Wound battery

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a winding battery. The winding battery comprises a positive electrode sheet and an electrolyte. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer. The first surface and / or the second surface of the positive electrode sheet has an empty foil area. A first coating layer is arranged on at least part of the surface of the empty foil area to form a first area. The area ratio of the first area on the empty foil area is 0.48 < B < 1. The electrolyte comprises a first additive. The first additive comprises at least one of the substances shown in formula I. In formula I, R1 comprises a fluorine-substituted or unsubstituted alkyl group with a number of carbon atoms greater than or equal to 3. The mass content C1wt% of the first additive in the electrolyte is 1wt% to 25wt%. The battery of the present application has excellent fast charging, cycle performance and high-temperature safety performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a wound battery. Background Technology

[0002] Lithium-ion batteries are widely used in various electronic devices due to their high energy density, becoming the mainstream energy storage device in the current electrochemical field. With the rapid development of intelligent and high-performance electronic devices, users' demands for lithium-ion battery charging efficiency continue to increase, making fast charging technology the core development trend of lithium-ion battery products at present. However, existing lithium-ion batteries with fast charging capabilities generally have poor thermal stability and insufficient tolerance to high-temperature environments, making it difficult to pass industry-standard furnace temperature reliability tests. Reduced high-temperature safety of the battery can easily lead to thermal runaway, bulging, fire, and other safety hazards, severely restricting the application of high-rate fast-charging lithium-ion battery products. This has become a technical problem that urgently needs to be solved in the development of current fast-charging lithium-ion battery technology. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of balancing fast charging performance and high-temperature safety performance in existing technologies, and to provide a wound battery. The wound battery (hereinafter referred to as the battery) of this invention includes a positive electrode sheet and an electrolyte. The surface of the positive electrode sheet has an empty foil area without a positive electrode active layer. At least a portion of the surface of the empty foil area is coated with a first coating to form a first region. The electrolyte includes a first additive. By controlling the area ratio of the first region in the empty foil area and the mass content of the first additive in the electrolyte, this invention can simultaneously improve the battery's fast charging, cycle performance, and high-temperature safety performance.

[0004] To achieve the above objectives, the inventors of this invention have proposed the following solution: This invention provides a wound battery, including a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side surface of the positive current collector; the positive electrode sheet includes a first surface and a second surface, the first surface facing the interior of the wound battery, and the second surface facing the exterior of the wound battery; the first surface and / or the second surface of the positive electrode sheet have empty foil regions, on which the positive active layer is not disposed, and a first coating is disposed on at least a portion of the surface of the empty foil regions to form a first region, the area ratio of the first region on the empty foil regions being B, where 0.48 < B ≤ 1; the first coating includes first inorganic particles; the lithium-ion battery further includes an electrolyte, the electrolyte including a first additive, the first additive including at least one of the substances represented by Formula I: Formula I, R1 includes alkyl groups with 3 or more carbon atoms, whether fluorinated or unsubstituted. The first additive has a mass content of C1wt% in the electrolyte; C1wt% is 1wt%-25wt%.

[0005] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: This invention achieves simultaneous improvement in the fast-charging cycle performance and high-temperature safety performance of the battery by adjusting the area ratio of the first region in the empty foil region and the mass content of the first additive in the electrolyte.

[0006] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0007] Figure 1 The diagram shown is a schematic diagram of the positive electrode sheet in an example of the present invention.

[0008] Figure label: 1. Positive electrode sheet; 11. Positive current collector; 12. Positive active layer; 13. First coating layer; 14. Second coating layer. Detailed Implementation

[0009] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0010] This invention provides a wound battery, including a positive electrode sheet; the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side surface of the positive current collector; the positive electrode sheet includes a first surface and a second surface, the first surface facing the interior of the wound battery, and the second surface facing the exterior of the wound battery; the first surface and / or the second surface of the positive electrode sheet have empty foil regions, on which the positive active layer is not disposed, and a first coating is disposed on at least a portion of the surface of the empty foil regions to form a first region, the area ratio of the first region on the empty foil regions being B, 0.48 < B ≤ 1 (e.g., 0.485, 0.49, 0.5, 0.6, 0.7, 0.8, 0.9, or 1); the first coating includes first inorganic particles; the lithium-ion battery further includes an electrolyte, the electrolyte including a first additive, the first additive including at least one of the substances shown in Formula I: Formula I, R1 includes alkyl groups with fluorine-substituted or unsubstituted carbon atoms of 3 or more.

[0011] In one example, R1 comprises an alkyl group having 3-6 carbon atoms, either fluorinated or unsubstituted.

[0012] The first additive has a mass content of C1wt% in the electrolyte; C1wt% is 1wt%-25wt% (e.g., 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 20wt%, 23wt% or 25wt%).

[0013] In one instance, 0.59 < B ≤ 1.

[0014] In one instance, C1wt% ranged from 3wt% to 20wt%.

[0015] In one instance, 2 ≤ C1 / B ≤ 42 (e.g., 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40 or 42).

[0016] In one instance, 2 ≤ C1 / B ≤ 20.

[0017] To improve the high-temperature safety performance of batteries, this invention focuses on continuous optimization and improvement of the electrolyte. It was discovered that adding an appropriate amount of a first additive to the electrolyte can significantly improve the battery's furnace temperature test pass rate and enhance its high-temperature safety performance. This is because the first additive preferentially undergoes an electrochemical reduction reaction on the negative electrode surface, breaking the SF bond and reacting synergistically with lithium salt and solvent decomposition products to generate a dense, stable, and flexible composite solid electrolyte interface (SEI) film rich in LiF, inorganic sulfides, or organic lithium sulfonates. This interface film effectively blocks continuous side reactions between the electrolyte and active materials, inhibits excessive solvent decomposition and negative electrode interface degradation at high temperatures, and alleviates interface damage caused by negative electrode volume changes during charging and discharging, significantly improving the battery's interface stability and safety performance under high-temperature conditions. However, when the first additive undergoes hydrolysis or electrochemical decomposition in the electrolyte system, it easily releases corrosive hydrogen fluoride (HF). HF can chemically react with the current collector exposed at the positive electrode (such as aluminum foil), damaging the passivation oxide film on the aluminum foil surface, causing corrosion and dissolution of the aluminum foil and releasing a large amount of aluminum ions. Aluminum ions not only migrate to the negative electrode surface and damage the already formed SEI film, but also further catalyze the decomposition of electrolyte side reactions to produce gas, which aggravates the continuous consumption of electrolyte and the increase of battery internal resistance, leading to accelerated battery cycle capacity decay and seriously affecting its long-term cycle stability.

[0018] Based on this, the present invention provides a first coating in the empty foil area on the surface of the positive electrode to form a first region, and limits the area ratio B of the first region in the empty foil area. By utilizing the excellent corrosion resistance and chemical stability of the first coating, a physical isolation barrier is formed on the exposed aluminum foil surface, which can effectively block the direct contact between corrosive components such as HF in the electrolyte and the aluminum foil, inhibiting the corrosion and dissolution of the aluminum foil and the release of aluminum ions. Furthermore, the coating can block the migration path of aluminum ions to the negative electrode interface, avoiding their damage to the negative electrode SEI film, effectively suppressing side reactions, reducing the continuous consumption of electrolyte, thereby significantly improving the interface stability, cycle life and safety of the battery under high temperature conditions.

[0019] Building upon this foundation, the present invention further synergistically regulates the mass content C1 of the first additive in the electrolyte and the area ratio B of the first region in the empty foil region, ensuring that C1 / B is within a specific range. This achieves optimal matching between the protective effects of the first additive and the first coating. On one hand, a stable and dense SEI film is continuously constructed using an appropriate amount of the first additive, providing interface protection at high temperatures. On the other hand, the first coating blocks HF corrosion of the aluminum foil, inhibits aluminum ion deposition and migration, and weakens the catalytic side reactions of aluminum ions on the negative electrode interface and electrolyte solvent. The synergistic effect of these two factors enhances the stability of the positive and negative electrode interfaces, significantly reduces electrolyte decomposition losses, alleviates battery internal resistance growth and capacity decay, and synergistically improves the battery's cycle performance, fast charging performance, and high-temperature safety performance. If C1 / B is too large (e.g., greater than 42), the content of the first additive in the electrolyte is relatively high, the first coating is insufficient, the HF generated by decomposition in the system cannot be effectively blocked, the aluminum foil corrosion is aggravated and a large number of aluminum ions are released, which catalyze the decomposition of the electrolyte. At the same time, a large number of aluminum ions migrate to the negative electrode and destroy the SEI film, causing the battery internal resistance to rise rapidly and the capacity to decrease significantly, affecting the battery's fast charging performance and cycle stability. If C1 / B is too small (e.g., less than 2), it means that the proportion of the first coating protection area is too high and the content of the first additive is insufficient. A continuous and stable SEI film cannot be formed on the negative electrode surface. The electrolyte is prone to violent side reactions at the negative electrode interface, resulting in increased interfacial impedance and deterioration of battery cycle stability and high-temperature safety performance.

[0020] In one example, the second surface of the positive electrode sheet has the first region. The first coating is disposed in the empty foil area on the second surface of the positive electrode sheet. Firstly, this area is located on the outer side of the wound cell, making it more likely to come into contact with electrolyte, moisture, and corrosive components, and thus more susceptible to HF corrosion. The first coating can preferentially construct a physical protective barrier here, blocking HF corrosion of the aluminum foil and inhibiting aluminum ion deposition. Secondly, the ion migration path in this area is shorter, making it easier for deposited aluminum ions to diffuse towards the negative electrode interface. The first coating can effectively block their outward migration channels, preventing damage to the negative electrode SEI film and electrolyte decomposition, while also reducing impedance and further improving the battery's high-temperature stability and long-term cycle life.

[0021] In this invention, the area ratio B of the first region in the empty foil area can be obtained by conventional methods in the art, such as measuring the outline dimensions of the empty foil area and the first region with a ruler and then calculating B.

[0022] In this invention, the mass content C1wt% of the first additive in the electrolyte can be obtained by conventional methods in the art, such as gas chromatography (GC), gas chromatography-mass spectrometry (GCMS) or liquid chromatography (LC).

[0023] In one instance, the first additive includes , , , , , and At least one of them.

[0024] In one instance, the first additive includes .

[0025] <Positive Electrode Tablets> In this invention, the first inorganic particle includes at least one of alumina, boehmite, silicon oxide, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, barium titanate, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphorus oxide, and lithium manganese iron phosphate.

[0026] In one example, the particle size of the first inorganic particle is 0.01 μm to 3 μm (e.g., 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm).

[0027] In one example, the thickness d1 of the first coating is 0.5 μm to 15 μm (e.g., 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm or 15 μm).

[0028] When d1 is too small (e.g., less than 0.5μm), a continuous and dense protective layer cannot be formed, and its effect on preventing HF from contacting the empty foil area is limited. When d1 is too large (e.g., greater than 15μm), it will not only increase the overall areal density and thickness of the positive electrode, squeezing the internal space of the wound cell and reducing the energy density of the battery, but also increase the interfacial contact resistance of the electrode, affecting the further improvement of the battery's fast charging performance and cycle performance.

[0029] In this invention, the first coating further includes a first adhesive, which comprises at least one of polyvinylidene fluoride, polyvinylidene chloride, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, styrene-butadiene rubber, polyethylene oxide, styrene-butadiene emulsion, styrene-acrylic emulsion, ethyl polyacrylate, butyl polymethacrylate, ethylene-vinyl acetate copolymer, and polyvinyl acetate, or at least one of their modifications or copolymers. Copolymers of polyvinylidene fluoride include, for example, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene.

[0030] In this invention, the positive electrode further includes a second coating, which is located between the positive electrode current collector and the positive electrode active layer. For example... Figure 1 The diagram shows a schematic of the structure of the positive electrode sheet in an embodiment of the present invention. As can be seen from the diagram, the positive electrode sheet 1 includes a positive current collector 11 and a positive active layer 12 located on both sides of the positive current collector. The first surface S1 of the positive electrode sheet faces the inside of the wound battery, and the second surface S2 faces the outside of the wound battery. The first and second surfaces of the positive electrode sheet have empty foil areas where no positive active layer is provided. A first coating 13 is provided on the surface of the empty foil areas to form a first region B. The positive electrode sheet also includes a second coating 14, which is located between the positive current collector and the positive active layer. The thickness of the first coating is d1, and the thickness of the second coating is d2.

[0031] In this invention, the second coating comprises second inorganic particles, a conductive agent, and a second binder. The second inorganic particles comprise at least one of alumina, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, barium titanate, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphorus oxide, and lithium manganese iron phosphate. The conductive agent comprises at least one of conductive carbon black, acetylene black, carbon dots, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and carbon nanofibers. The second binder comprises at least one of polyvinylidene fluoride, polyvinylidene chloride, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, styrene-butadiene rubber, polyethylene oxide, styrene-butadiene emulsion, styrene-acrylic emulsion, ethyl polyacrylate, polybutyl methacrylate, ethylene-vinyl acetate copolymer, and polyvinyl acetate, or at least one of their modifications or copolymers.

[0032] In one example, the thickness d2 of the second coating is 0.5 μm-15 μm (e.g., 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, or 15 μm). At this thickness, the second coating can fully coat the surface of the positive electrode current collector to form a continuous and low-resistance conductive interface without occupying the mass and volume of the active material. This maintains efficient electron transport capabilities and provides stress buffering, improving the battery's cycle stability and electrochemical performance. If d2 is too large (e.g., greater than 15 μm), it will additionally occupy internal battery space, increase the mass and volume of inactive materials, and significantly reduce the battery's energy density.

[0033] In this invention, d1 and d2 can be obtained by conventional methods in the art. For example, after discharging the lithium-ion battery to 0% SOC (e.g., discharging the battery to 2.7V), the positive electrode is disassembled and removed. It is then soaked in dimethyl carbonate (DMC) solvent for 12 hours and rinsed with DMC to remove the lithium salt attached to the electrode. The electrode is then cut using an argon ion mill to expose its cross-section. The positions of the first and second coatings are determined by scanning electron microscopy (SEM). Ten test sites are randomly selected on the surface of each coating, and the thickness of each site is measured and the average value is taken.

[0034] In this invention, the positive electrode active layer includes a positive electrode material, which includes at least one of lithium cobalt oxide, ternary positive electrode material and lithium iron phosphate.

[0035] In this invention, the positive electrode active layer further includes a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent includes at least one of superconducting carbon, acetylene black, conductive carbon black, carbon dots, carbon nanotubes (including at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes), graphene, and carbon nanofibers. The positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose, styrene-butadiene rubber, polytetrafluoroethylene, polyethylene oxide, polyacrylic acid, and derivatives of the above substances. Based on the total weight of the positive electrode active layer, the mass content of the positive electrode material is 80%-99.8%, the mass content of the positive electrode conductive agent is 0.1%-10%, and the mass content of the positive electrode binder is 0.1%-10%.

[0036] Electrolyte In this invention, the electrolyte further includes non-fluorinated cyclic carbonates and linear esters; the non-fluorinated cyclic carbonates include ethylene carbonate (EC) and / or propylene carbonate (PC), and the linear esters include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0037] In one example, the non-fluorinated cyclic carbonate in the electrolyte has a mass content of C2wt%, and the C2wt% is 3wt%-30wt% (e.g., 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%).

[0038] In one example, the linear ester has a mass content of C3wt% in the electrolyte, where C3wt% > C2wt%.

[0039] In one example, the linear ester in the electrolyte has a mass content of C3wt%, and the C3wt% is 4wt%-70wt% (e.g., 4wt%, 5wt%, 10wt%, 15wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt% or 70wt%).

[0040] Non-fluorinated cyclic carbonates provide high dielectric constants to promote lithium salt dissociation and participate in the formation of a stable SEI film on the negative electrode surface. However, the central carbon atom connected to two oxygen atoms results in uneven electron cloud distribution and weak bond energy, making them prone to nucleophilic attack and decomposition on the electrode surface, leading to low molecular structural stability. In contrast, the carbonyl carbon in linear esters can form a strong conjugation effect and electron delocalization with neighboring carbon atoms, resulting in structural stability. Furthermore, linear esters generally have lower viscosity than non-fluorinated cyclic carbonates. Therefore, this invention controls the content of linear esters in the electrolyte to be higher than that of non-fluorinated cyclic carbonates. This not only reduces solvent decomposition side reactions and the formation of byproducts but also lowers the overall viscosity of the electrolyte, enhances wettability, reduces interfacial impedance, and promotes rapid lithium-ion transport, thereby further improving the fast-charging cycle performance of the battery.

[0041] In this invention, the electrolyte further includes a second additive, which includes fluoroethylene carbonate (FEC) and / or vinylene carbonate (VC).

[0042] In one example, the second additive has a mass content of C4wt% in the electrolyte, and C4wt% is 5wt%-21wt% (e.g., 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 17wt%, 19wt% or 21wt%).

[0043] FEC preferentially undergoes a reduction reaction on the negative electrode surface to generate fluorinated compounds (such as LiF), which can further optimize the SEI film, improving its mechanical strength, thermal stability, and ionic conductivity, and inhibiting electrolyte decomposition. VC not only forms a dense SEI film with excellent ionic conductivity at the negative electrode, but also a thermally stable CEI film on the positive electrode side, preventing the dissolution or deposition of transition metal ions under high-temperature conditions and avoiding capacity decay. When VC and FEC are used in combination, they have a synergistic effect, further improving the high-temperature cycle stability and safety of the battery.

[0044] In this invention, the electrolyte further includes a third additive, which comprises at least one of lithium difluorooxalate borate (LiODFB), ethylene sulfate (DTD), lithium difluorophosphate, and lithium tetrafluoroborate (LiBF4). This further improves the battery's cycle performance, fast charging performance, and high-temperature safety performance.

[0045] In one example, the third additive has a mass content of C5wt% in the electrolyte, and C5wt% is 0.01wt%-3wt% (e.g., 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%).

[0046] In this invention, the electrolyte further includes a third additive, and the fourth additive includes an amide compound, which includes at least one of N,N-dimethylbutyramide, N,N-dimethyltrifluoroacetamide, N,N-dimethyllauramide, N,N-diethyllauramide and N,N-methylethyllauramide.

[0047] In one example, the fourth additive has a mass content of C6wt% in the electrolyte, and C6wt% is 0.1wt%-5wt% (e.g., 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%).

[0048] Amide compounds can inhibit the decomposition of the first additive to produce HF and consume the HF in the electrolyte, thereby significantly reducing the HF content in the battery, inhibiting aluminum foil corrosion and dissolution, aluminum ion precipitation and side reactions, and improving the long-term cycle stability of the battery.

[0049] In this invention, C2wt%, C3wt%, C4wt%, and C6wt% can be obtained by conventional methods in the art, such as by GC, GCMS, or LC; C5wt% can be obtained by conventional methods in the art, such as by ion chromatography (IC).

[0050] In this invention, the electrolyte further includes an electrolyte salt, which includes at least one of lithium hexafluorophosphate (LiPF6), lithium difluorosulfonylimide, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, or lithium di(trifluoromethylsulfonyl)imide.

[0051] In this invention, the electrolyte may also include at least one of butadionitrile, glutaronitrile, adiponitrile, heptadionitrile, octadionitrile, sebaconitrile, 1,3,6-hexanetrionitrile (HTCN), glyceroltrionitrile and 1,2-bis(2-cyanoethoxy)ethane.

[0052] Negative electrode film In this invention, the wound battery further includes a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer including a negative electrode material, the negative electrode material including silicon-based material and carbon-based material.

[0053] In one example, the silicon-based material includes silicon-carbon materials and / or silicon-oxygen materials. The silicon-carbon material refers to a material comprising elemental silicon and elemental carbon, and the silicon-oxygen material refers to a material comprising elemental silicon and elemental oxygen.

[0054] In one example, the carbon-based material includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0055] In one example, the silicon content in the negative electrode active layer is 2%-50% by mass (e.g., 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%). This can be tested using conventional methods in the art. For example, after discharging the battery to 0% SOC, the negative electrode sheet is disassembled, soaked in DMC solvent for 12 hours, then rinsed with DMC solvent to remove lithium salts adhering to the negative electrode sheet, dried, and then subjected to high-temperature treatment at 400°C in an inert atmosphere for 2 hours (e.g., in a tube furnace under nitrogen or argon atmosphere). The negative electrode active layer can then be peeled off from the negative electrode current collector, and collected as a test sample. Using a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer), the sample volume is 5mg-15mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature (25℃) to 900℃ at a rate of 10℃ / min, and held at 900℃ for 40min. This allows the non-silicon components in the negative electrode active layer to volatilize while the silicon is fully oxidized to silicon dioxide. The mass of the residual material is weighed. The silicon content in the negative electrode active layer can be calculated using the following formula: Silicon content in the negative electrode active layer = 7 × mass of residual material / (15 × mass of test sample).

[0056] In this invention, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent includes at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, carbon nanotubes (including at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes), and carbon fibers. The negative electrode binder includes at least one of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose, styrene-butadiene rubber, polytetrafluoroethylene, polyethylene oxide, polyacrylic acid, and derivatives of the above substances. Based on the total weight of the negative electrode active layer, the mass content of the negative electrode material is 80%-99.8%, the mass content of the negative electrode conductive agent is 0.1%-10%, and the mass content of the negative electrode binder is 0.1%-10%.

[0057] In this invention, the wound battery further includes a separator, the separator comprising a substrate layer, a ceramic layer located on at least one surface of the substrate layer, and adhesive layers located on both outer surfaces of the separator.

[0058] In one example, the substrate layer includes a matrix that may include at least one of polyethylene, polyvinyl chloride, polyoxyethylene, polypropylene, nylon, glass fiber, polyethylene phthalate (PET), polyimide (PI), aramid, cellulose, and nonwoven fabric.

[0059] In one example, the ceramic layer comprises a nitrogen-containing material and / or an inorganic material. The nitrogen-containing material includes melamine, melamine polyphosphate, melamine thiocyanate, melamine cyanurate, formaldehyde polymelamine hydrochloride, melamine polyphosphate, piperazine pyrophosphate, 1,3,5-triazine-2,4,6-triamine, symmetrical triaminotriazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazine-2-yl)guanidine, and 2,4-diamino-6-dimethylamino-1,3,5-triazine. - Triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, 2-amino-4,6-methoxy-1,3,5-triazine; the inorganic material includes at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride.

[0060] In one example, the adhesive layer comprises at least one of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), sodium carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li), and polyvinylpyrrolidone (PVP).

[0061] The assembly of the lithium-ion batteries can all be carried out in accordance with conventional methods in the field.

[0062] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0063] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0064] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0065] The following examples illustrate the lithium-ion rechargeable lithium-ion battery of the present invention.

[0066] Example 1 Batteries are prepared according to the following method. (1) Preparation of positive electrode sheet Step 1: Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 98:1.2:0.8 and placed in N-methylpyrrolidone (NMP). The mixture is stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on the first and second surfaces of the positive electrode current collector. Step 2: Boehmite (particle size 0.3μm) and PVDF are mixed at a mass ratio of 70:30, deionized water is added as a solvent, and the mixture is stirred evenly to obtain a first coating slurry. The slurry is then coated onto a portion of the empty foil area on the first and second surfaces to form the first region. After baking, rolling, and slitting, a positive electrode sheet is obtained. A groove of a fixed size is located on the positive electrode sheet, and a nickel tab is ultrasonically welded into this groove to form the positive electrode tab. The area ratio B of the first region in the empty foil area is 0.85, and C1 / B is 14.12; the thickness d1 of the first coating is 8.1 μm. (2) Preparation of negative electrode sheet A negative electrode material (artificial graphite and silicon carbon in a mass ratio of 70:30), conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a mass ratio of 97:1:1.5:0.5 was mixed with deionized water and stirred under vacuum to prepare a negative electrode slurry. This slurry was then uniformly coated onto both sides of a copper foil. After drying, rolling, die-cutting, and sheet forming, a negative electrode sheet was obtained. A negative electrode tab groove was formed in the negative electrode active layer using laser technology. Copper-plated nickel tabs were ultrasonically welded into the negative electrode tab groove to obtain the negative electrode tabs. The silicon content in the negative electrode active layer was 14.5% by mass. (3) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC, PC, EP, and PP were mixed thoroughly as the base solvent, and lithium hexafluorophosphate (LiPF6), 1,3,6-hexanetrionitrile (HTCN), and the first additive were added sequentially. The second additive, FEC, after passing moisture and free acid tests, yields the electrolyte. The mass ratio of EC to PC is 1.2:1, and the mass ratio of EP to PP is 1:1. Based on the total mass of the electrolyte, the mass content of LiPF6 is 15wt%, the mass content of HTCN is 2wt%, C1wt% is 12wt%, C2wt% is 18wt%, C3wt% is 40wt%, and C4wt% is 13wt%. (4) Battery preparation The positive electrode sheet, separator (a polyethylene film with a thickness of 8 μm, coated with a boehmite ceramic layer with a thickness of 2 μm on one side of the polyethylene film, and then coated with a polyvinylidene fluoride adhesive layer with a thickness of 1 μm on both sides) and negative electrode sheet prepared in step (2) are stacked in sequence to ensure that the separator is between the positive and negative electrode sheets to play a role in isolation. Then, the bare battery is obtained by winding. The bare battery cell is placed in the outer packaging aluminum foil, and the electrolyte prepared in step (3) is injected into the outer packaging. After vacuum sealing, standing, formation, shaping and sorting, a lithium-ion battery is obtained.

[0067] Examples 2, 10, 3, and 4 were conducted in accordance with Example 1, except that the C1 / B ratio was adjusted by changing the mass content C1wt% of the first additive in the electrolyte and the area ratio B of the first region in the empty foil region, in order to verify the effect of the change in C1 / B. Specific parameters are shown in Table 1-1.

[0068] Table 1-1 Example 3 Group This set of embodiments is based on Embodiment 1, except that the position of the first coating layer is changed, as follows: Example 3-1: The first coating slurry is applied to the second surface of the empty foil area; Example 3-2: The first coating slurry is applied to the first surface of the empty foil area.

[0069] Example 4 group This set of embodiments is based on Embodiment 1, except that the particle size of the first inorganic boehmite particles and the thickness d1 of the first coating are changed, as follows: Example 4-1: The boehmite has a particle size of 0.01 μm and a d1 of 0.5 μm; In Example 4-2, the boehmite had a particle size of 2.95 μm and a d1 of 14.8 μm.

[0070] Example 5 group This set of embodiments follows the same procedure as Embodiment 1, except that the positive electrode sheet further includes a second coating. Alumina, conductive carbon black, and PVDF are mixed in a mass ratio of 89:2:9, and N-methylpyrrolidone (NMP) is added as a solvent. The mixture is stirred until homogeneous to obtain a second coating slurry. This second coating is then deposited between the positive electrode current collector and the positive electrode active layer. The thickness d2 of the second coating is varied as follows: Example 5-1, d2 is 8.1 μm; Example 5-2, d2 is 0.5 μm; Example 5-3, d2 is 14.9 μm.

[0071] Examples 6-10 were performed in accordance with Example 1, except that the composition of the electrolyte was changed. Specific parameters are shown in Table 1-2 (Note: "×" in Table 1-2 indicates that the characteristic is not met).

[0072] Table 1-2 In Example 10-1, the first additive was replaced with In Example 10-2, the first inorganic particle is boehmite (particle size 0.3 μm), with d1 of 8.1 μm; the positive electrode also includes a second coating, with d2 of 8.2 μm; in Example 10-3, the first inorganic particle is barium titanate (particle size 0.1 μm), with d1 of 2.2 μm; the positive electrode also includes a second coating, with d2 of 2.3 μm; in Example 10-3, the first additive is replaced with The first inorganic particle is lithium titanium aluminum phosphate (particle size is 0.8μm), with d1 being 5.5μm; the positive electrode also includes a second coating, with d2 being 5.4μm.

[0073] Comparative Example 1 This comparative example is based on Example 1, except that the positive electrode surface does not have a first coating.

[0074] Comparative Example 2 This comparative example is based on Example 1, except that the electrolyte does not contain the first additive.

[0075] Test case (1) High-temperature fast charging performance test The batteries prepared in the examples and comparative examples were subjected to cycle tests, and the specific test methods are as follows: At 45℃, the battery was discharged at 3C to 3.0V, then allowed to stand for 10 minutes, and then charged at 3C to 4.55V with a cutoff current of 0.05C. It was then allowed to stand for 10 minutes, and then discharged at 3C to 3.0V again, and allowed to stand for 10 minutes. The initial discharge capacity C1 was recorded. This cycle was repeated until the 1000th cycle, and the discharge capacity at this point was recorded as the post-cycle capacity C2. The cycle capacity retention rate is calculated as C2 × 100% / C1. The results are shown in Table 2.

[0076] (2) Furnace temperature safety test The batteries prepared in the examples and comparative examples were subjected to furnace temperature safety tests. The specific test methods are as follows: Under conditions of 25±3℃, the battery was charged to 4.55V at a constant current of 0.7C, and then charged to a cutoff current of 0.05C at a constant voltage of 4.55V. The voltage, internal resistance, thickness, and DC internal resistance were tested at full charge, and a picture was taken before the test. The fully charged battery was placed in a test chamber, which was heated at a rate of (5±2)℃ / min. When the temperature inside the chamber reached 130℃±2℃, it was held at that temperature for 60 minutes. After the test, the voltage and internal resistance were tested again, and a picture was taken after the test; the surface temperature of the battery needed to be monitored. If the battery did not catch fire or explode within 60 minutes, it was considered to have passed the test. 15 samples were tested for each example, and the pass rate was recorded. The pass rate = number of passing batteries / total number of tested batteries, and the results are recorded in Table 2.

[0077] Table 2 As can be seen from Table 2, compared with the comparative example, the battery of the present invention can still maintain a high capacity retention rate after 1000 cycles under high-rate charge and discharge conditions at 45°C, and the furnace temperature test pass rate is much higher than that of the comparative example, indicating that the battery of the present invention has both good fast-charging cycle performance and high-temperature safety performance.

[0078] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A wound battery, characterized in that, Including the positive electrode plate; The positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the positive current collector; the positive electrode sheet includes a first surface and a second surface, the first surface facing the interior of the wound battery and the second surface facing the exterior of the wound battery; the first surface and / or the second surface of the positive electrode sheet have empty foil areas, on which the positive active layer is not disposed, and a first coating is disposed on at least a portion of the surface of the empty foil areas to form a first region, the area ratio of the first region on the empty foil areas is B, 0.48 < B ≤ 1; the first coating includes first inorganic particles; The wound battery further includes an electrolyte, the electrolyte comprising a first additive, the first additive comprising at least one of the substances shown in Formula I: Equation I, R1 includes alkyl groups with 3 or more carbon atoms, whether fluorinated or unsubstituted. The first additive has a mass content of C1wt% in the electrolyte; C1wt% is 1wt%-25wt%.

2. The wound battery according to claim 1, wherein 0.59 < B ≤ 1; And / or, C1wt% is 3wt%-20wt%; And / or, 2≤C1 / B≤42; preferably, 2≤C1 / B≤20; And / or, R1 includes alkyl groups with 3-6 carbon atoms that are either fluorinated or unsubstituted; And / or, the second surface of the positive electrode has the first region.

3. The wound battery according to claim 1 or 2, wherein, The first additive includes , , , , , and At least one of them; Preferably, the first additive includes .

4. The wound battery according to claim 1 or 2, wherein, The first inorganic particle includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, barium titanate, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphorus oxide, and lithium manganese iron phosphate. And / or, the particle size of the first inorganic particle is 0.01 μm-3 μm; And / or, the thickness d1 of the first coating is 0.5μm-15μm.

5. The wound battery according to claim 1 or 2, wherein, The positive electrode further includes a second coating, which is located between the positive electrode current collector and the positive electrode active layer; the second coating includes second inorganic particles and a conductive agent, wherein the second inorganic particles include at least one of alumina, boehmite, silicon oxide, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, barium titanate, lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphorus oxide, and lithium manganese iron phosphate. Preferably, the thickness d2 of the second coating is 0.5μm-15μm.

6. The wound battery according to claim 1 or 2, wherein, The electrolyte further includes non-fluorinated cyclic carbonates and linear esters; the non-fluorinated cyclic carbonates include ethylene carbonate and / or propylene carbonate, and the linear esters include at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate; Preferably, the non-fluorinated cyclic carbonate in the electrolyte has a mass content of C2wt%, where C2wt% is 3wt%-30wt%. Preferably, the linear ester in the electrolyte has a mass content of C3wt%, where C3wt% > C2wt%.

7. The wound battery according to claim 1 or 2, wherein, The electrolyte further includes a second additive, which includes fluoroethylene carbonate and / or vinylene carbonate. Preferably, the second additive has a mass content of C4wt% in the electrolyte, where C4wt% is 5wt%-21wt%.

8. The wound battery according to claim 1 or 2, wherein, The electrolyte also includes a third additive, which includes at least one of lithium difluorooxalate borate, vinyl sulfate, lithium tetrafluoroborate, and lithium difluorophosphate. Preferably, the third additive has a mass content of C5wt% in the electrolyte, where C5wt% is 0.01wt%-3wt%.

9. The wound battery according to claim 1 or 2, wherein, The electrolyte further includes a fourth additive, which comprises an amide compound, including at least one of N,N-dimethylbutyramide, N,N-dimethyltrifluoroacetamide, N,N-dimethyllauroamide, N,N-diethyllauroamide, and N,N-methylethyllauroamide. Preferably, the fourth additive has a mass content of C6wt% in the electrolyte, where C6wt% is 0.1wt%-5wt%.

10. The wound battery according to claim 1 or 2, wherein, The wound battery further includes a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer including a negative electrode material, the negative electrode material including silicon-based material and carbon-based material; Preferably, the silicon-based material includes silicon-carbon materials and / or silicon-oxygen materials; Preferably, the carbon-based material includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon; Preferably, the silicon content in the negative electrode active layer is 2%-50% by mass.

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