Battery jelly-roll, electrochemical device, and electronic device

Abstract

The application discloses a battery roll core, an electrochemical device and an electronic device, and belongs to the field of electrochemical energy storage. The battery roll core comprises a flat area and a corner area. The battery roll core comprises a diaphragm. The diaphragm comprises a base film and a coating layer on at least one surface of the base film. The coating layer comprises a deformable polymer. The softening temperature of the deformable polymer is 40 DEG C to 160 DEG C. After the battery roll core is hot-pressed under the condition that the temperature is 85 DEG C and the pressure is 1-2 MPa, the thickness compression rate of the flat area is a, 30%≤a≤80%, the thickness compression rate of the corner area is b, 10%≤b≤25%, and the thickness difference of the diaphragm between the flat area and the corner area is 1 um to 10 um. The diaphragm thickness of the flat area of the battery roll core is thinner, the flat area is more closely attached to the pole piece, the internal resistance is reduced, the interface ion conduction efficiency is improved, the diaphragm thickness of the corner area is thicker, the electrolyte is beneficial to be stored, and lithium precipitation is reduced.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to battery cores, electrochemical devices, and electronic devices. Background Technology

[0002] When separators are used in battery cells, the interface gaps in the corner areas are small. During battery charge-discharge cycles, these corner areas are easily compressed due to the expansion of the negative electrode material, preventing electrolyte wetting and leading to lithium plating. Therefore, a separator is needed that can improve lithium plating in the corner areas of battery cells and enhance their safety performance. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this application provides a battery core, an electrochemical device, and an electronic device, aiming to solve the problems of improving lithium deposition in the corner areas of the battery core and enhancing the safety performance of the battery core.

[0004] To achieve the above objectives, this application proposes a battery core comprising a straight region and a corner region. The battery core includes a separator, which comprises a base film and a coating on at least one surface of the base film. The coating comprises a deformable polymer with a softening temperature of 40°C to 160°C. Furthermore, after the battery core is hot-pressed at a temperature of 85°C and a pressure of 1 to 2 MPa, the thickness compression rate of the straight region is a, where 30% ≤ a ≤ 80%, and the thickness compression rate of the corner region is b, where 10% ≤ b ≤ 25%. The thickness difference between the separator in the straight region and the corner region is 1 μm to 10 μm.

[0005] In some embodiments, the volume average particle size Dv10 of the deformable polymer is 2.0 μm to 5 μm, the volume average particle size Dv50 of the deformable polymer is 3 μm to 15 μm, and the volume average particle size Dv90 of the deformable polymer is 3.8 μm to 31.5 μm.

[0006] In some embodiments, the particle size distribution width of the deformable polymer is 0.5 ≤ (Dv90-Dv10) / Dv50 ≤ 2.0.

[0007] In some embodiments, the deformable polymer has a Poisson's ratio of 0.35 to 0.45.

[0008] In some embodiments, the deformable polymer includes at least one selected from polyolefin, polymethyl methacrylate, polystyrene, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide.

[0009] In some embodiments, the coating includes an adhesive, wherein the mass ratio of the deformable polymer to the adhesive is c, and 0.2 ≤ c ≤ 1.0.

[0010] In some embodiments, the adhesive includes at least one of resin-based polymers, rubber-based polymers, and thermoplastic elastomer-based polymers.

[0011] In some embodiments, the adhesive comprises a water-soluble adhesive, and the coating comprises an additive, the additive comprising at least one of polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium citrate, sodium ethylenediaminetetraacetate, sodium diacetate, sodium hexametaphosphate, sodium silicate, and carboxymethyl cellulose.

[0012] To achieve the above objectives, this application also proposes an electrochemical device, including an electrode, an electrolyte, and the aforementioned battery core.

[0013] To achieve the above objectives, this application also proposes an electronic device including the aforementioned electrochemical device.

[0014] The beneficial effects of this application are as follows: This application provides a battery core in which a deformable polymer is incorporated into the separator coating. By setting a coating containing the deformable polymer on the separator surface and controlling its softening temperature to 40℃~160℃, the polymer can undergo adaptive deformation during hot pressing, thereby achieving differentiated control of the thickness of the flat and corner regions. After hot pressing, the thickness compression rate of the flat region is controlled at 30%~80%, and the thickness compression rate of the corner region is controlled at 10%~25%, with the thickness difference between the two maintained at 1μm~10μm. This ensures that the flat region has a high energy density while maintaining sufficient separator thickness in the corner region, effectively buffering the compressive stress generated by the expansion of the negative electrode material, maintaining the interfacial gap in the corner region, which is conducive to storing more electrolyte, reducing the risk of thermal runaway caused by internal short circuits due to lithium plating, improving battery safety performance, and avoiding irreversible loss of active lithium, which helps to extend the battery's cycle life. Attached Figure Description

[0015] The embodiments described in this application are not limited to the accompanying drawings, which are only some of the embodiments described herein. Those skilled in the art can obtain drawings of other embodiments based on the content of this application.

[0016] Figure 1 This is a schematic diagram of the structure of a battery core according to an embodiment of this application, where 1 is a straight area and 2 is a corner area; The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0017] General terminology: The term "deformable polymer" refers to a polymeric material whose structure or physicochemical properties undergo significant deformation when subjected to external pressure and temperature.

[0018] The term "water-soluble adhesive" refers to a polymer adhesive that is soluble in water or uniformly dispersed in water.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions.

[0020] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0021] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, these terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.

[0022] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0023] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0024] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0025] Throughout this specification, references to "implementation," "partial implementation," "one implementation," "another implementation," "specific method," or "partial method" mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0026] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0027] Separators are used in battery cells. At the corners of the battery, the interface gaps are small, and during charge-discharge cycles, the electrolyte cannot effectively penetrate these corners due to compression, leading to lithium plating. Therefore, it is necessary to develop a separator to improve lithium plating at corners and enhance the safety performance of the battery cell.

[0028] In view of this, refer to Figure 1 This application provides a battery core, which includes a straight region 1 and a corner region 2. The battery core includes a separator, which includes a base film and a coating on at least one surface of the base film. The coating includes a deformable polymer, and the softening temperature of the deformable polymer is 40°C to 160°C. After the battery core is hot-pressed at a temperature of 85°C and a pressure of 1 to 2 MPa, the thickness compression rate of the straight region is a, where 30% ≤ a ≤ 80%, and the thickness compression rate of the corner region is b, where 10% ≤ b ≤ 25%. The thickness difference between the separator in the straight region and the corner region is 1 μm to 10 μm.

[0029] This application incorporates deformable polymers into the diaphragm coating and limits the volume average particle size of the deformable polymers in the diaphragm coating. In this way, the stress difference between the flat area and the corner area of ​​the diaphragm during hot pressing is designed, and the performance of the diaphragm is controlled by the different degrees of elastic deformation of the diaphragm in different areas.

[0030] The softening temperature of the deformable polymer is 40℃~160℃. Within this range, the softening temperature of the deformable polymer facilitates achieving the desired membrane deformation after hot pressing.

[0031] By controlling the thickness compression ratio of the flat region 1 between 30% and 80%, the contact between the electrode and the separator within the flat region 1 is closer, the interfacial impedance is reduced, and this is beneficial for the rapid transport of lithium ions. Controlling the thickness compression ratio of the corner region 2 between 10% and 25% forms an effective elastic buffer layer, preventing separator collapse or pore closure due to rigid compression. Therefore, the corner region 2 maintains a stable electrolyte wetting channel even during long-term cycling. Controlling the separator thickness difference between the flat region 1 and the corner region 2 within the range of 1 μm to 10 μm helps to create a balanced electric and stress field throughout the core, preventing localized overcharging or damage to the core's mechanical properties.

[0032] For example, the thickness compression rate 'a' of the flat region 1 can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or within the range of any two of the above values.

[0033] For example, the thickness compression rate b of the corner region 2 can be 10%, 13%, 16%, 19%, 22%, 25%, or within the range of any two of the above values.

[0034] Therefore, this application ensures that the flat region has a high energy density and that the corner region retains sufficient membrane thickness, which can effectively buffer the compressive stress generated by the expansion of the negative electrode material, maintain the interface gap in the corner region, facilitate the storage of more electrolyte, reduce the risk of thermal runaway caused by internal short circuit due to lithium plating, improve the safety performance of the battery, and avoid irreversible loss of active lithium, which helps to extend the cycle life of the battery.

[0035] According to some embodiments of this application, the volume average particle size Dv10 of the deformable polymer is 2.0 μm to 5 μm, the volume average particle size Dv50 of the deformable polymer is 3 μm to 15 μm, and the volume average particle size Dv90 of the deformable polymer is 3.8 μm to 31.5 μm.

[0036] According to some embodiments of this application, the deformable polymer is a primary particle or a secondary particle. A primary particle refers to an individual, fine crystal or particle with an original particle size; these are particles that have not agglomerated and are typically considered the basic unit in measurement and analysis. A secondary particle refers to particles formed from primary particles through agglomeration or aggregation; agglomeration can be physical, such as van der Waals forces, or chemical, such as hydrogen bonds.

[0037] According to some embodiments of this application, the deformable polymer can be any shape, such as spheres, sheets, irregular blocks, etc.

[0038] For example, the softening temperature of the deformable polymer can be 40℃, 43℃, 46℃, 49℃, 52℃, 55℃, 58℃, 61℃, 64℃, 67℃, 70℃, 73℃, 76℃, 79℃, 82℃, 85℃, 88℃, 91℃, 94℃, 97℃, 100℃, 103℃, 106℃, 109℃, 112℃, 115℃, 118℃, 121℃, 124℃, 127℃, 130℃, 133℃, 136℃, 139℃, 142℃, 145℃, 148℃, 151℃, 154℃, 157℃, 160℃, or within any two of the above values.

[0039] The small-diameter particles represented by Dv10, the medium-diameter particles represented by Dv50, and the large-diameter particles represented by Dv90 do not act independently. In the flat region 1, due to the large external mechanical pressure, a large number of small-sized particles fill the skeleton and work together with the medium-sized particles to form a dense bottom layer and a uniform surface pore structure, which ensures excellent adhesion between the diaphragm and the electrode and significantly reduces the interfacial contact resistance. In the corner region 2, the mechanical stress distribution is complex. The medium and large-sized particles in the system act as a supporting skeleton and create pores and channels after thermal melting and shrinkage, which can store a sufficient amount of electrolyte.

[0040] This structure, with its specific particle size distribution, matches the ion transport requirements of different regions of the battery cell. This is directly manifested in the thinner membrane in the flat region 1, which is subjected to greater mechanical pressure, resulting in a tighter fit with the electrode, effectively reducing internal resistance and improving interfacial ion conduction efficiency. In contrast, in the corner region 2, where mechanical stress is complex and poor interfacial contact is prone to occur, the membrane stores a richer amount of electrolyte.

[0041] For example, the volume average particle size Dv10 of the deformable polymer can be 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm, or fall within the range of any two of the above values.

[0042] For example, the volume average particle size Dv50 of the deformable polymer can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or within any two of the above values.

[0043] For example, the volume average particle size Dv90 of the deformable polymer can be 3.8 μm, 4.8 μm, 5.8 μm, 6.8 μm, 7.8 μm, 8.8 μm, 9.8 μm, 10.8 μm, 11.8 μm, 12.8 μm, 13.8 μm, 14.8 μm, 15.8 μm, 16.8 μm, 17.8 μm, 18.8 μm, 19.8 μm, 20.8 μm, 21.8 μm, 22.8 μm, 23.8 μm, 24.8 μm, 25.8 μm, 26.8 μm, 27.8 μm, 28.8 μm, 29.8 μm, 30.8 μm, 31.5 μm, or within any two of the above values.

[0044] According to some embodiments of this application, the thickness of the coating is 3um to 10um, which can be 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, or within any two of the above values.

[0045] According to some embodiments of this application, the use of the base membrane is not particularly limited, as long as it is a separator commonly used in secondary batteries. In particular, a base membrane with low resistance to electrolyte ion movement and excellent electrolyte permeability is preferred, including at least one of polyolefins, polyesters, polyacetals, polyamides, polyethylene terephthalate, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyoxymethylene, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polysulfone, and polymethyl methacrylate. Some non-limiting examples of polyolefins include at least one of polyethylene (PE), ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polypropylene (PP), polyethylene-polypropylene copolymer (PE-PP), and polyethylene-polypropylene-polyethylene copolymer.

[0046] According to some embodiments of this application, the particle size distribution width of the deformable polymer is 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 2.0. With a particle size distribution width in the range of 0.5 to 2, the particle size distribution is relatively uniform, and the coating thickness on the diaphragm exhibits good consistency during coating.

[0047] For example, the particle size distribution width of the deformable polymer can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or within any two of the above values.

[0048] According to some embodiments of this application, the Poisson's ratio of the deformable polymer is 0.35 to 0.45.

[0049] Poisson's ratio refers to the ratio of transverse normal strain to axial normal strain when a material is subjected to uniaxial tension or compression. In this embodiment, the deformable polymer has a Poisson's ratio within the above range, which, in conjunction with particle size and softening temperature, makes the deformation of the diaphragm after hot pressing easier to control.

[0050] For example, the Poisson's ratio of the deformable polymer can be 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, or fall within the range of any two of the above values.

[0051] According to some embodiments of this application, the deformable polymer, provided that it meets the above-mentioned particle size range and softening temperature, can be selected from at least one of polyolefin polymers, polyester polymers, polyamide polymers, acrylic polymers, amino resin polymers, and polyurethane polymers.

[0052] According to some embodiments of this application, the deformable polymer includes at least one of polyolefins, polymethyl methacrylate, polystyrene, polyamide, and polyvinylidene fluoride. The selection of such deformable polymers allows for easy hot pressing to achieve a predetermined degree of deformation and also provides flexible compatibility with adhesives, ensuring a uniform and stable coating and preventing interface separation.

[0053] For example, polyolefins include low-density polyethylene, high-density polyethylene, polypropylene, etc.

[0054] According to some embodiments of this application, the coating includes an adhesive, and the mass ratio of the deformable polymer to the adhesive is c, where 0.11 ≤ c ≤ 4.0.

[0055] According to some embodiments of this application, the coating includes an adhesive, and the mass ratio of the deformable polymer to the adhesive is preferably c, where 0.2 ≤ c ≤ 1.0.

[0056] The core of adding binders is to work synergistically with deformable polymers to form a continuous, dense coating, and to achieve the necessary adhesion of the coating to ensure a strong bond between the diaphragm and the electrode.

[0057] For example, c can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or fall within the range of any two of the above values.

[0058] According to some embodiments of this application, the adhesive includes at least one of resin polymers, rubber polymers, and thermoplastic elastomer polymers.

[0059] For example, adhesives include 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; and fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers.

[0060] According to some embodiments of this application, the adhesive includes at least one of polyolefin, polyamic acid, styrene-butadiene rubber latex, polyvinylidene fluoride, polyvinylidene fluoride derivative, aromatic polyamide, and polyimide.

[0061] According to some embodiments of this application, the resin-based polymer includes a water-soluble binder, and the coating includes additives, which include at least one selected from polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium citrate, sodium ethylenediaminetetraacetate, sodium diacetate, sodium hexametaphosphate, sodium silicate, and carboxymethyl cellulose. The synergistic effect of the additives and the water-soluble binder improves the leveling properties, stability, adhesion, and pH adjustment of the coating slurry of this application, resulting in a uniform and consistent final coating without agglomeration and with stable performance.

[0062] According to some embodiments of this application, the coating slurry further includes a solvent, including at least one of dimethylformamide, N-methyl-2-pyrrolidone, tetrahydrofuran, N,N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, and deionized water. This application does not impose any particular limitation on the solvent in the diaphragm coating slurry, as long as it achieves the purpose of this solution; for example, it may include, but is not limited to, at least one of the solvents mentioned above.

[0063] This application does not impose any particular limitation on the coating method of the coating slurry. It can be any coating method known in the prior art, as long as it can achieve the purpose of this solution. For example, it can include, but is not limited to, brushing, spraying, dipping and coating methods.

[0064] To address the aforementioned issues, this application also proposes an electrochemical device, which is one of a battery cell, a battery module, or a battery pack. The electrochemical device includes an electrode, an electrolyte, and the aforementioned battery core.

[0065] An electrochemical device includes any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy and vice versa. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0066] In some embodiments, the electrolyte includes a lithium salt; Lithium salts may include at least one of LiPF6, LiBF4, LiBOB, LiB(C6H5)4, LiB(C2O4)2, LiAsF6, LiCl, LiClO4, LiCH3SO3, LiCF3SO3, LiC4F9SO3, LiC(SO2CF3)3, LiN(SO2CF3)2, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiSiF6, LiSbF6, LiAlO4, LiAlCl4, LiI, and lithium difluoroborate.

[0067] This scheme does not impose any particular restrictions on lithium salts, as long as they can achieve the purpose of this scheme. For example, it may include, but is not limited to, at least one of the lithium salts mentioned above. The use of lithium salts is unrestricted, as long as they can participate in the ion movement of the battery electrochemical reaction.

[0068] This solution does not impose any particular restrictions on the electrolyte; it can be any electrolyte known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the electrolytes mentioned above.

[0069] In some embodiments, the positive electrode includes a positive current collector and a layer of positive active material disposed on at least one side of the positive current collector.

[0070] In some implementations, the positive current collector includes a positive metal foil or a composite positive current collector.

[0071] In some implementations, the positive electrode metal foil includes aluminum foil.

[0072] This solution does not impose any particular restrictions on the positive electrode metal foil, which can be any positive electrode metal foil known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode metal foils.

[0073] In some embodiments, the composite positive current collector includes a metal foil and a conductive layer disposed on at least one side of the metal foil; The conductive layer includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0074] This solution does not impose any particular limitation on the conductive layer, which can be any conductive layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the conductive layers mentioned above.

[0075] This solution does not impose any particular restrictions on the composite positive electrode current collector, which can be any composite positive electrode current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, the composite positive electrode current collector mentioned above.

[0076] This solution does not impose any particular restrictions on the positive electrode current collector, which can be any positive electrode current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, the positive electrode current collector mentioned above.

[0077] In some embodiments, the positive electrode active material layer includes a positive electrode active material; The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0078] This solution does not impose any particular restrictions on the positive electrode active material. It can be any positive electrode active material known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode active materials.

[0079] In some embodiments, the positive electrode active material includes a dopant; The dopant includes at least one of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, and Ge.

[0080] This solution does not impose any particular restrictions on the dopant, which can be any dopant known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the dopants mentioned above.

[0081] In some embodiments, the positive electrode active material layer includes a positive electrode binder; The positive electrode binder includes at least one of polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropylene, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone, acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer.

[0082] This solution does not impose any particular restrictions on the positive electrode binder, which can be any positive electrode binder known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the positive electrode binders mentioned above.

[0083] In some embodiments, the positive electrode active material layer includes a conductive agent; The positive electrode conductive agent includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, and mesoporous carbon.

[0084] This solution does not impose any particular restrictions on the positive electrode conductive agent, which can be any positive electrode conductive agent known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the positive electrode conductive agents mentioned above.

[0085] In some embodiments, the positive electrode active material layer includes additives.

[0086] In some implementations, the additives include thickeners; Thickeners include at least one of cellulose thickeners, acrylate thickeners, and polyurethane thickeners.

[0087] In some embodiments, the thickener includes at least one of sodium carboxymethyl cellulose, sodium hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, polyvinyl alcohol, and polyvinylpyrrolidone.

[0088] This solution does not impose any particular restrictions on the thickener, which can be any thickener known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the thickeners mentioned above.

[0089] In some implementations, the additives include dispersants; Dispersants include surfactant dispersants and / or polymeric dispersants.

[0090] In some embodiments, the dispersant includes at least one of polyvinylpyrrolidone, polyoxyethylene ether, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium lignosulfonate, polyacrylic acid, polymethacrylic acid, sodium polystyrene sulfonate, and sodium carboxymethyl cellulose.

[0091] This solution does not impose any particular limitation on the dispersant, which can be any dispersant known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the dispersants mentioned above.

[0092] This solution does not impose any particular restrictions on additives, which can be any additives known in the prior art, as long as they can achieve the purpose of this application. For example, they can include, but are not limited to, at least one of the additives mentioned above.

[0093] This solution does not impose any particular restrictions on the positive electrode active material layer. It can be any positive electrode active material layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the above-mentioned positive electrode active material layers.

[0094] This solution does not impose any particular restrictions on the positive electrode, which can be any positive electrode known in the prior art, as long as it can achieve the purpose of this application, such as including but not limited to the positive electrode mentioned above.

[0095] In some embodiments, the negative electrode includes a negative electrode current collector and a layer of negative electrode active material disposed on at least one side of the negative electrode current collector.

[0096] In some embodiments, the negative electrode current collector includes a negative electrode metal foil or a composite negative electrode current collector.

[0097] In some implementations, the negative electrode metal foil includes copper foil.

[0098] In some embodiments, the composite negative electrode current collector includes a negative electrode metal foil and a negative electrode conductive layer disposed on at least one side of the negative electrode metal foil.

[0099] This solution does not impose any particular limitation on the metal foil; it can be any metal foil known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, the metal foils mentioned above. This solution also does not impose any particular limitation on the conductive layer of the composite negative electrode current collector; it can be any conductive layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the conductive layers mentioned above.

[0100] This solution does not impose any particular restrictions on the negative electrode current collector, which can be any negative electrode current collector known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode current collectors mentioned above.

[0101] In some embodiments, the negative electrode active material layer includes a negative electrode active material; Negative electrode active materials include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres, Sn, SnO2, SnO, and Li4Ti5O. 12 At least one of Si materials, silicon-carbon composite materials, silicon-nitrogen composite materials, and silicon-oxygen composite materials.

[0102] This solution does not impose any particular restrictions on the negative electrode active material. It can be any negative electrode active material known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode active materials mentioned above.

[0103] In some embodiments, the negative electrode active material layer includes a negative electrode binder; The negative electrode binder includes at least one of the following: polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene.

[0104] This solution does not impose any particular restrictions on the negative electrode binder, which can be any negative electrode binder known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode binders mentioned above.

[0105] In some embodiments, the negative electrode active material layer includes a negative electrode conductive agent.

[0106] This solution does not impose any particular limitation on the negative electrode conductive agent, which can be any negative electrode conductive agent known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode conductive agents mentioned above.

[0107] In some embodiments, the negative electrode active material layer includes additives.

[0108] In some embodiments, the additives include thickeners; the additives include dispersants.

[0109] This solution does not impose any particular restrictions on the additives used in the negative electrode active material layer. Any additive known in the prior art can be used, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of the additives mentioned above. Similarly, this solution does not impose any particular restrictions on the thickeners used in the negative electrode active material layer. Any thickener known in the prior art can be used, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of the thickeners mentioned above. Finally, this solution does not impose any particular restrictions on the dispersants used in the negative electrode active material layer. Any dispersant known in the prior art can be used, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of the dispersants mentioned above.

[0110] This solution does not impose any particular restrictions on the negative electrode active material layer. It can be any negative electrode active material layer known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrode active material layers mentioned above.

[0111] This solution does not impose any particular restrictions on the negative electrode, which can be any negative electrode known in the prior art, as long as it can achieve the purpose of this application. For example, it can include, but is not limited to, at least one of the negative electrodes mentioned above.

[0112] It should be stated that regardless of how the positive electrode, negative electrode, and electrolyte are conventionally selected, the aforementioned beneficial effects can be obtained as long as the electrochemical device includes the aforementioned battery core.

[0113] To address the aforementioned problems, this application also provides an electronic device, including the electrochemical device described in this application.

[0114] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. According to some embodiments of this application, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, android robots, etc.

[0115] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the reagents used, unless otherwise specified, are commercially available reagents and materials. The source information of the raw materials used in the following examples and comparative examples is for illustrative purposes only and does not constitute any restriction on the procurement of raw materials. Those skilled in the art will know that the relevant raw materials can be obtained through other commercial channels or prepared by conventional methods in the art.

[0116] The CAS numbers and supplier information for the main raw materials used in this application are as follows: .

[0117] Example 1 1. Preparation of the diaphragm The deformable polymer PMMA was selected, with a softening temperature of 60℃, a Dv10 of 3μm, a Dv50 of 7μm, a Dv90 of 11.6μm, and a particle size distribution (D90-D10) / D50 of 1.2. The adhesive PVDF was dissolved in the organic solvent NMP. After complete dissolution, PMMA was added and dispersed evenly to obtain a coating slurry. The coating slurry was uniformly coated on one surface of a polyethylene film. After drying in an oven, a diaphragm was obtained. In the diaphragm coating, the mass ratio of PMMA to PVDF was 3:7, and the thickness of the diaphragm coating was 4.2μm.

[0118] 2. Preparation of battery core The positive electrode material, conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), and pH-responsive acid removal material are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 93:3:2:2 to obtain a positive electrode slurry with a solid content of 40%-45%. This slurry is then coated onto the positive electrode current collector Al foil, dried, cold-pressed, and slit to obtain the positive electrode sheet. Artificial graphite (anode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) are thoroughly mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5 to obtain a cathode slurry with a solid content of 40%-45%. This slurry is coated onto Cu foil (anode current collector), dried, cold-pressed, and slit to obtain a cathode sheet. The positive electrode, separator, and negative electrode are stacked in sequence, with the battery core positioned between the positive and negative electrodes to provide a safe isolation. The battery core is then wound up to obtain the battery core.

[0119] 3. Preparation of battery cells A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC) in a mass ratio of 20:30:20:28:2, with a mass ratio of 8:92) was used as the electrolyte for lithium-ion secondary batteries. The electrode assembly was placed in a packaging shell, the electrolyte was injected, and the package was sealed to obtain a lithium-ion battery cell. The hot pressing was carried out at 85°C and 1 MPa for 1 hour.

[0120] Examples 2 to 10 Examples 2-10 were prepared using the same method as Example 1, but differed from Example 1 in that the physicochemical parameters of the deformable polymer and the mass ratio of the binder were different.

[0121] Comparative Examples 1-3 Comparative Example 1 uses the same preparation method as Example 1, except that the particle size of the deformable polymer in the diaphragm coating is changed or no deformable polymer is incorporated.

[0122] Furthermore, performance tests were conducted on the above embodiments and comparative examples, and the test methods are as follows: 1) Coating thickness: Tested using a Malm thickness gauge.

[0123] 2) Coating peel strength test: To evaluate the adhesion strength between the coating and the substrate, the diaphragm is cut into 19mm pieces. A 50mm sample strip was attached to a steel plate with the coating facing outwards. Then, 3M tape was applied over the coating, and the strip was rolled three times with a 5kg roller. The peel strength of the diaphragm and tape at 180° was tested at a tensile speed of 100mm / min.

[0124] 3) Coating adhesion strength test: The porous coating side of the composite diaphragm in each embodiment and comparative example was hot-pressed with the positive electrode sheet (the current collector was aluminum foil, and the positive electrode active layer was composed of LiCoO2, conductive agent (conductive carbon black) and binder (polyvinylidene fluoride) in a mass ratio of 96:2:2) at 1 MPa and 95°C for 3 min. Then, a universal tensile testing machine was used to perform a 180° peel tensile test on the composite diaphragm and the positive electrode sheet at a tensile speed of 100 mm / min. The force detected when the positive electrode sheet was peeled off is the adhesion strength between the composite diaphragm and the positive electrode sheet.

[0125] 4) Coating deformability test: Cut the diaphragm into 80mm pieces. 15cm, test the total thickness D0 of 8 diaphragms, then hot press for 1 hour at 85℃ and 1MPa pressure, let it stand naturally for 30 seconds after hot pressing, and then record the total thickness D1 after hot pressing. The compressible thickness of the coating is (D0-D1) / 8.

[0126] 5) Diaphragm thickness difference and thickness compression ratio (a / b) test: First, mark at least three measurement points on the side of the core to be tested, at the center of the straight area and at the apex of the corner. Record the initial thickness T0 at each point using a high-precision thickness gauge. Then, place the core in a preheated flatbed hot press at 85°C, apply a pressure of 1 MPa and hold it for 1 hour. During this time, the thickness will continue to change due to high-temperature creep. After the time is up, release the pressure and remove the core. Be sure to allow it to cool naturally to below 30°C at room temperature to eliminate the effects of thermal expansion. Then, remeasure the thickness T1 after hot pressing at the same marked points. The thickness difference between the straight area and the corner area of ​​the diaphragm is T0-T1. The compression ratio is calculated using the formula a or b = (T0-T1) / T0 × 100%. Take the average value of multiple measurement points in the straight area and the corner area as the final result.

[0127] 6) Liquid retention coefficient test: The liquid injection coefficient for the assembly process in the embodiments and comparative examples was set to 1.45 g / Ah, and the liquid retention coefficient was obtained by direct weighing.

[0128] 7) Lithium plating test: At 25 ℃, the separators prepared in the examples and comparative examples were assembled into lithium-ion batteries. The batteries were charged at a constant current of 3 C to 4.35 V, then charged at a constant current and voltage of 1.8 C to 4.48 V, with a cutoff current of 0.05 C. Finally, they were discharged at 0.7 C to 3.0 V. Following the above charge-discharge cycle, the lithium-ion batteries were subjected to 50 cycles to obtain fully charged batteries. The battery interface was then disassembled, the state of the negative electrode was photographed, the area of ​​lithium plating on the interface was counted, and the lithium plating level was evaluated according to the standards in Table 1.

[0129] Table 1. Evaluation Criteria for Lithium Plaque Grade on Negative Electrode Sheets After Charge and Discharge of Lithium-ion Batteries .

[0130] Record the performance results in Table 2: Table 2. Comparative Parameters of Examples .

[0131] Table 3. Comparative Parameters of Examples .

[0132] The performance results show that: Compared with Example 1, Comparative Example 1 did not add deformable polymer to the diaphragm coating, and the compressible thickness after hot pressing was 0. The compressibility a in the straight area and the compressibility b in the corner area were both 0, resulting in a liquid retention coefficient of only 1.18 for Comparative Example 1. This indicates that without the participation of deformable polymer, the diaphragm has no buffer and liquid storage space in the corner area, the interfacial liquid phase is depleted, and severe lithium plating occurs after cycling.

[0133] Compared with Example 1, Comparative Example 2 had a softening temperature of 35°C. After hot pressing, its a value was as high as 0.878 and b value was 0.307. The compression ratio of the flat region far exceeded the constraint range, and the liquid retention coefficient was only 1.16. Due to the excessively low softening temperature, Comparative Example 2 was over-compacted, the pores in the flat region collapsed, and lithium plating was severe.

[0134] Compared with Example 1, Comparative Example 3 uses PTFE with a softening temperature of 327°C. After hot pressing, the a value is only 0.186 and the b value is only 0.074, which has low compressibility. The larger gap between the diaphragm and the electrode is beneficial for liquid retention, but the polymer particles have a high softening point and the coating adhesion strength is low.

[0135] Compared with Example 1, Examples 2 and 3 have higher compression ratios in the flat region, and their performance is still excellent, indicating that when the compression ratio in the flat region approaches the upper limit but does not exceed it, the interface stability can still be maintained.

[0136] Compared to Example 1, Examples 4-6 used different polymers such as PP, PMMA (40℃), and PP (160℃), and had different softening temperatures and particle sizes. However, after hot pressing, the a-values ​​were concentrated between 0.535 and 0.558, and the b-values ​​were concentrated between 0.193 and 0.223, which are close to the compression ratios of Example 1. The liquid retention coefficient and lithium plating performance were also excellent. This indicates that as long as the compression ratios a and b fall within a suitable range, the specific choice of materials will not worsen the performance results.

[0137] Compared to Example 1, in Example 7, the polymer D50 was reduced from 7 μm to 3 μm, and the initial coating thickness was reduced from 4.2 μm to 2 μm. However, the ratio of a=0.5 to b=0.175 after hot pressing was exactly the same as in Example 1, resulting in a compressible thickness of only 1 μm. Both the liquid retention coefficient and lithium plating performance were excellent. This demonstrates that, under the premise of a reasonable compression ratio, even with a reduction in absolute thickness, sufficient buffering can still be maintained in the corner area.

[0138] Compared to Example 1, Examples 8-10 showed a decrease in the mechanical properties of the coating. In Example 8, due to the excessively large and widely distributed particle size, the peel strength and adhesive strength of the coating decreased. In Example 9, the deformable polymer content decreased from 30% to 10%, indicating a decrease in liquid retention capacity. In Example 10, due to the excessively high deformable polymer content and low binder content, the peel strength and adhesive strength of the coating also decreased. However, the compressibility in the straight and corner regions of all three examples remained within the effective range, and no significant deterioration was observed in the liquid retention coefficient and lithium plating, indicating that the interfacial stability of the coating remained reliable.

[0139] When the term "embodiment" is used in the specification, it means that the invention has at least one embodiment that includes the specific feature, structure, material, or property. Therefore, expressions such as "in some embodiments," "in certain embodiments," and "exemplary" used throughout the document do not necessarily refer to the same embodiment. Furthermore, the specific feature, structure, material, or property can be combined in any suitable manner in one or more embodiments.

[0140] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the invention, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the invention.

Claims

1. A battery winding core, the battery winding core comprising a straight section and a corner section, characterized in that, The battery core includes a separator, the separator comprising a base film and a coating on at least one surface of the base film, the coating comprising a deformable polymer having a softening temperature of 40°C to 160°C; and, After the battery core is hot-pressed at a temperature of 85°C and a pressure of 1~2MPa, the thickness compression rate of the straight area is a, 30%≤a≤80%, the thickness compression rate of the corner area is b, 10%≤b≤25%, and the thickness difference between the separator in the straight area and the corner area is 1um~10um.

2. The battery core according to claim 1, characterized in that, The deformable polymer has a volume average particle size Dv10 of 2.0 μm to 5 μm. The deformable polymer has a volume average particle size Dv50 of 3 μm to 15 μm. The deformable polymer has a volume average particle size Dv90 of 3.8 μm to 31.5 μm.

3. The battery core according to claim 2, characterized in that, The particle size distribution width of the deformable polymer is 0.5≤(Dv90-Dv10) / Dv50≤2.

0.

4. The battery core according to claim 1, characterized in that, The deformable polymer has a Poisson's ratio of 0.35 to 0.

45.

5. The battery core according to claim 1, characterized in that, The deformable polymer includes at least one of polyolefin, polymethyl methacrylate, polystyrene, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and polyimide.

6. The battery core according to claim 1, characterized in that, The coating includes an adhesive, wherein the mass ratio of the deformable polymer to the adhesive is c, and 0.2 ≤ c ≤ 1.

0.

7. The battery core according to claim 6, characterized in that, The adhesive includes at least one of resin-based polymers, rubber-based polymers, and thermoplastic elastomer-based polymers.

8. The battery core according to claim 7, characterized in that, The resin-based polymer includes a water-soluble binder, and the coating includes an additive, which includes at least one of polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium citrate, sodium ethylenediaminetetraacetate, sodium diacetate, sodium hexametaphosphate, sodium silicate, and carboxymethyl cellulose.

9. An electrochemical device, characterized in that, Includes the battery core as described in any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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