Battery

Abstract

The invention provides a battery. The battery comprises a positive plate, a negative plate, a diaphragm and an electrolyte, the diaphragm is located between the positive plate and the negative plate, the positive plate comprises 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 comprises a flexibilizer, the flexibilizer comprises a polyester compound, and in the positive active layer, the flexibilizer comprises a polyester compound. The weight content of the flexibilizer is 0.25%-1%, the conductivity X of the positive plate is 10 S / m to 100 S / m, the electrolyte comprises a thiophene compound and / or a derivative of the thiophene compound, and the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 0.1%-1.5%. The problem of breakage and / or damage of the positive plate is solved, meanwhile, migration of the flexibilizer from the positive electrode side to the negative electrode side is reduced, precipitation of the flexibilizer on the negative electrode side is avoided, and the high-rate charging performance and the cycle performance of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage devices, and in particular to a battery. Background Art

[0002] With the development of battery technology, high-energy-density battery technology has become a research hotspot. Increasing the active material loading in the electrode and improving the weight ratio of active materials are effective ways to improve battery energy density. However, while increasing the active material loading in the electrode to improve the electrode surface density also brings some problems, such as increased electrode thickness. After the existing rolling process, the flexibility of thick electrode sheets decreases, and areas with high stress accumulation such as the arc area of ​​the electrode sheet during winding may cause fracture and / or damage.

[0003] Therefore, it is very important to invent a battery with higher flexibility of the electrode. Summary of the Invention

[0004] Research has found that adding a toughening agent to the active layer of the positive electrode sheet can increase the flexibility of the positive electrode sheet and prevent the electrode sheet from breaking and / or damaging. However, under high-rate charge and discharge, the toughening agent in the active layer of the positive electrode sheet will migrate, that is, from the positive electrode side to the negative electrode side and precipitate at the negative electrode, reducing the lithium ion insertion and extraction ability of the negative electrode, resulting in black spots on the surface of the negative electrode, and further causing the deterioration of the high-rate charging performance and cycle performance of the battery.

[0005] To address the problem of toughening agents easily precipitating on the negative electrode side, which deteriorates the battery's high-rate charging and cycling performance, the present invention provides a battery. In the battery of the present invention, the migration of the toughening agent to the negative electrode side is reduced, improving or even preventing the toughening agent's precipitation on the negative electrode side, and enhancing the battery's high-rate charging and cycling performance.

[0006] To achieve the above objectives, the present invention provides a battery, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer comprises a toughening agent, the toughening agent comprises a polyester compound, and the weight content of the toughening agent in the positive electrode active layer is 0.25% to 1%;

[0007] The conductivity X of the positive electrode sheet is 10S / m-100S / m;

[0008] The electrolyte includes additives, and the additives include thiophene compounds and / or derivatives of thiophene compounds. In the electrolyte, the weight content of the thiophene compounds and / or derivatives of thiophene compounds is 0.1%-1.5%.

[0009] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0010] In the battery of the present invention, the positive electrode active layer of the positive electrode sheet includes a toughening agent, and the components of the toughening agent include polyester compounds, which can effectively increase the flexibility of the positive electrode sheet, solve the problems of brittleness and easy breakage caused by the thickening of the electrode sheet of high energy density batteries, and especially avoid the problems of breakage and / or damage in areas with large stress accumulation such as the arc area of ​​the electrode sheet during winding of the wound battery. At the same time, the content of the toughening agent in the positive electrode active layer, the conductivity of the positive electrode sheet and the content of thiophene compounds and / or derivatives of thiophene compounds in the electrolyte are regulated. The three cooperate with each other to avoid the breakage and / or damage of the electrode sheet while reducing the migration of the polyester compound toughening agent from the positive electrode side to the negative electrode side, improving or even avoiding its precipitation on the negative electrode side, and improving the high-rate charging performance and cycle performance of the battery.

[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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, unless otherwise specified, data ranges include endpoints. DETAILED DESCRIPTION

[0012] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0013] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention relates.

[0014] The present invention provides a battery, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer comprises a toughening agent, the toughening agent comprises a polyester compound, and the weight content of the toughening agent in the positive electrode active layer is 0.25%-1%, for example, 0.25%, 0.35%, 0.45%, 0.55%, 0.65%, 0.75%, 0.85%, 0.95%, 1%, or within a range consisting of any two of the above values;

[0015] The conductivity X of the positive electrode sheet is 10 S / m-100 S / m, for example, 10 S / m, 20 S / m, 30 S / m, 40 S / m, 50 S / m, 60 S / m, 70 S / m, 80 S / m, 90 S / m, 100 S / m, or within a range formed by any two of the above values;

[0016] The electrolyte includes an additive, and the additive includes a thiophene compound and / or a derivative of a thiophene compound. In the electrolyte, the weight content of the thiophene compound and / or the derivative of the thiophene compound is 0.1%-1.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or within the range of any two of the above values.

[0017] High energy density batteries have a high active material load, so their pole pieces are thicker. Especially during the winding process of wound batteries, areas with large stress accumulation, such as arc areas, are prone to breakage. Adding polyester compounds as toughening agents to the positive active layer of the positive electrode sheet can effectively increase the flexibility of the positive electrode sheet and effectively improve problems such as pole piece breakage and / or damage. However, the polyester compounds in the positive electrode active layer are easy to migrate from the positive electrode to the negative electrode and precipitate at the negative electrode. Studies have found that by controlling the conductivity of the positive electrode sheet, adjusting the conductive network of the positive electrode sheet, and eliminating local high electric field areas, the electromigration driving force of the toughening agent (polyester compound) can be weakened, thereby reducing the migration of the toughening agent from the positive electrode to the negative electrode. At the same time, an additive including a thiophene compound and / or a derivative of a thiophene compound is added to the electrolyte, and the additive can generate a dense polythiophene sieve in situ on the surface of the positive electrode sheet. The dense polythiophene sieve can block the toughening agent and reduce the migration of the toughening agent. Moreover, the ability of the additive to form a dense polythiophene sieve needs to be carried out under a certain electric field (for example, 10S / m-100S / m). Therefore, it is necessary to simultaneously control the conductivity of the positive electrode sheet and the additive in the electrolyte so that the electric field of the positive electrode sheet is uniform. The additive can form a dense polythiophene sieve that blocks the migration of the toughening agent, eliminates the local high electric field area, weakens the driving force of the electromigration of the toughening agent, and thus reduces the migration of the toughening agent.

[0018] Therefore, when the content of the toughening agent in the positive active layer is 0.25%-1%, the electrical conductivity X of the positive plate is 10 S / m-100 S / m, and the content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 0.1%-1.5%, the toughness of the plate can be improved, the plate fracture and / or damage can be reduced or even avoided, the homogeneous interface reaction can be eliminated to eliminate the local high electric field area, the driving force of the electric migration of the polyester compound can be weakened, and in the large rate charging and discharging, the thiophene compound and / or the derivative of the thiophene compound is easy to be anodically oxidized and polymerized to generate a polythiophene polymer, the dense reticular structure of the polythiophene polymer can be formed on the surface of the positive plate to cover the CEI layer, the dense reticular structure can block the molecular migration of the polyester compound, and the thiophene compound and / or the derivative of the thiophene compound can also regulate the Li + The solvent sheath reduces the probability of the migration of the polyester compound carried by the solvent, thereby further reducing the migration of the polyester compound toughening agent in the positive active layer to the negative electrode, improving or even avoiding the precipitation of the polyester compound toughening agent in the negative electrode, and improving the high rate charging performance and the cycle performance of the battery.

[0019] In the present application, the electrical conductivity X of the positive plate can be obtained by a conventional test method in the art, specifically: the overall resistance of the plate is tested by directly contacting the plate surface with two probes, the resistivity is calculated by the formula p=R*delta / A (R is the resistance, delta is the thickness of the plate, and A is the contact area), and the electrical conductivity X=1 / p.

[0020] In the present application, the weight content of the toughening agent in the positive active layer can be obtained by the following method, specifically: after the battery is discharged to 0% SOC, the positive plate is taken out, soaked and leached in DMC, and dried, the active coating is scraped and weighed to obtain the total mass m1, a certain amount of N-methyl pyrrolidone (NMP) is added to dissolve the binder and the toughening agent at 80°C, and the insoluble substances (active material / conductive agent) are separated by hot filtration; the filtrate and the NMP washing liquid are combined, and after cooling, the concentration C of the toughening agent is measured by gas chromatography (GC); the mass of the toughening agent is calculated as m2=C*total volume of the filtrate, and the weight content of the toughening agent is (m2 / m1)*100%.

[0021] It is understood that, when the electrolyte includes a thiophene compound, “the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte” refers to the weight content ratio of the thiophene compound in the electrolyte; when the electrolyte includes multiple (≥2) thiophene compounds, “the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte” refers to the sum of the weight content ratios of multiple thiophene compounds in the electrolyte; when the electrolyte includes a derivative of a thiophene compound, “the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte” refers to the sum of the weight content ratios of multiple thiophene compounds in the electrolyte. The term “weight content” refers to the weight content ratio of the derivative of the thiophene compound in the electrolyte; when the electrolyte includes multiple (≥2) derivatives of thiophene compounds, “the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte” refers to the sum of the weight content ratios of the derivatives of multiple thiophene compounds in the electrolyte; when the electrolyte includes thiophene compounds and derivatives of thiophene compounds, “the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte” refers to the sum of the weight ratios of the thiophene compound and the derivative of the thiophene compound in the electrolyte.

[0022] In the present invention, the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte can be obtained by testing by the following method: after discharging the battery to 0% SOC, extracting the electrolyte in the battery, and measuring the weight content of the thiophene compound and / or the derivative of the thiophene compound by gas chromatography (GC).

[0023] In the present invention, by adding a toughening agent to the positive electrode active layer and regulating the content of the toughening agent in the positive electrode active layer, the conductivity of the positive electrode sheet and the content of thiophene compounds and / or derivatives of thiophene compounds in the electrolyte, compared with the prior art, the toughness of the electrode sheet can be improved, while the migration rate of the toughening agent in the positive electrode active layer to the negative electrode is reduced, thereby avoiding its precipitation at the negative electrode, and improving the high-rate charging performance and cycle performance of the battery. In order to further improve the effect, one or more technical features can be further optimized.

[0024] In some embodiments, the thiophene compound and / or the derivative of the thiophene compound comprises a five-membered sulfur heterocycle. It is understood that the five-membered sulfur heterocycle refers to a five-membered cyclic conjugated system formed by one sulfur atom and four carbon atoms.

[0025] In some embodiments, the thiophene compound includes one or more structures represented by formula (I), and the derivative of the thiophene compound includes one or more structures represented by formula (II);

[0026]

[0027] wherein R1, R2, R3, R4, R5, R6, R7, R8 are each independently selected from H, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C6-C12 aryl, cyano, halogen, or boronic acid group, and the substituted substituent is halogen.

[0028] In the present application, "C1-C10 alkyl" means alkyl having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, cyclobutyl, n-pentyl, isopentyl, t-pentyl, neopentyl, cyclopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, cyclohexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethylpropyl, 3,3-dimethylbutyl, n-heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, isoheptyl, cycloheptyl, n-octyl, cyclooctyl, nonyl, decyl, and the like.

[0029] In the present application, "C2-C10 alkenyl" means alkenyl having 2 to 10 carbon atoms, such as ethenyl, propenyl, butenyl, 2-methylpropenyl, pentenyl, 2-methylbutenyl, 3-methylbutenyl, hexenyl, 2-methylpentenyl, 3-methylpentenyl, 4-methylpentenyl, 2,2-dimethylbutenyl, 2,3-dimethylbutenyl, heptenyl, and the like.

[0030] In the present application, "C2-C10 alkynyl" means alkynyl having 2 to 10 carbon atoms, such as ethynyl, propynyl, butynyl, 2-methylpropynyl, pentynyl, 2-methylbutynyl, 3-methylbutynyl, hexynyl, 2-methylpentynyl, 3-methylpentynyl, 4-methylpentynyl, heptynyl, 2-methylhexynyl, 3-methylhexynyl, 4-methylhexynyl, and the like.

[0031] In the present application, "C6-C12 aryl" means an aromatic ring-containing group having 6 to 12 carbon atoms, such as phenyl, tolyl, naphthyl, biphenyl, cumyl, t-butylphenyl, anthryl, phenanthryl, benzyl, phenethyl, phenpropyl, and the like.

[0032] In the present application, when R1, R2, R3, R4, R5, R6, R7, R8 are selected from substituted or unsubstituted C6-C12 aryl, two adjacent substituents, for example, R1and R2or R2and R3or R3and R4may be simultaneously linked to two carbon atoms on the aromatic group, for example, For example, R5 and R6 or R6 and R7 or R7 and R8 can be simultaneously connected to two carbon atoms on the aromatic group, for example

[0033] In the present invention, "halogen" may be one or more of F, Cl and Br.

[0034] In some embodiments, R2 is selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C12 aryl, cyano, and the substituted substituent is halogen, and R3 is a boronic acid group.

[0035] In the present invention, the expression "substituted or unsubstituted" means, for example, "substituted or unsubstituted C1-C10 alkyl", which means that the alkyl group may be substituted or may not be substituted by any substituent. When the alkane group is substituted, one H in the alkyl group may be substituted, multiple H groups may be substituted, or all H groups may be substituted.

[0036] In some embodiments, the polyester compound includes dimethyl phthalate and / or diethyl phthalate.

[0037] In some embodiments, the positive electrode active layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes carbon black and carbon nanotubes.

[0038] In some embodiments, the carbon nanotubes include multi-walled carbon nanotubes and / or single-walled carbon nanotubes.

[0039] In some embodiments, the difference in conductivity between any two sites of the positive electrode sheet is less than 0.05 S / m. Controlling the difference in conductivity between any two sites of the positive electrode sheet to be less than 0.05 S / m can make the electric field distribution of the positive electrode sheet more uniform, and is more conducive to the formation of a dense network structure of the polythiophene polymer on the surface of the positive electrode sheet to cover the CEI layer, thereby reducing the migration of the polyester compound toughening agent in the positive electrode active layer to the negative electrode, improving or even avoiding its precipitation at the negative electrode, and improving the high-rate charging performance and cycle performance of the battery.

[0040] In the present invention, the difference in conductivity between any two sites in the positive electrode sheet can be obtained by the following test method: measuring the conductivity values ​​of two points at selected positions respectively, and calculating the absolute value of the difference between the two measured values ​​as the difference in conductivity between any two sites in the positive electrode sheet.

[0041] In some embodiments, the carbon black includes at least one of furnace black, acetylene black, and Ketjen black.

[0042] In some embodiments, the weight content of the carbon black in the positive electrode active layer is 0.3%-2%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2% or within the range of any two of the above values.

[0043] In some embodiments, the specific surface area of ​​the carbon black is 30 m 2 / g-150m 2 / g, for example, 30m 2 / g, 40m 2 / g, 50m 2 / g, 60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g、100m 2 / g、110m 2 / g, 120m 2 / g, 130m 2 / g, 140m 2 / g, 150m 2 / g or within the range formed by any two of the above values, the oil absorption value of the carbon black is not less than 300ml / 100g, for example, 310ml / 100g, 320ml / 100g, 330ml / 100g, 340ml / 100g, 350ml / 100g, 400ml / 100g, etc. Under the premise of meeting the conductivity of the positive electrode sheet, controlling the specific surface area and oil absorption value of the carbon black within the above ranges is conducive to forming a three-dimensional conductive network, ensuring that the positive electrode sheet has a good conductive effect, and is also conducive to the dispersion of the carbon black, thereby achieving a homogenized electric field.

[0044] In some embodiments, the multi-walled carbon nanotubes include multi-walled carbon nanotubes greater than 8 μm in length, and the weight content of the multi-walled carbon nanotubes greater than 8 μm is not less than 50% based on the total weight of the multi-walled carbon nanotubes. When the weight of the multi-walled carbon nanotubes greater than 8 μm accounts for not less than 50% of the total weight of the multi-walled carbon nanotubes, a through-type conductive skeleton can be constructed, which suppresses local current concentration, promotes uniformity of the electric field in the positive electrode sheet, and improves the stability of the overall conductivity of the positive electrode sheet.

[0045] In some embodiments, the aspect ratio of the multi-walled carbon nanotubes is 100-3000, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, or within the range formed by any two of the above values; the average tube diameter of the multi-walled carbon nanotubes is 5nm-12nm, for example, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, or within the range formed by any two of the above values; the average length of the multi-walled carbon nanotubes is 10μm-15μm, for example, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or within the range formed by any two of the above values, which is beneficial to the dispersion of the multi-walled carbon nanotubes in the positive electrode active layer and promotes the homogenization of the electric field.

[0046] In some embodiments, in the positive electrode active layer, the weight content of the multi-walled carbon nanotubes is 0.3%-2.0%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2% or in the range formed by any two of the above values, and the weight content of the single-walled carbon nanotubes is 0%-1%, for example, 0%, 0.06%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1% or in the range formed by any two of the above values.

[0047] According to a specific embodiment, in the positive electrode active layer, the mass content of the carbon black is 0.3%-1%, the weight content of the multi-walled carbon nanotubes is 0.3%-1.0%, and the specific surface area of ​​the carbon black is 30m 2 / g-150m 2 / g, the oil absorption value of the carbon black is not less than 300ml / 100g, the average length of the multi-walled carbon nanotubes is 10μm-15μm, the multi-walled carbon nanotubes include multi-walled carbon nanotubes with a length greater than 8μm, and based on the total weight of the multi-walled carbon nanotubes, the weight content of the multi-walled carbon nanotubes with a length greater than 8μm is not less than 50%, the aspect ratio of the multi-walled carbon nanotubes is 100-3000, and the average tube diameter of the multi-walled carbon nanotubes is 5nm-12nm, which can achieve the control of the conductivity of the positive electrode sheet in the range of 10S / m-100S / m.

[0048] In some embodiments, the single-walled carbon nanotubes include single-walled carbon nanotubes with a length greater than 10 μm, and based on the total weight of the single-walled carbon nanotubes, the weight content of the single-walled carbon nanotubes with a length greater than 10 μm is not less than 50%. When the weight of the single-walled carbon nanotubes with a length greater than 10 μm in the single-walled carbon nanotubes is not less than 50%, a stable conductive network can be constructed, local current concentration can be suppressed, and electric field homogenization can be significantly improved.

[0049] In some embodiments, the aspect ratio of the single-walled carbon nanotubes is 100-10000, and the average tube diameter of the single-walled carbon nanotubes is 1nm-3nm, for example, 1nm, 1.25nm, 1.5nm, 1.75nm, 2nm, 2.25nm, 2.5nm, 2.75nm, 3nm, or in the range of any two of the above values. The average length of the single-walled carbon nanotubes is 15μm-25μm, for example, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, or in the range of any two of the above values, which is conducive to the dispersion of the single-walled carbon nanotubes in the positive electrode active layer and promotes the homogenization of the electric field.

[0050] In the present invention, the average length, diameter and aspect ratio of the multi-walled carbon nanotubes and single-walled carbon nanotubes are measured by the following methods: (1) Atomic force microscopy (AFM) is used. The length of a single carbon nanotube is measured by analyzing the vertical height profile in the AFM three-dimensional morphology. A sufficient number of single carbon nanotubes (usually ≥50) are measured and the average length and length distribution are obtained by statistical calculation. (2) High-resolution TEM images (point resolution ≤0.3nm) are used to directly observe the cross-sectional profile of the carbon nanotubes, measure their outer diameters, and perform statistical distribution analysis (usually ≥50 tubes are measured); (3) Based on the measured length of a single carbon nanotube and the corresponding diameter, the ratio is calculated to obtain the aspect ratio of the carbon nanotube. The aspect ratio finally reported is the average aspect ratio and distribution range of the statistical sample (usually ≥50 tubes).

[0051] According to a specific embodiment, in the positive electrode active layer, the mass content of the carbon black is 0.3%-2%, the weight content of the multi-walled carbon nanotubes is 0.3%-2.0%, the weight content of the single-walled carbon nanotubes is 0%-1%, and the specific surface area of ​​the carbon black is 30m 2 / g-150m 2 / g, the oil absorption value of the carbon black is not less than 300ml / 100g, the average length of the multi-walled carbon nanotubes is 10μm-15μm, the multi-walled carbon nanotubes include multi-walled carbon nanotubes with a length greater than 8μm, and based on the total weight of the multi-walled carbon nanotubes, the weight content of the multi-walled carbon nanotubes with a length greater than 8μm is not less than 50%, the aspect ratio of the multi-walled carbon nanotubes is 100-3000, the average tube diameter of the multi-walled carbon nanotubes is 5nm-12nm, and the single-walled carbon nanotubes are The carbon nanotubes include single-walled carbon nanotubes with a length greater than 10 μm, and based on the total weight of the single-walled carbon nanotubes, the weight content of the single-walled carbon nanotubes with a length greater than 10 μm is not less than 50%, the aspect ratio of the single-walled carbon nanotubes is 100-10000, the average tube diameter of the single-walled carbon nanotubes is 1nm-3nm, and the average length of the single-walled carbon nanotubes is 15μm-25μm, which can achieve the control of the conductivity of the positive electrode sheet in the range of 10S / m-100S / m.

[0052] In some embodiments, the positive electrode active layer includes a lithium cobalt oxide material, and the lithium cobalt oxide material is doped with at least one of Mg, Zr, La, Al, and Nb elements, which greatly improves the conductivity of the positive electrode sheet.

[0053] In some embodiments, the median particle size Dv50 of the lithium cobalt oxide material is 8 μm-15 μm, for example, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or within the range of any two of the above values, which is conducive to its dispersion in the positive electrode active layer and promotes the homogenization of the electric field.

[0054] In the present invention, the median particle size Dv50 of the lithium cobalt oxide material is obtained by the following test method: The particle size of the lithium cobalt oxide material is tested using laser particle size analysis, with key parameters including D10, D50, and D90, and the uniformity is evaluated in combination with the distribution width indicator K90 = (D90-D10) / D50. In actual testing, the sample is dispersed in a liquid or gas, and the particle size distribution in the range of 0.01μm-3500μm is analyzed using a Malvern laser particle size analyzer (such as the Malvern Mastersizer 3000), while the particle morphology and agglomeration state are observed using a scanning electron microscope (SEM).

[0055] In some embodiments, the positive electrode active layer includes a lithium cobalt oxide material, a positive electrode conductor and a positive electrode additive. In the positive electrode active layer, the weight content of the lithium cobalt oxide material is 96%-98.7% (for example, 96%, 96.3%, 96.6%, 96.9%, 97.2%, 97.5%, 97.8%, 98.1%, 98.4%, 98.7% or in the range formed by any two of the above values), the weight content of the positive electrode conductor is 0.25%-1.5% (for example, 0.25%, 0.35%, 0.45%, 0.55%, 0.65%, 0.75%, 0.85%, 0.95%, 1.05%, 1.15%, 1.25%, 1.35%, 1.45%, 1.5% or in the range formed by any two of the above values), and the weight content of the positive electrode additive is not less than 1%.

[0056] In some embodiments, the porosity of the positive electrode sheet is 20%-35%, for example, 20%, 22%, 23%, 25%, 27%, 28%, 30%, 32%, 34%, or 35%, and the peel strength of the positive electrode sheet is not less than 90 N / m.

[0057] In the present invention, the porosity can be determined by conventional testing methods in the field, specifically: based on Bohr's law of inert gas (such as helium), the porosity is calculated by measuring the difference between the actual volume and the apparent volume of the electrode, and the formula is porosity ε (%) = (1-M / ρV) × 100%, where M is the sample mass, V is the sample volume, and ρ is the sample density.

[0058] In the present invention, the peel strength of the positive electrode sheet can be measured by the following method: the positive electrode sheet is cut into strip samples with a width of 10-15 mm and a length ≥100 mm, and the non-coated surface is fixed to the stainless steel plate using double-sided tape (such as 3MVHB) to ensure that the coated area and the current collector form a stable clamp; a universal material testing machine is used to apply the peel force at a constant speed (80-120 mm / min), and the average force value (unit N / m) in the stable stage is recorded, and the peel curve morphology is simultaneously observed to determine the failure mode.

[0059] In some embodiments, the thiophene compound and / or thiophene compound derivative includes 3-thiophene boronic acid Thiophene-1,1-dioxide 2-thiophenecarbonitrile 2-Methylthiophene Benzothiophene At least one of .

[0060] In some embodiments, the separator includes a carrier layer and a coating located on at least one surface of the carrier layer, wherein the coating includes polymer particles composed of polymethyl methacrylate (PMMA). The ester groups in the PMMA interact with the ester groups in the polyester compound in the toughening agent through polarity, thereby intercepting a portion of the migrating polyester compound by chemical adsorption, thereby reducing the amount of toughening agent that migrates to the negative electrode.

[0061] In some embodiments, the average particle size of the polymer particles is 1 μm to 5 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm. Controlling the average particle size of the polymer particles within the above range enables the polymer particles to form fine micropores in the coating, thereby physically blocking the migration of toughening agent molecules toward the negative electrode, further reducing the amount of toughening agent migrating from the positive electrode into the negative electrode, and further improving the high-rate charging performance and cycling performance of the battery.

[0062] In some embodiments, the coating has a thickness of 0.5 μm to 3 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a range formed by any two of the above values. While ensuring the basic air permeability, ion conductivity, and mechanical properties of the separator, the coating of this thickness can physically block the polyester toughening agent while also allowing the polyester toughening agent molecules to pass through longer and more tortuous microscopic pores or polymer chain networks, slowing their migration speed and effectively inhibiting the toughening agent from migrating from the positive electrode side to the negative electrode side, thereby improving the long-term cycling stability of the battery.

[0063] In some embodiments, the coating corresponds to the positive electrode sheet to ensure that the coating plays an effective physical isolation role.

[0064] In some embodiments, the carrier layer includes a substrate layer and a ceramic layer, the ceramic layer is located on one side or both sides of the substrate layer, the ceramic layer includes inorganic particles, and the components of the inorganic particles include one or more of aluminum oxide, boehmite, silicon dioxide, zirconium dioxide, barium sulfate, magnesium hydroxide, fluoroapatite, fluorophlogopite, mullite, aluminum titanate, copper oxide, titanium dioxide, and zinc oxide.

[0065] In some embodiments, the thickness of the ceramic layer is 0.5 μm-3 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or within a range formed by any two of the above values.

[0066] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active layer includes a negative electrode active material, a negative electrode conductor, a negative electrode binder, and a negative electrode thickener.

[0067] In some embodiments, the negative electrode active material includes at least one of a graphite material, a silicon material, a silicon-oxygen material, a silicon-carbon material, and a soft carbon material.

[0068] In some embodiments, the negative electrode conductive agent includes at least one of artificial graphite, conductive carbon black, acetylene black, Ketjen black, conductive carbon fiber, carbon nanotubes, and carbon fiber.

[0069] In some embodiments, the negative electrode binder includes at least one of styrene-butadiene rubber, polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0070] In some embodiments, the negative electrode thickener includes sodium carboxymethyl cellulose and / or sodium alginate.

[0071] In some embodiments, in the negative electrode active layer, the weight content of the negative electrode active material is 85%-98% (for example, 85%, 87%, 89%, 91%, 93%, 95%, 97%, 98% or in the range of any two of the above values), and the weight content of the conductive agent is 0.1%-10% (for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or in the range of any two of the above values). The weight content of the binder is 0.1%-10% (for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or in the range formed by any two of the above values), and the weight content of the thickener is 0.1%-10% (for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or in the range formed by any two of the above values).

[0072] In some embodiments, the electrolyte includes a carbonate solvent, a lithium salt and an additive. In the electrolyte, the weight content of the carbonate solvent is 10%-60% (for example, 10%, 20%, 30%, 40%, 50%, 60% or in the range of any two of the above values), the weight content of the lithium salt is 12%-35% (for example, 12%, 15%, 20%, 25%, 30%, 35% or in the range of any two of the above values), and the weight content of the additive is 3%-20% (for example, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20% or in the range of any two of the above values).

[0073] In some embodiments, the carbonate solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC).

[0074] In some embodiments, the lithium salt includes lithium hexafluorophosphate (LiPF6) and / or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0075] In some embodiments, the additive further comprises fluoroethylene carbonate (FEC) and / or 1,3-propane sultone (PS).

[0076] According to a specific embodiment, in the electrolyte, the weight content of the fluoroethylene carbonate (FEC) is 7%, and the weight content of the 1,3-propane sultone (PS) is 3%.

[0077] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0078] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0079] The present invention will be described in detail below with reference to specific embodiments. These embodiments are intended to help you understand the present invention but are not intended to limit it.

[0080] Example 1

[0081] (1) Preparation of positive electrode sheet

[0082] Lithium cobalt oxide (LiCoO2, particle size Dv50 is 11.95 μm) and polyvinylidene fluoride were weighed and fully mixed in a mass ratio of 97.65:1. Then, conductive carbon black, toughening agent (dimethyl phthalate), carbon nanotubes (including multi-walled carbon nanotubes and single-walled carbon nanotubes) and N-methylpyrrolidone were added. After thorough stirring and vacuum degassing, a uniform positive electrode slurry was formed. The positive electrode slurry was coated on a 9 μm thick aluminum foil (positive electrode current collector) with a coating surface density of 28.25 mg / cm. 2 Then it is dried in an oven at 110-135℃ and rolled (the compaction density is 4.3g / cm 3 ), cut to obtain the positive electrode sheet.

[0083] (2) Preparation of negative electrode sheet

[0084] The negative electrode active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were weighed and thoroughly mixed according to the mass ratio of 96.7:0.7:1.3:1.3. Deionized water was added, and then stirred thoroughly and vacuum-defoamed to form a uniform negative electrode slurry. The negative electrode slurry was coated on a 6 μm thick copper foil (negative electrode current collector) with a coating surface density of 15.29 mg / cm 2 Then it was dried in an 80℃ oven and rolled (the compaction density was 1.7g / cm 3 ), cut to obtain the negative electrode sheet.

[0085] (3) Preparation of electrolyte

[0086] In a glove box filled with argon (H2O < 0.05ppm, O2 < 0.05ppm), EC, PC, and DMC were mixed in a mass ratio of 1:1:1 to obtain an electrolyte solvent. Then, 14wt% of LiPF6 and 6wt% of LiTFSI based on the total mass of the electrolyte were added to the electrolyte solvent. After dissolution, 7wt% of FEC, 5wt% of PS, and 1wt% of 2-methylthiophene based on the total mass of the electrolyte were added. The mixture was stirred evenly and the electrolyte was obtained after passing the moisture and free acid tests.

[0087] (4) Preparation of diaphragm

[0088] First, the dispersant polyacrylamide was completely dissolved in deionized water. Then, polymethyl methacrylate (PMMA) powder was added and stirred thoroughly for 1 hour. The mixture was then sand-milled for another 0.5 hour. Finally, the binder polyacrylate and the thickener carboxymethyl cellulose were added to form a PMMA slurry. Using a micro-concave roller coating process, the PMMA slurry was applied to a single surface of a PE separator substrate (7 μm thick) and dried to obtain the separator.

[0089] (5) Assemble the battery

[0090] The positive electrode sheet, separator and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet, and then the bare battery cell is obtained by welding the tabs and winding. The bare battery cell is placed in a 0.09mm aluminum-plastic film shell, and the battery is prepared through the processes of packaging, liquid injection, formation, secondary sealing, and sorting. Among them, the lithium cobalt oxide material in the positive electrode active layer of the battery is lithium cobalt oxide (LiCoO2), and in the positive electrode active layer, the weight content of the toughening agent (dimethyl phthalate) is 0.5%, the weight content of the conductive agent carbon black is 0.6%, the weight content of the multi-walled carbon nanotube is 0.7%, the weight content of the single-walled carbon nanotube is 0.1%, and the specific surface area of ​​the carbon black is 58m 2 / g, the oil absorption value of carbon black is 340ml / 100g, the multi-walled carbon nanotubes include multi-walled carbon nanotubes with a length greater than 8μm, and based on the total weight of the multi-walled carbon nanotubes, the weight content of the multi-walled carbon nanotubes with a length greater than 8μm is 67.2%, the aspect ratio of the multi-walled carbon nanotubes is 2143, the average tube diameter of the multi-walled carbon nanotubes is 7nm, the average length of the multi-walled carbon nanotubes is 15μm, the single-walled carbon nanotubes include single-walled carbon nanotubes with a length greater than 10μm, and the Based on the total weight of the single-walled carbon nanotubes, the weight content of the single-walled carbon nanotubes with a length greater than 10 μm is 61.8%, the aspect ratio of the single-walled carbon nanotubes is 9000, the average tube diameter of the single-walled carbon nanotubes is 2 nm, the average length of the single-walled carbon nanotubes is 18 μm, the conductivity of the positive electrode sheet is 32 S / m, the difference in conductivity between any two sites on the positive electrode sheet is 0.01 S / m, the weight content of 2-methylthiophene in the electrolyte is 1%, and the thickness of the coating in the diaphragm is 2.5 μm.

[0091] Example 2 group

[0092] This group of examples is used to illustrate the effects of changes in the composition of the toughening agent and / or the weight content of the toughening agent in the positive electrode active layer.

[0093] Example 2-1

[0094] The process is carried out with reference to Example 1, except that the toughening agent is diethyl phthalate.

[0095] Example 2-2

[0096] The process was carried out in accordance with Example 1, except that the weight content of the toughening agent in the positive electrode active layer was 0.28%.

[0097] Example 2-3

[0098] The process was carried out in accordance with Example 1, except that the weight content of the toughening agent in the positive electrode active layer was 0.97%.

[0099] Example 3 group

[0100] This group of embodiments is used to illustrate the impact produced when the conductivity X of the positive electrode sheet changes.

[0101] Example 3-1

[0102] The method is carried out in accordance with Example 1, except that the conductivity X of the positive electrode sheet is 10 S / m, the weight content of the conductive agent carbon black in the positive electrode active layer is 0.3%, the weight content of the multi-walled carbon nanotubes is 0.4%, the weight content of the single-walled carbon nanotubes is 0.01%, and the specific surface area of ​​the carbon black is 108 m 2 / g, the oil absorption value of carbon black is 312ml / 100g, the multi-walled carbon nanotubes include multi-walled carbon nanotubes with a length greater than 8μm, and based on the total weight of the multi-walled carbon nanotubes, the weight content of the multi-walled carbon nanotubes with a length greater than 8μm is 52%, the aspect ratio of the multi-walled carbon nanotubes is 1000, the average tube diameter of the multi-walled carbon nanotubes is 12nm, and the average length of the multi-walled carbon nanotubes is 12μm; the single-walled carbon nanotubes include single-walled carbon nanotubes with a length greater than 10μm, and based on the total weight of the single-walled carbon nanotubes, the weight content of the single-walled carbon nanotubes with a length greater than 10μm is 50.6%, the aspect ratio of the single-walled carbon nanotubes is 6667, the average tube diameter of the single-walled carbon nanotubes is 3nm, and the average length of the single-walled carbon nanotubes is 20μm.

[0103] Example 3-2 is carried out in accordance with Example 1, except that the conductivity of the positive electrode sheet is 98.5 S / m, and the lithium cobalt oxide material in the positive electrode active layer is Li(Co 0.96 Al 0.02 Mg 0.02 )O2, in the positive electrode active layer, the weight content of the conductive agent carbon black is 1.7%, the weight content of the multi-walled carbon nanotube is 1.8%, and the weight content of the single-walled carbon nanotube is 0.7%.

[0104] Example 4 Group

[0105] This set of examples is used to illustrate the effects produced when the weight content of thiophene compounds and / or derivatives of thiophene compounds in the electrolyte and / or the weight content of thiophene compounds and / or derivatives of thiophene compounds in the electrolyte changes.

[0106] Example 4-1

[0107] The process is carried out in accordance with Example 1, except that the thiophene compound and / or the derivative of the thiophene compound is 3-thiopheneboronic acid.

[0108] Example 4-2

[0109] The process is carried out in accordance with Example 1, except that the thiophene compound and / or the derivative of the thiophene compound is 2-thiophenecarbonitrile.

[0110] Example 4-3

[0111] The process is carried out in accordance with Example 1, except that the thiophene compound and / or the derivative of the thiophene compound is thiophene-1,1-dioxide.

[0112] Example 4-4

[0113] The process is carried out in accordance with Example 1, except that the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 0.13%.

[0114] Examples 4-5

[0115] The process is carried out in accordance with Example 1, except that the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 1.5%.

[0116] Example 5

[0117] This example is used to illustrate the effects of changing the composition of the polymer particles in the separator.

[0118] The process is carried out in accordance with Example 1, except that the polymer particles in the separator are composed of polyvinylidene fluoride (PVDF).

[0119] Comparative Example 1

[0120] The process is carried out in accordance with Example 1, except that no toughening agent is contained in the positive electrode active layer.

[0121] Comparative Example 2

[0122] Comparative Example 2-1

[0123] The process was carried out in accordance with Example 1, except that the weight content of the toughening agent in the positive electrode active layer was 0.2%.

[0124] Comparative Example 2-2

[0125] The process was carried out in accordance with Example 1, except that the weight content of the toughening agent in the positive electrode active layer was 1.2%.

[0126] Comparative Examples 2-3

[0127] The method was carried out in accordance with Example 3-1, except that the conductivity of the positive electrode sheet was 9 S / m, the difference in conductivity between any two sites of the positive electrode sheet was 0.03, and the weight content of the multi-walled carbon nanotubes in the positive electrode active layer was 0.3%.

[0128] Comparative Examples 2-4

[0129] The method is carried out in accordance with Example 1, except that the conductivity of the positive electrode is 101 S / m, the conductivity difference between any two sites of the positive electrode is 0.03, and the lithium cobalt oxide material in the positive electrode active layer is Li(Co 0.96 Al 0.02 Mg 0.02 )O2, in the positive electrode active layer, the weight content of the conductive agent carbon black is 2%, the weight content of the multi-walled carbon nanotube is 2%, and the weight content of the single-walled carbon nanotube is 1%.

[0130] Comparative Examples 2-5

[0131] The process is carried out in accordance with Example 1, except that the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 0.08%.

[0132] Comparative Examples 2-6

[0133] The process is carried out in accordance with Example 1, except that the weight content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte is 1.6%.

[0134] Comparative Examples 2-7

[0135] The process is carried out in accordance with Example 1, except that the electrolyte does not contain thiophene compounds and / or thiophene compound derivatives.

[0136] Test Case

[0137] The batteries prepared in the examples and comparative examples were subjected to the following performance tests:

[0138] (1) The situation of electrode fracture after cycling:

[0139] The battery was subjected to a charge and discharge cycle test at a 1.5C charge rate, a 0.7C discharge rate, and a voltage window of 3.0V-4.5V (using a blue electric test device). The cycle was repeated for 800 times. After the cycle was completed, the battery was disassembled and CT was used to observe whether the empty foil at the end of the outer ring of the electrode in the battery cell was broken. If a break occurred, it was considered a failure. If no break occurred, it was considered a pass. Ten battery samples were tested for each embodiment and comparative example, and the results were expressed as "number of tests passed / 10". For example, "5 / 10" means that only 5 of the 10 battery samples passed the test.

[0140] (2) Cycle capacity retention rate / % (tested at 25°C, 800 cycles):

[0141] The battery was subjected to a charge and discharge cycle test at a charge rate of 1.5C, a discharge rate of 0.7C, and a voltage window of 3.0V-4.5V (using a blue electric test device). The cycle was 800 cycles, and the capacity retention rate was calculated using the first discharge capacity C1 and the 800th discharge capacity C800: C800 / C1×100%.

[0142] (3) 4C constant current charging ratio:

[0143] A fresh battery is first discharged at 0.2C to the lower limit voltage, then charged at 4C constant current to the upper limit voltage, and then charged to full charge at constant voltage. The battery's constant current process charging capacity 1 and total charging capacity 2 are recorded. The constant current charging ratio is the charging capacity 1 divided by the total charging capacity 2.

[0144] (4) Lithium deposition test: The battery is charged at a high rate of 4.5C and disassembled after 20 cycles to observe the lithium deposition on the negative electrode surface. The criteria for judging lithium deposition on the negative electrode sheet are: 1) No lithium deposition, no white lithium metal deposition on the surface; 2) Lithium deposition on the top, bottom, and creases is marked as slight lithium deposition; 3) Lithium deposition on the entire surface is marked as severe lithium deposition.

[0145] Table 1

[0146]

[0147]

[0148] It can be seen from the examples and comparative examples in Table 1 that the addition of a toughening agent to the positive electrode sheet can significantly improve the fracture of the electrode sheet. At the same time, the content of the toughening agent in the positive electrode active layer, the conductivity of the positive electrode sheet, and the content of the thiophene compound and / or the derivative of the thiophene compound in the electrolyte are regulated within an appropriate range. The three work together to avoid fracture and / or damage of the electrode sheet while reducing the migration of the polyester compound toughening agent from the positive electrode side to the negative electrode side, thereby improving the high-rate charging performance and cycle performance of the battery.

[0149] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A battery, characterized in that: The battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one side of the positive electrode current collector, the positive electrode active layer includes a toughening agent, the toughening agent includes a polyester compound, and the weight content of the toughening agent in the positive electrode active layer is 0.25%-1%; The conductivity X of the positive electrode sheet is 10S / m-100S / m; The electrolyte includes additives, and the additives include thiophene compounds and / or derivatives of thiophene compounds. In the electrolyte, the weight content of the thiophene compounds and / or derivatives of thiophene compounds is 0.1%-1.5%.

2. The battery according to claim 1, characterized in that The thiophene compound and / or thiophene compound derivative includes a five-membered sulfur heterocycle; Preferably, the thiophene compound includes one or more structures represented by formula (I), and the derivative of the thiophene compound includes one or more structures represented by formula (II); wherein R1, R2, R3, R4, R5, R6, R7, and R8 are each independently selected from H, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted C6-C12 aryl, cyano, halogen, or boronic acid, and the substituted substituent is halogen; Preferably, R2 is selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C12 aryl, cyano, and the substituted substituent is halogen, and R3 is a boronic acid group; Preferably, the thiophene compound and / or the derivative of the thiophene compound includes at least one of 3-thiopheneboronic acid, thiophene-1,1-dioxide, 2-thiophenecarbonitrile, 2-methylthiophene, and benzothiophene.

3. The battery according to claim 1, characterized in that The diaphragm includes a carrier layer and a coating located on at least one side of the carrier layer, wherein the coating includes polymer particles, and the components of the polymer particles include polymethyl methacrylate; Preferably, the average particle size of the polymer particles is 1 μm-5 μm.

4. The battery according to claim 3, characterized in that The thickness of the coating is 0.5 μm-3 μm; And / or, the coating corresponds to the positive electrode sheet.

5. The battery according to claim 3, characterized in that The carrier layer includes a substrate layer and a ceramic layer, wherein the ceramic layer is located on one side or both sides of the substrate layer, and the ceramic layer includes inorganic particles, wherein the components of the inorganic particles include one or more of aluminum oxide, boehmite, silicon dioxide, zirconium dioxide, barium sulfate, magnesium hydroxide, fluorapatite, fluorphlogopite, mullite, aluminum titanate, copper oxide, titanium dioxide, and zinc oxide; Preferably, the thickness of the ceramic layer is 0.5 μm-3 μm.

6. The battery according to any one of claims 1 to 5, characterized in that The polyester compound includes dimethyl phthalate and / or diethyl phthalate; And / or, the positive electrode active layer includes a positive electrode conductive agent, and the positive electrode conductive agent includes carbon black and carbon nanotubes.

7. The battery according to claim 6, characterized in that The carbon nanotubes include multi-walled carbon nanotubes and / or single-walled carbon nanotubes; and / or, the carbon black comprises at least one of furnace black, acetylene black and Ketjen black; And / or, in the positive electrode active layer, the weight content of the carbon black is 0.3%-2.0%; And / or, the specific surface area of ​​the carbon black is 30-150m 2 / g, and the oil absorption value of the carbon black is not less than 300ml / 100g.

8. The battery according to claim 6, characterized in that The multi-walled carbon nanotubes include multi-walled carbon nanotubes with a length greater than 8 μm, and the weight content of the multi-walled carbon nanotubes with a length greater than 8 μm is not less than 50% based on the total weight of the multi-walled carbon nanotubes; And / or, the single-walled carbon nanotubes include single-walled carbon nanotubes with a length greater than 10 μm, and the weight content of the single-walled carbon nanotubes with a length greater than 10 μm is not less than 50% based on the total weight of the single-walled carbon nanotubes; And / or, the aspect ratio of the multi-walled carbon nanotubes is 100-3000, the average tube diameter of the multi-walled carbon nanotubes is 5nm-12nm, and the average length of the multi-walled carbon nanotubes is 10μm-15μm; And / or, the aspect ratio of the single-walled carbon nanotubes is 100-10000, the average tube diameter of the single-walled carbon nanotubes is 1 nm-3 nm, and the average length of the single-walled carbon nanotubes is 15 μm-25 μm.

9. The battery according to claim 8, characterized in that In the positive electrode active layer, the weight content of the multi-walled carbon nanotubes is 0.3%-2.0%, and the weight content of the single-walled carbon nanotubes is 0%-1%.

10. The battery according to any one of claims 7 to 9, characterized in that The positive electrode active layer includes a lithium cobalt oxide material, and the lithium cobalt oxide material is doped with at least one of Mg, Zr, La, Al, and Nb elements; Preferably, the median particle size Dv50 of the lithium cobalt oxide material is 8 μm-15 μm; Preferably, in the positive electrode active layer, the weight content of the lithium cobalt oxide material is 96%-98.7%.

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