Roll core, battery and electric device

Abstract

The invention provides a roll core, a battery and a power utilization device, and relates to the technical field of batteries. The roll core comprises a pole piece and an insulation protection layer, the pole piece is bent to form a bending area, the insulation protection layer is adhered to the surface of an active substance layer of the pole piece, the insulation protection layer is at least arranged in the bending area, the insulation protection layer is partially adhered to an inactive substance area of the pole piece, in the height direction of the roll core, the total size of the inactive substance area is d1mm, the size of the pole piece is d2mm, and the total size of the insulation protection layer is d1mm. The ratio of d1 to d2 is M, in the thickness direction of the pole piece, the total size of the active material layer on the pole piece is D1 [mu] m, the size of the pole piece is D2 [mu] m, the ratio of D1 to D2 is N, and the elongation at break of the current collector is K%. And (M * K) / N is greater than or equal to 0.016 and less than or equal to 2.3, so that the material falling risk of the roll core at the bending area can be reduced, the lithium dendrites are unlikely to pierce the pole piece, the short-circuit risk of the pole piece is reduced, the overall energy density of the battery can be improved, and the service life of the battery is prolonged.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a winding core, a battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density, good cycle performance, no memory effect, safety, and environmental friendliness, and are widely used in electric vehicles and portable electronic products. The core of a lithium-ion battery is formed by winding electrodes and a separator.

[0003] In related technologies, due to the characteristics of winding and forming, stress concentration occurs at the corners of the lithium-ion battery core, which easily leads to electrode material loss. To address this structural defect, a conventional protective measure is to attach an insulating protective layer to the corners.

[0004] However, during the use of lithium-ion batteries, the risk of material falling off the core at the corners still increases. Summary of the Invention

[0005] This application provides a winding core, a battery, and an electrical device to address the problem of increased risk of material falling off the winding core at corners during the use of lithium-ion batteries.

[0006] In a first aspect, embodiments of this application provide a winding core, comprising:

[0007] An electrode sheet, the electrode sheet comprising a current collector and an active material layer coated on at least one surface of the current collector, the electrode sheet being bent to form a bending region, and at least one end of the electrode sheet comprising an inactive material region in the height direction of the winding core.

[0008] An insulating protective layer is bonded to the surface of the active material layer, the insulating protective layer is at least disposed in the bending area, and the insulating protective layer is partially bonded to the inactive material area;

[0009] In the height direction of the core, the total size of the inactive material region is d1mm, the size of the electrode is d2mm, and the ratio of d1 to d2 is M;

[0010] In the thickness direction of the electrode, the total size of the active material layer on the electrode is D1μm, the size of the electrode is D2μm, and the ratio of D1 to D2 is N;

[0011] The elongation at break of the current collector is K%.

[0012] The M, N, and K satisfy the condition: 0.016 ≤ (M × K) / N ≤ 2.3.

[0013] Secondly, embodiments of this application provide a battery, including a housing and the winding core described in the first aspect, wherein a receiving cavity is provided inside the housing, and the winding core is placed inside the receiving cavity.

[0014] Thirdly, embodiments of this application provide an electrical device including the battery described in the second aspect.

[0015] This application provides a core, a battery, and an electrical device. If (M×K) / N is less than 0.016, the proportions of M, K, or N may be too small, increasing the risk of material loss at the bending area of ​​the core and making it easier for lithium dendrites to pierce the electrode, thus increasing the risk of short circuits. If (M×K) / N is greater than 2.3, the proportions of M, K, or N may be too large, resulting in a lower overall energy density of the battery and a shorter battery life. By ensuring that (M×K) / N is greater than or equal to 0.016 and less than or equal to 2.3, the risk of material loss at the bending area of ​​the core can be reduced, lithium dendrites are less likely to pierce the electrode, the risk of short circuits can be reduced, the overall energy density of the battery can be improved, and the battery life can be extended. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1a This is a schematic diagram of the structure of the first type of winding core provided in the embodiments of this application;

[0018] Figure 1b for Figure 1a A top view of the core in the winding;

[0019] Figure 2 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application;

[0020] Figure 3 A schematic diagram illustrating the connection between an electrode sheet and an insulating protective layer, provided in an embodiment of this application;

[0021] Figure 4 for Figure 1a A schematic diagram of the core after it has been unfolded;

[0022] Figure 5 This is a schematic diagram of the second type of roll core after being unfolded, provided in an embodiment of this application.

[0023] Figure 6 This is a schematic diagram of the third type of core after it has been unfolded, as provided in the embodiments of this application.

[0024] Figure 7 This is a schematic diagram illustrating the connection between another electrode and an insulating protective layer, provided in an embodiment of this application.

[0025] Figure 8 This is a schematic diagram of the structure of a battery provided in an embodiment of this application.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1-Core; 10-Electrode; 101-First end; 102-Second end; 11-Current collector; 12-Active material layer; 100-Bending area; 13-Taper; 200-Inactive material area; 20-Insulating protective layer; 2-Shell; 3-Injection hole; 201-First surface; 202-Second surface;

[0028] 1000 - Straight area; 2000 - Bending area; 30 - Diaphragm; 1010 - Head end. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. 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.

[0030] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixation," etc., 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, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0033] In the above description, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0034] The core is formed by winding. Specifically, a core is made by winding consecutive positive electrode plates, negative electrode plates, and separators, with the separator located between adjacent positive and negative electrode plates.

[0035] The core forming process includes a winding process and a pressing process. Continuous positive electrode sheet, negative electrode sheet, and separator are continuously wound on a winding needle. After the winding needle is pulled out, the circular core is pressed to form a core that is similar to an ellipse or a racetrack shape. During the pressing process, the positive electrode sheet and negative electrode sheet have stress concentration at the bending point, which increases the risk of material loss.

[0036] The positive electrode is one of the core components in a battery that carries the positive electrode active material. During charging, metal ions (such as lithium ions) are extracted from the crystal lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (such as lithium ions) are extracted from the negative electrode and intercalate into the crystal lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0037] The positive electrode sheet includes a positive current collector and a positive active material layer, wherein the positive active material layer is coated on at least one surface of the positive current collector.

[0038] The thickness of the positive electrode current collector is greater than 6 μm and less than or equal to 18 μm. The thickness of the positive electrode current collector can be 6 μm, 7 μm, 9 μm, 10 μm, 15 μm, or 18 μm, etc.

[0039] The positive electrode active material layer includes the positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, at least one of the following: lithium phosphates, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive electrode active materials in batteries. These positive electrode active materials can be used alone or in combination of two or more. The lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. The lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2 or LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0040] The conductive agent in the positive electrode active material layer includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene, and carbon nanofibers.

[0041] The binder of the positive electrode active material layer includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0042] The positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0043] During the charging and discharging process of the battery, the negative electrode acts as a carrier for active ions (such as Li) coming from the positive electrode. The active ions can be inserted or extracted, playing a role in energy storage and release.

[0044] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is coated on at least one surface of the negative electrode current collector.

[0045] The negative electrode active material layer includes carbon-based materials (graphite or natural graphite, etc.), silicon-based materials (elemental silicon, silicon oxides, silicon-carbon composites or silicon-nitrogen composites, etc.), tin-based materials (elemental tin, tin oxides or tin alloys, etc.), lithium titanate materials, and metallic lithium materials, etc.

[0046] The thickness of the negative electrode current collector is greater than 4 μm and less than or equal to 12 μm. The thickness of the positive electrode current collector can be 4 μm, 6 μm, 7 μm, 9 μm, 10 μm, or 12 μm, etc.

[0047] The negative electrode current collector can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc., with a surface silver plating treatment. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy, etc.) on a polymer base material (such as a polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0048] A diaphragm is placed between the positive and negative electrode plates to separate them and prevent them from short-circuiting due to contact.

[0049] The diaphragm can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride.

[0050] The membrane surface may also be coated, which may be an inorganic coating and / or an organic coating. Inorganic coating materials include at least one of alumina, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, and boehmite. Organic coatings include at least one of aramid coatings and polyvinylidene fluoride (PVDF) coatings.

[0051] Research has found that electrode shedding at bends is primarily due to the large thickness of the active material layer and the high curvature at the bend, exacerbating the risk of shedding. Additionally, the poor toughness of the foil increases the tendency to break. Furthermore, electrode shedding is also caused by the insulating protective layer being entirely bonded to the surface of the active material layer. After electrolyte injection into the core, the adhesive layer on the insulating protective layer absorbs and swells, increasing the risk of the insulating protective layer detaching. In summary, this solution increases the adhesive strength between the insulating protective layer and the electrode by partially bonding the insulating protective layer to the non-active area of ​​the electrode. Simultaneously, it controls the elongation at break of the current collector and the thickness of the active material layer to reduce core shedding. Furthermore, it avoids excessively strong overall adhesion of the insulating protective layer, which could prevent the electrolyte from transporting lithium ions between the positive and negative electrodes, leading to the formation of lithium dendrites that could pierce the electrode and cause a short circuit.

[0052] The core, battery, and power supply device provided in this application will be described in detail below with reference to specific embodiments.

[0053] See Figure 1a In a first aspect, embodiments of this application provide a winding core 1, including an electrode 10 and a diaphragm 30. The electrode 10 and the diaphragm 30 are wound together. The winding direction of the electrode 10 is the same as the winding direction of the winding core 1.

[0054] See Figure 1a and Figure 1b The length direction of core 1 is the X direction. The thickness direction of core 1 is the Y direction. The height direction of core 1 is the Z direction. The X, Y, and Z directions are perpendicular to each other.

[0055] The core 1 includes a straight region 1000 and a bent region 2000. In the length direction of the core 1, the bent region 2000 is connected to one side of the straight region 1000.

[0056] The straight portion of core 1 is designated as the straight area 1000. The bent portion of core 1 is designated as the bent area 2000.

[0057] It should be noted that the core 1 includes two bending regions 2000, which are located on both sides of the straight region 1000 along the length of the core 1.

[0058] exist Figure 1a and Figure 1b In the middle, electrode 10 is in a wound state. Figure 4 In the middle, electrode 10 is in the unfolded state.

[0059] See Figure 1a and Figure 1b The electrode 10 is wound. After the electrode 10 is wound, the electrode 10 is bent to form a bending area 100. That is, the part of the electrode 10 located in the bending area 2000 of the core 1 is the bending area 100.

[0060] The electrode 10 includes a current collector 11 and an active material layer 12 coated on at least one surface of the current collector 11.

[0061] When electrode 10 is a positive electrode, current collector 11 is a positive current collector, and active material layer 12 is a positive active material layer. When electrode 10 is a negative electrode, current collector 11 is a negative current collector, and active material layer 12 is a negative active material layer.

[0062] See Figure 2 In the height direction of the core 1, at least one end of the electrode 10 includes an inactive material region 200. It can be understood that in the height direction of the core 1, the area at least one end of the current collector 11 that is not coated with active material is the inactive material region 200.

[0063] Core 1 also includes an insulating protective layer 20 (see Figure 1b The insulating protective layer 20 is bonded to the surface of the active material layer 12, and the insulating protective layer 20 is provided at least in the bending area 100.

[0064] The insulating protective layer 20 is used to relieve bending stress and prevent the electrode sheet 10 from shedding. It should be noted that the shedding of active material from the electrode sheet 10 of the core 1 represents material shedding. For example, the insulating protective layer 20 can be an adhesive tape.

[0065] In some examples, the insulating protective layer 20 includes a base film layer and an adhesive layer. The base film layer serves to carry the adhesive layer.

[0066] The base film layer is used to support the adhesive layer. The base film layer can be made of at least one or more of the following materials: polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, tetrafluoropropylene-vinylidene fluoride copolymer, trifluorochloropropylene-vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, and nonwoven fabric.

[0067] The adhesive layer can be made of at least one of the following: acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic-grafted polypropylene, polyvinylidene fluoride, maleic anhydride-grafted polypropylene, carboxymethyl cellulose, polyimide, polyetherimide, styrene-isoprene-styrene copolymer rubber, polyethylene phthalate, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, and styrene-isoprene-styrene copolymer.

[0068] The insulating protective layer 20 is partially bonded to the inactive material region 200. It is understood that at least a portion of the insulating protective layer 20 is bonded to the active material layer 12 and at least a portion is bonded to the inactive material region 200.

[0069] In the height direction of core 1, the total dimension of the inactive material region 200 is d1mm. d1 satisfies: 1mm≤d1mm≤10mm. The value of d1mm can be 1mm, 2mm, 5mm, 7mm, 9mm, or 10mm, etc.

[0070] See in some examples Figure 2 In the height direction of the core 1, inactive material areas 200 are provided on both sides of the active material layer 12. The size of the inactive material area 200 on one side is d11mm, and the size of the inactive material area 200 on the other side is d12mm. The sum of d11mm and d12mm is d1mm.

[0071] In the height direction of the core 1, the size of the electrode 10 is d2mm. d2 satisfies: 70mm≤d2mm≤160mm. The value of d2mm can be 70mm, 80mm, 100mm, 110mm, 130mm, 150mm or 160mm, etc.

[0072] The ratio of d1 to d2 is M. M satisfies: 0.007 ≤ M ≤ 0.14. The value of M can be 0.007, 0.01, 0.05, 0.1, 0.11, 0.12 or 0.14, etc.

[0073] In the thickness direction of the electrode 10, the total size of the active material layer 12 on the electrode 10 is D1μm.

[0074] See in some examples Figure 2Active material layers 12 are disposed on both sides of the current collector 11 in the thickness direction of the electrode 10. The size of the active material layer 12 on one side is D11μm, and the size of the active material layer 12 on the other side is D12μm. The sum of D11μm and D12μm is D1μm.

[0075] In the thickness direction of electrode 10, the size of electrode 10 is D2μm.

[0076] When electrode 10 is a positive electrode, 30μm≤D1μm≤210μm, 36μm≤D2μm≤228μm. When electrode 10 is a negative electrode, 30μm≤D1μm≤200μm, 34μm≤D2μm≤212μm.

[0077] The ratio of D1 to D2 is N. N satisfies: 0.7 ≤ N ≤ 0.98. The value of N can be 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 0.98, etc.

[0078] If N is greater than 0.98, the proportion of D1 will be too large, increasing the risk of material loss at the bending zone 100 of the core and making it easier for lithium dendrites to pierce the electrode, thus increasing the risk of short circuits. If N is less than 0.7, the proportion of D1 will be too small, resulting in a small total size of the active material layer 12 on the electrode 10 in the thickness direction, leading to a lower energy density of the core 1. By setting N to be greater than or equal to 0.7 and less than or equal to 0.98, the risk of material loss at the bending zone 100 of the core 1 can be reduced, lithium dendrites are less likely to pierce the electrode, the risk of short circuits can be reduced, and the energy density of the core 1 can be improved.

[0079] The fracture elongation of current collector 11 is K%. Fracture elongation measures the plastic deformation capacity of a material. The larger the fracture elongation, the better the toughness and the stronger the plastic deformation; the smaller the fracture elongation, the more brittle it is, the less easily it is deformed, and the easier it is to break.

[0080] K satisfies: 2% ≤ K% ≤ 12%. The value of K% can be 2%, 3%, 5%, 7%, 9%, 10%, or 12%, etc.

[0081] M, N, and K satisfy the condition: 0.016 ≤ (M×K) / N ≤ 2.3. The value of (M×K) / N can be 0.016, 0.02, 0.025, 0.1, 1, 1.5, 2, or 2.3, etc.

[0082] If (M×K) / N is less than 0.016, the proportions of M, K, or N will be too small, increasing the risk of material loss at the bending zone 100 of the core 1. This also makes it easier for lithium dendrites to pierce the electrode, increasing the risk of short circuits in electrode 10. If (M×K) / N is greater than 2.3, the proportions of M, K, or N will be too large, resulting in lower overall battery energy density and shortened battery life. By ensuring (M×K) / N is greater than or equal to 0.016 and less than or equal to 2.3, the risk of material loss at the bending zone 100 of the core 1 can be reduced, lithium dendrites are less likely to pierce electrode 10, the risk of short circuits in the electrode is reduced, the overall battery energy density can be improved, and the battery life can be extended.

[0083] In some examples, M, N, and K satisfy: 0.035 ≤ (M×K) / N ≤ 1.605. The value of (M×K) / N can be 0.035, 0.038, 0.1, 1, 1.5, or 1.605, etc.

[0084] Compared to (M×K) / N being greater than 1.605 and less than or equal to 2.3, (M×K) / N being less than or equal to 1.605 results in a higher overall energy density and a longer battery life. Compared to (M×K) / N being greater than or equal to 0.016 and less than 0.035, (M×K) / N being greater than or equal to 0.035 reduces the risk of material loss at the bending zone of core 1 and makes it less likely for lithium dendrites to pierce the electrode, thus reducing the risk of short circuits in electrode 10. By using (M×K) / N greater than or equal to 0.035 and less than or equal to 1.605, the risk of material loss at the bending zone 100 of core 1 can be further reduced, making it less likely for lithium dendrites to pierce the electrode, further reducing the risk of short circuits in the electrode, and further improving the overall energy density of the battery and extending its lifespan.

[0085] In one possible implementation, K satisfies: 2% ≤ K% ≤ 12%. The value of K% can be 2%, 3%, 5%, 7%, 9%, 10%, or 12%, etc.

[0086] If K% is less than 2%, the current collector 11 will have poor bending resistance and be prone to breakage, increasing the risk of material loss from the core 1 at the bending zone 100. This also makes it easier for lithium dendrites to pierce the electrode 10, increasing the risk of a short circuit in the electrode 10. If K% is greater than 12%, the current collector 11 will have strong plastic deformation, easily undergoing plastic deformation during the winding of the electrode 10. This can result in wrinkles, wavy protrusions, or localized collapses, preventing the layers of the electrode 10 from adhering tightly and creating additional gaps. This leads to a lower overall energy density of the battery and a shorter battery life. By setting K% to 2% or greater and 12% or less, the risk of material loss from the core 1 at the bending zone 100 can be reduced, lithium dendrites are less likely to pierce the electrode 10, the risk of a short circuit in the electrode 10 can be reduced, the overall energy density of the battery can be improved, and the battery life can be extended.

[0087] See Figure 2 In the thickness direction of electrode 10, the current collector 11 has a size of D3μm, where D3 satisfies: 4μm≤D3μm≤18μm. The value of D3μm can be 4μm, 5μm, 7μm, 9μm, 10μm, 15μm, or 18μm, etc.

[0088] If D3μm is greater than 18μm, the current collector 11 will be too large in the thickness direction of the electrode 10, causing it to encroach on the space of the active material and resulting in a lower overall energy density of the battery. If D3μm is less than 4μm, the current collector 11 will be too small in the thickness direction of the electrode 10, making it prone to breakage during the winding process of the electrode 10. This increases the risk of material loss at the bending zone 100 of the core 1 and makes it easier for lithium dendrites to pierce the electrode 10, increasing the risk of short circuits in the electrode 10. By ensuring that D3μm is greater than or equal to 4μm and less than or equal to 18μm, the risk of material loss at the bending zone 100 of the core 1 can be reduced, the risk of lithium dendrites piercing the electrode 10 can be reduced, the risk of short circuits in the electrode 10 can be decreased, and the overall energy density of the battery can be improved.

[0089] It should be noted that in this embodiment, the core 1 can only satisfy K% greater than or equal to 2% and less than or equal to 12%, or it can only satisfy D3μm greater than or equal to 4μm and less than or equal to 18μm, or it can simultaneously satisfy K% greater than or equal to 2% and less than or equal to 12%, D3μm greater than or equal to 4μm and less than or equal to 18μm.

[0090] In one possible implementation, see Figure 3In the thickness direction of the electrode 10, there are active material layers 12 on both sides of the current collector 11, and insulating protective layers 20 are respectively bonded to the active material layers 12 on both sides of the current collector 11. With this configuration, by bonding the insulating protective layers 20 to the active material layers 12 on both sides of the current collector 11, the bending stress of the active material layers 12 on both sides of the current collector 11 can be alleviated, and the risk of material loss of the active material layers 12 on both sides of the current collector 11 at the bending area 100 can be reduced.

[0091] In one possible implementation, see Figure 4 The core 1 includes at least two insulating protective layers 20, the at least two insulating protective layers 20 including a first insulating protective layer and a second insulating protective layer, the first insulating protective layer having a first center line L1, and the second insulating protective layer having a second center line L2.

[0092] Among them, the first center line L1 and the second center line L2 both extend along the height direction of the core 1.

[0093] The first insulating protective layer is at least partially located on the bending area 100 on the -X direction side of the electrode 10, and the second insulating protective layer is at least partially located on the bending area 100 on the +X direction side of the electrode 10.

[0094] The line furthest from the second insulating layer on the -X side of the first insulating layer is the first centerline. The first insulating layer is symmetrical with respect to the first centerline L1.

[0095] The line furthest from the first insulating layer on the +X direction side of the second insulating layer is the second center line. The second insulating layer is symmetrical with respect to the second center line L2.

[0096] Along the length of the core 1, the first center line L1 and the second center line L2 are located on opposite sides of the core 1. The distance between the first center line L1 and the second center line L2 is D4mm, where D4 satisfies: 110mm ≤ D4mm ≤ 310mm. The value of D4mm can be 110mm, 150mm, 200mm, 250mm, 300mm, or 310mm, etc.

[0097] If D4mm is greater than 110mm, the distance between the first center line L1 and the second center line L2 along the length of the core 1 will be too large, resulting in an increased lithium-ion transport path and a higher risk of lithium plating at the bending zone 100. If D4mm is less than 310mm, the distance between the first center line L1 and the second center line L2 along the length of the core 1 will be too small, resulting in excessive stress on the electrode 10 at the bending zone 100 and an increased risk of material loss at the bending zone 100. By ensuring that D4mm is greater than or equal to 110mm and less than or equal to 310mm, the risk of lithium plating and material loss at the bending zone 100 can be reduced.

[0098] In one possible implementation, the core 1 includes two pole pieces 10, each comprising a first pole piece and a second pole piece. The first and second pole pieces have opposite polarities, and the elongation at break of the first pole piece is less than that of the second pole piece. An insulating protective layer 20 is bonded to the first pole piece. This configuration, by bonding the insulating protective layer 20 to the first pole piece, improves the bending resistance of the first pole piece, making it less prone to breakage and thus reducing the risk of material loss from the core 1 at the bending zone 100.

[0099] In this configuration, the first electrode can be either a positive or a negative electrode. When the first electrode is a positive electrode, the second electrode is a negative electrode. When the first electrode is a negative electrode, the second electrode is a positive electrode.

[0100] In some examples, the first electrode is a positive electrode and the second electrode is a negative electrode. The current collector 11 of the first electrode includes aluminum, and the current collector 11 of the second electrode includes copper. The current collector 11 containing copper has a greater deformation capacity before tensile fracture than the current collector 11 containing aluminum, resulting in a lower elongation at break of the first electrode than that of the second electrode.

[0101] In one possible implementation, d1 satisfies: 1mm ≤ d1mm ≤ 10mm. The value of d1mm can be 1mm, 2mm, 5mm, 7mm, 9mm, or 10mm, etc.

[0102] If d1mm is greater than 10mm, the total size of the inactive material region 200 of the electrode 10 will be too large in the height direction of the core 1, resulting in a lower overall energy density of the battery. If d1mm is less than 1mm, the total size of the inactive material region 200 of the electrode 10 will be too small in the height direction of the core 1, making it easier for heat to be transferred to the active material layer 12 during the welding of the tabs 13 of the core 1, thus increasing the risk of material loss at the bending area 100 of the core 1. By ensuring that d1mm is greater than or equal to 1mm and less than or equal to 10mm, the overall energy density of the battery can be improved, and the risk of material loss at the bending area 100 of the core 1 can be reduced.

[0103] d2 satisfies: 70mm≤d2mm≤160mm. The value of d2mm can be 70mm, 80mm, 100mm, 110mm, 130mm, 150mm or 160mm, etc.

[0104] If d2mm is greater than 160mm, the electrode 10 will be too large in the height direction of the core 1, causing it to easily interfere with the battery casing 2. If d2mm is less than 70mm, the electrode 10 will be too small in the height direction of the core 1, resulting in lower energy density of the core 1. By ensuring d2mm is greater than or equal to 70mm and less than or equal to 160mm, interference between the electrode 10 and the battery casing 2 can be minimized, and the energy density of the core 1 can be improved.

[0105] M satisfies: 0.007 ≤ M ≤ 0.14. If M is greater than 0.14, the total size of the inactive material region 200 of the electrode 10 will be too large in the height direction of the core 1, resulting in a lower overall energy density of the battery. If M is less than 0.007, the total size of the inactive material region 200 of the electrode 10 will be too small in the height direction of the core 1, making it easier for heat to be transferred to the active material layer 12 during the welding of the tab 13 of the core 1. This increases the risk of material loss at the bending area 100 of the core 1 and makes it easier for lithium dendrites to pierce the electrode 10, increasing the risk of short circuit in the electrode 10. By ensuring that M is greater than or equal to 0.007 and less than or equal to 0.14, the overall energy density of the battery can be improved, the risk of material loss at the bending area 100 of the core 1 can be reduced, and the risk of short circuit in the electrode 10 can be reduced.

[0106] In this embodiment, the core 1 only needs to satisfy at least one of the parameters d1, d2 and M.

[0107] Figure 4 The dashed box represents the electrode 10, the solid box inside the dashed box represents the active material layer 12, and the part between the dashed box and the solid box is the inactive material region 200.

[0108] In one possible implementation, see Figure 4 In the height direction of the core 1, inactive material regions 200 are provided at both ends of the electrode 10, and d1 satisfies: 1.2mm≤d1mm≤10mm. The value of d1mm can be 1.2mm, 2mm, 5mm, 7mm, 9mm or 10mm, etc.

[0109] If d1mm is greater than 10mm, the sum of the sizes of the inactive material regions 200 at both ends of the electrode 10 will be too large in the height direction of the core 1, resulting in a lower overall energy density of the battery. If d1mm is less than 1.2mm, the sum of the sizes of the inactive material regions 200 at both ends of the electrode 10 will be too small in the height direction of the core 1, making it easier for heat to be transferred to the active material layer 12 during the welding of the tabs 13 of the core 1, thus increasing the risk of material loss at the bending area 100 of the core 1. By ensuring that d1mm is greater than or equal to 1.2mm and less than or equal to 10mm, the overall energy density of the battery can be improved, and the risk of material loss at the bending area 100 of the core 1 can be reduced.

[0110] Figure 5 The dashed box represents the electrode 10, the solid box inside the dashed box represents the active material layer 12, and the part between the dashed box and the solid box is the inactive material region 200.

[0111] In one possible implementation, see Figure 5 In the height direction of the core 1, an inactive material region 200 is provided at only one end of the electrode 10, and d1 satisfies: 1.1mm≤d1mm≤10mm. The value of d1mm can be 1.1mm, 2mm, 5mm, 7mm, 9mm or 10mm, etc.

[0112] If d1mm is greater than 10mm, the size of the inactive material region 200 at one end of the electrode 10 will be too large in the height direction of the core 1, resulting in a lower overall energy density of the battery. If d1mm is less than 1.1mm, the size of the inactive material region 200 at one end of the electrode 10 will be too small in the height direction of the core 1, making it easier for heat to be transferred to the active material layer 12 during the welding of the tab 13 of the core 1, thus increasing the risk of material loss at the bending area 100 of the core 1. By ensuring that d1mm is greater than or equal to 1.1mm and less than or equal to 10mm, the overall energy density of the battery can be improved, and the risk of material loss at the bending area 100 of the core 1 can be reduced.

[0113] Figure 6 The dashed box represents the electrode 10, the solid box inside the dashed box represents the active material layer 12, and the part between the dashed box and the solid box is the inactive material region 200.

[0114] In one possible implementation, see Figure 6In the height direction of the core 1, the end of the insulating protective layer 20 does not exceed the end of the electrode sheet 10. This arrangement reduces the amount of material used in the insulating protective layer 20, thereby lowering production costs.

[0115] In the height direction of the core 1, the distance between the end of the insulating protective layer 20 and the end of the electrode 10 is D5mm, where D5 satisfies: 1mm≤D5mm≤15mm. The value of D5mm can be 1mm, 2mm, 5mm, 7mm, 9mm, 10mm, or 15mm, etc.

[0116] If D5mm is greater than 15mm, the distance between the end of the insulating protective layer 20 and the end of the electrode 10 will be too large in the height direction of the core 1, making the insulating protective layer prone to detachment and increasing the risk of material loss at the bending zone. If D5mm is less than 1mm, the distance between the end of the insulating protective layer 20 and the end of the electrode 10 will be too small in the height direction of the core 1, resulting in a longer lithium-ion transport path and increasing the risk of lithium plating at the bending zone 100 of the core 1. By ensuring that D5mm is greater than or equal to 1mm and less than or equal to 15mm, the risk of material loss at the bending zone and the risk of lithium plating at the bending zone 100 of the core 1 can be reduced.

[0117] In one possible implementation, in the height direction of the core 1, at least one end of the insulating protective layer 20 extends beyond the end of the electrode 10, and the dimension of the end of the insulating protective layer 20 extending beyond the end of the electrode 10 is D6mm (see...). Figure 4 D6 satisfies: 0.1mm≤D6mm≤10mm. The value of D6 can be 0.1mm, 1mm, 2mm, 5mm, 7mm, 9mm or 10mm, etc.

[0118] If D6mm is greater than 10mm, the end of the insulating protective layer 20 will extend too far beyond the end of the electrode 10 in the height direction of the core 1. This makes the insulating protective layer 20 prone to accidental contact with components such as the electrode post, causing thermal shrinkage and detachment, thus increasing the risk of material loss from the core 1 at the bending area. If D6mm is less than 0.1mm, the extension of the insulating protective layer 20 beyond the electrode 10 will be too small in the height direction of the core 1, making it difficult to bond the insulating protective layer 20 to the inactive material area 200. By ensuring that D6mm is greater than or equal to 0.1mm and less than or equal to 10mm, the risk of material loss from the core at the bending area can be reduced, and the bonding of the insulating protective layer 20 to the inactive material area 200 can be facilitated.

[0119] Among them, see Figure 7The two adjacent insulating protective layers 20 are bonded together. This arrangement prevents the two insulating protective layers 20 from falling off the electrode sheet 10, thereby reducing the risk of material falling off the core 1 at the bending point.

[0120] In some examples, the bonding dimension of two adjacent insulating protective layers 20 in the height direction of the core 1 is D7mm, where D7 satisfies: 0.1mm≤D7mm≤9.8mm. The value of D7mm can be 0.1mm, 1mm, 2mm, 5mm, 7mm, 9mm or 9.8mm, etc.

[0121] If D7mm is greater than 9.8mm, the bonding size between two adjacent insulating protective layers 20 in the height direction of the core 1 will be too large, making it easy for the two adjacent insulating protective layers 20 to accidentally come into contact with components such as poles, causing thermal shrinkage and detachment, thus increasing the risk of material loss from the core 1 at the bending area. If D7mm is less than 0.1mm, the bonding size between two adjacent insulating protective layers 20 in the height direction of the core 1 will be too small, making it inconvenient to bond the two adjacent insulating protective layers 20 to the inactive material area 200. By ensuring that D7mm is greater than or equal to 0.1mm and less than or equal to 9.8mm, the risk of material loss from the core 1 at the bending area can be reduced, and the bonding between the insulating protective layers 20 and the inactive material area 200 can be facilitated.

[0122] In some examples, the electrode 10 has a first end 101 and a second end 102 in the height direction of the core 1. The first end 101 of the electrode 10 is provided with a tab 13 (see...). Figure 4 The inactive material region 200 is disposed at the first end 101 of the electrode sheet 10. In the height direction of the core 1, the size of the tab 13 is D8mm, where D8 is greater than D6. With this arrangement, in the height direction of the core 1, the tab 13 can extend beyond the insulating protective layer 20, thereby facilitating the welding of the tab 13 to the battery terminal.

[0123] In one possible implementation, the dimension of a single insulating protective layer 20 is D9mm in the winding direction of the electrode 10 (see...). Figure 4 The D9 value satisfies the condition: 10mm ≤ D9mm ≤ 30mm. The value of D9mm can be 10mm, 11mm, 12mm, 15mm, 20mm, 25mm, or 30mm, etc.

[0124] If D9mm is greater than 30mm, the size of a single insulating protective layer 20 will be too large in the winding direction of the electrode 10, leading to increased lithium-ion transport resistance and a higher risk of lithium deposition in the core 1 at the bending zone 100. If D9mm is less than 10mm, the size of a single insulating protective layer 20 will be too small along the winding direction of the core 1, resulting in poor adhesion of the insulating protective layer 20 and a higher risk of material loss in the core 1 at the bending zone 100. By ensuring that D9mm is greater than or equal to 10mm and less than or equal to 30mm, the risk of material loss and lithium deposition in the core 1 at the bending zone 100 can be reduced.

[0125] In the thickness direction of electrode 10, the dimension of insulating protective layer 20 is D10μm (see...). Figure 3 The value of D10 satisfies: 20μm≤D10μm≤100μm. The value of D10μm can be 20μm, 25μm, 30μm, 50μm, 70μm, 90μm or 100μm, etc.

[0126] If D10μm is greater than 100μm, the insulating protective layer 20 will be too large in the thickness direction of the electrode 10, leading to increased lithium-ion transport resistance and a higher risk of lithium plating at the bending zone 100 of the core 1. If D10μm is less than 100μm, the insulating protective layer 20 will be too small in the thickness direction of the electrode 10, resulting in poor adhesion of the insulating protective layer 20 and a higher risk of material loss at the bending zone 100 of the core 1. By ensuring that D10μm is greater than or equal to 20μm and less than or equal to 100μm, the risk of material loss and lithium plating at the bending zone 100 of the core 1 can be reduced.

[0127] It should be noted that in this embodiment, the core 1 can only satisfy D9mm greater than or equal to 10mm and less than or equal to 30mm, or it can only satisfy D10μm greater than or equal to 20μm and less than or equal to 100μm, or it can simultaneously satisfy D9mm greater than or equal to 10mm and less than or equal to 30mm, D10μm greater than or equal to 20μm and less than or equal to 100μm.

[0128] In one possible implementation, an insulating protective layer 20 is provided within the first five turns of the core 1 closest to the first end 1010 of the electrode 10. This arrangement addresses the issue of stress concentration and a large radius of curvature in the inner turns of the electrode 10 near its first end 1010, which poses a significant risk of material loss. Therefore, the insulating protective layer 20 within the first five turns closest to the first end 1010 of the electrode 10 protects the active material layer 12 of the electrode 10, reducing the risk of material loss.

[0129] The starting end of the winding of electrode 10 is the first end 1010 of electrode 10.

[0130] One turn of the electrode 10 has an initial end and a tail end along the winding direction of the core 1. The initial end and the tail end are located in the straight region 1000. One turn of the electrode 10 passes through two bending regions 2000 of the core 1. The initial end and the tail end overlap in the thickness direction of the core 1.

[0131] For example, the first end of the electrode 10 can be used as the initial end of the first turn of the electrode 10 in the core 1. The first end 1010 of the electrode 10 is wound 5 turns, which is the 5 turns of the electrode 10 in the core 1 closest to the first end of the electrode 10.

[0132] Secondly, see Figure 8 This application provides a battery, including a housing 2 and a winding core 1. The housing 2 has a receiving cavity, and the winding core 1 is placed in the receiving cavity.

[0133] The core 1 in this embodiment has the same structure as the core 1 provided in any of the above embodiments, and can bring the same or similar technical effects. It will not be described in detail here, but can be referred to the description of the above embodiments.

[0134] The housing 2 is a component used to provide a receiving space to house the winding core 1 and other components and isolate them from the outside environment. The housing 2 includes a body and a cover plate with an opening and a receiving cavity at at least one end. The opening of the body can be closed by the cover plate to seal and isolate the internal environment of the battery from the external environment.

[0135] The material of the shell 2 includes, but is not limited to, metals or alloys such as copper, iron, aluminum, stainless steel, aluminum alloy, titanium, and magnesium.

[0136] In the height direction of the core 1, the housing 2 has a first surface 201 and a second surface 202. The first surface 201 is provided with a liquid injection hole 3, and the end of the electrode 10 of the core 1 near the liquid injection hole 3 is provided with an inactive material region 200, and the insulating protective layer 20 of the core 1 is bonded to the inactive material region 200.

[0137] The height direction of the battery is the same as that of the core 1. In the height direction of the battery, the distance between the injection hole 3 and the inactive material area 200 is greater than or equal to 0.5 mm and less than or equal to 15 mm. The distance between the injection hole 3 and the inactive material area 200 in the height direction of the battery can be 0.5 mm, 1 mm, 5 mm, 10 mm, or 15 mm, etc.

[0138] If the distance between the injection hole 3 and the inactive material area 200 is greater than 15mm in the height direction of the battery, the overall energy density of the battery will be low due to the excessive distance between them. If the distance between the injection hole 3 and the inactive material area 200 is less than 0.5mm in the height direction of the battery, the scouring force of the electrolyte during injection on the insulating protective layer 20 will be greater, making it easier for the insulating protective layer 20 to detach, thus increasing the risk of material loss from the core 1 at the bending area. By ensuring that the distance between the injection hole 3 and the inactive material area 200 is greater than or equal to 0.5mm and less than or equal to 15mm in the height direction of the battery, the overall energy density of the battery can be improved, and the risk of lithium plating in the core 1 at the bending area 100 can be reduced.

[0139] In this embodiment, the method for measuring the elongation at break is as follows: the current collector 11 of the electrode 10 is made of metal foil, and the method for testing the elongation at break of the metal foil is in accordance with GB / T29847-2025.

[0140] Methods for controlling the elongation at break include: adjusting the material of the current collector 11 in the electrode 10, such as pure copper, pure aluminum, or the proportion of each doping element in the alloy, can all adjust the elongation at break of the current collector 11 in the electrode 10. For example, doping an aluminum electrode with iron is beneficial to improving the elongation at break of the electrode 10. In addition, the elongation at break of the current collector 11 in the electrode 10 can also be changed by altering its thickness or by using a composite current collector.

[0141] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0142] The preparation of the example battery and the comparative battery includes the following steps:

[0143] Methods for measuring dimensions, thickness, distance, and area:

[0144] The battery is discharged to its lower limit voltage at 0.33C. Then, the battery is disassembled, and the electrode 10 with the insulating protective layer 20 is removed. The insulating protective layer 20 and the electrode 10 are then removed. Dimensions, thickness, and distances can be measured using a micrometer, calipers, or scanning electron microscope, and the area can be calculated from these dimensions. When the positive electrode active material of the battery is lithium iron phosphate, the lower limit voltage is 2.5V; when the positive electrode active material is lithium nickel cobalt manganese oxide, the lower limit voltage is 2.75V.

[0145] Battery manufacturing

[0146] (1) Preparation of the positive electrode:

[0147] The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., PVDF) are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet is obtained.

[0148] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98): (4~1): (4~1).

[0149] (2) Preparation of negative electrode:

[0150] The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (SBR)) are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained.

[0151] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0152] (3) Preparation of electrolyte:

[0153] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0154] (4) Preparation of the diaphragm:

[0155] Polyethylene film is selected as the diaphragm.

[0156] (5) Preparation of lithium-ion batteries:

[0157] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence and wound to form a bare battery core 1. Before stacking, an insulating protective layer 20 is attached to the position corresponding to the bending area 100 of the core 1. The bare core 1 is placed in the battery casing 2, which is a square shell. The battery is dried, injected with electrolyte, and then packaged, left to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0158] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate.

[0159] The negative electrode active material can be selected from one or more of the following negative electrode active main materials: artificial graphite, natural graphite, silicon carbide, silicon oxide, lithium titanate, etc.

[0160] The testing method is as follows:

[0161] Test Method 1, Battery Capacity Retention Rate:

[0162] Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The parameters of the core 1 in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. All other structures are identical. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, and then charged with a constant voltage of 0.33C until the current dropped to 0.05C. After standing for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This process was repeated three times to obtain the third discharge capacity Q1, which was taken as the fixed capacity.

[0163] The lithium-ion battery is charged at room temperature (25℃) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage of 0.33C until the current drops to 0.05C. After resting for 5 minutes, the battery is discharged with a constant current of 0.33C to the lower limit voltage. This constitutes one cycle. After n cycles, the battery discharge capacity Qn of the nth cycle is recorded. The battery capacity retention rate is calculated using the formula "Battery capacity retention rate = (Qn / Q1) × 100%". The number of cycles n when the capacity retention rate first falls below 80% is recorded as the number of cycles for that battery. If n is less than 1200, the battery capacity retention rate is unqualified; if n is greater than or equal to 1200 and less than 1400, the battery capacity retention rate is qualified; if n is greater than or equal to 1400, the battery capacity retention rate is good. That is, if n is greater than or equal to 1200, the battery capacity retention rate is qualified.

[0164] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0165] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0166] Test method 2, volumetric energy density:

[0167] According to the above battery preparation method, for each embodiment and comparative example, corresponding lithium-ion batteries were prepared. The parameters of the insulation protection layer and the winding core 1 in the lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1. The maximum length l (the dimension of the battery in the length direction of the winding core 1), maximum width d (the dimension of the battery in the height direction of the winding core 1), and maximum thickness h (the dimension of the battery in the thickness direction of the winding core 1) of the battery were controlled to be 246 mm, 40 mm, and 115 mm, respectively. Except for these, the remaining structures were the same. According to the formula V = l×d×h, the volume of the battery was calculated, with the unit of liter (L). The battery was placed in an incubator at 25°C, and the following operations were performed on the test object: Charge at 0.33C to the upper limit voltage, and then charge at a constant voltage until the cut-off current of 0.05C; let it stand for 30 minutes, and discharge at 0.33C to the lower limit voltage of discharge; Repeat the above operations for 3 cycles, and use the discharge capacity of the third cycle as the fixed capacity of the battery, denoted as W, with the unit of (Ah). According to the formula volume energy density = (W×N) / V, the volume energy density of the battery was calculated, with the unit of Wh / L, where N is the average working voltage of the battery. If the volume energy density of the battery is between 420 Wh / L and 470 Wh / L, the volume energy density is qualified; if it is greater than 470 Wh / L, the volume energy density is good. That is, if the volume energy density of the battery is greater than or equal to 420 Wh / L, the volume energy density is qualified; if the volume energy density of the battery is less than 420 Wh / L, the volume energy density is unqualified.

[0168] If the positive electrode material is a ternary material (lithium nickel cobalt manganate), the upper limit voltage is 4.25V, the lower limit voltage is 2.5V, and the average working voltage is 3.7V. If the positive electrode material is lithium iron phosphate, the upper limit voltage is 3.65V, the lower limit voltage is 2.5V, and the average working voltage is 3.3V.

[0169] In this test, the positive electrode active material of the battery is selected from lithium nickel cobalt manganese ternary LiNi 0.6 Co 0.2 Mn 0.2 O2 as an example, the mass ratio of the positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode activity is selected from artificial graphite, and the ratio of the negative electrode active material: conductive agent: thickening agent: binder satisfies 95:2:1:2.

[0170] Table 1

[0171]

[0172] Compared to Comparative Example 1 and Comparative Example 4, if M, N and K satisfy: 0.016≤(M×K) / N, the battery capacity retention rate is qualified. Limiting M, N and K can ensure the volumetric energy density of the battery while improving the battery capacity retention rate. That is, it can reduce the risk of material loss of the core 1 at the bending area 100, and make it less likely for lithium dendrites to pierce the electrode 10, thereby reducing the risk of short circuit of the electrode 10.

[0173] Compared to Comparative Examples 2 and 3, if M, N, and K satisfy (M×K) / N≤2.3, the volumetric energy density of the battery is qualified. Limiting M, N, and K can improve the volumetric energy density, while the battery capacity retention rate can also meet the requirements.

[0174] Thirdly, embodiments of this application provide an electrical device including the battery of the second aspect.

[0175] The battery in this embodiment has the same structure as the battery provided in any of the above embodiments and can bring the same or similar technical effects. It will not be described in detail here. For details, please refer to the description of the above embodiments.

[0176] Batteries can serve as the operating power source for electrical devices, or as the driving power source for electrical devices, replacing or partially replacing fuel or natural gas to provide driving power for vehicles.

[0177] Electrical devices include energy storage equipment, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and devices in the aerospace field.

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A type of winding core, characterized in that, include: An electrode sheet, the electrode sheet comprising a current collector and an active material layer coated on at least one surface of the current collector, the electrode sheet being bent to form a bending region, and at least one end of the electrode sheet comprising an inactive material region in the height direction of the winding core; An insulating protective layer is bonded to the surface of the active material layer, the insulating protective layer is at least disposed in the bending area, and the insulating protective layer is partially bonded to the inactive material area; In the height direction of the core, the total size of the inactive material region is d1mm, the size of the electrode is d2mm, and the ratio of d1 to d2 is M; In the thickness direction of the electrode, the total size of the active material layer on the electrode is D1μm, the size of the electrode is D2μm, and the ratio of D1 to D2 is N; The elongation at break of the current collector is K%. The M, N, and K satisfy the condition: 0.016 ≤ (M × K) / N ≤ 2.

3.

2. The winding core according to claim 1, characterized in that, The K satisfies: 2% ≤ K % ≤ 12%; and / or, in the thickness direction of the electrode, the size of the current collector is D3 μm, where D3 satisfies: 4 μm ≤ D3 μm ≤ 18 μm.

3. The winding core according to claim 1, characterized in that, In the thickness direction of the electrode, there are active material layers on both sides of the current collector, and the insulating protective layer is respectively bonded to the active material layers on both sides of the current collector.

4. The winding core according to claim 1, characterized in that, It includes at least two insulating protective layers, the at least two insulating protective layers including a first insulating protective layer and a second insulating protective layer, the first insulating protective layer having a first center line, the second insulating protective layer having a second center line, the first center line and the second center line being located on both sides of the winding core in the length direction of the winding core, the distance between the first center line and the second center line being D4mm, wherein D4 satisfies: 110mm≤D4mm≤310mm.

5. The winding core according to claim 1, characterized in that, The device includes two electrodes, one first electrode and the other second electrode, which have opposite polarities. The first electrode has a lower elongation at break than the second electrode. The insulating protective layer is bonded to the first electrode.

6. The winding core according to claim 5, characterized in that, The current collector of the first electrode comprises aluminum, and the current collector of the second electrode comprises copper.

7. The winding core according to any one of claims 1-6, characterized in that, The d1 satisfies: 1mm≤d1mm≤10mm; and / or, the d2 satisfies: 70mm≤d2mm≤160mm; and / or, the M satisfies: 0.007≤M≤0.

14.

8. The winding core according to any one of claims 1-6, characterized in that, In the height direction of the core, the inactive material region is provided at only one end of the electrode, and d1 satisfies: 1.1mm≤d1mm≤10mm.

9. The winding core according to any one of claims 1-6, characterized in that, In the height direction of the core, the inactive material region is provided at both ends of the electrode, and d1 satisfies: 1.2mm≤d1mm≤10mm.

10. The winding core according to any one of claims 1-6, characterized in that, In the height direction of the winding core, the end of the insulating protective layer does not exceed the end of the electrode sheet.

11. The winding core according to claim 10, characterized in that, In the height direction of the core, the distance between the end of the insulating protective layer and the end of the electrode sheet is D5mm, where D5 satisfies: 1mm≤D5mm≤15mm.

12. The winding core according to any one of claims 1-6, characterized in that, In the height direction of the core, at least one end of the insulating protective layer extends beyond the end of the electrode sheet, and the dimension by which the end of the insulating protective layer extends beyond the end of the electrode sheet is D6mm, wherein D6 satisfies: 0.1mm≤D6mm≤10mm.

13. The winding core according to claim 12, characterized in that, The two adjacent insulating protective layers are bonded together, and the bonding dimension of the two adjacent insulating protective layers in the height direction of the core is D7mm, wherein D7 satisfies: 0.1mm≤D7mm≤9.8mm.

14. The winding core according to claim 12, characterized in that, The first end of the electrode sheet is provided with an electrode tab, and the inactive material region is provided at the first end of the electrode sheet. In the height direction of the core, the size of the electrode tab is D8mm, where D8 is greater than D6.

15. The winding core according to any one of claims 1-6, characterized in that, In the winding direction of the electrode sheet, the size of a single insulating protective layer is D9mm, where D9 satisfies: 10mm≤D9mm≤30mm; and / or, in the thickness direction of the electrode sheet, the size of the insulating protective layer is D10μm, where D10 satisfies: 20μm≤D10μm≤100μm.

16. The winding core according to any one of claims 1-6, characterized in that, The electrode sheet has the insulating protective layer disposed within the first 5 turns of the winding core closest to the first end of the electrode sheet.

17. The winding core according to any one of claims 1-6, characterized in that, The M, N, and K satisfy the condition: 0.035 ≤ (M × K) / N ≤ 1.

605.

18. A battery, characterized in that, It includes a housing and a winding core as described in any one of claims 1-17, wherein the housing has a receiving cavity and the winding core is placed in the receiving cavity.

19. The battery according to claim 18, characterized in that, The first surface of the housing is provided with a liquid injection hole, and the end of the electrode of the core near the liquid injection hole is provided with an inactive material area, and the insulating protective layer of the core is bonded to the inactive material area.

20. The battery according to claim 19, characterized in that, In the height direction of the battery, the distance between the injection hole and the inactive material area is greater than or equal to 0.5 mm and less than or equal to 15 mm.

21. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 18-20.

Images