Secondary battery and electronic apparatus

Abstract

A secondary battery and an electronic apparatus. The secondary battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises a lithium cobalt oxide and a polymer P, the negative electrode comprises graphite and silicon-carbon, and the electrolyte comprises lithium difluorophosphate, 1,3,6-hexanetricarbonitrile and a nitrogen-containing lithium salt. The design not only can improve the cycle performance and the low-temperature rate performance of the secondary battery, but also can remarkedly improve the electrode swelling resistance after cycling.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of energy storage, specifically to a secondary battery and electronic device. Background Technology

[0002] Currently, with the rapid development and continuous expansion of the new energy vehicle industry, the development of high-power, high-capacity, and high-safety battery systems is urgently needed. Silicon-based anode materials have gained widespread attention and extensive research due to their advantages such as high theoretical specific capacity, low lithium intercalation potential, abundant raw materials, non-toxicity, and environmental friendliness, and are expected to replace carbon anode materials as the next generation of high-performance lithium battery anode materials.

[0003] However, silicon-based anode materials experience significant volume expansion during repeated lithium insertion / extraction processes, with volume changes reaching up to 400%. This leads to the breakage and pulverization of active particles, unstable and continuous growth of the surface SEI film, and severe electrode structure collapse. Consequently, the electrochemical performance of silicon anodes rapidly degrades, resulting in reduced battery capacity, cycle life, and coulombic efficiency. Furthermore, silicon's poor conductivity increases internal resistance, especially at low temperatures, leading to a significant deterioration in battery cycle performance. Summary of the Invention

[0004] The embodiments of this application address, to some extent, the problems existing in the prior art by adjusting the electrode composition and electrolyte composition used in secondary batteries.

[0005] The inventors of this application have discovered that the positive electrode comprises lithium cobalt oxide and polymer P, wherein polymer P contains nitrile-containing monomer units; the negative electrode comprises graphite and silicon carbide compounds; and the electrolyte comprises lithium difluorophosphate, 1,3,6-hexanetricarbonitrile and nitrogen-containing lithium salt. This design not only improves the cycle performance and low-temperature rate performance of secondary batteries, but also significantly enhances the electrode's resistance to expansion after cycling.

[0006] In secondary batteries where the positive electrode includes lithium cobalt oxide and polymer P, and the negative electrode uses silicon-carbon materials, and the electrolyte contains (I) lithium difluorophosphate, (II) 1,3,6-hexanetricarbonyl nitrile and (III) nitrogen-containing lithium salts, and more importantly, the total content of (I) to (III) is set within a specific range, although the reason for improving the cycle performance and low-temperature rate performance of the secondary battery is still unclear, it is believed that during the first charge-discharge cycle, the components (I) to (III) in the electrolyte not only form a low-resistance coating on the surface of the positive electrode, but also form a stable coating on the surface of the negative electrode. As a result, not only can the cycle performance and low-temperature rate performance of the secondary battery be improved, but the electrode expansion resistance after cycling is also significantly improved.

[0007] In another aspect of this application, an electronic device is provided that includes the secondary battery described in this application.

[0008] By using a specific combination of electrode configuration and electrolyte, this application not only improves the cycle performance and low-temperature rate performance of secondary batteries, but also significantly enhances the electrode's resistance to expansion after cycling.

[0009] 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

[0010] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0011] Unless otherwise expressly stated, the terms used in this application shall have the meanings indicated below.

[0012] By using a specific combination of electrode configuration and electrolyte, this application not only improves the cycling performance and low-temperature rate capability of secondary batteries, but also significantly enhances the electrode's resistance to expansion after cycling.

[0013] In one embodiment, this application provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte as described below.

[0014] I. Electrolyte

[0015] 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 further includes a combination of lithium difluorophosphate, 1,3,6-hexamethylenetricarbonate, and a nitrogen-containing lithium salt.

[0016] Since the coating formed by lithium difluorophosphate on the surface of silicon-carbon materials is unstable and prone to decomposition at low temperatures, the inventors discovered that when the electrolyte also contains 1,3,6-hexanetricarbonyl nitrile and nitrogen-containing lithium salt, the decomposition of the coating can be significantly reduced. Moreover, the combination of lithium difluorophosphate, 1,3,6-hexanetricarbonyl nitrile and nitrogen-containing lithium salt can also inhibit the swelling of polymer P contained in the positive electrode in the electrolyte. This design can not only improve the cycle performance and low-temperature rate performance of the secondary battery, but also significantly improve the electrode's resistance to swelling after cycling.

[0017] Specifically, from the viewpoint of improving the cycle performance of lithium-ion batteries, based on the quality of the electrolyte, the content of lithium difluorophosphate is 0.01 wt% or more, preferably 0.02 wt% or more, more preferably 0.03 wt% or more, and more preferably 0.04 wt% or more.

[0018] Furthermore, from the viewpoint of suppressing electrode expansion, the content of lithium difluorophosphate is 0.8 wt% or less as the upper limit of lithium difluorophosphate content, preferably 0.78 wt% or less, more preferably 0.59 wt% or less, even more preferably 0.37 wt% or less, and particularly preferably 0.25 wt% or less.

[0019] In some embodiments, the lithium difluorophosphate content is set to a1 wt%, where a1 is 0.01, 0.02, 0.03, 0.04, 0.05, 0.08, 0.11, 0.25, 0.37, 0.59, 0.78, 0.8, or within a range consisting of any two of the above values. For example, 0.01 to 0.05, 0.02 to 0.08, 0.03 to 0.11, 0.05 to 0.37, 0.08 to 0.25, 0.01 to 0.25, 0.05 to 0.59, 0.04 to 0.78, 0.03 to 0.8. When within the above ranges, it helps to further suppress electrode expansion.

[0020] Specifically, from the viewpoint of improving the cycle performance of lithium-ion batteries, based on the mass of the electrolyte, the content of 1,3,6-hexanetricarbonyl nitrile is 0.3 wt% or more, preferably 0.6 wt% or more, more preferably 0.8 wt% or more, and more preferably 1.2 wt% or more.

[0021] Furthermore, as an upper limit for the content of 1,3,6-hexanetrionitrile, from the viewpoint of suppressing electrode expansion, the content of 1,3,6-hexanetrionitrile is 5 wt% or less, preferably 4.9 wt% or less, more preferably 4.2 wt% or less, even more preferably 3.5 wt% or less, and particularly preferably 2.1 wt% or less.

[0022] In some embodiments, the content of 1,3,6-hexanetrionitrile is set as a2 wt%, where a2 is 0.3, 0.6, 0.8, 1.2, 1.7, 1.9, 2.1, 3.5, 4.2, 4.9, 5, or within any two of the above values. For example, 0.3 to 1.9, 0.6 to 2.1, 0.8 to 3.5, 1.2 to 4.2, 1.7 to 4.9, 1.2 to 5, when within the above ranges, helps to further suppress electrode expansion.

[0023] In some embodiments, the nitrogen-containing lithium salt includes LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiN(CF3SO2)(C4F9SO2), 4,5-dicyano-2-trifluoromethylimidazolium lithium salt, 4,5-dicyano-2-pentafluoroethylimidazolium lithium salt, and 2,4,5-tricyano... At least one of the following: imidazole lithium salt, 5,6-dicyano-2-trifluoromethylbenzimidazole lithium salt, 5,6-dicyano-2-pentafluoroethylbenzimidazole lithium salt, 2,5,6-tricyanobenzimidazole lithium salt, 4,7-dicyano-2-trifluoromethylbenzimidazole lithium salt, 4,7-dicyano-2-pentafluoroethylbenzimidazole lithium salt, 2,4,7-tricyanobenzimidazole lithium salt, 4,5,6,7-tetracyano-2-trifluoromethylbenzimidazole lithium salt, 4,5,6,7-tetracyano-2-pentafluoroethylbenzimidazole lithium salt, or 2,4,5,6,7-pentacyanobenzimidazole lithium salt. Due to the excellent stability of the formed coating, the battery performance is further improved. The nitrogen-containing lithium salt (III) can be only one type or two or more types.

[0024] In some embodiments, the nitrogen-containing lithium salt is preferably at least one of LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, and LiN(C2F5SO2)2.

[0025] Specifically, from the viewpoint of improving the cycle performance of lithium-ion batteries, based on the quality of the electrolyte, the content of nitrogen-containing lithium salt is 0.2 wt% or more, preferably 0.6 wt% or more, more preferably 0.8 wt% or more, and more preferably 1.1 wt% or more.

[0026] Furthermore, from the viewpoint of suppressing electrode expansion, the content of nitrogen-containing lithium salt is 3 wt% or less as an upper limit for the content of nitrogen-containing lithium salt, preferably 2.8 wt% or less, more preferably 2.4 wt% or less, even more preferably 2.1 wt% or less, and particularly preferably 1.7 wt% or less.

[0027] In some embodiments, the content of the nitrogen-containing lithium salt is set to a3 wt%, where a3 is 0.2, 0.6, 0.7, 0.8, 1.1, 1.9, 2.1, 2.4, 2.8, 3, or within a range of any two of the above values. For example, 0.2 to 1.9, 0.6 to 3, 0.7 to 2.8, 0.8 to 2.1, 1.1 to 2.8, 0.2 to 1.1, 0.2 to 0.8, when within the above ranges, helps to further improve cycle performance.

[0028] Furthermore, from the viewpoint of suppressing electrode expansion, based on the mass of the electrolyte, the total content of (I), (II) and (III) is 1.35 wt% or more, preferably 2.35 wt% or more.

[0029] Furthermore, as an upper limit for the total content of (I), (II) and (III), from the viewpoint of improving the electrochemical properties at low-temperature rates, the total content of (I), (II) and (III) is 5.65 wt% or less, preferably 4.85 wt% or less.

[0030] In some embodiments, the total content of (I), (II), and (III) is a wt%, where a is 1.35, 1.45, 1.55, 1.85, 2.35, 2.55, 2.75, 4.15, 4.85, 5.55, 5.65, or within any two of the above values. For example, 1.35 to 4.15, 1.55 to 4.85, 1.85 to 5.55, and 2.35 to 5.65, when within the above ranges, help to further suppress electrode expansion.

[0031] In addition, the electrolyte may also include other nitrile compounds. The inventors also unexpectedly discovered that other nitrile compounds can reduce the impedance of the aforementioned coating, improve lithium-ion charge transport, improve low-temperature performance and electrode expansion resistance.

[0032] Other nitrile compounds include at least one of succinic anion, adiponitrile, ethylene glycol di(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane.

[0033] The aforementioned nitrile compounds may be only one type or two or more types. For example, they include succinic anion and adiponitrile; or succinic anion and ethylene glycol di(propionitrile) ether; or adiponitrile and ethylene glycol di(propionitrile) ether.

[0034] Specifically, from the viewpoint of improving low-temperature rate performance and suppressing electrode expansion, based on the mass of the electrolyte, the content of other nitrile compounds is 0.3 wt% or more, preferably 0.6 wt% or more, more preferably 0.9 wt% or more, and more preferably 1.4 wt% or more.

[0035] Furthermore, as an upper limit for the content of other nitrile compounds, from the viewpoint of improving low-temperature rate performance and suppressing electrode expansion, the content of other nitrile compounds is 8 wt% or less, preferably 7.9 wt% or less, more preferably 7.1 wt% or less, even more preferably 6.2 wt% or less, and particularly preferably 5.3 wt% or less.

[0036] In some embodiments, the total content of other nitrile compounds is b wt%, where b is 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.4, 1.5, 2, 2.5, 3, 3.5, 3.9, 4, 4.6, 5.3, 6.2, 7.1, 7.9, 8, or within a range consisting of any two of the above values. For example, 0.3 to 5.3, 0.6 to 4.6, 0.9 to 3.9, 0.4 to 2, 0.45 to 4.6, 0.8 to 2.5, 1.4 to 3.9, 2.5 to 8, 0.9 to 6.2, 0.45 to 5.3, 0.6 to 1.4. When within the above ranges, it helps to further improve low-temperature rate performance and suppress electrode expansion.

[0037] In addition, the electrolyte may also include other additives. The inventors also unexpectedly discovered that other additives can inhibit the decomposition and regeneration of the aforementioned coating during the charge and discharge process, thereby further improving low-temperature performance and cycle performance.

[0038] Other additives include at least one of lithium monofluorophosphate, 1,2-bis(difluorophospho)ethane, lithium fluorosulfonate, vinylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,3-propanediol cyclosulfonate, fluorobenzene, cyclohexylbenzene, biphenyl, tris(trimethylsilane) phosphate, or tris(trimethylsilane) borate.

[0039] The other additives mentioned above may be only one type or two or more types.

[0040] Specifically, from the viewpoint of improving low-temperature rate performance and cycle performance, based on the quality of the electrolyte, the content of other additives is 0.3 wt% or more, preferably 0.9 wt% or more, more preferably 1.6 wt% or more, and more preferably 2.8 wt% or more.

[0041] Furthermore, as an upper limit for the content of other additives, from the viewpoint of improving low-temperature rate performance and cycle performance, the content of other additives is 10 wt% or less, preferably 9.7 wt% or less, more preferably 8.2 wt% or less, even more preferably 7.1 wt% or less, and particularly preferably 6.7 wt% or less.

[0042] In some embodiments, the total content of other additives is c wt%, where c is 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 1.6, 2, 2.5, 2.8, 3, 3.5, 3.9, 4, 4.5, 5, 5.5, 6, 6.5, 7.1, 7.5, 8.2, 8.6, 9, 9.3, 9.7, 10, or within a range consisting of any two of the above values. For example, 0.3 to 18.2, 0.45 to 7.5, 0.6 to 9.7, 5.5 to 9.7, 6 to 8.6, 2.8 to 6.5, 1 to 6.5, 0.7 to 7.1, 1.5 to 9.3, 0.45 to 3.9, 0.7 to 4.5. When within the above ranges, it helps to further improve low-temperature rate performance and cycle performance.

[0043] In some embodiments, the electrolyte is not particularly limited, and any substance known as an electrolyte can be used. The mass of the electrolyte is not particularly limited, as long as it does not impair the effectiveness of this application.

[0044] For example, the lithium salt used in the electrolyte of this application includes lithium hexafluorophosphate. Based on the mass of the electrolyte, the content of lithium hexafluorophosphate is 9 to 15 wt%, preferably 9 to 13 wt%, and more preferably 9 to 12 wt%. By setting the content within the above range, the improvement of cycle life and the enhancement of low-temperature discharge characteristics can be achieved in a more balanced manner.

[0045] In some embodiments, the electrolyte further comprises any non-aqueous solvent known in the art that can be used as a solvent for an electrolyte.

[0046] In some embodiments, the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, cyclic ethers, chain ethers, phosphorus-containing organic solvents, and sulfur-containing organic solvents.

[0047] II. Negative electrode

[0048] The negative electrode includes a negative electrode current collector and a negative electrode additive layer disposed on the 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, so as to minimize the unintentional deposition of lithium metal on the negative electrode during charging.

[0049] Furthermore, there are no particular limitations on the negative electrode active material; examples include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials that combine these elements.

[0050] Carbon-based anode active materials

[0051] Here, carbon-based anode active materials refer to active materials with carbon as the main framework that can insert lithium. Examples of carbon-based anode active materials include carbonaceous materials and graphitic materials.

[0052] Examples of carbonaceous materials include easily graphitized carbon and non-graphitized carbon with a similar amorphous structure, such as glassy carbon. Among easily graphitized carbons, examples include carbon materials derived from petroleum or coal using tar pitch as a raw material. Specific examples include coke, mesophase carbon microspheres (MCMB), mesophase pitch-based carbon fibers, and pyrolysis-grown carbon fibers. Furthermore, examples of non-graphitized carbons include phenolic resin sintered bodies, polyacrylonitrile-based carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin sintered bodies (PFA), and hard carbon.

[0053] Furthermore, examples of graphitic materials include natural graphite and artificial graphite. Among these, examples of artificial graphite include: artificial graphite formed by heat-treating carbon containing easily graphitizable carbon primarily at temperatures above 2800°C; graphitic MCMB formed by heat-treating MCMB at temperatures above 2000°C; and graphitic mesophase pitch-based carbon fiber formed by heat-treating mesophase pitch-based carbon fiber at temperatures above 2000°C. Additionally, in this application, natural graphite (amorphously coated natural graphite) can be used as the carbon-based negative electrode active material, where at least a portion of its surface is coated with amorphous carbon.

[0054] Metal-based anode active materials

[0055] Furthermore, metal-based anode active materials are active materials containing metals, generally referring to active materials whose structure contains elements capable of intercalating into or alloying with lithium, and whose theoretical current capacity per unit mass is 500 mAh / g or more when intercalated into or alloyed with lithium. Examples of metal-based anode active materials include: lithium metal, elemental metals capable of forming lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.) and their alloys, as well as their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. Among these, active materials containing silicon (silicon-based anode active materials) are preferred as metal-based anode active materials. This is because using silicon-based anode active materials enables high-capacity lithium-ion secondary batteries.

[0056] Examples of silicon-based anode active materials include: silicon (Si), silicon-containing alloys, SiO, and SiO2. x A composite material of silicon-containing materials and conductive carbon, formed by coating or compounding silicon-containing materials with conductive carbon.

[0057] From the perspective of improving battery capacity, silicon-carbon materials are preferred, such as porous carbon-supported silicon composites.

[0058] In addition, the negative electrode active material can be used alone or in combination of two or more in any ratio.

[0059] Volume average particle size of active material

[0060] Here, the volume average particle size of the negative electrode active material is preferably 1 μm or more, more preferably 5 μm or more, more preferably 30 μm or less, and more preferably 20 μm or less. If the volume average particle size of the negative electrode active material is above or below the above-mentioned lower limit, electrode expansion can be effectively suppressed. In addition, if the volume average particle size of the negative electrode active material is below or below the above-mentioned upper limit, the cycling performance of the resulting battery can be effectively suppressed.

[0061] Mass per unit area of ​​negative electrode mixture layer

[0062] Specifically, from the perspective of improving cycle performance, the mass per unit area of ​​the negative electrode mixture layer is 4.5 mg / cm². 2 The above, preferably 5.1 mg / cm³ 2 The above, preferably 5.5 mg / cm³ 2 The above, more preferably 6.2 mg / cm³ 2 above.

[0063] Furthermore, from the perspective of improving low-temperature rate performance, the upper limit of the mass per unit area of ​​the negative electrode mixture layer is 12.5 mg / cm³, which serves as the upper limit for the mass of the negative electrode mixture layer per unit area. 2 The preferred value is 11.2 mg / cm³. 2 The following is more preferably 10.5 mg / cm³ 2 The following is a further preferred value: 9.3 mg / cm³ 2 The following is particularly preferred: 8.1 mg / cm³ 2 the following.

[0064] In some embodiments, the mass per unit area of ​​the negative electrode mixture layer is w mg / cm³. 2The values ​​w are 4.5, 4.8, 5.1, 5.3, 5.5, 6.2, 7.8, 8.1, 9.3, 10.5, 11.2, 12.3, 12.5, or within any two of the above values. For example, values ​​4.5 to 9.3, 4.8 to 12.3, 5.1 to 8.1, 5.3 to 10.5, 5.5 to 12.3, 6.2 to 11.2, 7.8 to 12.5, 8.1 to 10.5, 9.3 to 12.5, 5.3 to 9.3, and 6.2 to 8.1. When these values ​​are within the above ranges, it helps to further suppress electrode expansion.

[0065] Furthermore, from the viewpoint of suppressing electrode expansion, the aforementioned a / w is 0.124 or higher and 1.009 or lower. In some embodiments, a / w is 0.124, 0.241, 0.259, 0.33, 0.42, 0.455, 0.491, 0.555, 0.608, 0.647, 0.741, 0.866, 0.991, 1.009, or within a range consisting of any two of the above values. For example, 0.124 to 0.741, 0.241 to 0.491, 0.33 to 1.009, and 0.555 to 0.866, when within the above ranges, helps to further suppress electrode expansion.

[0066] The mass per unit area of ​​the negative electrode mixture layer is the mass (mg) of the negative electrode mixture layer relative to the area (cm²) of the mixture layer. 2 The mass and area of ​​the negative electrode mixture layer are obtained as follows: A test piece of appropriate size is cut from the negative electrode, its area is measured as S1 and its mass as W0. Then, the negative electrode current collector is peeled off from the negative electrode, and its mass as W1 is measured. The mass of the negative electrode mixture layer is calculated from (W0-W1), where mass per unit area = (W0-W1) / S1. If the selected negative electrode is a double-sided mixture layer, then the mass per unit area = (W0-W1) / S1 / 2.

[0067] Methods for peeling off the negative electrode compound layer include, for example, immersing the negative electrode compound layer in a solvent that can dissolve or swell the negative electrode compound layer, or wiping the compound layer with a cloth.

[0068] The mass per unit area of ​​the negative electrode mixture layer can be adjusted using known methods. For example, when forming the negative electrode mixture layer by coating, it can be adjusted by changing the solid component concentration of the coating liquid used to form the negative electrode mixture layer, the number of coating passes, and the gap of the coating liquid inlet of the coating machine. The mass per unit area of ​​the negative electrode mixture layer can be increased by increasing the solid component concentration, increasing the number of coating passes, or increasing the gap. Conversely, the mass per unit area of ​​the negative electrode mixture layer can be decreased by decreasing the solid component concentration, decreasing the number of coating passes, or decreasing the gap.

[0069] The negative electrode mixture 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 preparing the negative electrode mixture slurry using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salts, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0070] As the current collector for retaining the active material of the negative electrode, any known current collector can be used. Examples of negative electrode current collectors include, but are not limited to, metallic materials such as copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0071] The negative electrode can be prepared by coating a negative electrode slurry containing negative electrode active material, resin binder, etc. onto the 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.

[0072] III. Positive electrode

[0073] The positive electrode includes a positive current collector and a positive electrode mixture layer disposed on the surface of the positive current collector.

[0074] The positive electrode additive layer contains a positive electrode active material, and the positive electrode additive layer can be one or more layers. The positive electrode active material is any substance capable of reversibly inserting and deintercalating lithium ions.

[0075] For example, as positive electrode active materials for lithium-ion batteries, composite metal oxides containing one or more lithium-containing metals selected from the group consisting of cobalt, manganese, and nickel, or olivine-type phosphates containing one or more lithium-containing metals selected from iron, cobalt, nickel, and manganese are used. These positive electrode active materials can be used alone or in combination of two or more.

[0076] Suitable examples of such lithium composite metal oxides include, for instance, those selected from LiCoO2, LiMn2O4, LiNiO2, and LiCo. 1-x Ni x O2(0.01 <x<1)、LiNi x Mn y Co z O2 (x+y+z=1), solid solutions of Li2MnO3 and LiMO2 (M is a transition metal such as Co, Ni, Mn, Fe, etc.), LiNi 1 / 2 Mn3 / 2 O4, LiFePO4, LiMnPO4, and LiMn 1-x One or more of FexPO4 (0.01 < x < 1), more preferably two or more. A part of these composite metal oxides with lithium or olivine-type phosphates containing lithium may be substituted with other elements, or a part of cobalt, nickel, manganese, and iron may be substituted with one or two or more elements selected from Co, Mn, Ni, Mg, Al, B, Ti, V, Nb, Cu, Zn, Mo, Ca, Sr, W, and Zr, or coated with a compound containing these other elements or a carbon material.

[0077] For example, the positive electrode contains a lithium cobalt oxide having at least three hetero elements among aluminum, magnesium, titanium, zirconium, lanthanum, iridium, cerium, and tungsten. From the viewpoint of improving the cycle characteristics of the lithium ion battery, based on the mass of the lithium cobalt oxide, the content of any one of the hetero elements is preferably 0.01 wt% or more, preferably 0.03 wt% or more, more preferably 0.05 wt% or more. In addition, as the upper limit of the content of the hetero element, the content of any one of the hetero elements is 1 wt% or less, preferably 0.5 wt% or less, more preferably 0.3 wt% or less, further preferably 0.15 wt% or less, and particularly preferably 0.1 wt% or less.

[0078] When using a lithium composite metal oxide that operates at a high charging voltage, the electrochemical characteristics are likely to deteriorate in a high-temperature environment due to the reaction with the non-aqueous electrolyte during charging, but in the lithium ion battery described in the present application, the deterioration of these electrochemical characteristics can be suppressed.

[0079] As the voltage during charging, from the viewpoint of increasing the voltage, the positive electrode potential is preferably 4.4 V (vs. Li / Li+) or more, more preferably 4.5 V (vs. Li / Li+) or more, and particularly preferably 4.6 V (vs. Li / Li+) or more.

[0080] From the viewpoint of suppressing electrode swelling, the positive electrode binder includes a polymer P, and the polymer P can play a binding role between the electrode active materials and between the electrode active material and the current collector.

[0081] As described above, the polymer P at least contains: a nitrile group-containing monomer unit; preferably polyacrylonitrile.

[0082] Examples of nitrile-containing monomers capable of forming nitrile-containing monomer units include α,β-ene unsaturated nitrile monomers. Specifically, there are no particular limitations on α,β-ene unsaturated nitrile monomers, as long as they are α,β-ene unsaturated compounds having a nitrile group; examples include acrylonitrile; α-haloacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile. Furthermore, nitrile-containing monomers can be used alone or in combination of two or more in any ratio.

[0083] There are no particular restrictions on the conductive agent used in the positive electrode, as long as it is an electron-conducting material that does not cause chemical changes. Examples include natural graphite (flake graphite, etc.), artificial graphite, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal cracking black, etc. Furthermore, graphite and carbon black can be appropriately mixed. The preferred amount of conductive agent added to the positive electrode mixture is 1–10 wt%, particularly preferably 1.5–5 wt%.

[0084] The positive electrode can be manufactured as follows: The above-mentioned positive electrode active material is mixed with conductive agents such as acetylene black and carbon black, and binders such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, copolymer of styrene and butadiene, and carboxymethyl cellulose. A high-boiling-point solvent such as 1-methyl-2-pyrrolidone is added and the mixture is kneaded to form a positive electrode slurry. This slurry is then coated onto an aluminum foil or similar current collector, dried, and pressurized to form a positive electrode slurry layer.

[0085] The density of the positive electrode, excluding the current collector, is typically 3.5 g / cm³. 3 In order to further improve the battery capacity, a value of 3.8 g / cm³ is preferred. 3 The above, more preferably 4g / cm 3 The above is further optimized to 4.1 g / cm³. 3 That's all. Furthermore, as an upper limit, 4.6 g / cm³ is preferred. 3 the following.

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

[0087] 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.

[0088] 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.

[0089] IV. Separating membrane

[0090] 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.

[0091] 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 may be a resin, glass fiber, inorganic material, or other material formed from a material stable to the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of 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.

[0092] 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.

[0093] 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.

[0094] The separator can be in the form of a thin film, examples of which include, but are not limited to, nonwoven fabrics, woven fabrics, microporous membranes, etc. In the form of a thin film, 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 separator, the following separator can also be used: a separator formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or negative electrode, for example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0095] 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, as well as the rate performance and energy density of the secondary battery.

[0096] This application also provides an electronic device that includes a secondary battery as described in this application.

[0097] 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, 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.

[0098] The preparation of secondary batteries is described below with reference to specific embodiments. 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.

[0099] Example

[0100] The following are examples of non-aqueous electrolytes of this application, but this application is not limited to these examples.

[0101] Manufacturing of lithium-ion batteries

[0102] The positive electrode active material (97 wt%) and acetylene black (1.5 wt%) from Table 1-1 were mixed and added to a solution obtained by dissolving 1.5 wt% polyacrylonitrile in 1-methyl-2-pyrrolidone. This mixture was then used to prepare a positive electrode paste. The paste was coated onto aluminum foil, dried, pressurized, and then cut to the specified size to fabricate the positive electrode.

[0103] In addition, 96 wt% of the negative electrode active material and 2 wt% of styrene-butadiene rubber from Table 1-1 were mixed and added to a solution obtained by dissolving 2 wt% of lithium carboxymethyl cellulose in deionized water, and then mixed to prepare a negative electrode paste. This negative electrode paste was coated onto copper foil, dried, pressurized, and then cut to the specified size to fabricate the negative electrode. The unit area mass of the negative electrode paste layer was obtained by controlling the coating thickness.

[0104] The positive and negative electrodes prepared as described above were each connected to a wire. A laminate was obtained by stacking the laminates through a 10 μm thick polypropylene porous membrane. Furthermore, LiPF6, serving as the supporting electrolyte, was dissolved in a solution containing (I) lithium difluorophosphate, (II) 1,3,6-hexamethylenetricarbonate, (III) a nitrogen-containing lithium salt, and propyl propionate, ethyl propionate, ethylene carbonate, and propylene carbonate (mass ratio 2.3:2:1.2:0.9). Based on 100 parts by mass of the total non-aqueous electrolyte, the contents and composition of (I) to (III), other nitrile compounds, and other additives are shown in Tables 1 and 2, with the LiPF6 content being 14%.

[0105] The laminated body and 3.2g of electrolyte are then housed together in an aluminum laminated casing. The opening of the casing is heat-sealed, and a lithium-ion battery is manufactured through formation, capacity testing, and other steps. This lithium-ion battery is a pouch-shaped structure with a width of 35mm, a height of 48mm, and a thickness of 5mm.

[0106] Table 1

[0107] Table 1 shows the positive and negative electrode materials and electrolyte component codes of the prepared lithium-ion batteries. The detailed composition is shown in Tables 1-1, 1-2, and 1-3, respectively.

[0108] [Revised according to Detailed Rules 26, 03.07.2026] Table 1: Codes for Positive and Negative Electrode Materials and Some Electrolyte Components of Lithium-ion Batteries

[0109] [Revised according to Rule 26, 03.07.2026] The values ​​in parentheses above are all in wt%.

[0110] [Revised according to Rule 26, 03.07.2026] Table 1-1 Codes of Positive Electrode Active Material Components

[0111] [Revised according to Detailed Rules 26, 03.07.2026] Table 1-2 Negative Electrode Active Material Component Codes

[0112] [Revised according to Detailed Rules 26, 03.07.2026] Table 1-3 Electrolyte Component Codes

[0113] Test methods

[0114] Cyclic characteristics

[0115] The lithium-ion batteries prepared in the examples and comparative examples were left to stand at 25°C for 5 hours after electrolyte injection. First, they were charged at 25°C using a constant current method at 0.2C to a battery voltage of 4.6V, and then aged at 60°C for 12 hours. Next, they were discharged at 25°C using a constant current method at 0.2C to a battery voltage of 3.0V. Then, they were charged using a constant current method at 0.2C using a CC-CV (constant current-constant voltage) method (upper limit battery voltage 4.6V), and discharged using a constant current method at 0.2C to 3.0V, and their initial discharge capacity X1 was measured. Then, at 45°C, 50 cycles of charge-discharge operation were performed with a battery voltage of 4.6-3.0V and a charge-discharge rate of 1.0C. Finally, at 0°C, 50 cycles of charge-discharge operation were performed with a battery voltage of 4.6-3.0V and a charge-discharge rate of 0.5C. Furthermore, at 25°C, the battery was charged using a constant current method at 0.2C (battery voltage 4.6V), and then discharged using a constant current method at 0.2C until the battery voltage reached 3.00V. The discharge capacity X2 was then measured. Using the initial discharge capacity X1 and the discharge capacity X2, the capacity retention rate, expressed as ΔC' = (X2 / X1) × 100 (%), was calculated and evaluated according to the following criteria. A indicates the best cycle performance, and D indicates the worst cycle performance.

[0116] A: Capacity retention rate ΔC' is above 85%.

[0117] B: Capacity retention rate ΔC' is above 80% and less than 85%.

[0118] C: Capacity retention ΔC' is 75% or higher and less than 80%.

[0119] D: Capacity retention rate ΔC' is less than 75%.

[0120] Low temperature ratio

[0121] The lithium-ion batteries prepared in the examples and comparative examples were left to stand at 25°C for 5 hours after electrolyte injection. Then, they were charged at 0.2C constant current at 25°C until the battery voltage reached 4.6V, followed by aging at 60°C for 12 hours. Next, they were discharged at 0.2C constant current at 25°C until the battery voltage reached 3.0V. Then, they were charged at 0.2C constant current using a CC-CV method (constant current-constant voltage) (upper limit battery voltage 4.6V), and discharged at 0.2C constant current using a CC method until the battery voltage reached 3.0V. This 0.2C charge-discharge cycle was repeated three times. Finally, at 25°C, constant current charge-discharge was performed at 0.5C between 4.6V and 3.0V; the discharge capacity at this point is defined as C0. Then, CC-CV charging was performed at a constant current of 0.2C, and then discharged to 2.5V at a constant current of 0.5C in an environment of -20℃. The discharge capacity at this point is defined as C1. Then, as a rate characteristic, the capacity retention rate shown as ΔC = (C1 / C0) × 100 (%) is calculated and evaluated according to the following benchmarks. A indicates the best low-temperature characteristics (high discharge capacity and low internal resistance under high current conditions in a low-temperature environment), and D indicates the lowest low-temperature characteristics.

[0122] A: Capacity retention rate ΔC is above 80%.

[0123] B: Capacity retention rate ΔC is above 75% and less than 80%.

[0124] C: Capacity retention ΔC is above 70% and less than 75%.

[0125] D: Capacity retention rate ΔC is less than 70%.

[0126] Electrode expansion resistance after cycling

[0127] After the first 50 cycles of the <Cycling Characteristics> section above, the battery was charged at 1C at 25°C. The charged battery was then disassembled, and the positive electrode was removed. The thickness (d2) of the positive electrode (excluding the current collector) was measured. Then, the rate of change of the thickness of the positive electrode after cycling relative to the thickness (d0) of the positive electrode before cycling (before manufacturing the lithium-ion battery) [{(d2-d0) / d0}×100(%)] was calculated. The following criteria were then used for evaluation: A indicates the best electrode swelling tolerance after cycling, and D indicates the lowest electrode swelling tolerance after cycling.

[0128] A: The rate of change in thickness is less than 10%.

[0129] B: The thickness variation rate is greater than 10% but less than 15%.

[0130] C: The rate of change in thickness is greater than 15% but less than 20%.

[0131] D: The thickness variation rate is above 25%.

[0132] Table 2

[0133] In Table 2, based on the total mass of the electrolyte, a1 represents the content of (I) lithium difluorophosphate (wt%), a2 represents the content of (II) 1,3,6-hexamethylenetrimethylonitrile (wt%), a3 represents the content of (III) nitrogen-containing lithium salt (wt%), a represents the total content of (I), (II), and (III), and w represents the mass per unit area of ​​the negative electrode binder layer (mg / cm²). 2 ), b represents the total content of other nitrile compounds (in wt%), and c represents the total content of other additives (in wt%).

[0134] [Revised according to Rule 26, 03.07.2026] Table 2: Content of some components in the electrolyte and electrochemical performance of lithium-ion batteries

[0135] In a secondary battery where the positive electrode includes lithium cobalt oxide and polymer P, and the negative electrode uses silicon-carbon materials, the electrolyte contains (I) lithium difluorophosphate, (II) 1,3,6-hexanetricarbonyl nitrile, and (III) nitrogen-containing lithium salt. During the first cycle, components (I) to (III) form a stable coating on the electrode surface, which inhibits the damage of the electrolyte to the negative electrode during charge-discharge cycles and reduces the consumption of active lithium due to coating decomposition and regeneration. This not only improves the cycle performance and low-temperature rate performance of the secondary battery, but also significantly enhances the electrode's resistance to expansion after cycling.

[0136] In particular, when the electrolyte also contains other nitrile compounds, it can reduce the impedance of the aforementioned coating, improve lithium-ion charge transport, and significantly enhance the low-temperature rate performance and electrode expansion resistance of lithium-ion batteries.

[0137] In particular, when the electrolyte also contains other additives, the inventors unexpectedly discovered that these other additives can inhibit the decomposition of the aforementioned coating during charge-discharge cycles, thereby improving cycle performance and low-temperature rate performance.

[0138] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in an example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics in this application can be combined in any suitable manner in one or more embodiments or examples.

[0139] 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 spirit, principles and scope of the present application.

Claims

1. A secondary battery, comprising: Positive electrode, negative electrode, and electrolyte. The positive electrode comprises lithium cobalt oxide and polymer P, wherein polymer P contains nitrile-containing monomer units; the negative electrode comprises graphite and silicon carbon. The electrolyte contains (I) lithium difluorophosphate, (II) 1,3,6-hexanetricarbonyl nitrile and (III) nitrogen-containing lithium salt, and the total content of (I), (II) and (III) based on the mass of the electrolyte is more than 1.35 wt% and less than 5.65 wt%.

2. The secondary battery according to claim 1, wherein, The lithium cobalt oxide contains at least three heteroelements selected from aluminum, magnesium, titanium, zirconium, lanthanum, iridium, cerium, and tungsten; based on the mass of the lithium cobalt oxide, the content of any one of the heteroelements is more than 0.01 wt% and less than 1 wt%.

3. The secondary battery according to claim 1 or 2, wherein, The polymer P includes polyacrylonitrile.

4. The secondary battery according to any one of claims 1 to 3, wherein, The nitrogen-containing lithium salts include LiN(FCO)₂, LiN(FCO)(FSO₂), LiN(FSO₂)₂, LiN(FSO₂)(CF₃SO₂), LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, cyclic 1,2-perfluoroethane disulfonylimide lithium, cyclic 1,3-perfluoropropane disulfonylimide lithium, LiN(CF₃SO₂)(C₄F₉SO₂), 4,5-dicyano-2-trifluoromethylimidazolium lithium salt, 4,5-dicyano-2-pentafluoroethylimidazolium lithium salt, and 2,4,5-tricyanoimidazolium lithium. The lithium salt, 5,6-dicyano-2-trifluoromethylbenzimidazole lithium salt, 5,6-dicyano-2-pentafluoroethylbenzimidazole lithium salt, 2,5,6-tricyanobenzimidazole lithium salt, 4,7-dicyano-2-trifluoromethylbenzimidazole lithium salt, 4,7-dicyano-2-pentafluoroethylbenzimidazole lithium salt, 2,4,7-tricyanobenzimidazole lithium salt, 4,5,6,7-tetracyano-2-trifluoromethylbenzimidazole lithium salt, 4,5,6,7-tetracyano-2-pentafluoroethylbenzimidazole lithium salt, or at least one of 2,4,5,6,7-pentacyanobenzimidazole lithium salt.

5. The secondary battery according to any one of claims 1 to 4, wherein, Based on the mass of the electrolyte The lithium difluorophosphate content is 0.01 wt% or more and 0.8 wt% or less; The mass content of the 1,3,6-hexanetrionitrile is more than 0.3 wt% and less than 5 wt%; The mass content of the nitrogen-containing lithium salt is above 0.2 wt% and below 3 wt%.

6. The secondary battery according to any one of claims 1 to 5, wherein, Based on the mass of the electrolyte, the total content of lithium difluorophosphate, 1,3,6-hexamethylenetricarbonate and nitrogen-containing lithium salt is more than 1.85 wt% and less than 5.55 wt%.

7. The secondary battery according to any one of claims 1 to 6, wherein, The negative electrode includes a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, wherein the mass per unit area of ​​the negative electrode mixture layer is 4.5 mg / cm³. 2 Above and 12.5 mg / cm 2 Based on the mass of the electrolyte, the total content of lithium difluorophosphate, 1,3,6-hexanetricarbonyl nitrile and nitrogen-containing lithium salt is a, and the mass per unit area of ​​the negative electrode mixture layer is w, where a and w satisfy: a / w is 0.124 or more and 1.009 or less.

8. The secondary battery according to any one of claims 1 to 7, wherein, The electrolyte also contains other nitrile compounds, including at least one selected from succinic anhydride, adiponitrile, ethylene glycol di(propionitrile) ether, 1,3,5-pentanetricarbonyl, 1,2,3-propanetricarbonyl, 1,2,6-hexanetricarbonyl, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane. Based on the mass of the electrolyte, the content of the other nitrile compounds is 0.3 wt% or more and 8 wt% or less, preferably 0.6 wt% or more and 7.1 wt% or less, more preferably 1.4 wt% or more and 6.2 wt% or less.

9. The secondary battery according to any one of claims 1 to 8, wherein, The electrolyte also includes other additives, including at least one of lithium monofluorophosphate, 1,2-bis(difluorophospho)ethane, vinylene carbonate, fluoroethylene carbonate, lithium fluorosulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,3-propanediol cyclosulfonate, fluorobenzene, cyclohexylbenzene, biphenyl, tris(trimethylsilane) phosphate, or tris(trimethylsilane) borate. Based on the mass of the electrolyte, the content of the other additives is 0.3 wt% or more and 10 wt% or less, preferably 0.6 wt% or more and 7.1 wt% or less, more preferably 1.4 wt% or more and 6.2 wt% or less.

10. An electronic device comprising a secondary battery according to any one of claims 1 to 9.

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