Electrolyte, sodium ion battery, battery module, battery pack and electric device

Abstract

The invention provides an electrolyte, a sodium ion battery, a battery module, a battery pack and a power utilization device, the electrolyte comprises a sodium salt and an organic solvent, the organic solvent comprises a fluorinated organic matter, an ether organic matter and a coordination organic matter, and the coordination organic matter contains a plurality of functional groups capable of being coordinated with transition metal. The electrolyte provided by the invention can improve the cycle performance of the sodium-ion battery in a high-temperature environment.

Description

Electrolyte, sodium-ion battery, battery module, battery pack and power-consuming device Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to an electrolyte, a sodium ion battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] At present, the storage capacity of non-renewable energy is no longer sufficient to support the rapid development of industries such as industry and agriculture, so new energy has developed rapidly. Among them, batteries used to store electrical energy (such as lithium-ion batteries, sodium-ion batteries, etc.) have gradually become one of the most widely used new energy sources.

[0003] However, in the related art, the cycle performance of sodium ion batteries will decrease in high temperature environments, which greatly limits the application of sodium ion batteries in high temperature environments.

[0004] Summary of the Invention

[0005] The present application provides an electrolyte, a sodium ion battery, a battery module, a battery pack and an electrical device. The electrolyte can improve the cycle performance of the sodium ion battery in a high temperature environment.

[0006] In a first aspect, an embodiment of the present application provides an electrolyte comprising a sodium salt and an organic solvent, wherein the organic solvent comprises a fluorinated organic compound, an ether organic compound, and a coordinated organic compound, wherein the coordinated organic compound contains multiple functional groups capable of coordinating with a transition metal.

[0007] In the electrolyte provided by the embodiment of the present application, under high temperature environmental conditions, the fluorinated organic compound and the coordinated organic compound can be co-dissolved in the ether organic compound and act synergistically to form a stable solid electrolyte interface film on the electrode surface. On the one hand, the fluorinated organic compound can help form a stable solid electrolyte interface film on the surface of the electrode pole piece to reduce the formation of sodium dendrites, thereby improving the cycle performance of the sodium ion battery; on the other hand, the transition metal dissolved from the electrode pole piece under high temperature environment can coordinate with the functional groups in the coordinated organic compound, reducing the damage of the transition metal to the solid electrolyte interface film, thereby improving the stability of the solid electrolyte interface film, and further improving the stability of the cycle performance of the sodium ion battery. Therefore, the electrolyte provided by the embodiment of the present application can improve the cycle performance of the sodium ion battery under high temperature environment.

[0008] According to any of the foregoing embodiments of the first aspect of the present application, the fluorinated organic compound includes a fluorinated carbonate and / or a fluorinated ether. The fluorinated carbonate and fluorinated ether can help form a sodium fluoride-rich solid electrolyte interface film on the surface of the electrode plate, thereby further improving the stability of the solid electrolyte interface film, effectively reducing the formation of sodium dendrites, and further improving the cycling performance of the sodium-ion battery.

[0009] According to any of the aforementioned embodiments of the first aspect of the present application, the fluorinated carbonate comprises a fluorinated linear carbonate and / or a fluorinated cyclic carbonate. The fluorinated linear carbonate comprises at least one of trifluoromethyl ethyl carbonate, trifluoromethyl propyl carbonate, two (trifluoromethyl) carbonate and two (2,2,2-trifluoroethyl) carbonate. The fluorinated cyclic carbonate comprises at least one of fluoroethylene carbonate, fluoropropylene carbonate and fluorobutylene carbonate.

[0010] According to any of the foregoing embodiments of the first aspect of the present application, the fluoroether includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl)ether, methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether.

[0011] According to any of the foregoing embodiments of the first aspect of the present application, the ether organic compound includes at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol methylene ether, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether. The ether organic compound can help form a stable solid electrolyte interface film and reduce electrochemical polarization.

[0012] According to any of the aforementioned embodiments of the first aspect of the present application, the functional group is selected from a cyano group. The cyano group can impart good stability and strong coordination capacity to the coordinated organic compound, thereby facilitating the formation of a stable solid electrolyte interface film on the surface of the electrode plate, thereby further improving the cycling performance of the sodium-ion battery.

[0013] According to any of the aforementioned embodiments of the first aspect of the present application, the coordinating organic compound includes at least one of 1,3,6-hexanetrinitrile, 1,3,5-pentanetrinitrile, succinonitrile, glutaronitrile, adiponitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, tricyanobenzene, and 1,2-bis(cyanoethoxy)ethane.

[0014] According to any of the aforementioned embodiments of the first aspect of the present application, based on the total volume of the organic solvent, the volume percentage of the fluorinated organic compound in the organic solvent is 5%-30%; the volume percentage of the ether organic compound in the organic solvent is 55%-93%; and the volume percentage of the coordinating organic compound in the organic solvent is 2%-15%. Setting the components of the organic solvent within the aforementioned suitable ranges can facilitate synergistic effects between the components, thereby significantly improving the cycling performance of the sodium-ion battery in a high-temperature environment.

[0015] According to any of the foregoing embodiments of the first aspect of the present application, the sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium bis(oxalate) borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0016] In a second aspect, an embodiment of the present application provides a sodium-ion battery, including the electrolyte according to any of the embodiments of the first aspect of the present application.

[0017] According to any of the foregoing embodiments of the second aspect of the present application, it further includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material, and the positive electrode active material includes at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0018] According to any of the foregoing embodiments of the second aspect of the present application, the sodium transition metal oxide has a general formula Na x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1; the polyanionic compound includes one or more of vanadium trifluorophosphate, sodium fluorophosphate vanadate, sodium vanadium phosphate, sodium iron phosphate, and Na4Fe3(PO4)2P2O7; the Prussian blue compound has a general formula Na y M 1 M 2 (CN)6, where M 1 and M 2 are each independently one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0 < y ≤ 2.

[0019] According to any of the foregoing embodiments of the second aspect of the present application, it further includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material, and the negative electrode active material includes at least one of carbon materials, metallic sodium, sodium alloys, and sodium metal oxides.

[0020] In a third aspect, an embodiment of the present application provides a battery module, including the sodium-ion battery according to any of the embodiments of the second aspect of the present application.

[0021] In a fourth aspect, an embodiment of the present application provides a battery pack, including the sodium-ion battery according to any of the embodiments of the second aspect of the present application or the battery module according to any of the embodiments of the third aspect of the present application.

[0022] In a fifth aspect, an embodiment of the present application provides an electrical device, comprising the sodium ion battery described in any embodiment of the second aspect of the present application, the battery module described in any embodiment of the third aspect of the present application, or the battery pack described in any embodiment of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without any creative work.

[0024] FIG1 shows a schematic structural diagram of a vehicle provided by some embodiments of the present application;

[0025] FIG2 shows a schematic structural diagram of a battery pack provided in some embodiments of the present application;

[0026] FIG3 shows a schematic diagram of the exploded structure of the battery pack in FIG2 ;

[0027] FIG4 shows a schematic structural diagram of the battery module in FIG3 ;

[0028] FIG5 shows a schematic structural diagram of a sodium ion battery cell provided by some embodiments of the present application;

[0029] FIG6 shows a schematic diagram of the exploded structure of the sodium ion battery cell in FIG5 .

[0030] In the drawings, the drawings are not drawn to scale.

[0031] Marking Description:

[0032] Vehicles 1000;

[0033] Battery pack 100, controller 200, motor 300;

[0034] A first box 11, a second box 12;

[0035] Battery module 20;

[0036] Sodium ion battery cell 30 , shell 31 , electrode assembly 32 , cover assembly 33 .

[0037] DETAILED DESCRIPTION

[0038] The following embodiments of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0040] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0041] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and A exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0043] It will be apparent to those skilled in the art that various modifications and variations can be made in this application without departing from the scope of protection of this application. Therefore, this application is intended to cover modifications and variations of this application that fall within the scope of the corresponding claims (scopes for which protection is sought) and their equivalents. It should be noted that the embodiments provided in the examples of this application can be combined with each other unless there is any contradiction.

[0044] Before describing the scope of protection provided by the embodiments of the present application, in order to facilitate understanding of the embodiments of the present application, the present application first specifically describes the problems existing in the related art:

[0045] Sodium-ion batteries have become one of the research hotspots in the battery field due to their long cycle life, good safety and low cost. They are also used in consumer electronic devices, transportation, power grid energy storage equipment, engineering machinery and other fields.

[0046] However, in the related art, the solid electrolyte interface (SEI) formed on the electrode surface of the sodium ion battery is prone to rupture under high temperature environment, resulting in poor cycle performance of the sodium ion battery.

[0047] In view of this, the embodiments of the present application provide an electrolyte, a sodium ion battery, a battery module, a battery pack and an electrical device, wherein the electrolyte can improve the cycle performance of the sodium ion battery in a high temperature environment.

[0048] In the present application, electrical devices may include vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools, etc. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0049] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device according to an embodiment of the present application.

[0050] As shown in Figure 1, the vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery pack 100 is provided inside the vehicle 1000. The battery pack 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery pack 100 can be used to power the vehicle 1000. For example, the battery pack 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 can also include a controller 200 and a motor 300. The controller 200 is used to control the battery pack 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0051] In some embodiments of the present application, the battery pack 100 can serve not only as the operating power source of the vehicle 1000, but also as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0052] Figure 2 shows a schematic diagram of the structure of a battery pack provided in some embodiments of the present application. Figure 3 shows a schematic diagram of the exploded structure of the battery pack in Figure 2.

[0053] The battery pack 100 in this application refers to a battery pack including at least one battery module 20 or at least one battery cell 30. As shown in Figures 2 and 3, the battery pack 100 includes a box and a battery module 20, and the battery module 20 is accommodated in the box.

[0054] The battery pack 100 includes a case and a battery module 20, which is housed in the case. The case is used to provide a storage space for the battery module 20, and the case can adopt various structures. In some embodiments, the case can include a first case 11 and a second case 12, which cover each other and together define a storage space for accommodating the battery module 20. The second case 12 can be a hollow structure with one end open, and the first case 11 can be a plate-like structure, with the first case 11 covering the open side of the second case 12, so that the first case 11 and the second case 12 together define a storage space; the first case 11 and the second case 12 can also be hollow structures with one side open, with the open side of the first case 11 covering the open side of the second case 12. Of course, the case formed by the first case 11 and the second case 12 can be of various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0055] In the battery pack 100, there may be multiple battery modules 20. The multiple battery modules 20 may be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a configuration in which the multiple battery modules 20 are connected in both series and parallel. The multiple battery modules 20 may be directly connected in series, in parallel, or in a hybrid configuration, and then the entire battery module 20 may be housed in a housing.

[0056] FIG4 shows a schematic structural diagram of the battery module in FIG3 .

[0057] The battery module 20 includes one or more sodium-ion battery cells 30. For example, as shown in FIG4 , the battery module 20 includes multiple sodium-ion battery cells 30. The multiple sodium-ion battery cells 30 can be connected in series, in parallel, or in a hybrid connection. A hybrid connection means that the multiple sodium-ion battery cells 30 are connected both in series and in parallel. The multiple sodium-ion battery cells 30 can be directly connected in series, in parallel, or in a hybrid connection.

[0058] Each sodium ion battery cell 30 may be a secondary battery cell or a primary battery. In addition, the sodium ion battery cell 30 may be cylindrical, flat, rectangular, or in other shapes.

[0059] Figure 5 shows a schematic diagram of the structure of a sodium ion battery cell provided in some embodiments of the present application. Figure 6 shows a schematic diagram of the exploded structure of the sodium ion battery cell in Figure 5.

[0060] As shown in Figure 5, a sodium-ion battery cell 30 is the smallest unit that makes up a battery. As shown in Figure 6, a sodium-ion battery cell 30 includes a housing 31, an electrode assembly 32, and a cover assembly 33. The housing 31 has a chamber that accommodates the electrode assembly 32, and the cover assembly 33 is used to seal the opening of the housing 31. The cover assembly 33 includes an end cap that connects to the housing 31 to form the outer shell of the sodium-ion battery cell 30. The electrode assembly 32 is disposed within the housing 31, and the housing 31 is filled with electrolyte.

[0061] The end cap is a component that fits over the opening of the housing 31 to isolate the internal environment of the sodium-ion battery cell 30 from the external environment. The shape of the end cap can be adapted to the shape of the housing 31 to fit the housing 31. Optionally, the end cap can be made of a material with a certain degree of hardness and strength (such as an aluminum alloy). This prevents deformation during compression and collision, giving the sodium-ion battery cell 30 greater structural strength and improved safety. The end cap can be provided with functional components such as electrode terminals. The electrode terminals can be used to electrically connect to the electrode assembly 32 for inputting or outputting electrical energy from the sodium-ion battery cell 30. In some embodiments, the end cap can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the sodium-ion battery cell 30 reaches a threshold. The end cap can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, and plastic, and this is not specifically limited in the present embodiments. In some embodiments, an insulating member may be provided inside the end cap to isolate the electrical connection components in the housing 31 from the end cap to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0062] The housing 31 is a component used to cooperate with the end cap to form the internal environment of the sodium-ion battery cell 30, wherein the formed internal environment can be used to accommodate the electrode assembly 32, electrolyte, and other components. The housing 31 and the end cap can be independent components. An opening can be provided on the housing 31, and the internal environment of the sodium-ion battery cell 30 is formed by closing the end cap at the opening. Without limitation, the end cap and the housing 31 can also be integrated. Specifically, the end cap and the housing 31 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 31 needs to be encapsulated, the end cap is closed to the housing 31. The housing 31 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc.

[0063] The electrode assembly 32 is a component in the sodium-ion battery cell 30 where electrochemical reactions occur. One or more electrode assemblies 32 may be contained in the housing 31. The electrode assembly 32 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly 32, and the parts of the positive and negative electrode sheets without active materials each constitute a tab. The positive and negative electrode tabs may be located together at one end of the main body or at both ends of the main body respectively. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs connect the electrode terminals to form a current loop.

[0064] electrolyte

[0065] An embodiment of the present application provides an electrolyte, which includes a sodium salt and an organic solvent. The organic solvent includes a fluorinated organic compound, an ether organic compound, and a coordinated organic compound, wherein the coordinated organic compound contains multiple functional groups that can coordinate with a transition metal.

[0066] In the electrolyte provided in the embodiment of the present application, under high temperature environmental conditions, the fluorinated organic compound and the coordinated organic compound can be co-dissolved in the ether organic compound and act synergistically to form a stable solid electrolyte interface film on the electrode surface. On the one hand, the fluorinated organic compound can help form a stable solid electrolyte interface film on the surface of the electrode pole piece to reduce the formation of sodium dendrites, thereby improving the cycle performance of the sodium ion battery. On the other hand, the transition metal dissolved from the electrode pole piece under high temperature environment can coordinate with the functional groups in the coordinated organic compound, reducing the damage of the transition metal to the solid electrolyte interface film, thereby improving the stability of the solid electrolyte interface film, and further improving the cycle performance of the sodium ion battery. Therefore, the electrolyte provided in the embodiment of the present application can improve the cycle performance of the sodium ion battery under high temperature environment.

[0067] In some embodiments of the present application, the fluorinated organic compound includes fluorinated carbonate and / or fluorinated ether.

[0068] Fluorinated carbonate refers to a compound in which a part or all of the hydrogen atoms in carbonate are substituted with fluorine atoms, and fluorinated ether refers to a compound in which a part or all of the hydrogen atoms in ether are substituted with fluorine atoms.

[0069] In the above embodiments, fluorocarbonates and fluoroethers can help form a sodium fluoride (NaF)-rich SEI film. The NaF-rich SEIM not only has higher mechanical strength to adapt to large volume changes, but also promotes the uniform deposition of Na, thereby further improving the stability of the solid electrolyte interface film, effectively reducing the formation of sodium dendrites, and greatly improving the cycle performance of the sodium ion battery.

[0070] In some embodiments of the present application, the fluorinated carbonate includes a fluorinated chain carbonate and / or a fluorinated cyclic carbonate.

[0071] The fluorinated chain carbonate refers to a compound in which one or more hydrogen atoms in the chain carbonate are replaced by fluorine atoms, and the fluorinated cyclic carbonate refers to a compound in which one or more hydrogen atoms in the cyclic carbonate are replaced by fluorine atoms.

[0072] In some specific embodiments of the present application, the fluorinated chain carbonate includes at least one of trifluoromethyl ethyl carbonate (FEMC), trifluoromethyl propyl carbonate, bis(trifluoromethyl) carbonate and bis(2,2,2-trifluoroethyl) carbonate.

[0073] In some other specific embodiments of the present application, the fluorinated cyclic carbonate includes at least one of fluorinated ethylene carbonate (FEC), fluorinated propylene carbonate, and fluorinated butylene carbonate.

[0074] In some specific embodiments of the present application, the fluoroether includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE-347), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether.

[0075] In the embodiments of the present application, the ether organic compound can help the fluorinated organic compound and the coordinated organic compound to co-dissolve and act synergistically to form a stable SEI film.

[0076] In some embodiments of the present application, the ether organic compound includes at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol methylene ether, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0077] In the two aforementioned embodiments, the ether organic matter can help form a stable solid electrolyte interface film and reduce electrochemical polarization.

[0078] In some embodiments of the present application, the functional group of the coordinating organic compound is selected from cyano.

[0079] In the above embodiments, the cyano group (-CN) can make the coordinated organic matter have better stability and stronger coordination ability, which can help form a stable solid electrolyte interface film on the surface of the electrode plate, thereby further improving the cycle performance of the sodium ion battery.

[0080] In some embodiments of the present application, the coordination organic compound includes a nitrile solvent containing 2 to 4 cyano groups.

[0081] In the above embodiments, the nitrile solvent contains 2-4 cyano groups, which can enhance its coordination ability, so that the nitrile solvent and the transition metal can be better combined, thereby helping to enhance the electrolyte's resistance to electrode oxidation, thereby reducing the decomposition of the electrolyte.

[0082] In some specific embodiments of the present application, the coordinating organic compound includes at least one of 1,3,6-hexanetrinitrile (HTCN), 1,3,5-pentanetrinitrile, succinonitrile, glutaronitrile, adiponitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, tricyanobenzene, and 1,2-bis(cyanoethoxy)ethane.

[0083] In the embodiments of the present application, the fluorinated organic matter, ether organic matter and coordination organic matter in the electrolyte are within a suitable volume percentage range, which can contribute to a synergistic effect and improve the cycle performance of the sodium ion battery in a high temperature environment.

[0084] In some embodiments of the present application, the volume percentage of the fluorinated organic compound in the organic solvent is 5%-30% based on the total volume of the organic solvent. The fluorinated organic compound within the above suitable range can help improve the cycle performance of the sodium ion battery in a high temperature environment.

[0085] Exemplarily, the volume percentage of the fluorinated organic compound in the organic solvent can be, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%.

[0086] Based on the above embodiments, the volume percentage of the ether organic compound in the organic solvent is 55%-93%. When the ether organic compound is within the above suitable range, it can help form a stable SEI film and further reduce electrochemical polarization.

[0087] Illustratively, the volume percentage of the ether organic matter in the organic solvent can be, but is not limited to, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, or 93%.

[0088] Based on the above embodiments, the volume percentage of the coordinated organic compound in the organic solvent is 2%-15%. When the coordinated organic compound is within the above suitable range, the electrolyte can have a suitable viscosity, thereby making the sodium ion battery have a lower internal resistance.

[0089] Illustratively, the volume percentage of the coordinating organic compound in the organic solvent can be, but is not limited to, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0090] In the embodiments of the present application, the sodium salt may be any well-known electrolyte sodium salt in sodium ion batteries.

[0091] In some embodiments of the present application, the sodium salt includes at least one of sodium hexafluorophosphate (NaPF6), sodium difluorooxalatoborate (NaDFOB), sodium tetrafluoroborate (NaBF4), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium bis(oxalatoborate) (NaBOB), sodium perchlorate, sodium hexafluoroarsenate, and sodium trifluoromethylsulfonate.

[0092] When sodium-ion batteries are exposed to high temperatures (>30°C), the anions in the electrolyte decompose to form decomposition products. These decomposition products damage the SEI membrane, resulting in a decrease in the cycling stability of the sodium-ion battery. However, controlling the sodium salt content within a reasonable range can help improve the cycling performance of sodium-ion batteries.

[0093] In some embodiments of the present application, the concentration of the sodium salt can be set at 0.5 mol / L-8 mol / L.

[0094] Illustratively, the concentration of sodium salt can be, but is not limited to, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L, 6.5 mol / L, 7.0 mol / L, 7.5 mol / L, or 8.0 mol / L.

[0095] Sodium-ion batteries

[0096] An embodiment of the present application provides a sodium ion battery, comprising the electrolyte of any one of the above embodiments.

[0097] In addition, the sodium-ion battery in the embodiments of the present application further includes an electrode assembly, which generally includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. Among them, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and containing a positive electrode active material.

[0098] In some embodiments of the present application, the positive electrode active material includes at least one of sodium transition metal oxides, polyanion-type compounds, and Prussian blue compounds.

[0099] Exemplarily, the sodium transition metal oxide has the general formula Na x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1; the polyanion-type compounds include one or more of vanadium trifluorophosphate, sodium fluorophosphate vanadate, sodium vanadium phosphate, sodium iron phosphate, and Na4Fe3(PO4)2P2O7; the Prussian blue compounds have the general formula Na y M 1 M 2 (CN)6, where M 1 and M 2 are each independently one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0 < y ≤ 2.

[0100] In addition, in some embodiments of the present application, the positive electrode active material layer may further include a conductive agent and a binder. The conductive agent is used to improve the conductivity of the positive electrode active material layer, and the binder is used to firmly bond the positive electrode active material and the binder to the positive electrode current collector. The types of the conductive agent and the binder are not specifically limited in the embodiments of the present application and can be selected according to actual needs.

[0101] Exemplarily, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may include at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA).

[0102] In the embodiments of the present application, the positive electrode current collector may be made of a metal foil, a carbon-coated metal foil, or a porous metal plate. In some specific embodiments of the present application, the positive electrode current collector is made of an aluminum foil.

[0103] In some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material, wherein the negative electrode active material includes at least one of a carbon material, metallic sodium, a sodium alloy, and a sodium metal oxide.

[0104] In addition, in some embodiments of the present application, the negative electrode active material layer may further include a conductive agent and a binder. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. The embodiments of the present application do not specifically limit the types of the conductive agent and the binder, and they can be selected according to actual needs.

[0105] Exemplarily, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers; the binder may include at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin and carboxymethyl cellulose (CMC).

[0106] In some embodiments of the present application, the negative electrode active material layer may further include a thickener, such as carboxymethyl cellulose (CMC). However, the present application is not limited thereto, and other materials that can be used as thickeners for sodium ion battery negative electrode sheets may also be used in the present application.

[0107] In the embodiments of the present application, the negative electrode current collector may be made of metal foil, carbon-coated metal foil, porous metal plate, etc. In some specific embodiments of the present application, the negative electrode current collector is made of copper foil.

[0108] The embodiments of the present application do not have any special restrictions on the isolation membrane. Any porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can be a single-layer or multi-layer film containing one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0109] In addition, the sodium-ion battery also includes a shell and an end cap assembly. The shell is a component used to cooperate with the end cap assembly to form an internal environment of the sodium-ion battery cell, wherein the formed internal environment can be used to accommodate the electrode assembly, electrolyte and other components.

[0110]

[0111] The sodium ion battery provided in the embodiments of the present application can be prepared by conventional methods. For example, the following preparation method can be used: the positive electrode active material, the conductive agent and the binder are dispersed in a solvent (such as N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, the positive electrode slurry is coated on the two opposite surfaces of the positive electrode current collector, and the positive electrode sheet is obtained after drying, cold pressing and punching; the negative electrode active material, the conductive agent, the binder and the thickener are dispersed in a solvent (such as deionized water) to form a uniform negative electrode slurry, the negative electrode slurry is coated on the two opposite surfaces of the negative electrode current collector, and the negative electrode sheet is obtained after drying, cold pressing and punching; the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence to obtain an electrode assembly, or they are stacked in sequence and wound to obtain an electrode assembly; the electrode assembly is placed in a shell, the electrolyte is injected and the shell is encapsulated to obtain a sodium ion battery.

[0112] battery module

[0113] The present application provides a battery module including the sodium-ion battery of any of the above embodiments. Since the battery module includes the sodium-ion battery of the above embodiments, the battery module also has the technical effects of the above sodium-ion battery, which will not be described in detail here.

[0114] battery pack

[0115] The present application provides a battery pack including the sodium-ion battery or battery module described in the above embodiments. Because the battery pack includes the sodium-ion battery or battery module described in the above embodiments, the battery pack also has the technical effects of the sodium-ion battery or battery module described above, and further description thereof is omitted here.

[0116] Electrical devices

[0117] The present application provides an electrical device comprising the sodium-ion battery, battery module, or battery pack described in the above embodiments. Due to the inclusion of the sodium-ion battery, battery module, or battery pack described in the above embodiments, the electrical device has a long service life and range.

[0118] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0119] Example 1

[0120] Preparation of positive electrode

[0121] 10wt% polyvinylidene fluoride (PVDF) binder is fully dissolved in NMP, and 10wt% carbon black conductive agent and 80wt% positive electrode active material Na4Fe3(PO4)2P2O7 are added to make a uniformly dispersed positive electrode slurry; the positive electrode slurry is coated on two opposite surfaces of aluminum foil, and after drying, cold pressing and punching, the positive electrode sheet is obtained.

[0122] Preparation of negative electrode sheet

[0123] 4 wt% carbon nanotube material and 1.6 wt% polymer binder sodium carboxymethyl cellulose were added to water and stirred to form a uniform negative electrode slurry. The negative electrode slurry was coated on two opposite surfaces of the copper foil, and the negative electrode sheet was obtained after drying, cold pressing and punching.

[0124] Preparation of electrolyte

[0125] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), sodium salt sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), fluoroethylene carbonate (FEC), and 1,3,6-hexanetrinitrile (HTCN) were dissolved in ether organic matter ethylene glycol dimethyl ether (DME) according to the proportions in Table 1 and stirred uniformly to obtain an electrolyte with a sodium salt concentration of 1 mol / L.

[0126] Isolation film

[0127] Polypropylene film is used as the isolation film.

[0128] Preparation of sodium ion batteries

[0129] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator located between the positive and negative electrode sheets, to obtain an electrode assembly. The electrode assembly is placed in a shell, and an electrolyte is injected and packaged to obtain a sodium ion battery.

[0130] Examples 2-14 and Comparative Examples 1-6

[0131] The preparation method is similar to that of Example 1, except that the composition and content of the organic solvent are shown in Table 1.

[0132] Test section

[0133] (1) Coulomb efficiency test

[0134] At 25°C, the battery was charged to 4.15V at a constant current of 1 / 3C, and then charged at a constant voltage of 4.15V until the current dropped to 0.05C. The initial charge capacity (C c1 ); then discharge to 2.5V at a constant current of 1 / 3C to obtain the first discharge capacity (Cd1 ). Coulombic efficiency can be calculated according to the following formula:

[0135] Coulombic efficiency = C d1 / C c1 ×100%.

[0136] (2) Capacity retention test

[0137] At 45°C, the battery was charged to 4.15V at a constant current of 1C, then charged at a constant voltage of 4.15V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 1C. The first cycle discharge capacity (C d1 ); Repeat the charge and discharge until the 200th cycle, and record the discharge capacity as C d200 The capacity retention rate is calculated according to the following formula:

[0138] Capacity retention rate = C d200 / C d1 ×100%.

[0139] (3) Testing of transition metal cyanides

[0140] The transition metal cyanide is tested using the ion chromatography UV test method, which is as follows:

[0141] Samples were taken from each embodiment and comparative example, i.e., the samples were electrolytes after the battery cycled 200 times;

[0142] Separate the electrolyte using a chromatographic column to obtain a solution to be tested;

[0143] The test solution was quantitatively detected by ion chromatography.

[0144] Through the above quantitative test, it can be seen that in each example, the tested solution has a characteristic peak at a wavelength of about 215 nm. Therefore, this test can show that the cyano group can coordinate with the transition metal to form a complex.

[0145] Table 1

[0146] No. Components and Volume Percentage of Organic Solvents (%) Coulombic Efficiency (%) Capacity Retention Rate (%) Example 1 DME:FEC:HTCN (70:20:10) 97.590.2 Example 2 DME:FEC:HTCN (93:5:2) 94.686.1 Example 3 DME:FEC:HTCN (55:30:15) 96.888.4 Example 4 DME:FEC:HTCN (70:20:10) 96.988.8 Example 5 DME:FEC:HTCN (70:20:10) 95.287.6 Example 6 DME:FEC:HTCN (70:20:10) 94.586.1 Example 7 DME:FEC:HTCN (70:20:10) 92.384.9 Example 8 DEE:FEC:HTCN (70:20:10) 97.089.4 Example 9 DME:FEMC:HTCN (70:20:10) 97.189.8 Example 1 0DME:HFE-347:HTCN (70:20:10) 96.788.2 Example 11DME:FEC:1,3,5-pentanetrinitrile (70:20:10) 96.487.9 Example 12DME:FEC:succinonitrile (70:20:10) 95.788.1 Example 13DME:FEC:2,2-difluorosuccinonitrile (70:20:10) 96.188.6 Example 14DME:FEC:tricyanobenzene (70: Comparative Example 1 DME 82.6 71.8 Comparative Example 2 DME:FEC (80:20) 84.9 74.1 Comparative Example 3 DME:HTCN (90:10) 85.4 76.5 Comparative Example 4 DME:FEC:acetonitrile (70:20:10) 87.7 78.2 Comparative Example 5 FEC:acetonitrile (67:33) 78.5 66.2 Comparative Example 6 DMC:FEC:acetonitrile (70:20:10) 81.6 68.9

[0147] According to Table 1, by comparing the test results of Examples 1-14 and Comparative Examples 1-6, it can be seen that the electrolyte provided in the embodiments of the present application can enable the sodium ion battery to have good cycle performance at high temperatures.

[0148] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and equivalent components may be substituted without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all embodiments falling within the scope of the claims.

Claims

1. An electrolyte comprising: sodium salt; The organic solvent includes a fluorinated organic compound, an ether organic compound and a coordinated organic compound, wherein the coordinated organic compound contains a plurality of functional groups capable of coordinating with a transition metal.

2. The electrolyte according to claim 1, wherein The fluorinated organic compound includes fluorinated carbonate and / or fluorinated ether.

3. The electrolyte according to claim 2, wherein The fluorinated carbonate comprises a fluorinated chain; Optionally, the fluorinated chain carbonate includes at least one of trifluoromethyl ethyl carbonate, trifluoromethyl propyl carbonate, bis(trifluoromethyl) carbonate and bis(2,2,2-trifluoroethyl) carbonate. Optionally, the fluorinated cyclic carbonate includes at least one of fluorinated ethylene carbonate, fluorinated propylene carbonate and fluorinated butylene carbonate.

4. The electrolyte according to claim 2 or 3, wherein The fluoroether includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether.

5. The electrolyte according to any one of claims 1 to 4, wherein The ether organic matter includes at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol methylene ether, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

6. The electrolyte according to any one of claims 1 to 5, wherein The functional group is selected from cyano groups.

7. The electrolyte according to any one of claims 1 to 6, wherein The coordination organic compound includes at least one of 1,3,6-hexanetrinitrile, 1,3,5-pentanetrinitrile, succinonitrile, glutaronitrile, adiponitrile, 2-fluoroadiponitrile, 2,2-difluorosuccinonitrile, tricyanobenzene, and 1,2-bis(cyanoethoxy)ethane.

8. The electrolyte according to any one of claims 1 to 7, wherein Based on the total volume of the organic solvent, the volume percentage of the fluorinated organic compound in the organic solvent is 5%-30%; The volume percentage of the ether organic matter in the organic solvent is 55%-93%; The volume percentage of the coordinated organic matter in the organic solvent is 2%-15%.

9. The electrolyte according to any one of claims 1 to 8, wherein The sodium salt includes at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

10. A sodium ion battery comprising the electrolyte according to any one of claims 1 to 9.

11. The sodium ion battery according to claim 10, wherein: It also includes a positive electrode plate, which includes a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector and containing a positive electrode active material, wherein the positive electrode active material includes at least one of a transition metal oxide, a polyanionic compound and a Prussian blue compound.

12. The sodium ion battery according to claim 11, wherein The sodium transition metal oxide has the general formula Na x MO2, M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1; The polyanionic compound includes one or more of vanadium trifluorophosphate, sodium vanadium trifluorophosphate, sodium vanadium phosphate, sodium iron phosphate and Na4Fe3(PO4)2P2O7; The Prussian blue compound has the general formula Na y M 1 M 2 (CN)6,M 1 、M 2 Each independently represents one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0<y≤2.

13. The sodium ion battery according to any one of claims 10 to 12, wherein: It also includes a negative electrode plate, which includes a negative electrode collector and a negative electrode active material layer arranged on at least one surface of the negative electrode collector and containing a negative electrode active material, wherein the negative electrode active material includes at least one of a carbon material, metallic sodium, a sodium alloy and a sodium metal oxide.

14. A battery module comprising the sodium ion battery according to any one of claims 10 to 13.

15. A battery pack comprising the sodium ion battery according to any one of claims 10 to 13 or the battery module according to claim 14.

16. An electrical device comprising the sodium ion battery according to any one of claims 10 to 13, the battery module according to claim 14, or the battery pack according to claim 15.

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