + The polarization of the negative electrode surface is reduced at high rates to suppress lithium plating, while the bulk layer provides mechanical strength to prevent dendrites from piercing the separator.

[0142] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A battery cell, characterized in that, include: An electrode assembly includes electrodes and a diaphragm stacked together, and an interface layer is provided on the surface of the electrodes. A first polymer backbone is provided in the interface layer. The polymer monomer of the first polymer backbone includes an ionic liquid. The ionic liquid contains unsaturated bonds, and the unsaturated bonds include at least one of vinyl, methacryl, or acryloyl groups. Housing, wherein the electrode assembly is located within the housing; A gel polymer framework is located between the electrode and the diaphragm, and the gel polymer framework is grafted to the first polymer framework; Electrolyte, which is located inside the housing.

2. The battery cell according to claim 1, characterized in that, The first polymer backbone further includes a first polymeric monomer, the polymerization reactivity ratio of which is r1; the gel polymer backbone includes a second polymeric monomer, the polymerization reactivity ratio of which is r2; 0.8 ≤ r1·r2 ≤ 1, and 0 <r1≤1,0<r2≤1。 3. The battery cell according to claim 2, characterized in that, The first polymeric monomer includes acrylate groups, methacrylate groups, or vinyl groups; and / or, The second polymeric monomer includes acrylate groups, methacrylate groups, or vinyl groups.

4. The battery cell according to claim 2 or 3, characterized in that, The first polymerization monomer includes an acrylate monomer; and / or, the second polymerization monomer includes an acrylate monomer; The acrylate monomers include at least one of polyurethane acrylate prepolymers, epoxy acrylates, polyester acrylates, polydimethylsiloxane-methacrylate, butyl acrylate, perfluoropolyether acrylates, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, or trimethylolpropane triacrylate.

5. The battery cell according to claim 1, characterized in that, The anion in the ionic liquid includes either bis(fluorosulfonyl)imide or bis(trifluoromethanesulfonyl)imide.

6. The battery cell according to claim 1 or 5, characterized in that, The ionic liquid comprises at least one of 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, or [2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethanesulfonyl)imide.

7. The battery cell according to claim 1, characterized in that, The thickness of the interface layer is 5μm~15μm.

8. A method for preparing a single battery cell, characterized in that, include: Obtain an electrode assembly, the electrode assembly comprising electrodes and a diaphragm stacked together; An interface layer precursor solution is obtained, the interface layer precursor solution comprising an ionic liquid and an electrolyte, wherein the ionic liquid contains unsaturated bonds, and the unsaturated bonds include at least one of vinyl, methacryl, or acryloyl groups; The interface layer precursor liquid and the electrode assembly are placed in the housing and heated at T1℃ to form a first polymer skeleton; The bulk precursor liquid is injected into the shell and heated at T2°C to form a gel polymer skeleton, and the gel polymer skeleton is grafted to the first polymer skeleton, where T1 < T2.

9. The method for preparing a battery cell according to claim 8, characterized in that, 25≤T1≤40, 50≤T2≤70.

10. The method for preparing a battery cell according to claim 8 or 9, characterized in that, The interface layer precursor solution further includes a first initiator, the first initiator comprising 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile); and / or, The bulk precursor liquid includes a second initiator, which includes azobisisobutyronitrile.

11. The method for preparing a battery cell according to claim 8 or 9, characterized in that, Based on the mass of the interface layer precursor solution, the mass content of the ionic liquid is 5% to 10%.

12. The method for preparing a battery cell according to claim 8 or 9, characterized in that, Based on the total mass of the interface layer precursor liquid and the bulk precursor liquid, the mass content of the interface layer precursor liquid is 10%~15%, and the mass content of the bulk precursor liquid is 85%~90%.

13. A battery device, characterized in that, The battery device includes one or more of the following: battery cell as described in any one of claims 1 to 7, or battery cell prepared by the method described in any one of claims 8 to 12.

14. An energy storage device, characterized in that, Includes the battery device as described in claim 13, wherein the battery device is used to store electrical energy.

15. An electrical appliance, characterized in that, Includes the battery device as described in claim 13, the battery device being used to provide electrical energy.

Images