Electrolyte, secondary battery, energy storage device and electric equipment

Abstract

The invention provides an electrolyte, a secondary battery, an energy storage device and electric equipment, the electrolyte comprises an additive, and the additive is a compound as shown in a formula (I). In the formula (I), X1, X2, X3 and X4 are respectively and independently selected from carbon atoms or nitrogen atoms, at least two of X1, X2, X3 and X4 are nitrogen atoms, at least one of X1 and X2 is a nitrogen atom, R1 and R2 are respectively and independently selected from at least one of hydrogen atoms, alkyl, amino, benzene rings and trifluoromethyl, and R3 and R4 are respectively and independently selected from at least one of hydrogen atoms, alkyl, amino, benzene rings, double-bond oxygen, double-bond sulfur and trifluoromethyl.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an electrolyte, a secondary battery, an energy storage device, and an electrical appliance. Background Technology

[0002] With the continuous development of rechargeable battery technology, users' requirements for battery performance are also constantly increasing. In order to meet the growing and diversified application needs, it is necessary to develop rechargeable batteries that have both long lifespan and wide temperature range characteristics. Summary of the Invention

[0003] To address the aforementioned technical problems, this application discloses an electrolyte, a secondary battery, an energy storage device, and an electrical appliance, in order to improve the room temperature and high temperature cycling performance of the secondary battery, thereby enabling the secondary battery to have long lifespan and wide temperature range.

[0004] In a first aspect, this application provides an electrolyte comprising an additive, the additive being a compound of formula (I):

[0005]

[0006] In formula (Ⅰ), X1, X2, X3, and X4 are each independently selected from carbon atoms or nitrogen atoms, and at least two of X1, X2, X3, and X4 are nitrogen atoms, and at least one of X1 and X2 is a nitrogen atom. R1 and R2 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, and trifluoromethyl groups. R3 and R4 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, double-bonded oxygen, double-bonded sulfur, and trifluoromethyl groups.

[0007] Preferably, based on the mass of the electrolyte, the mass percentage of the additive is a, where 0.1% ≤ a ≤ 10%.

[0008] More preferably, 0.2% ≤ a ≤ 1%.

[0009] Preferably, in the additive, one of X1 and X2 is a nitrogen atom and the other is a carbon atom. Optionally, the additive is selected from at least one of the following compounds:

[0010]

[0011] Preferably, the additive is selected from at least one of the following compounds:

[0012]

[0013] More preferably, the additive is:

[0014]

[0015] Secondly, this application provides a battery comprising the electrolyte described in the first aspect.

[0016] 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.

[0017] 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.

[0018] Compared with the prior art, this application has at least the following beneficial effects:

[0019] In the electrolyte of this application embodiment, by adding the compound shown in formula (I), the room temperature cycling performance and high temperature cycling performance of the lithium-ion battery can be improved. In other words, the lithium-ion battery can maintain good cycle stability over a wide temperature range, thereby giving the lithium-ion battery the advantages of long life and wide temperature range, expanding its applicability, and making it particularly suitable for large-scale energy storage. The compound shown in formula (I) can act as a preferential reductive decomposition film-forming additive, optimizing the SEI (Solid Electrolyte Interphase) film structure at the negative electrode interface and improving interface stability. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a schematic diagram of the structure of an energy storage system according to one embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the energy storage system according to another embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the energy storage system according to another embodiment of this application.

[0024] 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

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (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, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0030] 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.

[0031] This application provides an electrolyte comprising an additive, wherein the additive is a compound of formula (I):

[0032]

[0033] In formula (Ⅰ), X1, X2, X3, and X4 are each independently selected from carbon atoms or nitrogen atoms, and at least two of X1, X2, X3, and X4 are nitrogen atoms, and at least one of X1 and X2 is a nitrogen atom. R1 and R2 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, and trifluoromethyl groups. R3 and R4 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, double-bonded oxygen, double-bonded sulfur, and trifluoromethyl groups.

[0034] In this context, double-bonded oxygen and double-bonded sulfur refer to functional groups R whose corresponding elements are oxygen or sulfur, and where a double bond is formed between R and the corresponding functional group X. For example, if X3 is a carbon atom and R3 is a double-bonded oxygen, then X3-R3 forms a carbonyl group; if X3 is a carbon atom and R3 is a double-bonded sulfur, then X3-R3 forms a sulfur carbonyl group.

[0035] In the electrolyte of this application embodiment, by adding the compound shown in formula (I), the room temperature cycling performance and high temperature cycling performance of the lithium-ion battery can be improved. In other words, the lithium-ion battery can maintain good cycle stability over a wide temperature range, leveraging its long lifespan and wide temperature range advantages, thus broadening its application scenarios (especially suitable for large-scale energy storage). The compound shown in formula (I) can act as a preferential reductive decomposition film-forming additive, preferentially forming a film and suppressing the decomposition and consumption of solvent components in the electrolyte to reduce active lithium loss. Furthermore, based on preferential film formation, it can improve the SEI (Solid Electrolyte Interphase) film structure at the negative electrode interface, enhancing interface stability and thereby promoting improved room temperature and high temperature cycling performance of the lithium-ion battery.

[0036] On the one hand, the compound shown in formula (I) contains adjacent intracyclic double bonds (X1 = X2) and exocyclic double bonds (C = O). These two double bonds can form a conjugated structure to lower the molecular HOMO energy level, making the additive preferentially decomposed over conventional film-forming additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC), and inhibiting the decomposition and consumption of solvents such as ethylene carbonate (EC), thus reducing the loss of active lithium. On the other hand, at least one end of the aforementioned intracyclic double bond (X1 = X2) is a nitrogen atom, which can introduce highly stable nitrogen-containing components into the SEI film generated by reductive decomposition, thereby improving the stability of the film-forming interface based on preferential film formation. Through the combined effect of the above two aspects, the electrolyte used in lithium-ion batteries can effectively improve the room temperature cycle performance and high temperature cycle performance of lithium-ion batteries.

[0037] Based on the mass of the electrolyte, the mass percentage of the additive is 'a'. Preferably, 0.1% ≤ a ≤ 10%; more preferably, 0.2% ≤ a ≤ 1%; most preferably, a is 0.5%. Exemplarily, a is 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0038] In this embodiment, controlling the mass percentage 'a' of the additive within the range of 0.1% to 10% results in better improvement of the room temperature and high temperature cycle performance of lithium-ion batteries. The improvement is even more pronounced when 'a' is further controlled within the range of 0.2% to 1%. The best improvement is achieved when 'a' is 0.5%.

[0039] Optionally, in the embodiments of this application, the additives X1 and X2 may be one of nitrogen atoms and the other of carbon atoms, in which case at least one of X3 and X4 is a nitrogen atom; the additives X1 and X2 may also be both nitrogen atoms, in which case X3 and X4 may not contain nitrogen atoms, or may contain one or two nitrogen atoms.

[0040] Preferably, in the embodiments of this application, one of X1 and X2 is a nitrogen atom and the other is a carbon atom. Compared with the case where both X1 and X2 of the additive are nitrogen atoms, when one of X1 and X2 of the additive is a nitrogen atom, it is beneficial to better balance the performance of SEI film stability, electrolyte impedance, electrolyte solubility, etc. This allows the electrolyte to introduce an appropriate amount of inorganic components into the SEI film to enhance its stability, without causing an excessively high proportion of nitrogen in the intracyclic double bond (X1=X2), which would lead to increased impedance and decreased solubility, thus affecting the cycle performance of the lithium-ion battery.

[0041] In some embodiments of this application, the additive is selected from at least one of the following compounds:

[0042]

[0043]

[0044] By selecting at least one of the compounds shown in formula (I-1) to formula (I-14), it is beneficial to improve the room temperature cycle performance and high temperature cycle performance of lithium-ion batteries.

[0045] Preferably, the additive is selected from at least one of the following compounds:

[0046]

[0047] When any of R1-R4 in formula (I) of the additive is an amino group, firstly, amino groups exhibit better affinity for the electrolyte, which is beneficial for improving the solubility in the electrolyte; secondly, amino groups react well with Li... + It has a stronger binding capacity, which is more conducive to reducing the impedance of the electrolyte and improving the degree of improvement in both room temperature cycling performance and high temperature cycling performance.

[0048] More preferably, the additive is:

[0049]

[0050] In formula (I-8), R2 is an amino group adjacent to the double bond in the ring. Since this amino group can form an electron-donating conjugation effect with the C=N double bond in the ring, it is beneficial to further promote the preferential decomposition of the additive into a film, and the improvement of the room temperature cycle performance and high temperature cycle performance of lithium-ion batteries is more obvious.

[0051] 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%.

[0052] 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.

[0053] 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) (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), and lithium trifluoromethanesulfonate (CF3SO3Li).

[0054] 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.

[0055] This application also provides a battery including the electrolyte described in any embodiment of this application.

[0056] 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.

[0057] 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 13μm. The single-sided thickness of the positive active material layer in this application can be 100μm to 200μm.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The electrical equipment in this application may include, but is not limited to: containers, 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.

[0069] 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 for future applications. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0070] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. 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. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0071] 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.

[0072] 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 440 include:

[0073] (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 source in 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.

[0074] (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.

[0075] (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 charges. 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.

[0076] 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.

[0077] 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.

[0078] 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 2 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Optionally, the individual cell can be, but is not limited to, at least one of cylindrical, prismatic, prismatic, or other shaped cells.

[0087] 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.

[0088] Example

[0089] 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.

[0090] Example 1

[0091] <Preparation of the positive electrode>

[0092] Lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and PVDF binder were mixed at a mass ratio of 97:0.7:2.3. Then, N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode slurry with a solid content of 60 wt%. The mixture was stirred until homogeneous, and then the positive electrode slurry was uniformly coated onto one surface of a 15 μm thick aluminum foil current collector. The coating weight of the positive electrode slurry was 300 mg / 1540.25 mm. 2 After drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0093] <Preparation of Negative Electrode Sheets>

[0094] 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 96:1:1:2. 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 then uniformly coated onto one surface of an 8 μm thick copper foil current collector. The coating weight of the negative electrode slurry was 144 mg / 1540.25 mm. 2 After drying, cold pressing, slitting, and cutting, the negative electrode sheet is obtained.

[0095] <Preparation of Electrolyte>

[0096] In an argon-atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed at a mass ratio of 1:1:2. Lithium salt LiPF6 was then added and dissolved in the solvent. The mixture was stirred until the lithium salt was completely dissolved. Additives were then added, and the mixture was thoroughly mixed to obtain the electrolyte. The types and amounts of additives are shown in Table 1. The content of LiPF6 in the electrolyte was 1 mol / L.

[0097] <Preparation of the diaphragm>

[0098] A 16μm thick polypropylene (PP) film was used as the separator.

[0099] <Preparation of Lithium-ion Batteries>

[0100] 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 bare cell is then wound. After welding, the cell is assembled into an outer packaging bag, vacuum dried, and then injected with electrolyte. Following vacuum sealing, settling, formation, and shaping processes, a lithium-ion battery is obtained.

[0101] Examples 2 to 20

[0102] Except for adjusting the types and contents of additives according to Table 1 in the <Preparation of Electrolyte> section, the rest is the same as in Example 1.

[0103] Comparative Example 1

[0104] Except for the fact that no additives were added in the <Preparation of Electrolyte>, the rest is the same as in Example 1.

[0105] Test method:

[0106] Room temperature cycling performance test:

[0107] At 25℃, the lithium-ion battery was left to stand for 5 hours, 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 process constituted one charge-discharge cycle, and a total of 1000 cycles were performed. 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%.

[0108] High-temperature cycling performance test:

[0109] The lithium-ion battery was left to stand for 5 hours at 45℃, then charged at a 1P rate to 3.65V, left to stand for 10 minutes, then discharged at a 1P rate 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] The test results are shown in Table 1.

[0111] Table 1: Preparation parameters and performance data of each embodiment and comparative example

[0112]

[0113] Note: 1. In Table 1, " / " indicates that there are no relevant preparation parameters.

[0114] 2. The molecular formulas of each additive are as follows:

[0115]

[0116] By comparing Comparative Example 1 and Examples 1 to 20, it can be seen that after adding the additives of the present application embodiments to the electrolyte, the capacity retention rate of the lithium-ion battery after 1000 cycles at 25°C and 45°C is significantly improved. This indicates that the electrolyte of the present application embodiments can enable the applied lithium-ion battery to have the advantages of long life and wide temperature range, which can meet a wider range of application scenarios.

[0117] By comparing Examples 1 to 7, Example 11, and Examples 15 to 20, it can be seen that, under the same additive dosage, the lithium-ion batteries of Examples 6 and 11 have better wide-temperature capacity retention. Additives (I-6) and (I-8) corresponding to these two examples are preferred additives. Specifically, the capacity retention rate after 1000 cycles at 25°C and 45°C both reached over 90%. This indicates that when any of R1-R4 in formula (I) of the electrolyte additive is amino, the improvement in room-temperature and high-temperature cycling performance can be further enhanced. More preferably, additive (I-8) has a more prominent effect on improving the wide-temperature capacity retention rate of lithium-ion batteries, specifically with capacity retention rates of 98% and 95% after 1000 cycles at 25°C and 45°C, respectively. It is evident that when R2 is amino, the improvement in room-temperature and high-temperature cycling performance of lithium-ion batteries is more significant.

[0118] Comparative studies of Examples 8 to 14 show that controlling the mass percentage 'a' of the additive within the range of 0.1% to 10% results in better improvement of the room temperature and high temperature cycle performance of lithium-ion batteries. The improvement is even more pronounced when 'a' is further controlled within the range of 0.2% to 1%. The best improvement is achieved when 'a' is 0.5%.

[0119] The technical solutions disclosed in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this 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 this 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 this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte includes an additive, which is a compound of formula (I): In formula (Ⅰ), X1, X2, X3, and X4 are each independently selected from carbon atoms or nitrogen atoms, and at least two of X1, X2, X3, and X4 are nitrogen atoms, and at least one of X1 and X2 is a nitrogen atom. R1 and R2 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, and trifluoromethyl groups. R3 and R4 are each independently selected from at least one of hydrogen atoms, alkyl groups, amino groups, benzene rings, double-bonded oxygen, double-bonded sulfur, and trifluoromethyl groups.

2. The electrolyte according to claim 1, characterized in that, Based on the mass of the electrolyte, the mass percentage of the additive is a, where 0.1% ≤ a ≤ 10%.

3. The electrolyte according to claim 1, characterized in that, 0.2％≤a≤1％。 4. The electrolyte according to claim 1, characterized in that, In the additive, one of X1 and X2 is a nitrogen atom and the other is a carbon atom.

5. The electrolyte according to any one of claims 1 to 4, characterized in that, The additive is selected from at least one of the following compounds:

6. The electrolyte according to claim 5, characterized in that, The additive is selected from at least one of the following compounds:

7. The electrolyte according to claim 6, characterized in that, The additive is:

8. A battery, characterized in that, Includes the electrolyte 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 is configured to supply power to the electrical equipment.

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