Electrolyte, battery, battery device and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery device and electric equipment, the electrolyte comprises a first additive, the first additive comprises a cyano boric acid ester compound, the cyano boric acid ester compound has a benzene ring and a cyano group and a boric acid ester group which are located on the benzene ring, and the cyano group is located at the ortho position of the boric acid ester group. According to the electrolyte provided by the invention, the cycle performance of the battery can be improved, the impedance of the battery is reduced, and the ion precipitation phenomenon is relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to an electrolyte, a battery, a battery device and an electrical device. Background Art

[0002] Secondary batteries, also known as rechargeable batteries, are core components of modern portable electronic devices, electric vehicles, and energy storage systems. They can store and release electrical energy through reversible chemical reactions, offering significant advantages in energy efficiency and environmental friendliness. As a key material in secondary batteries, the electrolyte performs ion conduction and plays a crucial role in the battery's electrochemical performance, cycle life, and safety.

[0003] However, when used in secondary batteries, existing electrolytes still suffer from high impedance, severe ion leaching, and poor cycling performance. Therefore, developing new electrolyte materials with low impedance, reduced ion leaching, and excellent cycling performance has become a key area of ​​development for secondary battery technology. Summary of the Invention

[0004] The main purpose of the present invention is to provide an electrolyte, which, when applied to a battery, can reduce the impedance of the battery, alleviate ion precipitation, and improve the cycle performance of the battery.

[0005] The present invention also provides a battery comprising the above electrolyte, so that the battery has low impedance, alleviated ion precipitation phenomenon, and excellent cycle performance.

[0006] The present invention also provides a battery device comprising a plurality of the above batteries. Therefore, the battery device has low impedance, alleviated ion precipitation, and excellent cycle performance.

[0007] The present invention also provides an electrical device comprising the above-mentioned battery. Therefore, the performance of the battery associated with the electrical device is relatively excellent.

[0008] In a first aspect, the present invention provides an electrolyte comprising a first additive, wherein the first additive comprises a cyanoborate compound, wherein the cyanoborate compound has a benzene ring and a cyano group and a borate group located on the benzene ring, wherein the cyano group is located at an ortho position to the borate group.

[0009] In the electrolyte described above, the cyanoborate compound includes a compound having a structure shown in Formula 1 and / or a compound having a structure shown in Formula 2;

[0010]

[0011] Among them, R1~R 10Each is independently selected from hydrogen, halogen, cyano, straight-chain or branched alkyl having 1 to 20 carbon atoms, straight-chain or branched alkenyl having 2 to 20 carbon atoms, and straight-chain or branched alkynyl having 2 to 20 carbon atoms.

[0012] In the electrolyte as described above, the cyanoborate compound includes the compound having the structure shown in Formula 1, and the compound having the structure shown in Formula 1 has at least one fluorine-containing functional group.

[0013] In the electrolyte described above, the compound having the structure shown in Formula 1 includes at least one of the structure shown in Formula 1-1, the structure shown in Formula 1-2, the structure shown in Formula 1-3, and the structure shown in Formula 1-4:

[0014]

[0015]

[0016] In the electrolyte as described above, the cyanoborate compound includes the compound having the structure shown in Formula 2, and the compound having the structure shown in Formula 2 has at least one fluorine-containing functional group.

[0017] In the electrolyte described above, the compound having the structure shown in Formula 2 includes at least one of the structure shown in Formula 2-1, the structure shown in Formula 2-2, the structure shown in Formula 2-3, and the structure shown in Formula 2-4:

[0018]

[0019] In the electrolyte as described above, the mass percentage of the first additive in the electrolyte is 0.05% to 3%.

[0020] In the electrolyte as described above, the first additive accounts for 0.5% to 2% by mass of the electrolyte.

[0021] The electrolyte as described above further includes a second additive, which includes at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, vinyl ethylene carbonate, vinyl sulfate, methylene dicarbonate, tris(trimethylsilyl)phosphate, succinic anhydride, and maleic anhydride.

[0022] In the electrolyte as described above, the mass percentage of the second additive in the electrolyte is 0.05% to 10%.

[0023] In the electrolyte as described above, the mass percentage of the second additive in the electrolyte is 0.5% to 6%.

[0024] The electrolyte as described above, further comprising an electrolyte salt;

[0025] The electrolyte salt includes at least one of borate, imide salt, hexafluorophosphate, and perchlorate;

[0026] And / or, the concentration of the electrolyte salt in the electrolyte solution is 0.3 mol / L to 3 mol / L.

[0027] In the electrolyte solution described above, the concentration of the electrolyte salt in the electrolyte solution is 0.8 mol / L to 1.2 mol / L.

[0028] In a second aspect, the present invention provides a battery comprising the electrolyte as described above.

[0029] The battery as described above comprises a sodium ion battery.

[0030] In a third aspect, the present invention provides a battery device comprising a plurality of batteries as described above.

[0031] In a fourth aspect, the present invention provides an electrical device comprising the electrolyte as described above, or the battery as described above, or the battery device as described above.

[0032] The electrolyte provided by the present invention comprises a first additive including a cyanoborate compound, and the cyanoborate compound has a cyano group and a borate group located on a benzene ring, the cyano group and the borate group are in ortho positions on the benzene ring, the cyano group can complex transition metals to prevent the transition metal on the positive electrode side from migrating to the negative electrode, the presence of the benzene ring can increase the solubility of the cyano group, and the borate group can form a stable solid electrolyte interface (SEI) film on the positive and negative electrodes of the battery. Since the hydrogen atoms in the ortho position have higher activity after substitution on the benzene ring, the cyano group is located in the ortho position of the borate group, which makes it easier to promote the occurrence of interfacial reactions, thereby accelerating and optimizing the formation process of the SEI film, reducing the irreversible consumption of the electrolyte, maintaining the stability of the electrolyte, and being able to effectively reduce the charge transfer impedance and improve the conductivity of ions between the electrode and the electrolyte, thereby improving the cycle performance of the battery, reducing the impedance of the battery, and alleviating the ion precipitation phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0034] Figure 1 This is a SEM image of the negative electrode sheet in the battery prepared with the electrolyte of Example 1;

[0035] Figure 2 This is the SEM image of the negative electrode in the battery prepared with the electrolyte of Comparative Example 1. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0037] With the rapid development of the electric vehicle industry, lithium-ion batteries, the primary power source, face challenges with scarce and unevenly distributed lithium resources. Sodium-ion batteries, however, have attracted significant attention due to their high sodium abundance and low cost. While similar to lithium-ion batteries in terms of material selection and electrochemical performance, sodium-ion batteries also face unique technical challenges.

[0038] Electrolyte is one of the key materials of sodium-ion batteries and has an important impact on the cycle performance and safety of the battery. Sodium-ion batteries usually use hard carbon as the negative electrode material. However, there are many defects on the surface of negative electrode materials such as hard carbon materials, which leads to more side reactions between the electrolyte and the negative electrode surface. These side reactions not only lead to irreversible consumption of the electrolyte, but also form a thicker negative electrode surface passivation film, namely SEI film, which increases the battery impedance and ion precipitation (such as sodium precipitation in sodium-ion batteries). In this case, the safety and electrochemical performance of the battery will be significantly affected. In addition, excessive consumption of the electrolyte may also cause the battery to experience rapid capacity decay during the cycle.

[0039] The inventors of the present application have discovered through research that by adding cyanoborate additives to the electrolyte, the impedance of the battery can be significantly reduced, the ion precipitation phenomenon can be alleviated, and the cycle performance of the battery can be improved.

[0040] Based on this, in a first aspect, the present invention provides an electrolyte comprising a first additive, wherein the first additive comprises a cyanoborate compound, wherein the cyanoborate compound has a benzene ring and a cyano group and a borate group located on the benzene ring, wherein the cyano group is located at an ortho position to the borate group.

[0041] The first additive in the electrolyte provided by the present invention includes a cyanoborate compound, and the cyanoborate compound has a cyano group and a borate group located on a benzene ring, and the cyano group is located in the ortho position of the borate group, which can reduce the impedance of the battery, alleviate the ion precipitation phenomenon, and improve the cycle performance of the battery. The reason for analysis is that the cyano group can complex transition metals and prevent the transition metal on the positive electrode side from migrating to the negative electrode, thereby improving the overall performance of the battery. However, the cyano group has a low solubility in carbonate solvents and is easily precipitated at low temperatures, resulting in turbidity of the electrolyte, which in turn has an adverse effect on the battery. In order to solve this problem, a benzene ring structure is introduced, and the presence of the benzene ring significantly increases the solubility of the cyano group, ensuring that the electrolyte remains clear and stable under various temperature conditions. In addition, the borate group can form a stable solid electrolyte interface (SEI) film on the positive and negative electrodes of the battery. This film layer has a low impedance, which is conducive to reducing the overall impedance of the battery, and effectively alleviates the precipitation problem of ions and improves the cycle performance of the battery. Moreover, the hydrogen atoms in the ortho position on the benzene ring are more active, and the ortho substituents will activate the benzene ring and increase its reactivity, making the cyanide and borate more efficient in forming the film layer.

[0042] Furthermore, cyanoborate compounds can act as film-forming additives. When added to the electrolyte, they preferentially form a thin and dense solid electrolyte interface (SEI) film on the negative electrode surface, reducing irreversible electrolyte consumption and maintaining electrolyte stability. Furthermore, a stable SEI film not only reduces the occurrence of side reactions but also protects the electrode material, minimizing structural changes and volume expansion, thereby increasing the battery's cycle life. A stable and uniform SEI film can effectively reduce charge transfer impedance and improve ion conductivity between the electrode and electrolyte, thereby lowering the overall battery impedance and mitigating ion precipitation.

[0043] Therefore, the first additive in the electrolyte provided by the present invention includes a cyanoborate compound, and the cyanoborate compound has a cyano group and a borate group located on a benzene ring, and the cyano group is located at the ortho position of the borate group, which can reduce the impedance of the battery, alleviate the ion precipitation phenomenon, and improve the cycle performance of the battery.

[0044] Specifically, the cyanoborate compound includes a compound having a structure shown in Formula 1 and / or a compound having a structure shown in Formula 2;

[0045]

[0046] Among them, R1~R 10 Each is independently selected from hydrogen, halogen, cyano, straight-chain or branched alkyl having 1 to 20 carbon atoms, straight-chain or branched alkenyl having 2 to 20 carbon atoms, and straight-chain or branched alkynyl having 2 to 20 carbon atoms.

[0047] Specifically, the halogen may be an F element; the number of carbon atoms in a straight-chain or branched-chain alkyl group may be 1, 3, 5, 10, 12, 15, 18, 20 or a range consisting of any two thereof, and may be a fluorinated or non-fluorinated alkyl group; the number of carbon atoms in a straight-chain or branched-chain alkenyl group may be 2, 3, 5, 10, 12, 15, 18, 20 or a range consisting of any two thereof, and may be a fluorinated or non-fluorinated alkenyl group, and may contain one or more double bonds; the number of carbon atoms in a straight-chain or branched-chain alkynyl group may be 2, 3, 5, 10, 12, 15, 18, 20 or a range consisting of any two thereof, and may contain one or more triple bonds.

[0048] The cyanoborate compound of the present invention includes a compound having a structure represented by Formula 1 and / or a compound having a structure represented by Formula 2, which can further reduce the impedance of the battery, alleviate ion precipitation, and improve the cycle performance of the battery.

[0049] In some embodiments of the present invention, the cyanoborate compound includes a compound having a structure shown in Formula 1. The compound having a structure shown in Formula 1 has at least one fluorine-containing functional group. Fluorine has a low electronegativity and is easy to form a film at the negative electrode. The introduction of fluorine element can form more NaF in the negative electrode SEI film (the battery is a sodium ion battery). NaF has strong mechanical stability and a fast sodium ion transfer rate at the NaF grain boundary, which is beneficial to improving the kinetic performance of the battery.

[0050] In some embodiments of the present invention, the compound having the structure shown in Formula 1 includes at least one of the structure shown in Formula 1-1, the structure shown in Formula 1-2, the structure shown in Formula 1-3, and the structure shown in Formula 1-4:

[0051]

[0052] The structures shown in Formulas 1-1 to 1-4 can further form a stable and dense SEI film on the surface of the negative electrode, reduce the irreversible consumption of the electrolyte, maintain the stability of the electrolyte, and effectively reduce the charge transfer impedance and improve the conductivity of ions between the electrode and the electrolyte, thereby improving the cycle performance of the battery, reducing the impedance of the battery, and alleviating the ion precipitation phenomenon.

[0053] In some embodiments of the present invention, the cyanoborate compound includes a compound having a structure shown in Formula 2. The compound having a structure shown in Formula 2 has at least one fluorine-containing functional group. Fluorine has a low electronegativity and is easy to form a film at the negative electrode. The introduction of fluorine element can form more NaF in the negative electrode SEI film (the battery is a sodium ion battery). NaF has strong mechanical stability and a fast sodium ion transfer rate at the NaF grain boundary, which is beneficial to improving the kinetic performance of the battery.

[0054] In some embodiments of the present invention, the compound having the structure shown in Formula 2 includes at least one of the structure shown in Formula 2-1, the structure shown in Formula 2-2, the structure shown in Formula 2-3, and the structure shown in Formula 2-4:

[0055]

[0056] The structures shown in Formulas 2-1 to 2-4 can further form a stable and dense SEI film on the surface of the negative electrode, reduce the irreversible consumption of the electrolyte, maintain the stability of the electrolyte, and effectively reduce the charge transfer impedance and improve the conductivity of ions between the electrode and the electrolyte, thereby improving the cycle performance of the battery, reducing the impedance of the battery, and alleviating the ion precipitation phenomenon.

[0057] In some embodiments of the present invention, the mass percentage of the first additive in the electrolyte is 0.05% to 3%, for example, it can be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 3% or any two thereof.

[0058] In the present invention, the first additive's content in the electrolyte by mass within the aforementioned range effectively performs its function, forming a stable SEI film and inhibiting side reactions, effectively reducing irreversible electrolyte consumption, maintaining the chemical stability of the electrolyte, protecting the electrode materials, and extending the battery's cycle life. Furthermore, the first additive's content within the aforementioned range effectively reduces battery impedance and promotes uniform sodium ion deposition, reducing dendrite formation and mitigating ion leaching.

[0059] Furthermore, the first additive may comprise 0.5% to 2% by mass of the electrolyte, for example, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, or any combination thereof. This can further improve the battery's cycle performance, reduce the battery's impedance, and alleviate ion precipitation.

[0060] In some embodiments of the present invention, the electrolyte further includes a second additive, which may be a film-forming additive, and the second additive includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), 1-propylene-1,3-sultone (PES), vinyl ethylene carbonate (VEC), diethylene sulfate (DTD), methylene dicarbonate (MMDS), tris(trimethylsilyl) phosphate (TMSP), succinic anhydride (SA), and maleic anhydride (MMA).

[0061] The electrolyte of the present invention also includes a second additive, and the second additive includes the aforementioned substance. This second additive can synergistically form a film with the first additive, forming a stable and dense SEI film on the electrode surface. This effectively protects the electrode material, reduces the occurrence of side reactions, and improves the cycle life of the battery. It can also effectively reduce the battery's impedance, inhibit uneven metal deposition on the electrode surface, and reduce the formation of dendrites, thereby improving the battery's safety and stability.

[0062] In some embodiments of the present invention, the mass percentage of the second additive in the electrolyte is 0.05% to 10%, for example, it can be 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any two thereof.

[0063] In the present invention, the mass percentage of the second additive in the electrolyte is within the above range, which can further improve the cycle life of the battery, reduce the impedance of the battery, and alleviate the occurrence of ion precipitation.

[0064] Furthermore, the mass percentage of the second additive in the electrolyte is 0.5% to 6%, for example, it can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6% or any two of them, which can further improve the cycle life of the battery, reduce the impedance of the battery, and alleviate the occurrence of ion precipitation.

[0065] The electrolyte of the present invention may be a non-aqueous electrolyte. Specifically, the electrolyte includes a solvent and an electrolyte salt, and the solvent may include an organic solvent.

[0066] In some embodiments of the present invention, the electrolyte further includes an electrolyte salt; the electrolyte salt includes at least one of a borate, an imide salt, a hexafluorophosphate, and a perchlorate. This facilitates the formation of a stable SEI film on the negative electrode surface, protecting the electrode material and reducing side reactions, thereby improving battery cycle performance, reducing battery impedance, and slowing ion precipitation.

[0067] In some embodiments, the electrolyte salt includes hexafluorophosphate, which can be used in conjunction with the first and second additives to further improve the battery's cycle performance, reduce the battery's impedance, and slow down ion precipitation. This is because hexafluorophosphate, when used in an electrolyte system, generates phosphorus pentafluoride during the battery's charge and discharge process. The cyano group in the cyanoborate compound can combine with phosphorus pentafluoride to inhibit the formation of HF in the system, protecting the positive electrode interface from attack. It can also broaden the electrochemical window of the electrolyte, resulting in the electrolyte having higher oxidative stability and being suitable for high-voltage systems.

[0068] Specifically, the electrolyte salt may include at least one of sodium difluoro(oxalato)borate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium hexafluorophosphate, sodium tetrafluoroborate, and sodium perchlorate.

[0069] In some embodiments, the concentration of the electrolyte salt in the electrolyte is 0.3 mol / L to 3 mol / L, for example, it can be 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or any two thereof.

[0070] The concentration of the electrolyte salt in the electrolyte of the present invention can provide high ionic conductivity, and is conducive to the formation of a stable SEI film, thereby improving the cycle life and safety of the battery.

[0071] Furthermore, the concentration of the electrolyte salt in the electrolyte is 0.8 mol / L to 1.2 mol / L, for example, it can be 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L or a range consisting of any two of them, which can further improve the cycle life and safety of the battery.

[0072] It is understood that the electrolyte also includes an organic solvent; the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl formate, ethyl acetate, propyl acetate, ethyl propionate, methyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isopentyl propionate, ethyl butyrate, n-propyl butyrate, propyl isobutyrate, n-pentyl butyrate, n-pentyl isobutyrate, n-butyl butyrate, isobutyl isobutyrate, n-pentyl valerate, butyrolactone, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0073] The organic solvent in the electrolyte of the present invention helps to dissolve the electrolyte salt, improve the ionic conductivity of the electrolyte, and can also form a stable SEI film on the surface of the negative electrode, reduce the occurrence of side reactions, and improve the cycle life.

[0074] In the present invention, the contents of the first additive, the second additive, and the electrolyte salt in the electrolyte can be obtained by testing using the following method:

[0075] The discharged battery is squeezed or soaked to obtain liquid, and the electrolyte is then subjected to gas chromatography-mass spectrometry testing and gas chromatography testing. The content of the first additive, the second additive and the electrolyte salt (such as sodium salt) is determined based on the peak time and peak area in the spectrum.

[0076] In a second aspect, the present invention provides a battery comprising the electrolyte as described above. The battery has advantages corresponding to the above electrolyte, which will not be described in detail.

[0077] In some embodiments of the present invention, the battery includes a sodium ion battery, which has advantages corresponding to the above-mentioned electrolyte and will not be described in detail.

[0078] The sodium ion battery of the present invention comprises a battery shell, a battery core and an electrolyte sealed in the battery shell, and the battery core comprises a positive electrode sheet, a negative electrode sheet and a diaphragm.

[0079] A positive electrode sheet typically includes a positive electrode current collector and a positive electrode material coated and / or filled onto the positive electrode current collector. The positive electrode current collector can be at least one of aluminum foil, copper foil, and nickel-plated steel strip. For example, aluminum foil can be used as the positive electrode current collector. The positive electrode material typically includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The present invention has no particular limitations on the positive electrode active material and may be at least one of an oxide material, a polyanion material, an organic polymer, or a Prussian blue-based material. Oxide materials include layered oxides and / or tunnel-structured oxides, and polyanion materials include at least one of phosphates, fluorinated phosphates, pyrophosphates, and sulfates. The present invention has no particular limitations on the positive electrode binder and may be selected from fluorine-containing resins and / or polyolefin compounds, such as at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and styrene-butadiene rubber. The positive electrode binder content can be 0.01% to 8%, preferably 1% to 5%, based on the mass of the positive electrode active material. The present invention has no particular limitation on the positive electrode conductive agent, which can be selected from at least one of conductive carbon black, acetylene black, nickel powder, copper powder and conductive graphite. The content of the positive electrode conductive agent can be 0% to 15%, preferably 0% to 10%, based on the mass of the positive electrode active material.

[0080] The negative electrode sheet includes a negative electrode current collector and a negative electrode material coated and / or filled on the negative electrode current collector. The negative electrode current collector can be selected from at least one of aluminum foil, copper foil, nickel-plated steel strip, and punched steel strip. The negative electrode material includes a negative electrode active material and a binder. The negative electrode active material can be selected from conventional negative electrode active materials, such as at least one of carbon-based, titanium-based, and alloy materials. The carbon-based material can include hard carbon materials. The negative electrode binder can be selected from conventional binders, such as at least one of polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), hydroxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). Generally speaking, the mass percentage of the negative electrode binder to the negative electrode active material is 0.5% to 8%, preferably 2% to 5%.

[0081] In some embodiments, the negative electrode active material comprises a hard carbon material. Hard carbon materials have numerous surface defects, which lead to numerous side reactions between the electrolyte and the negative electrode surface. These side reactions not only lead to irreversible consumption of the electrolyte but also form a thicker negative electrode surface passivation film, which in turn increases battery impedance and ion precipitation (e.g., sodium precipitation in sodium-ion batteries).

[0082] In the electrolyte provided by the present invention, the compound of the structure shown in Formula 1 or the compound of the structure shown in Formula 2 is used as the first additive. After being added to the electrolyte, a thin and dense solid electrolyte interface (SEI) film is preferentially formed on the surface of the negative electrode, reducing the irreversible consumption of the electrolyte and maintaining the stability of the electrolyte. In addition, the stable SEI film not only reduces the occurrence of side reactions, but also protects the electrode material, reduces the structural changes and volume expansion of the electrode material, thereby improving the cycle life of the battery. The stable and uniform SEI film can effectively reduce the charge transfer impedance and improve the conductivity of ions between the electrode and the electrolyte, thereby reducing the impedance of the overall battery and alleviating the phenomenon of ion precipitation.

[0083] The solvent used to prepare the positive and negative electrode slurries in the present invention can be selected from conventional solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), diethylformamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water, and alcohols. The amount of solvent used is sufficient to coat the slurry onto the current collector. Generally, the amount of solvent used is such that the concentration of the positive or negative electrode active material in the slurry is 40% to 90% by weight, preferably 50% to 85% by weight.

[0084] The separator, which provides both electrical insulation and liquid retention properties, is positioned between the positive and negative electrodes and sealed within the battery case along with the positive and negative electrodes and the electrolyte. The separator can be any of a variety of commonly used separators in the art, such as a composite membrane formed by welding or bonding modified polyethylene felt, modified polypropylene felt, ultrafine glass fiber felt, vinylon felt, or nylon felt to a wettable polyolefin microporous membrane.

[0085] The preparation method of the positive electrode sheet includes coating a positive electrode slurry containing a positive electrode active material, a binder, and optionally a conductive agent onto a positive electrode current collector. The positive electrode sheet is obtained after drying, roll-pressing, and slicing. Drying is generally performed at 50°C to 160°C, preferably 80°C to 150°C.

[0086] The preparation method of the negative electrode sheet is basically the same as that of the positive electrode sheet, except that the positive electrode slurry containing the positive electrode active material, the binder and the conductive agent is replaced by the negative electrode slurry containing the negative electrode active material and the binder.

[0087] The preparation method of the battery provided by the present invention comprises preparing a positive electrode sheet, a negative electrode sheet and a separator into an electrode group, and sealing the obtained electrode group and an electrolyte in a battery shell to prepare a battery, wherein the electrolyte is the electrolyte provided by the first aspect of the present invention.

[0088] The batteries of the present invention may be in the form of battery cells, battery modules, and battery packs. In some embodiments, battery cells may be assembled into a battery module, which may contain one or more battery cells, with the specific number selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, which may contain one or more battery modules, with the specific number selected by those skilled in the art based on the application and capacity of the battery pack.

[0089] There is no particular restriction on the specific type of the battery of the present invention. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft pack batteries and cylindrical batteries, etc., and this application does not impose any particular restrictions. From the perspective of the pole core structure, the pole core of the battery can be a wound pole core (i.e., the positive electrode sheet, the negative electrode sheet and the separator are stacked and arranged, and then the pole core is made by a winding process), or it can be a laminated pole core (i.e., multiple positive electrode sheets, negative electrode sheets and separators are stacked to form a pole core). The outer shell can be a hard shell (such as a steel shell, a hard plastic shell, etc.), or a soft shell (such as an aluminum plastic film, a bag-type soft shell, etc.). The present invention does not impose any particular restrictions.

[0090] It should be noted that during the preparation process of the battery provided by the present invention, there may be deviations between the amount of each substance added and the content of each substance tested in the electrolyte obtained after disassembling the battery, but they are within the error range. Therefore, the amount of each substance added during the battery preparation process is basically consistent with the content of each substance in the electrolyte.

[0091] In a third aspect, the present invention provides a battery device comprising a plurality of batteries as described above.

[0092] The battery device of the present invention may include a plurality of battery cells, and the plurality of battery cells are connected in series, in parallel or in a hybrid manner, wherein the hybrid manner is a combination of series and parallel.

[0093] In a fourth aspect, the present invention provides an electrical device comprising the battery as described above. The electrical device has advantages corresponding to the above-mentioned electrolyte, which will not be described in detail.

[0094] The electrical equipment of the present invention can be conventional electrical equipment in the field, such as power equipment (such as electric vehicles), electronic equipment (such as computers, mobile phones, digital cameras, printers, fax machines, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), household appliances (such as air conditioners, refrigerators, washing machines, microwave ovens, etc.), etc., without special restrictions.

[0095] The technical solution of the present invention is further described below with reference to specific embodiments.

[0096] Example 1

[0097] The preparation method of the electrolyte of this embodiment comprises the following steps:

[0098] An electrolyte solution was prepared in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm. 15 g of ethylene carbonate (EC), 28 g of ethyl methyl carbonate (EMC), 38 g of diethyl carbonate (DEC), 3 g of fluoroethylene carbonate (FEC), and 1 g of vinylene carbonate (VC) were mixed, and then 13 g of sodium hexafluorophosphate (NaPF6) and 2 g of the compound represented by Formula 1-1 were added and mixed uniformly to prepare the electrolyte solution. The first additive, i.e., the compound represented by Formula 1-1, accounted for 2% by weight of the electrolyte solution; the second additives, i.e., FEC and VC, accounted for 4% by weight of the electrolyte solution; and the concentration of the sodium salt NaPF6 in the electrolyte solution was 0.99 mol / L.

[0099] Example 2

[0100] The preparation methods of the electrolytes of Example 2 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 1-2.

[0101] Example 3

[0102] The preparation methods of the electrolytes of Example 3 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 1-3.

[0103] Example 4

[0104] The preparation methods of the electrolytes of Example 4 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 1-4.

[0105] Example 5

[0106] The preparation methods of the electrolytes of Example 5 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 2-1.

[0107] Example 6

[0108] The preparation methods of the electrolytes of Example 6 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 2-2.

[0109] Example 7

[0110] The preparation methods of the electrolytes of Example 7 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 2-3.

[0111] Example 8

[0112] The preparation methods of the electrolytes of Example 8 and Example 1 are basically the same, except that the first additive is a compound having a structure shown in Formula 2-4.

[0113] Example 9

[0114] The preparation methods of the electrolytes of Example 9 and Example 6 are basically the same, except that 0.5 g of fluoroethylene carbonate (FEC) and 1 g of vinylene carbonate (VC) are added as the second additive.

[0115] Example 10

[0116] The preparation method of the electrolyte of Example 10 is substantially the same as that of Example 7, except that 0.05 g of the compound of Formula 2-3 is added. The first additive, i.e., the compound of Formula 2-3, accounts for 0.05% by weight of the electrolyte, and the second additive, i.e., FEC and VC, account for 4.08% by weight of the electrolyte.

[0117] Example 11

[0118] The preparation method of the electrolyte in Example 11 is substantially the same as that in Example 7, except that 0.5 g of the compound of Formula 2-3 is added. The first additive, i.e., the compound of Formula 2-3, accounts for 0.51% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 4.06% by weight of the electrolyte.

[0119] Example 12

[0120] The preparation method of the electrolyte of Example 12 is substantially the same as that of Example 7, except that 3 g of the compound of Formula 2-3 is added. The first additive, i.e., the compound of Formula 2-3, accounts for 2.97% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 3.96% by weight of the electrolyte.

[0121] Example 13

[0122] The preparation method of the electrolyte of Example 13 is basically the same as that of Example 7, except that 3 g of diethyl sulfate (DTD) and 1 g of 1,3-propane sultone (PS) are added as the second additive.

[0123] Example 14

[0124] The preparation method of the electrolyte of Example 14 is substantially the same as that of Example 7, except that 0.03 g of fluoroethylene carbonate (FEC) and 0.02 g of vinylene carbonate (VC) are added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 2.08% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 0.05% by weight of the electrolyte.

[0125] Example 15

[0126] The preparation method of the electrolyte of Example 15 is substantially the same as that of Example 7, except that 0.3 g of fluoroethylene carbonate (FEC) and 0.2 g of vinylene carbonate (VC) are added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 2.07% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 0.52% by weight of the electrolyte.

[0127] Example 16

[0128] The preparation method of the electrolyte of Example 16 is substantially the same as that of Example 7, except that 3.8 g of fluoroethylene carbonate (FEC) and 2.4 g of vinylene carbonate (VC) are added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 1.96% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 6.07% by weight of the electrolyte.

[0129] Example 17

[0130] The preparation method of the electrolyte of Example 17 is substantially the same as that of Example 7, except that 7 g of fluoroethylene carbonate (FEC) and 3.6 g of vinylene carbonate (VC) are added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 1.88% by weight of the electrolyte, and the second additives, i.e., FEC and VC, account for 9.94% by weight of the electrolyte.

[0131] Example 18

[0132] The preparation method of the electrolyte of Example 18 is basically the same as that of Example 7, except that 13 g of sodium tetrafluoroborate (NaBF4) is added as the electrolyte salt.

[0133] Example 19

[0134] The preparation method of the electrolyte in Example 19 is substantially the same as that in Example 7, except that 4 g of sodium hexafluorophosphate (NaPF6) is added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 2.2% by weight of the electrolyte, the second additive, i.e., FEC and VC, account for 4.4% by weight of the electrolyte, and the concentration of the sodium salt NaPF6 in the electrolyte is 0.305 mol / L.

[0135] Example 20

[0136] The preparation method of the electrolyte in Example 20 is substantially the same as that in Example 7, except that 10.6 g of sodium hexafluorophosphate (NaPF6) is added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 2.05% by weight of the electrolyte, the second additive, i.e., FEC and VC, account for 4.1% by weight of the electrolyte, and the concentration of the sodium salt NaPF6 in the electrolyte is 0.808 mol / L.

[0137] Example 21

[0138] The preparation method of the electrolyte in Example 21 is substantially the same as that in Example 7, except that 39 g of sodium hexafluorophosphate (NaPF6) is added. The first additive, i.e., the compound having the structure shown in Formula 2-3, accounts for 1.59% by weight of the electrolyte, the second additive, i.e., FEC and VC, account for 3.17% by weight of the electrolyte, and the concentration of the sodium salt NaPF6 in the electrolyte is 2.97 mol / L.

[0139] Comparative Example 1

[0140] The preparation methods of the electrolytes of Comparative Example 1 and Example 1 are basically the same, except that 2 g of dimethyl-acetonitrile borate is added as the first additive.

[0141] Comparative Example 2

[0142] The preparation methods of the electrolytes of Comparative Example 2 and Example 1 are basically the same, except that 2 g of hexanetricarbonitrile (HTCN) is added as the first additive.

[0143] Comparative Example 3

[0144] The preparation methods of the electrolytes of Comparative Example 3 and Example 1 are basically the same, except that 2 g of tris(trimethylsilyl)borate (TMSB) is added as the first additive.

[0145] Comparative Example 4

[0146] The preparation method of the electrolyte of Comparative Example 4 is basically the same as that of Example 1, except that no first additive is added; and the mass percentage of the second additives, namely FEC and VC, in the electrolyte is 4.08%.

[0147] Test example:

[0148] Preparation of positive electrode sheet: Sodium iron pyrophosphate positive electrode material (NFPP), polyvinylidene fluoride (PVDF) binder, and acetylene black (Super P) conductive agent are mixed in a mass ratio of 8:1:1, and a certain amount of N-methylpyrrolidone (NMP) is added to prepare a positive electrode slurry. The solid content of the slurry is adjusted to about 50%. After degassing and sieving, the slurry is evenly coated on the surface of aluminum foil. After drying, rolling, and cutting, the positive electrode sheet is obtained.

[0149] Preparation of negative electrode sheet: Hard carbon negative electrode material (HC), styrene-butadiene rubber (SBR) / carboxymethyl cellulose (CMC) composite binder and acetylene black (Super P) conductive agent are mixed in a mass ratio of 8:1:1, and deionized water is added to prepare negative electrode slurry. The solid content is adjusted to about 45%. After degassing and sieving, it is evenly coated on the surface of aluminum foil. After drying, rolling and cutting, the negative electrode sheet is obtained.

[0150] Preparation of soft-pack batteries: The negative electrode sheet, separator, and positive electrode sheet are stacked in sequence to form a battery cell, which is then encapsulated in an aluminum-plastic shell. After the battery cell is baked to remove moisture, the sodium-ion battery electrolyte is injected into the soft-pack battery. After aging, formation, aging, and capacity separation, a soft-pack sodium-ion battery is obtained.

[0151] 1. Battery impedance test: Connect the positive and negative plates of the battery to the electrochemical workstation respectively, start the impedance test program, the frequency range is 5mHZ ~ 10kHZ, and export the impedance spectrum.

[0152] 2. Normal temperature cycle performance test: Place the battery in a 25℃ constant temperature box for 2 hours, then charge it at a constant current and constant voltage of 0.5C to 3.60V, and cut off at 0.05C. Leave it for 5 minutes, and discharge it at a constant current of 1C to 2.0V. This is considered one cycle. Repeat this cycle 1000 times, and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 500th cycle. 500 And the discharge capacity Q at the 1000th cycle 1000 The capacity retention rate after 500 cycles is Q = Q 500 / Q1×100%, capacity retention rate after 1000 cycles Q=Q 1000 / Q1×100%. The test results are shown in Table 1.

[0153] 3. High temperature cycle test: Place the battery in a 45℃ constant temperature box for 2 hours, then charge it at 0.5C constant current and constant voltage to 3.60V, and cut off at 0.05C. Leave it for 5 minutes, and discharge it at 1C constant current to 2.0V. This is considered one cycle. Repeat this cycle 500 times, and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 500th cycle. 500 The capacity retention rate after 500 cycles is Q = Q 500 / Q1×100%. The test results are shown in Table 1.

[0154] 4. Sodium precipitation: Disassemble the battery and observe the negative electrode interface, which appears grayish white. Perform SEM / EDS testing. If sodium dendrites are present at the negative electrode interface, it is considered sodium precipitation. If no sodium dendrites are present, it is considered sodium precipitation.

[0155] Figure 1 This is the SEM image of the negative electrode in the battery prepared with the electrolyte of Example 1.

[0156] from Figure 1 It can be seen that in the battery prepared with the electrolyte of Example 1, no sodium dendrites appeared in the negative electrode sheet, that is, no sodium precipitation phenomenon occurred.

[0157] Figure 2 This is the SEM image of the negative electrode in the battery prepared with the electrolyte of Comparative Example 1.

[0158] from Figure 2 It can be seen that in the battery prepared with the electrolyte of Comparative Example 1, sodium dendrites appeared in the negative electrode sheet, that is, sodium precipitation occurred.

[0159] Table 1

[0160]

[0161]

[0162] Table 2

[0163]

[0164]

[0165] As can be seen from Table 1, compared with the comparative example, the first additive in the electrolyte provided by the present invention includes a cyanoborate compound, and the cyanoborate compound has a cyano group and a borate group located on a benzene ring, and the cyano group is located at the ortho position of the borate group, which can reduce the impedance of the battery, alleviate the ion precipitation phenomenon, and improve the cycle performance of the battery.

[0166] It can be seen from Examples 7 and 10-12 that when the mass percentage of the first additive in the electrolyte is 0.5% to 2%, the impedance of the battery can be further reduced and the cycle performance of the battery can be improved.

[0167] It can be seen from Examples 7 and 14-17 that when the mass percentage of the second additive in the electrolyte is 0.5% to 6%, the impedance of the battery can be further reduced and the cycle performance of the battery can be improved.

[0168] It can be seen from Examples 7 and 19-21 that when the concentration of the electrolyte salt in the electrolyte is 0.8 mol / L to 1.2 mol / L, the impedance of the battery can be further reduced and the cycle performance of the battery can be improved.

[0169] Finally, it should be noted that those skilled in the art will readily identify other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The present invention is not limited to the precise structure described above and illustrated in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof. The scope of the present invention is limited solely by the appended claims.

Claims

1. An electrolyte, characterized in that: The invention comprises a first additive, wherein the first additive comprises a cyanoborate compound, wherein the cyanoborate compound has a benzene ring, a cyano group and a borate group located on the benzene ring, and the cyano group is located at an ortho position to the borate group.

2. The electrolyte according to claim 1, characterized in that The cyanoborate compound includes a compound having a structure shown in Formula 1 and / or a compound having a structure shown in Formula 2; Among them, R1~R 10 Each is independently selected from hydrogen, halogen, cyano, straight-chain or branched alkyl having 1 to 20 carbon atoms, straight-chain or branched alkenyl having 2 to 20 carbon atoms, and straight-chain or branched alkynyl having 2 to 20 carbon atoms.

3. The electrolyte according to claim 2, characterized in that The cyanoborate compound includes the compound having the structure shown in Formula 1, and the compound having the structure shown in Formula 1 has at least one fluorine-containing functional group.

4. The electrolyte according to claim 2 or 3, characterized in that The compound having the structure shown in Formula 1 includes at least one of the structure shown in Formula 1-1, the structure shown in Formula 1-2, the structure shown in Formula 1-3, and the structure shown in Formula 1-4:

5. The electrolyte according to any one of claims 2 to 4, characterized in that The cyanoborate compound includes the compound having the structure shown in Formula 2, and the compound having the structure shown in Formula 2 has at least one fluorine-containing functional group.

6. The electrolyte according to any one of claims 2 to 5, characterized in that The compound having the structure shown in Formula 2 includes at least one of the structure shown in Formula 2-1, the structure shown in Formula 2-2, the structure shown in Formula 2-3, and the structure shown in Formula 2-4:

7. The electrolyte according to any one of claims 1 to 6, characterized in that The mass percentage of the first additive in the electrolyte is 0.05% to 3%.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The mass percentage of the first additive in the electrolyte is 0.5% to 2%.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The electrolyte further includes a second additive, which includes at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, 1-propylene-1,3-sultone, vinyl ethylene carbonate, vinyl sulfate, methylene dicarbonate, tris(trimethylsilyl)phosphate, succinic anhydride, and maleic anhydride.

10. The electrolyte according to claim 9, characterized in that The mass percentage of the second additive in the electrolyte is 0.05% to 10%.

11. The electrolyte according to claim 9 or 10, characterized in that The mass percentage of the second additive in the electrolyte is 0.5% to 6%.

12. The electrolyte according to any one of claims 1 to 11, characterized in that The electrolyte further includes an electrolyte salt; The electrolyte salt includes at least one of borate, imide salt, hexafluorophosphate, and perchlorate; And / or, the concentration of the electrolyte salt in the electrolyte solution is 0.3 mol / L to 3 mol / L.

13. The electrolyte according to claim 12, characterized in that The concentration of the electrolyte salt in the electrolyte solution is 0.8 mol / L to 1.2 mol / L.

14. A battery, characterized in that: The electrolyte comprises the electrolyte according to any one of claims 1 to 13.

15. The battery according to claim 14, characterized in that The battery comprises a sodium ion battery.

16. A battery device, characterized in that: Comprising a plurality of batteries as claimed in claim 14 or 15.

17. An electrical device, characterized in that: Comprising the electrolyte according to any one of claims 1 to 13, or the battery according to claim 14 or 15, or the battery device according to claim 16.

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