Electrolyte, battery, battery pack and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electric equipment, the electrolyte comprises a sulfone compound, a nitrile compound and an ether compound, and the sulfone compound comprises a compound with a structure as shown in a formula 1 and / or a compound with a structure as shown in a formula 2. The electrolyte provided by the invention can reduce the self-discharge of the battery and improve the cycle performance and rate capability of the battery.

Description

Technical Field

[0001] This invention relates to an electrolyte, and more particularly to an electrolyte, a battery, a battery pack, and an electrical device, belonging to the field of ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage due to their high energy density and cycle performance. However, rising lithium salt prices have limited the development of lithium-ion batteries due to limited lithium resources. Sodium, an element in the same group as lithium, has very similar physical and chemical properties. Moreover, sodium is more abundant on Earth than lithium and has a lower cost, making the development of sodium-ion batteries a better choice for large-scale energy storage devices.

[0003] Currently, research on sodium-ion battery technology has attracted widespread attention in both academic and industrial fields. However, sodium-ion batteries still face some problems and challenges in practical applications, such as self-discharge, short cycle life, and poor rate performance.

[0004] Therefore, those skilled in the art urgently need to develop an electrolyte that can improve the self-discharge, cycle performance, and rate performance of batteries. Summary of the Invention

[0005] This invention provides an electrolyte that can reduce battery self-discharge and improve battery cycle performance and rate performance.

[0006] The present invention provides a battery that is prepared based on the above-mentioned electrolyte and has low self-discharge, high cycle performance and high rate performance.

[0007] This invention provides a battery pack with low self-discharge, high cycle performance, and high rate performance.

[0008] This invention provides an electrical device with low self-discharge, long cycle life, and high rate performance, which is beneficial for use in various scenarios.

[0009] This invention provides an electrolyte comprising sulfone compounds, nitrile compounds, and ether compounds, wherein the sulfone compounds include compounds having the structure shown in Formula 1 and / or compounds having the structure shown in Formula 2.

[0010]

[0011] In Formula 1, R1 and R2 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms.

[0012]

[0013] In Formula 2, R3 and R4 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms.

[0014] The electrolyte as described above, wherein the compound having the structure shown in Formula 1 includes one or more of dimethyl sulfoxide, ethyl methyl sulfoxide, and 2,2-difluoroethyl methyl sulfoxide; and the compound having the structure shown in Formula 2 includes one or more of ethyl methyl sulfone, ethyl isopropyl sulfone, trifluoromethyl ethyl sulfone, ethyl vinyl sulfone, and divinyl sulfone.

[0015] In the electrolyte as described above, the nitrile compound includes one or more of acetonitrile, succinic anion, 1,3,6-hexanetrionitrile, propionitrile, formonitrile, and acrylonitrile.

[0016] In the electrolyte described above, the ether compound includes one or more of methyl ether, dimethyl ether, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, methyl ethyl ether, and 4-methyl-1,3-dioxolane.

[0017] In the electrolyte as described above, the total mass percentage of the sulfone compound, the nitrile compound, and the ether compound in the electrolyte is 1% to 20%.

[0018] In the electrolyte as described above, the mass percentage of the sulfone compound in the electrolyte is 0.1% to 10%.

[0019] In the electrolyte as described above, the mass percentage of the nitrile compound in the electrolyte is 0.5% to 9%.

[0020] In the electrolyte as described above, the mass percentage of the ether compound in the electrolyte is 0.5% to 5%.

[0021] The electrolyte as described above further includes an organic solvent, wherein the organic solvent includes carbonates, and the carbonates include one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate; and / or, the mass percentage of the organic solvent in the electrolyte is 20% to 99%.

[0022] The electrolyte as described above, wherein the electrolyte comprises a sodium salt, and the concentration of the sodium salt in the electrolyte is 0.5 mol / L to 2.5 mol / L.

[0023] The electrolyte as described above, wherein the electrolyte comprises a sodium salt, the sodium salt comprising one or more of sodium hexafluorophosphate, sodium hexafluoroborate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, and sodium bis(fluorosulfonyl)imide.

[0024] The electrolyte as described above, wherein the electrolyte includes silicon-based additives.

[0025] The present invention also provides a battery comprising the electrolyte as described above.

[0026] The present invention also provides a battery pack, wherein the battery described above is included.

[0027] The present invention also provides an electrical device, wherein the device includes a battery as described above or a battery pack as described above.

[0028] The electrolyte, battery, battery pack, and electrical device provided by this invention include sulfone compounds, nitrile compounds, and ether compounds in the electrolyte system. In this electrolyte system, the sulfone compounds help promote sodium salt dissociation and have lower viscosity, thus improving the ionic conductivity of the electrolyte. Simultaneously, the sulfone compounds can participate in the formation of a more stable CEI film, reducing electrolyte decomposition and thereby reducing battery self-discharge and improving battery cycle performance and rate performance. The cyano groups in the nitrile compounds have strong coordination ability and can combine with transition metal cations on the positive electrode surface, inhibiting the decomposition of the electrolyte by the positive electrode and improving battery cycle performance. The ether compounds help improve the kinetic performance of sodium-ion batteries, and the SEI film formed has a richer inorganic component, improving its stability and helping to improve the self-discharge performance of batteries (such as sodium-ion batteries). Furthermore, they can reduce battery impedance and facilitate the migration of active ions such as sodium ions, thereby improving battery cycle performance and rate performance. By synergistically combining sulfone compounds, nitrile compounds, and ether compounds, the battery generates more stable SEI and CEI films, thereby reducing the contact between the positive and negative electrodes and the electrolyte, effectively suppressing positive electrode decomposition and electrolyte consumption, and reducing battery impedance, thus improving the battery's self-discharge performance, cycle performance, and rate performance. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention provides an electrolyte comprising sulfone compounds, nitrile compounds, and ether compounds, wherein the sulfone compounds include compounds having the structure shown in Formula 1 and / or compounds having the structure shown in Formula 2:

[0031]

[0032] In Formula 1, R1 and R2 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms.

[0033]

[0034] In Formula 2, R3 and R4 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms.

[0035] According to the above-described solution provided by the present invention, when this electrolyte is applied to a battery, the battery exhibits low self-discharge, high cycle performance, and high rate performance. The inventors analyzed the principle behind this and believe the reasons may be as follows: Firstly, sulfone compounds have a high dielectric constant, and as electrolyte additives in sodium-ion batteries, they help promote the dissociation of sodium salts, increasing the ionic conductivity of the electrolyte. Furthermore, compared to cyclic sulfone compounds, the sulfone compounds provided by the present invention typically have lower viscosity, which helps improve the ionic conductivity of the electrolyte. Simultaneously, sulfone compounds can participate in the formation of a more stable CEI film, covering the positive electrode surface and reducing electrolyte decomposition, thereby reducing battery self-discharge and improving battery cycle performance and rate performance; Secondly... The cyano group in nitrile compounds has a strong coordinating ability and can bind to transition metal cations on the positive electrode surface. This binding can prevent the transition metal cations from contacting the electrolyte, thereby inhibiting the decomposition of the electrolyte by the positive electrode and improving the cycle performance of the battery. In addition, ether compounds help improve the kinetic performance of sodium-ion batteries. The SEI film formed has a richer inorganic component, which improves the stability of the SEI film, helps improve the self-discharge performance of sodium-ion batteries, and can reduce battery impedance, which is more conducive to sodium ion migration, thereby improving the cycle performance and rate performance of the battery. In the embodiments of the present invention, sulfone compounds, nitrile compounds, and ether compounds work synergistically to generate more stable SEI and CEI films, thereby reducing the contact between the positive and negative electrodes and the electrolyte, effectively inhibiting positive electrode decomposition and electrolyte consumption, and reducing battery impedance, thereby improving the self-discharge performance, cycle performance, and rate performance of the battery.

[0036] In this embodiment of the invention, halogen atoms refer to halogen atoms such as -F, -Cl, -Br, and I.

[0037] In this embodiment of the invention, the substituted or unsubstituted C1-C5 hydrocarbon group refers to an alkyl group with 1-5 carbon atoms that has a substituent or unsubstituted carbon atom, or a cycloalkyl group with 3-5 carbon atoms that has a substituent or unsubstituted carbon atom, or an alkenyl group with 2-5 carbon atoms that has a substituent or unsubstituted carbon atom, or an alkyne group with 2-5 carbon atoms that has a substituent or unsubstituted carbon atom, or an alkyne group with 2-5 carbon atoms that has a substituent or unsubstituted carbon atom; wherein, the alkyl group can be an unbranched straight-chain alkyl group or a branched isoalkyl group, the alkenyl group can be an unbranched straight-chain alkenyl group or a branched isoalkynyl group, and the alkyne group can be an unbranched straight-chain alkyne group or a branched isoalkynyl group; exemplaryly, the number of carbon atoms in the C1-C5 hydrocarbon group can be 1, 2, 3, 4 or 5.

[0038] In this embodiment of the invention, the substituents of the C1-C5 hydrocarbon groups may include halogen atoms.

[0039] In this embodiment of the invention, the type and position of the substituent are not limited, and can be selected according to actual needs.

[0040] For example, R1, R2, R3, and R4 are each independently selected from -H, -F, -Cl, -Br, -I, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH(CH3)2, -C(CH3)3, -CH=CH2, -C≡CH, -CH2CH=CH2, -CH2C≡CH, -CH2CH2CF3, -CH2CF2CF3, -CF2CF2CF3, etc.

[0041] The nitrile compounds in this embodiment refer to compounds comprising a hydrocarbon group and a cyano group. Preferably, the nitrile compounds comprise alkyl and cyano groups.

[0042] The embodiments of the present invention do not limit the substitution position of the cyano group on the hydrocarbon group, and can be selected according to actual needs.

[0043] This invention does not limit the number of cyano groups in nitrile compounds; the number can be selected according to actual needs.

[0044] This invention does not limit whether the nitrile compounds include other substituents; these can be selected according to actual needs.

[0045] In one specific embodiment, the nitrile compound includes one or more of acetonitrile, succinic anionyl nitrile, 1,3,6-hexanetrionitrile, propionitrile, formonitrile, and acrylonitrile. When the above-mentioned compounds are selected as nitrile compounds in the embodiments of the present invention, the nitrile compounds can exhibit better synergistic effects with sulfone compounds and ether compounds, and the nitrile compounds can better recombine with transition metal cations on the positive electrode surface, thus minimizing electrolyte decomposition and resulting in better battery cycle performance. Preferably, the nitrile compound includes acetonitrile.

[0046] The ether compounds in this embodiment of the invention refer to compounds comprising hydrocarbon groups and ether groups. Preferably, the ether compounds comprise alkyl groups and ether groups.

[0047] The embodiments of the present invention do not limit the connection relationship between the ether group and the hydrocarbon group, and can be selected according to actual needs.

[0048] This invention does not limit whether the ether compounds include other substituents; these can be selected according to actual needs.

[0049] In one specific embodiment, the ether compound includes one or more of methyl ether, dimethyl ether, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, methyl ethyl ether, and 4-methyl-1,3-dioxolane. When the above-mentioned compounds are selected as ether compounds in the embodiments of the present invention, the ether compounds can achieve better synergistic effects with sulfone compounds and nitrile compounds, and the ether compounds can improve the kinetic performance of the battery to a greater extent, reduce battery impedance, and simultaneously contribute to the higher stability of the SEI film produced, thus helping to improve the battery's cycle performance, rate performance, and self-discharge performance. Preferably, the ether compound includes diethylene glycol dimethyl ether.

[0050] In one specific embodiment, the compound having the structure shown in Formula 1 includes one or more of dimethyl sulfoxide, ethyl methyl sulfoxide, and 2,2-difluoroethyl methyl sulfoxide;

[0051] In one specific embodiment, the compound having the structure shown in Formula 2 includes one or more of ethyl methyl sulfone, ethyl isopropyl sulfone, trifluoromethyl ethyl sulfone, ethyl vinyl sulfone, and divinyl sulfone.

[0052] When the above-mentioned compounds are selected as sulfone compounds in the embodiments of the present invention, sulfone compounds can achieve better synergistic effects with nitrile compounds and ether compounds. Furthermore, sulfone compounds have higher dielectric constants, resulting in faster dissociation of sodium salts and further improving the ionic conductivity of the electrolyte. Simultaneously, the CEI film formed with the participation of sulfone compounds exhibits higher stability, providing better protection for the positive electrode and electrolyte, thereby resulting in superior cycle performance and rate performance of the battery. Preferably, the sulfone compounds include ethyl isopropyl sulfone and trifluoromethyl ethyl sulfone.

[0053] In one specific embodiment, the total mass percentage of sulfone compounds, nitrile compounds, and ether compounds in the electrolyte (i.e., the ratio of the sum of the masses of sulfone compounds, nitrile compounds, and ether compounds to the total mass of the electrolyte) is 1% to 20%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, etc. When the total mass percentage of sulfone compounds, nitrile compounds, and ether compounds is within the above range, the battery impedance is lower, and the stability of the SEI film and CEI film is higher. This better reduces the contact between the positive and negative electrodes and the electrolyte, effectively suppressing positive electrode decomposition and electrolyte consumption, thereby giving the battery superior self-discharge performance, cycle performance, and rate performance.

[0054] In one specific embodiment, the mass percentage of sulfone compounds in the electrolyte is 0.1% to 10%, for example, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. When the mass percentage of sulfone compounds is within the above range, the synergistic effect of sulfone compounds with nitrile compounds and ether compounds is better, which can further improve the ionic conductivity of the electrolyte. At the same time, the CEI film formed by sulfone compounds has higher stability, which can better protect the positive electrode and the electrolyte. It can also avoid excessive electrolyte viscosity and increased battery internal resistance caused by excessive sulfone compounds, thereby resulting in better cycle performance and rate performance of the battery.

[0055] In one specific embodiment, the mass percentage of nitrile compounds in the electrolyte is 0.5% to 9%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%. When the mass percentage of nitrile compounds is within the above range, the nitrile compounds can exert better synergistic effects with sulfone compounds and ether compounds, and an appropriate amount of nitrile compounds can recombine with transition metal cations on the positive electrode surface, reducing electrolyte decomposition and avoiding unnecessary reduction and decomposition of excessive nitrile compounds at the negative electrode, thereby resulting in better battery cycle performance.

[0056] In one specific embodiment, the mass percentage of ether compounds in the electrolyte is 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. When the mass percentage of ether compounds is within the above range, the ether compounds can exert a better synergistic effect with sulfone compounds and nitrile compounds. Sufficient amounts of ether compounds help improve the kinetic performance of the battery, reduce battery impedance, and enhance the stability of the SEI film. Furthermore, it can prevent the oxidative decomposition of excessive ether additives under high voltage, thereby resulting in better cycle performance, rate performance, and self-discharge performance of the battery.

[0057] In one specific embodiment, the electrolyte further includes an organic solvent, which includes carbonates, specifically one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate. When the organic solvent is selected from the above-mentioned solvents, the electrolyte exhibits high stability, and sodium salts, sulfones, nitrile compounds, and ethers can be fully dissolved, resulting in an electrolyte with high conductivity. Simultaneously, the electrolyte viscosity is suitable, allowing the sodium salts, sulfones, nitrile compounds, and ethers to better exert their functions, leading to superior cycle performance, rate performance, and self-discharge performance of the battery. Comparatively, when the organic solvent includes diethyl carbonate and propylene carbonate, it is more conducive to compatibility with electrolyte components such as sulfones, nitrile compounds, and ethers, further improving the battery's cycle performance, rate performance, and self-discharge performance.

[0058] In one specific embodiment, the mass percentage of organic solvent in the electrolyte is 20% to 99%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99%.

[0059] Specifically, when the electrolyte includes multiple organic solvents, the mass percentage of each organic solvent can be 20% to 99%, for example, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 99%. Preferably, the mass percentage of each organic solvent is 30% to 95%.

[0060] In some embodiments, the organic solvent includes diethyl carbonate and propylene carbonate, wherein the mass ratio of diethyl carbonate to the sum of the masses of diethyl carbonate and propylene carbonate can be 30% to 80%, for example, 30%, 40%, 50%, 60%, 70%, or 80%, and correspondingly, the mass ratio of propylene carbonate to the sum of the masses of diethyl carbonate and propylene carbonate is 20% to 70%. For example, the mass ratio of diethyl carbonate to propylene carbonate can be 4:6.

[0061] In one specific embodiment, the electrolyte includes a sodium salt, and the concentration of the sodium salt in the electrolyte is from 0.5 mol / L to 2.5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L. When the concentration of the sodium salt is within the above range, the sodium salt can fully dissociate in the electrolyte, resulting in high ionic conductivity of the electrolyte, thereby improving the cycle performance of the battery. For example, the concentration of the sodium salt in the electrolyte is 1 mol / L.

[0062] In one specific embodiment, the electrolyte comprises a sodium salt, including one or more of sodium hexafluorophosphate, sodium hexafluoroborate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, and sodium bis(fluorosulfonyl)imide. When the sodium salt is selected from the above compounds, it can fully exert its function to prepare an electrolyte with high ionic conductivity and high stability, thereby enabling the sodium-ion battery to fully exert its electrochemical performance and improve the battery's cycle life, rate performance, and self-discharge performance. Preferably, the sodium salt comprises sodium hexafluorophosphate.

[0063] In one specific embodiment, the electrolyte includes a silicon-based additive. The silicon-based additive in this embodiment includes siloxane groups or silanium-nitrogen groups.

[0064] The embodiments of the present invention do not limit the connection relationship between the siloxy group or the silicon nitrogen group and other groups, and can be selected according to actual needs.

[0065] This invention does not limit the specific selection of other substituents in silicon-based additives; they can be selected according to actual needs.

[0066] In some embodiments, the silicon-based additive may include one or more of vinyltrimethoxysilane, dimethyldimethoxysilane, propoxytrimethylsilane, tetramethoxysilane, etc. Preferably, the silicon-based additive may include vinyltrimethoxysilane.

[0067] The electrolyte in this embodiment of the invention also includes silicon-based additives, which can further improve the stability of the cathode / electrolyte interface, thereby avoiding cathode decomposition or electrolyte consumption to a greater extent, and thus improving the cycle life, rate performance and self-discharge performance of the battery.

[0068] This invention provides a battery comprising the electrolyte described above. This battery exhibits excellent cycle performance, rate performance, and self-discharge performance.

[0069] In one embodiment, the battery includes a positive electrode sheet, which includes a positive electrode active material, and the positive electrode active material includes a layered sodium oxide-based material.

[0070] Generally, a positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer includes a positive active substance (or positive active material), a conductive agent, and a binder. The positive current collector generally includes aluminum foil.

[0071] The embodiments of the present invention do not specifically limit the layered oxide sodium-based materials. In some embodiments, the general formula of the layered oxide sodium-based material is Na. y M x O2, wherein M can be selected from one or more of Ni, Cu, Fe, Mn, Co, Zn, Ti, and Ca, and layered oxide sodium-based materials include, for example, NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2(NNFM), NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NNCM), NaCu 1 / 3Fe 1 / 3 Mn 1 / 3 O2 (NCFM) and P2-Na 2 / 3 Ni 1 / 3 Mn 2 / 3 One or more of O2 (P2-NNMO) can be used as the positive electrode active material. When the positive electrode active material is selected from the above-mentioned positive electrode materials, it is beneficial to further improve the discharge specific capacity of the battery.

[0072] In one specific embodiment, the battery includes a negative electrode sheet, which includes a negative electrode active material, comprising one or more of graphite, mesophase carbon microspheres, and silicon-carbon materials. The negative electrode sheet of this embodiment includes a negative electrode current collector and a layer of negative electrode active material disposed on the surface of the current collector. The negative electrode active material layer includes a negative electrode active material (or negative electrode active material), a conductive agent, and a binder. The negative electrode current collector generally includes copper foil.

[0073] In the embodiments of the present invention, the conductive agent and binder in the positive electrode active material layer and the negative electrode active material layer can be conventional materials in the art.

[0074] The lithium-ion battery of this invention also includes a separator. The separator is a separator known in the art that can be used in batteries and is stable to the electrolyte used. It may include one or more of polyolefins, aromatic polyamides, polytetrafluoroethylene, and polyethersulfone, and may be configured as needed.

[0075] This invention also provides a battery pack including the battery described above. This battery pack has advantages corresponding to the electrolyte described above, which will not be elaborated further.

[0076] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0077] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the electrolyte described above, which will not be elaborated further.

[0078] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations.

[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0080] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0081] Example 1

[0082] The battery preparation method of this embodiment includes the following steps:

[0083] 1. Electrolyte preparation: Prepare the electrolyte in a glove box filled with 99.999% pure argon gas. Maintain the moisture content in the glove box at ≤0.1ppm and the temperature at room temperature. Mix diethyl carbonate (DEC) and propylene carbonate (PC) in a mass ratio of 2:3 until homogeneous. Add ethyl isopropyl sulfone (EiPS), acetonitrile (ACN), and diethylene glycol dimethyl ether (DEDM) according to their mass percentages. Finally, add sodium hexafluorophosphate (NaPF6) according to its molar concentration and dissolve it completely to obtain the electrolyte.

[0084] The electrolyte contains 7% EiPS by mass, 3% ACN by mass, 2% DEDM by mass, and 1 mol / L NaPF6 by mass.

[0085] 2. Preparation of the positive electrode: The positive electrode active material is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, conductive agent SP, and polyvinylidene fluoride (PVDF) were mixed evenly in a mass ratio of 8:1:1. NMP was added at a mass ratio of PVDF:N-methylpyrrolidone (NMP) of 1:50 and stirred until homogeneous. The resulting paste was evenly coated onto aluminum foil, which would serve as the positive electrode current collector. The paste was then dried in a vacuum oven at 60°C for 12 hours to obtain the positive electrode sheet. The weight was recorded, and the mass of the active material was calculated. 总 -m 铝箔 (*0.8), the diameter of the positive electrode is 12mm.

[0086] 3. Preparation of the negative electrode: Sodium carboxymethyl cellulose (CMC) was dissolved in deionized water to prepare an emulsion with a solid content of 2% wt. Hard carbon, conductive agent SP, CMC, and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 90:5:2:3. The resulting slurry was evenly coated onto aluminum foil and placed in a vacuum drying oven. It was baked at 60℃ for 12 hours. After cutting, the negative electrode was obtained. The weight was recorded, and the mass of the active material was calculated. 总 -m 铝箔 (*0.9), the diameter of the negative electrode is 14mm.

[0087] 4. Assemble the CR2032 button cell in the following order: negative electrode shell - negative electrode sheet - electrolyte - glass fiber separator - electrolyte - positive electrode - gasket - spring sheet - positive electrode shell.

[0088] Example 2

[0089] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 3%, the mass percentage of ACN is 3%, and the mass percentage of DEDM is 2%.

[0090] Example 3

[0091] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 9%, the mass percentage of ACN is 3%, and the mass percentage of DEDM is 2%.

[0092] Example 4

[0093] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 7%, the mass percentage of ACN is 1%, and the mass percentage of DEDM is 2%.

[0094] Example 5

[0095] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 7%, the mass percentage of ACN is 7%, and the mass percentage of DEDM is 2%.

[0096] Example 6

[0097] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 7%, the mass percentage of ACN is 3%, and the mass percentage of DEDM is 1%.

[0098] Example 7

[0099] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 7%, the mass percentage of ACN is 3%, and the mass percentage of DEDM is 4%.

[0100] Example 8

[0101] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 7%, the mass percentage of ACN is 7%, and the mass percentage of DEDM is 4%.

[0102] Example 9

[0103] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 0.1%.

[0104] Example 10

[0105] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 10%.

[0106] Example 11

[0107] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 0.05%.

[0108] Example 12

[0109] The difference between this embodiment and Embodiment 1 is that the mass percentage of EiPS is 15%.

[0110] Example 13

[0111] The difference between this embodiment and Embodiment 1 is that the mass percentage of ACN is 0.5%.

[0112] Example 14

[0113] The difference between this embodiment and Embodiment 1 is that the mass percentage of ACN is 9%.

[0114] Example 15

[0115] The difference between this embodiment and Embodiment 1 is that the mass percentage of ACN is 0.1%.

[0116] Example 16

[0117] The difference between this embodiment and Embodiment 1 is that the mass percentage of ACN is 11%.

[0118] Example 17

[0119] The difference between this embodiment and Embodiment 1 is that the mass percentage of DEDM is 0.5%.

[0120] Example 18

[0121] The difference between this embodiment and Embodiment 1 is that the mass percentage of DEDM is 5%.

[0122] Example 19

[0123] The difference between this embodiment and Embodiment 1 is that the mass percentage of DEDM is 0.1%.

[0124] Example 20

[0125] The difference between this embodiment and Embodiment 1 is that the mass percentage of DEDM is 10%.

[0126] Example 21

[0127] The difference between this embodiment and Embodiment 1 is that the electrolyte also includes vinyltrimethoxysilane, and the mass percentage of vinyltrimethoxysilane is 6%.

[0128] Example 22

[0129] The difference between this embodiment and Embodiment 1 is that EiPS is replaced with trifluoromethyl ethyl sulfone (FMES).

[0130] Example 23

[0131] The difference between this embodiment and Embodiment 1 is that EiPS is replaced with dimethyl sulfoxide.

[0132] Example 24

[0133] The difference between this embodiment and Embodiment 1 is that ACN is replaced with succinic acid.

[0134] Example 25

[0135] The difference between this embodiment and Embodiment 1 is that ACN is replaced with 1,3,6-hexanetrionitrile.

[0136] Example 26

[0137] The difference between this embodiment and Embodiment 1 is that DEDM is replaced with ethylene diether.

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 1 is that EiPS, ACN, and DEDM are not added to the electrolyte.

[0140] Comparative Example 2

[0141] The difference between this comparative example and Example 1 is that no ACN or DEDM is added to the electrolyte, and the mass percentage of EiPS is 7%.

[0142] Comparative Example 3

[0143] The difference between this comparative example and Example 1 is that EiPS, ACN, and DEDM are not added to the electrolyte, and the mass percentage of trifluoromethyl ethyl sulfone (FMES) is 7%.

[0144] Comparative Example 4

[0145] The difference between this comparative example and Example 1 is that EiPS and DEDM are not added to the electrolyte, and the mass percentage of ACN is 3%.

[0146] Comparative Example 5

[0147] The difference between this comparative example and Example 1 is that EiPS and ACN are not added to the electrolyte, and the mass percentage of DEDM is 2%.

[0148] Comparative Example 6

[0149] The difference between this comparative example and Example 1 is that DEDM is not added to the electrolyte, the mass percentage of EiPS is 7%, and the mass percentage of ACN is 3%.

[0150] Comparative Example 7

[0151] The difference between this comparative example and Example 1 is that DEDM is not added to the electrolyte, the mass percentage of EiPS is 3%, and the mass percentage of ACN is 3%.

[0152] Comparative Example 8

[0153] The difference between this comparative example and Example 1 is that DEDM is not added to the electrolyte, the mass percentage of EiPS is 9%, and the mass percentage of ACN is 3%.

[0154] Comparative Example 9

[0155] The difference between this comparative example and Example 1 is that EiPS and DEDM are not added to the electrolyte, and the electrolyte includes trifluoromethyl ethyl sulfone and ACN, with the mass percentage of trifluoromethyl ethyl sulfone being 7% and the mass percentage of ACN being 3%.

[0156] Comparative Example 10

[0157] The difference between this comparative example and Example 1 is that EiPS and DEDM are not added to the electrolyte, and the electrolyte includes trifluoromethyl ethyl sulfone and ACN, with a mass percentage of 3% for trifluoromethyl ethyl sulfone and 3% for ACN.

[0158] Comparative Example 11

[0159] The difference between this comparative example and Example 1 is that EiPS and DEDM are not added to the electrolyte, and the electrolyte includes trifluoromethyl ethyl sulfone and ACN, with the mass percentage of trifluoromethyl ethyl sulfone being 9% and the mass percentage of ACN being 3%.

[0160] Comparative Example 12

[0161] The difference between this comparative example and Example 1 is that no ACN is added to the electrolyte, and the electrolyte includes EiPS and DEDM, with EiPS accounting for 7% by mass and DEDM accounting for 2% by mass.

[0162] Table 1

[0163]

[0164] Test case

[0165] Self-discharge test: First, the button cell is converted to capacity at 0.1C with a voltage range of 1.5-4V. Then, it is cycled at 0.2C for 3 cycles to fix the capacity. After standing for 21 days, it is discharged to 1.5V to test the remaining capacity. Then, it is charged at 0.2C to restore the capacity and the capacity recovery rate is calculated.

[0166] Rate performance testing: The coin cells were subjected to cycle tests at different rates. First, they were converted to capacity at 0.1C with a voltage range of 1.5-4V, and then fixed at 0.2C for 3 cycles. After 200 cycles at 0.5C, 1C, and 3C respectively, the capacity retention rate after 200 cycles at each rate was measured.

[0167] Table 2

[0168]

[0169]

[0170] As can be seen from Table 2, compared with Comparative Examples 1 to 12, Examples 1 to 26, by simultaneously introducing nitrile compounds, ether compounds, and sulfone compounds having the structure shown in Formula 1 and / or the structure shown in Formula 2 into the electrolyte system, the components work synergistically. For example, sulfones can improve the cycle stability of the battery, ether compounds can improve the self-discharge performance and high-rate cycle stability of the battery, and nitrile and sulfone compounds work synergistically to improve the cycle stability of the battery, thereby improving the self-discharge performance, rate performance, and cycle performance of the battery.

[0171] Further, as can be seen from Examples 1 to 20, Examples 1 to 10, 13, 14, 17 and 18, by further controlling at least one of the following in the electrolyte: sulfone compounds at 0.1% to 10%, nitriles at 0.5% to 9%, and ethers at 0.5% to 5%, are beneficial to further improve the battery's self-discharge performance, rate performance and cycle performance.

[0172] As can be seen from Examples 1 and 21, Example 21, by further introducing additives into the electrolyte, helps to further improve the battery's self-discharge performance, rate performance, and cycle performance.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that, This includes sulfone compounds, nitrile compounds, and ether compounds, wherein the sulfone compounds include compounds having the structure shown in Formula 1 and / or compounds having the structure shown in Formula 2: In Formula 1, R1 and R2 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms. In Formula 2, R3 and R4 are each independently selected from hydrogen atoms, halogen atoms, substituted or unsubstituted C1-C5 hydrocarbon groups; wherein, when the C1-C5 hydrocarbon group has substituents, the substituents of the C1-C5 hydrocarbon group include halogen atoms.

2. The electrolyte according to claim 1, characterized in that, The compound having the structure shown in Formula 1 includes one or more of dimethyl sulfoxide, ethyl methyl sulfoxide, and 2,2-difluoroethyl methyl sulfoxide; The compounds having the structure shown in Formula 2 include one or more of ethyl methyl sulfone, ethyl isopropyl sulfone, trifluoromethyl ethyl sulfone, ethyl vinyl sulfone, and divinyl sulfone.

3. The electrolyte according to claim 1, characterized in that, The nitrile compounds include one or more of acetonitrile, butadienenitrile, 1,3,6-hexanetrionitrile, propionitrile, formonitrile, and acrylonitrile.

4. The electrolyte according to claim 1, characterized in that, The ether compounds include one or more of methyl ether, dimethyl ether, diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, methyl ethyl ether, and 4-methyl-1,3-dioxolane.

5. The electrolyte according to any one of claims 1-4, characterized in that, The total mass percentage of the sulfone compounds, nitrile compounds, and ether compounds in the electrolyte is 1% to 20%.

6. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte contains 0.1% to 10% by mass of the sulfone compound.

7. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte contains 0.5% to 9% by mass of the nitrile compound.

8. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte contains 0.5% to 5% by mass of the ether compound.

9. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte also includes an organic solvent, wherein... The organic solvent includes carbonates, which include one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate. And / or, the organic solvent in the electrolyte has a mass percentage content of 20% to 99%.

10. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte includes a sodium salt, and the concentration of the sodium salt in the electrolyte is 0.5 mol / L to 2.5 mol / L.

11. The electrolyte according to claim 10, characterized in that, The electrolyte comprises a sodium salt, which includes one or more of sodium hexafluorophosphate, sodium hexafluoroborate, sodium perchlorate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, and sodium bis(fluorosulfonyl)imide.

12. The electrolyte according to any one of claims 1-4, characterized in that, The electrolyte includes silicon-based additives.

13. A battery, characterized in that, Includes the electrolyte according to any one of claims 1-12.

14. A battery pack, characterized in that, Includes the battery as described in claim 13.

15. An electrical appliance, characterized in that, Includes the battery of claim 13 or the battery pack of claim 14.

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