Electrochemical device and electronic apparatus

Abstract

The invention provides an electrochemical device and electronic equipment, the electrochemical device comprises a positive electrode plate, a negative electrode plate and an electrolyte, the negative electrode plate comprises a negative electrode current collector and a first film layer arranged on at least one surface of the negative electrode current collector, the first film layer comprises a negative electrode active material, a second film layer is arranged on one side, far away from the negative electrode current collector, of the first film layer, the second film layer comprises an organic sulfonate compound and a binder, and the mass ratio of the organic sulfonate compound to the binder is 0.001-100. The electrochemical device has good cycle performance and storage performance.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and specifically relates to an electrochemical device and an electronic device. Background Art

[0002] With the continuous development of electrochemical devices, higher requirements are put forward for their performance. Since side reactions easily occur between the electrolyte and the negative electrode in the electrochemical device, the cycle performance of the electrochemical device will deteriorate. Therefore, it is necessary to improve the cycle performance of the electrochemical device. Summary of the Invention

[0003] The present application provides an electrochemical device and an electronic device, and the electrochemical device has good cycle performance and storage performance.

[0004] In a first aspect, the present application provides an electrochemical device, including a positive electrode sheet, a negative electrode sheet and an electrolyte. The negative electrode sheet includes a negative electrode current collector and a first film layer provided on at least one surface of the negative electrode current collector. The first film layer includes a negative electrode active material. A second film layer is provided on a side of the first film layer away from the negative electrode current collector. The second film layer includes an organic sulfonate compound and a binder, wherein the mass ratio of the organic sulfonate compound to the binder is from 0.001 to 100.

[0005] According to the present application, the negative electrode sheet of the electrochemical device is provided with a first film layer and a second film layer, wherein the second film layer is provided on the side away from the negative electrode current collector, that is, the first film layer is provided between the negative electrode current collector and the second film layer. The second film layer includes an organic sulfonate compound. By controlling the mass ratio of the organic sulfonate compound to the binder in the second film layer within the above range, the second film layer can enable active ions (such as lithium ions) to be quickly desolvated, reduce the co-insertion of the solvent in the electrolyte into the negative electrode active material in the first film layer, thereby reducing the damage to the structure of the negative electrode active material, reducing the side reaction between the negative electrode active material and the solvent, and effectively improving the cycle performance and storage performance of the electrochemical device.

[0006] In some embodiments, based on the total mass of the first film layer and the second film layer, the mass percentage content of the organic sulfonate compound is x%, and 0.01 ≤ x ≤ 5. Based on the above embodiments, under this condition, the organic sulfonate compound in the second film layer can more effectively reduce the influence of solvent co-insertion on the negative electrode active material, and further improve the cycle performance and storage performance of the electrochemical device.

[0007] In some embodiments, the intensity of the D peak in the Raman spectrum of the negative electrode active material is I D , the intensity of the G peak is I G , y = I D / I G ; the average volume particle size D of the negative electrode active material V50 is d μm; x, y, and d satisfy: 0.0017 ≤ x / (d + y) ≤ 0.33. Based on the above embodiments, y can represent the degree of defect of the negative electrode active material. When x, y, and d satisfy the above relationship, the cycle performance and storage performance of the chemical device can be further improved.

[0008] In some embodiments, the electrochemical device satisfies at least one of the following conditions: (1) the mass ratio of the organic sulfonate compound to the binder is from 0.01 to 20; (2) 0.1 ≤ x ≤ 2; (3) 0.2 ≤ y ≤ 0.8; preferably 0.2 ≤ y ≤ 0.6; (4) 5 ≤ d ≤ 16; preferably 8 ≤ d ≤ 14; (5) 0.0058 ≤ x / (d + y) ≤ 0.14. In the above embodiments, by further controlling the mass ratio of the organic sulfonate compound to the binder in the first film layer, the mass percentage content x% of the organic sulfonate compound, and the average volume particle size D of the negative electrode active material V 50 d μm and y satisfying the above conditions can further improve the cycle performance and storage performance of the electrochemical device.

[0009] In some embodiments, the positive electrode plate includes a positive electrode active material layer; the outer periphery of the first film layer includes an extending area that does not overlap with the positive electrode active material layer, and the ratio of the area of the extending area to the area of the first film layer is from 1% to 30%.

[0010] In the above embodiments, the outer periphery of the first film layer includes an extending area that does not overlap with the positive electrode active material layer, and controlling the area of the extending area within the above range can reduce the precipitation of active ions at the edge of the negative electrode plate during charging and improve the safety of the electrochemical device; in addition, since there is no reaction of deintercalating and intercalating active ions in the extending area during the formation process, it is not easy to form a stable SEI film, and the electrolyte is likely to react with the negative electrode active material in the extending area, deteriorating the cycle performance of the electrochemical device; while in the present application, the second film layer can act as a protective layer to reduce the side reaction between the extending area and the electrolyte. Therefore, in the above embodiments, the safety of the electrochemical device can be improved without deteriorating the cycle performance of the electrochemical device.

[0011] In some embodiments, the organic sulfonate compound includes a compound of formula (I),

[0012]

[0013] wherein, R 11 is selected from substituted or unsubstituted C1 to C 10 alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 alkynyl, substituted or unsubstituted C1 to C6 chain heteroalkyl, halogen atom, amino group or The number of heteroatoms in the chain heteroalkyl group is from 1 to 5, and the heteroatoms in the chain heteroalkyl group are selected from O, N, P or S; the R 12 is selected from a substituted or unsubstituted C1 to C 10 alkylene group, a substituted or unsubstituted C2 to C 10 alkenylene group, a substituted or unsubstituted C1 to C6 chain heteroalkylene group, the number of heteroatoms in the chain heteroalkylene group is from 1 to 5, and the heteroatoms in the chain heteroalkylene group are selected from O or S; when substituted, the substituent is selected from a halogen atom, a C2 to C5 cycloalkyl group or a C6 to C 12 aryl group; X 11 and X 12 are each independently selected from Li, K or Na. Based on the above embodiments, by using the organic sulfonate compound having the above structure, the cycle performance and storage performance of the electrochemical device can be further improved.

[0014] In some embodiments, the compound of formula (I) includes at least one of the following compounds:

[0015]

[0016] By using the above types of organic sulfonate compounds, the cycle performance and storage performance of the electrochemical device can be further improved.

[0017] In some embodiments, the electrolyte includes a compound of formula (Ⅱ):

[0018]

[0019] wherein, R 21 , R 22 , R 23 and R 24 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 alkyl group, a substituted or unsubstituted C2 to C 10 alkenyl group, a substituted or unsubstituted C2 to C 10 alkynyl group, any one of a substituted or unsubstituted C1 to C 10 heteroatom-containing functional group, when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 , R 22 , R 23 and R 24A ring can be formed between any two of the groups; based on the mass of the electrolyte, the mass percentage of the compound of formula (II) is 0.01% to 1%. Based on the above embodiments, adding the compound of formula (II) in the above content to the electrolyte can cooperate with the organic sulfonate compound in the second film layer to reduce the side reaction between the electrolyte and the negative electrode active material, and further improve the cycle performance and storage performance of the electrochemical device.

[0020] In some embodiments, the compound of formula (II) includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilyl) maleate, tetraallylsilane, pentamethylpentavinyldisiloxane, vinylmethylsilyl (diol) diacetate, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethenyldisiloxane, triacetoxyethylsilane, trivinylmethylsilane, triethylvinylsilane, triethylsilylacetylene, tetravinylsilane, tetramethyltetravinylcyclotetrasiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane or vinyltriethoxysilane. By using the compound of formula (II) of the above type, the cycle performance and storage performance of the electrochemical device can be further improved.

[0021] In some embodiments, the electrolyte includes a compound of formula (III),

[0022]

[0023] wherein, R1 and R3 are each independently selected from C1-C4 alkyl groups, and R2 is selected from C1-C4 alkylene groups;

[0024] Based on the mass of the electrolyte, the mass percentage of the compound of formula (III) is 0.001% to 5%. Based on the above embodiments, adding the compound of formula (III) in the above content to the electrolyte can cooperate with the organic sulfonate compound in the second film layer to reduce the side reaction between the electrolyte and the negative electrode active material, and further improve the cycle performance and storage performance of the electrochemical device.

[0025] In some embodiments, the electrochemical device satisfies at least one of the following characteristics:

[0026] (1) The binder includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium hydroxymethyl cellulose, polyvinyl alcohol, sodium alginate, sodium polyacrylate, lithium polyacrylate, styrene-butadiene rubber; (2) The negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon or soft carbon. Based on the above embodiments, by using the binder and / or negative electrode active material of the above type, the electrochemical device has better cycle performance and storage performance.

[0027] In a second aspect, the present application provides an electronic device, including the electrochemical device according to any one of the embodiments of the first aspect.

[0028] According to the present application, the electronic device includes the electrochemical device of the first aspect, and thus has the corresponding beneficial effects of the first aspect. Detailed implementation manners

[0029] In the description of this specification, the embodiments or implementation manners are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments.

[0030] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0031] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0032] In this specification, "alkyl" refers to a straight-chain or branched-chain saturated hydrocarbon group. "Alkenyl" refers to a straight-chain or branched-chain alkyl group containing one or more carbon-carbon double bonds. "Alkynyl" refers to a straight-chain or branched-chain alkyl group containing one or more carbon-carbon triple bonds. "Heteroalkyl chain" refers to a straight-chain or branched-chain saturated hydrocarbon group containing a heteroatom. "Aryl" refers to an aromatic monocyclic hydrocarbon ring system or polycyclic system, in which two or more aromatic hydrocarbon rings are fused (i.e., contain shared bonds) together or at least one aromatic monocyclic hydrocarbon ring is fused with one or more cycloalkyl and / or heterocycloalkyl rings. "Sub-" refers to a group that can form covalent bonds with two other moieties.

[0033] In this specification, the substituents of the compounds are disclosed in groups or ranges. It is explicitly contemplated that such a description includes every individual sub-combination of the members of these groups and ranges. For example, it is explicitly contemplated that the term "alkyl of C1 to C6" discloses C1, C2, C3, C4, C5, C6, C1 to C6, C1 to C5, C1 to C4, C1 to C3, C1 to C2, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C6, C3 to C5, C3 to C4, C4 to C6, C4 to C5, and C5 to C6 alkyl individually.

[0034] Electrochemical device

[0035] In a first aspect, the present application provides an electrochemical device, comprising a positive electrode plate, a negative electrode plate, and an electrolyte. The negative electrode plate includes a negative current collector and a first film layer provided on at least one surface of the negative current collector. The first film layer includes a negative active material. A second film layer is provided on a side of the first film layer away from the negative current collector. The second film layer includes an organic sulfonate compound and a binder. Among them, the mass ratio of the organic sulfonate compound to the binder is from 0.001 to 100.

[0036] According to the present application, the negative electrode plate of the electrochemical device is provided with a first film layer and a second film layer, wherein the second film layer is provided on the side away from the negative current collector, that is, the first film layer is provided between the negative current collector and the second film layer. The second film layer includes an organic sulfonate compound. By controlling the mass ratio of the organic sulfonate compound to the binder in the second film layer within the above range, the second film layer can reduce the co-insertion of the solvent in the electrolyte into the negative active material of the first film layer through rapid desolvation, thereby reducing the damage to the structure of the negative active material and reducing the side reaction between the negative active material and the solvent, and can effectively improve the cycle performance and storage performance of the electrochemical device.

[0037] Specifically, the inventors found that the sulfonate group in the organic sulfonate compound has good desolvation effect, so that the co-insertion of the solvent into the negative electrode active material can be reduced, protecting the negative electrode active material and reducing the side reaction between the negative electrode sheet and the electrolyte at the same time. Meanwhile, the negative electrode sheet includes a first film layer and a second film layer, wherein the first film layer includes the negative electrode active material, and the second film layer includes the organic sulfonate compound and the binder. The second film layer is located on the side away from the negative electrode current collector, and the penetration direction of the electrolyte is from the second film layer to the first film layer. At this time, the second film layer can serve as a protective layer for the first film layer. During the charging process, when the solvated active ions pass through the second film layer, under the action of the organic sulfonate compound, they can be quickly desolvated and enter the first film layer, thereby effectively reducing the influence of solvation co-insertion on the negative electrode active material in the first film layer and improving the cycle performance of the electrochemical device. It can be understood that compared with the single-layer blending of the negative electrode active material and the organic sulfonate compound, by setting the layered structure, the influence of the organic sulfonate compound on the conductive path of the first film layer can be effectively reduced, and the active ions passing through the second film layer can be fully desolvated, playing a good protective effect on the negative electrode active material at different positions in the first film layer, so that the electrochemical device has good cycle performance and storage performance.

[0038] In addition, it is necessary to control the mass ratio of the organic sulfonate compound to the binder in the second film layer to be 0.001 to 100. If the content of the organic sulfonate compound is too low, it may be difficult to fully desolvate the active ions passing through the second film layer, and the protective effect on the negative electrode active material in the first film layer is poor. Or a thicker second film layer is required to desolvate the active ions, which will affect the energy density of the electrochemical device. If the content of the binder is too low, the structure of the second film layer may be unstable, especially in the electrolyte, the organic sulfonate compound in the second film layer falls off, resulting in the destruction of the structure of the second film layer, and it is difficult to protect the negative electrode active material in the first film layer. Therefore, it is necessary to control the mass ratio of the organic sulfonate compound to the binder in the second film layer within the above range. For example, the mass ratio of the organic sulfonate compound to the binder in the second film layer can be 0.001, 0.01, 0.15, 1.2, 2.0, 9.5, 18.3, 29.3, 37.3, 42.7, 53.3, 60.2, 61.9, 71.5, 78.1, 92.1, 97.6, 100, or within the range composed of any of the above values. Further, the mass ratio of the organic sulfonate compound to the binder can be 0.01 to 20, and at this time, the cycle performance and storage performance of the electrochemical device are better.

[0039] In some embodiments, based on the total mass of the first film layer and the second film layer, the mass percentage content of the organic sulfonate compound is x%, and 0.01 ≤ x ≤ 5.

[0040] In some of the above embodiments, x% can be adjusted by adjusting the mass ratio of the organic sulfonate and the binder in the second film layer, and by adjusting the masses of the first film layer and the second film layer. When x meets the above conditions, the organic sulfonate compound in the second film layer can more effectively reduce the influence of co-insertion of the solvent on the anode active material, further improving the cycle performance and storage performance of the electrochemical device, while reducing the influence of the second film layer on the energy density of the electrochemical device. For example, x can be 0.01, 0.1, 0.7, 0.9, 1.3, 1.8, 2.2, 2.5, 2.8, 3.5, 3.6, 3.9, 4.4, 4.8, 5, or within the range composed of any of the above values. Preferably, 0.01 ≤ x ≤ 2.

[0041] In some embodiments, the intensity of the D peak in the Raman spectrum of the anode active material is I D and the intensity of the G peak is I G , and y = I D / I G ; the average volume particle size D V 50 of the anode active material is d μm; x, y, and d satisfy: 0.0017 ≤ x / (d + y) ≤ 0.33.

[0042] In some of the above embodiments, the intensity I D of the D peak and the intensity I G of the G peak in the Raman spectrum of the anode active material have the meanings well-known in the art, where I D represents the intensity of the peak at 1360 ± 5 cm -1 in the Raman spectrum of the anode active material; I G represents the intensity of the peak at 1580 ± 5 cm -1 in the Raman spectrum of the anode active material. The ratio of the two can represent the degree of defect of the anode active material. Generally speaking, I D / I GThe larger it is, the higher its degree of defect, which is more conducive to the insertion and extraction of active ions and improves the fast charging performance. However, it will also exacerbate the side reaction between it and the electrolyte, deteriorating the cycling performance. Therefore, when the degree of defect of the negative electrode active material is small, only a small amount of organic sulfonate compound needs to be added to enable the electrochemical device to have good cycling performance and storage performance. At the same time, the larger the particle size of the negative electrode active material, the better its cycling stability. In addition, under the condition of the same mass of the negative electrode active material, the larger the particle size, the smaller the specific surface area. Therefore, when the particle size of the negative electrode active material is large, only a small amount of organic sulfonate compound needs to be added to enable the electrochemical device to have good cycling performance and storage performance. Therefore, the above three conditions will jointly affect the performance of the electrochemical device. The inventors found that when x, y, and d meet the above conditions, the electrochemical device still has better cycling performance and storage performance under high-rate charge and discharge. For example, the value of x / (d + y) can be 0.0017, 0.018, 0.040, 0.064, 0.093, 0.108, 0.136, 0.155, 0.198, 0.219, 0.240, 0.272, 0.304, 0.317, 0.33, or within the range composed of any of the above values. Preferably, it can satisfy: 0.0058 ≤ x / (d + y) ≤ 0.14.

[0043] The intensity I of the D peak in the Raman spectrum of the negative electrode active material D and the intensity I of the G peak G can be detected according to the methods and instruments known in the art. As an example, a laser confocal Raman spectrometer (Raman, HREvolution, HORIBA Scientific Instruments Division) is used to scan the sample particles to obtain the D peak and G peak of all particles within this area range. The LabSpec software is used to process the data to obtain the peak intensities of the D peak and G peak of each particle, which are I D and I G , I D / I G Taking 0.02 as the step size, the frequency of I D / I G is statistically analyzed to obtain a normal distribution graph, and the average value of I D / I G is calculated, which is the intensity ratio I D / I G of the D peak to the G peak of the active material. The laser wavelength of the Raman spectrometer can be in the range of 532 nm to 785 nm. Among them, for the D peak: the peak intensity at 1360 cm -1 is taken; for the G peak: the peak intensity at 1580 cm -1 is taken.

[0044] In some embodiments, 0.2 ≤ y ≤ 0.8. Based on the above embodiments, when the defect degree y of the negative electrode active material is within the above range, the cycle stability and fast charging performance can be better balanced, and the electrochemical device can better balance the cycle performance and fast charging performance. For example, y can be 0.2, 0.21, 0.26, 0.30, 0.38, 0.41, 0.47, 0.52, 0.55, 0.59, 0.60, 0.67, 0.75, 0.80, or within the range composed of any of the above values. Preferably, 0.2 ≤ y ≤ 0.6.

[0045] In some embodiments, 5 ≤ d ≤ 16. When the average volume particle size D V 50 dμm of the negative electrode active material satisfies the above conditions, the cycle performance and storage performance of the electrochemical device are better. For example, d can be 5, 5.3, 5.8, 6, 6.8, 7.2, 7.6, 8, 8.2, 8.9, 8.9, 9.4, 10.1, 10.7, 11.0, 11.6, 12.1, 12.4, 12.9, 13.2, 13.6, 14, 14.6, 14.8, 15.3, 15.6, 16, or within the range composed of any of the above values. Preferably, 8 ≤ d ≤ 14.

[0046] The average volume particle size D V 50 has the meaning well-known in the art and can be detected according to the methods and instruments known in the art. As an example, it can be detected with reference to GB / T 19077-2016. Specifically: Weigh 1 g of the sample, mix it evenly with 20 mL of deionized water and a small amount of dispersant, place it in an ultrasonic device and ultrasonicate for 5 min, then pour the solution into the injection system Hydro 2000SM for testing. The testing equipment used is Mastersizer3000 produced by Malvern. During the testing process, when the laser beam passes through the dispersed particle sample, the particle size measurement is completed by measuring the intensity of the scattered light. Then the data is used for analysis and calculation to form the particle size distribution of the scattered spectrogram. The refractive index of the particles used in the test is 1.8. One sample is tested three times, and the final particle size is the average of the three tests to obtain Dv50.

[0047] In some embodiments, the positive electrode plate includes a positive electrode active material layer; the outer periphery of the first film layer includes an extended area that does not overlap with the positive electrode active material layer, and the ratio of the area of the extended area to the area of the first film layer is 1% to 30%.

[0048] In the above-described embodiments, the first film layer includes protruding regions on both sides in the length direction of the negative electrode sheet that do not overlap with the positive electrode active material layer, and the area of the protruding regions is controlled within the above range, which can reduce the precipitation of active ions at the edges of the negative electrode sheet during charging and improve the safety of the electrochemical device; in addition, since there is no reaction of deintercalating and intercalating active ions in the protruding regions during the formation process, it is not easy to form a stable SEI film in the protruding regions, and the electrolyte is likely to have a side reaction with the negative electrode active material in the protruding regions, deteriorating the cycling performance of the electrochemical device; while in the present application, the second film layer can act as a protective layer to reduce the side reaction between the protruding regions and the electrolyte. Thus, in the above-described embodiments, the safety of the electrochemical device can be improved without deteriorating the cycling performance of the electrochemical device. For example, the ratio of the area of the protruding regions to the area of the first film layer can be 1%, 4%, 7%, 11%, 14%, 19%, 22%, 24%, 29%, 30%, or within the range composed of any of the above values. Preferably, the ratio of the area of the protruding regions to the area of the first film layer is 2% to 20%.

[0049] In some embodiments, the organic sulfonate compound includes the compound of formula (I),

[0050]

[0051] wherein, R 11 is selected from substituted or unsubstituted C1 to C 10 alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 alkynyl, substituted or unsubstituted C1 to C6 chain heteroalkyl, halogen atom, amino group or the number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P or S; R 12 is selected from substituted or unsubstituted C1 to C 10 alkylene, substituted or unsubstituted C2 to C 10 alkenylene, substituted or unsubstituted C1 to C6 chain heteroalkylene, the number of heteroatoms in the chain heteroalkylene is 1 to 5, and the heteroatoms in the chain heteroalkylene are selected from O or S; when substituted, the substituents are selected from halogen atoms, C2 to C5 cycloalkyl or C6 to C 12 aryl; X 11 and X 12 each independently is selected from Li, K or Na. Based on the above embodiments, by using the organic sulfonate compound having the above structure, the cycling performance and storage performance of the electrochemical device can be further improved.

[0052] It can be further understood that in the compound shown in formula (I), the sulfonate group mainly plays the above-mentioned role in the second film layer, and R therein 11 When it is the above-mentioned type of group, it will not deteriorate the performance of the electrochemical device, X 11 and X 12 can be selected according to the specific type of the electrochemical device. The following lists some compounds shown in formula (I) as examples.

[0053] In some embodiments, the compound of formula (I) includes at least one of the following compounds:

[0054]

[0055]

[0056] By using the above-mentioned type of organic sulfonate compound, the cycle performance and storage performance of the electrochemical device can be further improved.

[0057] In some embodiments, the electrolyte includes a compound of formula (II):

[0058]

[0059] wherein, R 21 、R 22 、R 23 and R 24 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 alkyl group, a substituted or unsubstituted C2 to C 10 alkenyl group, a substituted or unsubstituted C2 to C 10 alkynyl group, a substituted or unsubstituted C1 to C 10 heteroatom-containing functional group, and when substituted, the substituent is a halogen atom; the heteroatom is selected from Si or O; R 21 、R 22 、R 23 and R 24A ring can be formed between any two of the groups; based on the mass of the electrolyte, the mass percentage of the compound of formula (II) is 0.01% to 1%. Based on the above embodiments, adding the compound of formula (II) in the above content to the electrolyte can cooperate with the organic sulfonate compound in the second film layer to reduce the side reaction between the electrolyte and the negative electrode active material, and further improve the cycle performance and storage performance of the electrochemical device. For example, based on the mass of the electrolyte, the mass percentage of the compound of formula (II) can be 0.01%, 0.03%, 0.15%, 0.17%, 0.30%, 0.35%, 0.42%, 0.54%, 0.56%, 0.68%, 0.75%, 0.79%, 0.90%, 0.96%, 1%, or within the range composed of any of the above values.

[0060] It can be further understood that among the compounds represented by formula (II), the main component that plays the above role in the electrolyte is the silyl group, where R 21 , R 22 , R 23 , R 24 When being the above types of groups, it will not deteriorate the performance of the electrochemical device. The following lists some compounds represented by formula (II) as examples.

[0061] In some embodiments, the compound of formula (II) includes at least one of tetramethyldivinyldisiloxane, bis(trimethylsilyl) maleate, tetraallylsilane, pentamethylpentavinyldisiloxane, vinylmethylsilanediol diacetate, vinyltrimethylsilane, divinyldimethylsilane, 1,3-dimethyl-1,1,3,3-tetraethenyldisiloxane, triacetoxyethylsilane, trivinylmethylsilane, triethylvinylsilane, triethylsilylacetylene, tetravinylsilane, tetramethyltetravinyldisiloxane, diphenyldifluorosilane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane or vinyltriethoxysilane. By using the above types of compounds of formula (II), the cycle performance and storage performance of the electrochemical device can be further improved.

[0062] In some embodiments, the electrolyte includes a compound of formula (III),

[0063]

[0064] wherein, R1 and R3 are each independently selected from C1 to C4 alkyl groups, and R2 is selected from C1 to C4 alkylene groups;

[0065] Based on the mass of the electrolyte, the mass percentage of the compound of formula (III) is 0.001% to 5%. Based on the above embodiments, adding the compound of formula (III) in the above content in the electrolyte can cooperate with the organic sulfonate compound in the second film layer to reduce the side reaction between the electrolyte and the negative electrode active material, and further improve the cycle performance and storage performance of the electrochemical device. For example, based on the mass of the electrolyte, the mass percentage of the compound of formula (III) can be 0.001%, 0.01%, 0.06%, 0.48%, 0.84%, 1.48%, 1.61%, 2.00%, 2.58%, 2.95%, 3.40%, 3.53%, 4.04%, 4.52%, 4.89%, 5%, or within the range composed of any of the above values.

[0066] It can be further understood that regarding the compound shown in formula (III), the main part that plays the above role in the electrolyte is the carbonate dimer structure. When R1, R2, and R3 are the above types of groups, the performance of the electrochemical device will not deteriorate. The following lists some compounds shown in formula (III) as examples.

[0067] In some embodiments, the compound shown in formula (III) includes at least one of the following compounds:

[0068]

[0069]

[0070] In some embodiments, as an example, the electrolyte further includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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).

[0071] In some embodiments, the electrolyte includes an electrolyte salt, and the electrolyte salt may include a lithium salt. As an example, the lithium salt includes, but is not limited to, at least one of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoro(oxalato)borate), LiBOB (lithium bis(oxalato)borate), LiPO2F2 (lithium difluorophosphate), LiDODFP (lithium difluoro(dioxalato)phosphate), and LiOTFP (lithium tetrafluoro(oxalato)phosphate).

[0072] In some embodiments, the electrochemical device satisfies at least one of the following characteristics: (1) the binder includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium hydroxymethyl cellulose, polyvinyl alcohol, sodium alginate, sodium polyacrylate, lithium polyacrylate, and styrene-butadiene rubber; (2) the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, or soft carbon. Based on the above embodiments, by using the above types of binders and / or negative electrode active materials, the electrochemical device has better cycle performance and storage performance.

[0073] In some embodiments, the first film layer further includes a negative electrode binder. The negative electrode binder may be selected from one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium hydroxymethyl cellulose, polyvinyl alcohol, sodium alginate, sodium polyacrylate, lithium polyacrylate, and styrene-butadiene rubber.

[0074] The first film layer and / or the second film layer of the present application further includes a conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent, as long as the object of the present application can be achieved. For example, the negative electrode conductive agent may be at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots, or graphene, and the above carbon nanotubes may include, but are not limited to, at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0075] The present application has no particular limitation on the negative electrode current collector, as long as the object of the present application can be achieved. For example, the negative electrode current collector may include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal, etc. Among them, the conductive metal includes but is not limited to copper, nickel, or titanium, and the materials of the polymer substrate include but are not limited to at least one of polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene terephthalate, poly(ethylene naphthalate), or poly(p-phenylene terephthalamide). In the present application, there is no particular limitation on the thicknesses of the negative electrode current collector and the negative electrode active layer, as long as the object of the present 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 layer is 30 μm to 160 μm. In the present application, the first film layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on both surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here may be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector, and the present application has no particular limitation, as long as the object of the present application can be achieved.

[0076] Optionally, the negative electrode sheet may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the first film layer. The present application has no particular limitation on the composition of the conductive layer, and it may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular limitation on the conductive agent and the binder in the conductive layer, and they may be at least one of the above-mentioned conductive agents and the above-mentioned binders. The present application has no particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs, as long as the object of the present application can be achieved. The present application has no particular limitation on the thickness of the conductive layer, as long as the object of the present application can be achieved. For example, the thickness of the conductive layer is 1 μm to 10 μm.

[0077] [[Positive Electrode Sheet]]

[0078] The positive electrode sheet further includes a positive electrode current collector, and the positive electrode active material layer is provided on at least one surface of the positive electrode current collector.

[0079] The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material layer may be one layer or multiple layers. Each layer in the multiple positive electrode active material layers may contain the same or different positive electrode active materials. The positive electrode active material is any substance that can reversibly intercalate and deintercalate alkali metal ions.

[0080] The positive electrode active material includes lithium transition metal oxides containing nickel and other transition metals. In the lithium transition metal oxides containing nickel and other transition metals, the amount of nickel may be 60 mol% or more, for example, 75 mol% or more, for example, 80 mol% or more, for example, 85 mol% or more, or for example, 90 mol% or more, relative to the total molar amount of the transition metals.

[0081] In some embodiments, the positive electrode active material includes at least one active material selected from the group consisting of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, or lithium manganese iron phosphate.

[0082] In some embodiments, the positive electrode active material layer includes a positive electrode conductive agent; the type of the positive electrode conductive agent is not limited, and any known conductive material can be used. Examples of the positive electrode conductive agent may include, but are not limited to, carbon blacks such as acetylene black and Super-P; amorphous carbon materials such as needle coke; carbon nanotubes; graphene, etc. The above positive electrode conductive agents can be used alone or in any combination.

[0083] In some embodiments, the positive electrode active material layer includes a positive electrode binder. The type of the positive electrode binder is not particularly limited, and in the case of the coating method, it is sufficient that it is a binder material that can be dissolved or dispersed in the liquid medium used during electrode manufacturing. Examples of the positive electrode binder may include, but are not limited to, one or more of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, or nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutene rubber, or ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymer or its hydride, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or its hydride; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, or propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, or polytetrafluoroethylene-ethylene copolymer; polymer compositions having ionic conductivity of alkali metal ions, etc. The above positive electrode binders can be used alone or in any combination.

[0084] There is no limitation on the type of solvent used to form the positive electrode paste, as long as it can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener (used as needed). Examples of solvents for forming the positive electrode paste may include any one of aqueous solvents and organic solvents. Examples of aqueous media may include, but are not limited to, a mixed medium of alcohol and water, water, etc. Examples of organic media may 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; amides such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide or dimethyl sulfoxide, etc.

[0085] The thickener is usually used to adjust the viscosity of the paste. In the case of using an aqueous medium, a thickener and styrene-butadiene rubber latex can be used for pasting. There is no particular limitation on the type of thickener, and its examples may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, or casein and their salts, etc. The above thickeners can be used alone or in any combination.

[0086] There is no particular limitation on the type of positive electrode current collector, and it can be any material known to be suitable for use as a positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, or tantalum; materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0087] In order to reduce the electron contact resistance between the positive electrode current collector and the positive electrode active layer, the surface of the positive electrode current collector may include a conductive aid or a conductive coating. Examples of conductive aids may include, but are not limited to, precious metals such as carbon, gold, platinum, or silver. Examples of conductive coatings may include a mixture layer containing inorganic oxides, conductive agents, and binders.

[0088]

Separator

[0089] In this application, a separator is usually provided between the positive electrode plate and the negative electrode plate. The separator is used to separate the positive electrode plate and the negative electrode plate, prevent internal short circuit of the electrochemical device, allow electrolyte ions to pass freely, and does not affect the progress of the electrochemical charge and discharge process.

[0090] The present application has no particular limitation on the separator, as long as it can achieve the purpose of the present application. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of the separator may include at least one of woven film, non-woven film, microporous film, composite film, rolled film or spun film.

[0091] In the present application, the separator may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having 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 film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder. The present application has no particular limitation on the above-mentioned inorganic particles, and for example, it may include at least one of alumina, silica, magnesia, 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. The present application has no particular limitation on the above-mentioned binder, and for example, it may be at least one of the foregoing binders. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0092] The pore size of the separator in the present application is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In some embodiments, the thickness of the separator is 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 range, the insulation and mechanical strength can be ensured, and the rate performance and energy density of the secondary battery can be ensured.

[0093] The electrochemical device of the present application further includes a packaging bag for accommodating the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, as well as other components known in the art in the electrochemical device. The present application does not limit the above-mentioned other components. The present application has no particular limitation on the packaging bag, and it may be a packaging bag well known in the art, as long as it can achieve the purpose of the present application.

[0094] Electronic device

[0095] In a second aspect, the present application provides an electronic device including the electrochemical device according to any one of the embodiments of the first aspect.

[0096] According to the present application, the electronic device includes the electrochemical device of the first aspect, and thus has the corresponding beneficial effects of the first aspect.

[0097] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable CD player, a minidisc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0098] Embodiment

[0099] Hereinafter, taking a lithium-ion battery as an example, embodiments and comparative examples are given to more specifically illustrate the embodiments of the electrochemical device of the present application. Those skilled in the art will understand that the preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0100] <Test Method>

[0101] (1) Cycle performance test:

[0102] Place the lithium-ion battery in a constant-temperature test chamber at 45 °C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Charge the lithium-ion battery at a constant current of 1C until the voltage reaches 4.3V, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.05C, and then discharge it at a constant current of 1C until the voltage reaches 2.5V. This is one charge-discharge cycle, and the discharge capacity measured at this time is recorded as the initial discharge capacity C0. Taking the capacity of the first discharge as 100%, repeat the charge-discharge cycle. When the cycle reaches 800 times, stop the test and record the discharge capacity of the lithium-ion battery at this time, which is recorded as the discharge capacity C1 after 800 cycles, and calculate the cycle capacity retention rate of the lithium-ion battery.

[0103] Cycle capacity retention rate = C1 / C0 × 100%.

[0104] (2) High-temperature storage performance test:

[0105] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Charge it at a constant current of 1C until 4.3V, then charge it at a constant voltage until the current is less than or equal to 0.05C. After that, let it stand for 5 minutes, then discharge it at a constant current of 1C until 2.5V, and then charge it at a constant current of 1C until 4.3V, and then charge it at a constant voltage until the current is less than or equal to 0.05C. Record the thickness of the lithium-ion battery, which is denoted as the initial thickness. Transfer the lithium-ion battery to a constant temperature oven at 60°C and store it for 90 days. After 90 days of storage, take out the lithium-ion battery and observe and test its thickness, which is denoted as the thickness after high-temperature storage. Calculate the thickness expansion rate of the lithium-ion battery and use it as an index to evaluate the high-temperature storage performance of the lithium-ion battery.

[0106] High-temperature storage expansion rate = (storage thickness - initial thickness) / initial thickness × 100%.

[0107] (3) Fast charging performance test:

[0108] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature at a constant current of 3C until the voltage is 4.3V, then charge it at a constant current of 1C until 4.35V, and then charge it at a constant voltage until the current is less than or equal to 0.05C. Record the charging time T of this process.

[0109] Example 1-1

[0110] (1) Preparation of the negative electrode: Mix the organic sulfonate compound and the binder sodium alginate according to a mass ratio of 0.001:1, add deionized water and stir evenly to obtain a first slurry with a solid content of 75 wt%. Mix the negative electrode active material artificial graphite, the conductive agent Super P, and the negative electrode binder sodium carboxymethylcellulose according to a mass ratio of 95:2:3, add deionized water and stir evenly to obtain a second slurry with a solid content of 70 wt%; among them, the volume average particle size Dv50 of the artificial graphite is 10 μm, and the defect degree y is 0.5.

[0111] Coat the second slurry evenly on one surface of a negative electrode current collector copper foil with a thickness of 8 μm, then spray the first slurry on the surface of the first film layer with a spraying device to form a second film layer, and then dry it at 110°C. Repeat the above steps on the other surface of the negative electrode current collector. After cold pressing, a double-sided coated negative electrode sheet with a single-sided negative electrode material layer thickness of 150 μm is obtained. Then, cut the negative electrode sheet into negative electrode sheets with a specification of 77 mm × 875 mm, and weld the negative electrode tabs and set them aside. By controlling the coating amounts of the first film layer and the second film layer and controlling the total mass based on the first film layer and the second film layer, the mass percentage content of the organic sulfonate compound is 0.01%.

[0112] (2) Preparation of the positive electrode: Mix the positive electrode active material LiMn0.6 Fe 0.4 PO4, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) is added as a solvent. The system is stirred under the action of a vacuum mixer until it becomes a uniform positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on a positive electrode current collector aluminum foil with a thickness of 12μm, dried at 85℃, and the above steps are 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 100μm is obtained. The positive electrode sheet is cut into a specification of 74mm×866mm and welded to the pole ear for standby use.

[0113] The ratio of the area of ​​the extended region to the area of ​​the first film layer is (77×875-74×866) / (77×875)×100%=5%.

[0114] (3) Preparation of electrolyte: In an argon atmosphere glove box with a water content of <10 ppm, organic solvents ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) are mixed uniformly in a mass ratio of 1:1:3 to obtain a base solvent. Fully dried lithium salt LiPF6 and fluoroethylene carbonate (FEC), compound of formula (II), compound of formula (III), 1,3-propane sultone (PS), adiponitrile (ADN) and 1,3,6-hexanetrinitrile (HTCN) are dissolved in the above base solvent and mixed uniformly to obtain an electrolyte, wherein the mass percentage of lithium salt LiPF6 is 12.5%, the mass percentage of FEC is 5%, the mass percentage of PS is 2%, the mass percentage of AND is 1%, and the mass percentage of HTCN is 2%; the types and contents of the compound of formula (II) and the compound of formula (III) are shown in Table 1, and the balance is the base solvent.

[0115] (4) Preparation of isolation membrane: A polyethylene (PE) porous polymer film is used as the isolation membrane.

[0116] (5) Preparation of lithium-ion battery: The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, placed in a vacuum oven at 85°C to dry for 12 hours to remove moisture, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, shaping, capacity testing, secondary packaging and other processes, a lithium-ion battery is obtained.

[0117] The above lithium-ion batteries were tested for cycle performance and high temperature storage performance, and the results are shown in Table 1.

[0118] Example 1-1 to Example 1-37

[0119] Except for adjusting the parameters according to Table 1, the rest is the same as Example 1-1.

[0120] The ratio of the area of ​​the extended region to the area of ​​the first film layer is adjusted by adjusting the length and / or width of the negative electrode sheet.

[0121] The above lithium-ion batteries were tested for cycle performance and high temperature storage performance, and the results are shown in Table 1.

[0122] Comparative Example 1-1

[0123] It is substantially the same as Example 1-5, except that the preparation of the negative electrode is different, specifically:

[0124] Preparation of the negative electrode: The negative electrode active material artificial graphite, the conductive agent Super P, and the negative electrode binder sodium carboxymethyl cellulose are mixed in a mass ratio of 95:2:3, deionized water is added and stirred evenly to obtain a slurry with a solid content of 70wt%; wherein the volume average particle size Dv50 of the artificial graphite is 10μm, and the defect degree y is 0.5.

[0125] The slurry was evenly coated on one surface of a negative electrode collector copper foil with a thickness of 8 μm, and then dried at 110°C. The above steps were repeated on the other surface of the negative electrode 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. The negative electrode sheet was then cut into negative electrode sheets with a specification of 78 mm × 875 mm, and the negative electrode ears were welded for standby use.

[0126] The above lithium-ion batteries were tested for cycle performance and high temperature storage performance, and the results are shown in Table 1.

[0127]

[0128]

[0129]

[0130]

[0131] As can be seen from Table 1, the cycle capacity retention rate of the lithium-ion battery obtained in each embodiment is higher than that of the comparative example and the storage expansion rate is lower than that of the comparative example, indicating that by using a certain mass ratio of an organic sulfonate compound and a binder as the second film layer disposed on the surface of the negative electrode plate, the positive electrode active material in the first film layer can be effectively protected, and its side reaction with the electrolyte can be reduced, thereby improving the cycle performance and storage performance of the electrochemical device.

[0132] As can be seen from Examples 1-1 to 1-8, when the mass ratio of the organic sulfonate compound to the binder in the second film layer is from 0.01 to 20, the cycling performance and storage performance of the electrochemical device are better.

[0133] As can be seen from Examples 1-5, 1-9 to 1-11, when the mass percentage content of the organic sulfonate compound is from 0.1% to 2% based on the total mass of the first film layer and the second film layer, the cycling performance and storage performance of the electrochemical device are better.

[0134] As can be seen from Examples 1-5, 1-12 to 1-15, when d satisfies the condition of 8 to 14, the cycling performance and storage performance of the electrochemical device are better.

[0135] As can be seen from Examples 1-5, 1-16 to 1-20, using different types of organic sulfonate compounds can improve the cycling performance and storage performance of the electrochemical device.

[0136] As can be seen from Examples 1-5, 1-21 to 1-25, when the ratio of the area of the protruding region to the area of the first film layer is from 2% to 20%, the cycling performance and storage performance of the electrochemical device are better.

[0137] As can be seen from Examples 1-5, 1-26 to 1-31, when a certain concentration of the compound of formula (II) is further added to the electrolyte, the cycling performance and storage performance of the electrochemical device are better.

[0138] As can be seen from Examples 1-5, 1-30 to 1-37, when a certain concentration of the compound of formula (III) is further added to the electrolyte, the cycling performance and storage performance of the electrochemical device are better.

[0139] Examples 2-1 to 2-8

[0140] Except for adjusting the parameters according to Table 2, the rest are the same as Example 1-5.

[0141] The y and d of the negative electrode active material in the first film layer, and the mass percentage content x of the organic sulfonate compound based on the total mass of the first film layer and the second film layer are different.

[0142] The above-mentioned lithium ion batteries are tested for cycling performance, high-temperature storage performance and fast charging performance, and the results are shown in Table 2.

[0143] Table 2

[0144]

[0145]

[0146] As can be seen from Examples 1-5 and Examples 2-1 to 2-4 in Table 2, by using a negative electrode active material with a higher degree of defects, the fast charging performance of the battery can be effectively improved without significantly deteriorating the cycle performance and storage performance of the battery; under the condition that y is between 0.2 and 0.6, the cycle performance and storage performance of the battery are better.

[0147] As can be seen from Examples 1-5 and Examples 2-1 to 2-8, when x / (d + y) satisfies the condition of 0.0058 to 0.14, the lithium-ion battery can better balance the fast charging performance, cycle performance and storage performance.

[0148] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrochemical device, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a first film layer arranged on at least one surface of the negative electrode current collector, wherein the first film layer comprises a negative electrode active material, and a second film layer is arranged on the side of the first film layer away from the negative electrode current collector, wherein the second film layer comprises an organic sulfonate compound and a binder, wherein the mass ratio of the organic sulfonate compound to the binder is 0.001 to 100.

2. The electrochemical device according to claim 1, characterized in that Based on the total mass of the first film layer and the second film layer, the mass percentage of the organic sulfonate compound is x%, and 0.01≤x≤5.

3. The electrochemical device according to claim 2, characterized in that The peak intensity of D peak in the Raman spectrum of the negative electrode active material is 1 D , G peak intensity is I G , y=I D / I G The average volume particle size D of the negative electrode active material V 50 is d μm; The x, y, and d satisfy: 0.0017≤x / (d+y)≤0.

33.

4. The electrochemical device according to claim 3, characterized in that The electrochemical device satisfies at least one of the following conditions: (1) The mass ratio of the organic sulfonate compound to the binder is 0.01 to 20; (2)0.1≤x≤2； (3)0.2≤y≤0.8； (4)5≤d≤16； (5)0.0058≤x / (d+y)≤0.

14.

5. The electrochemical device according to claim 1, characterized in that The positive electrode sheet includes a positive electrode active material layer; the first film layer includes a protruding area that does not overlap with the positive electrode active material layer, and the ratio of the area of ​​the protruding area to the area of ​​the first film layer is 1% to 30%.

6. The electrochemical device according to any one of claims 1 to 5, characterized in that: The organic sulfonate compound includes a compound of formula (I), Among them, R 11 is selected from substituted or unsubstituted C1 to C 10 alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 substituted or unsubstituted C1 to C6 heteroalkyl, halogen atoms, amino groups or The number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P or S; 12 is selected from substituted or unsubstituted C1 to C 10 alkylene, substituted or unsubstituted C2 to C 10 an alkenylene group, a substituted or unsubstituted C1 to C6 chain heteroalkylene group, wherein the number of heteroatoms in the chain heteroalkylene group is 1 to 5, and the heteroatoms in the chain heteroalkylene group are selected from O or S; When substituted, the substituent is selected from a halogen atom, a C2 to C5 cycloalkyl group or a C6 to C 12 Aromatic groups; X 11 , X 12 Each is independently selected from Li, K or Na.

7. The electrochemical device according to claim 6, characterized in that The compound of formula (I) comprises at least one of the following compounds:

8. The electrochemical device according to claim 1, characterized in that The electrolyte comprises a compound of formula (II): Among them, R 21 , R 22 , R 23 and R 24 are independently selected from a hydrogen atom, a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkynyl, substituted or unsubstituted C1 to C 10 Any one of the heteroatom-containing functional groups of 21 , R 22 , R 23 and R 24 Any two groups in can form a ring; Based on the mass of the electrolyte, the mass percentage of the compound of formula (II) is 0.01% to 1%.

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

10. The electrochemical device according to claim 1, wherein The electrolyte comprises a compound of formula (III), wherein R1 and R3 are independently selected from C1 to C4 alkyl groups, and R2 is selected from C1 to C4 alkylene groups; Based on the mass of the electrolyte, the mass percentage of the compound of formula (III) is 0.001% to 5%.

11. The electrochemical device according to claim 1, characterized in that The electrochemical device satisfies at least one of the following characteristics: (1) The binder includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium hydroxymethyl cellulose, polyvinyl alcohol, sodium alginate, sodium polyacrylate, lithium polyacrylate, and styrene-butadiene rubber; (2) The negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon or soft carbon.

12. An electronic device, characterized in that: An electrochemical device comprising any one of claims 1 to 11.

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