Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device. The secondary battery comprises a negative pole piece and an electrolyte, the electrolyte comprises a sulfonyl compound, the sulfonyl compound comprises at least one of a compound shown in a formula I or a compound shown in a formula II, based on the mass of the electrolyte, the mass percentage content of the sulfonyl compound is W1%, and W1 is larger than or equal to 10 and smaller than or equal to 90; the negative pole piece comprises a negative current collector and a negative material layer arranged on at least one surface of the negative current collector, the negative material layer comprises a carbon nanotube cluster and silicon-based particles, the carbon nanotube cluster is composed of a plurality of carbon nanotubes, the average diameter of the carbon nanotube cluster is D [mu] m, and D is greater than or equal to 0.2 and less than or equal to 6.5. The secondary battery provided by the invention has good cycle performance and rate capability.

Description

Technical Field

[0001] The present application relates to the field of electrochemistry technology, and particularly to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, have significant advantages such as high energy density, miniaturization, and light weight, and are widely used in mobile phones, laptop computers, tablet computers, drones, electric vehicles, power tools, power storage systems, etc. Generally, a lithium-ion battery is composed of a positive electrode sheet, a negative electrode sheet, and an electrolyte. The electrolyte is responsible for maintaining the ion transport between the positive electrode sheet and the negative electrode sheet, and is also responsible for maintaining a stable interface to enable the lithium-ion battery to work stably. At present, users also put forward higher and higher requirements for the performance of secondary batteries, such as cycle performance and rate performance. Therefore, there is an urgent need to provide a secondary battery with good cycle performance and rate performance to meet the increasingly high usage requirements of people. Summary of the Invention

[0003] The purpose of the present application is to provide a secondary battery and an electronic device to improve the cycle performance and rate performance of the secondary battery. The specific technical solutions are as follows:

[0004] It should be noted that in the summary of the invention of the present application, a lithium-ion battery is used as an example of the secondary battery to explain the present application, but the secondary battery of the present application is not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0005] In the first aspect of the present application, a secondary battery is provided, which includes a negative electrode sheet and an electrolyte. The electrolyte includes a sulfonyl compound, and the sulfonyl compound includes at least one of a compound of formula I or a compound of formula II. The chemical formula of the compound of formula I is: The chemical formula of the compound of formula II is: Among them, R1 is selected from a fluorine atom, a C1-C5 alkyl group that is fully or partially substituted by fluorine, R2 and R3 are each independently selected from a C1-C5 alkyl group, R2 and R3 can be connected by a single bond to form a ring, R4 is selected from an unsubstituted or fluorine-substituted C1-C5 alkyl group. Based on the mass of the electrolyte, the mass percentage content of the sulfonyl compound is W1%, and 10 ≤ W1 ≤ 90; the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes carbon nanotube clusters and silicon-based particles. The average diameter of the carbon nanotube clusters is D μm, and 0.2 ≤ D ≤ 6.5. Among them, the "carbon nanotube clusters" are composed of multiple carbon nanotubes. Among them, at least part of the regions of the multiple carbon nanotubes are in contact and the contact regions are arranged in a bundle-like manner. At least part of the long axes of the multiple carbon nanotubes are parallel to each other. By introducing the sulfonyl compound within the above range into the electrolyte and regulating the D value of the carbon nanotube clusters in the negative electrode material layer within the above range, the electrolyte and the carbon nanotube clusters with a specific D value act synergistically, and a solid electrolyte interface film (SEI film) rich in inorganic substances such as lithium fluoride with high toughness can be formed on the surface of the silicon-based particles, improving the stability of the negative electrode interface, reducing the side reactions between the negative electrode material layer and the electrolyte, improving the cycle stability of the secondary battery. At the same time, the carbon nanotube clusters can adhere to the silicon-based particles, constructing more conductive channels between the silicon-based particles, improving the electron transfer rate between the silicon-based particles, thereby improving the cycle performance and rate performance of the secondary battery, and having a relatively high energy density.

[0006] In some embodiments of the present application, the compound of formula I includes at least one of the following compounds:

[0007]

[0008]

[0009] Selecting the above compound of formula I is beneficial to forming a solid electrolyte interface film (SEI film) rich in inorganic substances such as lithium fluoride on the surface of the silicon-based particles, improving the stability of the negative electrode interface, reducing the side reactions between the negative electrode material layer and the electrolyte, improving the cycle stability of the secondary battery, and thus being beneficial to further improving the cycle performance of the secondary battery, and having good rate performance.

[0010] In some embodiments of the present application, the compound of formula II includes at least one of the following compounds:

[0011]

[0012]

[0013] Selecting the above compound of formula II is beneficial to form a solid electrolyte interface film (SEI film) rich in inorganic substances such as lithium fluoride on the surface of the silicon-based particles, improve the stability of the negative electrode interface, reduce the side reactions between the negative electrode material layer and the electrolyte, improve the cycle stability of the secondary battery, and thus is beneficial to further improve the cycle performance of the secondary battery, while having good rate performance.

[0014] In some embodiments of the present application, the secondary battery satisfies at least one of the following conditions: (1) 20 ≤ W1 ≤ 70; (2) 0.5 ≤ D ≤ 5. When the secondary battery satisfies the above conditions, it is beneficial to further improve the cycle performance and rate performance of the secondary battery.

[0015] In some embodiments of the present application, the electrolyte further includes a first component, and the first component includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate or ethylene vinylene carbonate; based on the mass of the electrolyte, the mass percentage content of the first component is W2%, 0.5 ≤ W2 ≤ 15, preferably, 1 ≤ W2 ≤ 8. Selecting an electrolyte including the above types of first components and regulating the mass percentage content W2% of the first component within the above range is beneficial to improve the cycle performance and rate performance of the secondary battery.

[0016] In some embodiments of the present application, the average diameter of the carbon nanotubes is d nm, 3 ≤ d ≤ 40, preferably, 5 ≤ d ≤ 20. By regulating the average diameter d of the carbon nanotubes within the above range, the carbon nanotube clusters are more likely to adhere to the silicon-based particles, which is beneficial to construct more conductive channels between the silicon-based particles, improve the electron transfer rate between the silicon-based particles, and thus is beneficial to improve the cycle performance and rate performance of the secondary battery.

[0017] In some embodiments of the present application, the average length of the carbon nanotube clusters is L μm, 3 ≤ L ≤ 40, preferably, 5 ≤ L ≤ 30. By regulating the average length L of the carbon nanotube clusters within the above range, the carbon nanotube clusters can adhere to the silicon-based particles, which is beneficial to construct more conductive channels between the silicon-based particles, improve the electron transfer rate between the silicon-based particles, and thus is beneficial to improve the cycle performance and rate performance of the secondary battery.

[0018] In some embodiments of the present application, the silicon-based particles include at least one of pure silicon, silicon alloy, silicon-carbon composite material or silicon-oxygen composite material. Selecting the above materials for the silicon-based particles is beneficial to improve the energy density of the secondary battery while having good cycle performance and rate performance.

[0019] In some embodiments of the present application, the carbon nanotubes include multi-walled carbon nanotubes.

[0020] In some embodiments of the present application, based on the mass of the negative electrode material layer, the mass percentage content of the carbon nanotube clusters is 0.1% to 2%. By regulating the mass percentage content of the carbon nanotube clusters within the above range, it is beneficial to construct more conductive channels between the silicon-based particles, form a long-range conductive network, improve the electron transfer rate between the silicon-based particles, and thus is beneficial to improving the cycle performance and rate performance of the secondary battery, while the energy density of the secondary battery is relatively high.

[0021] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. The electronic device of the present application has good use performance.

[0022] Advantages of the present application:

[0023] The present application provides a secondary battery and an electronic device. The secondary battery includes a negative electrode tab and an electrolyte. The electrolyte includes a sulfonyl compound, and the sulfonyl compound includes at least one of a compound of Formula I or a compound of Formula II. Based on the mass of the electrolyte, the mass percentage content of the sulfonyl compound is W1%, 10 ≤ W1 ≤ 90; the negative electrode tab includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes carbon nanotube clusters and silicon-based particles. The average diameter of the carbon nanotube clusters is D μm, 0.2 ≤ D ≤ 6.5. By introducing the sulfonyl compound within the above range into the electrolyte and regulating the D value of the carbon nanotube clusters in the negative electrode material layer within the above range, the electrolyte and the carbon nanotube clusters with a specific D value act synergistically to form a solid electrolyte interface film (SEI film) rich in inorganic substances such as lithium fluoride with high toughness on the surface of the silicon-based particles, improve the stability of the negative electrode interface, reduce the side reactions between the negative electrode material layer and the electrolyte, improve the cycle stability of the secondary battery. At the same time, the carbon nanotube clusters can adhere to the silicon-based particles, construct more conductive channels between the silicon-based particles, improve the electron transfer rate between the silicon-based particles, thereby improving the cycle performance and rate performance of the secondary battery, while the energy density is relatively high.

[0024] Of course, it is not necessarily required to achieve all the above advantages simultaneously when implementing any product or method of the present application. Detailed implementation manners

[0025] Next, the technical solutions in the present application will be described clearly and completely in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0026] It should be noted that in the specific embodiments of the present application, a lithium-ion battery is taken as an example of the secondary battery to explain the present application. However, the secondary battery of the present application is not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0027] In a first aspect of the present application, a secondary battery is provided, which includes a negative electrode sheet and an electrolyte. The electrolyte includes a sulfonyl compound, and the sulfonyl compound includes at least one of a compound of Formula I or a compound of Formula II. The chemical formula of the compound of Formula I is: The chemical formula of the compound of Formula II is: Wherein, R1 is selected from a fluorine atom, a C1-C5 alkyl group that is fully or partially substituted by fluorine, R2 and R3 are each independently selected from a C1-C5 alkyl group, R2 and R3 can be connected by a single bond to form a ring, R4 is selected from an unsubstituted or fluorine-substituted C1-C5 alkyl group. Based on the mass of the electrolyte, the mass percentage content of the sulfonyl compound is W1%, 10 ≤ W1 ≤ 90. Preferably, 20 ≤ W1 ≤ 70. For example, the value of W1 can be 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90 or a range composed of any two of these values. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes carbon nanotube clusters and silicon-based particles. The carbon nanotube clusters are composed of multiple carbon nanotubes. The average diameter of the carbon nanotube clusters is D μm, 0.2 ≤ D ≤ 6.5. Preferably, 0.5 ≤ D ≤ 5. For example, the value of D can be 0.2, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 or a range composed of any two of these values.

[0028] Among them, the "carbon nanotube clusters" are composed of multiple carbon nanotubes. Among them, at least part of the regions of the multiple carbon nanotubes are in contact and the contact regions are arranged in a bundle shape. At least part of the long axes of the multiple carbon nanotubes are parallel to each other. Among them, being parallel to each other includes the case where the included angle between the long axes of the carbon nanotubes is less than or equal to 20°. When testing the diameter of the carbon nanotube clusters, a region where the multiple carbon nanotubes are in contact and the long axes are parallel to each other is selected for testing.

[0029] The negative electrode material layer of the present application includes silicon-based particles. The silicon-based particles have a high specific capacity, which can improve the energy density of the secondary battery. At the same time, the sulfonyl compound contained in the electrolyte can form a solid electrolyte interface film (SEI film) rich in inorganic substances such as lithium fluoride on the surface of the silicon-based particles, improve the stability of the negative electrode interface, reduce the side reactions between the negative electrode material layer and the electrolyte, improve the cycle stability of the secondary battery, and thus improve the cycle performance of the secondary battery. However, the SEI film rich in inorganic substances on the negative electrode surface will affect the electron transfer between the silicon-based particles, thereby affecting the rate performance of the secondary battery. In the present application, by adding carbon nanotube clusters to the negative electrode material layer and controlling the average diameter D of the carbon nanotube clusters within the scope of the present application, the carbon nanotube clusters can adhere to the silicon-based particles, build more conductive channels between the silicon-based particles, improve the electron transfer rate between the silicon-based particles, and thus improve the rate performance of the secondary battery. Therefore, by introducing the sulfonyl compound within the above range into the electrolyte and controlling the D value of the carbon nanotube clusters in the negative electrode material layer within the above range, the electrolyte and the negative electrode plate act synergistically, which can improve the cycle performance and rate performance of the secondary battery, and at the same time has a high energy density.

[0030] When the value of W1 is too small, for example, less than 10, it is difficult to form an SEI film rich in inorganic substances such as lithium fluoride on the surface of the silicon-based particles. The stability of the negative electrode interface is poor, there are more side reactions between the negative electrode material layer and the electrolyte, and the cycle stability of the secondary battery is poor, thereby affecting the cycle performance of the secondary battery. When the value of W1 is too large, for example, greater than 90, the SEI film rich in inorganic substances on the negative electrode surface is relatively thick, the ion transport is blocked, and it will also affect the electron transfer between the silicon-based particles, thereby affecting the cycle performance and rate performance of the secondary battery. When the value of D is too small, for example, less than 0.2, the electron transfer rate between the silicon-based particles is slow, thereby affecting the cycle performance and rate performance of the secondary battery. When the value of D is too large, for example, greater than 6.5, the carbon nanotube clusters are prone to agglomeration in the negative electrode slurry and are difficult to adhere to the silicon-based particles to form a highly efficient electron network, thereby affecting the cycle performance and rate performance of the secondary battery.

[0031] In some embodiments, R1 is selected from a fluorine atom, difluoromethyl, trifluoromethyl, tetrafluoroethyl, pentafluoroethyl, heptafluoropropyl or nonafluorobutyl; R2 is selected from methyl, ethyl, propyl or butyl; R3 is selected from methyl, ethyl, propyl or butyl; R4 is selected from methyl, ethyl, propyl, butyl, pentyl, fluoroethyl, difluoroethyl or trifluoroethyl. The sulfonyl compound containing the groups within the above range is beneficial to form an SEI film rich in inorganic substances such as lithium fluoride on the surface of the silicon-based particles, improve the stability of the negative electrode interface, and thus is beneficial to improving the cycle performance of the secondary battery, and at the same time has good rate performance.

[0032] In some embodiments of the present application, the compound of formula I includes at least one of the following compounds:

[0033]

[0034]

[0035] Selecting the compound of Formula I above is conducive to forming an SEI film rich in inorganic substances such as lithium fluoride on the surface of silicon-based particles, improving the stability of the negative electrode interface, reducing the side reactions between the negative electrode material layer and the electrolyte, improving the cycle stability of the secondary battery, and can cooperate with the negative electrode sheet containing carbon nanotube clusters, thereby being conducive to further improving the cycle performance of the secondary battery, while having good rate performance.

[0036] In some embodiments of the present application, the compound of Formula II includes at least one of the following compounds:

[0037]

[0038] Selecting the compound of Formula II above is conducive to forming an SEI film rich in inorganic substances such as lithium fluoride on the surface of silicon-based particles, improving the stability of the negative electrode interface, reducing the side reactions between the negative electrode material layer and the electrolyte, improving the cycle stability of the secondary battery, and can cooperate with the negative electrode sheet containing carbon nanotube clusters, thereby being conducive to further improving the cycle performance of the secondary battery, while having good rate performance.

[0039] In some embodiments of the present application, the electrolyte further includes a first component, and the first component includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate or ethylene vinylene carbonate. Selecting the electrolyte including the first component of the above types is conducive to cooperating with the sulfonyl compound to form a tough and dense SEI film on the negative electrode surface, reducing the contact between the negative electrode active material and the electrolyte, reducing the side reactions between the negative electrode material layer and the electrolyte, enabling the secondary battery to have a longer cycle life, improving the cycle stability of the secondary battery, and can cooperate with the negative electrode sheet containing carbon nanotube clusters, thereby being conducive to improving the cycle performance and rate performance of the secondary battery.

[0040] In some embodiments of the present application, based on the mass of the electrolyte, the mass percentage of the first component is W2%, where 0.5 ≤ W2 ≤ 15, preferably 1 ≤ W2 ≤ 8. For example, the value of W2 can be 0.5, 0.7, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range composed of any two of these numerical values. By controlling the mass percentage W2% of the first component within the above range, it is beneficial to form a tough and dense SEI film on the negative electrode surface synergistically with the sulfonyl compound, reduce the contact between the negative electrode active material and the electrolyte, reduce the side reactions between the negative electrode material layer and the electrolyte, enable the secondary battery to have a longer cycle life, improve the cycle stability of the secondary battery, and can act synergistically with the negative electrode sheet containing carbon nanotube clusters, thereby being beneficial to improving the cycle performance and rate performance of the secondary battery.

[0041] In the present application, the electrolyte further includes a lithium salt and other non-aqueous solvents. The present application places no particular limitation on the lithium salt, as long as the object of the present application can be achieved. For example, the lithium salt can include, but is not limited to, at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. The present application places no particular limitation on the content of the lithium salt in the electrolyte, as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage of the lithium salt is 8% to 30%.

[0042] The present application places no particular limitation on the other non-aqueous solvents, as long as the object of the present application can be achieved. For example, the other non-aqueous solvents can include, but are not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents.

[0043] The above-mentioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The above-mentioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The above-mentioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), or butylene carbonate (BC). The fluorinated carbonate compounds may include, but are not limited to, at least one of 1,2-difluoroethylene carbonate, 1,1-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 trifluoromethyl ethylene carbonate. The above-mentioned carboxylate 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, decanolide, valerolactone, or caprolactone. The above-mentioned 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 above-mentioned 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-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application does not particularly limit the content of other non-aqueous solvents in the electrolyte, as long as the object of the present application can be achieved. For example, based on the mass of the electrolyte, the mass percentage content of other non-aqueous solvents is 0% to 81.5%.

[0044] In some embodiments, the electrolyte may include a sulfonyl compound, a lithium salt, and other non-aqueous solvents, and the mass percentage contents of the sulfonyl compound, the lithium salt, and the other non-aqueous solvents are as described above. The secondary battery including the above-mentioned electrolyte has good cycle performance and rate performance.

[0045] In some embodiments, the electrolyte may include a sulfonyl compound, a first component, a lithium salt, and other non-aqueous solvents, and the mass percentage contents of the sulfonyl compound, the first component, the lithium salt, and the other non-aqueous solvents are as described above. The secondary battery including the above-mentioned electrolyte has good cycle performance and rate performance.

[0046] In some embodiments of the present application, the average diameter of the carbon nanotubes is d nm, where 3 ≤ d ≤ 40, preferably 5 ≤ d ≤ 20. For example, the value of d can be 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, or a range composed of any two of these numerical values. By controlling the average diameter d of the carbon nanotubes within the above range, the carbon nanotube clusters can adhere to the silicon-based particles, which is beneficial to constructing more conductive channels between the silicon-based particles, improving the electron transfer rate between the silicon-based particles, and can cooperate with the electrolyte containing sulfonyl compounds, thereby being beneficial to improving the cycle performance and rate performance of the secondary battery.

[0047] In some embodiments of the present application, the average length of the carbon nanotube clusters is L μm, where 3 ≤ L ≤ 40, preferably 5 ≤ L ≤ 30. For example, the value of L can be 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, or a range composed of any two of these numerical values. By controlling the average length L of the carbon nanotube clusters within the above range, the carbon nanotube clusters can adhere to the silicon-based particles, which is beneficial to constructing more conductive channels between the silicon-based particles, improving the electron transfer rate between the silicon-based particles, is easy to implement in the process, and can cooperate with the electrolyte containing sulfonyl compounds, thereby being beneficial to improving the cycle performance and rate performance of the secondary battery.

[0048] The preparation method of the carbon nanotube clusters in this application is not particularly limited, as long as the purpose of this application can be achieved. For example, the preparation method of the carbon nanotube clusters may include but is not limited to the following steps: adding multi-walled carbon nanotubes and a dispersant in a mass ratio of 1∶(0.1 to 10) to a dispersion medium, and obtaining a mixed solution with a solid content of 1.5 wt% to 20 wt% after mixing evenly; obtaining a dispersion of the carbon nanotube clusters by applying a shear force to the mixed solution. Among them, the dispersant may include but is not limited to at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose; the dispersion medium may include but is not limited to deionized water, dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol, heptanol or octanol; diols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, acetone, methyl ethyl ketone, methyl propyl ketone, cyclopentanone, ethyl acetate, γ-butyrolactone or ε-propiolactone; based on the mass of the mixed solution, the mass percentage of the multi-walled carbon nanotubes may be 1% to 4%; the machine for applying the shear force to the mixed solution may include but is not limited to at least one of a homogenizer, a bead mill, a ball mill, a sand mill, a basket crusher, a grinder, a general stirrer, a transparent mixer, a pin mill, a mixing device of a TK mixer or an ultrasonic dispersion device.

[0049] In the above preparation method of the carbon nanotube clusters, when applying the shear force to the mixed solution using a ball mill, the specific steps are: adding the mixed solution to a container containing sand grinding balls, that is, a ball mill, and rotating the container to obtain a dispersion of the carbon nanotube clusters. Among them, the average diameter of the sand grinding balls may be 0.5 mm to 2.5 mm, the rotation speed of the container may be 500 rpm to 6000 rpm, and the ball milling time may be 0.5 h to 2 h.

[0050] In the present application, the average diameter D of the carbon nanotube clusters can be adjusted by controlling the average diameter of the grinding balls, the rotation speed of the container, and the ball milling time. For example, when other conditions remain unchanged, the larger the average diameter of the grinding balls, the larger the average diameter D of the carbon nanotube clusters; the smaller the average diameter of the grinding balls, the smaller the average diameter D of the carbon nanotube clusters. When other conditions remain unchanged, the slower the rotation speed of the container, the larger the average diameter D of the carbon nanotube clusters; the faster the rotation speed of the container, the smaller the average diameter D of the carbon nanotube clusters. When other conditions remain unchanged, the shorter the ball milling time, the larger the average diameter D of the carbon nanotube clusters; the longer the ball milling time, the smaller the average diameter D of the carbon nanotube clusters.

[0051] In the present application, the average length L of the carbon nanotube clusters can be adjusted by controlling the average length of the carbon nanotubes. For example, when other conditions remain unchanged, as the average length of the carbon nanotubes increases, the average length L of the carbon nanotube clusters increases; as the average length of the carbon nanotubes decreases, the average length L of the carbon nanotube clusters decreases.

[0052] In some embodiments of the present application, the silicon-based particles include at least one of pure silicon, silicon alloys, silicon-carbon composites, or silicon-oxygen composites (SiOx (0 < x ≤ 2)), wherein the silicon alloys can include at least one of lithium-silicon alloys, silicon-germanium alloys, silicon-tin alloys, or silicon-aluminum alloys; the mass ratio of silicon element to carbon element in the silicon-carbon composites can be 1∶(0.4 to 3). Selecting the above materials for the silicon-based particles is beneficial to improving the energy density of the secondary battery while having good cycle performance and rate performance.

[0053] In some embodiments, based on the mass of the negative electrode material layer, the mass percentage content of the silicon-based particles is 5% to 98%. For example, the mass percentage content of the silicon-based particles can be 5%, 10%, 15%, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 98%, or a range composed of any two of these values.

[0054] In some embodiments of the present application, based on the mass of the negative electrode material layer, the mass percentage content of the carbon nanotube clusters is 0.1% to 2%. For example, the mass percentage content of the carbon nanotube clusters can be 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, or a range composed of any two of these values. By controlling the mass percentage content of the carbon nanotube clusters within the above range, it is beneficial to construct more conductive channels between the silicon-based particles, form a long-range conductive network, improve the electron transfer rate between the silicon-based particles, and can cooperate with the electrolyte containing sulfonyl compounds, thereby being beneficial to improving the cycle performance and rate performance of the secondary battery, while the secondary battery has a relatively high energy density.

[0055] In some embodiments, the negative electrode material layer further includes a negative electrode active material other than the silicon-based particles. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode active material other than the silicon-based particles is 0% to 90%. For example, the mass percentage of the negative electrode active material other than the silicon-based particles can be 0%, 10%, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, or a range composed of any two of these values. The present application does not particularly limit the type of the negative electrode active material other than the silicon-based particles, as long as the purpose of the present application can be achieved. For example, the negative electrode active material other than the silicon-based particles may include at least one of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 , Li-Al alloy, or metallic lithium.

[0056] In some embodiments, the negative electrode material layer further includes a negative electrode binder. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode binder is 0.5% to 4%. For example, the mass percentage of the negative electrode binder can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or a range composed of any two of these values. The present application does not particularly limit the type of the negative electrode binder, as long as the purpose of the present application can be achieved. For example, the negative electrode binder may include at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamideimide, styrene-butadiene rubber, or polyvinylidene fluoride.

[0057] In the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The above "the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be provided on one surface of the negative electrode current collector along its thickness direction, or can be provided on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of the surface of the negative electrode current collector, or can be a partial area of the surface of the negative electrode current collector. The present application does not particularly limit this, as long as the purpose of the present application can be achieved.

[0058] The present application does not particularly limit the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector. Exemplarily, the composite current collector can be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0059] In the present application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode material 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 20 μm, and the thickness of the single-sided negative electrode material layer is 30 μm to 130 μm.

[0060] In the present application, the secondary battery further includes a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be provided on one surface of the positive electrode current collector along its thickness direction, or can be provided on two surfaces of the positive electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of the positive electrode current collector or a partial area of the positive electrode current collector, and there is no particular limitation in the present application, as long as the object of the present application can be achieved.

[0061] There is no particular limitation on the positive electrode current collector in the present application, as long as the object of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil or composite current collector (such as aluminum-carbon composite current collector), etc.

[0062] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance capable of reversibly inserting and extracting active ions such as lithium ions. The positive electrode material layer can be one layer or multiple layers, and each layer in the multiple positive electrode material layers can contain the same or different positive electrode active materials. There is no particular limitation on the positive electrode active material in the present application, as long as the object of the present application can be achieved. For example, the positive electrode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate or lithium titanate. The above-mentioned lithium nickel cobalt manganese oxide can include LiNi 0.95 Co 0.03 Mn 0.02 O2(Ni95), LiNi 0.91 Co 0.03 Mn 0.06 O2(Ni91), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3At least one of O2 (NCM111). In the present application, the positive electrode active material may further include a non-metallic element. For example, the non-metallic element includes at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur.

[0063] The positive electrode material layer of the present application further includes a positive electrode conductive agent and a positive electrode binder. The present application places no particular limitation on the positive electrode conductive agent and the positive electrode binder in the positive electrode material layer, as long as the object of the present application can be achieved. For example, the positive electrode conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers. The conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanofibers. The above-mentioned metal materials may include, but are not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The positive electrode binder may be at least one of the above-mentioned negative electrode binders. The present application places no particular limitation on the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder in the positive electrode material 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.

[0064] In the present application, there is no particular limitation on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm; the thickness of the single-sided positive electrode material layer is 30 μm to 120 μm.

[0065] In the present application, the secondary battery further includes a separator. The present application places no particular limitation on the separator, as long as the object of the present application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of the separator may include, but is not limited to, at least one of a woven film, a non-woven film, a microporous film, a composite film, a rolled film or a spun film.

[0066] In some embodiments, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric membrane or a composite membrane having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0067] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, 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.

[0068] In some embodiments, the inorganic layer includes inorganic particles and an inorganic layer binder. There is no particular limitation on the inorganic particles in the present application. For example, the inorganic particles may include at least one of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. There is no particular limitation on the inorganic layer binder in the present application. For example, it may be at least one of the above-mentioned negative electrode binders. In some embodiments, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0069] In the present application, there is no particular limitation on the thickness of the separator, as long as the object of the present application can be achieved. For example, the thickness of the separator may be 3 μm to 30 μm.

[0070] The secondary battery further includes a housing for accommodating the positive electrode plate, the separator, the negative electrode plate, and the electrolyte, as well as other components known in the field of secondary batteries. The present application does not limit the above-mentioned other components. There is no particular limitation on the housing in the present application, and it may be a housing well-known in the art as long as the object of the present application can be achieved. For example, the housing may be a hard shell housing or a flexible housing. The material of the hard shell housing may be metal, and the present application does not limit the type of metal. A metal hard shell housing known in the art may be used as long as the object of the present application can be achieved. The flexible housing may be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0071] There is no particular limitation on the secondary battery of the present application, and it may include any device that generates an electrochemical reaction. In some embodiments, the secondary battery may include, but is not limited to: lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, etc.

[0072] The preparation process of the secondary battery of the present application is well-known to those skilled in the art, and the present application has no special limitations. For example, the preparation process of the secondary battery may include, but is not limited to, the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and winding, folding, etc. as needed to obtain a wound electrode assembly, placing the electrode assembly into a housing, injecting electrolyte into the housing and sealing it to obtain a secondary battery. Alternatively, stack the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and then fix the four corners of the entire laminated structure with tape to obtain a laminated electrode assembly, place the electrode assembly into a housing, inject electrolyte into the housing and seal it to obtain a secondary battery. In addition, an overcurrent protection element, a guide plate, etc. can be placed in the housing as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0073] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. The electronic device of the present application has good performance in use.

[0074] The present application does not particularly limit the type of the electronic device, 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 supply, 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.

[0075] Examples

[0076] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments 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.

[0077] Testing methods and equipment:

[0078] Measurement of the average diameter D and average length L of the carbon nanotube clusters and the average diameter d of the carbon nanotubes

[0079] After discharging the lithium-ion battery at a constant current of 0.2C until 3V, the negative electrode sheet sample was disassembled. After cleaning the above sample with dimethyl carbonate (DMC), it was dried at 60°C. The cross-section of the negative electrode sheet along the thickness direction was obtained by brittle fracture with liquid nitrogen, and the above cross-section was observed under a scanning electron microscope (SEM). Five different positions were tested, and the diameters and lengths of a total of 20 carbon nanotube clusters and the diameters of carbon nanotubes were measured. The average diameter D and average length L of the carbon nanotube clusters and the average diameter d of the carbon nanotubes were calculated respectively by taking their averages.

[0080] Cycling performance test

[0081] The lithium-ion battery was placed in a constant temperature environment of 25°C and left to stand for 30 min to reach a constant temperature state of 25°C. It was charged at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V until the current reached 0.025C, left to stand for 5 min, and then discharged at a constant current of 0.5C to 3.0V. The initial discharge capacity was recorded as C0. The above charge-discharge steps were cycled 500 times, and the discharge capacity after 500 cycles was recorded as C1. The cycling capacity retention rate (%) = C1 / C0 × 100%.

[0082] Rate performance test

[0083] The lithium-ion battery was placed in a constant temperature environment of 25°C and left to stand for 30 min to reach a constant temperature state of 25°C. It was charged at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V until the current reached 0.025C, discharged at a constant current of 0.2C to 3.0V, and the discharge capacity at 0.2C at 25°C was recorded as C2. Then it was charged at a constant current of 0.5C to 4.5V, charged at a constant voltage of 4.5V until the current reached 0.025C, left to stand for 10 min, and then discharged at a constant current of 2C to 3.0V. The discharge capacity at 2C at 25°C was recorded as C3. The discharge capacity retention rate at 2C rate (%) = C3 / C2 × 100%.

[0084] Example 1-1

[0085] <Preparation of electrolyte>

[0086] In an argon atmosphere glove box with a water content of less than 10 ppm, diethyl carbonate and ethylene carbonate were mixed in a mass ratio of 1:1 to obtain a basic solvent. Then, a sulfonyl compound of formula I-1 and lithium salt lithium hexafluorophosphate (LiPF6) were added to the basic solvent and mixed evenly to obtain an electrolyte. Among them, based on the mass of the electrolyte, the mass percentage content of the lithium salt LiPF6 was 8%, the mass percentage content W1% of the sulfonyl compound was as shown in Table 1, and the balance was the basic solvent.

[0087] <Preparation of carbon nanotube clusters>

[0088] Multi-walled carbon nanotubes and sodium carboxymethyl cellulose as a dispersant were added to deionized water as a dispersion medium at a mass ratio of 1:2. After mixing evenly, a mixed solution with a solid content of 10 wt% was obtained. The mixed solution was added to a container containing sanding balls, i.e., a ball mill, and the container was rotated to obtain a dispersion of carbon nanotube clusters. Among them, the average diameter of the sanding balls was 1.5 mm, the rotation speed of the container was 3000 rpm, and the ball milling time was 1 h.

[0089] <Preparation of negative electrode sheet>

[0090] The silicon-based particulate silicon-carbon composite material SiC, artificial graphite, the dispersion of carbon nanotube clusters, and the negative electrode binder styrene-butadiene rubber were mixed, and deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%. After being stirred evenly by a vacuum mixer, a negative electrode slurry was obtained. Among them, the mass ratio of the silicon-based particulate silicon-carbon composite material SiC, artificial graphite, carbon nanotube clusters, and the negative electrode binder styrene-butadiene rubber in the negative electrode slurry was 10:87.8:1:1.2. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector with a thickness of 6 μm and dried at 120 °C to obtain a negative electrode sheet with a single-sided coated negative electrode material layer. Then, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode material layer. After drying at 120 °C, it was cold-pressed, and then cut into pieces and welded with tabs to obtain a negative electrode sheet with a specification of 78 mm × 875 mm for use. Among them, the thickness of the single-sided negative electrode material layer was 54.5 μm, and the coating weight of the single-sided negative electrode material layer was 142 mg / 1540 mm 2 , the average diameter D and average length L of the carbon nanotube clusters and the average diameter d of the carbon nanotubes are shown in Table 1.

[0091] <Preparation of positive electrode sheet>

[0092] The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%. After being stirred evenly by a vacuum mixer, a positive electrode slurry was obtained. The positive electrode slurry was evenly coated on one surface of an aluminum foil positive electrode current collector with a thickness of 10 μm and dried at 85 °C to obtain a positive electrode sheet with a single-sided coated positive electrode material layer. Then, the above steps were repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a double-sided coated positive electrode material layer. After coating, the positive electrode sheet was cold-pressed, and then cut into pieces and welded with tabs to obtain a positive electrode sheet with a specification of 74 mm × 867 mm for use. Among them, the coating weight of the single-sided positive electrode material layer was 267.8 mg / 1540 mm 2 , and the thickness of the single-sided positive electrode material layer was 42 μm.

[0093] <Separator>

[0094] A polyethylene (PE) film with a thickness of 7 μm is used.

[0095] <Preparation of Lithium-Ion Battery>

[0096] Stack the above-prepared positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed in the middle of the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging shell, dried in a vacuum oven at 85 °C for 12 h to remove moisture, injected with the above-prepared electrolyte, and then subjected to vacuum packaging, standing, formation (constant current charging at 0.02C to 3.5V, and then constant current charging at 0.1C to 3.9V), shaping, capacity testing and other processes to obtain a lithium-ion battery.

[0097] Examples 1-2 to Examples 1-29

[0098] Except for adjusting the relevant preparation parameters according to Table 1, the rest are the same as in Example 1-1. Among them, when the mass percentage content W1% of the sulfonyl compound changes, the mass percentage content of the base solvent changes accordingly, the proportion of each component in the base solvent remains unchanged, and the mass percentage content of the lithium salt LiPF6 remains unchanged; when the mass percentage content of the carbon nanotube clusters in the negative electrode material layer changes, the mass percentage content of artificial graphite changes accordingly, and the mass percentage contents of the silicon-based particles and the negative electrode binder remain unchanged; the molar ratio of silicon element to oxygen element in the silicon-oxygen composite material in Examples 1-29 is 1:1.

[0099] Example 2-1

[0100] Except that <Preparation of Electrolyte> adopts the following preparation method, the rest are the same as in Example 1-1.

[0101] <Preparation of Electrolyte>

[0102] In a glove box under an argon atmosphere with a water content of less than 10 ppm, diethyl carbonate and ethylene carbonate are mixed in a mass ratio of 1:1 to obtain a base solvent, and then a sulfonyl compound of formula I-1, a first component fluoroethylene carbonate, and a lithium salt lithium hexafluorophosphate (LiPF6) are added to the base solvent and mixed evenly to obtain an electrolyte. Among them, based on the mass of the electrolyte, the mass percentage content W1% of the sulfonyl compound is 50%, the mass percentage content W2% of the first component fluoroethylene carbonate is 5%, the mass percentage content of the lithium salt LiPF6 is 8%, and the balance is the base solvent.

[0103] Examples 2-2 to Examples 2-7

[0104] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as in Example 2-1. Among them, when the mass percentage content W2% of the first component changes, the mass percentage content of the base solvent changes accordingly, the proportions of the components in the base solvent remain unchanged, and the mass percentage contents of the sulfonyl compound and the lithium salt LiPF6 remain unchanged.

[0105] Comparative Example 1

[0106] Except for not including <Preparation of Carbon Nanotube Clusters>, replacing the carbon nanotube clusters with acetylene black as the negative electrode conductive agent in <Preparation of Negative Electrode Sheet>, and using the following preparation method for <Preparation of Electrolyte>, the rest is the same as in Example 1-1.

[0107] <Preparation of Electrolyte>

[0108] In a glove box under an argon atmosphere with a water content of less than 10 ppm, diethyl carbonate and ethylene carbonate were mixed in a mass ratio of 1:1 to obtain a base solvent, and then lithium hexafluorophosphate (LiPF6) was added to the base solvent and mixed evenly to obtain an electrolyte. Among them, based on the mass of the electrolyte, the mass percentage content of the lithium salt LiPF6 was 8%, and the balance was the base solvent.

[0109] Comparative Example 2

[0110] Except that <Preparation of Electrolyte> is the same as in Comparative Example 1, the rest is the same as in Example 1-1.

[0111] Comparative Example 3

[0112] Except for not including <Preparation of Carbon Nanotube Clusters> and replacing the carbon nanotube clusters with acetylene black as the negative electrode conductive agent in <Preparation of Negative Electrode Sheet>, the rest is the same as in Example 1-1.

[0113] Comparative Examples 4 to 7

[0114] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Example 1-1. Among them, when the mass percentage content W1% of the sulfonyl compound changes, the mass percentage content of the base solvent changes accordingly, the proportions of the components in the base solvent remain unchanged, and the mass percentage content of the lithium salt LiPF6 remains unchanged.

[0115] The preparation parameters and performance parameters of each example and comparative example are shown in Table 1 and Table 2.

[0116] Table 1

[0117]

[0118]

[0119] Note: (1) " / " in Table 1 indicates no relevant preparation parameters; (2) in Examples 1-10, the "sulfonyl compound" is "Formula I-1 + Formula II-1", and "W1(%)" is "25 + 25", indicating that the sulfonyl compound is the compound of Formula I-1 and the compound of Formula II-1. Based on the total mass of the electrolyte, the mass percentage of the compound of Formula I-1 is 25%, and the mass percentage of the compound of Formula II-1 is 25%.

[0120] It can be seen from Examples 1-1 to 1-29 and Comparative Examples 1 to 7 that the electrolyte containing the sulfonyl compound and the negative electrode sheet containing the carbon nanotube clusters can act synergistically. In Comparative Example 1, the negative electrode sheet does not include carbon nanotube clusters and the electrolyte does not include the sulfonyl compound; in Comparative Example 2, the electrolyte does not include the sulfonyl compound; in Comparative Example 3, the negative electrode sheet does not include carbon nanotube clusters; in Comparative Examples 4 and 5, the mass percentage W1% of the sulfonyl compound in the electrolyte is not within the scope of this application; in Comparative Examples 6 and 7, the average diameter D of the carbon nanotube clusters is not within the scope of this application. The cycle capacity retention rate and / or the 2C rate discharge capacity retention rate of the lithium-ion batteries in Comparative Examples 1 to 7 are smaller, indicating that the lithium-ion batteries cannot balance the cycle performance and the rate performance at the same time.

[0121] The type of the sulfonyl compound will affect the cycle performance and the rate performance of the lithium-ion battery. It can be seen from Examples 1-1 to 1-10 that when the sulfonyl compound within the scope of this application is selected, the cycle capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0122] The mass percentage W1% of the sulfonyl compound will affect the cycle performance and the rate performance of the lithium-ion battery. It can be seen from Example 1-1, Examples 1-11 to 1-14, Comparative Examples 4 and 5 that when the value of W1 is too small, such as in Comparative Example 4, the cycle capacity retention rate of the lithium-ion battery is smaller; when the value of W1 is too large, such as in Comparative Example 5, the cycle capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are smaller, indicating that the lithium-ion battery cannot balance the cycle performance and the rate performance at the same time. When the value of W1 is within the scope of this application, the cycle capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0123] The average diameter D of the carbon nanotube clusters affects the cycling performance and rate performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-15 to 1-18, Comparative Example 6 and Comparative Example 7, when the value of D is too small, such as in Comparative Example 6, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are smaller; when the value of D is too large, such as in Comparative Example 7, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are smaller, indicating that the lithium-ion battery cannot balance the cycling performance and rate performance simultaneously. When the value of D is within the scope of this application, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycling performance and rate performance.

[0124] The average diameter d of the carbon nanotubes affects the cycling performance and rate performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-19 to 1-22, when the value of d is within the scope of this application, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycling performance and rate performance.

[0125] The average length L of the carbon nanotube clusters affects the cycling performance and rate performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-23 to 1-26, when the value of L is within the scope of this application, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycling performance and rate performance, and is also easy to implement in terms of process.

[0126] The mass percentage content of the carbon nanotube clusters affects the cycling performance and rate performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-27 to 1-28, when the mass percentage content of the carbon nanotube clusters is within the scope of this application, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycling performance and rate performance.

[0127] The type of silicon-based particles affects the cycling performance and rate performance of the lithium-ion battery. As can be seen from Examples 1-1, 1-29, when silicon-based particles within the scope of this application are selected, the cycling capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are larger, indicating that the lithium-ion battery has good cycling performance and rate performance.

[0128] Table 2

[0129]

[0130] Note: " / " in Table 2 indicates no relevant preparation parameters.

[0131] The mass percentage content W2% of the first component will affect the cycle performance and rate performance of the lithium-ion battery. It can be seen from Examples 1-1, 2-1 to 2-6 that when the value of W2 is within the scope of this application, the cycle capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are relatively large, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0132] The type of the first component will affect the cycle performance and rate performance of the lithium-ion battery. It can be seen from Examples 2-1 and 2-7 that when the first component within the scope of this application is selected, the cycle capacity retention rate and the 2C rate discharge capacity retention rate of the lithium-ion battery are relatively large, indicating that the lithium-ion battery has good cycle performance and rate performance.

[0133] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method or article.

[0134] Each embodiment in this specification is described in a related manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

[0135] The above are only the preferred embodiments of this application, and are not intended to limit this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application.

Claims

1. A secondary battery, which includes a negative electrode plate and an electrolyte, the electrolyte includes a sulfonyl compound, and the sulfonyl compound includes at least one of a compound of Formula I or a compound of Formula II, The chemical formula of the compound of Formula I is: The chemical formula of the compound of Formula II is: Among them, R1 is selected from a fluorine atom, a C1 to C5 alkyl group that is fully or partially substituted by fluorine, R2 and R3 are each independently selected from a C1 to C5 alkyl group, R2 and R3 may be connected by a single bond to form a ring, and R4 is selected from an unsubstituted or fluorine-substituted C1 to C5 alkyl group, Based on the mass of the electrolyte, the mass percentage content of the sulfonyl compound is W1%, 10 ≤ W1 ≤ 90; The negative electrode plate includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes carbon nanotube clusters and silicon-based particles. The carbon nanotube clusters are composed of multiple carbon nanotubes, and the average diameter of the carbon nanotube clusters is D μm, 0.2 ≤ D ≤ 6.

5.

2. The secondary battery according to claim 1, wherein, The compound of Formula I includes at least one of the following compounds:

3. The secondary battery according to claim 1, wherein, The compound of Formula II includes at least one of the following compounds:

4. The secondary battery according to claim 1, wherein, The secondary battery satisfies at least one of the following conditions: (1)20≤W1≤70； (2)0.5≤D≤5。 5. The secondary battery according to any one of claims 1 to 4, wherein, The electrolyte further includes a first component, and the first component includes at least one of fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate or ethylene vinylene carbonate; Based on the mass of the electrolyte, the mass percentage content of the first component is W2%, 0.5 ≤ W2 ≤ 15, preferably, 1 ≤ W2 ≤ 8.

6. The secondary battery according to any one of claims 1 to 4, wherein, The average diameter of the carbon nanotubes is d nm, 3 ≤ d ≤ 40, preferably, 5 ≤ d ≤ 20.

7. The secondary battery according to any one of claims 1 to 4, wherein, The average length of the carbon nanotube clusters is L μm, 3 ≤ L ≤ 40, preferably, 5 ≤ L ≤ 30.

8. The secondary battery according to any one of claims 1 to 4, wherein, The negative electrode material layer satisfies at least one of the following: (1) The silicon-based particles include at least one of pure silicon, a silicon alloy, a silicon-carbon composite material or a silicon-oxygen composite material; (2) The carbon nanotubes include multi-walled carbon nanotubes.

9. The secondary battery according to any one of claims 1 to 4, wherein, Based on the mass of the negative electrode material layer, the mass percentage content of the carbon nanotube clusters is 0.1% to 2%.

10. An electronic device, which includes the secondary battery according to any one of claims 1 to 9.

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