Electrolyte, battery containing electrolyte, energy storage device and electric equipment

Abstract

The invention provides an electrolyte, a battery containing the electrolyte, an energy storage device and electric equipment, the electrolyte comprises a compound shown as a formula (I) and a compound shown as a formula (II), in the formula (I), R1, R2, R3, R4 and R5 are independently selected from hydrogen, alkyl or amido, and at least one of R1-R5 is amido; in the formula (II), R6 is selected from alkyl or vinyl; based on the mass of the electrolyte, the mass percentage content of the compound shown in the formula (I) is a, the mass percentage content of the compound shown in the formula (II) is b, a is larger than or equal to 0.1% and smaller than or equal to 1%, and b is larger than or equal to 0.1% and smaller than or equal to 3%. # imgabs0 #

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to an electrolyte, a battery containing the electrolyte, an energy storage device, and an electrical equipment. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have the advantages of high energy density, low self-discharge, and light weight, and are therefore widely used in fields such as energy storage devices.

[0003] As people's requirements for the performance of secondary batteries increase, for example, the requirements for the performance of secondary batteries in energy storage scenarios increase, secondary batteries are not only required to have stable performance under normal temperature conditions, but also required to have stable performance under high temperature conditions, such as high temperature cycle performance, high temperature storage stability and other performance, so as to meet the long-term high temperature stable operation requirements of energy storage devices in energy storage application scenarios. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses an electrolyte, a battery containing the electrolyte, an energy storage device and an electrical equipment to improve the high temperature cycle performance and high temperature storage stability of a secondary battery.

[0005] In a first aspect, the present application provides an electrolyte comprising a compound of formula (I) and a compound of formula (II):

[0006]

[0007] In formula (I), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, an alkyl group, or an amide group, and at least one of R1 to R5 is an amide group;

[0008] In formula (II), R6 is selected from alkyl or vinyl;

[0009] Based on the mass of the electrolyte, the mass percentage of the compound of formula (I) is a, the mass percentage of the compound of formula (II) is b, 0.1%≤a≤1%, and 0.1%≤b≤3%.

[0010] In some embodiments of the present application, 0.5%≤b≤2%.

[0011] In some embodiments of the present application, 0.1≤a / b≤1.5.

[0012] In some embodiments of the present application, the compound of formula (I) is selected from at least one of the following compounds:

[0013]

[0014] In some embodiments of the present application, the compound of formula (II) is selected from at least one of the following compounds:

[0015]

[0016] In some embodiments of the present application, the electrolyte further includes cyclic carbonates and chain carbonates, the cyclic carbonates include at least one of ethylene carbonate and propylene carbonate; the chain carbonates include at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0017] In a second aspect, the present application provides a battery, comprising the electrolyte described in the first aspect.

[0018] In some embodiments of the present application, the battery further comprises a negative electrode plate, the negative electrode plate comprises a negative electrode material layer, the negative electrode material layer comprises a negative electrode active material, the negative electrode active material comprises graphite, the mass percentage of the compound of formula (I) in the electrolyte is a, and the Dv10 of the graphite satisfies a:

[0019] In some embodiments of the present application, the Dv10 of the graphite is 5 μm to 10 μm.

[0020] In a third aspect, the present application provides an energy storage device, comprising a housing and at least one battery as described in the second aspect, wherein the battery is accommodated in the housing.

[0021] In a fourth aspect, the present application provides an electrical device, comprising the energy storage device described in the third aspect, wherein the energy storage device supplies power to the electrical device.

[0022] Compared with the prior art, this application has at least the following beneficial effects:

[0023] The present application provides an electrolyte, a battery containing the electrolyte, an energy storage device and an electrical device, wherein the electrolyte includes a compound of formula (I) and a compound of formula (II), the compound of formula (I) is a pyridine amide compound, the compound of formula (II) is a sulfate compound, based on the mass of the electrolyte, the mass percentage of the compound of formula (I) is a, the mass percentage of the compound of formula (II) is b, 0.1%≤a≤1%, and 0.1%≤b≤3%. The electrolyte of the present application contains the above-mentioned compound of formula (I) and the compound of formula (II), and by regulating the content of the above-mentioned two compounds, under the synergistic effect of the above-mentioned two compounds, the high-temperature cycle performance and high-temperature storage stability of the lithium-ion battery are improved, and it is more suitable for energy storage devices that require long-term high-temperature stable operation of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application;

[0026] Figure 2 A schematic diagram of the structure of an energy storage system according to an implementation scheme of the present application.

[0027] Explanation of the reference numerals: 1 - energy storage device, 2 - electric energy conversion device, 3 - first user load, 4 - second user load, 400 - energy storage system, 410 - high voltage cable, 420 - first electric energy conversion device, 430 - second electric energy conversion device. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0030] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0031] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0033] It should be noted that, in the present application, a lithium-ion battery is used as an example of a secondary battery to explain the present application, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0034] At present, lithium iron phosphate is mostly used as the main positive electrode active material in the energy storage field. Lithium iron phosphate has the advantages of not easy to release oxygen and good electrochemical and thermal stability. In order to improve the energy density of energy storage devices based on lithium iron phosphate positive electrode active materials, thicker electrode coatings and higher cold pressing and compaction are currently used. At the same time, the capacity of single cells is getting larger and larger. On the basis of the same active material capacity, the amount of current collector and electrolyte used is reduced. While these solutions bring high energy density, the stability of lithium-ion batteries under high temperature conditions is also affected. In addition, in large-capacity lithium-ion batteries, lithium-ion batteries have high heat generation and poor heat dissipation. During operation, heat accumulates, and the electrolyte is easily decomposed and evaporated, resulting in increased internal pressure of the lithium-ion battery, affecting the safety of the energy storage device.

[0035] In view of this, the present application provides an electrolyte, which includes a compound of formula (I) and a compound of formula (II):

[0036]

[0037] In formula (I), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, an alkyl group, or an amide group, and at least one of R1 to R5 is an amide group;

[0038] In formula (II), R6 is selected from alkyl or vinyl;

[0039] Based on the mass of the electrolyte, the mass percentage of the compound of formula (I) is a, and the mass percentage of the compound of formula (II) is b, 0.1%≤a≤1%, and 0.1%≤b≤3%; in another optional embodiment, 0.5%≤b≤2%. For example, a is 0.1%, 0.5%, 0.6%, 0.8%, 0.9% or 1%; b is 0.1%, 0.3%, 0.5%, 1%, 2% or 3%.

[0040] The inventors have found that during the cycle of lithium-ion batteries, although the compound of formula (I) will preferentially form a film on the negative electrode interface to construct a SEI (Solid Electrolyte Interphase) film rich in inorganic components Li3N, thereby improving the mechanical strength of the SEI film, as the content of the compound of formula (I) in the electrolyte increases, its influence on the impedance of the SEI film becomes greater, which may affect the high-temperature cycle performance of the lithium-ion battery; although the organic components in the generated SEI film containing SO chain segments when the compound of formula (II) forms a film on the negative electrode interface can increase the transmission rate of lithium ions in the SEI film, it is easily catalyzed by the PF5 decomposed from LiPF6 at high temperature and undergoes ring-opening polymerization, thereby causing the electrolyte to deteriorate and affecting the high-temperature storage stability of the lithium-ion battery. The electrolyte of the present application contains both the compound of formula (I) and the compound of formula (II), wherein the compound of formula (I) has a higher reduction potential and electrostatic potential than the compound of formula (II), thereby forming a film in priority to the compound of formula (II), constructing Li3N rich in inorganic components in the inner layer of the SEI film, and reducing the solubility of the electrolyte film at high temperature; and the lone electron of the amide group in the compound of formula (I) can stabilize PF5 decomposed from LiPF6, reduce the attack of PF5 on the compound of formula (II), thereby slowing down the degree of decomposition of the electrolyte, improving the storage stability of the electrolyte, and improving the high-temperature storage stability of the lithium-ion battery; the organic components in the SEI film containing SO segments generated by the compound of formula (II) can effectively increase the transmission speed of lithium ions in the SEI film, thereby improving the effect of the compound of formula (I) on the impedance of the SEI film and improving the high-temperature cycle performance of the lithium-ion battery. In addition, the electron-withdrawing group in the compound of formula (I) has a strong dipole effect on the compound of formula (II), thereby promoting the ring opening of the compound of formula (II), which is beneficial to constructing a SEI film with high ion conductivity and low solubility characteristics, with an inner layer rich in inorganic components and an outer layer wrapped with organic components. The present application regulates the content of the above two compounds within the scope of the present application, and through the synergistic effect of the compound of formula (I) and the compound of formula (II), the improvement effect on high-temperature cycle performance and high-temperature storage stability can be optimized, so that the lithium-ion battery exhibits excellent high-temperature cycle performance and high-temperature storage stability.

[0041] In the present application, high temperature refers to a temperature greater than or equal to 45°C.

[0042] In some embodiments of the present application, 0.1≤a / b≤1.5. For example, a / b=0.1, a / b=0.5, a / b=0.8, a / b=1 or a / b=1.5. By regulating a / b within the above range, it is beneficial to further improve the high temperature cycle performance and high temperature storage stability of lithium ion batteries.

[0043] In some embodiments of the present application, the compound of formula (I) is selected from at least one of the following compounds:

[0044]

[0045] By selecting at least one of the compounds of formula (I-1) to formula (I-3), it is beneficial to play a synergistic role with the compound of formula (II), so that the lithium-ion battery exhibits excellent high-temperature cycle performance and high-temperature storage stability. In addition, the amide group in the molecular structure of the above compound is conducive to the formation of an inorganic SEI film, which improves the mechanical strength of the SEI film and improves the high-temperature storage stability of the lithium-ion battery.

[0046] In some embodiments of the present application, the compound of formula (II) is selected from at least one of the following compounds:

[0047]

[0048] By selecting at least one of the compounds of formula (II-1) to formula (II-3), it is beneficial to play a synergistic role with the compound of formula (I), so that the lithium-ion battery exhibits excellent high-temperature cycle performance and high-temperature storage stability. In addition, when the above compounds are formed at the negative electrode interface, the organic components in the generated SEI film containing SO segments can effectively increase the transmission speed of lithium ions in the SEI film, which is beneficial to improve the high-temperature cycle performance of the lithium-ion battery.

[0049] The electrolyte of the present application also includes an organic solvent. In some embodiments of the present application, the electrolyte also includes cyclic carbonates and chain carbonates. The cyclic carbonates include at least one of ethylene carbonate (EC) and propylene carbonate (PC); the chain carbonates include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC). The present application has no particular restrictions on the content of the organic solvent. For example, the mass percentage of the organic solvent in the electrolyte is 65% to 90%.

[0050] The present application has no particular restrictions on the preparation process of the electrolyte. For example, at least one of ethylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl methyl carbonate, dimethyl carbonate and vinylene carbonate can be mixed in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, and then the compound of formula (I) and the compound of formula (II) are added, and then lithium salt is added to dissolve and mix evenly.

[0051] The present application has no particular limitation on the lithium salt. For example, the lithium salt includes at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiBOB, LiODFP, LiODFB, LiPO2F2 or CF3SO3Li.

[0052] The present application has no particular restrictions on the concentration of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. Taking LiPF6 as an example, the concentration of LiPF6 in the electrolyte is 10wt% to 15wt%, for example, the concentration of LiPF6 is 10wt%, 11wt%, 12wt%, 13wt% or 15wt%.

[0053] The present application also provides a battery, comprising the electrolyte described in any embodiment of the present application.

[0054] The battery of the present application may include a lithium-ion battery, which also includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet to play an isolating role.

[0055] In some embodiments of the present application, the negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, the negative electrode active material includes graphite, the mass percentage of the compound of formula (I) in the electrolyte is a, and the Dv10 of the graphite satisfies a: For example, or

[0056] The inventors have found that the Dv10 of graphite in the negative electrode sheet and the content a of the compound of formula (I) will jointly affect the performance of the lithium-ion battery. Based on this, by regulating the relationship between Dv10 and a of graphite to satisfy the above relationship, the interfacial transmission rate of lithium ions in the SEI film can be increased, thereby improving the effect of the compound of formula (I) on the impedance of the SEI film. Moreover, under the joint action of the compound of formula (I) and the compound of formula (II), an SEI film with an effective protective effect can be formed at the negative electrode interface, reducing the interfacial side reactions of small particles in the graphite, which is beneficial to improving the high-temperature cycle performance and high-temperature storage stability of the lithium-ion battery.

[0057] In the present application, Dv10 means a particle size at which the volume accumulation reaches 10% from the smaller particle size side in a volume-based particle size distribution of particles.

[0058] In some embodiments of the present application, the Dv10 of the graphite is 5 μm to 10 μm. For example, the Dv10 is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0059] The present application has no special restrictions on the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the positive electrode sheet usually includes a positive current collector and a positive active material layer. The positive active material layer can be arranged on one surface in the thickness direction of the positive current collector, or on two surfaces in the thickness direction of the positive current collector. In the present application, the positive active material layer is arranged on the surface of the positive current collector, that is, the positive active material layer can be arranged in a partial area of ​​one surface of the positive current collector, or in the entire area of ​​one surface of the positive current collector. The present application has no special restrictions on the positive current collector, as long as the purpose of the present application can be achieved, for example, it can include but is not limited to aluminum foil, aluminum alloy foil or composite current collector. In the present application, there is no special restriction on the thickness of the positive current collector, as long as the purpose of the present application can be achieved, for example, the thickness is 8μm to 13μm. The single-sided thickness of the positive active material layer of the present application can be 100μm to 200μm.

[0060] In the present application, the positive electrode active material layer includes a positive electrode active material. The present application has no particular limitation on the positive electrode active material as long as the purpose of the present application can be achieved. For example, it may include at least one of lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide and lithium iron manganese phosphate.

[0061] In the present application, the positive electrode active material layer may also include a positive electrode conductive agent. The present application has no particular restrictions on the positive electrode conductive agent, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, acetylene black and graphene. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. In the present application, the positive electrode active material layer may also include a positive electrode binder. The present application has no particular restrictions on the positive electrode binder, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of fluorine-containing resins, polypropylene resins, fiber-type binders, rubber-type binders or polyimide-type binders.

[0062] The present application has no special restrictions on the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, the negative electrode sheet usually includes a negative electrode collector and a negative electrode active material layer. The negative electrode active material layer can be arranged on one surface or two surfaces in the thickness direction of the negative electrode collector. In the present application, the negative electrode active material layer is arranged on the surface of the negative electrode collector, that is, the negative electrode active material layer can be arranged in a partial area of ​​one surface of the negative electrode collector, or in the entire area of ​​one surface of the negative electrode collector. The present application has no special restrictions on the negative electrode collector, as long as the purpose of the present application can be achieved. For example, it can include but is not limited to copper foil, copper alloy foil, nickel foil or composite current collector. In the present application, there is no special restriction on the thickness of the negative electrode collector, as long as the purpose of the present application can be achieved, for example, the thickness is 4μm to 12μm. The single-sided thickness of the negative electrode active material layer of the present application can be 70μm to 200μm.

[0063] In the present application, the negative electrode active material layer includes a negative electrode active material, wherein the negative electrode active material is not particularly limited as long as the purpose of the present application can be achieved, for example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microbeads, silicon, and silicon carbon.

[0064] In the present application, the negative electrode active material layer may further include a negative electrode binder. The present application has no particular restrictions on the negative electrode binder, as long as the purpose of the present application can be achieved, for example, it may include at least one of acrylate, polyamide, polyimide, polyamideimide, polyvinylidene fluoride (PVDF), styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose.

[0065] The present application has no particular restrictions on the diaphragm, and those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved. For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0066] The battery of the present application also includes a shell, and the present application has no particular limitation on the shell, and those skilled in the art can select it according to actual needs, as long as the purpose of the present application can be achieved. For example, the shell may include an aluminum-plastic film.

[0067] The present application does not particularly limit the preparation method of the battery, and a preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the battery includes but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain a bare cell with a wound structure, placing the bare cell in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a battery.

[0068] The present application also provides an energy storage device, including a housing and at least one battery in any of the above embodiments, wherein the battery is contained in the housing. The energy storage device having the battery has excellent performance, which is beneficial to the use of the energy storage device. By containing the battery in the housing, the fixation and protection of the battery can be increased, thereby improving the service life of the energy storage device. It is understandable that the energy storage device may have one or more batteries, and when the energy storage device contains multiple batteries, the multiple batteries may be connected in at least one of parallel and series connection.

[0069] The present application also provides an electrical device, including the energy storage device in the above-mentioned implementation scheme, which is conducive to improving the product competitiveness and performance of the electrical device. In an optional implementation scheme, the electrical device includes an electrical device body, and the energy storage device is used to supply power to the electrical device body. In an optional implementation scheme, the electrical device body includes a positive electrode of the device and a negative electrode of the device, the positive electrode plate of the battery in the energy storage device is used to electrically connect to the positive electrode of the device body of the electrical device, and the negative electrode plate of the battery in the energy storage device is used to electrically connect to the negative electrode of the device body of the electrical device, so as to supply power to the electrical device.

[0070] The electrical equipment of the present application may include but is not limited to: containers, household energy storage systems, battery vehicles, electric vehicles, ships, spacecraft, electric toys and electric tools, etc., wherein spacecrafts include airplanes, rockets, space shuttles and spacecrafts, etc., electric toys include fixed or mobile electric toys, such as electric car toys, electric ship toys and electric airplane toys, etc., and electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.

[0071] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a household energy storage system according to an implementation scheme of the present application, and the present application Figure 1 The implementation plan is described using a household energy storage scenario in user-side energy storage as an example, but the energy storage device of the present application is not limited to the household energy storage scenario.

[0072] The present application provides a household energy storage system, which includes an energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as air conditioner and other household appliances), and an energy storage device 1. The energy storage device 1 is a small energy storage box that can be mounted on an outdoor wall by wall hanging. Specifically, the photovoltaic panel can convert solar energy into electrical energy during the period of low electricity prices. The energy storage device 1 is used to store the electrical energy and supply it to street lamps and household appliances for use during the peak electricity prices, or to supply power when the power grid is out of power / power outage.

[0073] See also Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to an implementation scheme of the present application, and the present application Figure 2 The implementation plan is described using the shared energy storage scenario on the generation / distribution side as an example, and the energy storage device 1 of the present application is not limited to the energy storage scenario on the generation / distribution side.

[0074] The present application provides an energy storage system 400, which includes: a high-voltage cable 410, a first electric energy conversion device 420, a second electric energy conversion device 430 and an energy storage device 1 provided in the present application. In the case of power generation, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used to convert other forms of energy into electric energy, which are connected to the high-voltage cable 410 and supplied to the power distribution network for use. When the power load is low and the first electric energy conversion device 420 and the second electric energy conversion device 430 generate excess power, the excess power is stored in the energy storage device 1, thereby reducing the wind and solar power abandonment rates and improving the problem of new energy power generation and consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 1 in conjunction with the high-voltage cable 410 in a grid-connected mode to the power consumption side, thereby providing peak shaving, frequency regulation, standby and other services for the power grid operation, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling of the power grid, and alleviating the power supply pressure of the power grid.

[0075] Optionally, the first electric energy conversion device 420 and the second electric energy conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy and mechanical energy into electric energy.

[0076] The number of energy storage devices 1 can be multiple, and multiple energy storage devices 1 are connected in series or in parallel. Multiple energy storage devices 1 are supported and electrically connected by isolation plates (not shown). In this embodiment, "multiple" refers to two or more. An energy storage box can also be provided outside the energy storage device 1 to accommodate the energy storage device 1.

[0077] Optionally, the energy storage device 1 may include but is not limited to a battery module, a battery pack, a battery system, etc. Among them, the battery module may be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack may include multiple batteries of the present application, and the battery system may be a charging and discharging system including the battery or battery pack of the present application.

[0078] The actual application form of the energy storage device 1 provided in the embodiment of the present application may be, but is not limited to, the listed products, and may also be other application forms. The embodiment of the present application does not strictly limit the application form of the energy storage device 1. The embodiment of the present application only takes the energy storage device 1 as a multi-core battery as an example for explanation. When the energy storage device 1 is a single battery, the energy storage device 1 may be at least one of a cylindrical battery, a square battery, and the like.

[0079] Example

[0080] Hereinafter, the embodiments of the present application will be described in more detail with reference to preparation examples, examples and comparative examples. Various tests and evaluations were performed according to the following methods.

[0081] Example 1

[0082] <Preparation of positive electrode sheet>

[0083] The positive electrode active material lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and binder PVDF are mixed in a mass ratio of 97:0.7:2.3; then N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 60wt%, and stirred evenly, and then the positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 85℃; then, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer. After drying, cold pressing, striping, and cutting, a positive electrode sheet is obtained. The single-sided thickness of the positive electrode active material layer is 100μm.

[0084] <Preparation of negative electrode sheet>

[0085] The negative electrode active material artificial graphite, conductive carbon black (Super-P), thickener carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed in a mass ratio of 96.5:0.5:1:2, and deionized water is added to prepare a negative electrode slurry with a solid content of 50wt%, and stirred evenly. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 85℃; then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode active material layer coated on both sides. After drying, cold pressing, striping, and cutting, a negative electrode sheet is obtained. The single-sided thickness of the negative electrode active material layer is 70μm.

[0086] <Preparation of Electrolyte>

[0087] In an argon atmosphere glove box with a moisture content of ≤1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 2:1:2, and then lithium salt LiPF6 is added and dissolved in the above solvent, stirred until dissolved uniformly, and then the compound of formula (I), the compound of formula (II), fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are added. Among them, the types and contents of the compound of formula (I) and the compound of formula (II) are shown in Table 1, the content of FEC in the electrolyte is 1.50wt%, the content of VC in the electrolyte is 2.50wt%, and the concentration of LiPF6 in the electrolyte is 13wt%.

[0088] <Preparation of Separator>

[0089] A polyethylene (PE) porous polymer film with a thickness of 16 μm was used as the separator.

[0090] <Preparation of lithium-ion batteries>

[0091] The positive electrode sheet, separator and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive and negative electrodes to play an isolating role, and wound to obtain a bare battery cell. After welding the pole ears, the bare battery cell is placed in an aluminum-plastic film packaging bag, and the electrolyte is injected after vacuum drying. After vacuum packaging, standing, formation, shaping, capacity testing and other processes, a lithium-ion battery is obtained.

[0092] Embodiment 2 to Embodiment 10

[0093] Except that the contents of the compound of formula (I) and the compound of formula (II) are adjusted according to Table 1 in <Preparation of electrolyte>, the rest is the same as Example 1.

[0094] Example 11 to Example 14

[0095] Except for adjusting the types of the compound of formula (I) and the compound of formula (II) according to Table 1 in <Preparation of electrolyte>, the rest is the same as Example 3.

[0096] Comparative Example 1

[0097] Except that the compound of formula (I) and the compound of formula (II) are not added in the preparation of electrolyte, the rest is the same as Example 1.

[0098] Comparative Example 2 to Comparative Example 4

[0099] Except that the contents of the compound of formula (I) and the compound of formula (II) are adjusted according to Table 1 in <Preparation of electrolyte>, the rest is the same as Example 1.

[0100] Table 1 Preparation parameters of Examples 1 to 14 and Comparative Examples 1 to 4

[0101]

[0102] Test methods and equipment:

[0103] 45℃ Cyclic Performance Test:

[0104] The lithium-ion batteries prepared in the embodiments and comparative examples were subjected to charge and discharge cycle tests on a charge and discharge instrument (model: Nebula charge and discharge test system BAT-NEEFLCT-05300-V010), with the test temperature being 45°C, the cycle rate being 1C (i.e., both the charge rate and the discharge rate being 1C), the charging voltage being 2.5V to 3.65V, and the capacity retention rate after the cycle being calculated. The capacity retention rate calculation formula is: capacity retention rate after the 500th cycle = (discharge capacity after the 500th cycle / discharge capacity of the first cycle) × 100%.

[0105] Storage performance test at 60°C:

[0106] The test temperature is 25°C. After the lithium-ion battery is allowed to stand for 10 minutes, it is charged to 3.65V at a constant current of 0.33C, and then charged to 3.65V at a constant voltage of 0.05C. After standing for 30 minutes, the initial fully charged volume of the lithium-ion battery is tested and recorded as V0; the temperature of the constant temperature box is adjusted to 60°C, the lithium-ion battery is allowed to stand for 30 minutes, charged to 3.65V at a constant current of 0.33C, and allowed to stand for 1 hour. This cycle is repeated twice for recharging and stored for 60 days; thereafter, the lithium-ion battery is cooled to 25°C, and the fully charged volume of the lithium-ion battery at this time is tested and recorded as V1. The volume expansion rate after storage at 60°C for 60 days = (V1-V0) / V0×100%.

[0107] Table 2 Performance data of each embodiment and comparative example

[0108] 45℃ 500 cycles capacity retention Volume expansion rate after 60 days storage at 60℃ Example 1 95.2％ 13.3％ Example 2 95.8％ 12.9％ Example 3 96.6％ 12.1％ Example 4 95.9％ 12.7％ Example 5 95.8％ 12.8％ Example 6 96.2％ 12.6％ Example 7 95.5％ 13.0％ Example 8 95.1％ 13.5％ Example 9 82.6％ 14.6％ Example 10 84.8％ 13.7％ Embodiment 11 96.6％ 12.1％ Example 12 96.6％ 12.1％ Embodiment 13 96.5％ 12.2％ Embodiment 14 96.3％ 12.4％ Comparative Example 1 70.2％ 23.9％ Comparative Example 2 74.5％ 23.4％ Comparative Example 3 75.3％ 20.7％ Comparative Example 4 81.5％ 15.2％

[0109] In combination with Table 2, it can be seen from Examples 1 to 10 and Comparative Examples 1 to 4 that when the electrolyte does not contain the compound of formula (I) and the compound of formula (II) (for example, Comparative Example 1), the high temperature cycle capacity retention rate of the lithium ion battery is low, and the high temperature storage volume expansion rate is high; when only the compound of formula (I) is added to the electrolyte (for example, Comparative Example 2), although the high temperature cycle capacity retention rate of the lithium ion battery is slightly improved, the high temperature storage volume expansion rate is still high, indicating that the addition of the compound of formula (I) alone has limited effect on improving the high temperature cycle performance and high temperature storage stability of the lithium ion battery; when only the compound of formula (II) is added to the electrolyte (for example, Comparative Example 3), although the high temperature cycle capacity retention rate of the lithium ion battery is slightly improved, the high temperature storage volume expansion rate is still high. The expansion rate is still high, indicating that the addition of the compound of formula (II) alone has limited effect on improving the high temperature cycle performance and high temperature storage stability of the lithium ion battery; when the addition amount of the compound of formula (I) and the compound of formula (II) in the electrolyte is too high (for example, Comparative Example 4), although the high temperature cycle performance of the lithium ion battery is improved to a certain extent, and the high temperature storage volume expansion rate is reduced to a certain extent, the improvement effect on the high temperature cycle performance and high temperature storage performance is still limited. This may be because an excess of the compound of formula (I) is more likely to increase the impedance of the SEI film, resulting in easier lithium precipitation at the negative electrode interface during the cycle, thereby resulting in loss of active lithium, while an excess of the compound of formula (II) is likely to lead to an increase in side reactions, thereby resulting in an increase in gas production, thereby affecting the high temperature cycle performance and high temperature storage performance of the lithium ion battery.

[0110] The electrolyte of the present application includes a compound of formula (I) and a compound of formula (II), and when the contents of the two compounds are regulated within the scope of the present application, the high-temperature cycle capacity retention rate of the lithium-ion battery is significantly improved, and the high-temperature storage volume expansion rate is significantly reduced, indicating that the synergistic effect of the compound of formula (I) and the compound of formula (II) can optimize the improvement effect on high-temperature storage stability and high-temperature cycle performance, so that the lithium-ion battery exhibits excellent high-temperature cycle performance and high-temperature storage stability.

[0111] It can also be seen from Examples 1 to 8 and Examples 9 to 10 that, based on the content of the compound of formula (I) and the compound of formula (II) in the electrolyte within the scope of the present application, by regulating a / b within the scope of the present application, it is beneficial for the lithium-ion battery to exhibit better warm cycle performance and high temperature storage stability.

[0112] The types of the compound of formula (I) and the compound of formula (II) will generally also have an impact on the performance of the lithium-ion battery. It can also be seen from Example 1 and Example 11 to Example 14 that by regulating the types of the compound of formula (I) and the compound of formula (II) within the scope of this application, it is beneficial to obtain a lithium-ion battery with excellent high-temperature cycle performance and high-temperature storage stability.

[0113] The above is a detailed introduction to an electrolyte, a battery containing the electrolyte, an energy storage device and an electrical equipment disclosed in the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for general technicians in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. An electrolyte, characterized in that: Including compounds of formula (I) and compounds of formula (II): In formula (I), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, an alkyl group, or an amide group, and at least one of R1 to R5 is an amide group; In formula (II), R6 is selected from alkyl or vinyl; Based on the mass of the electrolyte, the mass percentage of the compound of formula (I) is a, the mass percentage of the compound of formula (II) is b, 0.1%≤a≤1%, and 0.1%≤b≤3%.

2. The electrolyte according to claim 1, characterized in that 0.5％≤b≤2％。 3. The electrolyte according to claim 1, characterized in that 0.1≤a / b≤1.

5.

4. The electrolyte according to claim 1, characterized in that The compound of formula (I) is selected from at least one of the following compounds:

5. The electrolyte according to claim 1, characterized in that The compound of formula (II) is selected from at least one of the following compounds:

6. The electrolyte according to claim 1, characterized in that The electrolyte further comprises cyclic carbonate and chain carbonate, wherein the cyclic carbonate comprises at least one of ethylene carbonate and propylene carbonate; and the chain carbonate comprises at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

7. A battery, characterized in that: The electrolyte comprises the electrolyte described in any one of claims 1 to 6.

8. The battery according to claim 7, characterized in that The battery further comprises a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode material layer, wherein the negative electrode material layer comprises a negative electrode active material, wherein the negative electrode active material comprises graphite, wherein the mass percentage content of the compound of formula (I) in the electrolyte is a, and the Dv10 of the graphite satisfies a:

9. The battery according to claim 8, characterized in that The Dv10 of the graphite is 5 μm to 10 μm.

10. An energy storage device, characterized in that: The invention comprises a casing and at least one battery according to claim 9, wherein the battery is accommodated in the casing.

11. An electrical device, characterized in that: It includes the energy storage device as described in claim 10, and the energy storage device supplies power to the electrical equipment.

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