battery

Abstract

The present application relates to the technical field of battery, in particular to a battery. The battery comprises electrolyte and a roll core formed by laminating and rolling a positive electrode sheet, a diaphragm and a negative electrode sheet; the positive electrode sheet comprises a tab slot and a notch, the tab slot is arranged on one side edge of the positive electrode sheet, the notch is arranged on the other side edge of the positive electrode sheet and is recessed from the edge to the inside, and the notch and the tab slot are oppositely arranged along the width direction of the positive electrode sheet; the area of the notch is S mm 2 ; the electrolyte comprises butanetricarbonitrile; the mass content of the butanetricarbonitrile in the electrolyte is C1 wt%, and C1 wt% is 0.1 wt%-5 wt%; and the area S mm 2 of the notch and the mass content C1 wt% of the butanetricarbonitrile in the electrolyte satisfy: 5≤S / C1≤725. The battery has excellent fast charging performance, high-temperature storage performance and high-temperature cycle 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 technology, batteries, as crucial energy storage and supply devices, are finding increasingly diverse and sophisticated applications. Consumers are also placing higher demands on battery performance, particularly in terms of charging speed and environmental adaptability. In today's fast-paced world, users expect electronic devices to have rapid charging capabilities to reduce waiting time and improve efficiency. Simultaneously, batteries need to maintain stable operation under various complex environmental conditions, including high temperatures, posing a significant challenge to their high-temperature performance. Therefore, developing a battery product that can both meet the requirements of rapid charging and possess excellent high-temperature performance has become an urgent market need and an inevitable trend in industry development.

[0003] However, existing technologies for improving battery fast-charging performance generally sacrifice battery high-temperature performance to varying degrees, making it difficult to balance fast-charging and high-temperature performance. For example, under high-rate charging conditions, the current density at the electrode tabs increases significantly, becoming a high-risk area for lithium plating. Lithium plating not only leads to battery capacity decay and shortened cycle life but may also cause internal short-circuit safety issues, seriously threatening user safety and the normal operation of equipment.

[0004] Therefore, how to ensure that the battery does not precipitate lithium during high-rate fast charging while not affecting the battery's high-temperature safety performance has become a key technical problem that those skilled in the art urgently need to solve, 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 problem of balancing fast charging performance and high-temperature performance in existing technologies, and to provide a battery solution. This invention, through synergistic improvements to the positive electrode and electrolyte, alleviates lithium plating during high-rate fast charging and exhibits excellent high-temperature storage and cycling performance.

[0006] Based on the above problems, the inventors conducted extensive targeted research and discovered: Optimizing the structure of the positive electrode can effectively improve the lithium plating problem of batteries under high-rate charging conditions. Specifically, the positive electrode of this invention includes a tab groove and a notch (i.e., a void structure formed after the entire positive electrode in a specific area is removed). The tab groove is located on one edge of the positive electrode, and the notch is located on the other edge of the positive electrode. The notch and the tab groove are positioned opposite each other along the width direction of the positive electrode. In this way, the notch on the positive electrode results in a relative excess of negative electrode capacity at the corresponding position, which to a certain extent increases the overall CB value (negative electrode capacity / positive electrode capacity) of the battery. This allows lithium ions to be more uniformly embedded in the negative electrode surface during high-rate charging, effectively suppressing lithium plating and improving the fast-charging performance of the battery.

[0007] However, while this technical solution addresses the lithium plating problem, it also introduces new issues. Due to the reduced amount of active material at the notch, the positive electrode potential is higher, making the positive electrode material more susceptible to degradation reactions at high temperatures. These degradation reactions include damage to the crystal structure, lattice distortion, and increased side reactions between the electrode and electrolyte. The byproducts of these side reactions further coat the electrode surface and block ion transport channels, leading to a significant decrease in the battery's high-temperature storage and cycle performance. To address this problem, this invention focuses on continuously optimizing and improving the electrolyte. Ultimately, it was discovered that adding an appropriate amount of butanetrionitrile (BTCN) to the electrolyte can effectively improve the battery's high-temperature storage and cycle performance. The reason is that BTCN is a short-chain trinitrile, which has stronger diffusion ability compared to other conventional nitriles (such as 1,3,6-hexanetrinitrile HTCN). It can penetrate to the lattice defects not covered by the long-chain trinitrile adsorption layer, react with trace amounts of HF to form amide-fluoride oligomers, filling the microcracks caused by the escape of lattice oxygen. This can both repair the cathode structure and build a low-impedance lithium-ion transport channel, 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, inhibiting the occurrence of side reactions inside the battery. At the same time, the cyano groups can also form stable complexes with high-valence metal ions in the cathode material, effectively inhibiting the dissolution of metal ions and reducing the catalytic decomposition of electrolyte by metal ions. This improves the structural stability of the cathode material, alleviates problems such as gas generation during high-temperature cycling, and significantly improves the high-temperature storage performance and high-temperature cycling performance of the battery.

[0008] Building upon this, the present invention further synergistically regulates the area S of the notch and the mass content C1 of the butanetrionitrile in the electrolyte, ensuring their ratio meets a specific range. This allows the battery to simultaneously meet the requirements of high-rate fast charging without lithium plating and excellent high-temperature performance. The area S of the notch affects the battery's CB value and the current-carrying capacity of the positive tab. A larger S results in a higher CB value and a lower risk of lithium plating at the tab, but also increases the degree of side reactions and the risk of high-temperature degradation due to the increased positive electrode potential. The mass content C1 of the butanetrionitrile determines the degree of improvement in high-temperature degradation of the battery. Therefore, when the ratio of S to C1 is within a specific range, the content of the butanetrionitrile can be matched with the area of ​​the notch, ensuring that the battery does not plating during high-rate fast charging, effectively suppressing the occurrence of internal side reactions and the dissolution of metal ions, and significantly improving the battery's high-temperature performance. When the S / C1 ratio is too high (e.g., greater than 725), the area of ​​the notch is too large, and the amount of butanetrionitrile added is insufficient. Its effect on suppressing internal side reactions of the battery is not good, and it cannot improve the high-temperature performance of the battery. When the S / C1 ratio is too low (e.g., less than 5), the area of ​​the notch is too small, and the content of butanetrionitrile is too high. This will aggravate the side reactions of the electrolyte, destroy the stable solid electrolyte interface (SEI) film formed on the electrode surface, and cause the electrolyte to continuously decompose and consume, resulting in rapid capacity decay and a significant reduction in cycle life. At the same time, excessive butanetrionitrile will also increase the viscosity of the electrolyte, reduce the lithium-ion migration rate, and lead to increased battery polarization and decreased 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 comprising a positive electrode sheet, a separator, and a negative electrode sheet, the positive electrode sheet, the separator, and the negative electrode sheet being stacked and wound to form the core; the positive electrode sheet includes a tab groove and a notch, the tab groove being disposed on one side edge of the positive electrode sheet, the notch being disposed on the other side edge of the positive electrode sheet and recessed inward from that edge, the notch and the tab groove being disposed opposite to each other along the width direction of the positive electrode sheet; the area of ​​the notch is 5 mm. 2 The electrolyte comprises butanetrionitrile; the mass content of butanetrionitrile in the electrolyte is C1wt%, and the C1wt% is 0.1wt%-5wt%; the area of ​​the notch is S mm. 2 The mass content (C1wt%) of the butanetrionitrile in the electrolyte satisfies: 5 ≤ S / C1 ≤ 725.

[0010] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The battery of this invention can achieve excellent fast charging performance, high-temperature storage performance, and high-temperature cycling 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 diagram of the positive electrode sheet in an example of the present invention. Detailed Implementation

[0013] 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.

[0014] 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. The positive electrode includes a tab groove and a notch. The tab groove is located on one edge of the positive electrode, and the notch is located on the other edge of the positive electrode and is recessed inward from that edge. The notch and the tab groove are disposed opposite each other along the width direction of the positive electrode. The area of ​​the notch is 5 mm. 2 The electrolyte comprises butanetrionitrile; the mass content of butanetrionitrile in the electrolyte is C1wt%, and the C1wt% is 0.1wt%-5wt% (e.g., 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%); the area of ​​the notch is S mm. 2 The mass content (C1wt%) of the butanetrionitrile in the electrolyte satisfies: 5 ≤ S / C1 ≤ 725 (e.g., 5, 10, 50, 100, 200, 300, 400, 500, 600, 700 or 725).

[0015] In one instance, Smm 2 5mm 2 -350mm 2 (e.g., 5mm) 2 10mm 2 50mm 2 100mm 2 150mm 2 200mm 2 250mm 2 300mm 2 Or 350mm 2 ).

[0016] In one instance, Smm 2 15mm 2 -250mm 2 .

[0017] In one instance, C1wt% is 0.2wt%-3.5wt% (e.g., 0.2wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt% or 3.5wt%).

[0018] In one instance, 10 ≤ S / C1 ≤ 400.

[0019] In one example, the dimension d1mm of the notch along the length of the positive electrode is 5mm-30mm (e.g., 5mm, 10mm, 15mm, 20mm, 25mm or 30mm).

[0020] In one example, the dimension d2mm of the notch along the width direction of the positive electrode is 0.1mm-15mm (e.g., 0.1mm, 0.5mm, 1mm, 3mm, 5mm, 7mm, 9mm, 11mm, 13mm or 15mm).

[0021] It should be noted that the length direction of the positive electrode is the same as the winding direction of the battery, that is, the length direction of the positive electrode is equivalent to the winding direction of the battery.

[0022] It should be noted that the region in the positive electrode sheet with an uncoated active layer is used to form a groove for welding to the positive electrode tab, i.e., the tab groove. The width direction of the positive electrode sheet is along the extension direction of the positive electrode tab.

[0023] like Figure 1 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 positive electrode sheet includes a tab groove and a notch. The tab groove is disposed on one side edge of the positive electrode sheet, and the notch is disposed on the other side edge of the positive electrode sheet. The notch and the tab groove are disposed opposite to each other along the width direction of the positive electrode sheet (along the width direction of the positive electrode sheet, the projections of the notch and the tab groove at least partially overlap). The dimension of the notch along the length direction of the positive electrode sheet is d1, and the dimension along the width direction of the positive electrode sheet is d2.

[0024] In this invention, d1mm and d2mm can be obtained by methods conventional in the art, such as by measuring with vernier calipers.

[0025] In one example, the butanetrionitrile comprises , and At least one of them.

[0026] In one example, the butanetrionitrile comprises .

[0027] In this invention, the electrolyte 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 anionyl, 1,3,6-hexanetrionitrile, glutaronitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanohepane, tetramethylsuccinic anionyl, 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.

[0028] 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.

[0029] In one example, the mass content (C2wt%) 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%).

[0030] 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.

[0031] In this invention, the electrolyte further includes a second additive; the second additive includes at least one of 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), vinyl sulfate, erythritol sulfate, pentaerythritol bicyclic sulfate, and mannitol carbonate sulfate.

[0032] In one example, the mass content (C3wt%) of the second additive in the electrolyte is 0.3wt%-5wt% (e.g., 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%).

[0033] 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.

[0034] In this invention, the electrolyte further includes ethylene carbonate (EC) and / or 2,2-difluoroethyl acetate (DFEA).

[0035] 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%).

[0036] In one example, the mass content (C5wt%) of the 2,2-difluoroethyl acetate in the electrolyte is 3wt%-50wt% (e.g., 3wt%, 5wt%, 10wt%, 20wt%, 30wt%, 40wt% or 50wt%).

[0037] 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.

[0038] 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.

[0039] In one instance, the third additive comprises lithium difluorooxalate borate.

[0040] In one example, the mass content (C6wt%) 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%).

[0041] 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 (LiPF6). 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.

[0042] In one example, the mass content (C7wt%) of the electrolyte salt in the electrolyte is 13wt%-20wt% (e.g., 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt% or 20wt%).

[0043] In this invention, C1wt%, C2wt%, C3wt%, C4wt%, and C5wt% can be obtained by conventional methods in the art, such as gas chromatography (GC), gas chromatography-mass spectrometry (GCMS), or liquid chromatography (LC).

[0044] In this invention, C6wt% and C7wt% can be obtained by methods conventional in the art, such as by ion chromatography (IC).

[0045] 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).

[0046] In this invention, the positive electrode sheet includes a positive electrode active layer, the positive electrode active layer includes a positive electrode material, and the positive electrode material includes at least one of lithium cobalt oxide, ternary positive electrode material and lithium iron phosphate.

[0047] In one example, the cathode material includes lithium cobalt oxide.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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%.

[0052] 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.

[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%, 20%, 30%, 40% or 50%).

[0056] The mass content of silicon in the negative electrode active layer can be determined by conventional methods in the art. For example, after discharging the battery to 0% SOC (e.g., discharging the battery to 3V), 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 nitrogen or argon atmosphere). The negative electrode active layer can then be peeled off from the negative electrode current collector, and the negative electrode active layer is collected as a test sample. Using a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer), the sample amount is 5mg-15mg. 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 minutes. 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 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 ash. The calculation formula is as follows: Mass content of silicon in the negative electrode active layer = 7 × mass of ash / (15 × mass of test sample).

[0057] 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%.

[0058] 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).

[0059] The batteries can all be assembled in accordance with conventional methods in the field.

[0060] 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.

[0061] 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.

[0062] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0063] The following examples illustrate the lithium-ion secondary battery of the present invention.

[0064] Example 1 Batteries are prepared according to the following method. (1) 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 the mixture was stirred under vacuum until a homogeneous, fluid positive electrode slurry was formed. This slurry was uniformly coated onto both sides of an aluminum foil, and after baking, rolling, and slitting, a positive electrode sheet was obtained. A fixed-size tab groove was formed at a specific location on the positive electrode sheet. Nickel tabs were laser- or ultrasonically welded into this groove to form the positive electrode tab. A notch was laser-cut at a position corresponding to the tab groove along the width of the positive electrode sheet. The area of ​​the notch was S mm. 2 It is 18.2mm 2 S / C1 is 18.2, d1mm is 8.5mm, and d2mm is 2.14mm; (2) 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% by mass. (3) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / EP / PP were mixed thoroughly at a mass ratio of 1:2:2. Then, fully dried LiPF6 was quickly added and dissolved. Finally, the following were added sequentially: The electrolyte was mixed with 1,3-propanesulfonate lactone (PS), stirred until homogeneous, and after passing tests for moisture and free acid, the desired electrolyte was obtained. The total mass of the electrolyte was calculated as follows: C1 wt% = 1%, C3 wt% = 2.5%, and C7 wt% = 16.5%. (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.

[0065] Example 2 Batteries are prepared according to the following method. (1) 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 the mixture was stirred under vacuum until a homogeneous, fluid positive electrode slurry was formed. This slurry was uniformly coated onto both sides of an aluminum foil, and after baking, rolling, and slitting, a positive electrode sheet was obtained. A fixed-size tab groove was formed at a specific location on the positive electrode sheet. Nickel tabs were laser- or ultrasonically welded into this groove to form the positive electrode tab. A notch was laser-cut at a position corresponding to the tab groove along the width of the positive electrode sheet. The area of ​​the notch was S mm. 2 It is 78.5mm 2 S / C1 is 392.5, d1mm is 17.4mm, and d2mm is 4.51mm; (2) 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% by mass. (3) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / EP / PP were mixed thoroughly at a mass ratio of 1:2:2. Then, fully dried LiPF6 and LiTFSI (mass ratio 1:1) were quickly added and dissolved. After dissolution, the following were added sequentially: The electrolyte was mixed with 1,3-propanesulfonate lactone (PS), stirred until homogeneous, and after passing tests for moisture and free acid, the desired electrolyte was obtained. The total mass of the electrolyte was calculated as follows: C1 wt% = 0.2%, C3 wt% = 0.3%, and C7 wt% = 20%. (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.

[0066] Example 3 Batteries are prepared according to the following method. (1) 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 the mixture was stirred under vacuum until a homogeneous, fluid positive electrode slurry was formed. This slurry was uniformly coated onto both sides of an aluminum foil, and after baking, rolling, and slitting, a positive electrode sheet was obtained. A fixed-size tab groove was formed at a specific location on the positive electrode sheet. Nickel tabs were laser- or ultrasonically welded into this groove to form the positive electrode tab. A notch was laser-cut at a position corresponding to the tab groove along the width of the positive electrode sheet. The area of ​​the notch was S mm. 2 It is 249.8mm 2 S / C1 is 71.4, d1mm is 25.2mm, and d2mm is 9.91mm; (2) 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% by mass. (3) Preparation of electrolyte In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / EP / PP were mixed thoroughly at a mass ratio of 1:2:2. Then, fully dried LiPF6 and LiFSI (mass ratio 1:1) were quickly added and dissolved. After dissolution, the following were added sequentially: The electrolyte was mixed with 1,3-propanesulfonate lactone (PS), stirred until homogeneous, and after passing tests for moisture and free acid, the desired electrolyte was obtained. The total mass of the electrolyte was calculated as follows: C1 wt% 3.5%, C3 wt% 5%, and C7 wt% 13%. (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 4 and Comparative Examples 1-4 were performed according to Examples 1-3, except that the "notch" and the mass content C1 of ethyl butyrate in the electrolyte were changed. Specifically, the positive electrode in Comparative Example 1 did not have a notch, and in Comparative Examples 2-2, butanetrionitrile was used. Replace with 1,3,6-hexanetrionitrile of the same mass content. See Table 1 for specific parameter settings. Table 1 Note: The " / " in Table 1 indicates that the parameter does not exist here.

[0068] Example 5 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, the C2wt% is 1.5wt%.

[0069] Example 6 group This set of embodiments is based on Embodiment 1, except that the composition of the electrolyte is changed, as follows: Example 6-1: 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, C4wt% was 2.5wt% and C5wt% was 35wt%. Example 6-2: Based on the electrolyte of Example 1, ethylene carbonate (EC) was added, with a C4 wt% of 2.5 wt% based on the total mass of the electrolyte; In Examples 6-3, based on the electrolyte of Example 1, 2,2-difluoroethyl acetate (DFEA) was added, with C5wt% being 35wt% based on the total mass of the electrolyte.

[0070] Example 7 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, C6wt% is 0.5wt%.

[0071] Example 8 group This set of embodiments is based on Embodiment 1, except that the composition of the electrolyte is changed, as follows: Example 8-1: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C2wt% was 1.5wt%, C4wt% was 2.5wt%, C5wt% was 35wt%, and C6wt% was 0.5wt%. Example 8-2: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C2wt% was 0.3wt%, C4wt% was 5wt%, C5wt% was 5wt%, and C6wt% was 2wt%. Examples 8-3: Based on the electrolyte of Example 1, ADN, EC, DFEA and lithium difluorooxalate borate were added. Based on the total mass of the electrolyte, C2wt% was 4.5wt%, C4wt% was 1wt%, C5wt% was 50wt%, and C6wt% was 0.01wt%.

[0072] 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 2.

[0073] (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 2.

[0074] (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 2.

[0075] Table 2 As can be seen from Table 2, 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.

[0076] 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. The positive electrode includes a tab groove and a notch. The tab groove is located on one edge of the positive electrode, and the notch is located on the other edge of the positive electrode and is recessed inward from that edge. The notch and the tab groove are positioned opposite each other along the width direction of the positive electrode. The area of ​​the notch is S mm. 2 ; The electrolyte comprises butanetrionitrile; the mass content of butanetrionitrile in the electrolyte is C1wt%, and the C1wt% is 0.1wt%-5wt%. The area of ​​the gap is S mm. 2 The mass content (C1wt%) of the butanetrionitrile in the electrolyte satisfies: 5 ≤ S / C1 ≤ 725.

2. The battery according to claim 1, wherein, Smm 2 5mm 2 -350mm 2 Preferably 15mm 2 -250mm 2 ; And / or, C1wt% is 0.2wt%-3.5wt%; And / or, 10≤S / C1≤400.

3. The battery according to claim 1 or 2, wherein the dimension d1mm of the notch along the length direction of the positive electrode sheet is 5mm-30mm; And / or, the dimension d2mm of the notch along the width direction of the positive electrode is 0.1mm-15mm.

4. The battery according to claim 1 or 2, wherein, The butanetrionitrile includes , and At least one of them; Preferably, the butanetrionitrile comprises .

5. The battery according to claim 1 or 2, wherein, The electrolyte 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 (C2wt%) of the first additive in the electrolyte is 0.3wt%-4.5wt%.

6. The battery according to claim 1 or 2, wherein, 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. Preferably, the mass content (C3wt%) of the second additive in the electrolyte is 0.3wt%-5wt%.

7. 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 (C4wt%) of the ethylene carbonate in the electrolyte is not higher than 5wt%. Preferably, the mass content (C5wt%) of 2,2-difluoroethyl acetate in the electrolyte is 3wt%-50wt%.

8. The battery according to claim 1 or 2, wherein, The electrolyte also includes a third additive; Preferably, the third additive includes at least one of lithium difluorooxalate borate, lithium difluorooxalate borate, and lithium tetrafluoroborate. Preferably, the mass content (C6wt%) of the third additive in the electrolyte is 0.01wt%-2wt%.

9. The battery according to claim 1 or 2, wherein, The positive electrode sheet includes a positive electrode active layer, the positive electrode active layer includes a positive electrode material, and the positive electrode material includes lithium cobalt oxide; And / or, the charging cut-off voltage of the battery is ≥4.5V.

10. The battery according to claim 1 or 2, wherein, 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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