Electrolyte, battery, energy storage device and electric equipment comprising the same

Abstract

The application provides an electrolyte, a battery, an energy storage device and an electric device comprising the electrolyte, wherein the electrolyte comprises a first additive, and the first additive is a compound shown in formula (I). In formula (I), R1, R2, R3, R4 and R5 are each independently selected from hydrogen, a halogen atom, a cyano group, an amino group, an unsubstituted or Ra-substituted C 1~10 alkyl group, an unsubstituted or Ra-substituted C 2~10 alkenyl group, an unsubstituted or Ra-substituted C 6~16 aryl group; Ra is at least one selected from an acyl group, a carbonyl group, an ether group or a halogen atom; the mass percentage content of the first additive is a, 0.02%≤a≤4%, based on the mass of the electrolyte.

Description

Technical Field

[0001] This 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 appliance. Background Technology

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

[0003] As people's requirements for the performance of secondary batteries increase, such as the performance requirements for secondary batteries in energy storage scenarios, not only are high energy density required, but also good high-temperature performance is required, such as high-temperature cycle performance and high-temperature storage performance, to ensure the service life of secondary batteries in high-temperature energy storage applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this application discloses an electrolyte, a battery containing the electrolyte, an energy storage device, and an electrical appliance, in order to improve the high-temperature cycle performance and high-temperature storage performance of secondary batteries.

[0005] In a first aspect, this application provides an electrolyte comprising a first additive, wherein the first additive is a compound of formula (I):

[0006]

[0007] In formula (Ⅰ), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, halogen atoms, cyano groups, amino groups, unsubstituted or Ra-substituted C atoms. 1~10 Alkyl, unsubstituted or Ra-substituted C 2~10 Alkenyl, unsubstituted or Ra-substituted C 6~16 One of the aryl groups; Ra is selected from at least one of acyl, carbonyl, ether, or halogen atoms; based on the mass of the electrolyte, the mass percentage of the first additive is a, 0.02% ≤ a ≤ 4%.

[0008] In some embodiments of this application, 0.05% ≤ a ≤ 0.8%.

[0009] In some embodiments of this application, the first additive is selected from at least one of the following compounds:

[0010] , , , ,

[0011] , .

[0012] In some embodiments of this application, the electrolyte further includes a second additive selected from at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate.

[0013] In some embodiments of this application, the mass percentage of the second additive is b, based on the mass of the electrolyte, where 0.1% ≤ b ≤ 20%.

[0014] In some embodiments of this application, 1% ≤ b ≤ 10%.

[0015] In some embodiments of this application, 0.05 ≤ a / b ≤ 2.

[0016] Secondly, this application provides a battery comprising the electrolyte described in the first aspect.

[0017] Thirdly, this application provides an energy storage device, including a housing and at least one battery as described in the second aspect, the battery being housed within the housing.

[0018] Fourthly, this application provides an electrical device including the energy storage device described in the third aspect, wherein the energy storage device supplies power to the electrical device.

[0019] Compared with the prior art, this application has at least the following beneficial effects:

[0020] This application provides an electrolyte, a battery containing the electrolyte, an energy storage device, and an electrical device. The electrolyte includes a first additive, which is a compound represented by formula (I). Based on the mass of the electrolyte, the mass percentage of the first additive is 'a', where 0.02% ≤ a ≤ 4%. The electrolyte of this application contains the aforementioned first additive, and by adjusting the content of the first additive within the scope of this application, the high-temperature cycle performance and high-temperature storage performance of the secondary battery are improved. When the secondary battery of this application is used in an energy storage device, it improves the service life of the energy storage device in high-temperature energy storage application scenarios. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application;

[0023] Figure 2This is a schematic diagram of the energy storage system according to another embodiment of this application;

[0024] Figure 3 This is a schematic diagram of the energy storage system according to another embodiment of this application.

[0025] Explanation of reference numerals in the attached drawings: 400-Energy storage system, 410-First power conversion device, 420-First user load, 430-Second user load, 440-Energy storage device, 450-High voltage cable, 460-Second power conversion device, 470-Vehicle, 480-Photovoltaic-energy storage-charging station. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0028] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0029] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0030] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0031] It should be noted that this application uses lithium-ion batteries as an example of secondary batteries to explain the application, but the secondary batteries in this application are not limited to lithium-ion batteries.

[0032] This application provides an electrolyte comprising a first additive, wherein the first additive is a compound of formula (I):

[0033]

[0034] In formula (Ⅰ), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, halogen atoms, cyano groups, amino groups, unsubstituted or Ra-substituted C atoms. 1~10 Alkyl, unsubstituted or Ra-substituted C 2~10 Alkenyl, unsubstituted or Ra-substituted C 6~16 One of the aryl groups; Ra is selected from at least one of the acyl, carbonyl, ether, or halogen atom;

[0035] Based on the mass of the electrolyte, the mass percentage of the first additive is 'a', where 0.02% ≤ a ≤ 4%; in another alternative embodiment, 0.05% ≤ a ≤ 0.8%. For example, a can be 0.02%, 0.04%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%.

[0036] The inventors discovered that when the electrolyte contains a first additive, namely the compound shown in formula (I), the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries are improved. This may be because the compound shown in formula (I) contains a pyridine ring structure and a triazolone structure. The nitrogen atom and carbonyl group in the triazolone structure are more electronegative and more likely to attract electrons, thereby weakening the conjugation effect of the pyridine ring structure. Correspondingly, the pyridine ring structure also affects the charge distribution of the triazolone structure. Under the interaction of the two ring structures mentioned above, the charge redistribution and electron cloud density in the compound shown in formula (I) change, so that the compound shown in formula (I) has a higher highest occupied molecular orbital (HOMO) energy level and a lower lowest unoccupied molecular orbital (LUMO) energy level, making it more likely to undergo oxidation / reduction reactions and thus participate in film formation at the positive and negative electrodes of lithium-ion batteries. This allows for preferential reactions, thereby optimizing the structural composition of the CEI (Chemical-Electrochemical Interface) film on the positive electrode side and the SEI (Solid Electrolyte Interphase) film on the negative electrode side.

[0037] Further research by the inventors revealed that the content of the first additive in the electrolyte affects the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries. When the content of the first additive is too low (e.g., below 0.02%), it is difficult to optimize the structural composition of the CEI film on the positive electrode side and the SEI film on the negative electrode side, thus the improvement effect on the high-temperature cycle performance of lithium-ion batteries is not significant. When the content of the first additive is too high (e.g., above 4%), it leads to an increase in electrolyte impedance, which in turn affects the high-temperature cycle performance of lithium-ion batteries. By controlling the content of the first additive within the above range, it is beneficial to simultaneously improve the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries.

[0038] In some embodiments of this application, the first additive is selected from at least one of the following compounds:

[0039] , , , ,

[0040] , .

[0041] By selecting at least one of the compounds shown in formula (I-1) to formula (I-6), it is beneficial to improve the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries.

[0042] In some embodiments of this application, the electrolyte further includes a second additive selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and ethylene ethylene carbonate (VEC). The inclusion of the aforementioned second additive in the electrolyte is beneficial for further improving the cycle life of the lithium-ion battery.

[0043] In some embodiments of this application, the mass percentage of the second additive is b, based on the mass of the electrolyte, where 0.1% ≤ b ≤ 20%; in other embodiments, 1% ≤ b ≤ 10%. For example, b can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, or 20%. By controlling the content of the second additive within the above range, the second additive can synergistically interact with the first additive. Specifically, the first additive preferentially undergoes a reduction reaction to participate in the formation of the SEI film and inhibits the reduction reaction of the second additive. On the one hand, this optimizes the initial SEI film structure and increases the proportion of inorganic components in the SEI film, thereby improving the thermal stability of the SEI film. On the other hand, it reduces the initial consumption of the second additive, so that the second additive mainly plays a role in repairing the SEI film in the middle and late stages of charge-discharge cycles, compensating for the destructive effect of negative electrode volume changes on the SEI film during discharge, which is beneficial to further improving the high-temperature cycle life of lithium-ion batteries.

[0044] In some embodiments of this application, 0.05 ≤ a / b ≤ 2. For example, a / b is 0.05, 1, 1.2, 1.5, 1.8, or 2. By adjusting a / b within the above range, the first and second additives can work more synergistically, which is beneficial to further improving the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries.

[0045] The electrolyte of this application may further include an organic solvent. Exemplarily, the organic solvent includes at least one selected from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethyl acetate, ethyl propionate, and propyl propionate. This application does not impose any particular limitation on the content of the organic solvent; for example, the mass percentage of the organic solvent in the electrolyte may be 60% to 90%.

[0046] This application does not impose any particular restrictions on the preparation process of the electrolyte. For example, the above-mentioned organic solvents can be mixed in a certain mass ratio or volume ratio, then lithium salt can be added to dissolve and mix evenly, and then electrolyte additives such as the electrolyte additives of this application can be added and dissolved.

[0047] This application does not impose any particular limitation on lithium salts. For example, lithium salts include at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorosulfonylimide, lithium difluorooxalate borate (LiODFB), lithium bis(oxalate borate) borate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), and lithium trifluoromethanesulfonate (CF3SO3Li).

[0048] This application does not impose any particular limitation on the concentration of lithium salt in the electrolyte, as long as it achieves the purpose of this application. Taking LiPF6 as an example, the concentration of LiPF6 in the electrolyte is 0.6 mol / L to 2.0 mol / L. For example, the concentration of LiPF6 can be 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, or any range thereof.

[0049] This application also provides a battery including the electrolyte described in any embodiment of this application.

[0050] The lithium-ion battery of this application also includes a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode and plays a role in isolation.

[0051] This application does not impose any particular limitation on the positive electrode sheet, as long as it achieves the purpose of this application. For example, the positive electrode sheet typically includes a positive current collector and a positive active material layer. The positive active material layer can be disposed on one surface or on two surfaces in the thickness direction of the positive current collector. In this application, the positive active material layer is disposed on the surface of the positive current collector, that is, the positive active material layer can be disposed on a portion of a surface of the positive current collector or on the entire surface of a surface of the positive current collector. This application does not impose any particular limitation on the positive current collector, as long as it achieves the purpose of this application, it can be, for example, including but not limited to aluminum foil, aluminum alloy foil, or composite current collectors. In this application, there is no particular limitation on the thickness of the positive current collector, as long as it achieves the purpose of this application, for example, a thickness of 8μm to 15μm. The single-sided thickness of the positive active material layer in this application can be 100μm to 300μm.

[0052] In this application, the positive electrode active material layer includes a positive electrode active material. This application does not have any particular restrictions on the positive electrode active material, as long as it can achieve the purpose of this application. 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 manganese iron phosphate.

[0053] In this application, the positive electrode active material layer may further include a positive electrode conductive agent. This application does not impose any particular limitation on the positive electrode conductive agent, as long as it can achieve the purpose of this application. 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 aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. In this application, the positive electrode active material layer may further include a positive electrode binder. This application does not impose any particular limitation on the positive electrode binder, as long as it can achieve the purpose of this application. For example, it may include, but is not limited to, at least one of fluorinated resins, polypropylene resins, fiber-type binders, rubber-type binders, or polyimide-type binders.

[0054] This application does not impose any particular limitation on the negative electrode sheet, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically includes a negative current collector and a negative active material layer. The negative active material layer can be disposed on one or both surfaces of the negative current collector in the thickness direction. In this application, the negative active material layer is disposed on the surface of the negative current collector, that is, the negative active material layer can be disposed on a portion of one surface of the negative current collector, or it can be disposed on the entire surface of one surface of the negative current collector. This application does not impose any particular limitation on the negative current collector, as long as it achieves the purpose of this application. For example, it can include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collectors. In this application, there is no particular limitation on the thickness of the negative current collector, as long as it achieves the purpose of this application, for example, a thickness of 4μm to 12μm. The single-sided thickness of the negative active material layer in this application can be 70μm to 200μm.

[0055] In this application, the negative electrode active material layer includes a negative electrode active material. There are no particular limitations on the negative electrode active material, as long as it can achieve the purpose of this application. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon, and silicon-carbon.

[0056] In this application, the negative electrode active material layer may also include a negative electrode binder. This application does not impose any particular limitation on the negative electrode binder, as long as it can achieve the purpose of this application. For example, it may include at least one of acrylate, polyamide, polyimide, polyamide-imide, polyvinylidene fluoride (PVDF), styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose.

[0057] This application does not impose any particular limitation on the diaphragm; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved. For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane 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, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.

[0058] The battery of this application also includes a casing. This application does not impose any particular restrictions on the casing, and those skilled in the art can choose one according to actual needs, as long as it can achieve the purpose of this application. For example, the casing may include an aluminum-plastic film.

[0059] This application does not impose any particular limitation on the battery preparation method; any preparation method known in the art can be used, as long as it can achieve the purpose of this application. For example, the battery preparation method includes, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a bare cell with a wound structure; placing the bare cell in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the battery.

[0060] This application also provides an energy storage device, including a housing and at least one battery as described in any of the above embodiments, the battery being housed within the housing. The energy storage device with this battery exhibits excellent performance, which is beneficial for its use. Housing the battery within the housing increases its stability and protection, thereby extending the lifespan of the energy storage device. It is understood that the energy storage device may contain one or more batteries, and when the energy storage device contains multiple batteries, the multiple batteries can be connected in at least one manner, such as parallel or series connection.

[0061] This application also provides an electrical device including the energy storage device described in the above embodiments, which is beneficial for improving the product competitiveness and performance of the electrical device. In an optional embodiment, 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 embodiment, the electrical device body includes a positive terminal and a negative terminal, the positive electrode of the battery in the energy storage device is used to electrically connect to the positive terminal of the electrical device body, and the negative electrode of the battery in the energy storage device is used to electrically connect to the negative terminal of the electrical device body, so as to supply power to the electrical device.

[0062] The electrical equipment in this application may include, but is not limited to: prefabricated energy storage cabins, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. Among them, spacecraft include, for example, airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include, for example, stationary or mobile electric toys, specifically, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include, for example, metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, specifically, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0063] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels. The generation of green electricity currently relies heavily on photovoltaics, wind power, and hydropower. However, wind and solar energy generally suffer from strong intermittency and large fluctuations, which can cause grid instability, insufficient electricity during peak demand periods, and excessive electricity during off-peak periods. Unstable voltage can also damage power grids. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it, releasing it as electricity when needed. Simply put, energy storage is like a large "power bank," storing electrical energy when photovoltaic and wind power are abundant and releasing the stored electricity when needed.

[0064] Taking electrochemical energy storage as an example, this solution provides an energy storage device 440, which is applied to an energy storage system 400. The energy storage device 440 is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage medium. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage medium. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electrical energy is released for use, or transferred to places with a shortage of electricity for use.

[0065] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include:

[0066] (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation.

[0067] (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption.

[0068] (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0069] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 This application Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 440 of this application is not limited to the home energy storage scenario.

[0070] This application provides an energy storage system 400, which includes a first power conversion device 410 (photovoltaic panel), a first user load 420 (household lighting fixture), a second user load 430 (e.g., household appliances such as air conditioners), and an energy storage device 440. The energy storage device 440 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 440 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 440 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0071] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 1 And this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 440 of this application is not limited to the energy storage scenario on the generation / distribution side.

[0072] This application provides an energy storage system 400, which includes: a high-voltage cable 450, a first power conversion device 410, a second power conversion device 460, and an energy storage device 440 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 460 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 440 through grid connection. The energy storage device 440 is connected to the high-voltage cable and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power... The conversion device is always connected to the high-voltage cable. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 440 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 440 together with the high-voltage cable 450 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0073] In some embodiments on the distribution network side, the first power conversion device 410 can be a photovoltaic panel, and the energy storage device 440 is connected to the high-voltage cable 450 and installed downstream of the high-voltage cable 450 and between the user load. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 440, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 450 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0074] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 400 according to an embodiment of this application. Figure 3 And this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 440 of this application is not limited to industrial and commercial energy storage scenarios.

[0075] This application provides an energy storage system 400, which includes: an energy storage device 440, a high-voltage cable 450, a factory equipped with a first power conversion device 410, a photovoltaic-energy storage-charging station 480, and a vehicle 470. In some embodiments of industrial and commercial scenarios, the first power conversion device 410 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 440 in the factory. In the event of a power grid failure, the energy storage device 440 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 440 in conjunction with the high-voltage cable 450 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the first power conversion device 410 can also convert solar energy into electrical energy and store it in the energy storage device 440 of the photovoltaic-energy storage-charging station 480, which can then directly charge the vehicle 470, making it fast and convenient.

[0076] Optionally, the first power conversion device 410 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 460 may include, but is not limited to, a wind power conversion device. The first power conversion device 410 and the second power conversion device 460 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0077] Optionally, the energy storage device 440 may include, but is not limited to, energy storage applications such as energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and may also be applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0078] Optionally, the energy storage device 440 may include, but is not limited to, individual batteries, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage compartments, and other battery integrated systems composed of individual batteries. The actual application form of the energy storage device 440 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 440.

[0079] Optionally, the individual cell can be, but is not limited to, at least one of cylindrical, prismatic, prismatic, or other shaped cells.

[0080] Optionally, the single cell can be a rechargeable battery, which refers to a single cell that can be recharged after discharge to activate the active materials and continue to be used. The single cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0081] Example

[0082] The following examples, embodiments, and comparative examples illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0083] Example 1

[0084] <Preparation of the positive electrode>

[0085] Lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and PVDF binder were mixed at a mass ratio of 94:3:3. Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 60 wt%, which was stirred evenly. The positive electrode slurry was then uniformly coated onto one surface of a 10 μm thick aluminum foil current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet was obtained. The single-sided thickness of the positive electrode active material layer was 100 μm.

[0086] <Preparation of Negative Electrode Sheets>

[0087] Artificial graphite (anode active material), sodium carboxymethyl cellulose (CMC-Na) thickener, Super-P conductive carbon black, and styrene-butadiene rubber (SBR) binder were mixed in a mass ratio of 96:2:1:1. Deionized water was added to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred evenly. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil current collector. After drying, cold pressing, slitting, and cutting, the negative electrode sheet was obtained. The single-sided thickness of the negative electrode active material layer was 70 μm.

[0088] <Preparation of Electrolyte>

[0089] In an argon-atmospheric glove box with a moisture content ≤1ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 1:2:1. Lithium salt LiPF6 was then added and dissolved in the solvent. The mixture was stirred until the lithium salt was completely dissolved. Next, the first additive was added, and the mixture was thoroughly mixed to obtain the electrolyte. The types and amounts of the first additive are shown in Table 1, and the content of LiPF6 in the electrolyte was 1 mol / L.

[0090] <Preparation of the diaphragm>

[0091] A porous polyethylene (PE) membrane with a thickness of 16 μm was used as the separator.

[0092] <Preparation of Lithium-ion Batteries>

[0093] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting cells are then wound to obtain a bare battery cell. The bare battery cell is placed in an aluminum-plastic film packaging bag, vacuum dried, and then injected with electrolyte. After vacuum sealing, settling, and formation processes, a lithium-ion battery is obtained.

[0094] Examples 2 to 14

[0095] Except for adjusting the type and content of the first additive according to Table 1 in the <Preparation of Electrolyte> section, the rest is the same as in Example 1.

[0096] Examples 15 to 21

[0097] Except for the addition of a second additive to the electrolyte in the <Preparation of Electrolyte> section, and the adjustment of the type and content of the second additive according to Table 1, the rest is the same as in Example 14.

[0098] Examples 22-25

[0099] Except for adjusting the types and contents of the first and second additives according to Table 1 in the <Preparation of Electrolyte> section, the rest is the same as in Example 15.

[0100] Comparative Example 1

[0101] Except for the omission of the first additive in the <Preparation of Electrolyte>, the rest is the same as in Example 1.

[0102] Comparative Examples 2 to 3

[0103] Except for adjusting the content of the first additive according to Table 1 in the <Preparation of Electrolyte>, the rest is the same as in Example 1.

[0104] Table 1: Preparation parameters for each example and comparative example

[0105]

[0106] Note: In Table 1, " / " indicates that the relevant preparation parameters do not exist.

[0107] Test methods and equipment:

[0108] High-temperature cycling performance test:

[0109] The lithium-ion battery was left to stand for 5 hours at 45℃, then charged at a rate of 0.5P to 3.65V, left to stand for 10 minutes, then discharged at a rate of 0.5P to 2.5V, and left to stand for another 10 minutes. This charge-discharge cycle was repeated 1000 times. The discharge capacity of the first charge-discharge cycle was recorded as C1, and the discharge capacity of the 1000th charge-discharge cycle was recorded as C2. 1000 Then the capacity retention rate of a lithium-ion battery after 1000 cycles = (C 1000 / C1)×100%.

[0110] High-temperature storage performance test:

[0111] First, the lithium-ion battery was left to stand for 5 hours at 25℃. Then, it was charged to 3.65V at a 0.5P rate, left to stand for 10 minutes, and then discharged to 2.5V at a 0.5P rate, left to stand for another 10 minutes. This charge-discharge process constituted one charge-discharge cycle, which was repeated twice. The discharge capacity of the second charge-discharge cycle was recorded as the initial capacity C0. Next, the lithium-ion battery was fully charged to 3.65V at 25℃. Then, the fully charged lithium-ion battery was left to stand for 30 days at 45℃. Finally, the lithium-ion battery was left to stand for 5 hours at 25℃, and then discharged to 2.5V at a 0.5P rate. The discharge capacity was recorded as C0. 30 The capacity retention rate of a lithium-ion battery after 30 days of high-temperature storage = (C 30 / C0)×100%.

[0112] Table 2: Performance data of each embodiment and comparative example

[0113]

[0114] As can be seen from Examples 1-14 and Comparative Examples 1-3, when the electrolyte does not contain the first additive (e.g., Comparative Example 1), the capacity retention rate of the lithium-ion battery after 1000 high-temperature cycles and after 30 days of high-temperature storage is relatively low. When the content of the first additive in the electrolyte is too low (e.g., Comparative Example 2), the capacity retention rate of the lithium-ion battery after 1000 high-temperature cycles and after 30 days of high-temperature storage is also relatively low. This may be because a low content of the first additive makes it difficult to optimize the structural composition of the CEI film on the positive electrode side and the SEI film on the negative electrode side, thus reducing its effect on improving the high-temperature cycling performance of the lithium-ion battery. The effect is not obvious. When the content of the first additive in the electrolyte is too high (e.g., Comparative Example 3), the capacity retention rate of the lithium-ion battery after 1000 high-temperature cycles and after 30 days of high-temperature storage is also low. This may be because the excessive first additive increases the electrolyte impedance, which in turn affects the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery. However, when the content of the first additive in the electrolyte of this application is controlled within the range of this application, the capacity retention rate of the lithium-ion battery after 1000 high-temperature cycles and after 30 days of high-temperature storage is improved, which shows that the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery are improved.

[0115] As can be seen from Examples 14 and 15-21, when the electrolyte contains both the first additive and the second additive, the capacity retention rate of the lithium-ion battery after 1000 high-temperature cycles and after 30 days of high-temperature storage are further improved.

[0116] As can be seen from Examples 15 to 21, by further adjusting the amount of the second additive added to the electrolyte, it is beneficial to further improve the capacity retention rate of lithium-ion batteries after 1000 high-temperature cycles and after 30 days of high-temperature storage.

[0117] The type of the first additive and the type of the second additive also typically affect the performance of lithium-ion batteries. As can be seen from Examples 1, 8-12, and 22-25, by selecting the first additive and the second additive of this application, it is beneficial to obtain lithium-ion batteries with excellent high-temperature cycle performance and high-temperature storage performance.

[0118] The present application discloses an electrolyte, a battery containing the electrolyte, an energy storage device, and an electrical device. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of the present application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present application. Therefore, the content of this specification should not be construed as a limitation of the present application.

Claims

1. An electrolyte for use in secondary batteries, characterized in that, Includes a first additive, which is a compound of formula (I): In formula (Ⅰ), R1, R2, R3, R4, and R5 are each independently selected from hydrogen, halogen atoms, cyano groups, amino groups, unsubstituted or Ra-substituted C atoms. 1~10 Alkyl, unsubstituted or Ra-substituted C 2~10 Alkenyl, unsubstituted or Ra-substituted C 6~16 One of the aryl groups; Ra is selected from at least one of the acyl, carbonyl, ether, or halogen atom; Based on the mass of the electrolyte, the mass percentage of the first additive is a, where 0.02% ≤ a ≤ 4%.

2. The electrolyte according to claim 1, characterized in that, 0.05%≤a≤0.8%。 3. The electrolyte according to claim 1, characterized in that, The first additive is selected from at least one of the following compounds: 、 、 、 、 、 。 4. The electrolyte according to claim 1, characterized in that, The electrolyte further includes a second additive, which is selected from at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate.

5. The electrolyte according to claim 4, characterized in that, Based on the mass of the electrolyte, the mass percentage of the second additive is b, where 0.1% ≤ b ≤ 20%.

6. The electrolyte according to claim 5, characterized in that, 1%≤b≤10%。 7. The electrolyte according to claim 5, characterized in that, 0.05≤a / b≤2.

8. A battery, characterized in that, Includes the electrolyte for use in secondary batteries as described in any one of claims 1 to 7.

9. An energy storage device, characterized in that, It includes a housing and at least one battery as described in claim 8, the battery being housed within the housing.

10. An electrical appliance, characterized in that, The device includes the energy storage device of claim 9, wherein the energy storage device supplies power to the electrical equipment.

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