Battery cell, battery device, and electric device

Abstract

The application discloses a battery monomer, a battery device and a power utilization equipment. The battery monomer comprises an electrode assembly, the electrode assembly comprises one negative electrode wire and N positive electrode wires, N is a positive integer greater than or equal to 2; the positive electrode wire is spirally wound on the outer periphery of the negative electrode wire, and a diaphragm is arranged between the positive electrode wire and the negative electrode wire. By adopting the asymmetric multi-strand counter-twisted structure, cooperating with the negative electrode silicon-carbon / graphite composite system and the specific active material loading design, the problems of low capacity of the traditional symmetric counter-twisted battery and easy cracking of thick coating are solved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical appliance. Background Technology

[0002] Fibrous lithium-ion batteries, with their flexibility, weavability, and lightweight characteristics, have broad application prospects in wearable devices, flexible electronics, and smart fabrics. Currently, the mainstream fiber lithium-ion battery cells are mainly divided into two categories: one is the traditional two-strand twisted structure, in which a single positive electrode wire and a single negative electrode wire are directly twisted together.

[0003] Two-strand twisted fiber batteries are the most widely used due to their simple manufacturing process and excellent flexibility. However, this structure has significant drawbacks. In traditional twisted-strand structures with a single positive and a single negative electrode wire, the total amount of active material in the electrode is limited. Capacity can only be increased by thickening the coating of the single positive and negative electrode wires. However, excessively thick coatings severely hinder ion transport, significantly deteriorating the battery's rate performance and cycle stability. This results in a common problem of low capacity per unit length and insufficient energy density in such batteries. Summary of the Invention

[0004] The main purpose of this application is to provide a single battery cell to solve the problem that the electrode active material of the current single positive electrode wire and single negative electrode wire twisted together structure is limited. Increasing the thickness of the active material to improve capacity will hinder ion transport, which will greatly deteriorate the rate performance and cycle stability of the battery. As a result, such batteries generally have the problems of low capacity per unit length and insufficient energy density.

[0005] To achieve the above objectives, a first aspect of this application provides a battery cell comprising: An electrode assembly includes a separator, a negative electrode wire, and N positive electrode wires, where N is a positive integer greater than 2. The outer peripheral surface of at least one of the positive and negative electrode wires is covered by the separator, and the N positive electrode wires are spirally wound around the same negative electrode wire.

[0006] This application employs a structure in which multiple positive electrode wires are spirally wound around a single negative electrode wire. Compared to the traditional single-positive-single-negative twisted structure, this increases the ion transport interface between the positive and negative electrode wires, reducing the ion transport obstruction problem caused by the traditional method of increasing capacity through thicker electrode coatings. Furthermore, the electrode active materials can fully participate in the electrochemical reaction, improving the rate performance and cycle stability of the battery cell. Compared to a battery structure formed by twisting a single positive electrode wire and a single negative electrode wire together to achieve the same capacity through six parallel connections, the volume of the battery cell in this application is 1 / 3 smaller than that of a battery structure with six parallel single-positive-negative electrode twisted wires. This results in a smaller volume for the same capacity, meaning a higher volumetric energy density, while maintaining the flexibility of the fiber battery cell.

[0007] In some embodiments, N≤6.

[0008] In some embodiments, the negative electrode wire includes a negative electrode active material layer, which includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The mass percentages of the negative electrode active material, negative electrode binder and negative electrode conductive agent are (89%~92%): (4%~6%): (3%~5%).

[0009] In some embodiments, the negative electrode active material includes silicon carbon and graphite, with the mass percentage of silicon carbon and graphite being (11%–14%): (86%–89%).

[0010] In some embodiments, the positive electrode wire includes a positive electrode active material layer, which includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The mass percentages of the positive electrode active material, positive electrode binder and positive electrode conductive agent are (89%~92%): (4%~6%): (3%~5%).

[0011] In some embodiments, the negative electrode wire includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the mass of the negative electrode active material ranges from 370 mg / m to 400 mg / m; and / or The positive electrode wire includes a positive electrode active material layer, which contains positive electrode active material. The mass of the positive electrode active material in each positive electrode wire ranges from 175 mg / m to 180 mg / m.

[0012] In some embodiments, the diameter of the positive electrode wire ranges from 0.4 mm to 0.48 mm; and / or, the diameter of the negative electrode wire ranges from 0.7 mm to 0.75 mm.

[0013] In some embodiments, the diameter of the positive current collector 12 ranges from 0.2 mm to 0.22 mm, and the diameter of the negative current collector 22 ranges from 0.25 mm to 0.3 mm.

[0014] In some embodiments, the pitch of each positive electrode wire ranges from 10mm to 20mm.

[0015] In some embodiments, the ratio of the reversible areal capacity of the negative electrode wire to the reversible areal capacity of the positive electrode wire ranges from 1.05 to 1.1.

[0016] In some embodiments, the battery cell further includes an encapsulation layer covering the outer peripheral surface of the electrode assembly; and / or, a separator wrapping the outer peripheral surface of the negative electrode wire.

[0017] A second aspect of this application provides a battery device comprising at least one battery cell as described in the first aspect.

[0018] A third aspect of this application provides an electrical device including the battery device described in the second aspect, the battery device being used to provide electrical energy to the electrical device. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This application provides a partial structural schematic diagram of an electrode assembly in a battery cell for some embodiments; Figure 2 This is a cross-sectional view of a battery cell through the negative electrode wire, provided for some embodiments of this application.

[0020] The reference numerals in the accompanying drawings for the specific implementation methods are as follows: 100. Electrode assembly; 10. Positive electrode wire; 11. Positive electrode active material layer; 12. Positive current collector; 20. Negative electrode wire; 21. Negative electrode active material layer; 22. Negative current collector; 30. Separator; 200. Encapsulation layer. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0025] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linked," and "socketing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] The following is combined Figure 1 and Figure 2 The following explanation will be based on a single battery cell from this application.

[0027] This application proposes a battery cell including an electrode assembly 100. The electrode assembly 100 includes a separator 30, a negative electrode wire 20, and N positive electrode wires 10, where N is a positive integer greater than 2. The outer peripheral surface of at least one of the positive electrode wires 10 and the negative electrode wires 20 is covered by the separator 30, and the N positive electrode wires 10 are spirally wound around the same negative electrode wire 20.

[0028] Each positive electrode wire 10 has a positive tab connected to its end, and each negative electrode wire 20 has a negative tab connected to its end. Positive tabs of the same polarity can be electrically connected to each other, and negative tabs of the same polarity can be electrically connected to each other. The positive and negative tabs are arranged alternately. The positive and negative tabs can be located at the same end of the electrode assembly 100 or at opposite ends.

[0029] The positive electrode wire 10 includes a positive current collector 12 and a positive active material layer 11 coated on the outer periphery of the positive current collector 12; the negative electrode wire 20 includes a negative current collector 22 and a negative active material layer 21 coated on the outer periphery of the negative current collector 22. The positive current collector 12 can be an aluminum wire or a composite conductive wire formed by combining aluminum and polymer materials, such as a metallized polymer composite wire with a core layer of polymer materials such as polyethylene terephthalate (PET), polypropylene (PP), or polyimide (PI) and an aluminum or aluminum alloy conductive layer on its outer periphery. The negative current collector 22 can be a copper wire or a composite conductive wire formed by combining copper and polymer materials, such as a metallized polymer composite wire with a core layer of polymer materials such as PET, PP, or PI and a copper or copper alloy conductive layer on its outer periphery.

[0030] The diaphragm 30 may be a lithium-ion permeable porous insulating film, the material of which includes, but is not limited to, polyethylene (PE), polypropylene (PP), PE / PP composite microporous membrane, polyimide (PI), polyvinylidene fluoride (PVDF) or copolymers thereof (such as PVDF). The membrane 30 is made of HFP (hydrophobic polymer), polyethylene terephthalate (PET) nonwoven fabric or microporous membrane, polyamide (PA) nonwoven fabric, or a modified porous membrane 30 coated with inorganic ceramic particles such as alumina, silica, or titanium dioxide. The membrane 30 is wrapped around the outer peripheral surface of the positive electrode wire 10 and / or the negative electrode wire 20 in a tubular or strip shape, so that the positive electrode wire 10 and the negative electrode wire 20 are mutually insulated, while allowing lithium ions to pass freely.

[0031] The diaphragm 30 is wrapped around the outer surface of the positive electrode wire 10 and / or the negative electrode wire 20 in a tubular, sleeve-like or longitudinally wrapped manner. When at least one of the positive electrode wire 10 and the negative electrode wire 20 is wrapped by the diaphragm 30, electrical insulation is achieved between the two through the diaphragm 30 to prevent short circuit.

[0032] This application employs a structure in which multiple positive electrode wires 10 are spirally wound around a single negative electrode wire 20. Compared to the traditional single positive and single negative twisted structure, the ion transport interface between the positive and negative electrode wires is increased, reducing the ion transport obstruction problem caused by the traditional solution of increasing capacity by thickening the electrode coating. Furthermore, the electrode active material can fully participate in the electrochemical reaction, improving the rate performance and cycle stability of the battery cell. Compared to the battery structure formed by twisting a single positive electrode wire 10 and a single negative electrode wire 20 together to achieve the same capacity through six parallel connections, the volume of the battery cell in this application is 1 / 3 smaller than that of the battery structure with six parallel single positive and negative electrode twisted wires. It has a smaller volume for the same capacity, i.e., a higher volumetric energy density, and can maintain the flexibility of the fiber battery cell.

[0033] In some embodiments, the diameter of the positive current collector 12 ranges from 0.2mm to 0.22mm, and the diameter of the negative current collector 22 ranges from 0.25mm to 0.3mm. By limiting the diameter of the positive current collector 12 to 0.2mm to 0.22mm and the diameter of the negative current collector 22 to 0.25mm to 0.3mm, a single battery cell is formed into a fine wire structure. This effectively reduces the overall bending stiffness of the battery, allowing it to bend freely like ordinary sewing thread, greatly improving its adaptability and wearing comfort in applications such as smart clothing and biomedical devices.

[0034] In some embodiments, N≤6, that is, N can take any integer between 2 and 6.

[0035] If the number of positive electrode wires 10 is too large (greater than 6), increasing the thickness of the negative electrode active material layer 21 of a single negative electrode wire 20 to match the positive electrode capacity would result in an excessively thick negative electrode active material layer 21. This would increase the ion transport path, limiting the charge and discharge rate of the battery cell, and would also lead to powder shedding, which would be difficult to achieve in the coating process. Therefore, the value of N is set to less than or equal to 6.

[0036] In some embodiments, the negative electrode wire 20 includes a negative electrode active material layer 21, which includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The mass percentages of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are (89%–92%): (4%–6%): (3%–5%).

[0037] The materials used for negative electrode active materials include one or more of graphite, silicon carbide, and alloys.

[0038] The negative electrode active material can be selected from one or more lithium-intercalable materials, including but not limited to: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-carbon composites (Si / C), and silicon-oxygen composites (SiO2). x / C), Lithium titanate (Li4Ti5O) 12 LTO, tin-based alloy or tin oxide anode materials.

[0039] The binder is typically selected from sodium carboxymethyl cellulose (CMC) and styrene. Aqueous system of butadiene rubber (SBR); conductive agent can be selected from superconducting carbon, carbon nanotubes or graphene.

[0040] Setting the mass percentage of the negative electrode active material in the high range of 89%–92% maximizes the reversible lithium intercalation capacity of the negative electrode, thereby improving the battery's initial efficiency and overall energy density. If the proportion of the negative electrode active material is too high (>92%), although the initial capacity is slightly improved, the interfacial bonding force between the active material layer and the current collector is significantly reduced due to the decrease in the absolute amount of binder and conductive agent. Furthermore, it cannot effectively buffer the volume expansion stress during cycling, easily leading to powdering or cracking of the active material layer after bending or long cycling. To address the volume expansion effect of the negative electrode material during lithium intercalation, controlling the binder proportion within the range of 4%–6% not only provides the necessary bonding force but also effectively suppresses the radial expansion and deformation of the negative electrode wire 20 during charging and discharging, preventing the spiral winding structure from loosening or the separator from being punctured. If the binder proportion is too low (<4%), the negative electrode wire 20 is prone to pulverization; if the proportion is too high (>6%), it will significantly increase the electrode internal resistance and reduce the energy density. Since the negative electrode wire 20 of this application cannot be coated using a roll forming process, the addition of the conductive agent can also improve the rheological properties of the slurry to a certain extent, and help to uniformly coat the active material layer. This ratio range avoids the dilution of the active material ratio and the decrease in coating density caused by excessive conductive agent (>5%), thereby improving the volumetric energy density of the battery cell.

[0041] In some embodiments, the diameter of the positive electrode wire 10 ranges from 0.4 mm to 0.48 mm; and / or, the diameter of the negative electrode wire 20 ranges from 0.7 mm to 0.75 mm.

[0042] This allows for the production of thinner diameters for the positive electrode wire 10 and the negative electrode wire 20, thereby reducing the overall diameter of the battery cell. This facilitates the production of various shapes for the battery cell through weaving and other methods, making it easier to wear and supply power, and thus improving the applicability of the battery cell in different scenarios.

[0043] In some embodiments, the negative electrode active material includes silicon carbon and graphite, wherein the mass percentage of silicon carbon and graphite is (11% to 14%): (86% to 89%).

[0044] The nominal specific capacity of silicon-carbon is 1790 mAh / g, and that of graphite is 340 mAh / g.

[0045] The introduction of silicon-carbon significantly improves the overall reversible specific capacity of the negative electrode, thereby enhancing the capacity of the battery cell. Compared to traditional pure graphite negative electrode active materials, the addition of silicon-carbon in this proportion allows the negative electrode wire 20 to be made thinner to achieve the same capacity. This enables multiple positive electrode wires 10 to work in conjunction with a single negative electrode wire 20 to achieve a higher capacity. In other words, the diameter range of the positive electrode wire 10 and the negative electrode wire 20 can be used to give the fiber battery cell both high capacity and a certain degree of flexibility, making it easy to weave and shape into various forms for easy wear and power supply.

[0046] In some embodiments, the positive electrode wire 10 includes a positive electrode active material layer 11, which includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The mass percentages of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are (89%–92%): (4%–6%): (3%–5%).

[0047] The positive electrode active material can be selected from one or more combinations of lithium transition metal oxides, including but not limited to: lithium cobalt oxide (LiCoO2, LCO), lithium manganese oxide (such as spinel-type LiMn2O4, LMO), lithium nickel cobalt manganese oxide ternary materials (LiNi x Co y Mn 1-x-y O2, NCM, such as NCM111, NCM523, NCM622, NCM811, lithium nickel cobalt aluminum oxide (LiNi 0.8 Co 0.15 Al 0.05 O2, NCA), lithium iron phosphate (LiFePO4, LFP), lithium nickel manganese spinel (LiNi 0.5 Mn 1.5 O4).

[0048] In LiNi x Co y Mn 1-x-y In O2 materials, 0 < x ≤ 0.9, 0 < y ≤ 0.9, and x + y < 1; typically, x can take values ​​from 0.3 to 0.8, y can take values ​​from 0.1 to 0.3, and z = 1. x y can be taken as 0.1 to 0.4.

[0049] The binder can be selected from polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), and styrene. Butadiene rubber (SBR), etc.; the conductive agent can be selected from one or more of acetylene black, superconducting carbon (Super P), carbon nanotubes (CNT) or graphene.

[0050] Setting the mass percentage of the positive electrode active material in the high range of 89%–92% ensures that the electrode wire can carry a sufficient amount of electrochemical reactants per unit length, thereby effectively improving the mass energy density and capacity of the battery cell. If the active material percentage is too low (<89%), although the electrode flexibility may be improved, it will lead to a significant decrease in battery capacity, failing to meet usage requirements. Since the electrode wire in this application cannot be densified by planar rolling, the bonding force between the active material layer and the current collector mainly depends on the adhesive. Controlling the adhesive percentage at 4%–6% provides sufficient interfacial adhesion to prevent powder shedding or peeling of the active material layer during spiral winding or bending, and also reduces ion transport obstruction and impedance surge caused by excessive adhesive (>6%). Controlling the conductive agent percentage at 3%–5% enables the construction of effective electron transport channels between the active material particles. An appropriate amount of conductive agent can significantly reduce electrode polarization and improve the rate performance and low-temperature performance of the battery. If the proportion of conductive agent is too low (<3%), it will lead to poor electron conduction path and excessive internal resistance. If the proportion is too high (>5%), it will occupy the space of active material, reduce the capacity of the battery cell, and increase the material cost.

[0051] In some embodiments, the negative electrode wire 20 includes a negative electrode active material layer 21, which includes a negative electrode active material, and the mass of the negative electrode active material ranges from 370 mg / m to 400 mg / m. And / or, the positive electrode wire 10 includes a positive electrode active material layer 11, which includes a positive electrode active material, and the mass of the positive electrode active material in each positive electrode wire 10 ranges from 175 mg / m to 180 mg / m.

[0052] In lithium-ion batteries, to ensure sufficient lithium insertion into the negative electrode and avoid lithium dendrite formation during the first charge-discharge cycle, the reversible capacity provided by the negative electrode typically needs to be slightly higher than the amount of lithium that can be extracted from the positive electrode (i.e., negative-to-positive electrode capacity ratio > 1). Since both the negative electrode wire 20 and the positive electrode wire 10 in this application are wire-coated without rolling, their capacity is primarily determined by the load per unit length of the active material. Setting the mass of the negative electrode active material to 370 mg / m to 400 mg / m, combined with the mass of the positive electrode active material at 175 mg / m to 180 mg / m, allows the battery cell to operate within a safe and reasonable negative-to-positive electrode capacity ratio range, ensuring cycle safety without unnecessary waste of inactive mass due to excessive negative electrode loading. Excessive thickness of the negative electrode active material layer 21 increases the risk of drying shrinkage stress and coating peeling during bending. By controlling the content of the negative electrode active material at 370mg / m to 400mg / m, the negative electrode wire 20 can maintain good flexibility and coating bonding strength while meeting the capacity matching requirements, and adapt to the requirements of subsequent spiral winding and fiber bending.

[0053] In some embodiments, the negative electrode binder includes sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR), and the mass ratio of CMC to SBR is 1:2.5.

[0054] In some embodiments, the pitch of each positive electrode wire ranges from 10mm to 20mm.

[0055] As an example, all positive electrode wires have the same pitch.

[0056] If the pitch of the positive electrode wire 10 is too small, the stress generated by the spiral winding will be too large, which will easily cause the active material on the coating surface to fall off. If the pitch is too large, the wire will not be wound tightly, resulting in insufficient contact between the positive and negative electrode wires, which will have an adverse effect on the performance of the battery cell. Therefore, the pitch of both the positive electrode wire 10 and the negative electrode wire 20 is set to a range of 10mm-20mm.

[0057] In some embodiments, the ratio (NP ratio) of the reversible surface capacity of the negative electrode wire 20 to the reversible surface capacity of the positive electrode wire 10 ranges from 1.05 to 1.1.

[0058] Table 1 shows the comparative experimental data of the NP ratio of the battery cells when N=6 in this application. Table 1

[0059] As can be seen from Table 1, when N=6 in this application, the battery cells used for comparison in this group are 20cm test sample batteries, with a sample size of 4 cells for each specification, and the data are averaged.

[0060] When the NP ratio is below or above the range of 1.05 to 1.15, the capacity performance of the battery cells will be directly affected, including specific capacity, discharge capacity, and battery initial efficiency.

[0061] When the NP ratio is below 0.9, the battery's initial efficiency decreases by about 3%, capacity decreases by about 5%, and specific capacity decreases by about 10%.

[0062] When the NP ratio is between 1.3 and 1.5, the battery's initial efficiency decreases by about 5%, its capacity decreases by about 7%, and its specific capacity decreases by about 10%.

[0063] The NP ratio can be set to a range of 1.05 to 1.15, which is also applicable to any value of N from 2 to 5.

[0064] The above experimental comparisons show that when the NP ratio is below 0.9: the battery's initial efficiency decreases by about 3%; capacity decreases by about 5%; and specific capacity decreases by about 10%. When the NP ratio is between 1.3 and 1.5, the battery's initial efficiency decreases by about 5%; capacity decreases by about 7%; and specific capacity decreases by about 10%. Setting the NP ratio within the range of 1.05 to 1.15 can improve the specific capacity (also called specific mass capacity, which refers to the electrical capacity that a unit mass of battery cell can release, usually measured in mAh / g or mAh / kg), discharge capacity, and initial efficiency performance of the battery.

[0065] In some embodiments, the battery cell further includes an encapsulation layer 200 covering the outer peripheral surface of the electrode assembly 100; and / or, a separator wrapping the outer peripheral surface of the negative electrode wire 20.

[0066] The encapsulation layer 200 can be a flexible material layer. The material of the encapsulation layer 200 can be selected from, but is not limited to: fluorinated ethylene propylene copolymer (FEP), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polyvinyl chloride (PVC), or thermoplastic polyurethane (TPU); preferably fluorinated ethylene propylene copolymer (FEP) or polypropylene (PP), as they possess excellent resistance to electrolyte corrosion, low heat shrinkage, and high light transmittance / visibility, making them suitable for the encapsulation requirements of flexible fibrous lithium-ion batteries. The battery cells can be pre-bent or woven into various preset shapes (such as S-shape, spiral, ring, or wave shape) according to actual application requirements, allowing the battery cells to power devices as batteries in the form of woven fabric, such as watch straps. This eliminates the need for additional space in the device for the battery, enabling the battery cells to function as both wearable components and power sources.

[0067] In traditional symmetrical twin-strand twisted-fiber battery cells (i.e., a single positive electrode core wire paired with a single negative electrode core wire), the positive electrode active material loading of a single cell is typically limited to approximately 161 mg / m² due to the twin-strand structure and the coating thickness limit of a single core wire. Increasing the coating thickness to further improve the loading would lead to intensified polarization and increased internal resistance due to an excessively long ion transport path, ultimately resulting in a deterioration in the cell's performance.

[0068] Therefore, when applications require higher capacity output, traditional symmetrical structures cannot be achieved with a single battery cell and must rely on multiple batteries connected in parallel to form a battery pack. To achieve a total positive electrode active material load and discharge capacity comparable to the multi-strand twisted structure of this application (i.e., 6 positive electrode core wires and 1 negative electrode core wire), traditional solutions require connecting 6 symmetrical double-strand twisted battery cells in parallel. This integration method of connecting multiple battery cells in parallel results in significant volume redundancy.

[0069] The volume increases exponentially: the battery cell assembly consists of six twisted-pair cells, each encapsulated using a tubular material (such as an FEP tube with an inner diameter of 1mm and an outer diameter of 2mm) forming an encapsulation layer 200. The total volume of the battery cell assembly is approximately 18.85 cm³. 3 ; In comparison, to achieve the same capacity, the multi-strand twisted single-cell structure provided in this application requires only one set of encapsulation material (such as an FEP tube with an inner diameter of 1.7 mm and an outer diameter of 2.7 mm), and the total volume is only 5.73 cm². 3 .

[0070] Therefore, under the premise of achieving the same positive electrode active material loading and the same capacity output, the volume of the traditional symmetrical double-strand twisted parallel battery pack is about 3 times that of the asymmetrical multi-strand twisted single battery of this patent, and the volumetric energy density of this application is higher.

[0071] Table 2 shows the performance of battery cells fabricated with different numbers of positive electrode wires 10 and negative electrode wires 20. The negative electrode active material layer 21 uses a silicon-carbon-graphite hybrid system. The nominal specific capacity of silicon-carbon is 1790 mAh / g, and the nominal specific capacity of graphite is 340 mAh / g. The mass ratio used is 12% silicon-carbon and 88% graphite.

[0072] Slurry formulation: 92% negative electrode active material: 5% binder (1.4% CMC: 3.6% SBR): 3% conductive agent (conductive carbon black (SuperP)); Solid content of slurry: 51%.

[0073] Positive electrode active material layer 11 formulation: Positive electrode active material: 4.53V high-voltage lithium cobalt oxide, with a nominal specific capacity of 200mAh / g.

[0074] Slurry formulation: 92% active material + 5% binder (polyvinylidene fluoride (PVDF)) + 3% conductive agent (SuperP); Solid content of slurry: 55%.

[0075] Electrolyte: Guotai Huarong: LB-303 specification electrolyte.

[0076] Table 2

[0077] As shown in Table 2, this application achieves a non-linear improvement in the performance of a single battery cell by spirally winding multiple positive electrode wires 10 with N≥2 wires around a single negative electrode wire 20, as detailed below: The capacity per unit length increases in a stepwise manner: When N=1 (traditional single positive, single negative structure), the capacity per unit length is only 25~28 mAh / m; as the N value increases, the capacity increases approximately exponentially, reaching 50~55 mAh / m when N=2 (an increase of about 100%), and 130~150 mAh / m when N=6 (an increase of about 400%). This proves that the twisted structure of multiple positive electrode wires 10 and a single negative electrode wire 20 effectively breaks through the limitation of traditional single-strand fiber battery cells "only relying on thickening the coating to increase capacity". Without increasing ion transport resistance, the capacity is increased on a large scale by increasing the number of active interfaces. Furthermore, when N=1 achieves the same capacity as this application, multiple battery cells need to be connected in parallel, and the space occupied is larger. In comparison, this application has a smaller volume and higher volumetric and gravimetric energy density.

[0078] In this application, the diameter of the positive electrode wire 10 is 0.40mm~0.48mm, and the diameter of the negative electrode wire 20 is 0.70mm~0.75mm. Together with the pitch range of 10mm~20mm, they constitute the mechanical stability range of the multi-strand stranded structure under bending and torsion conditions. This wire diameter range ensures that a single wire can bear 175mg / m~180mg / m of positive electrode active material 11 or 370mg / m~400mg / m of negative electrode active material 21, while avoiding excessive overall stiffness after multi-strand stranding, which would compromise the weavability of the fibrous battery. The aforementioned pitch range is designed to address the stress superposition effect of multiple positive electrode wires 10 when N≥2, and is used to reduce coating powder shedding during the stranding (spiral winding) process.

[0079] The mass of the negative electrode active material 21 is limited to 370 mg / m to 400 mg / m, and the mass of the positive electrode active material 11 is limited to 175 mg / m to 180 mg / m. This forms a defined capacity matching and synergistic relationship with the reversible areal capacity ratio (NP ratio) of the negative electrode wire 20 to the positive electrode wire 10, which is 1.05 to 1.1. The above NP ratio range is used to control the capacity relationship between the positive and negative electrodes within a reasonable range. This avoids the risk of lithium plating due to insufficient negative electrode capacity and prevents an increase in the proportion of inactive mass due to excessively high negative electrode capacity, which would affect the mass energy density of the battery cell. When the NP ratio deviates from the above range, even if the loading of the positive and negative electrode active materials is still within the above range, it will still lead to a decrease of approximately 5% in the battery's initial efficiency and a decrease of approximately 10% in the specific capacity (see Table 1).

[0080] The ratio of active material in the positive and negative electrodes is 89%~92%, binder 4%~6%, and conductive agent 3%~5%. This ensures that the proportion of active material is maximized, while the synergistic effect of binder and conductive agent suppresses coating slippage, powder shedding, and increase in interfacial impedance during multi-strand twisting and bending.

[0081] The following describes a battery device according to some embodiments of this application.

[0082] This application proposes a battery device including at least one battery cell as described in the above embodiments. When there are multiple battery cells, the multiple battery cells are electrically connected in series and / or parallel.

[0083] Because the battery cell is flexible and fibrous with a small cross-sectional diameter, the battery device can be further manufactured into the following structural forms according to usage requirements: Fiber bundle / yarn type battery device: Multiple battery cells are bundled together or woven into multi-core fiber bundles, which look similar to ordinary textile yarns and can be subsequently used in weaving, knitting or embroidery. Fabric-integrated battery devices: Multiple battery cells are woven directly into a flexible base fabric as weft or warp yarns to form a flexible and foldable textile battery module. Strip / Cable Battery Device: Multiple battery cells are arranged in parallel and encapsulated in a flexible strip encapsulation layer 200 to form a flexible wearable power strip; Miniature flexible power module: Multiple battery cells and miniature protection circuits are encapsulated together on a flexible polymer substrate to form a miniature power system for smart wearable terminals.

[0084] The following describes a specific example of an electrical device based on some embodiments of this application.

[0085] This application provides an electrical device including the battery device described in the above embodiments, the battery device being used to provide electrical energy to the electrical device.

[0086] Battery devices can be applied to, but are not limited to, smart wearable devices, such as smartwatch straps, smart bracelets, and smart clothing (heated clothing, heart rate monitoring clothing); flexible portable electronic products, such as power supplies for flexible displays, foldable electronic tags, and flexible sensor nodes; and medical and implantable flexible devices, such as flexible physiological signal monitoring patches and power supply units for wearable drug delivery systems.

[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized in that, include: An electrode assembly includes a separator, a negative electrode wire, and N positive electrode wires, where N is a positive integer greater than 2. The outer peripheral surface of at least one of the positive electrode wires and the negative electrode wires is covered by the separator, and the N positive electrode wires are spirally wound around the same negative electrode wire.

2. The battery cell according to claim 1, characterized in that, N≤6。 3. The battery cell according to claim 1, characterized in that, The negative electrode wire includes a negative electrode active material layer, which includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent. The mass percentages of the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are (89%–92%): (4%–6%): (3%–5%).

4. The battery cell according to claim 3, characterized in that, The negative electrode active material includes silicon carbon and graphite, and the mass percentage of silicon carbon and graphite is (11%~14%): (86%~89%).

5. The battery cell according to claim 1, characterized in that, The positive electrode wire includes a positive electrode active material layer, which includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The mass percentages of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are (89%–92%): (4%–6%): (3%–5%).

6. The battery cell according to claim 1, characterized in that, The negative electrode wire includes a negative electrode active material layer, the negative electrode active material layer includes negative electrode active material, and the mass of the negative electrode active material ranges from 370 mg / m to 400 mg / m; and / or The positive electrode wire includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the mass of the positive electrode active material in each positive electrode wire ranges from 175 mg / m to 180 mg / m.

7. The battery cell according to claim 1, characterized in that, The diameter of the positive electrode wire ranges from 0.4 mm to 0.48 mm; and / or, the diameter of the negative electrode wire ranges from 0.7 mm to 0.75 mm.

8. The battery cell according to claim 1, characterized in that, The pitch of each positive electrode wire ranges from 10mm to 20mm.

9. The battery cell according to claim 1, characterized in that, The ratio of the reversible surface capacity of the negative electrode wire to the reversible surface capacity of the positive electrode wire ranges from 1.05 to 1.

1.

10. The battery cell according to claim 1, characterized in that, The battery cell further includes an encapsulation layer that covers the outer peripheral surface of the electrode assembly; and / or, the separator that wraps around the outer peripheral surface of the negative electrode wire.

11. A battery device, characterized in that, It includes at least one battery cell as described in any one of claims 1 to 10.

12. An electrical appliance, characterized in that, Includes the battery device as described in claim 11, the battery device being used to provide electrical energy to the electrical equipment.

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