A battery

Abstract

The present application relates to the technical field of battery, in particular to a battery. The battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, the separator comprises a substrate layer and a polymer coating layer, the polymer coating layer comprises a fluorine-containing polymer and first particles, the polymer coating layer has a porous structure formed by the fluorine-containing polymer; the adhesion F 1 between the separator and the positive electrode sheet is 20 N / m-40 N / m, the adhesion F 2 between the separator and the negative electrode sheet is 5 N / m-20 N / m; the electrolyte comprises a fluorine-containing solvent, the weight proportion a 1 of the fluorine-containing solvent in the electrolyte is 10%-70%, and the battery simultaneously satisfies the following relationship: F 1 / F 2 ≥1.5, 0.05≤a 1 / H 3 ≤0.43, H 3 is the thickness of the polymer coating layer of the separator adjacent to the positive electrode sheet. The battery of the present application can make the battery have both high resistance to heavy object impact performance and high thermal safety performance by regulating the adhesion distribution of the separator-pole sheet interface.

Description

Technical Field

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

[0002] In lithium-ion battery applications, battery safety remains a core challenge. Especially when portable electronic devices or power batteries experience external mechanical impacts (such as heavy object impacts), the interfacial stability between the separator and electrode plates is a key factor affecting battery failure. Traditional designs generally suffer from insufficient adhesion between the separator and electrode plates, leading to two major safety hazards: 1- Interface displacement causing internal short circuits: When the battery is impacted, insufficient adhesion between the separator and electrode plates causes relative slippage. The positive and negative electrode active material layers may come into contact due to displacement, triggering a local short circuit and instantaneous heat release, accelerating thermal runaway; 2- Positive electrode active particles detaching and piercing the separator: Low adhesion cannot effectively fix the positive electrode active material particles. During long-term charging and discharging or mechanical vibration, detached sharp particles can easily pierce the micron-thick separator under impact, causing direct conduction between the positive and negative electrodes. This not only triggers uncontrollable self-discharge but may also create current concentration at the puncture point, inducing localized high temperatures and gas evolution, ultimately leading to battery expansion, leakage, or even fire and explosion. Summary of the Invention

[0003] Currently, while attempts are being made to improve the adhesion strength of the separator coating, the differentiated requirements of the positive and negative electrode interfaces are often overlooked: simply increasing the overall adhesion strength limits the expansion and deformation space of the negative electrode and hinders electrolyte wetting, thus exacerbating the difficulty of thermal management. Therefore, how to precisely control the adhesion strength distribution at the separator-electrode interface has become a key bottleneck in balancing the impact resistance of heavy objects and thermal stability.

[0004] To address the issue of insufficient separator adhesion causing batteries to fail to simultaneously achieve high impact resistance and high thermal safety, this invention provides a battery. The battery of this invention can balance impact resistance and thermal stability by regulating the adhesive force distribution at the separator-electrode interface, thereby achieving both high impact resistance and high thermal safety.

[0005] To achieve the above objectives, the present invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The separator comprises a substrate layer and a polymer coating located on both sides of the substrate layer. The polymer coating comprises a fluoropolymer and first particles, and the polymer coating has a porous structure formed by the fluoropolymer. The adhesion force F between the separator and the positive electrode plate 1 The adhesion force F between the diaphragm and the negative electrode sheet is 20 N / m-40 N / m. 2The strength is 5 N / m to 20 N / m; the electrolyte includes a fluorinated solvent, and the weight percentage (a) of the fluorinated solvent in the electrolyte is... 1 The battery capacity is 10%-70%, and the battery simultaneously satisfies the following relationship: F 1 / F 2 ≥1.5, 0.05≤a 1 / H 3 ≤0.43, H 3 The thickness of the polymer coating adjacent to the positive electrode in the separator is expressed in μm.

[0006] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the battery of the present invention, a polymer coating with a porous structure is provided on both sides of the separator, and by controlling F 1 For 20N / m-40N / m, F 2 5N / m-20N / m, F 1 / F 2 A strength of ≥1.5 allows for differentiated bonding forces between the separator and the positive electrode, as well as between the separator and the negative electrode. By precisely adjusting the adhesive force distribution at the separator-electrode interface, the adhesive force on the positive electrode side is significantly greater than that on the negative electrode side. This not only ensures the rigid fixation of the positive electrode and the separator, mitigating or even preventing displacement of the positive electrode and separator when the battery is impacted, but also firmly holds the fragments of the positive electrode active particles in place, improving the stability of the positive electrode-separator interface, reducing the risk of positive electrode active particles detaching, and mitigating or even preventing them from falling and puncturing the separator. Furthermore, the weaker adhesive force on the negative electrode side allows for localized deformation of the negative electrode, reducing burrs caused by the breakage of the negative electrode current collector, lowering the risk of short circuits and fires caused by separator punctures, and improving the battery's resistance to heavy impacts.

[0007] However, excessively high adhesion on the positive electrode side hinders heat dissipation, reduces the high-temperature stability of the positive electrode active material, and leads to a deterioration in the battery's furnace temperature. The battery of this invention simultaneously controls a... 1 For 10%-70% and 0.05≤a 1 / H 3The concentration of fluorinated solvent (≤0.43) in the electrolyte results in a high content of fluorinated solvent. This fluorinated solvent exhibits good compatibility with the polymer coating of the separator, thereby improving the electrolyte wettability of the separator on the positive electrode side and increasing the electrolyte content between the positive electrode and the separator. The synergistic effect of the high electrolyte content between the positive electrode and the separator, combined with the porous structure of the polymer coating, enhances the heat dissipation performance on the positive electrode side. Furthermore, the abundant CF bonds between the separator and the electrode allow for the formation of LiF-rich interfacial films (CEI and SEI films) on the surfaces of both the positive and negative electrodes. These LiF-rich interfacial films exhibit high thermal stability, particularly reducing exothermic side reactions on the positive electrode side, thus further improving the battery's furnace temperature performance. Therefore, the battery of this invention balances the battery's impact resistance with its thermal stability, achieving both high impact resistance and high thermal safety.

[0008] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0009] 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

[0010] Figure 1 The image shown is a top view of a battery in one embodiment of the present invention, showing the positive electrode, negative electrode, and separator stacked together.

[0011] Figure 2 The diagram shown is a schematic cross-sectional view of the separator of a battery in one embodiment of the present invention. Detailed Implementation

[0012] 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 invention. Unless otherwise specified herein, data ranges include endpoints.

[0013] 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.

[0014] The present invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The separator comprises a substrate layer and a polymer coating located on both sides of the substrate layer. The polymer coating comprises a fluoropolymer and first particles, and the polymer coating has a porous structure formed by the fluoropolymer. The adhesion force F between the separator and the positive electrode plate 1 The adhesion force F between the diaphragm and the negative electrode sheet is 20 N / m to 40 N / m (e.g., 20 N / m, 23 N / m, 25 N / m, 28 N / m, 30 N / m, 33 N / m, 35 N / m, 38 N / m or 40 N / m). 2 The electrolyte has a strength of 5 N / m to 20 N / m (e.g., 5 N / m, 8 N / m, 10 N / m, 13 N / m, 15 N / m, 18 N / m, or 20 N / m); the electrolyte includes a fluorinated solvent, wherein the weight percentage a of the fluorinated solvent in the electrolyte is fluorinated. 1 For a concentration of 10%-70% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%), the battery simultaneously satisfies the following relationship: F 1 / F 2 ≥1.5 (e.g., 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10), 0.05≤a 1 / H 3 ≤0.43 (e.g., 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.43), H 3 The thickness of the polymer coating adjacent to the positive electrode in the separator is expressed in μm.

[0015] In the separator of the battery of the present invention, a polymer coating with a porous structure is provided on both sides of the substrate layer and F is controlled. 1 For 20N / m-40N / m, F 2 For 5N / m-20N / m and F 1 / F 2A strength of ≥1.5 ensures that the adhesion force on the positive electrode side is much greater than that on the negative electrode side. On the one hand, the stronger adhesion force on the positive electrode side can ensure that the positive electrode sheet and the separator are rigidly fixed, improving or even preventing the risk of displacement during impact. In addition, the high adhesion force can also firmly fix the fragments of the positive electrode active particles, improve the stability of the interface between the positive electrode and the separator, reduce the risk of positive electrode active particles falling off, and improve or even prevent them from falling off and puncturing the separator. On the other hand, the weaker adhesion force on the negative electrode side can allow the negative electrode sheet to undergo local deformation, which can locally adjust the stress direction on the negative electrode current collector, reduce the burrs caused by the breakage of the negative electrode current collector, reduce the risk of short circuit and fire caused by the separator being punctured, and improve the battery's resistance to heavy impact.

[0016] However, excessively high adhesion strength on the positive electrode side is detrimental to heat dissipation and can lead to a decrease in the battery's furnace temperature. To ensure that the positive electrode side has high adhesion strength while improving its heat dissipation performance, the battery of this invention also satisfies a. 1 For 10%-70% and 0.05≤a 1 / H 3 ≤0.43, at this point the electrolyte contains a large amount of fluorinated solvent. The CF bonds in the polymer coating of the separator and the CF bonds in the fluorinated solvent in the electrolyte have good compatibility. On the one hand, it can improve the electrolyte wettability of the separator on the positive electrode side, thereby improving the heat dissipation performance on the positive electrode side. On the other hand, it can also make the separator and the electrode contain abundant CF bonds, thereby forming a LiF-rich interface film on the surface of the positive and negative electrodes. This LiF-rich interface film (CEI film and SEI film) has high thermal stability (LiF has excellent thermal stability, melting point >800℃), especially it can reduce the exothermic side reaction on the positive electrode side, thereby further improving the furnace temperature performance of the battery.

[0017] In summary, the battery of the present invention, by providing a polymer coating with a porous structure on both sides of the separator, and by differentially adjusting the adhesion force F between the separator and the positive electrode, 1 and the adhesive force F between the diaphragm and the negative electrode sheet 2 At the same time, ensure that the electrolyte contains a large amount of fluorinated solvent to control the battery to meet: F 1 For 20N / m-40N / m, F 2 5N / m-20N / m, F 1 / F 2 ≥1.5, a 1 For 10%-70% and 0.05≤a 1 / H 3 With a density of ≤0.43, the battery can form an interface between the positive electrode and the separator that has both high adhesion and high heat dissipation, thereby balancing the battery's resistance to heavy impact and thermal stability, and enabling the battery to have both high resistance to heavy impact and high thermal safety performance.

[0018] In this invention, the adhesive force F between the separator and the positive electrode plate 1 and the adhesive force F between the diaphragm and the negative electrode sheet 2 This can be obtained through testing using the following methods: Adhesion force F 1 Test method: Place the battery in an environment of (25±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, discharge the battery completely (0% SOC) and dissect it. Select a 30mm long × 15mm wide separator and positive electrode sample along the tab direction. Place the separator and positive electrode at a 180-degree angle and test on a universal tensile testing machine at a speed of 100mm / min and a test displacement of 50mm. Record the maximum peel force obtained in the test as N. 1 Then the adhesive force F between the diaphragm and the positive electrode 1 =N 1 / 0.15 (unit: N / m).

[0019] Adhesion force F 2 Test method: Place the battery in an environment of (25±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, discharge the battery completely (0% SOC) and dissect it. Select a 30mm long × 15mm wide separator and negative electrode sample along the tab direction. Place the separator and negative electrode at a 180-degree angle on a universal tensile testing machine at a speed of 100mm / min and a test displacement of 50mm. Record the maximum peel force obtained in the test as N. 2 Then the adhesive force F between the diaphragm and the negative electrode 2 =N 2 / 0.15 (unit: N / m).

[0020] In this invention, the thickness H of the polymer coating adjacent to the positive electrode in the separator is... 3 The thickness of the polymer coating adjacent to the positive electrode in the membrane can be measured at each of the 10 test sites along the length of the membrane. The average value is taken as the final test result.

[0021] In this invention, by controlling the adhesion between the polymer coatings on both sides of the separator and the electrode, the weight ratio of the fluorinated solvent in the electrolyte, and the thickness of the polymer coating adjacent to the positive electrode in the separator, compared with the prior art, the problem that the battery cannot simultaneously achieve high resistance to heavy object impact and high thermal safety performance due to insufficient adhesion of the separator can be effectively improved, enabling the battery to have both high resistance to heavy object impact and high thermal safety performance. To further improve the effect, one or more of the technical features can be further optimized.

[0022] In some instances, the weight percentage a of the fluorinated solvent in the electrolyte is... 1 It is 45%-55% (e.g., 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%).

[0023] In some instances, the fluorinated solvent is selected from at least one of ethyl difluoroacetate, ethylene difluorocarbonate, ethylene fluorocarbonate, ethylene trifluoromethyl carbonate, ethylene fluoromethyl carbonate, ethyl fluoroacetate, and perfluorosulfonate.

[0024] In some instances, the fluorinated solvent comprises ethyl difluorocarbonate and at least one selected from the group consisting of: ethylene difluorocarbonate, ethylene fluorocarbonate, ethylene trifluoromethyl carbonate, fluoromethyl ethyl carbonate, ethyl fluorocarbonate, and perfluorosulfonate, wherein the weight percentage of ethyl difluorocarbonate is 50%-90% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%) based on the total mass of the fluorinated solvent.

[0025] In some instances, the ethyl difluoroacetate comprises one or more of ethyl 2,2-difluoroacetate and 2,2-difluoroethyl acetate.

[0026] In some instances, the electrolyte further includes a lithium salt, which includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorosulfonate imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0027] In some instances, the lithium salt comprises lithium bis(trifluoromethanesulfonyl)imide. Lithium bis(trifluoromethanesulfonyl)imide exhibits high thermal stability, which can further improve the thermal stability of the electrolyte, thereby further enhancing the thermal safety performance of the battery. However, when the weight percentage of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte is high, it can corrode the aluminum foil, leading to increased side reactions and ultimately affecting the thermal safety performance of the battery.

[0028] In some instances, the weight percentage of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte is 0.8%-8% (e.g., 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%). Controlling the weight percentage of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte allows the electrolyte to balance high thermal stability with low corrosivity to aluminum foil, thereby further improving the thermal safety performance of the battery.

[0029] In some instances, the lithium salt in the electrolyte accounts for 5%-30% by weight (e.g., 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%).

[0030] In some instances, the electrolyte includes lithium salts, organic solvents, and additives.

[0031] In some instances, the organic solvent includes fluorinated solvents.

[0032] In some instances, the organic solvent may also include a second solvent other than a fluorinated solvent. There are no particular requirements for the second solvent, which can be a solvent commonly used in the art. For example, the second solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0033] In some instances, the additive includes 1,2,4-butanetrionitrile.

[0034] In some instances, the additive may also include a second additive other than 1,2,4-butanetrionitrile. The second additive is not particularly required and may be a common additive in the art. For example, the second additive may include one or more of dinitrile compounds, cyclic sulfates, linear sulfates, linear sulfonates, cyclic sulfonates, linear sulfites, cyclic sulfites, linear sulfonates, cyclic sulfites, linear sulfones, and cyclic sulfones.

[0035] In some instances, the dinitrile compound includes at least one selected from adiponitrile, 1,2-bis(2-cyanoethoxy)ethane, butadionitrile, 1,4-dicyano-2-butene, 1,5-dicyanopentane, and 1,6-dicyanohexane. In some instances, the additive in the electrolyte accounts for 0.2%-30% by weight (e.g., 0.2%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%).

[0036] In some instances, the thickness H of the polymer coating in the separator adjacent to the positive electrode is... 3 The thickness is 1.5μm-4μm (e.g., 1.5μm, 1.8μm, 2μm, 2.3μm, 2.5μm, 2.8μm, 3μm, 3.3μm, 3.5μm, 3.8μm, or 4μm). It is understood that when the separator comprises a first portion and a second portion, wherein the first portion is a separator that does not contact either the positive or negative electrode, and the second portion is a separator that contacts both the positive and negative electrode, the thickness H of the polymer coating adjacent to the positive electrode in the separator... 3 This refers to the thickness of the polymer coating adjacent to the positive electrode in the second part of the separator.

[0037] According to some specific implementation methods, a 1 It ranges from 10% to 70%, H 3 The value is 1.5-4, and 0.05≤a. 1 / H 3 ≤0.43.

[0038] According to some specific implementation methods, a 1 It is 45%-55%, H 3 The value is 1.5-4, and 0.05≤a. 1 / H 3 ≤0.43.

[0039] In some instances, the fluoropolymer includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, and fluoroethylene-hexafluoropropylene copolymer.

[0040] In some instances, the battery also satisfies the following relationship: F 1 -F 2 ≥5N / m (e.g., 5N / m, 6N / m, 7N / m, 8N / m, 9N / m, 10N / m, 11N / m, 12N / m, 13N / m, 14N / m or 15N / m).

[0041] In some instances, the fluoropolymer accounts for 35%-70% (e.g., 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%) of the total weight of the polymer coating, and the first particle accounts for 30%-65% (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%) of the total weight of the polymer coating.

[0042] In some instances, the polymer coatings on both sides of the substrate layer may be the same or different. It is understood that differences in the polymer coatings on both sides of the substrate layer can refer to one or more differences in the specific selection of the fluoropolymer, the coating thickness, the weight percentage of the fluoropolymer in the polymer coating, the composition of the first particle, the particle size of the first particle, the morphology of the first particle, and the content of the first particle.

[0043] In some instances, the first particle comprises one or more of the following: alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, boron nitride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, and guanine.

[0044] In some instances, the porosity of the substrate layer is 30%-60% (e.g., 30%, 35%, 40%, 45%, 50%, 55% or 60%).

[0045] In this invention, the porosity of the substrate layer is measured by the following method: the battery is disassembled, the separator is removed, and the polymer coating on the surface of the substrate layer is removed. When the residual amount of polymer coating on the surface of the substrate layer is less than 5%, it is considered as obtaining a test sample of the substrate layer. Alternatively, the original substrate layer without polymer coating is used as a test sample. The test sample is tested in accordance with the standard "GB / T-36363-2018 Polyolefin Separator for Lithium-ion Batteries" to obtain the porosity of the substrate layer.

[0046] In some instances, the thickness of the substrate layer is 4μm-12μm (e.g., 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm).

[0047] In some instances, the substrate layer comprises one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

[0048] In some instances, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector, the positive active layer including a positive active material and a positive binder.

[0049] In some instances, the positive electrode active material includes lithium cobalt oxide particles or lithium cobalt oxide particles that have been doped with two or more elements from Al, Ni, Mn, Mg, Zn, Ti, Zr, and F.

[0050] In some instances, the positive electrode binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-acrylonitrile copolymer, polyurethane, polyimide, polyacrylic acid, polytetrafluoroethylene, perfluorosulfonic acid ionomer, and polyacrylonitrile.

[0051] In some instances, the positive electrode active material accounts for 90%-99% of the total weight of the positive electrode active layer (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%), and the positive electrode binder accounts for 0.5%-8% of the total weight of the positive electrode active layer (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%).

[0052] In some instances, the positive electrode active layer also includes a positive electrode conductive agent.

[0053] In some instances, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, graphene, and acetylene black.

[0054] In some instances, the weight percentage of the positive electrode conductive agent is 0.5%-8% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%), based on the total weight of the positive electrode active layer.

[0055] In some instances, the first particle comprises at least magnesium hydroxide, with the Mg content ranging from 6.5% to 26.5% by mass (e.g., 6.5%, 8%, 10%, 12%, 15%, 18%, 19%, 21%, 23%, 25%, 26.5%) based on the total weight of the polymer coating. The positive electrode comprises a positive electrode active material, which is lithium cobalt oxide. The lithium cobalt oxide includes dopant elements, including magnesium, with the magnesium content ranging from 6.5% to 26.5% by mass based on the total weight of the dopant elements. The electrolyte comprises 1,2,4-butanetrionitrile, with a content of 6%-40% (e.g., 6%, 10%, 15%, 20%, 25%, 30%, 35% or 40%). The weight percentage of the 1,2,4-butanetrionitrile is 0.2%-4.3% (e.g., 0.2%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, 1.7%, 2%, 2.2%, 2.5%, 2.7%, 3%, 3.2%, 3.5%, 3.7%, 4% or 4.3%).

[0056] Doping lithium cobalt oxide with magnesium, whose ion radius is similar to that of lithium ions, suppresses the harmful transformation of lithium cobalt oxide from a hexagonal crystal system to a monoclinic or spinel phase, maintaining the structural integrity of lithium cobalt oxide. Furthermore, magnesium doping significantly increases the oxygen vacancy formation energy of lithium cobalt oxide, delaying the side reactions of cobalt dissolution and oxygen evolution at high temperatures, thereby improving the high-temperature stability of lithium cobalt oxide. Magnesium hydroxide in the separator coating effectively neutralizes HF, preventing HF corrosion of the positive electrode surface and further enhancing the high-temperature stability of lithium cobalt oxide. 1,2,4-Butanetrionitrile can form a stable CEI film on the surface of lithium cobalt oxide, further improving its high-temperature stability. Compared to dinitrile compounds, 1,2,4-Butanetrionitrile has lower viscosity and desolvation energy, simultaneously improving the heat dissipation performance on the positive electrode side. Therefore, by simultaneously controlling the mass content of Mg in the polymer coating, the mass content of magnesium in the lithium cobalt oxide dopant, and the weight percentage of 1,2,4-butanetrionitrile in the electrolyte, the high-temperature stability of the positive electrode active material can be improved through the synergistic effect of the above three factors, while further enhancing the thermal safety performance of the battery.

[0057] In this invention, the mass content of magnesium in the dopant elements of lithium cobalt oxide can be tested using ICP, SEM combined with EDS. When using ICP, the lithium cobalt oxide particles are digested to prepare a test solution. Under set test conditions, the content of each element in the solution is quantitatively tested, and the mass percentage of magnesium in the impurity elements is calculated. When using EDS, a surface scan or point scan is performed on a selected area containing lithium cobalt oxide particles in the positive electrode active material layer to obtain the content of each element, and the mass percentage of magnesium in the impurity elements is calculated.

[0058] In this invention, the content of Mg element is obtained by using SEM combined with EDS, based on the total weight of the polymer coating. Specifically, a surface scan is performed on the surface of the polymer coating to obtain the mass percentage of magnesium element.

[0059] In some instances, along the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface facing away from each other, the first surface including a plurality of recesses, and the second surface including a plurality of protrusions corresponding to the recesses.

[0060] In this invention, the protrusions and the recesses can be obtained using conventional techniques in the art, for example, by using an embossing roller (with protrusions) through an embossing process.

[0061] In some instances, the shape of the protrusion includes one or more of the following: circular, elliptical, and polygonal.

[0062] In some instances, the height H of the protrusion 4The height is 3μm-50μm (e.g., 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm). In this invention, the height of the protrusion is specified as the maximum vertical distance from any point on the top of the protrusion to the surface of the positive electrode in the thickness direction of the positive electrode.

[0063] In some instances, the height H of the protrusion 4 The range is 4μm-30μm.

[0064] In some instances, the width of the protrusion is 0.85mm-8mm (e.g., 0.85mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, or 8mm). In this invention, the width of the protrusion refers to the maximum distance between any two points on the edge line of the protrusion.

[0065] In some instances, the width of the protrusion is 1mm-3.5mm.

[0066] In some instances, the spacing between adjacent protrusions is 1mm-8mm (e.g., 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, or 8mm). In this invention, the spacing between adjacent protrusions refers to the minimum distance between the edge lines of two adjacent protrusions.

[0067] In some instances, the spacing between adjacent protrusions is 2mm-4mm.

[0068] In some instances, the shape of the recess includes one or more of the following: circular, elliptical, and polygonal.

[0069] In some instances, the depth of the recess is 3μm-50μm (e.g., 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm). In this invention, the depth of the recess is specified as the maximum vertical distance from any point at the bottom of the recess to the surface of the positive electrode in the thickness direction of the positive electrode.

[0070] In some instances, the width of the recess is 0.85mm-8mm (e.g., 0.85mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, or 8mm). In this invention, the width of the recess refers to the maximum distance between any two points on the edge line of the recess.

[0071] In some instances, the spacing between adjacent recesses is 1mm-8mm (e.g., 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, or 8mm). In this invention, the spacing between adjacent recesses refers to the minimum distance between the edge lines of two adjacent recesses.

[0072] In this invention, the height of the protrusion and the depth of the concave portion can be obtained by testing the following method: taking the "height of the protrusion" as an example, when the number of protrusions is greater than 1, the height of the protrusion is the average depth. For example, when the number of protrusions is less than or equal to 20, the height of the protrusion is the average height of all the protrusions; when the number of protrusions is greater than 20, the height of the protrusion is the average height of any 20 protrusions.

[0073] In this invention, the width of the protrusion and the width of the concave can be obtained by testing the following method: taking the "width of the protrusion" as an example, when the number of protrusions is greater than 1, the width of the protrusion is the average width. For example, when the number of protrusions is less than or equal to 20, the width of the protrusion is the average width of all the protrusions; when the number of protrusions is greater than 20, the width of the protrusion is the average width of any 20 protrusions.

[0074] In this invention, the spacing between adjacent protrusions and the spacing between adjacent recesses can be obtained by testing the following method: Taking the "spacing between adjacent protrusions" as an example, when the number of protrusions is greater than 2, the spacing between adjacent protrusions is the average spacing between adjacent protrusions. For example, when the number of protrusions is less than or equal to 20, the spacing between adjacent protrusions is the average of the spacing between all adjacent protrusions; when the number of protrusions is greater than 20, the spacing between adjacent protrusions is the average of the spacing between adjacent protrusions of any 20 protrusions.

[0075] In this invention, the width of the protrusion, the height of the protrusion, the spacing between the protrusions of the line, the width of the concave part, the depth of the concave part, and the spacing between adjacent concave parts can all be obtained by 3D profilometer or SEM test.

[0076] In some instances, the separator 1 includes a first portion 11 and a second portion 12, wherein the separator 1 of the first portion 11 is a separator 1 that does not contact either the positive electrode 3 or the negative electrode 2, and the separator 1 of the second portion 12 is a separator that contacts both the positive electrode 3 and the negative electrode 2. It is understood that, as... Figure 1 As shown, the diaphragm between the two thick blue dashed lines is the first part 11 of the diaphragm, and the diaphragm framed by the thin red dashed line is the second part 12 of the diaphragm.

[0077] In some instances, the compression ratio b of the diaphragm1 For 15%-50% (e.g., 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%), where b 1 =(H 1 -H 2 ) / H 2 H 1 The average thickness of the diaphragm in the first part is expressed in μm, H. 2 The average thickness of the diaphragm in the second part, in μm (e.g.) Figure 2 (As shown). When the compression ratio of the separator meets the above range, the battery can effectively delay the impact process when subjected to heavy impact, thereby reducing the damage to the internal electrodes of the cell during the heavy impact, and thus improving the battery's resistance to heavy impact.

[0078] In some instances, the battery satisfies the following relationship: 10 ≤ H 4 / b 1 ≤200 (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200). By controlling the battery to satisfy the above relationship, and by adjusting the matching degree between the height of the protrusion and the compression ratio of the separator, displacement between the positive electrode and the separator can be reduced or even prevented, and a certain amount of local deformation space can be provided for the positive electrode side, thereby absorbing impact energy and further improving the battery's resistance to heavy object impacts.

[0079] In some instances, the battery satisfies the following relationship: 12 ≤ H 4 / b 1 ≤150.

[0080] In some instances, the negative electrode sheet includes a negative current collector and a negative active layer located on at least one side of the surface of the negative current collector. The negative active layer includes a negative active material, which includes one or more of carbon-based materials and silicon-based materials.

[0081] In some instances, the thickness of the negative electrode current collector is 8 μm-14 μm (e.g., 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm).

[0082] In some instances, the thickness of the negative electrode current collector is 10 μm-12 μm.

[0083] In some instances, the Dv90 of the silicon-based material is 9.5 μm-11 μm (e.g., 9.5 μm, 9.8 μm, 10 μm, 10.3 μm, 10.5 μm, 10.8 μm, or 11 μm), and / or, the sphericity of the silicon-based material is 0.8-1 (e.g., 0.8, 0.83, 0.85, 0.88, 0.9, 0.93, 0.95, 0.98, or 1). This reduces or even prevents the risk of silicon-based particles puncturing the diaphragm when expanding at high temperatures, further improving the high-temperature cycling voltage drop.

[0084] In this invention, the sphericity of the silicon-based material can be tested by the following method: A surface particle image of the negative electrode active layer is captured using a scanning electron microscope (SEM). In the image, within an arbitrarily selected 100μm × 100μm area, silicon-based material particles are identified using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The radius r1 of the equivalent circle representing the projected perimeter of a single silicon-based material particle and the radius r2 of the equivalent circle representing the projected area of ​​the silicon-based material particle are calculated. The sphericity of a single silicon-based material particle is calculated as r2 / r1. The sphericity of 100 silicon-based material particles is averaged. This process is repeated 5 times, and the average value is the final test result.

[0085] In this invention, the Dv90 of the silicon-based material is the particle size corresponding to the cumulative particle size distribution reaching 90% in the volumetric particle size distribution of the silicon-based material. In this invention, the volumetric particle size distribution of the silicon-based material can be obtained by arbitrarily selecting a 100μm × 100μm area from an SEM image taken at 10000x magnification on the surface of the negative electrode active layer, and then measuring and statistically processing it using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv90 of the silicon-based material can also be obtained by testing with a laser particle size analyzer; for example, before preparing the negative electrode sheet, the Dv90 of the silicon-based material can be measured using a laser particle size analyzer.

[0086] In some instances, the weight percentage of the silicon-based material in the negative electrode active material is 1%-100% (e.g., 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%).

[0087] In some instances, the carbon-based material in the negative electrode active material accounts for 0%-99% by weight (e.g., 0, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%).

[0088] In some instances, the silicon-based material includes one or more of elemental silicon particles, silicon-carbon particles, silicon-oxygen particles, and silicon alloy particles; In some instances, the carbon-based material includes one or more of graphite and hard carbon.

[0089] In some instances, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder.

[0090] In some instances, the negative electrode conductive agent includes one or more of conductive carbon black, graphene, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0091] In some instances, the negative electrode binder includes one or more of polyurethane, polyacrylic acid, acrylic-acrylonitrile copolymer, acrylonitrile-vinylidene fluoride copolymer, acrylate polymers, sodium carboxymethyl cellulose, styrene-butadiene latex, and fluoropolymers.

[0092] In some instances, based on the total weight of the negative electrode active layer, the weight percentage of the negative electrode active material is 80%-98% (e.g., 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, or 98%), the weight percentage of the negative electrode conductive agent is 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%), and the weight percentage of the negative electrode binder is 0.5%-18% (e.g., 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, or 18%).

[0093] In some instances, the battery is a lithium-ion rechargeable battery.

[0094] 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.

[0095] The following examples illustrate the battery of the present invention.

[0096] Example 1 (1) Diaphragm A fluoropolymer (vinylidene fluoride-hexafluoropropylene copolymer) and the first particle (composed of magnesium hydroxide) were mixed at a weight ratio of 60:40. The mixed solids were added to a DMAC at a solid content of 10%, and stirred at 1500 rpm until the vinylidene fluoride-hexafluoropropylene copolymer dissolved, yielding a polymer coating slurry. This polymer coating slurry was then applied to both sides of a substrate layer (polyethylene) to form a polymer coating. After drying in an oven, a diaphragm was obtained. The fluoropolymer comprised 60% of the polymer coating by weight, the first particle comprised 40% by weight, and the magnesium element in the polymer coating was measured to be 16.5% by weight.

[0097] (2) Positive electrode plate The positive electrode active material (lithium cobalt oxide, with magnesium accounting for 15% of the mass of the doping elements in lithium cobalt oxide), the positive electrode binder (polyvinylidene fluoride (PVDF)), and the positive electrode conductive agent (acetylene black) were mixed at a weight ratio of 98.2:0.8:1. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto both sides of an aluminum foil with a thickness of 10 μm. The coated aluminum foil was baked in an oven at five different temperature gradients (95℃±5℃, 100℃±5℃, 103℃±5℃, 100℃±5℃, 95℃±5℃), and then rolled and slit to obtain the desired positive electrode sheet. Several recesses were formed on the first surface and the second surface of the positive electrode sheet through an embossing process.

[0098] (3) Negative electrode plate The negative electrode active material (graphite and silicon oxide compound in a weight ratio of 93:7, with a sphericity of 0.96 for silicon oxide particles), negative electrode conductive agent (single-walled carbon nanotubes (SWCNT)), and negative electrode binder (containing 0.5 parts by weight of lithium carboxymethyl cellulose (CMC-Li), 1.5 parts by weight of styrene-butadiene rubber (SBR), and 1 part by weight of lithium polyacrylate (PAA-Li)) were mixed in a weight ratio of 96.5:0.5:3. The mixture was prepared by a wet process (water was added to the above mixture, and the mixture was stirred under vacuum until it became a homogeneous and fluid negative electrode slurry). The slurry was coated on both sides of the negative electrode current collector (copper foil), dried (temperature: 85℃, time: 5h), rolled, and die-cut to obtain the negative electrode sheet.

[0099] (4) Electrolyte Ingredient preparation: Lithium salt: 12.5 parts by weight of lithium hexafluorophosphate, 4.5 parts by weight of lithium bis(trifluoromethanesulfonyl)imide; Organic solvent: 79.2 parts by weight, of which 50 parts by weight are fluorinated solvent (2,2-difluoroethyl acetate and FEC, of ​​which 2,2-difluoroethyl acetate accounts for 75% by weight) and 29.2 parts by weight are second solvent (propylene carbonate, ethyl propionate and propyl propionate are mixed in a volume ratio of 4:10:10 to form the second solvent). Additives: 1.5 parts by weight of 1,2,4-butanetrionitrile, 2.3 parts by weight of adiponitrile; In an argon-filled glove box (moisture content <10ppm, oxygen content <1ppm), organic solvents are mixed evenly to obtain mixed solution 1. Additives are added to mixed solution 1 to obtain mixed solution 2. Lithium bis(trifluoromethanesulfonyl)imide and lithium salt are slowly added to mixed solution 2 and stirred evenly to obtain a non-aqueous electrolyte.

[0100] (5) Preparation of lithium-ion batteries The positive electrode sheet prepared in step (2), the separator prepared in step (1), and the negative electrode sheet prepared in step (3) are alternately stacked and stacked in a Z-shaped stacking method to form a stack core. After the stack core is injected with electrolyte (injected with the electrolyte in step (4)), packaged, and hot-pressed, a lithium-ion battery is obtained.

[0101] Among them, the adhesion force F between the separator and the positive electrode plate 1 The adhesion force F between the separator and the negative electrode is 28.7 N / m. 2 If it is 13.2 N / m, then F 1 / F 2 =28.7 / 13.2=2.17, the thickness H of the polymer coating adjacent to the positive electrode in the separator. 3 The average thickness H of the first part of the diaphragm is 2 μm. 1 The average thickness H of the second part of the diaphragm is 10 μm. 2 8μm, b 1 =(H 1 -H 2 ) / H 2 =25%, the width of the convex part is 2mm, and the height of the convex part is H. 4 25μm, H 4 / b 1 =25 / 25%=100, a 1 / H 3 =50% / 2=0.25.

[0102] Example 2 group Example 2a The procedure was carried out in accordance with Example 1, except that the adhesive force F between the separator and the positive electrode was [not specified]. 1 The adhesion force F between the separator and the negative electrode is 39.6 N / m. 2If it is 19.8 N / m, then F 1 / F 2 =39.6 / 19.8=2, the weight percentage of fluoropolymer in the polymer coating is 70%, the weight percentage of the first particle (alumina and magnesium hydroxide) is 30%, the weight percentage of Mg in the polymer coating is 6.8%, and the thickness H of the polymer coating adjacent to the positive electrode in the separator is... 3 The average thickness H of the first part of the diaphragm is 1.5 μm. 1 The average thickness H of the second part of the diaphragm is 9 μm. 2 It is 6.1 μm, b 1 =(H 1 -H 2 ) / H 2 =47.54%, the width of the protrusion is 0.85mm, and the height H of the protrusion is... 4 5μm, H 4 / b 1 =5 / 47.54%=10.52, the magnesium content in the lithium cobalt oxide doping element is 6.2% by weight, the fluorinated solvent in the electrolyte accounts for 55% by weight, and 2,2-difluoroethyl acetate accounts for 90% of the fluorinated solvent. 1 / H 3 =55% / 1.5=0.37, the weight percentage of 1,2,4-butanetrionitrile in the electrolyte is 4.3%, the weight percentage of lithium bis(trifluoromethanesulfonylimide) in the electrolyte is 8%, and the sphericity of the silicon-based particles is 0.8.

[0103] Example 2b The procedure was carried out in accordance with Example 1, except that the adhesive force F between the separator and the positive electrode was [not specified]. 1 The adhesion force F between the separator and the negative electrode is 19.3 N / m. 2 If it is 5.7 N / m, then F 1 / F 2 =19.3 / 5.7=3.39, the weight percentage of fluoropolymer in the polymer coating is 35%, the weight percentage of the first particle (magnesium hydroxide) is 65%, the weight percentage of Mg in the polymer coating is 26.5%, and the thickness H of the polymer coating adjacent to the positive electrode in the separator is... 3 The average thickness H of the first part of the diaphragm is 1.7 μm. 1 The average thickness H of the second part of the diaphragm is 11 μm. 2 It is 9.5μm, b 1 =(H 1 -H 2 ) / H 2 =15.79%, the width of the convex part is 8mm, and the height of the convex part is H. 4 3μm, H 4 / b1 =3 / 15.79%=19, the magnesium content in the lithium cobalt oxide doping elements is 39.8% by weight, the fluorinated solvent in the electrolyte accounts for 70% by weight, and 2,2-difluoroethyl acetate accounts for 50% of the fluorinated solvent. a 1 / H 3 =70% / 1.7=0.41, the weight percentage of 1,2,4-butanetrionitrile in the electrolyte is 0.2%, the weight percentage of lithium bis(trifluoromethanesulfonylimide) in the electrolyte is 0.8%, and the sphericity of the silicon-based particles is 0.98.

[0104] Example 2c The procedure was carried out in accordance with Example 1, except that the adhesive force F between the separator and the positive electrode was [not specified]. 1 The adhesion force F between the separator and the negative electrode is 19.7 N / m. 2 If it is 12.7 N / m, then F 1 / F 2 =19.7 / 12.7=1.55, the thickness H of the polymer coating adjacent to the positive electrode in the separator. 3 The diameter is 2μm, the width of the protrusion is 1mm, and the height of the protrusion is H. 4 30μm, H 4 / b 1 =30 / 25%=120, the fluorinated solvent is adjusted to FEC, the weight percentage of 2,2-difluoroethyl acetic acid in the fluorinated solvent is 0, and the weight percentage of the fluorinated solvent in the electrolyte is 10%. 1 / H 3 =10% / 2=0.05.

[0105] Example 2d The procedure was carried out in accordance with Example 1, except that the fluoropolymer was changed to polyvinylidene fluoride, and the thickness H of the polymer coating adjacent to the positive electrode in the separator was increased. 3 The average thickness H of the first part of the diaphragm is 4 μm. 1 The diameter is 10μm, the width of the protrusion is 3.5mm, and the height H of the protrusion is... 4 50μm, H 4 / b 1 =50 / 25%=200, the weight percentage of fluorinated solvent in the electrolyte is 45%, a 1 / H 3 =45% / 4=0.11.

[0106] Example 3 Group This set of examples illustrates the effects that occur when the composition of the first particle changes.

[0107] Example 3a The procedure was carried out in accordance with Example 1, except that the first particle was composed of aluminum oxide.

[0108] Example 3b The procedure was carried out in accordance with Example 1, except that the first particle was composed of melamine cyanurate.

[0109] Example 4 group This set of examples illustrates the effects of changes in the mass content of Mg in the polymer coating, the mass content of magnesium in the lithium cobalt oxide dopant, and the weight percentage of 1,2,4-butanetrionitrile in the electrolyte. Specifically, the mass content of Mg in the polymer coating is changed by adjusting at least one of the specific selection of the first particle and the weight percentage of the first particle in the polymer coating.

[0110] Example 4a The experiment was conducted in accordance with Example 1, except that, based on the total weight of the polymer coating, the mass content of Mg was 6.3%, based on the total weight of the doped elements, the mass content of magnesium was 4.7%, and based on the total weight of the electrolyte, the weight percentage of 1,2,4-butanetrionitrile was 0.1%.

[0111] Example 4b The experiment was conducted in accordance with Example 1, except that, based on the total weight of the polymer coating, the mass content of Mg was 26.5%, based on the total weight of the doped elements, the mass content of magnesium was 41.8%, and based on the total weight of the electrolyte, the weight percentage of 1,2,4-butanetrionitrile was 4.8%.

[0112] Example 5 group This set of examples illustrates the effects of changing the weight percentage of lithium bis(trifluoromethanesulfonylimide) in the electrolyte by adjusting the weight percentage of the second solvent in the electrolyte.

[0113] Example 5a The same procedure was followed as in Example 1, except that the weight percentage of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte was 0.5%.

[0114] Example 5b The same procedure was followed as in Example 1, except that the weight percentage of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte was 9%.

[0115] Example 6 The same procedure was followed as in Example 1, except that the sphericity of the silicon-based particles was 0.75.

[0116] Example 7 group This set of examples is used to illustrate when a 1 / H 3 The impact of changes.

[0117] Example 7a The procedure is carried out in accordance with Example 1, except that H 3 It is 1μm, a1 is 30%, a 1 / H 3 =30% / 1=0.3.

[0118] Example 7b The procedure is carried out in accordance with Example 1, except that H 3 It is 4.5μm, a1 is 60%, a 1 / H 3 =60% / 4.5=0.13.

[0119] Example 8 The experiment was conducted in accordance with Example 1, except that the weight percentage of ethyl difluoroacetate in the fluorinated solvent was 95%, and the weight percentage of the fluorinated solvent in the electrolyte was 50%.

[0120] Example 9 group This set of examples is used to illustrate when H 4 / b 1 The impact of changes.

[0121] This embodiment group is carried out with reference to Embodiment 1, except that H is adjusted. 4 and / or b 1 Change H 4 / b 1 For details, please refer to Table 1-1.

[0122] Table 1-1 Example 10 The experiment was carried out in accordance with Example 1, except that the first particle in the polymer coating on the side corresponding to the positive electrode was composed of aluminum oxide, and the first particle in the polymer coating on the side corresponding to the negative electrode was composed of magnesium hydroxide.

[0123] Comparative Example 1 The procedure was carried out in accordance with Example 1, except that the fluoropolymer was replaced with the same amount of aramid by weight.

[0124] Comparative Example 2 The process was carried out in accordance with Example 1, except that the preparation process of the polymer coating was adjusted to disperse fluoropolymer particles in water to form a polymer coating slurry.

[0125] Comparative Examples 3-7 The procedure is carried out in accordance with Example 1, except that F is adjusted. 1 and / or F 2 See Table 1-2 for details.

[0126] Table 1-2 Comparative Examples 8-11 The procedure is carried out in accordance with Example 1, except that a is adjusted. 1 and / or H 3 See Table 1-2 for details.

[0127] Test case The batteries prepared in the examples and comparative examples were subjected to the following tests.

[0128] 1. Impact test The battery was discharged at 0.7C to 3V, then charged at 0.7C to 4.52V, and finally charged at 0.05C. A metal rod with a diameter of 15.8mm ± 0.2mm was then placed horizontally on the upper surface of the wide geometric center of the fully charged battery. A weight of 9.1kg ± 0.1kg was dropped from a height of 610mm ± 25mm onto the metal rod, concentrating the impact force on the central area of ​​the battery. After the test, the battery was observed for 6 hours, and the battery status was recorded. Each example and comparative example tested 50 battery samples. If the battery did not explode and / or catch fire, it was considered a "pass"; if it exploded or caught fire, it was considered a "fail". The result was expressed as "number of passes P / 50T". For example, "90P / 50T" means all passed, and "10P / 50T" means 10 out of 50 batteries passed.

[0129] The results are recorded in Table 2.

[0130] 2. 135℃ Hot Box Test The lithium-ion batteries were placed at 25℃±3℃ and charged at a constant current of 1C to the upper limit voltage (4.52V). Then, they were charged at a constant voltage of 4.52V to 0.05C and left to stand for 2 hours. The lithium-ion batteries were then heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min, and the temperature was increased to (135±1)℃. The temperature was maintained for 60 minutes before the test was ended. The battery status was recorded. 30 battery samples were tested for each example and comparative example. If the battery did not explode and / or catch fire, it was considered "passed". If it exploded or caught fire, it was considered "failed". The result was expressed as "number of passes / 30". For example, "30 / 30" means all passed, and "10 / 30" means 10 out of 30 batteries passed.

[0131] The results are recorded in Table 2.

[0132] 3. High-temperature storage voltage drop test The lithium-ion battery was placed at 25℃±2℃ and charged to full capacity (100% SOC) at a constant current of 0.2C. After standing for 2 hours, it was discharged to 3V at a constant current of 0.2C and left to stand for 5 hours. It was then charged to full capacity (100% SOC) at a constant current of 0.2C and the voltage at this point was recorded as V1. After standing at 85℃ for 4 hours, the voltage after 4 hours was recorded as V2. The voltage drop was (V1-V2) / 4.

[0133] The results are recorded in Table 2.

[0134] Table 2 As can be seen from Table 2, by comparing the comparative examples and the embodiments, it can be seen that the battery prepared in the embodiments has significantly improved resistance to heavy object impacts, significantly improved resistance to hot box impacts, and significantly reduced high-temperature cycling voltage drop. This indicates that by controlling the adhesion between the polymer coatings on both sides of the separator and the electrode, the weight ratio of fluorinated solvent in the electrolyte, and the thickness of the polymer coating adjacent to the positive electrode in the separator, the battery can have both high resistance to heavy object impacts and high thermal safety performance.

[0135] 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 positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode. The separator includes a substrate layer and a polymer coating located on both sides of the substrate layer. The polymer coating includes a fluoropolymer and first particles, and the polymer coating has a porous structure formed by the fluoropolymer. The adhesion force F between the separator and the positive electrode plate 1 The adhesion force F between the diaphragm and the negative electrode sheet is 20 N / m-40 N / m. 2 The strength is 5 N / m to 20 N / m; the electrolyte includes a fluorinated solvent, and the weight percentage (a) of the fluorinated solvent in the electrolyte is... 1 The battery capacity is 10%-70%, and the battery simultaneously satisfies the following relationship: F 1 / F 2 ≥1.5, 0.05≤a 1 / H 3 ≤0.43, H 3 The thickness of the polymer coating adjacent to the positive electrode in the separator is expressed in μm.

2. The battery according to claim 1, wherein, The weight percentage a of the fluorinated solvent in the electrolyte 1 It is 45%-55%; And / or, the fluorinated solvent is selected from at least one of ethyl difluoroacetate, ethylene difluorocarbonate, ethylene fluorocarbonate, ethylene trifluoromethyl carbonate, ethylene fluoromethyl carbonate, ethyl fluoroacetate, and perfluorosulfonate. And / or, the thickness of the polymer coating in the separator adjacent to the positive electrode is 1.5 μm-4 μm; And / or, the fluoropolymer includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, and fluoroethylene-hexafluoropropylene copolymer; And / or, the first particle comprises one or more of the following: alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, boron nitride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, and guanine.

3. The battery according to claim 2, wherein, The weight percentage of the ethyl difluoroacetate is 50%-90% based on the total mass of the fluorinated solvent. And / or, the ethyl difluoroacetate includes one or more of ethyl 2,2-difluoroacetate and 2,2-difluoroethyl acetate; And / or, the first particle comprises at least magnesium hydroxide, and the mass content of the Mg element is 6.5%-26.5% based on the total weight of the polymer coating; the positive electrode comprises a positive electrode active material, which is lithium cobalt oxide, and the lithium cobalt oxide comprises doping elements, including magnesium, and the mass content of the magnesium element is 6%-40% based on the total weight of the doping elements; the electrolyte comprises 1,2,4-butanetrionitrile, and the weight percentage of the 1,2,4-butanetrionitrile is 0.2%-4.3% based on the total weight of the electrolyte.

4. The battery according to claim 1, wherein, The battery also satisfies the following relationship: F 1 -F 2 ≥5N / m; And / or, based on the total weight of the polymer coating, the fluoropolymer accounts for 35%-70% by weight, and the first particle accounts for 30%-65% by weight; And / or, the polymer coatings on both sides of the substrate layer may be the same or different.

5. The battery according to claim 1, wherein, Along the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface facing away from each other. The first surface includes a plurality of recesses, and the second surface includes a plurality of protrusions, with the protrusions corresponding to the recesses. The separator comprises a first part and a second part. The first part of the separator is a separator that does not contact either the positive or negative electrode plate, while the second part of the separator is a separator that contacts both the positive and negative electrode plates. The compression ratio b of the separator is... 1 It ranges from 15% to 50%, of which b 1 =(H 1 -H 2 ) / H 2 H 1 The average thickness of the diaphragm in the first part is expressed in μm, H. 2 The average thickness of the diaphragm in the second part is expressed in μm.

6. The battery according to claim 5, wherein, The battery satisfies the following relationship: 10≤H 4 / b 1 ≤200, where H 4 The height of the protrusion is in μm; And / or, the height H of the protrusion 4 The range is 3μm-50μm; And / or, the width of the protrusion is 0.85m. m -8mm; And / or, the spacing between adjacent protrusions is 1. m m-8mm; And / or, the depth of the recess is 3μm-50μm; And / or, the width of the recess is 0.85mm-8mm; And / or, the spacing between adjacent recesses is 1mm-8mm.

7. The battery according to claim 6, wherein, The battery satisfies the following relationship: 12≤H 4 / b 1 ≤150; And / or, the height H of the protrusion 4 The thickness ranges from 4μm to 30μm. And / or, the width of the protrusion is 1mm-3.5mm; And / or, the spacing between adjacent protrusions is 2mm-4mm.

8. The battery according to claim 1, wherein, The porosity of the substrate layer is 30%-60%; And / or, the thickness of the substrate layer is 4μm-12μm; And / or, the composition of the substrate layer includes one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

9. The battery according to claim 1, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, which includes one or more of carbon-based materials and silicon-based materials. Preferably, the thickness of the negative electrode current collector is 8μm-14μm, more preferably 10μm-12μm; Preferably, the Dv90 of the silicon-based material is 9.5-11 μm, and / or the sphericity of the silicon-based material is 0.8-1; Preferably, the silicon-based material accounts for 1%-100% of the weight of the negative electrode active material; Preferably, the silicon-based material includes one or more of elemental silicon particles, silicon-carbon particles, silicon-oxygen particles, and silicon alloy particles; Preferably, the carbon-based material includes one or more of graphite and hard carbon.

10. The battery according to claim 1, wherein, The electrolyte also includes lithium salts, which include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorosulfonate imide, and lithium bis(trifluoromethanesulfonyl)imide. Preferably, the weight percentage of lithium bis(trifluoromethanesulfonylimide) in the electrolyte is 0.8%-8%.

Images