Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device. The secondary battery comprises a negative electrode, a positive electrode and an electrolyte, the negative electrode comprises a negative electrode current collector and a negative electrode mixture layer arranged on at least one surface of the negative electrode current collector, the thickness of the negative electrode mixture layer is T [mu] m, the negative electrode mixture layer contains carbon nanotubes and silicon-based particles, the average particle diameter of the silicon-based particles is D [mu] m, and 3.7 < = 10 T / D2 < = 24.9; the electrolyte comprises a dinitrile compound and a trinitrile compound. According to the secondary battery provided by the invention, relatively high energy density is realized, and meanwhile, the high-temperature intermittent cycle resistance growth rate and the fast charge cycle resistance growth rate are both improved.

Description

[0001] This application is a divisional application of the patent application filed on May 10, 2024, with application number 202410574921.2 and title "Secondary Battery and Electronic Device". Technical Field

[0002] This application belongs to the field of energy storage technology, specifically relating to a secondary battery and electronic device. Background Technology

[0003] To meet the requirements of sustainable development, secondary batteries offer a clean energy storage and utilization solution. With the continuous development of application scenarios, the performance requirements for secondary batteries are also constantly increasing, especially the demand for energy density. Since the theoretical capacity of silicon is approximately ten times that of graphite, replacing all or part of graphite with silicon can significantly improve the energy density of secondary batteries. However, during the use of secondary batteries, silicon undergoes significant contraction and expansion due to the insertion and extraction of metal ions, resulting in a significant deterioration in the cycle performance of the secondary battery. Therefore, it is necessary to develop a silicon-containing secondary battery that achieves high energy density while also considering good cycle performance. Summary of the Invention

[0004] The purpose of this application is to provide a secondary battery and electronic device that achieves high energy density while improving the growth rate of resistance during high-temperature intermittent cycling and fast-charging cycling.

[0005] In a first aspect, this application provides a secondary battery, comprising a negative electrode, a positive electrode, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode additive layer disposed on at least one surface of the negative electrode current collector. The negative electrode additive layer contains carbon nanotubes and silicon-based particles. The thickness of the negative electrode additive layer is T μm, and the average particle size of the silicon-based particles is D μm, 3.7 ≤ 10T / D. 2 ≤24.9; the electrolyte includes dinitrile compounds and trinitrile compounds. The secondary battery provided in this application achieves high energy density while also improving the growth rate of resistance during high-temperature intermittent cycling and fast-charge cycling.

[0006] The inventors discovered that the resistivity of secondary batteries containing silicon-based particles increases significantly after undergoing high-temperature intermittent cycling and fast-charge cycling. By configuring the secondary battery as described above, it is possible to achieve high energy density while simultaneously improving the resistance growth rate during both high-temperature intermittent cycling and fast-charge cycling. The inventors hypothesize that during high-temperature intermittent cycling and fast-charge cycling, the volume of silicon-based particles undergoes significant expansion and contraction. Carbon nanotubes are displaced as the silicon-based particles expand, and this displacement cannot be fully recovered as the silicon-based particles contract, causing a break in the conductive network within the negative electrode binder layer, resulting in increased resistivity. The thickness Tμm of the negative electrode binder layer and the average particle size Dμm of the silicon-based particles jointly influence the distribution and displacement space of carbon nanotubes within the negative electrode binder layer; the cyano groups in the dinitrile and trinitrile compounds possess relatively small steric hindrance and strong nucleophilic properties. When cyano-containing dinitrile and trinitrile compounds participate in the formation of the solid electrolyte interphase (SEI) film on the surface of silicon-based particles, the resulting SEI film possesses a unique adsorption force for carbon nanotubes, reducing the possibility of circuit breakage in the conductive network inside the negative electrode due to volume changes in the silicon-based particles. By controlling the thickness Tμm of the negative electrode binder layer and the average particle size Dμm of the silicon-based particles, the following condition can be met: 3.7 ≤ 10T / D 2 With a strength of ≤24.9, and by including dinitrile and trinitrile compounds in the electrolyte, the secondary battery can achieve high energy density while also improving the growth rate of resistance during high-temperature intermittent cycling and fast-charging cycling.

[0007] In some embodiments, the dinitrile compound includes at least one of malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxopropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, the trinitrile compound includes at least one of 1,3,6-hexanetrionitrile, 1,3,5-pentanetrimethylonitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane. By adjusting the dinitrile compound to include at least one of the above-mentioned substances and / or the trinitrile compound to include at least one of the above-mentioned substances, the high-temperature intermittent cycle resistance growth rate and the fast-charge cycle resistance growth rate of the secondary battery can be improved.

[0008] In some embodiments, the dinitrile compound includes at least two of malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxopropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, the trinitrile compound includes at least two of 1,3,6-hexanetrionitrile, 1,3,5-pentanetrimethylonitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane. By adjusting the dinitrile compound to include at least two of the above-mentioned substances and / or the trinitrile compound to include at least two of the above-mentioned substances, the high-temperature intermittent cycle resistance growth rate and the fast-charge cycle resistance growth rate of the secondary battery can be further improved.

[0009] In some embodiments, based on the mass of the electrolyte, the mass percentage of the dinitrile compound is N1%, the mass percentage of the trinitrile compound is N2%, and 1.1 ≤ N1 / N2 ≤ 4.9. By adjusting the value of N1 / N2 within the above range, the possibility of open circuits in the conductive network inside the negative electrode due to volume changes of silicon-based particles can be reduced, improving the rate of increase in high-temperature intermittent cycle resistance and the rate of increase in fast-charge cycle resistance of the secondary battery. Optionally, 2.2 ≤ N1 / N2 ≤ 3.7.

[0010] In some embodiments, based on the mass of the electrolyte, the electrolyte satisfies at least one of the following: (1) 7.0 ≤ 10 T / D 2 (1) ≤18.1; (2) 60≤T≤122; (3) 7.0≤D≤12.7; (4) 3.2≤N1≤6.8; (5) 1.4≤N2≤2.9. By ensuring that the electrolyte meets at least one of the above conditions, the growth rate of the high-temperature intermittent cycle resistance and the growth rate of the fast-charge cycle resistance of the secondary battery can be improved. Optionally, the electrolyte meets at least one of the following conditions: 78.2≤T≤113.0; 7.6≤D≤10.6; 4.2≤N1≤5.9; 1.6≤N2≤2.5.

[0011] In some embodiments, based on the mass of the electrolyte, the electrolyte satisfies at least one of the following: (1) the electrolyte includes succinate and adiponitrile, with the mass percentage of succinate being A1% and the mass percentage of adiponitrile being A2%, and 1.27 ≤ A1 / A2 ≤ 3.36; (2) the electrolyte includes 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile, with the mass percentage of 1,2-bis(2-cyanoethoxy)ethane being B1% and the mass percentage of 1,3,6-hexanetrionitrile being B2%, and 0.83 ≤ B1 / B2 ≤ 2.43. By ensuring that the electrolyte satisfies at least one of the above, the possibility of open circuits in the conductive network inside the negative electrode due to volume changes of silicon-based particles can be reduced, thereby improving the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery. Optionally, the electrolyte satisfies at least one of the following: 1.84≤A1 / A2≤2.91; 1.36≤B1 / B2≤2.00.

[0012] In some embodiments, the electrolyte satisfies at least one of the following: (1) 2.8 ≤ A1 ≤ 3.7; (2) 1.1 ≤ A2 ≤ 2.2; (3) 1.0 ≤ B1 ≤ 1.7; (4) 0.7 ≤ B2 ≤ 1.2. Adjusting the mass percentages of succinic acid, adiponitrile, 1,2-bis(2-cyanoethoxy)ethane, and / or 1,3,6-hexanetrionitrile in the electrolyte to satisfy the above ranges can further improve the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0013] In some embodiments, the electrolyte comprises ethylene carbonate and propylene carbonate, wherein the mass percentage of ethylene carbonate is X1% and the mass percentage of propylene carbonate is X2% based on the mass of the electrolyte, and the electrolyte satisfies at least one of the following: (1) 29 ≤ X1 + X2 ≤ 51; (2) 1.1 ≤ X2 / X1 ≤ 2.5. By ensuring that the electrolyte satisfies at least one of the above, the growth rate of high-temperature intermittent cycle resistance and the growth rate of fast-charge cycle resistance of the secondary battery can be improved. Optionally, the electrolyte satisfies at least one of the following: 34 ≤ X1 + X2 ≤ 46; 1.6 ≤ X2 / X1 ≤ 2.2.

[0014] In some embodiments, the electrolyte comprises ethyl propionate and propyl propionate, wherein the mass percentage of ethyl propionate is Y1% and the mass percentage of propyl propionate is Y2% based on the mass of the electrolyte, and the electrolyte satisfies at least one of the following: (1) 35 ≤ Y1 + Y2 ≤ 62; (2) 1.2 ≤ Y2 / Y1 ≤ 2.9. By satisfying at least one of the above conditions, the growth rate of high-temperature intermittent cycle resistance and the growth rate of fast-charge cycle resistance of the secondary battery can be improved. Optionally, the electrolyte satisfies at least one of the following: 41 ≤ Y1 + Y2 ≤ 55; 1.5 ≤ Y2 / Y1 ≤ 2.5.

[0015] In some embodiments, the electrolyte includes a fluorinated compound, which includes at least one of fluorobenzene or fluoroethylene carbonate. Based on the mass of the electrolyte, the electrolyte satisfies at least one of the following: (1) the mass percentage of fluorobenzene is F1%, 0.9 ≤ F1 ≤ 4.1; (2) the mass percentage of fluoroethylene carbonate is F2%, 10.5 ≤ F2 ≤ 19.5. By ensuring that the electrolyte satisfies at least one of the above, the ability of the generated solid electrolyte interface film to adsorb carbon nanotubes can be enhanced, thereby improving the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charging cycling of the secondary battery. Optionally, the electrolyte satisfies at least one of the following: 2.7 ≤ F1 ≤ 3.4; 12.5 ≤ F2 ≤ 17.5.

[0016] In some embodiments, the electrolyte includes a compound of Formula I, wherein the mass percentage of the compound of Formula I is H%, and 0.2 ≤ H ≤ 0.9% based on the mass of the electrolyte. By including the compound of Formula I in the electrolyte and adjusting the value of H within the above range, the elasticity of the solid electrolyte interfacial membrane and its ability to adsorb carbon nanotubes can be improved, further enhancing the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charging cycling.

[0017] The chemical formula of compound I is:

[0018] In some embodiments, the electrolyte includes a compound of formula II, wherein the mass percentage of compound II is G%, 0.2 ≤ G ≤ 0.7%, based on the mass of the electrolyte. By adjusting the value of G within the above range, the elasticity of the solid electrolyte interfacial membrane and its ability to adsorb carbon nanotubes can be improved, further enhancing the growth rate of resistance during high-temperature intermittent cycling and the growth rate of resistance during fast-charging cycling.

[0019] The chemical formula of compound II is:

[0020] In some embodiments, the silicon-based particles include a carbon skeleton and a protective layer located on at least a portion of the surface of the carbon skeleton. The material of the protective layer includes amorphous carbon, and the material of the carbon skeleton includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, or hard carbon.

[0021] A second aspect of this application provides an electronic device that includes the secondary battery provided in the first aspect of this application. The electronic device provided in the second aspect achieves higher energy density while simultaneously improving the growth rate of resistance during high-temperature intermittent cycling and fast-charging cycling.

[0022] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Detailed Implementation

[0023] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0024] Unless otherwise expressly stated, the terms used in this application shall have the meanings indicated below.

[0025] In a first aspect, this application provides a secondary battery, comprising a negative electrode, a positive electrode, and an electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode additive layer disposed on at least one surface of the negative electrode current collector. The negative electrode additive layer contains carbon nanotubes and silicon-based particles. The thickness of the negative electrode additive layer is T μm, and the average particle size of the silicon-based particles is D μm, 3.7 ≤ 10T / D. 2 ≤24.9; the electrolyte includes dinitrile compounds and trinitrile compounds. The secondary battery provided in this application achieves high energy density while also improving the growth rate of resistance during high-temperature intermittent cycling and fast-charge cycling.

[0026] negative electrode

[0027] The negative electrode includes a negative electrode current collector and a negative electrode additive layer disposed on at least one surface of the negative electrode current collector, the negative electrode additive layer containing a negative electrode active material. In some embodiments, the rechargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.

[0028] In some embodiments, the thickness of the negative electrode mixture layer is T μm, and the negative electrode active material includes silicon-based particles with an average particle size of D μm, 3.7 ≤ 10T / D. 2 ≤24.9. In some embodiments, 7.0 ≤10T / D 2 ≤24.9. In some embodiments, 3.7 ≤ 10 T / D 2 ≤18.1. In some embodiments, 7.0 ≤ 10 T / D 2 ≤18.1. In some embodiments, 7.4 ≤10T / D 2 ≤18.1. In some embodiments, 7.0 ≤ 10 T / D 2 ≤11.7. In some embodiments, 7.4 ≤10T / D 2 ≤11.7. In some embodiments, 3.7 ≤ 10 T / D 2 ≤7.0. In some embodiments, 7.0 ≤ 10 T / D 2 ≤7.4. In some embodiments, 11.7 ≤ 10 T / D 2 ≤18.1. In some embodiments, 18.1 ≤ 10 T / D 2 ≤24.9. In some embodiments, 10T / D 2The values ​​are 3.7, 4.9, 6.6, 6.7, 7.0, 7.38, 7.6, 8.9, 10.5, 11.66, 13.0, 14.5, 15.2, 17.3, 18.1, 18.8, 19.7, 21.0, 22.3, 23.5, 24.9, or any combination of these values. This application regulates the thickness Tμm of the negative electrode binder layer and the average particle size Dμm of the silicon-based particles to satisfy the above relationship. This optimizes the distribution and displacement space of carbon nanotubes within the negative electrode binder layer, helping to reduce the possibility of circuit breakage in the conductive network inside the negative electrode due to volume changes in the silicon-based particles. Thus, while achieving higher energy density, it also improves the growth rate of resistance during high-temperature intermittent cycling and fast-charging cycling.

[0029] In some embodiments, 60 ≤ T ≤ 122. In some embodiments, 78.2 ≤ T ≤ 122. In some embodiments, 60 ≤ T ≤ 113.0. In some embodiments, 78.2 ≤ T ≤ 113.0. In some embodiments, 60 ≤ T ≤ 78.2. In some embodiments, 113.0 ≤ T ≤ 122. In some embodiments, T is a value within the range of 60, 62.2, 69.4, 70.7, 78.2, 80.1, 81.7, 82.9, 83.9, 89.8, 94.2, 98.7, 100.3, 103.2, 108.3, 112.2, 112.9, 114.9, 119.5, 122, or any two of these values. Adjusting the thickness of the negative electrode binder layer within the above range can improve the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0030] In some embodiments, 7.0 ≤ D ≤ 12.7. In some embodiments, 7.0 ≤ D ≤ 10.6. In some embodiments, 7.6 ≤ D ≤ 12.7. In some embodiments, 7.6 ≤ D ≤ 10.6. In some embodiments, 7.0 ≤ D ≤ 7.6. In some embodiments, 10.6 ≤ D ≤ 12.7. In some embodiments, D is a value within the range of 7, 7.4, 7.6, 7.7, 7.9, 8.0, 8.5, 9.0, 9.2, 9.6, 10.0, 10.1, 10.6, 10.7, 10.8, 10.9, 11.2, 11.7, 12.0, 12.3, 12.7, or any combination of these values. Adjusting the average particle size of the silicon-based particles within the above range can improve the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0031] In some embodiments, silicon-based particles include silicon-based materials, silicon-carbon materials (composite of silicon-based materials and carbon materials), or silicon oxide (SiO2). x At least one of the following: (0 < x ≤ 2).

[0032] In some embodiments, the silicon-based material may be silicon particles, silicon alloy particles, etc.

[0033] For example, the silicon-based and carbon-based composite material can be an active material obtained by dispersing silicon nanoparticles with an average particle size of 200 nm or less on carbon-based particles, and then coating them with carbon, an active material in which silicon (Si) particles are present on and inside graphite, etc. The average particle size of the secondary particles of the silicon-based and carbon-based composite material can be from 5 μm to 20 μm. In this application, the secondary particles of the silicon-based and carbon-based composite material refer to silicon-based particles and / or carbon-based particles, such as silicon nanoparticles, in the composite material. The average particle size of the silicon nanoparticles can be 5 nm or more, for example, 10 nm or more, for example, 20 nm or more, for example, 50 nm or more, for example, 70 nm or more. The average particle size of the silicon nanoparticles can be 200 nm or less, 150 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, or 10 nm or less. For example, the average particle size of the silicon nanoparticles can be from 100 nm to 150 nm. The average particle size of the secondary particles of the silicon-based and carbon-based composite material can be from 5 μm to 20 μm, for example, from 7 μm to 15 μm, for example, from 10 μm to 13 μm.

[0034] In some preferred embodiments, the silicon-based particles include a carbon skeleton and a protective layer located on at least a portion of the surface of the carbon skeleton. The material of the protective layer includes amorphous carbon, and the material of the carbon skeleton includes at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, or hard carbon.

[0035] Optionally, the negative electrode active material may further include amorphous carbon materials, which may be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, or calcined coke, etc.

[0036] This application does not impose any particular limitation on the type of negative electrode conductive agent, as long as it can achieve the purpose of this application. For example, the negative electrode conductive agent can be at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots, or graphene, etc. The aforementioned carbon nanotubes can include, but are not limited to, at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0037] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application. For example, the negative electrode current collector may comprise copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal. The conductive metal includes, but is not limited to, copper, nickel, or titanium, and the polymer substrate material includes, but is not limited to, at least one of polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene terephthalate, polyethylene terephthalate, or poly(p-phenylene terephthalate). In this application, there are no particular limitations on the thickness of the negative electrode current collector and the negative electrode binder layer, as long as they achieve the purpose of this application. 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 binder layer is 30 μm to 160 μm. In this application, the negative electrode binder layer may be disposed on one surface or on two surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or only a part of it. This application has no particular restrictions, as long as the purpose of this application can be achieved.

[0038] The negative electrode active material layer may also include a negative electrode binder. The negative electrode binder improves the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. There are no particular limitations on the type of negative electrode binder, as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of resin binders include, but are not limited to, fluoropolymers, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, etc. When a negative electrode slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, hydroxyethyl carboxymethyl cellulose (HECMC) or its salts, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0039] For example, the negative electrode can be prepared by coating a negative electrode slurry containing a negative electrode binder, silicon-carbon composite particles, conductive agent, etc. onto a negative electrode current collector, drying it, and then calendering it to form a negative electrode slurry layer on both sides of the negative electrode current collector, thereby obtaining the negative electrode.

[0040] This application does not impose any particular limitation on the compaction density of the negative electrode sheet, as long as it achieves the purpose of this application. For example, the compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 Up to 1.85 g / cm 3 This application does not impose any particular limitation on the cold pressing pressure of the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the cold pressing pressure of the negative electrode sheet can be from 3 tons to 30 tons.

[0041] electrolyte

[0042] The electrolyte used in the secondary battery of this application includes an electrolyte and a solvent for dissolving the electrolyte. In some embodiments, the electrolyte of this application includes a dinitrile compound and a trinitrile compound. The cyano group in the dinitrile compound and trinitrile compound has small reaction steric hindrance and large nucleophilic properties. When the dinitrile compound and trinitrile compound containing cyano groups participate in the formation process of the solid electrolyte interface film on the surface of silicon-based particles, the formed solid electrolyte interface film has a special adsorption force for adsorbing carbon nanotubes, thus improving the high-temperature intermittent cycle resistance growth rate and the fast-charge cycle resistance growth rate of the secondary battery.

[0043] In some embodiments, the dinitrile compound includes at least one of malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxopropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, the trinitrile compound includes at least one of 1,3,6-hexanetrionitrile, 1,3,5-pentanetrimethylonitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane. By adjusting the dinitrile compound and / or the trinitrile compound to include the above-mentioned substances, the quality of the SEI film can be improved, and the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery can be improved.

[0044] In some embodiments, the dinitrile compound includes at least two of malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxopropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, the trinitrile compound includes at least two of 1,3,6-hexanetrionitrile, 1,3,5-pentanetrimethylonitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane. By adjusting the dinitrile compound and / or the trinitrile compound to include at least two of the above-mentioned substances, better compatibility with the negative electrode can be achieved, further improving the high-temperature intermittent cycle resistance growth rate and the fast-charge cycle resistance growth rate of the secondary battery.

[0045] In some embodiments, the mass percentage of the dinitrile compound is N1%, the mass percentage of the trinitrile compound is N2%, and 1.1 ≤ N1 / N2 ≤ 4.9. In some embodiments, 2.2 ≤ N1 / N2 ≤ 4.9. In some embodiments, 1.1 ≤ N1 / N2 ≤ 3.7. In some embodiments, 2.2 ≤ N1 / N2 ≤ 3.7. In some embodiments, 2.2 ≤ N1 / N2 ≤ 3.3. In some embodiments, 1.1 ≤ N1 / N2 ≤ 2.2. In some embodiments, 3.3 ≤ N1 / N2 ≤ 3.7. In some embodiments, 3.7 ≤ N1 / N2 ≤ 4.9. In some embodiments, the value of N1 / N2 is 1.1, 1.4, 1.6, 1.7, 1.8, 2.0, 2.2, 2.4, 2.9, 3.1, 3.3, 3.5, 3.7, 3.8, 4.3, 4.5, 4.7, 4.9, or a value within a range of any two of these values. By adjusting the values ​​of N1 / N2 within the above range, this application can further reduce the possibility of the conductive network inside the negative electrode being broken due to the volume change of silicon-based particles, thereby significantly improving the growth rate of high-temperature intermittent cycle resistance and fast-charging cycle resistance of the secondary battery.

[0046] In some embodiments, 3.2 ≤ N1 ≤ 6.8. In some embodiments, 4.9 ≤ N1 ≤ 6.8. In some embodiments, 3.2 ≤ N1 ≤ 4.9. In some embodiments, 4.9 ≤ N1 ≤ 5.9. In some embodiments, 3.2 ≤ N1 ≤ 4.9. In some embodiments, 5.9 ≤ N1 ≤ 6.8. In some embodiments, the value of N1 is 3.2, 3.4, 3.7, 3.9, 4.1, 4.2, 4.5, 4.7, 4.9, 5.1, 5.2, 5.3, 5.5, 5.6, 5.8, 5.9, 6.2, 6.5, 6.6, 6.8, or a value within any two of these ranges. Controlling the mass percentage of dinitrile compounds in the electrolyte within the above range is beneficial for further improving the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0047] In some embodiments, 1.4 ≤ N2 ≤ 2.9. In some embodiments, 1.4 ≤ N2 ≤ 2.2. In some embodiments, 1.6 ≤ N2 ≤ 2.9. In some embodiments, 1.6 ≤ N2 ≤ 2.2. In some embodiments, 1.4 ≤ N2 ≤ 1.6. In some embodiments, 2.2 ≤ N2 ≤ 2.9. In some embodiments, the value of N2 is 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or a value within any two of these ranges. Controlling the mass percentage of trinitrile compounds in the electrolyte within the above range is beneficial for further improving the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0048] In some embodiments, the electrolyte comprises succinic acid and adiponitrile, wherein the mass percentage of succinic acid is A1% and the mass percentage of adiponitrile is A2% based on the mass of the electrolyte, and 1.27 ≤ A1 / A2 ≤ 3.36. In some embodiments, 1.84 ≤ A1 / A2 ≤ 3.36. In some embodiments, 1.27 ≤ A1 / A2 ≤ 2.91. In some embodiments, 1.84 ≤ A1 / A2 ≤ 2.91. In some embodiments, 1.27 ≤ A1 / A2 ≤ 1.84. In some embodiments, 2.91 ≤ A1 / A2 ≤ 3.36. In some embodiments, the value of A1 / A2 is 1.27, 1.33, 1.52, 1.66, 1.78, 2.06, 2.18, 2.35, 2.55, 2.70, 2.77, 3.01, 3.12, 3.26, 3.36, or a value within a range of any two of these values. Adjusting the mass percentage of succinic acid and adiponitrile in the electrolyte to satisfy the above relationship can improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of secondary batteries.

[0049] In some embodiments, 2.8 ≤ A1 ≤ 3.7; 1.1 ≤ A2 ≤ 2.2. In some embodiments, 2.8 ≤ A1 ≤ 3.2. In some embodiments, 2.8 ≤ A1 ≤ 3.5. In some embodiments, 3.2 ≤ A1 ≤ 3.5. In some embodiments, 3.2 ≤ A1 ≤ 3.7. In some embodiments, 3.5 ≤ A1 ≤ 3.7. In some embodiments, 1.1 ≤ A2 ≤ 1.7. In some embodiments, 1.1 ≤ A2 ≤ 1.9. In some embodiments, 1.7 ≤ A2 ≤ 2.2. In some embodiments, 1.7 ≤ A2 ≤ 1.9. In some embodiments, 1.9 ≤ A2 ≤ 2.2. In some embodiments, A1 is a value within the range of 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, or any two of these values. In some embodiments, A2 is a value within the range of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, or any combination thereof. Adjusting the succinic acid and / or adiponitrile in the electrolyte to meet the above ranges can further improve the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charge cycling of the secondary battery.

[0050] In some embodiments, the electrolyte comprises 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile, wherein, based on the mass of the electrolyte, the mass percentage of 1,2-bis(2-cyanoethoxy)ethane is B1%, the mass percentage of 1,3,6-hexanetrionitrile is B2%, and 0.83 ≤ B1 / B2 ≤ 2.43. In some embodiments, 0.83 ≤ B1 / B2 ≤ 2.00. In some embodiments, 1.36 ≤ B1 / B2 ≤ 2.43. In some embodiments, 1.36 ≤ B1 / B2 ≤ 2.00. In some embodiments, 0.83 ≤ B1 / B2 ≤ 1.36. In some embodiments, 1.36 ≤ B1 / B2 ≤ 2.43. In some embodiments, the value of B1 / B2 is 0.83, 0.91, 1.00, 1.12, 1.32, 1.33, 1.36, 1.55, 1.66, 1.77, 1.82, 2.00, 2.13, 2.19, 2.33, 2.43, or a range of any two of these values. Adjusting the mass percentage of 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile in the electrolyte to satisfy the above relationship can improve the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charge cycling of the secondary battery.

[0051] In some embodiments, 1.0 ≤ B1 ≤ 1.7; 0.7 ≤ B2 ≤ 1.2. In some embodiments, 1.0 ≤ B1 ≤ 1.5. In some embodiments, 1.5 ≤ B1 ≤ 1.7. In some embodiments, 0.7 ≤ B2 ≤ 0.8. In some embodiments, 0.8 ≤ B2 ≤ 1.1. In some embodiments, 1.1 ≤ B2 ≤ 1.2. In some embodiments, 0.7 ≤ B2 ≤ 1.1. In some embodiments, 0.8 ≤ B2 ≤ 1.2. In some embodiments, B1 is a value within the range of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or any two of these values. In some embodiments, B2 is a value within the range of 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, or any two of these values. Adjusting the 1,2-bis(2-cyanoethoxy)ethane and / or 1,3,6-hexanetrionitrile in the electrolyte to meet the above-mentioned ranges can further improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of secondary batteries.

[0052] In some embodiments, the electrolyte comprises ethylene carbonate and propylene carbonate, wherein the mass percentage of ethylene carbonate is X1% and the mass percentage of propylene carbonate is X2% based on the mass of the electrolyte, and 29 ≤ X1 + X2 ≤ 51. In some embodiments, 34 ≤ X1 + X2 ≤ 51. In some embodiments, 29 ≤ X1 + X2 ≤ 46. In some embodiments, 34 ≤ X1 + X2 ≤ 46. In some embodiments, 29 ≤ X1 + X2 ≤ 34. In some embodiments, 46 ≤ X1 + X2 ≤ 51. In some embodiments, the value of X1 + X2 is 29, 30, 32, 33, 35, 36, 38, 39, 41, 43, 45, 47, 49, 50, 51, or a value within the range of any two of these values. This application regulates the sum of the mass contents of ethylene carbonate and propylene carbonate in the electrolyte within the above ranges, thereby improving the rate of increase in resistance during high-temperature intermittent cycles and the rate of increase in resistance during fast-charge cycles of the secondary battery.

[0053] In some embodiments, 1.1 ≤ X2 / X1 ≤ 2.5. In some embodiments, 1.6 ≤ X2 / X1 ≤ 2.5. In some embodiments, 1.1 ≤ X2 / X1 ≤ 2.2. In some embodiments, 1.6 ≤ X2 / X1 ≤ 2.2. In some embodiments, 1.1 ≤ X2 / X1 ≤ 1.6. In some embodiments, 2.2 ≤ X2 / X1 ≤ 2.5. In some embodiments, the value of X2 / X1 is 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or a value within a range of any two of these values. By adjusting the mass content of ethylene carbonate and propylene carbonate in the electrolyte to satisfy the above relationship, the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery can be further improved.

[0054] In some embodiments, the electrolyte comprises ethyl propionate and propyl propionate, wherein the mass percentage of ethyl propionate is Y1% and the mass percentage of propyl propionate is Y2% based on the mass of the electrolyte, and 35 ≤ Y1 + Y2 ≤ 62. In some embodiments, 41 ≤ Y1 + Y2 ≤ 62. In some embodiments, 35 ≤ Y1 + Y2 ≤ 55. In some embodiments, 41 ≤ Y1 + Y2 ≤ 55. In some embodiments, 35 ≤ Y1 + Y2 ≤ 41. In some embodiments, 55 ≤ Y1 + Y2 ≤ 62. In some embodiments, the value of Y1 + Y2 is 35, 36, 39, 40, 41, 43, 44, 47, 48, 50, 52, 55, 56, 59, 61, 62, or a value within the range of any two of these values. This application regulates the sum of the mass contents of ethyl propionate and propyl propionate in the electrolyte within the above range, thereby improving the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery.

[0055] In some embodiments, 1.2 ≤ Y2 / Y1 ≤ 2.9. In some embodiments, 1.2 ≤ Y2 / Y1 ≤ 2.5. In some embodiments, 1.5 ≤ Y2 / Y1 ≤ 2.9. In some embodiments, 1.5 ≤ Y2 / Y1 ≤ 2.5. In some embodiments, 1.2 ≤ Y2 / Y1 ≤ 1.5. In some embodiments, 2.5 ≤ Y2 / Y1 ≤ 2.9. In some embodiments, the value of Y2 / Y1 is 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.9, 2.1, 2.2, 2.3, 2.4, 2.5, 2.7, 2.8, 2.9, or a value within a range of any two of these values. By adjusting the mass content of ethyl propionate and propyl propionate in the electrolyte to satisfy the above relationship, the high-temperature intermittent cycle resistance growth rate and fast-charge cycle resistance growth rate of the secondary battery can be further improved.

[0056] In some embodiments, the electrolyte comprises a fluorinated compound, which includes at least one of fluorobenzene or fluoroethylene carbonate. Based on the mass of the electrolyte, the mass percentage of fluorobenzene is F1%, where 0.9 ≤ F1 ≤ 4.1. In some embodiments, 0.9 ≤ F1 ≤ 3.4. In some embodiments, 2.7 ≤ F1 ≤ 4.1. In some embodiments, 2.7 ≤ F1 ≤ 3.4. In some embodiments, 0.9 ≤ F1 ≤ 2.7. In some embodiments, 3.4 ≤ F1 ≤ 4.1. In some embodiments, F1 is a value within the range of 0.9, 1.0, 1.2, 1.6, 1.8, 1.9, 2.3, 2.6, 2.7, 2.9, 3.0, 3.2, 3.4, 3.6, 3.9, 4.1, or any combination of these values. Regulating the mass percentage of fluorobenzene in the electrolyte within the above range can enhance the ability of the generated solid electrolyte interface film to adsorb carbon nanotubes, improving the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charging cycling of the secondary battery.

[0057] In some embodiments, the mass percentage of fluoroethylene carbonate is F2% based on the mass of the electrolyte, with 10.5 ≤ F2 ≤ 19.5%. In some embodiments, 12.5 ≤ F2 ≤ 19.5%. In some embodiments, 10.5 ≤ F2 ≤ 17.5%. In some embodiments, 12.5 ≤ F2 ≤ 17.5%. In some embodiments, 10.5 ≤ F2 ≤ 12.5%. In some embodiments, 12.5 ≤ F2 ≤ 17.5. In some embodiments, 17.5 ≤ F2 ≤ 19.5. In some embodiments, F2 is a value within the range of 10.5, 10.9, 11.3, 12.5, 13.2, 13.7, 14.1, 14.7, 15.6, 16.6, 16.8, 17.5, 17.8, 18.3, 19.2, 19.5, or any two of these values. By controlling the mass percentage of fluoroethylene carbonate in the electrolyte within the above range, the ability of the generated solid electrolyte interface film to adsorb carbon nanotubes can be enhanced, thereby improving the growth rate of high-temperature intermittent cycle resistance and fast-charging cycle resistance of the secondary battery.

[0058] In some embodiments, the electrolyte comprises a compound of Formula I, wherein the mass percentage of the compound of Formula I is H%, and 0.2 ≤ H ≤ 0.9% based on the mass of the electrolyte. In some embodiments, 0.2 ≤ H ≤ 0.5. In some embodiments, 0.5 ≤ H ≤ 0.9. In some embodiments, H is a value within the range of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or any two of these values. Adding a compound of Formula I to the electrolyte and controlling the mass percentage within the above range can further improve the high-temperature intermittent cycling resistance growth rate and the fast-charge cycling resistance growth rate.

[0059] In this application, the chemical formula of compound I is:

[0060] In some embodiments, the electrolyte comprises a compound of formula II, wherein the mass percentage of compound II is G% based on the mass of the electrolyte, and 0.2 ≤ G ≤ 0.7. In some embodiments, 0.2 ≤ G ≤ 0.4. In some embodiments, 0.4 ≤ G ≤ 0.7. In some embodiments, G is a value within the range of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or any two of these values. Adding a compound of formula II to the electrolyte and controlling the mass percentage within the above range can further improve the rate of increase in resistance during high-temperature intermittent cycling and the rate of increase in resistance during fast-charging cycling.

[0061] The chemical formula of compound II is:

[0062] The electrolyte may also include lithium salts and organic solvents. This application does not particularly limit the type of lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalateborate)borate (LiBOB), or lithium difluorooxalateborate (LiDFOB). Based on the mass of the electrolyte, the mass percentage of lithium salt may be from 8% to 15%, for example, the mass percentage of lithium salt may be 8%, 9%, 10%, 11%, 12.5%, 13%, 15%, or a range consisting of any two of these values. This application does not particularly limit the type of organic solvents mentioned above, as long as they achieve the purpose of this application. For example, they may include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The carbonate compounds mentioned above may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate. The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene ethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of ethylene glycol dimethyl ether, 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 other organic solvents mentioned above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0063] positive electrode

[0064] The positive electrode includes a positive electrode current collector and a positive electrode additive layer disposed on the surface of the positive electrode current collector.

[0065] The positive electrode mixture layer contains positive electrode active material, and the positive electrode mixture layer can be one or more layers. Each layer in a multilayer positive electrode active material can contain the same or different positive electrode active materials. The positive electrode active material is any substance capable of reversibly inserting and deintercalating alkali metal ions.

[0066] In some embodiments, the positive electrode active material comprises a lithium transition metal oxide containing nickel and other transition metals. In the lithium transition metal oxide comprising 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 moles of the transition metals.

[0067] For example, lithium transition metal oxides can be compounds represented by the following formula α:

[0068] Formula α: Li a Ni x Co y M z O 2-b A b ,

[0069] In formula α, 0.9≤a≤1.2, 0≤b≤0.2, 0.6≤x<1, 0<y≤0.3, 0<z≤0.3, and x+y+z=1, M is at least one selected from manganese (Mn), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al) or boron (B), and A is F, S, Cl, Br or a combination thereof. For example, the above subscripts can be 0.7≤x<1, 0<y≤0.3, and 0<z≤0.3; 0.8≤x<1, 0<y≤0.3, and 0<z≤0.3; 0.8≤x<1, 0<y≤0.2, and 0<z≤0.2; 0.83≤x<0.97, 0<y≤0.15, and 0<z≤0.15; or 0.85≤x<0.95, 0<y≤0.1, and 0<z≤0.1.

[0070] For example, lithium transition metal oxides can be at least one compound represented by the following formula β or formula γ:

[0071] Formula β: LiNi x Co y Mn z O2,

[0072] In equation β, 0.6≤x≤0.95, 0<y≤0.2, and 0<z≤0.1. For example, 0.7≤x≤0.95, 0<y≤0.3, and 0<z≤0.3.

[0073] Formula γ: LiNi x Co y Al z O2,

[0074] In the formula γ, 0.6≤x≤0.95, 0<y≤0.2, and 0<z≤0.1, for example, 0.7≤x≤0.95, 0<y≤0.3, and 0<z≤0.3, for example, 0.8≤x≤0.95, 0<y≤0.3, and 0<z≤0.3, for example, 0.82≤x≤0.95, 0<y≤0.15, and 0<z≤0.15, for example, 0.85≤x≤0.95, 0<y≤0.1, and 0<z≤0.1.

[0075] For example, lithium transition metal oxides can be LiNi. 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2 or LiNi 0.88 Co 0.1 Al 0.02 O2.

[0076] According to another embodiment, the positive electrode active material includes at least one active material selected from the group consisting of: Li-Ni-Co-Al (NCA), Li-Ni-Co-Mn (NCM), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), and lithium iron phosphate (LiFePO4).

[0077] In some embodiments, the positive electrode mixture layer includes a positive electrode conductive material; there is no limitation on the type of positive electrode conductive material, and any known conductive material can be used. Examples of positive electrode conductive materials may include, but are not limited to, acetylene black, Super-P carbon black, etc.; amorphous carbon such as needle coke; carbon nanotubes; graphene, etc. The above-mentioned positive electrode conductive materials can be used alone or in any combination.

[0078] There are no particular restrictions on the type of positive electrode binder used in the manufacture of the positive electrode binder layer. In the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode manufacturing is acceptable. Examples of positive electrode binders 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, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrides, and ethylene-propylene-diene terpolymers (EPDM). The above-mentioned positive electrode adhesives include thermoplastic elastomers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, or their hydrides; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymeric compositions with ion conductivity of alkali metal ions (especially lithium ions). These positive electrode adhesives can be used alone or in any combination.

[0079] There are no restrictions on the type of solvent used to form the positive electrode slurry, 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 used to form the positive electrode slurry can include any of aqueous solvents and organic solvents. Examples of aqueous media can include, but are not limited to, mixtures of alcohol and water or water. Examples of organic media can include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide.

[0080] Thickeners are typically used to adjust the viscosity of slurries. In the case of aqueous media, thickeners and styrene-butadiene rubber (SBR) latex can be used for slurry preparation. There are no particular limitations on the types of thickeners; examples include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts. The above-mentioned thickeners can be used alone or in any combination.

[0081] There are no particular limitations on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metallic material. In some embodiments, the positive electrode current collector is aluminum.

[0082] To reduce the electronic contact resistance between the positive current collector and the positive electrode binder layer, the surface of the positive current collector may include a conductive additive or a conductive coating. Examples of conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver. Examples of conductive coatings may include a mixture layer containing inorganic oxides, conductive agents, and binders.

[0083] The positive electrode can be manufactured by forming a positive electrode mixture layer containing positive electrode active material and binder on the current collector. The manufacture of a positive electrode using positive electrode active material can be carried out by conventional methods, namely, dry mixing the positive electrode active material, binder, and conductive material and thickener as needed, forming a sheet, and pressing the resulting sheet onto the positive electrode current collector; or dissolving or dispersing these materials in a liquid medium to form a slurry, coating the slurry onto the positive electrode current collector and drying it, thereby forming a positive electrode mixture layer on the current collector, thus obtaining the positive electrode.

[0084] Separating membrane

[0085] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0086] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator can be a resin, glass fiber, inorganic material, etc., formed from a material that stabilizes the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of materials for resin or glass fiber separators may include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0087] The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0088] Examples of inorganic materials may include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). Inorganic materials may be in, but are not limited to, particulate or fibrous forms.

[0089] The separator can be in the form of a thin film, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, and microporous membranes. In the thin film form, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separators, the following separators can also be used: separators formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive and / or negative electrodes. For example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0090] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. When the thickness of the separator is within the above ranges, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the secondary battery can be ensured.

[0091] This application also provides an electronic device that includes a secondary battery according to this application.

[0092] The application of the secondary battery in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the secondary battery of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0093] Example

[0094] The following examples, using lithium-ion batteries as an example, provide more specific illustrations of the implementation methods of the secondary battery of this application. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0095] Test methods

[0096] Resistance growth rate after high temperature (65℃) intermittent cycling

[0097] (1) Initial resistance test: After moving the lithium-ion battery to the charge / discharge device at room temperature (25°C), it was charged at a constant current of 0.33C to 4.45V, then charged at a constant voltage of 4.45V to 0.05C to cut off charging, and discharged at 0.33C to 3.0V. After three charge and discharge cycles, the battery was set to SOC 50% based on the discharge capacity of the last cycle. The DC internal resistance (PNE-0506 charge / discharge device) was then measured by the voltage drop displayed when a discharge pulse of 5A (2.5C) was applied for 10 seconds. This resistance was defined as the initial resistance.

[0098] (2) High-temperature intermittent cycling: After measuring the initial resistance, the lithium-ion battery was placed at a high temperature (65°C) and charged to 4.25V with a constant current of 0.5C. Then, it was charged to 0.05C with a constant voltage at 4.25V. The battery thickness was recorded as the initial cycle thickness. After that, it was kept at a constant current of 0.5C to 3.0V. The above charging and discharging process was defined as one high-temperature intermittent cycle, and a total of 80 high-temperature intermittent cycles were performed.

[0099] (3) Resistance after high-temperature intermittent cycling: After the lithium-ion battery was moved into the charge-discharge device at room temperature, the SOC was set to 50%. Then, the resistance after 80 cycles was measured by the voltage drop displayed when a discharge pulse of 5A (2.5C) was applied for 10 seconds using the PNE-0506 charge-discharge device.

[0100] (4) Calculate the rate of increase in resistivity R1 after high-temperature (65℃) intermittent cycling:

[0101] The resistance increase rate R1 (%) after high temperature (65℃) intermittent cycling = {(resistance after 80 cycles - initial resistance) / initial resistance} × 100.

[0102] Fast charging (6C) cycle resistance growth rate

[0103] (1) Initial resistance test: After moving the lithium-ion battery to the charge / discharge device at room temperature (25°C), it was constant-current charged to 4.45V at 0.33C, then charged at a constant voltage of 4.45V to the 0.05C cutoff point, and discharged at 0.33C to 3.0V. After three charge and discharge cycles, the battery was set to SOC 50% based on the discharge capacity of the last cycle. The DC internal resistance (PNE-0506 charge / discharge device) was then measured by the voltage drop displayed when a discharge pulse of 5A (2.5C) was applied for 10 seconds. This resistance was defined as the initial resistance.

[0104] (2) Fast charging cycle: Charge the lithium-ion battery at a constant current of 6C (nominal capacity) to a voltage of 4.25V, then charge it at a constant voltage of 4.25V to a current of 0.05C. After resting for 10 minutes, discharge it at a constant current of 1C to a cutoff voltage of 2.8V. The above charging and discharging process is set as one cycle, and a total of 80 charging and discharging cycles are performed.

[0105] (3) Resistance after fast charging cycle: Set the SOC to 50%. Then, measure the resistance after 80 cycles by using the PNE-0506 charge / discharge device to measure the voltage drop displayed when a discharge pulse of 5A (2.5C) is applied for 10 seconds.

[0106] (4) Calculate the resistance increase rate R2 during fast charging (6C) cycles:

[0107] Fast charging (6C) cycle resistance increase rate R2 (%) = {(resistance after 80 cycles - initial resistance) / initial resistance} × 100.

[0108] Energy density ED

[0109] The lithium-ion batteries of each embodiment and comparative example were placed in a constant temperature chamber at 25℃±1℃ for 30 minutes, charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V to 0.025C, placed in a constant temperature chamber for 5 minutes, and then discharged at 0.5C to 3.0V. The discharge energy E mAh of the lithium-ion battery was recorded, and the length, width, and height of the battery were measured at 50% charge (the lithium-ion battery was charged at a constant current of 0.5C to 3.95V) to obtain the battery volume Vcm. 3 Energy density ED = E / V.

[0110] The average particle size Dμm of silicon-based particles

[0111] The negative electrode sheet was cut into 1cm×1cm dimensions, and then the cut surface of the negative electrode sheet was polished using argon plasma polishing (CP) technology to obtain a CP sample.

[0112] The CP sample was observed using a scanning electron microscope. Silicon-based particles were selected from the CP sample, and their cross-sectional area was calculated and recorded as S. According to S = πR... 2 The formula calculates R. The particle size of silicon-based particles is 2R.

[0113] A total of 20 silicon-based particles were randomly selected. The arithmetic mean of the particle size of the 20 silicon-based particles was calculated and denoted as the average particle size D μm.

[0114] Thickness Tμm of negative electrode compound layer

[0115] The negative electrode sheet was cut into 1cm×1cm dimensions, and then the cut surface of the negative electrode sheet was polished using argon plasma polishing (CP) technology to obtain a CP sample.

[0116] The thickness T μm of the negative electrode mixture layer can be obtained by observing the CP sample with a scanning electron microscope, measuring the thickness of the negative electrode mixture layer on the two surfaces of the current collector, and calculating the arithmetic mean of the two thicknesses.

[0117] Example 1-1

[0118] <Preparation of the negative electrode>

[0119] Preparation of negative electrode sheet:

[0120] Silicon-based particles and artificial graphite were mixed uniformly at a mass ratio of 12:88 to form the negative electrode active material. The above negative electrode active material, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), carbon nanotubes, and carboxymethyl cellulose were mixed at a mass ratio of 95.8:2.4:0.5:0.5:0.8, then deionized water was added and stirred evenly to prepare a negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil, and after drying, a negative electrode sheet with a single-sided negative electrode mixture layer was obtained. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided negative electrode mixture layer. After cold pressing, cutting, slitting, and drying, a negative electrode sheet with a size of 76.6 mm × 875 mm was obtained.

[0121] <Preparation of the positive electrode>

[0122] Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride were mixed in a mass ratio of 95:2:3, and N-methylpyrrolidone was added and stirred until homogeneous to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated onto one surface of an aluminum foil with a thickness of 9 μm, and after drying, a positive electrode sheet with a single-sided coating of positive electrode additive layer was obtained. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode additive layer. After drying, it was cold-pressed, cut, and slit, and then dried again to obtain a positive electrode sheet with a size of 74 mm × 867 mm.

[0123] <Preparation of Electrolyte>

[0124] In a dry argon atmosphere glove box, lithium hexafluorophosphate (LiPF6) was dissolved in a mixed solution containing diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), propyl propionate (PP), dinitrile compounds, trinitrile compounds, and fluoroethylene carbonate (FEC). Based on the mass of the electrolyte, the LiPF6 content was 12%, the contents of other substances are shown in Table 1, and the balance was DEC.

[0125] The dinitrile compounds are succinic anion and adiponitrile, and the ratio of succinic anion to adiponitrile content is 11:10 based on the mass of the electrolyte.

[0126] The trinitrile compound is 1,3,6-hexanetrinitrile.

[0127] <Septum>

[0128] A porous polyethylene film with a thickness of 15 μm (provided by Celgard) was used as the diaphragm.

[0129] <Preparation of Lithium-ion Batteries>

[0130] The positive and negative electrodes, prepared as described above, are connected to the tabs. They are then laminated using a separator to obtain a laminate. The laminate, along with the electrolyte, is then housed within an aluminum laminated casing. The opening of the casing is heat-sealed, and the lithium-ion battery is manufactured through formation, capacity testing, and other steps.

[0131] Except for adjusting the parameters shown in Table 1 and the types of dinitrile and trinitrile compounds described below, all other examples and comparative examples in Table 1 are the same as those in Examples 1-1.

[0132] Examples 1-19 to Examples 1-26

[0133] The dinitrile compound is succinic anion and 1,2-bis(2-cyanoethoxy)ethane, and the ratio of succinic anion to 1,2-bis(2-cyanoethoxy)ethane is 11:10 based on the mass of the electrolyte.

[0134] Examples 1-27 and Examples 1-35

[0135] The dinitrile compound is adiponitrile and 1,2-bis(2-cyanoethoxy)ethane, and the ratio of adiponitrile to 1,2-bis(2-cyanoethoxy)ethane is 11:10 based on the mass of the electrolyte.

[0136] Examples 1-36 and Examples 1-52

[0137] The trinitrile compounds are 1,3,6-hexanetrionitrile and 4-(2-cyanoethyl)heptanedionitrile, and the content ratio of 1,3,6-hexanetrionitrile to 4-(2-cyanoethyl)heptanedionitrile is 11:10 based on the mass of the electrolyte.

[0138] Examples 1-53 and Examples 1-70

[0139] The dinitrile compounds are adiponitrile and 1,2-bis(2-cyanoethoxy)ethane, with a content ratio of adiponitrile to 1,2-bis(2-cyanoethoxy)ethane of 11:10 based on the mass of the electrolyte. The trinitrile compounds are 1,3,6-hexanetrionitrile and 4-(2-cyanoethyl)heptanedionitrile, with a content ratio of 1,3,6-hexanetrionitrile to 4-(2-cyanoethyl)heptanedionitrile of 11:10 based on the mass of the electrolyte.

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] In Table 1, T (μm) represents the thickness of the negative electrode binder layer, and D (μm) represents the average particle size of the silicon-based particles. Based on the mass of the electrolyte, N1 (%) represents the mass percentage of dinitrile compounds, N2 (%) represents the mass percentage of trinitrile compounds, X1 (%) represents the mass percentage of EC, X2 (%) represents the mass percentage of PC, Y1 (%) represents the mass percentage of EP, Y2 (%) represents the mass percentage of PP, F1 (%) represents the mass percentage of fluorobenzene, and F2 (%) represents the mass percentage of FEC.

[0146] As shown in Table 1, the thickness T μm of the negative electrode binder layer and the average particle size D μm of the silicon-based particles in this application satisfy 3.7 ≤ 10T / D 2 The relationship of ≤24.9, combined with dinitrile and trinitrile compounds in the electrolyte, enables the achievement of high energy density while simultaneously improving the growth rate of resistance during high-temperature intermittent cycling and fast-charge cycling. In particular, the regulation of T and D conforms to 7.0 ≤ 10T / D. 2 At ≤18.1, it can further improve the growth rate of high-temperature intermittent cycle resistance and fast-charging cycle resistance of lithium-ion batteries.

[0147] Specifically, when the mass percentages of dinitrile and trinitrile compounds in the electrolyte are controlled to satisfy 1.1 ≤ N1 / N2 ≤ 4.9, they can better match the negative electrode system of this application, further improving the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of the lithium-ion battery. In particular, under the condition of 2.2 ≤ N1 / N2 ≤ 3.7, the growth rates of high-temperature intermittent cycle resistance and fast-charge cycle resistance of the lithium-ion battery can be significantly improved.

[0148] Specifically, adjusting the mass percentages of ethylene carbonate and propylene carbonate in the electrolyte to satisfy 29 ≤ X1 + X2 ≤ 51 and / or 1.1 ≤ X2 / X1 ≤ 2.5 can improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of the secondary battery. Furthermore, adjusting the mass percentages of these two components to satisfy 34 ≤ X1 + X2 ≤ 46 and / or 1.6 ≤ X2 / X1 ≤ 2.2 can result in even lower growth rates of high-temperature intermittent cycle resistance and fast-charge cycle resistance of the lithium-ion battery.

[0149] Specifically, controlling the mass percentage of ethyl propionate and propyl propionate in the electrolyte to satisfy at least one of 35 ≤ Y1 + Y2 ≤ 62 or 1.2 ≤ Y2 / Y1 ≤ 2.9 can improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries. Especially when satisfying at least one of 41 ≤ Y1 + Y2 ≤ 55 or 1.5 ≤ Y2 / Y1 ≤ 2.5, the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries can be further improved.

[0150] In particular, adding fluorinated compounds such as fluorobenzene and / or fluoroethylene carbonate to the electrolyte, especially controlling the mass percentages of fluorobenzene and fluoroethylene carbonate in the electrolyte to satisfy 0.9≤F1≤4.1 and / or 10.5≤F2≤19.5 respectively, can enhance the adsorption capacity of the generated solid electrolyte interface film for carbon nanotubes, thereby improving the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries. Further adjusting the mass percentages of fluorobenzene and fluoroethylene carbonate in the electrolyte to satisfy 2.7≤F1≤3.4 and / or 12.5≤F2≤17.5 respectively can significantly improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries.

[0151] Except for <Preparation of Electrolyte>, all other examples in Table 2 are the same as those in Examples 1-1.

[0152] The <Preparation of Electrolyte> in Table 2 for each embodiment is as follows:

[0153] In a dry argon atmosphere glove box, lithium hexafluorophosphate (LiPF6) was dissolved in a mixed solution containing ethylene carbonate, propylene carbonate, ethyl propionate, propyl propionate, dinitrile compounds, trinitrile compounds, and fluoroethylene carbonate. Based on the mass of the electrolyte, the LiPF6 content was 12%, and the contents of other substances are shown in Table 2, with the balance being ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate. Based on the mass of the electrolyte, the content ratio of ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate was 1:2:1:2.

[0154] Table 2

[0155]

[0156]

[0157] In Table 2, based on the mass of the electrolyte, A1 (%) is the mass percentage of succinic anion, A2 (%) is the mass percentage of adiponitrile, B1 (%) is the mass percentage of 1,2-bis(2-cyanoethoxy)ethane, B2 (%) is the mass percentage of 1,3,6-hexanetrionitrile, F1 (%) is the mass percentage of fluorobenzene, F2 (%) is the mass percentage of fluoroethylene carbonate, H (%) is the mass percentage of compound I, and G (%) is the mass percentage of compound II.

[0158] As shown in Table 2, this application controls the inclusion of succinic anionibacterium and adiponitrile in the electrolyte, and adjusts the mass percentage of succinic anionibacterium and adiponitrile to satisfy 1.27≤A1 / A2≤3.36, which can improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries. In particular, satisfying 1.84≤A1 / A2≤2.91 can significantly improve the growth rate of high-temperature intermittent cycle resistance and fast-charge cycle resistance of lithium-ion batteries.

[0159] Specifically, the electrolyte of this application comprises 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile, and by controlling the mass percentage content of 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile to satisfy 0.83≤B1 / B2≤2.43, the growth rate of high-temperature intermittent cycle resistance and the growth rate of fast-charge cycle resistance of the secondary battery can be improved. When the relationship between the two is preferably 1.36≤B1 / B2≤2.00, the growth rate of high-temperature intermittent cycle resistance and the growth rate of fast-charge cycle resistance of the lithium-ion battery can be further reduced.

[0160] Specifically, adding a compound of formula I to the electrolyte and adjusting its mass percentage in the electrolyte to satisfy 0.2 ≤ H ≤ 0.9 can further improve the growth rate of high-temperature intermittent cycling resistance and the growth rate of fast-charging cycling resistance. On the other hand, controlling the addition of a compound of formula II to the electrolyte and adjusting its mass percentage in the electrolyte to satisfy 0.2 ≤ G ≤ 0.7 can significantly improve the growth rate of high-temperature intermittent cycling resistance and the growth rate of fast-charging cycling resistance of lithium-ion batteries.

[0161] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the principles and scope of the present application.

Claims

1. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode binder layer disposed on at least one surface of the negative electrode current collector, characterized in that, The thickness of the negative electrode mixture layer is T μm; the negative electrode mixture layer contains carbon nanotubes and silicon-based particles, and the average particle size of the silicon-based particles is D μm, 3.7 ≤ 10T / D 2 ≤24.9; The electrolyte comprises a dinitrile compound and a trinitrile compound, wherein the mass percentage of the dinitrile compound is N1% and the mass percentage of the trinitrile compound is N2%, with 3.2 ≤ N1 ≤ 6.8 and 1.4 ≤ N2 ≤ 2.

9. The electrolyte also includes a fluorinated compound, which includes at least one of fluorobenzene or fluoroethylene carbonate.

2. The secondary battery according to claim 1, wherein the dinitrile compound comprises at least one selected from malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxadipropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, The trinitrile compound includes at least one of 1,3,6-hexanetrionitrile, 1,3,5-pentanetricarboxynitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane.

3. The secondary battery according to claim 1, wherein the dinitrile compound comprises at least two selected from malononitrile, butadionitrile, glutaronitrile, adiponitrile, heptanonitrile, octadionitrile, 3,3'-oxopropionitrile, hex-2-enadionitrile, trans-butenedionitrile, 2-pentenedionitrile, methylglutaronitrile, (Z)-but-2-enadionitrile, 2,2,3,3-tetrafluorobutadionitrile, or 1,2-bis(2-cyanoethoxy)ethane; and / or, The trinitrile compound includes at least two of 1,3,6-hexanetrionitrile, 1,3,5-pentanetricarboxynitrile, 4-(2-cyanoethyl)heptanedionitrile, or 1,2,3-tris(2-cyanoethoxy)propane.

4. In the secondary battery according to any one of claims 1 to 3, 1.1 ≤ N1 / N2 ≤ 4.

9.

5. The secondary battery according to claim 4, wherein the secondary battery satisfies at least one of the following: (1)7.0≤10T / D 2 ≤18.1; (2)60≤T≤122； (3)7.0≤D≤12.7； (4) 2.2≤N1 / N2≤3.

7.

6. The secondary battery according to claim 5, wherein the secondary battery satisfies at least one of the following: (1)78.2≤T≤113.0； (2)7.6≤D≤10.6； (3)4.2≤N1≤5.9； (4)1.6≤N2≤2.5。 7. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte satisfies at least one of the following: (1) The electrolyte includes succinate and adiponitrile. Based on the mass of the electrolyte, the mass percentage of succinate is A1% and the mass percentage of adiponitrile is A2%, and 1.27≤A1 / A2≤3.36; (2) The electrolyte comprises 1,2-bis(2-cyanoethoxy)ethane and 1,3,6-hexanetrionitrile, and based on the mass of the electrolyte, the mass percentage of 1,2-bis(2-cyanoethoxy)ethane is B1%, the mass percentage of 1,3,6-hexanetrionitrile is B2%, and 0.83≤B1 / B2≤2.

43.

8. The secondary battery according to claim 7, wherein the electrolyte satisfies at least one of the following: (1)2.8≤A1≤3.7； (2)1.1≤A2≤2.2； (3)1.0≤B1≤1.7； (4)0.7≤B2≤1.2； (5) 1.84≤A1 / A2≤2.91; (6) 1.36≤B1 / B2≤2.

00.

9. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte comprises ethylene carbonate and propylene carbonate, and based on the mass of the electrolyte, the mass percentage of ethylene carbonate is X1%, the mass percentage of propylene carbonate is X2%, and the electrolyte satisfies at least one of the following: (1) 29 ≤ X1 + X2 ≤ 51; (2) 1.1 ≤ X2 / X1 ≤ 2.

5.

10. The secondary battery according to claim 9, wherein the electrolyte satisfies at least one of the following: (1) 34 ≤ X1 + X2 ≤ 46; (2) 1.6 ≤ X2 / X1 ≤ 2.

2.

11. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte comprises ethyl propionate and propyl propionate, and based on the mass of the electrolyte, the mass percentage of ethyl propionate is Y1%, the mass percentage of propyl propionate is Y2%, and the electrolyte satisfies at least one of the following: (1) 35≤Y1+Y2≤62; (2) 1.2≤Y2 / Y1≤2.

9.

12. The secondary battery according to claim 11, wherein the electrolyte satisfies at least one of the following: (1) 41≤Y1+Y2≤55; (2) 1.5 ≤ Y2 / Y1 ≤ 2.

5.

13. The secondary battery according to any one of claims 1 to 3, wherein, based on the mass of the electrolyte, the electrolyte satisfies at least one of the following: (1) The mass percentage of the fluorobenzene is F1%, 0.9 ≤ F1 ≤ 4.1; (2) The mass percentage of the fluoroethylene carbonate is F2%, 10.5≤F2≤19.

5.

14. The secondary battery according to claim 13, wherein the electrolyte satisfies at least one of the following: (1)2.7≤F1≤3.4； (2)12.5≤F2≤17.5。 15. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte comprises a compound of formula I, and the chemical formula of the compound of formula I is: Based on the mass of the electrolyte, the mass percentage of the compound of formula I is H%, and 0.2 ≤ H ≤ 0.9%.

16. The secondary battery according to any one of claims 1 to 3, wherein the electrolyte comprises a compound of formula II, and the chemical formula of the compound of formula II is: Based on the mass of the electrolyte, the mass percentage of the compound of formula II is G%, where 0.2 ≤ G ≤ 0.

7.

17. The secondary battery according to claim 1, wherein the silicon-based particles comprise a carbon skeleton and a protective layer located on at least a portion of the surface of the carbon skeleton, the material of the protective layer comprising amorphous carbon, and the material of the carbon skeleton comprising at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, or hard carbon.

18. An electronic device comprising a secondary battery according to any one of claims 1 to 17.

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