battery

Abstract

The application relates to the technical field of batteries, in particular to a battery. The battery comprises electrolyte and a winding core formed by laminating and winding a positive electrode sheet, a diaphragm and a negative electrode sheet; along the winding direction of the winding core, the positive electrode sheet has, from the starting end, a first flat area, a first circular arc area, a second flat area, a second circular arc area, a third flat area, a third circular arc area to an n-th flat area and an n-th circular arc area which are sequentially connected, wherein n>3; the first circular arc area is provided with a gum paper, the gum paper comprises a base material layer and a functional layer coated on at least one side surface of the base material layer, the base material layer comprises a plurality of interlaced and / or laminated fibers to form pores; the size of the gum paper along the length direction of the positive electrode sheet is A1 mm; the mass content of butanetricarboxylic acid in the electrolyte is C1 wt%, C1 wt% is 0.1 wt%-5 wt%; 1<=A1 / C1<=105. The battery has high energy density and excellent fast charging performance, cycle performance and high-temperature storage performance.

Description

Technical Field

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

[0002] With the rapid development of new energy vehicles, portable electronic devices, and energy storage systems, the market has placed more stringent demands on the energy density and charging efficiency of lithium-ion batteries. High-energy-density batteries can significantly improve the range of devices and reduce the frequency of charging, while fast charging technology greatly shortens user waiting time, becoming a key indicator driving technological upgrades in the industry. In existing technologies, one of the main methods to improve battery energy density is to increase the thickness of the active layer on the electrode to accommodate more active material, thereby storing more electrical energy.

[0003] However, as the thickness of the active layer increases, the innermost layer of the electrode will bear greater mechanical stress at the crease during the winding process. This high stress state can easily lead to a weakening of the bonding force between active material particles, and even cause powder to fall off. The fallen powder may puncture the separator during its movement inside the battery, causing direct contact between the positive and negative electrodes and forming an internal short circuit. This will not only cause local overheating of the battery, but may also lead to thermal runaway in severe cases, threatening safety, but will also accelerate the battery capacity decay and seriously affect the battery's fast charging cycle life and long-term stability.

[0004] Therefore, how to effectively solve the risks of mechanical stress concentration, powder shedding and internal short circuit caused by the thickening of the electrode layer while ensuring the high energy density of the battery, so that the battery can have both good fast charging performance and cycle performance, has become a technical problem that urgently needs to be solved in the current battery technology research and development field, and it is also the technical problem that this application aims to solve. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a battery. This invention improves the battery core and electrolyte, and through structural optimization and material innovation, it can effectively suppress risks such as mechanical stress concentration in the innermost layer, powder shedding, and internal short circuits caused by the thickening of the active layer, while ensuring high energy density. This allows the battery to balance high energy density with excellent fast-charging performance, cycle performance, and high-temperature storage performance, comprehensively improving the overall performance of the battery.

[0006] Based on the above problems, the inventors conducted extensive targeted research and discovered: By placing adhesive tape in the first arc region of the battery core, the problem of stress concentration in the first arc region caused by the thickening of the active layer can be specifically solved by utilizing the adhesive's bonding and buffering properties. Specifically, because the innermost layer of the core has the greatest curvature during winding, the active layer experiences the most concentrated stress in this area. During cyclic charging and discharging, the expansion and contraction of the active material causes repeated stress accumulation in this area, leading to separation between the active layer and the current collector interface, and subsequently causing problems such as powder shedding and puncture of the separator. This invention, by placing adhesive tape in the first arc region of the battery core, provides a physical constraint to this area, fixing the active material particles to the electrode surface and preventing particle shedding and puncture of the separator, thus avoiding internal short circuits. Simultaneously, the adhesive tape itself has a certain degree of elastic deformation capability, which can reduce the impact of stress on the active layer during cycling, providing reliable protection for the safe use of the battery. Furthermore, the adhesive tape of this invention allows lithium ions to shuttle and electrolyte to permeate, thereby allowing the capacity of the positive electrode active layer in the area covered by the adhesive tape to function normally, ensuring that the battery maintains a high energy density. However, the adhesive tape covering the surface of the active layer still affects the fluidity of the electrolyte, resulting in insufficient electrolyte wetting and affecting the fast charging performance of the battery. Furthermore, under high temperature and high pressure conditions, some components in the electrolyte are prone to chemical side reactions with the adhesive tape, weakening the protective effect of the adhesive tape on the first arc region. At the same time, the side reaction products will cover the electrode surface and block the ion transport channels, affecting the high temperature storage performance and cycle performance of the battery.

[0007] To address this issue, this invention focuses on the electrolyte and continuously optimizes and improves it. It was ultimately discovered that adding appropriate amounts of carboxylic acid esters and butanetrionitrile (BTCN) to the electrolyte can effectively improve the battery's fast-charging performance, high-temperature storage performance, and high-temperature cycling performance. Specifically, carboxylic acid esters reduce electrolyte viscosity, increase electrolyte wettability, and enhance ionic conductivity, allowing lithium ions to be transported more quickly in the electrolyte, thus facilitating fast charging and effectively improving the battery's fast-charging performance. BTCN reduces side reactions and improves the battery's high-temperature storage and cycling performance. BTCN is a short-chain trinitrile, which has stronger diffusion capabilities compared to other conventional nitriles (such as 1,3,6-hexanetrionitrile HTCN). It can penetrate to lattice defects not covered by the long-chain trinitrile adsorption layer, reacting with trace amounts of HF to form amide-fluoride oligomers, constructing low-impedance lithium-ion transport channels, thus compensating for the defects of incomplete film coverage and high impedance caused by simply adding long-chain trinitrile to the electrolyte. In addition, the cyano groups in BTCN can fully combine with protic acids in the electrolyte to suppress the occurrence of side reactions inside the battery. At the same time, the three cyano groups can also form a stable "tridentate chelate" structure with transition metal ions in the adhesive paper, reducing the oxidative decomposition of the electrolyte by metal leaching, improving problems such as gas generation during high-temperature cycling, and significantly improving the high-temperature storage performance and high-temperature cycling performance of the battery.

[0008] Building upon this, the present invention further coordinates the dimensional A1 of the adhesive tape along the length of the positive electrode sheet and the mass content C1 of butanetrionitrile in the electrolyte, ensuring that their ratio meets a specific range. This guarantees the compatibility of the adhesive tape and butanetrionitrile content, enabling the battery to achieve both high energy density and excellent fast-charging, cycle, and high-temperature storage performance. If A1 / C1 is too large (e.g., greater than 10⁵), i.e., A1 is too large while C1 is too low, the adhesive tape, while providing sufficient physical constraint, will also increase the flow resistance of the electrolyte, exacerbating the problem of insufficient electrolyte wetting. Furthermore, the insufficient BTCN content makes it difficult to effectively suppress the side reactions between the electrolyte components and the adhesive tape under high temperature and pressure, failing to improve the battery's fast-charging, high-temperature storage, and cycle performance. If A1 / C1 is too small (e.g., less than 1), i.e., A1 is too small while C1 is too high, the adhesive tape's coverage area is insufficient, making it difficult to address stress concentration issues. During long-term cycling, this area is still prone to internal short circuits, resulting in poor battery puncture safety performance. Meanwhile, excessive BTCN can also react with other components in the electrolyte, resulting in an excessively thick and uneven solid electrolyte interphase (SEI) film formed on the electrode surface, which increases ion transport impedance and affects the battery's fast charging performance.

[0009] Based on this, the inventors of this invention propose the following solution: This invention provides a battery, characterized in that the battery comprises a core and an electrolyte; the core comprises a positive electrode sheet, a separator, and a negative electrode sheet, which are stacked and wound to form the core; along the winding direction of the core, the positive electrode sheet has, starting from the starting end, a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, a third arc region up to an nth straight region and an nth arc region, wherein n > 3; the first arc region is provided with adhesive paper, the adhesive paper comprising a substrate layer and... A functional layer is coated on at least one surface of the substrate layer; the substrate layer has pores; the adhesive tape has a dimension A1 along the length of the positive electrode; the electrolyte includes a carboxylic acid ester and butanetrionitrile; the mass content of butanetrionitrile in the electrolyte is C1wt%, and C1wt% is 0.1wt%-5wt%; the dimension A1mm of the adhesive tape along the length of the positive electrode and the mass content C1wt% of butanetrionitrile in the electrolyte satisfy: 1≤A1 / C1≤105.

[0010] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: (1) The present invention improves the core and electrolyte. By setting adhesive paper in the first arc area of ​​the core, the adhesive paper’s pores and its own bonding and fixing effect can ensure that the battery can maintain high energy density while suppressing the risk of powder falling off and internal short circuit caused by stress concentration in the first arc area; and increase electrolyte wettability to reduce side reactions. (2) The battery of the present invention has high energy density and excellent fast charging performance, cycle performance and high temperature storage performance.

[0011] 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

[0012] Figure 1 The diagram shown is a schematic representation of the structure of the positive electrode sheet after it is unwound along the winding direction from the inside to the outside of the core in an embodiment of the present invention.

[0013] Figure 2 The diagram shown is a schematic diagram of the positive electrode sheet in an example of the present invention. Detailed Implementation

[0014] 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.

[0015] This invention provides a battery comprising a core and an electrolyte. The core includes a positive electrode, a separator, and a negative electrode, which are stacked and wound to form the core. Along the winding direction of the core, the positive electrode has, starting from the starting end, a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, a third arc region up to an nth straight region and an nth arc region, wherein n > 3 (for example, when n = 5, the positive electrode has, starting from the starting end, a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, a third arc region, a fourth straight region, a fourth arc region, a fifth straight region, and a fifth arc region). The first arc region is provided with adhesive tape; the adhesive tape has a dimension of A1 mm along the length direction of the positive electrode. The electrolyte comprises a carboxylic acid ester and butanetrionitrile; the mass content of butanetrionitrile in the electrolyte is C1wt%, and C1wt% is 0.1wt%-5wt% (e.g., 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%); the dimension A1mm of the adhesive tape along the length of the positive electrode sheet and the mass content C1wt% of butanetrionitrile in the electrolyte satisfy: 1≤A1 / C1≤105 (e.g., 1, 5, 10, 30, 50, 70, 90, or 105). This can be understood as 1≤A1 / C1≤105, where A1 is in mm and C1 is in wt%, and the corresponding values ​​are used for calculation. For example, when A1 is 5mm and C1 is 1.5wt%, substituting A1=5 and C1=1.5, A1 / C1 is 3.3. It should be noted that the length direction of the positive electrode is the same as the winding direction of the battery cell, that is, the length direction of the positive electrode is equivalent to the winding direction of the battery.

[0016] In one instance, 2 ≤ A1 / C1 ≤ 83.

[0017] In one instance, A1mm is 3mm-24mm (e.g., 3mm, 5mm, 7mm, 9mm, 11mm, 13mm, 15mm, 17mm, 19mm, 21mm or 24mm).

[0018] In one example, A1mm is 5mm-19mm.

[0019] In one instance, C1wt% ranged from 0.2wt% to 3.5wt%.

[0020] In this invention, the carboxylic acid ester includes ethyl propionate (EP) and / or propyl propionate (PP); the mass content of the carboxylic acid ester in the electrolyte is C2wt%, and the C2wt% is 5wt%-60wt% (e.g., 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt% or 60wt%).

[0021] In one instance, C2wt% ranged from 10wt% to 40wt%.

[0022] In this invention, the butanetrionitrile comprises , , and At least one of them.

[0023] In one example, the butanetrionitrile comprises .

[0024] In this invention, along the width direction of the positive electrode sheet, the adhesive tape extends beyond the positive electrode sheet by a dimension A2mm that is 0mm-4mm (e.g., 0mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, or 4mm). It is worth noting that A2 indicates the dimension by which the adhesive tape extends beyond the positive electrode sheet on either side of the positive electrode sheet along its width direction. Figure 1 The diagram shows a schematic of the structure of the positive electrode sheet after it is unwound along the winding direction from the inside to the outside in an embodiment of the present invention. As can be seen from the diagram, the positive electrode sheet 1 has, starting from the beginning, a first straight region S1, a first arc region R1, a second straight region S2, a second arc region R2, a third straight region S3, a third arc region R3, up to the nth straight region Sn and the nth arc region Rn, where n > 3. The first arc region is provided with adhesive tape 2. The dimension of the adhesive tape along the length of the positive electrode sheet is A1, and the dimension of the adhesive tape extending beyond the positive electrode sheet along the width of the positive electrode sheet is A2. The present invention limits A1 and A2 to a suitable range, ensuring that the adhesive tape provides sufficient constraint and stress buffering for the first arc region while avoiding obstruction of electrolyte flow and lithium-ion shuttle due to excessive extension of the adhesive tape beyond the positive electrode sheet. This effectively improves electrolyte wettability and battery fast-charging performance, reduces the side reaction interface between the adhesive tape and electrolyte components under high temperature and high pressure, and further enhances the battery's high-temperature storage performance and high-temperature cycle performance. It should be noted that, as Figure 1 As shown, the width direction of the positive electrode is along the extension direction of the tab 3.

[0025] In this invention, A1mm and A2mm can be obtained by methods conventional in the art, such as by measuring with vernier calipers.

[0026] In this invention, C1wt% and C2wt% can be obtained by methods conventional in the art, such as gas chromatography (GC).

[0027] In this invention, the adhesive tape includes a substrate layer and a functional layer coated on at least one surface of the substrate layer; the substrate layer has pores. The pores of the substrate layer can be formed by a plurality of intersecting and / or stacked fibers; the fibers can form a sufficiently dense support structure to ensure the puncture resistance of the adhesive tape during cycling, and can also improve the interfacial bonding between the functional layer and the substrate layer and the electrolyte retention capacity of the adhesive tape, promote lithium-ion shuttle and electrolyte flow, reduce problems such as electrolyte accumulation under the adhesive tape causing bulging, reduce the risk of lithium plating on the negative electrode, improve the interfacial stability and safety of the battery during long-term cycling, and at the same time ensure the normal performance of the capacity in the adhesive tape area, maintaining a high energy density of the battery.

[0028] In this invention, 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 active layer in the third arc region to the nth arc region is provided with a recessed region, the recessed region including a plurality of recesses. It should be noted that: "the third arc region to the nth arc region" refers to each arc region starting from the third arc region in the winding core, sequentially covering the fourth arc region up to the nth arc region, excluding the straight region located between adjacent arc regions; the "recess" is recessed from near the winding center to away from the winding center. The recessed area not only provides space for the volume expansion of the negative electrode active material, effectively releasing the internal stress generated in the arc area, alleviating stress concentration in the arc area, and reducing the risk of interfacial delamination and powder shedding between the active layer and the current collector; it also increases the contact area between the electrolyte and the surface of the active layer, improves the uniformity of electrolyte wetting in the arc area, increases the electrolyte storage capacity in the arc area, facilitates the rapid transport of lithium ions, and further improves the fast charging performance and cycle performance of the battery.

[0029] In one example, the depth dμm of the recess is 5μm-40μm (e.g., 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, or 40μm). The depth of the recess has a conventional meaning in the art, referring to the vertical distance from the lowest point within the recess to the surface of the positive electrode sheet, and can be measured by conventional methods in the art, such as using a 3D profilometer to select at least 10 recesses on the surface of the positive electrode sheet, measuring the depth of each recess, and taking the average value to obtain the depth of the recess.

[0030] In one example, the width w1mm of the recess is 0.03mm-1mm (e.g., 0.03mm, 0.05mm, 0.1mm, 0.5mm, or 1mm). When the projection of the recess onto the thickness direction of the positive electrode sheet is a regular circle, the width of the recess is the diameter of the regular circle; when the projection of the recess onto the thickness direction of the positive electrode sheet is not a "regular circle," the width of the recess is the equivalent diameter of a circle with the same area as the irregular circle. The width of the recess can be measured using conventional methods in the art, such as using a 3D profilometer to select at least 10 recesses on the surface of the positive electrode sheet, measuring the width of each recess, and taking the average value.

[0031] In one example, the spacing ΔLmm between the recesses is 0.04mm-5mm (e.g., 0.04mm, 1mm, 2mm, 3mm, 4mm, or 5mm). The spacing between the recesses refers to the shortest distance between the edges of the orthographic projections of two adjacent recesses onto the surface of the positive electrode. The spacing between the recesses can be measured using methods conventional in the art, such as by selecting at least 10 adjacent recesses on the surface of the positive electrode using a 3D profilometer, measuring the spacing, and taking the average value.

[0032] In one example, along the width direction of the positive electrode sheet, the distance w2mm from the recessed region to the edge of the positive electrode active layer is 0.1mm-5mm (e.g., 0.1mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, or 5mm). Figure 2 The figure shows a schematic diagram of the structure of the positive electrode sheet in an embodiment of the present invention. As can be seen from the figure, the concave region includes a plurality of concave portions 12. Along the width direction of the positive electrode sheet 1, the distance from the concave region to the edge of the positive electrode active layer 11 is w2.

[0033] In one example, the size L of the recessed region along the length of the positive electrode is 3mm-20mm (e.g., 3mm, 5mm, 10mm, 15mm or 20mm).

[0034] In this invention, the shape of the orthographic projection of the recess on the surface of the positive electrode is not limited, and it can be a circle, an ellipse, a line (including a straight line or a wavy line), a polygon, or other shapes.

[0035] In this invention, the recess can be obtained by conventional means in the art, such as laser facial scanning, etc. This invention does not specifically limit the method of preparing the recess.

[0036] In this invention, the thickness h1 of the positive electrode active layer located in the first arc region facing the inner side of the core and the thickness h2 of the positive electrode active layer located in the first straight region facing the inner side of the core satisfy the following: 2μm≤h2-h1≤35μm (e.g., 2μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm or 35μm); the thickness h3 of the positive electrode active layer located in the second arc region facing the inner side of the core and the thickness h4 of the positive electrode active layer located in the second straight region facing the inner side of the core satisfy the following: 5μm≤h4-h3≤35μm (e.g., 5μm, 10μm, 15μm, 20μm, 25μm, 30μm or 35μm). The closer the arc area is to the center of the core, the smaller its radius of curvature. It is more affected by the volume expansion of the negative electrode and the more concentrated the stress it bears during charging and discharging. By controlling h1, h2, h3, and h4 to keep their thickness difference within a suitable range, it helps to further suppress the risk of active particles falling off and the separator being punctured due to stress concentration in the inner layer of the core, thereby improving the structural stability of the battery.

[0037] In this invention, the material of the substrate layer includes at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and a composite material of polyethylene and polypropylene.

[0038] In one example, the material of the substrate layer includes polyethylene terephthalate.

[0039] In one example, the thickness H1 of the substrate layer is 5 μm to 25 μm (e.g., 5 μm, 8 μm, 11 μm, 14 μm, 17 μm, 20 μm or 25 μm).

[0040] In one example, H1 / C1 ranges from 2 to 150 (e.g., 2, 5, 10, 20, 40, 60, 80, 100, 120, or 150), where C1 is in wt% and H1 is in μm. This can be understood as H1 / C1 being 2-150, calculated using the corresponding values ​​when C1 is in wt% and H1 is in μm. For example, when C1 is 1.5 wt% and H1 is 5.5 μm, substituting C1=1.5 and H1=5.5, H1 / C1 is 3.67. When H1 / C1 is within this range, it can achieve a synergistic effect. The substrate layer provides sufficient mechanical strength and buffering to suppress stress concentration and active layer shedding in the first arc region. Simultaneously, an appropriate amount of butanetrionitrile is sufficient to complex with transition metal ions dissolved from the adhesive paper to form a stable structure and effectively suppress electrolyte side reactions, further improving the battery's fast-charging and high-temperature performance.

[0041] In this invention, the functional layer comprises an adhesive and inorganic particles, wherein the inorganic particles comprise at least one of the following: alumina, boehmite, lanthanum aluminum zirconate, lanthanum aluminum titanate, lithium aluminum titanium phosphate, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, and titanium dioxide.

[0042] In one instance, the inorganic particles comprise aluminum oxide.

[0043] In one example, the adhesive comprises at least one of polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber.

[0044] In one instance, the adhesive comprises polyisobutylene.

[0045] In one example, the thickness H2 of the functional layer is 2μm-15μm (e.g., 2μm, 5μm, 8μm, 11μm, 13μm or 15μm).

[0046] In this invention, the electrolyte further includes a first additive; the first additive includes at least one selected from 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, adiponitrile, succinic anion, 1,3,6-hexanetrionitrile, glutaronitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanohepane, tetramethylsuccinic anion, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 1,4-dicyano-2-butene, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,3,4-tetra(2-cyanoethoxy)butane, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane.

[0047] In one example, the first additive comprises at least one selected from 1,2-bis(cyanoethoxy)ethane, adiponitrile, succinic anhydride, 1,3,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,3,4-tetra(2-cyanoethoxy)butane, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane.

[0048] In one example, the mass content (C3wt%) of the first additive in the electrolyte is 0.3wt%-4.5wt% (e.g., 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt% or 4.5wt%).

[0049] The C≡N functional group in the first additive can undergo a complexation reaction with transition metal ions such as Ni and Co in the cathode material to form a stable complex, thereby forming a stable solid electrolyte interface (CEI) film on the surface of the high-voltage cathode, preventing the dissolution of transition metal ions, alleviating their oxidative decomposition of the electrolyte, reducing the polarization overpotential of the electrode, protecting the crystal structure of the cathode material, and further improving the problems of high-temperature storage and high-temperature cycling gas generation in the battery.

[0050] In this invention, the electrolyte further includes a second additive; the second additive includes at least one of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate.

[0051] In one example, the second additive has a mass content (C4wt%) of 0.3wt%-5wt% in the electrolyte (e.g., 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%).

[0052] The second additive releases active intermediates (such as thiols and sulfonates) through a ring-opening reaction, which quickly cover the positive electrode surface to form a stable and dense CEI film. This effectively prevents direct contact between the electrolyte and the positive electrode material, reduces the occurrence of side reactions, inhibits the corrosion of the battery by HF, and further improves the structural stability of the positive electrode material and the high-temperature cycle performance of the battery.

[0053] In this invention, the electrolyte further includes ethylene carbonate (EC) and / or 2,2-difluoroethyl acetate (DFEA).

[0054] In one example, the ethylene carbonate content in the electrolyte is not higher than 5 wt% (e.g., 0 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%).

[0055] In one example, the mass content (C6wt%) of the 2,2-difluoroethyl acetate in the electrolyte is 3wt%-50wt% (e.g., 3wt%, 5wt%, 10wt%, 20wt%, 30wt%, 40wt% or 50wt%).

[0056] The fluorine atoms in the DFEA molecule give it a low HOMO energy level, which effectively reduces further reactions between the electrolyte and the positive electrode, inhibits the oxidative decomposition of the electrolyte by metals such as Ni, Co, and Mn under high voltage, and improves the stability of the electrolyte in high-voltage environments, ensuring stable battery operation at high voltages. Furthermore, DFEA, when combined with EC, can adjust the electrolyte structure, forming a solvated structure with EC in the inner layer and DFEA in the outer layer. This helps reduce electrolyte viscosity, improve EC film formation efficiency, and enhance the battery's high-voltage, high-temperature cycling performance.

[0057] In this invention, the electrolyte further includes a third additive. The third additive includes at least one selected from lithium difluorooxalate borate, lithium difluorooxalate borate, and lithium tetrafluoroborate.

[0058] In one instance, the third additive comprises lithium difluorooxalate borate.

[0059] In one example, the mass content (C7wt%) of the third additive in the electrolyte is 0.01wt%-2wt% (e.g., 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt% or 2wt%).

[0060] In this invention, the electrolyte further includes an electrolyte salt, which comprises at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium hexafluorophosphate. These lithium salts themselves can improve the lithium-ion conductivity of the electrolyte, ensuring that the battery has high lithium-ion conductivity under high-speed charging conditions, thereby improving the battery's fast-charging performance and cycle stability. Among them, LiTFSI and LiFSI have high chemical and thermal stability and are not prone to hydrolysis.

[0061] In one example, the mass content (C8wt%) of the electrolyte salt in the electrolyte is 13wt%-20wt% (e.g., 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%).

[0062] In this invention, C3wt%, C4wt%, C5wt%, and C6wt% can be obtained by conventional methods in the art, such as gas chromatography (GC), gas chromatography-mass spectrometry (GCMS), or liquid chromatography (LC).

[0063] In this invention, C7wt% and C8wt% can be obtained by methods conventional in the art, such as by ion chromatography (IC).

[0064] In this invention, the electrolyte may also include other conventional choices in the art, such as, but not limited to, at least one of propylene carbonate (PC) and butylene carbonate (BC), 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), and methyl butyrate (MB).

[0065] 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.

[0066] In one example, the cathode material includes lithium cobalt oxide.

[0067] In one example, the lithium cobalt oxide has a particle size Dv50 of 8μm-25μm (e.g., 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm or 25μm), which can be obtained by laser particle size analyzer.

[0068] In one example, the specific surface area of ​​the lithium cobalt oxide is 0.125 m². 2 / g-0.225m 2 / g (e.g., 0.125m) 2 / g, 0.15m 2 / g, 0.175m 2 / g, 0.2m 2 / g or 0.225m 2 / g), can be obtained by testing with a surface area analyzer.

[0069] In one example, the lithium cobalt oxide includes a doping element, which includes at least one selected from Al, Mg, Mn, Cr, Ti, and Zr.

[0070] In one example, the lithium cobalt oxide includes aluminum, and the mass content 'a' of the aluminum is 5000 ppm to 15000 ppm based on the total weight of the lithium cobalt oxide. 'a' can be determined by methods conventional in the art, such as inductively coupled plasma (ICP) testing.

[0071] When lithium cobalt oxide is doped with an appropriate amount of metal elements, the reactivity of Co is reduced, making it less prone to dissolution under high voltage. This prevents irreversible phase transitions or lattice distortions in the crystal structure of lithium cobalt oxide during charge and discharge, further stabilizing the crystal structure and improving the cycle stability of the battery. Especially under high temperature and high pressure conditions, the doped metal elements help stabilize the structure of the cathode material and reduce gas generation caused by excessive thermal decomposition or redox reactions, effectively improving the gas generation problem during high-temperature storage of the battery.

[0072] In the lithium cobalt oxide system, lithium difluorooxalate-borate plays a unique role. The fluorine atoms and oxalate-borate groups in its molecular structure possess high electronegativity and reactivity, enabling it to form a stable coordination structure with cobalt atoms in the lithium cobalt oxide cathode material. This coordination structure optimizes the microstructure and chemical composition of the solid electrolyte interphase (CEI) film on the cathode surface, reducing defects and impurities in the interfacial film. This, in turn, reduces side reactions under high voltage on the cathode side, further improving the battery's high-temperature cycle performance.

[0073] In this invention, the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 -4.5g / cm 3 (For example, 3.4 g / cm³) 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 3.9g / cm 3 4g / cm 3 4.1g / cm 3 4.15g / cm 3 4.2g / cm 3 4.25g / cm 3 4.3g / cm 3 4.4g / cm 3 Or 4.5g / cm 3 The thickness of the positive active layer on both sides of the positive current collector is 0.04mm-0.16mm (e.g., 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm or 0.16mm).

[0074] 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 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 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%.

[0075] In this invention, the battery further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active layer, the negative electrode active layer includes a negative electrode material, and the negative electrode material includes silicon-based material and carbon-based material.

[0076] 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.

[0077] In one example, the particle size Dv50 of the silicon-based material is 5μm-15μm (e.g., 5μm, 7μm, 9μm, 11μm, 13μm or 15μm), which can be obtained by laser particle size analyzer.

[0078] In one example, the carbon-based material includes at least one of artificial graphite, natural graphite, hard carbon, and soft carbon.

[0079] In one example, the particle size Dv50 of the carbon-based material is 2μm-25μm (e.g., 2μm, 5μm, 10μm, 15μm, 20μm or 25μm), which can be obtained by laser particle size analyzer.

[0080] In one example, the silicon content in the negative electrode active layer is 2%-50% by mass (e.g., 2%, 5%, 10%, 20%, 30%, 40%, or 50%), which can be obtained by conventional methods in the art. For example, after discharging the battery to 0% SOC, the negative electrode sheet is disassembled and removed. After soaking in dimethyl carbonate (DMC) solvent for 12 hours, it is rinsed with DMC solvent to remove the lithium salt adhering to the negative electrode sheet. After drying, the negative electrode sheet is subjected to high-temperature treatment at 400°C in an inert atmosphere for 2 hours (e.g., in a tube furnace under a 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 size is 5-15 mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature (25°C) to 900°C at a rate of 10°C / min, and held at 900°C for 40 min. This allows the non-silicon components in the negative electrode active layer to volatilize while the silicon is fully oxidized to silicon dioxide. The remaining substance is the ash content of the negative electrode active layer. The mass content of silicon in the negative electrode active layer can be calculated based on the mass of the ash, using the following formula: Mass content of silicon in the negative electrode active layer = 7 × mass of ash / (15 × mass of test sample).

[0081] 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 selected from superconducting carbon, acetylene black, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the negative electrode binder includes at least one selected from polyvinylidene fluoride, carboxymethyl cellulose, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and polytetrafluoroethylene. 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%.

[0082] In this invention, the charging cutoff voltage of the battery is ≥4.5V (e.g., 4.5V, 4.51V, 4.52V, 4.53V, 4.54V, 4.55V, 4.56V, 4.57V, 4.58V, 4.59V or 4.6V).

[0083] The batteries can all be assembled in accordance with conventional methods in the field.

[0084] 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.

[0085] 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.

[0086] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0087] The following examples illustrate the lithium-ion secondary battery of the present invention.

[0088] Example 1 Batteries are prepared according to the following method. (1) Preparation of adhesive paper Polyisobutylene and alumina were mixed uniformly at a mass ratio of 50:50 and added to a toluene solution to obtain a coating slurry. This slurry was uniformly coated onto one side of a polyethylene terephthalate substrate layer (substrate layer thickness H1 is 5.5 μm, functional layer thickness H2 is 2.8 μm), dried, and then bonded to a release film and wound up to prepare the adhesive tape. The substrate layer includes pores formed by several intersecting and / or stacked fibers. The adhesive tape has a dimension A1mm of 5 mm along the length of the positive electrode sheet, and a dimension A2mm extending beyond the positive electrode sheet of 0 mm. The A1 / C1 ratio is 3.3, and the H1 / C1 ratio is 3.67. (2) Preparation of positive electrode sheet Lithium cobalt oxide, polyvinylidene fluoride, conductive carbon black and carbon nanotubes were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone was added and stirred under vacuum until the mixture became a uniform and fluid positive electrode active layer slurry. The positive electrode active layer slurry was uniformly coated on both sides of the aluminum foil. After baking, rolling, die cutting and sheet making, the outer surface of the positive electrode active layer in the third arc region to the nth arc region was etched with laser processing technology to obtain a concave part. A fixed-size tab groove was provided at a certain position of the positive electrode sheet. The nickel tab was ultrasonically welded into this groove to obtain the positive electrode tab. The adhesive paper prepared in step (1) was then pasted onto the surface of the positive electrode active layer in the first arc region to obtain the positive electrode sheet. The depth dμm of the recess is 22.5μm, the width w1mm of the recess is 0.5mm, the spacing ΔLmm between the recesses is 2.5mm, and the distance w2mm from the recessed region to the edge of the positive electrode active layer is 2.4mm; h2-h1 is 18.5μm, and h4-h3 is 20.2μm. (3) Preparation of negative electrode sheet A negative electrode material (artificial graphite and silicon carbon in a mass ratio of 62:38), sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black, and single-walled carbon nanotubes were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5. Deionized water was added, and the mixture was stirred under vacuum to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil and dried in an oven at 80°C for 10 hours. After rolling and slitting, the negative electrode sheet was obtained. The silicon content in the negative electrode active layer was 25%, the particle size Dv50 of the silicon carbon was 10.2 μm, and the particle size Dv50 of the artificial graphite was 13.5 μm. (4) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (PC) and diethyl carbonate (DEC) were mixed evenly at a 1:1 mass ratio. Then, thoroughly dried LiPF6 was quickly added and dissolved. Afterward, the following were added sequentially... Ethyl propionate (EP) and 1,3-propanesulfonate lactone (PS) were stirred until homogeneous. After passing tests for moisture and free acid, the desired electrolyte was obtained. Based on the total mass of the electrolyte, C1 wt% was 1.5%, C2 wt% was 25%, C4 wt% was 3%, and C8 wt% was 15.5%. (3) 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 (3) 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 (4) is injected into the outer packaging. After vacuum sealing, standing, formation, shaping and sorting, a lithium-ion battery is obtained.

[0089] Example 2 Batteries are prepared according to the following method. (1) Preparation of adhesive paper Polyisobutylene and alumina were mixed uniformly at a mass ratio of 50:50 and added to a toluene solution to obtain a coating slurry. This slurry was uniformly coated onto one side of a polyethylene terephthalate substrate layer (substrate layer thickness H1 is 15 μm, functional layer thickness H2 is 7.5 μm), dried, and then bonded to a release film and wound up to prepare the adhesive tape. The substrate layer includes pores formed by several intersecting and / or stacked fibers. The adhesive tape has a dimension A1mm of 16 mm along the length of the positive electrode sheet, and a dimension A2mm extending beyond the positive electrode sheet of 2 mm. The A1 / C1 ratio is 80, and the H1 / C1 ratio is 75. (2) Preparation of positive electrode sheet Lithium cobalt oxide, polyvinylidene fluoride, conductive carbon black and carbon nanotubes were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone was added and stirred under vacuum until the mixture became a uniform and fluid positive electrode active layer slurry. The positive electrode active layer slurry was uniformly coated on both sides of the aluminum foil. After baking, rolling, die cutting and sheet making, the outer surface of the positive electrode active layer in the third arc region to the nth arc region was etched with laser processing technology to obtain a concave part. A fixed-size tab groove was provided at a certain position of the positive electrode sheet. The nickel tab was ultrasonically welded into this groove to obtain the positive electrode tab. The adhesive paper prepared in step (1) was then pasted onto the surface of the positive electrode active layer in the first arc region to obtain the positive electrode sheet. The depth dμm of the recess is 5.2μm, the width w1mm of the recess is 0.05mm, the spacing ΔLmm between the recesses is 0.04mm, the distance w2mm from the recessed region to the edge of the positive electrode active layer is 0.1mm; h2-h1 is 2.5μm, and h4-h3 is 5μm. (3) Preparation of negative electrode sheet A negative electrode material (artificial graphite and silicon carbon in a mass ratio of 62:38), sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black, and single-walled carbon nanotubes were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5. Deionized water was added, and the mixture was stirred under vacuum to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil and dried in an oven at 80°C for 10 hours. After rolling and slitting, the negative electrode sheet was obtained. The silicon content in the negative electrode active layer was 25%, the particle size Dv50 of the silicon carbon was 5.3 μm, and the particle size Dv50 of the artificial graphite was 2.1 μm. (4) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (PC) and diethyl carbonate (DEC) were mixed evenly at a mass ratio of 1:1. Then, thoroughly dried LiPF6 and LiTFSI (mass ratio of 1:1) were quickly added and dissolved. Then, the following were added sequentially... Propyl propionate (PP) and 1,3-propanesulfonate lactone (PS) were stirred until homogeneous. After passing tests for moisture and free acid, the desired electrolyte was obtained. Based on the total mass of the electrolyte, C1wt% was 0.2%, C2wt% was 40%, C4wt% was 0.3%, and C8wt% was 20%. (3) 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 (3) 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 (4) is injected into the outer packaging. After vacuum sealing, standing, formation, shaping and sorting, a lithium-ion battery is obtained.

[0090] Example 3 Batteries are prepared according to the following method. (1) Preparation of adhesive paper Polyisobutylene and alumina were mixed uniformly at a mass ratio of 50:50 and added to a toluene solution to obtain a coating slurry. This slurry was uniformly coated onto one side of a polyethylene terephthalate substrate layer (substrate layer thickness H1 is 24.8 μm, functional layer thickness H2 is 15 μm), dried, and then bonded to a release film and wound up to prepare the adhesive tape. The substrate layer includes pores formed by several intersecting and / or stacked fibers. The adhesive tape has a dimension A1mm of 19 mm along the length of the positive electrode, and a dimension A2mm extending beyond the positive electrode of 4 mm. The A1 / C1 ratio is 5.4, and the H1 / C1 ratio is 7.09. (2) Preparation of positive electrode sheet Lithium cobalt oxide, polyvinylidene fluoride, conductive carbon black and carbon nanotubes were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone was added and stirred under vacuum until the mixture became a uniform and fluid positive electrode active layer slurry. The positive electrode active layer slurry was uniformly coated on both sides of the aluminum foil. After baking, rolling, die cutting and sheet making, the outer surface of the positive electrode active layer in the third arc region to the nth arc region was etched with laser processing technology to obtain a concave part. A fixed-size tab groove was provided at a certain position of the positive electrode sheet. The nickel tab was ultrasonically welded into this groove to obtain the positive electrode tab. The adhesive paper prepared in step (1) was then pasted onto the surface of the positive electrode active layer in the first arc region to obtain the positive electrode sheet. The depth dμm of the recess is 39.5μm, the width w1mm of the recess is 1mm, the spacing ΔLmm of the recess is 4.8mm, and the distance w2mm from the recess region to the edge of the positive electrode active layer is 4.9mm; h2-h1 is 34.6μm, and h4-h3 is 34.8μm. (3) Preparation of negative electrode sheet A negative electrode material (artificial graphite and silicon carbon in a mass ratio of 62:38), sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive carbon black, and single-walled carbon nanotubes were mixed in a mass ratio of 94.5:2.5:1.5:1:0.5. Deionized water was added, and the mixture was stirred under vacuum to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil and dried in an oven at 80°C for 10 hours. After rolling and slitting, the negative electrode sheet was obtained. The silicon content in the negative electrode active layer was 25%, the particle size Dv50 of the silicon carbon was 14.6 μm, and the particle size Dv50 of the artificial graphite was 24.8 μm. (4) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (PC) and diethyl carbonate (DEC) were mixed evenly at a 1:1 mass ratio. Then, thoroughly dried LiPF6 and LiFSI (mass ratio 1:1) were quickly added and dissolved. After dissolution, the following were added sequentially... The desired electrolyte was obtained by mixing 1,3-propanesulfonate (EP:PP mass ratio 1:1) and 1,3-propanesulfonate lactone (PS) thoroughly, and after passing tests for moisture and free acid, the electrolyte was prepared. The total mass of the electrolyte was calculated as follows: C1 wt% 3.5%, C2 wt% 10%, C4 wt% 5%, and C8 wt% 13%. (3) 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 (3) 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 (4) is injected into the outer packaging. After vacuum sealing, standing, formation, shaping and sorting, a lithium-ion battery is obtained.

[0091] Example 4 group In this set of embodiments, A1 / C1 is controlled by changing C1 and A1, as follows: Example 4-1 is the same as Example 1, except that C1wt% is 0.1%, A1 / C1 is 50, and H1 / C1 is 55; Example 4-2 is the same as Example 2, except that C1wt% is 5%, A1 / C1 is 3.2, and H1 / C1 is 3. Examples 4-3 are the same as Example 1, except that A1mm is 3mm and A1 / C1 is 2. Example 4-4 is the same as Example 1, except that A1mm is 24mm and A1 / C1 is 16; Examples 4-5 are the same as Example 3, except that A1mm is 3.5mm and A1 / C1 is 1; Examples 4-6 are the same as Example 2, except that A1mm is 21mm and A1 / C1 is 105.

[0092] Example 5 group This set of examples follows the same procedures as Example 1, and is used to verify the effect of changes in the mass content (C2wt%) of carboxylic acid esters in the electrolyte, as detailed below: Example 5-1, C2wt% is 5wt%; Example 5-2, C2wt% is 60wt%.

[0093] Example 6 This embodiment is based on Example 1, except that the composition of the electrolyte is changed. Specifically, adiponitrile (ADN) is added to the electrolyte of Example 1. Based on the total mass of the electrolyte, C3wt% is 2.5wt%.

[0094] Example 7 group This set of embodiments is based on Embodiment 1, except that the composition of the electrolyte is changed, as follows: Example 7-1: Based on the electrolyte of Example 1, ethylene carbonate (EC) and 2,2-difluoroethyl acetate (DFEA) were added. Based on the total mass of the electrolyte, C5wt% was 3wt% and C6wt% was 30wt%. Example 7-2: Based on the electrolyte of Example 1, ethylene carbonate (EC) was added, with C5wt% being 3wt% based on the total mass of the electrolyte; Examples 7-3: Based on the electrolyte of Example 1, 2,2-difluoroethyl acetate (DFEA) was added, with C6wt% being 30wt% based on the total mass of the electrolyte.

[0095] Example 8 This embodiment is based on Example 1, except that the composition of the electrolyte is changed. Specifically, a third additive, lithium difluorooxalate borate, is added to the electrolyte of Example 1. Based on the total mass of the electrolyte, C7wt% is 1wt%.

[0096] Example 9 group This set of embodiments is based on Embodiment 1, except that the composition of the electrolyte is changed, as follows: Example 9-1: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C3wt% was 2.5wt%, C5wt% was 3wt%, C6wt% was 30wt%, and C7wt% was 1wt%. Example 9-2: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C3wt% was 0.3wt%, C5wt% was 1.5wt%, C6wt% was 50wt%, and C7wt% was 0.01wt%. Examples 9-3: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C3wt% was 4.5wt%, C5wt% was 4.5wt%, C6wt% was 10wt%, and C7wt% was 2wt%.

[0097] Comparative Example 1 This comparative example is based on Example 1, except that no adhesive tape is provided on the surface of the positive electrode active layer in the first arc region.

[0098] Comparative Example 2 This comparative study was conducted in accordance with Example 1, except that the composition of the electrolyte was changed, as follows: Comparative Example 2-1, C1wt% is 0%, meaning that the electrolyte does not contain butanetrionitrile; Comparative Example 2-2, C2wt% is 0%, meaning that the electrolyte does not contain carboxylic acid esters; Comparative Examples 2-3, butanetrionitrile Replace with 1,3,6-hexanetrionitrile.

[0099] Comparative Example 3 Groups In this comparative study, the ratios A1 / C1 and H1 / C1 were adjusted by changing C1 and A1, as follows: Comparative Example 3-1 is the same as Example 1, except that C1wt% is 0.05%, A1 / C1 is 100, and H1 / C1 is 110; Comparative Example 3-2 is the same as Example 2, except that C1wt% is 6.5%, Al / C1 is 2.5, and H1 / C1 is 2.3. Comparative Example 3-3 is the same as Example 1, except that C1wt% is 4.5%, A1mm is 4mm, A1 / C1 is 0.9, and H1 / C1 is 1.2. Comparative Examples 3-4 are the same as Example 2, except that A1mm is 23mm, A1 / C1 is 115, and H1 / C1 is 75.

[0100] Test case (1) Lithium plating test The batteries prepared in the examples and comparative examples were subjected to lithium plating tests. The specific test methods are as follows: The resulting batteries were charged at 25°C at a 5C rate to a cutoff voltage of 4.55V and a cutoff current of 0.05C. After resting for 5 minutes, they were discharged at a 5C rate to a cutoff voltage of 3V. This constitutes one charge-discharge cycle. After 300 cycles, the batteries were disassembled, and the lithium plating state on the surface of the negative electrode was observed. The evaluation criteria for lithium plating on the negative electrode were 1-3 levels: 1- No lithium plating; 2- Lithium plating on the top, bottom, and creases was recorded as slight lithium plating; 3- Lithium plating across the entire surface was recorded as severe lithium plating. The test results are recorded in Table 1.

[0101] (2) High-temperature storage test The batteries prepared in the examples and comparative examples were subjected to high-temperature storage tests. The specific test methods are as follows: Charge the battery to 4.55V at 0.7C (cutoff current is 0.25C), let it stand for 2 hours, and then test the storage thickness B1. Store it in an oven (temperature is 85℃±2℃) for 8 hours. After the battery returns to room temperature (25℃±2℃), test the final thickness B2. The high temperature storage expansion rate (%) = B2 / B1×100%. Record the test results in Table 1.

[0102] (3) High temperature cycling test The batteries prepared in the examples and comparative examples were subjected to high-temperature cycling tests. The specific test methods are as follows: After measuring the open circuit voltage (OCV), the battery with 50% SOC was placed in a constant temperature environment at 45℃ and charged to 4.55V at a constant current and constant voltage of 0.7C. After resting for 30 minutes, it was discharged to 3.0V at a constant current of 0.5C, and the discharge capacity C0 was recorded. When the cycle reached 400 cycles, the discharge capacity Cn of the last cycle was recorded. The formula for calculating the capacity retention rate of the nth cycle is: Capacity retention rate (%) = Cn / C0 × 100%. The test results are recorded in Table 1.

[0103] Table 1 As can be seen from Table 1, compared with the comparative example, the battery of the present invention can achieve lithium non-deposition or only slight lithium deposition under high-rate charge and discharge conditions, and has a low thickness expansion rate after high-temperature storage. The battery of the present invention has excellent high-temperature cycle performance.

[0104] 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 battery, characterized in that, The battery includes a core and an electrolyte. The core includes a positive electrode, a separator, and a negative electrode, which are stacked and wound together to form the core. Along the winding direction of the core, the positive electrode sheet has a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, a third arc region, up to an nth straight region and an nth arc region, starting from the starting end, where n > 3; the first arc region is provided with adhesive paper, the adhesive paper includes a substrate layer and a functional layer located on at least one surface of the substrate layer; the substrate layer has pores; the dimension of the adhesive paper along the length direction of the positive electrode sheet is A1 mm; The electrolyte comprises a carboxylic acid ester and butanetrionitrile; the butanetrionitrile in the electrolyte has a mass content of C1wt%, and the C1wt% is 0.1wt%-5wt%. The dimension A1mm of the adhesive tape along the length of the positive electrode sheet and the mass content C1wt% of the butanetrionitrile in the electrolyte satisfy the following condition: 1≤A1 / C1≤105.

2. The battery according to claim 1, wherein, 2≤A1 / C1≤83; And / or, A1mm is 3mm-24mm; preferably 5mm-19mm; And / or, C1wt% is 0.2wt%-3.5wt%.

3. The battery according to claim 1 or 2, wherein, The carboxylic acid ester includes ethyl propionate and / or propyl propionate; the mass content of the carboxylic acid ester in the electrolyte is C2wt%, and the C2wt% is 5wt%-60wt%; preferably 10wt%-40wt%; And / or, along the width direction of the positive electrode sheet, the adhesive tape extends 0mm-4mm beyond the dimension A2mm of the positive electrode sheet; And / or, the butanetrionitrile comprises , , and At least one of them; Preferably, the butanetrionitrile comprises .

4. The battery according to claim 1 or 2, wherein, 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 active layer in the third arc region to the nth arc region is provided with a recessed region, and the recessed region includes a plurality of recesses; Preferably, the depth dμm of the recess is 5μm-40μm, the width w1mm of the recess is 0.03mm-1mm, and the spacing ΔLmm between the recesses is 0.04mm-5mm. Preferably, along the width direction of the positive electrode sheet, the distance w2mm from the recessed region to the edge of the positive electrode active layer is 0.1mm-5mm.

5. The battery according to claim 1 or 2, wherein, The functional layer includes inorganic particles, which include at least one of the following: alumina, boehmite, lanthanum aluminum zirconate, lanthanum aluminum titanate, lithium aluminum titanium phosphate, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, and titanium dioxide. And / or, the material of the substrate layer includes at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, and composite materials of polyethylene and polypropylene; And / or, the mass content C1 of the butanetrionitrile in the electrolyte and the thickness H1 of the substrate layer satisfy: 1≤H1 / C1≤150, where C1 is in wt% and H1 is in μm.

6. The battery according to claim 1 or 2, wherein, The electrolyte further includes a first additive; the first additive includes at least one selected from 1,2-bis(cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, adiponitrile, succinic anion, 1,3,6-hexanetrionitrile, glutaronitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanohepane, tetramethylsuccinic anion, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 1,4-dicyano-2-butene, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,3,4-tetra(2-cyanoethoxy)butane, and 1,2,3,4,5-penta(2-cyanoethoxy)pentane. Preferably, the first additive comprises at least one selected from 1,2-bis(cyanoethoxy)ethane, adiponitrile, butadionitrile, 1,3,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,3,4-tetra(2-cyanoethoxy)butane and 1,2,3,4,5-penta(2-cyanoethoxy)pentane; Preferably, the mass content (C3wt%) of the first additive in the electrolyte is 0.3wt%-4.5wt%.

7. The battery according to claim 1 or 2, wherein, The electrolyte also includes a second additive; Preferably, the second additive comprises at least one of 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate. Preferably, the mass content (C4wt%) of the second additive in the electrolyte is 0.3wt%-5wt%.

8. The battery according to claim 1 or 2, wherein, The electrolyte also includes ethylene carbonate and / or 2,2-difluoroethyl acetate; Preferably, the mass content (C5wt%) of the ethylene carbonate in the electrolyte is not higher than 5wt%. Preferably, the mass content (C6wt%) of 2,2-difluoroethyl acetate in the electrolyte is 3wt%-50wt%.

9. The battery according to claim 1 or 2, wherein, The thickness h1 of the positive electrode active layer located in the first arc region facing the inside of the core and the thickness h2 of the positive electrode active layer located in the first straight region facing the inside of the core satisfy the following: 2μm≤h2-h1≤35μm; And / or, the thickness h3 of the positive electrode active layer located on the inner side of the second arc region facing the core and the thickness h4 of the positive electrode active layer located on the inner side of the second straight region facing the core satisfy: 5μm≤h4-h3≤35μm.

10. The battery according to claim 1 or 2, wherein, The battery further includes a negative electrode sheet; the negative electrode sheet includes a negative electrode active layer, the negative electrode active layer includes a negative electrode material, and the negative electrode material includes 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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