Electrochemical apparatus and electronic device

Abstract

Provided in the present application are an electrochemical apparatus and an electronic device. The electrochemical apparatus of the present application comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and at least one positive electrode active material layer, and the negative electrode sheet comprises a negative electrode current collector and at least one negative electrode active material layer; the length of the longest negative electrode active material layer is x1, and the length of the shortest positive electrode active material layer is x2, where 0.1%≤(x1-x2) / x1≤30%; in a Raman spectrum of the negative electrode active material, the D-band intensity is ID, and the G-band intensity is IG, where y=ID / IG, and 0.2≤y≤0.8; the electrolyte contains z% of 1,3-propane sultone, y and z satisfying: 0.02≤y / z≤160. The electrochemical apparatus in the present application has good rate capability, and further is not prone to side reactions at the interface of the electrochemical apparatus, thereby achieving a low thickness expansion rate after multiple low-temperature cycles.

Description

An electrochemical device and electronic device Technical Field

[0001] This application relates to the field of energy storage, and more specifically, to an electrochemical device and an electronic device. Background Technology

[0002] Electrochemical devices such as lithium-ion batteries are widely used in portable electronic products, electric vehicles, aerospace, and energy storage due to their advantages such as high energy density, good cycle performance, safety, environmental friendliness, and lack of memory effect. As the application of lithium-ion batteries in electric vehicles and other electric transportation tools becomes more widespread, there is a need for lithium-ion batteries to have good rate performance; however, current methods to improve the rate performance of lithium-ion batteries often lead to increased thickness expansion after multiple low-temperature cycles. Summary of the Invention

[0003] This application provides an electrochemical device and an electronic device. The electrochemical device in this application not only has good rate performance, but also can effectively suppress the thickness expansion of the electrochemical device after multiple low-temperature cycles.

[0004] In a first aspect, this application provides an electrochemical device comprising an electrolyte, and a positive electrode, a separator, and a negative electrode sequentially stacked thereon. The positive electrode includes a positive current collector, and at least one surface of the positive current collector is provided with a positive active material layer. The negative electrode includes a negative current collector, and at least one surface of the negative current collector is provided with a negative active material layer, wherein the length of the negative active material layer is greater than the length of the positive active material layer; the longest negative active material layer has a length of x1, the shortest positive active material layer has a length of x2, and 0.1% ≤ (x1-x2) / x1 ≤ 30%; the negative active material layer includes a negative active material, and the peak intensity of the D peak in the Raman spectrum of the negative active material is I. D The peak strength of G is I G y = I D / I G , 0.2≤y≤0.8; the electrolyte includes 1,3-propanesulfonate lactone, the mass content of 1,3-propanesulfonate lactone in the electrolyte is z%, 0.02≤y / z≤160.

[0005] In the above technical solution, by limiting the proportion by which the length of the negative electrode active material layer exceeds the length of the positive electrode active material layer to 0.1% ≤ (x1-x2) / x1 ≤ 30%, the negative electrode active material layer has sufficient space to accommodate lithium ions during high-rate charging of the electrochemical device, and lithium deposition at the interface of the negative electrode sheet is not easily achieved, thereby improving the rate performance of the electrochemical device. Furthermore, the peak intensity ratio of the D peak and G peak in the Raman spectrum of the negative electrode active material is I... D / I GA value between 0.2 and 0.8 indicates a relatively large surface lattice defect degree in the negative electrode active material, which is beneficial for rapid lithium-ion insertion, thereby improving the rate performance of the negative electrode active material. However, the inventors discovered that because the region of the negative electrode active material layer extending beyond the positive electrode active material layer experiences less lithium-ion insertion and extraction during the formation process, it is difficult to form a sufficient SEI film (SEI stands for Solid Electrolyte Interface) in this region, resulting in a large thickness expansion rate during low-temperature cycling. Based on this, the inventors discovered that adding a certain amount of 1,3-propanesulfonate lactone to the electrolyte, along with I₂ within a specific range... D / I G The peak intensity ratio is matched so that the ratio of peak intensity ratio to 1,3-propanesulfonate content is in the range of 0.02 to 160, which makes it easier to form a more uniform and stable SEI film during the formation process. This reduces the occurrence of side reactions of electrolyte at the interface, and can improve the problem of high low-temperature thickness expansion rate in the region where the negative electrode active material layer exceeds the positive electrode active material layer while achieving high rate performance of electrochemical device.

[0006] In one possible implementation, the electrochemical device satisfies at least one of the following conditions: (1) both the upper and lower surfaces of the negative electrode current collector are provided with negative electrode active material layers, and the two negative electrode active material layers have the same length; (2) both the upper and lower surfaces of the positive electrode current collector are provided with positive electrode active material layers, and the two positive electrode active material layers have the same length.

[0007] In one possible implementation, the electrochemical device satisfies at least one of the following conditions: (1) 1% ≤ (x1-x2) / x1 ≤ 20%; (2) 0.2 ≤ y ≤ 0.6; (3) 0.005 ≤ z ≤ 10; (4) 0.067 ≤ y / z ≤ 60.

[0008] In the above technical solution, the rate performance of the electrochemical device can be improved, and the thickness expansion rate after multiple low-temperature cycles is less obvious.

[0009] In one possible implementation, the electrochemical device satisfies at least one of the following conditions: (1) 1% ≤ (x1-x2) / x1 ≤ 15%; (2) 0.01 ≤ z ≤ 3.

[0010] In the above technical solution, the thickness expansion rate of the electrochemical device after multiple low-temperature cycles can be further suppressed.

[0011] In one possible implementation, the negative electrode sheet includes multiple negative electrode tabs, which are integrally formed with the negative current collector; and / or, the positive electrode sheet includes multiple positive electrode tabs, which are integrally formed with the positive current collector.

[0012] In the above technical solution, setting multiple tabs on the negative electrode and / or positive electrode can provide more transport channels for ions and electrons, thereby improving the rate performance and fast charging performance of the electrochemical device.

[0013] In one possible implementation, the average volumetric particle size D of the negative electrode active material V 50 ranges from 5μm to 15μm.

[0014] In the above technical solution, the Dv50 of the negative electrode active material is within a suitable range, which can avoid the decrease in lithium-ion diffusion rate caused by excessively large negative electrode material particles, and reduce the increase in electrolyte side reactions caused by excessively small particles due to excessive specific surface area. This is beneficial to further improve the rate performance of the electrochemical device and the thickness expansion after multiple low-temperature cycles.

[0015] In one possible implementation, the electrolyte further includes a compound of formula I, the structural formula of which is shown in formula (I) below:

[0016] Among them, R 21 R 22 R 23 and R 24 Each is independently selected from hydrogen atoms, halogen atoms, cyano groups, and substituted or unsubstituted C1 to C2 atoms. 10 Alkyl, substituted or unsubstituted C2 to C3 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne group, substituted or unsubstituted C1 to C2 10 Any one of the heteroatom-containing functional groups, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 R 22 R 23 and R 24 A ring can be formed between any two groups in Formula I; the mass content of the compound in the electrolyte is 0.001% to 1%.

[0017] In the above technical solution, the compound of formula I contains silicon, which can form an SEI film on the electrode interface of the electrochemical device, which is beneficial to suppress the thickness expansion rate of the electrochemical device after multiple low-temperature cycles.

[0018] In one possible implementation, the compound of formula I includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilane) maleate, tetraallylsilane, pentamethylpentavinylcyclopentasiloxane, vinylmethylsilyl(diol) diacetate, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethylenedisiloxane, triacetoxyethylsilane, trivinylmethylsilane, triethylvinylsilane, triethylsilylacetylene, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, or vinyltriethoxysilane.

[0019] In one possible implementation, the electrolyte further includes a cyclic carbonate compound, which includes at least one of ethylene carbonate and propylene carbonate, and the cyclic carbonate compound has a mass content of 5% to 40% in the electrolyte.

[0020] In the above technical solutions, cyclic carbonates have strong solubility, which is beneficial to improving the solubility of lithium salts in the electrolyte, thereby improving the kinetic performance of the electrochemical device.

[0021] In one possible implementation, the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, or soft carbon.

[0022] In the above technical solution, the inventors discovered that when the negative electrode active material includes natural graphite, artificial graphite, hard carbon, and soft carbon, the effect of the electrochemical device in suppressing expansion is particularly obvious.

[0023] In one possible implementation, the electrochemical device is a wound structure, which includes a positive electrode, a separator, and a negative electrode arranged in sequence and wound together.

[0024] Secondly, this application provides an electronic device that includes the aforementioned electrochemical device. Therefore, the electronic device provided by this application has good performance.

[0025] The beneficial effects of this application are:

[0026] This application provides an electrochemical device and an electronic device. The electrochemical device includes an electrolyte, and a positive electrode, a separator, and a negative electrode sequentially stacked. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The length of the negative active material layer is greater than the length of the positive active material layer. The longest negative active material layer has a length of x1, and the shortest positive active material layer has a length of x2, where 0.1% ≤ (x1-x2) / x1 ≤ 30%. The negative active material layer includes a negative active material, and the peak intensity of the D peak in the Raman spectrum of the negative active material is I. D The peak strength of G is I G y = I D / I G The electrolyte contains 1,3-propanesulfonate lactone, with a mass content of z% in the electrolyte, and 0.02 ≤ y / z ≤ 160. In the electrochemical device of this application, the length of the negative electrode active material layer exceeds the length of the positive electrode active material layer by a ratio between 0.1% and 30%, while the Ig of the negative electrode active material… D / I G The value is controlled within the range of 0.2 to 0.8, and I is controlled. D / I G The ratio of the content of 1,3-propanesulfonate lactone added to the electrolyte is 0.02 to 160, which can make the negative electrode plate interface form a stable and uniform SEI film during the fast charging process, suppress the probability of side reactions of the electrolyte at the interface, and improve the problem of high low-temperature thickness expansion rate of the negative electrode active material layer in the region where it exceeds the positive electrode active material layer in the electrochemical device while achieving high-rate fast charging performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 is a schematic diagram of an electrode with active material layers of the same length on both the upper and lower sides.

[0029] Figure 2 is a schematic diagram of an electrode with different lengths of active material layers on the upper and lower sides. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are clearly and completely described below in conjunction with the accompanying drawings and embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] The electrochemical devices and electronic devices according to embodiments of this application will be described in detail below.

[0032] In a first aspect, this application provides an electrochemical device comprising a negative electrode, an electrolyte, a positive electrode, and a separator, wherein the positive electrode, the separator, and the negative electrode are sequentially stacked and wound to form a wound structure; the positive electrode comprises a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, and the negative electrode comprises a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector.

[0033] In this application, the length of the positive electrode active material layer is less than the length of the negative electrode active material layer; and in both the positive and negative electrode sheets, the length of the negative electrode active material layer is x1, and the length of the positive electrode active material layer is x2, with 0.1% ≤ (x1-x2) / x1 ≤ 30%, preferably 1% to 20%, more preferably 1% to 15%; for example, (x1-x2) / x1 can be 0.1%, 0.8%, 1%, 6%, 10%, 15%, 18%, 20%, 24%, 27%, 30%, etc., or within a range consisting of any two of the above values. By controlling the proportion by which the length of the negative electrode active material layer exceeds the length of the positive electrode active material layer within the above range, the negative electrode active material layer has sufficient space to accommodate lithium ions, making it easier to achieve high-rate performance of the electrochemical device, reducing the probability of the negative electrode active material layer delaminating beyond the positive electrode active material layer during multiple low-temperature cycles, and further ensuring that the energy density of the electrochemical device is not lost.

[0034] In this application, the length x1 of the negative electrode active material layer ranges from 70 mm to 230 mm.

[0035] It should be noted that when both the upper and lower surfaces of the positive and negative current collectors are provided with negative / positive active material layers, the lengths of the active material layers on the upper and lower surfaces can be the same or slightly different. Figure 1 shows an electrode structure where the active material layers on both surfaces are the same length, and Figure 2 shows an electrode structure where the active material layers on the upper and lower surfaces are different lengths. When the lengths of the positive active material layers on the upper and lower surfaces of the positive current collector are different, the length of the shortest positive active material layer is taken as x2; when the lengths of the negative active material layers on the upper and lower surfaces of the negative current collector are different, the length of the longest negative active material layer is taken as x1.

[0036] As an example, in a specific embodiment of this application, a positive active material layer is provided on both the upper and lower surfaces of the positive current collector, and a negative active material layer is also provided on both the upper and lower surfaces of the negative current collector; moreover, the lengths of the two negative active material layers are the same, and the lengths of the two positive active material layers are also the same.

[0037] Of course, in other embodiments of this application, when active material layers are provided on both the upper and lower surfaces of the same current collector in the electrochemical device, the lengths of the active material layers can also be different; for example, the lengths of the two negative electrode active material layers can be different, but the lengths of the two positive electrode active material layers can be the same; the lengths of the two positive electrode active material layers can be different, but the lengths of the two negative electrode active material layers can be the same; or the lengths of the two negative electrode active material layers can be different, and the lengths of the two positive electrode active material layers can also be different. Furthermore, only one positive electrode active material layer and / or only one negative electrode active material layer can be provided. For ease of explanation, this application only uses the following example: "Both the upper and lower surfaces of the positive electrode current collector are provided with positive electrode active material layers, and both the upper and lower surfaces of the negative electrode current collector are also provided with negative electrode active material layers, and the lengths of the two negative electrode active material layers are the same, and the lengths of the two positive electrode active material layers are also the same." Other solutions will not be elaborated upon; however, for those skilled in the art, other solutions are also included within the scope of protection of this application. Furthermore, in this application, "the length of the negative electrode active material layer is greater than the length of the positive electrode active material layer" means that, along the winding direction, the length of the negative electrode active material layer is greater than the length of the positive electrode active material layer. Therefore, when the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in sequence, along the winding direction, at least one end of the negative electrode active material layer extends beyond the positive electrode active material layer. This could be the beginning end of the winding, the end end of the winding, or both the beginning and end ends. This application does not have any particular limitation here, as long as it can meet the purpose of this application.

[0038] Furthermore, the negative electrode active material layer of this application includes a negative electrode active material, and in the Raman spectrum of the negative electrode active material of this application, the peak intensity of the D peak is I. D The peak strength of G is I G y = I D / I G , 0.2≤y≤0.8. Where 1340cm -1 Up to 1370cm -1 The inner peak is peak D, 1570cm -1 Up to 1590cm -1The peak within the image is the G peak. In the negative electrode active material, the intensity ratio of the D peak to the G peak represents the defect degree of the negative electrode active material. When the defect degree y is in the range of 0.2 to 0.8, it indicates that the defect degree of the negative electrode active material is relatively large, which is conducive to the rapid insertion of active ions, thereby improving the rate performance of the negative electrode active material. In addition, the inventors also found that when the negative electrode active material includes natural graphite, artificial graphite, hard carbon, or soft carbon, the effect of inhibiting expansion of the electrochemical device is particularly significant.

[0039] However, the inventors discovered that because the length of the negative electrode active material layer is greater than that of the positive electrode active material layer, fewer lithium insertion / extraction reactions occur in the region where the negative electrode active material layer extends beyond the positive electrode active material layer (hereinafter referred to as the "extended region") during the formation of the electrochemical device. This results in insufficient formation of the interfacial protective film in the extended region, making it easier for other components such as carbonates in the electrolyte to undergo side reactions in the extended region. The inventors further discovered that when the electrolyte contains 1,3-propanesulfonate lactone, 1,3-propanesulfonate lactone can preferentially and rapidly form an SEI film in the extended region. This reduces the likelihood of side reactions in the extended region, preventing interface deterioration in the extended region of the negative electrode sheet and effectively suppressing the thickness expansion of the electrochemical device after multiple low-temperature cycles. Furthermore, although a higher defect rate of the negative electrode active material can improve the rate performance of the electrochemical device, other active components in the electrolyte are more likely to undergo side reactions with the negative electrode active material, which also deteriorates the interfacial performance of the electrode sheet, leading to a higher expansion rate of the electrochemical device after multiple cycles. The inventors discovered that when the mass content of 1,3-propanesulfonate lactone in the electrolyte is z%, and y and z satisfy 0.02 ≤ y / z ≤ 160, the side reactions of other components in the electrolyte and the negative electrode active material can be well suppressed, and the interface of the negative electrode sheet of the electrochemical device is less likely to deteriorate. This also effectively suppresses the thickness expansion of the electrochemical device after multiple low-temperature cycles. Therefore, when the electrochemical device in this application contains 1,3-propanesulfonate lactone, and the defect degree y of the negative electrode active material and the content z% of 1,3-propanesulfonate lactone satisfy 0.02 ≤ y / z ≤ 160, the interface of the protruding area of ​​the negative electrode active material layer and the area overlapping with the positive electrode active material layer is less likely to deteriorate, thereby effectively suppressing the thickness expansion of the electrochemical device after multiple low-temperature cycles. In some embodiments of this application, y is preferably 0.2 to 0.6; or z is preferably 0.005 to 10, more preferably 0.01 to 3; or y / z is preferably 0.067 to 60. Specifically, y can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., or within the range of any two of the above values; z can be 0.005, 0.01, 0.04, 0.1, 0.7, 1.4, 2.5, 3, 6.8, 10, etc., or within the range of any two of the above values; y / z can be 0.02, 0.04, 0.067, 0.5, 1.4, 6.5, 10.2, 30.2, 40.5, 60, 100, 120, 155, 160, or within the range of any two of the above values.

[0040] In addition to the features mentioned above, the positive electrode, negative electrode, and electrolyte also have other structures and features, as detailed below:

[0041] Negative electrode sheet

[0042] In some embodiments of this application, the average volumetric particle size D of the negative electrode active material V The particle size is 5μm to 15μm. This avoids the decrease in lithium-ion diffusion rate caused by excessively large negative electrode material particles, and also reduces the increase in electrolyte side reactions caused by excessively small particles due to their large specific surface area. This is beneficial for further improving the rate performance of the electrochemical device and the thickness expansion after multiple low-temperature cycles.

[0043] In some embodiments of this application, the negative electrode sheet includes multiple negative electrode tabs, which are integrally formed with the negative electrode current collector. "Multiple negative electrode tabs" means that the number of negative electrode tabs is not less than two. Providing multiple negative electrode tabs on the negative electrode sheet can offer more transport channels for ions and electrons, thereby improving the fast charging performance and rate capability of the electrochemical device. The multiple negative electrode tabs are formed by die-cutting the negative electrode current collector.

[0044] In some embodiments, the negative electrode active material layer typically also contains a negative electrode conductive agent. This application does not particularly limit the type of negative electrode conductive agent, as long as it achieves the purpose of this application. For example, negative electrode conductive agents include, but are not limited to, at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots, or graphene.

[0045] In some embodiments, the negative electrode active material layer may also contain a negative electrode binder and a thickener. This application does not impose any particular limitation on the types of negative electrode binders and thickeners, as long as they can achieve the purpose of this application. For example, the negative electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, or acrylated styrene-butadiene rubber; the thickener in the negative electrode slurry may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0046] In the negative electrode sheet, the material of the negative electrode current collector includes, but is not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal, etc., and this application does not have any particular limitations. Among them, the conductive metal includes, but is not limited to, copper, nickel, or titanium, and the material of the polymer substrate includes, but is not limited to, at least one of polyethylene, polypropylene, ethylene propylene copolymer, polyethylene terephthalate, polyethylene terephthalate, or poly(p-phenylene terephthalamide).

[0047] Furthermore, this application does not impose any particular limitations on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode active material layer is 30 μm to 160 μm.

[0048] In preparing the negative electrode sheet, the components of the aforementioned negative electrode active material layer can be dissolved or dispersed in a liquid solvent to form a negative electrode slurry. This slurry is then coated onto a negative electrode current collector and dried, thereby forming a negative electrode active material layer on the current collector, thus obtaining the negative electrode sheet. When preparing the negative electrode sheet using this method, there are no particular limitations on the solvent in the negative electrode slurry, as long as it can dissolve or disperse the aforementioned components. Specifically, the solvent in the negative electrode slurry includes any of the following: aqueous solvents and organic solvents. Aqueous solvents include, but are not limited to, mixtures of alcohol and water or water itself. Organic solvents include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. In some other embodiments, when using aqueous solvents, the negative electrode slurry composition may also include a thickener and styrene-butadiene rubber (SBR) emulsion to slurry the negative electrode slurry, thereby adjusting its viscosity. The types of thickeners in the negative electrode slurry include, but are not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. In addition, when preparing the negative electrode sheet, the various components in the negative electrode active material layer can be dry-mixed to form a sheet, and then the resulting sheet can be pressed onto the negative electrode current collector.

[0049] electrolyte

[0050] The electrolyte of this application may also include a compound of formula I:

[0051] Formula (I)

[0052] Among them, R 21 R 22 R 23 and R 24 Each is independently selected from hydrogen atoms, halogen atoms, cyano groups, and substituted or unsubstituted C1 to C2 atoms. 10 Alkyl, substituted or unsubstituted C2 to C3 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne group, substituted or unsubstituted C1 to C2 10 Any one of the heteroatom-containing functional groups, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 R 22 R23 and R 24 A ring can be formed between any two groups in Formula I; the mass content of Formula I compound in the electrolyte is 0.001% to 1% (hereinafter referred to as b% to indicate the mass content of Formula I compound). Specifically, Formula I compound includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilane) maleate, tetraallylsilane, pentamethylpentavinylcyclopentasiloxane, vinylmethylsilane(diol) diacetate, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethylenedisiloxane, triacetoxyethylsilane, trivinylmethylsilane, triethylvinylsilane, triethylsilylacetylene, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, or vinyltriethoxysilane. An appropriate amount of compound I can form an SEI film on the electrode interface of an electrochemical device, which helps to suppress the thickness expansion rate of the electrochemical device after multiple cycles.

[0053] In some embodiments of this application, the electrolyte further includes a cyclic carbonate compound, which includes at least one of ethylene carbonate and propylene carbonate. The mass content of the cyclic carbonate compound in the electrolyte is 5% to 40% (hereinafter, c% represents the mass content of the cyclic carbonate compound). The cyclic carbonate compound has strong solubility, which is beneficial to improving the solubility of lithium salt in the electrolyte, thereby improving the kinetic performance of the electrochemical device.

[0054] In addition, in some embodiments of this application, the electrolyte further includes lithium salt additives, specifically including at least one of lithium difluorophosphate, lithium difluorobis(oxalate)phosphate, lithium tetrafluoro(oxalate)phosphate, lithium di(oxalate)borate, lithium tetrafluoroborate, or lithium difluoro(oxalate)borate; and based on the mass of the electrolyte, the mass content of the lithium salt additive is h%, and the value of h ranges from 0.005 to h ≤ 2.

[0055] In some embodiments of this application, the electrolyte may further include lithium salts and non-aqueous solvents. This application does not impose any particular limitation on lithium salts, as long as they achieve the purpose of this application. For example, lithium salts may include, but are not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or Li2SiF6. This application does not impose any particular limitation on the content of lithium salts in the electrolyte, as long as they achieve the purpose of this application. For example, based on the mass of the electrolyte, the mass percentage of lithium salts is 8% to 15%. This application does not impose any particular limitation on non-aqueous solvents, as long as they achieve the purpose of this application. For example, non-aqueous solvents may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, other cyclic carbonate compounds, or fluorocarbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), dipropyl carbonate (DPC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The remaining cyclic carbonates may include, but are not limited to, at least one of butyl carbonate (BC) or vinyl ethylene carbonate (VEC). Fluorinated carbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1,2-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved.

[0056] Positive electrode sheet

[0057] In some embodiments of this application, the positive electrode sheet includes multiple positive electrode tabs, which are integrally formed with the positive current collector. Similar to the negative electrode sheet, "multiple positive electrode tabs" means that the number of positive electrode tabs is not less than two. Providing multiple positive electrode tabs on the positive electrode sheet can provide more transport channels for ions and electrons, thereby improving the fast charging performance and rate performance of the electrochemical device. The multiple positive electrode tabs are formed by die-cutting the positive current collector.

[0058] The positive electrode active material layer comprises a positive electrode active material, which can be any material capable of reversibly inserting and de-inserting Li. + Na + Substances containing alkali metal ions are used to ensure the normal charging and discharging of the electrochemical device. For example, positive electrode active materials include, but are not limited to, at least one of lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium nickel oxide, and ternary materials. Ternary materials include, but are not limited to, LiNi x Co y Mn z O2, LiNi x Co y Al z At least one of O2, etc., and the contents of Ni, Co, Mn, Al, etc., can be adjusted to ensure that x+y+z=1. For example, the ternary material can be LiNi. 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.88 Co 0.1 Al 0.02 O2, etc.

[0059] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent; this application does not limit the type of positive electrode conductive agent, and any known conductive material can be used. Specifically, the positive electrode conductive agent includes, but is not limited to, at least one of the following: acetylene black, Super-P carbon black, or amorphous carbon such as needle coke, or carbon nanotubes, or graphene.

[0060] In some embodiments, the positive electrode active material layer generally also contains a positive electrode binder. There are no particular restrictions on the type of positive electrode binder used in the manufacture of the positive electrode active material layer. In the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used in the electrode manufacturing process is acceptable. Positive electrode binders include, but are not limited to, any one or at least two of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene-styrene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ion conductivity of alkali metal ions (especially lithium ions).

[0061] In the positive electrode sheet, there are no particular restrictions on the type of positive current collector; it can be any known material suitable for use as a positive current collector. Materials for the positive current collector include, but are not limited to, metals such as aluminum, stainless steel, nickel plating, titanium, and tantalum. Furthermore, to reduce the electronic contact resistance between the positive current collector and the positive active material layer, conductive additives or conductive coatings can be applied to the surface of the positive current collector. Conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver. The conductive coating can be a mixture of inorganic oxides, conductive agents, and positive electrode binders.

[0062] Furthermore, similar to the preparation of the negative electrode, the preparation of the positive electrode can be achieved either by preparing a positive electrode slurry, coating the slurry onto a positive electrode current collector, and drying it to form a positive electrode active material layer on the current collector, thus obtaining the positive electrode sheet; or by dry mixing the components of the positive electrode active material layer to form a sheet, which is then pressed onto the positive electrode current collector to form the positive electrode active material layer, thereby obtaining the positive electrode sheet. Specifically, the solvents in the positive electrode slurry include, but are not limited to, N-methylpyrrolidone (NMP) and ethylene carbonate (EC).

[0063] Separating membrane

[0064] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0065] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator material can be resin, glass fiber, inorganic materials, etc., formed from materials stable to the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of resin or glass fiber separator materials include, but are not limited to, polyolefins, aromatic polyamides, polyimide (PI), polyamide (PA), polytetrafluoroethylene, polyethersulfone, spandex, or aramid. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0066] The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0067] Inorganic materials include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The forms of inorganic materials include, but are not limited to, particulate or fibrous forms.

[0068] The separator can be in the form of a thin film, including but not limited to non-woven fabric, woven fabric, and microporous membranes. In the thin film form, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separators, the following separators can also be used: separators formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or negative electrode, for example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0069] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. When the thickness of the separator is within the above ranges, insulation and mechanical strength can be ensured, and the rate capability and energy density of the electrochemical device can be ensured.

[0070] In this application, the separator may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. This application does not particularly limit the aforementioned inorganic particles, and may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the aforementioned binder, and may include at least one of the aforementioned binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0071] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, the separator, the negative electrode, and the electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the aforementioned other components. This application does not have any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0072] Secondly, this application also provides an electronic device that includes an electrochemical device according to this application.

[0073] The application of the electrochemical device described in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device described in this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0074] Example

[0075] The following uses a lithium-ion battery as an example to illustrate the implementation of the electrochemical device of this application in more detail through embodiments and comparative examples. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0076] Test methods and equipment:

[0077] Ratio Performance Test

[0078] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 1C to a voltage of 4.3V, and then charged at a constant voltage of 4.3V until the current was less than or equal to 0.05C. Subsequently, it was discharged at constant currents of 1C and 5C to 2.5V, respectively, and the 1C and 5C discharge capacities were obtained. Dividing the 5C discharge capacity by the 1C discharge capacity gives the 5C capacity retention rate; a higher 5C capacity retention rate indicates better rate performance.

[0079] Low temperature short-term performance test thickness expansion rate

[0080] The lithium-ion battery was placed in a high-low temperature chamber, and the temperature was adjusted to 25°C. It was left to stand for 30 minutes to allow the battery to reach a constant temperature. Once at constant temperature, the battery was discharged at a constant current of 0.2C until the voltage reached 2.5V. The thickness of the battery was recorded as the initial thickness. Next, the temperature of the high-low temperature chamber was adjusted to -10°C, and the battery was left to stand for 3 hours to allow the temperature to match the ambient temperature. At -10°C, the battery was charged at a constant current of 0.5C until the voltage reached 4.3V, then charged at a constant voltage of 4.3V until the current was less than or equal to 0.02C. It was left to stand for 60 minutes, then discharged at a constant current of 0.2C until the voltage reached 2.5V, and left to stand for another 60 minutes. This constituted one charge-discharge cycle, which was repeated 10 times. Adjust the high and low temperature chamber temperature to 25℃, and let the lithium-ion battery stand for 3 hours to allow its temperature to match the ambient temperature. Charge it to 4.3V at a current of 0.3C, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.02C. Let it stand for 30 minutes, then remove the lithium-ion battery and observe and measure its thickness, recording it as the thickness after the test. Calculate the thickness expansion rate of the lithium-ion battery and use it as an indicator to evaluate the short-term low-temperature performance of the lithium-ion battery.

[0081] Low-temperature short-term performance test thickness expansion rate = (thickness after test - initial thickness) / initial thickness × 100%.

[0082] Raman spectral determination

[0083] The determination of the Raman spectrum of the negative electrode active material in this application needs to meet the following test conditions:

[0084] When determining the Raman spectrum, the test temperature is between 10℃ and 30℃, and it is usually stabilized at room temperature (i.e., 25℃). A 532nm or 633nm laser source is used to test the negative electrode active material (this application uses a 633nm laser source, and preheating is performed for 15 minutes before testing). The wavenumber center range is 150–3000 cm⁻¹. -1 .

[0085] Example 1-1

[0086] <Preparation of Electrolyte>

[0087] In an argon-atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate, propylene carbonate, and diethyl carbonate (DEC) were mixed thoroughly to obtain a base solvent. Fully dried lithium salt LiPF6 and 1,3-propanesulfonate lactone were dissolved in the base solvent and mixed thoroughly to obtain an electrolyte. Based on the mass of the electrolyte, the mass content of lithium salt LiPF6 was 12.5%, the mass content of 1,3-propanesulfonate lactone is shown in Table 1, the mass content of ethylene carbonate was 20%, the mass content of propylene carbonate was 5%, and the balance was diethyl carbonate.

[0088] <Preparation of the positive electrode>

[0089] LiMn, the positive electrode active material 0.6 Fe 0.4 PO4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred under vacuum until a homogeneous positive electrode slurry with a solid content of 75 wt% was formed. The positive electrode slurry was uniformly coated onto a 12 μm thick aluminum foil for the positive electrode current collector and dried at 85 °C. The above steps were repeated on the other surface of the positive electrode current collector. After cold pressing, a double-sided coated positive electrode sheet with a thickness of 100 μm was obtained. After cutting and slitting, the sheet was dried under vacuum at 105 °C for 4 hours to obtain a positive electrode sheet with a size of 74 mm × 867 mm for later use. The length of the positive active material layer on both surfaces of the positive electrode current collector is the same, and the length of the positive material layer x2 is 69.93 mm.

[0090] <Preparation of Negative Electrode Sheets>

[0091] Artificial graphite (negative electrode active material), Super P (conductive agent), and sodium carboxymethyl cellulose (negative electrode binder) were mixed in a mass ratio of 92:2:6. Deionized water was added and the mixture was stirred until homogeneous, yielding a negative electrode slurry with a solid content of 70 wt%. The negative electrode slurry was uniformly coated onto one surface of an 8 μm thick copper foil current collector, and then dried at 110 °C. The above steps were repeated on the other surface of the current collector. After cold pressing, a double-sided coated negative electrode sheet with a single-sided negative electrode material layer thickness of 150 μm was obtained, and the compaction density of the single-sided negative electrode material layer was 1.6 g / cm³. 3 After being cut and slit, the material is dried under vacuum at 105℃ for 4 hours to obtain a negative electrode with dimensions of 75mm×865mm for later use. The negative electrode active material layer on both surfaces of the negative electrode current collector has the same length, and the length x1 of the negative electrode material layer is 70mm.

[0092] <Isolation membrane>

[0093] Polyethylene (PE) porous polymer film is used as the separator.

[0094] <Preparation of Electrochemical Devices>

[0095] The prepared positive electrode, separator, negative electrode, and separator are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, shaping, and capacity testing.

[0096] Examples 1-2 to Examples 1-9

[0097] Apart from adjusting the value of (x1-x2) / x1 according to Table 1, this value is mainly adjusted by changing the length of x2, and the rest is the same as in Example 1-1.

[0098] Examples 1-10 to Examples 1-17

[0099] Except for adjusting the values ​​of y and z according to Table 1, the rest is the same as in Examples 1-5.

[0100] Examples 1-18 to Examples 1-21

[0101] Except for adjusting the material of the negative electrode active material according to Table 1, the rest is the same as in Examples 1-5.

[0102] Comparative Examples 1 to 4

[0103] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1.

[0104] Table 1

[0105] In Table 1, the length of the extended region in Comparative Example 1 is relatively small, resulting in poor rate performance. In Comparative Example 2, the length of the extended region is relatively large, leading to a higher low-temperature thickness expansion rate of the electrochemical device, which also negatively impacts rate performance. In Comparative Example 3, the y / z ratio is less than 0.02, indicating a relatively high content of 1,3-propanesulfonate lactone. This results in a thicker SEI film formed during the electrochemical device's formation process, hindering lithium-ion transport and thus causing poor rate performance. In Comparative Example 4, the y / z ratio is greater than 160, indicating a relatively high content of 1,3-propanesulfonate lactone. This leads to an unstable SEI film formed during the electrochemical device's formation process, resulting in a higher low-temperature thickness expansion rate and poor rate performance. Furthermore, Table 1 shows that regardless of whether the negative electrode active material is natural graphite, artificial graphite, hard carbon, soft carbon, or silicon-based material, by controlling the range of (x1-x2) / x1 and y (i.e., I...),... D / I GThe range of ), and the ratio range of the mass content z% and y of 3-propanesulfonate lactone, can both allow the electrochemical device to have good rate performance while also effectively suppressing the thickness expansion rate after multiple low-temperature cycles. In particular, as shown in Table 1, when at least one of the following conditions is met, the rate performance of the electrochemical device can be further improved and the thickness expansion rate after multiple low-temperature cycles is less obvious; especially when 1%≤(x1-x2) / x1≤15% or 0.01≤z≤3, the rate performance of the electrochemical device is improved more significantly and the thickness expansion rate after multiple low-temperature cycles can be further suppressed.

[0106] Examples 2-1 to 2-5

[0107] Except for adjusting the average volumetric particle size Dv50 according to Table 2, the rest is the same as in Examples 1-5.

[0108] Table 2

[0109] In Table 2, compared to Examples 2-4 to 2-5, Examples 1-5, and Examples 2-1 to 2-3, the Dv50 of the negative electrode active material is in the range of 5-15 μm. Therefore, the electrochemical device exhibits good rate performance while showing little thickness expansion after multiple low-temperature cycles. This indicates that when the average volumetric particle size DV50 of the negative electrode active material is between 5 μm and 15 μm, it avoids the decrease in diffusion rate caused by excessively large particles and reduces side reactions (such as excessive SEI film growth) caused by excessively small particles due to their large specific surface area. This is beneficial for further improving the rate performance of the electrochemical device and reducing the thickness expansion after multiple low-temperature cycles.

[0110] Examples 3-1 to 3-11

[0111] Except for the preparation of the electrolyte as follows, the rest is the same as in Examples 1-5.

[0112] <Preparation of Electrolyte>

[0113] In an argon-atmospheric glove box with a water content of less than 10 ppm, the organic solvents ethylene carbonate, propylene carbonate, and DEC were mixed evenly to obtain a base solvent. The fully dried lithium salt LiPF6, 1,3-propanesulfonate lactone, and compound I were dissolved in the above base solvent and mixed evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass content of lithium salt LiPF6 was 12.5%, the mass content of 1,3-propanesulfonate lactone is shown in Table 3, the types and mass contents of compound I are shown in Table 3, the mass content of ethylene carbonate was 20%, the mass content of propylene carbonate was 5%, and the balance was DEC.

[0114] Table 3

[0115] In Table 3, in the electrochemical devices of Examples 3-1 to 3-11, the electrolyte contained 0.001% to 1% of the compound of Formula I, and its thickness expansion rate could be further suppressed, while the rate performance remained relatively good. This indicates that 0.001% to 1% of the compound of Formula I can form a stable SEI film of suitable thickness at the electrode interface of the electrochemical device, which is beneficial for suppressing the thickness expansion rate after multiple cycles of the electrochemical device.

[0116] Examples 4-1 to 4-9

[0117] Except for the preparation of the electrolyte as follows, the rest is the same as in Examples 1-5.

[0118] <Preparation of Electrolyte>

[0119] In an argon-atmospheric glove box with a water content of less than 10 ppm, cyclic carbonates and DEC were mixed evenly to obtain a base solvent. Thoroughly dried lithium salt LiPF6 and 1,3-propanesulfonate lactone were dissolved in the base solvent and mixed evenly to obtain an electrolyte. Based on the mass of the electrolyte, the mass content of lithium salt LiPF6 was 12.5%, the mass content of 1,3-propanesulfonate lactone was 3%, the types and mass contents of cyclic carbonates are shown in Table 4, and the balance was DEC.

[0120] Table 4

[0121] In Table 4, since the mass content of cyclic carbonate in Examples 4-6 is less than 5%, the electrolyte has a relatively poor ability to dissolve lithium salts, and the rate performance of the electrochemical device is reduced compared to other examples.

[0122] Example 5-1

[0123] Except for forming multiple positive electrode tabs and multiple negative electrode tabs by die-cutting positive electrode current collectors and negative electrode current collectors during the battery manufacturing process, the rest is the same as in Examples 1-5.

[0124] Table 5

[0125] In Table 5, since the negative and positive electrode tabs in Examples 1-5 are single, their rate performance is relatively worse than that in Examples 5-1. This indicates that multiple tabs can provide more transport channels for ions and electrons, thereby improving the fast charging performance and rate performance of the electrochemical device.

[0126] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0127] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0128] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device, characterized in that, It includes an electrolyte, and a positive electrode, a separator, and a negative electrode stacked sequentially. The positive electrode includes a positive current collector, and at least one surface of the positive current collector is provided with a positive active material layer. The negative electrode includes a negative current collector, and at least one surface of the negative current collector is provided with a negative active material layer. The length of the negative active material layer is greater than the length of the positive active material layer. The longest length of the negative active material layer is x1, and the shortest length of the positive active material layer is x2, with 0.1% ≤ (x1-x2) / x1 ≤ 30%. The negative electrode active material layer includes a negative electrode active material, and the peak intensity of the D peak in the Raman spectrum of the negative electrode active material is I. D The peak strength of G is I G y = I D / I G , 0.2≤y≤0.8; The electrolyte includes 1,3-propanesulfonate lactone, wherein the mass content of 1,3-propanesulfonate lactone in the electrolyte is z%, and 0.02≤y / z≤160.

2. The electrochemical device according to claim 1, characterized in that, The electrochemical device satisfies at least one of the following conditions: (1) The negative electrode current collector is provided with negative electrode active material layers on both the upper and lower surfaces, and the two negative electrode active material layers have the same length; (2) The positive electrode current collector is provided with the positive electrode active material layer on both the upper and lower surfaces, and the two positive electrode active material layers have the same length.

3. The electrochemical device according to claim 1, characterized in that, The electrochemical device satisfies at least one of the following conditions: (1)1%≤(x1-x2) / x1≤20%; (2)0.2≤y≤0.6； (3)0.005≤z≤10； (4) 0.067≤y / z≤60.

4. The electrochemical device according to claim 1, characterized in that, The electrochemical device satisfies at least one of the following conditions: (1)1%≤(x1-x2) / x1≤15%; (2)0.01≤z≤3。 5. The electrochemical device according to any one of claims 1 to 4, characterized in that, The negative electrode sheet includes multiple negative electrode tabs, which are integrally formed with the negative electrode current collector; and / or The positive electrode sheet includes multiple positive electrode tabs, which are integrally formed with the positive current collector.

6. The electrochemical device according to any one of claims 1 to 4, characterized in that, The average volume particle size D of the negative electrode active material V 50 ranges from 5μm to 15μm.

7. The electrochemical device according to any one of claims 1 to 4, characterized in that, The electrolyte also includes a compound of formula I, the structural formula of which is shown in formula (I): Among them, R 21 R 22 R 23 and R 24 Each is independently selected from hydrogen atoms, halogen atoms, cyano groups, and substituted or unsubstituted C1 to C2 atoms. 10 Alkyl, substituted or unsubstituted C2 to C3 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne group, substituted or unsubstituted C1 to C2 10 The R group contains any one of the heteroatom-containing functional groups, and when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; 21 R 22 R 23 and R 24 A ring can be formed between any two groups in it; Based on the mass of the electrolyte, the mass content of the compound of formula I is from 0.001% to 1%.

8. The electrochemical device according to claim 7, characterized in that, The compound of Formula I includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilane) maleate, tetraallylsilane, pentamethylpentavinylcyclopentasiloxane, vinylmethylsilyl(diol) diacetate, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethylenedisiloxane, triacetoxyethylsilane, trivinylmethylsilane, triethylvinylsilane, triethylsilylacetylene, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, or vinyltriethoxysilane.

9. The electrochemical device according to any one of claims 1 to 4, characterized in that, The electrolyte also includes a cyclic carbonate compound, which includes at least one of ethylene carbonate and propylene carbonate, and the mass content of the cyclic carbonate compound is from 5% to 40% based on the mass of the electrolyte.

10. The electrochemical device according to any one of claims 1 to 4, characterized in that, The negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, or soft carbon.

11. The electrochemical device according to claim 1, characterized in that, The electrochemical device has a wound structure, which includes the positive electrode, the separator, and the negative electrode arranged in sequence and wound together.

12. An electronic device comprising the electrochemical device according to any one of claims 1 to 11.

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