Electrolyte, secondary battery and electric device

Abstract

The invention discloses an electrolyte, a secondary battery and an electric device. The electrolyte comprises a cyclic ether additive as shown in a formula I; wherein n is a positive integer of 1-20, and R1, R2 and R3 independently comprise any one of hydrogen, fluorine, nitryl and alkyl with the carbon atom number of 1-6. The electrolyte is improved, so that the cycle performance and the rate capability of the secondary battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to an electrolyte, a secondary battery, and an electrical device. Background Technology

[0002] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as in military equipment and aerospace and other fields.

[0003] Improving the cycle performance and rate performance of rechargeable batteries has always been an industry goal. As a crucial component of batteries, the composition of the electrolyte affects battery performance. However, side reactions at the anode and cathode interfaces of the electrolyte can lead to poor overall cell performance. Summary of the Invention

[0004] This application addresses the aforementioned issues and aims to provide an electrolyte, a secondary battery, and an electrical device. The goal is to improve the cycle performance and rate performance of the secondary battery through improvements to the electrolyte.

[0005] To achieve the above objectives, this application provides an electrolyte, a secondary battery, and an electrical device.

[0006] In a first aspect, this application provides an electrolyte comprising cyclic ether additives as shown in Formula I;

[0007]

[0008] Where n is a positive integer from 1 to 20, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, or alkyl groups having 1 to 6 carbon atoms.

[0009] Adding cyclic ether additives to the electrolyte, which contain at least three carbon-oxygen bonds, allows them to strongly coordinate with sodium ions, participating in the formation of the negative electrode SEI (Solid Electrolyte Interphase) film. This results in a denser, more uniform, and stable SEI film, suppressing side reactions in the electrolyte and negative electrode. Furthermore, the strong coordination between the cyclic ether additives and sodium ions reduces the sodium ion concentration on the negative electrode surface, preventing the formation of large crystal nuclei and effectively inhibiting sodium dendrite growth. This, in turn, improves the battery's cycle performance and rate performance.

[0010] In any embodiment, n is a positive integer from 1 to 5, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, and alkyl groups having 1 to 4 carbon atoms.

[0011] When R1, R2, and R3 have branched structures, they can increase the steric hindrance after the cyclic ether additives and sodium ions are combined through coordination, which is more conducive to reducing the sodium ion concentration on the negative electrode surface to prevent the formation of large crystal nuclei and effectively inhibit the growth of sodium dendrites.

[0012] In any embodiment, the cyclic ether additive includes at least one of the compounds shown in Formula I-1 to Formula I-22:

[0013]

[0014] When cyclic ether additives include at least one compound shown in Formulas I-1 to I-22, they can undergo strong coordination with sodium ions, participating in the formation of the negative electrode SEI film, making the SEI film more dense, uniform, and stable, and suppressing side reactions in the electrolyte and negative electrode; they can also reduce the sodium ion concentration on the negative electrode surface to prevent the formation of large crystal nuclei, effectively inhibiting the growth of sodium dendrites. This, in turn, improves the battery's cycle performance and rate performance.

[0015] In any embodiment, the mass percentage of cyclic ether additives in the electrolyte is 0.1%-10%. Within this suitable range, the mass percentage of cyclic ether additives is beneficial for improving the stability and density of the SEI film, suppressing side reactions in the electrolyte and negative electrode, effectively inhibiting the growth of sodium dendrites, and improving the cycle performance and rate performance of the battery.

[0016] In any embodiment, the cyclic ether additives account for 1% to 10% of the electrolyte by mass. Within this suitable range, the cyclic ether additives can better participate in the formation of the negative electrode SEI film, making the SEI film denser, more uniform, and more stable, suppressing side reactions in the electrolyte and negative electrode, and also more effectively suppressing the growth of sodium dendrites, thereby contributing to higher cycle performance and rate performance of the battery.

[0017] In any embodiment, the electrolyte further includes borate ester additives as shown in Formula II.

[0018]

[0019] L1, L2, and L3 each independently include any one of alkyl groups, substituted or unsubstituted phenyl groups having 1 to 4 carbon atoms.

[0020] Adding borate esters to the electrolyte can effectively remove water and alkaline impurities from the positive electrode surface, participate in the formation of the positive electrode CEI (Cathode electrolyte interphase) film, make the CEI film more dense, uniform and stable, suppress side reactions of the electrolyte and positive electrode, and thus further improve the cycle performance and rate performance of the battery.

[0021] In any embodiment, the borate ester additive includes at least one selected from trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and triphenyl borate. This effectively removes water from the electrolyte and alkaline impurities from the positive electrode surface, improves the stability and density of the CEI film, suppresses side reactions in the electrolyte and positive electrode, and thus further improves the battery's cycle performance and rate performance.

[0022] In any embodiment, the borate ester additives account for 0.1%-10% of the electrolyte by mass. Within this suitable range, the mass percentage of borate ester additives is beneficial for improving the stability and density of the CEI film, suppressing side reactions in the electrolyte and the negative electrode, and also for removing water from the electrolyte and alkaline impurities on the positive electrode surface, thereby further improving the cycle performance and rate performance of the battery.

[0023] In any embodiment, the borate ester additives account for 1%-10% of the mass of the electrolyte. Within this suitable range, the borate ester additives can better participate in the formation of the positive electrode CEI film, making the CEI film denser, more uniform, and more stable, suppressing side reactions in the electrolyte and the positive electrode, and also facilitating the removal of water from the electrolyte and alkaline impurities on the positive electrode surface, thereby contributing to higher cycle performance and rate performance of the battery.

[0024] In any embodiment, the electrolyte further includes a solvent, which includes at least one selected from diethyl ether, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, and methyltetrahydrofuran. This promotes the dissolution of electrolyte salts, facilitates ion transport, and gives the electrolyte good ionic conductivity.

[0025] In any embodiment, the electrolyte further includes a sodium salt, including at least one of sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, sodium difluorooxalate borate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0026] In any embodiment, the concentration of the sodium salt in the electrolyte is 0.1-3 mol / L. A sodium salt concentration within this suitable range in the electrolyte is beneficial for the transport of sodium ions.

[0027] Secondly, this application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte according to the first aspect of this application.

[0028] Thirdly, this application provides an electrical device, including the secondary battery of the second aspect of this application. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0030] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0031] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0032] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0033] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0034] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrolyte, secondary battery, and power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0038] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0042] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0043] During the charging and discharging process of sodium batteries, the electrolyte is prone to instability in the solid electrolyte interface (SEI) film formed at the negative electrode, which will continuously consume electrolyte components and electrode materials, resulting in a decrease in the cycle performance and rate performance of the battery.

[0044] In view of the above problems, in a first aspect, this application provides an electrolyte comprising cyclic ether additives as shown in Formula I;

[0045]

[0046] Where n is a positive integer from 1 to 20, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, or alkyl groups having 1 to 6 carbon atoms.

[0047] In this document, "alkyl group with 1-6 carbon atoms" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, without any unsaturation, having 1 to 6 carbon atoms, and attached to the rest of the molecule by a single bond. Suitable examples include, but are not limited to: methyl (-CH3), ethyl (-CH2CH3), 1-propyl (-CH2CH2CH3), 2-propyl (-CH(CH3)2), 1-butyl (-CH2CH2CH2CH3), 1-pentyl (-CH2CH2CH2CH2CH3), and 1-hexyl (-CH2CH2CH2CH2CH2CH3).

[0048] In this article, "nitro" refers to the group remaining after removing one hydroxyl group from a nitric acid molecule, with the chemical formula -NO2.

[0049] n can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

[0050] Adding cyclic ether additives to the electrolyte, which contain at least three carbon-oxygen bonds, allows them to strongly coordinate with sodium ions, participating in the formation of the negative electrode SEI (Solid Electrolyte Interphase) film. This results in a denser, more uniform, and stable SEI film, suppressing side reactions in the electrolyte and negative electrode. Furthermore, the strong coordination between the cyclic ether additives and sodium ions reduces the sodium ion concentration on the negative electrode surface, preventing the formation of large crystal nuclei and effectively inhibiting sodium dendrite growth. This, in turn, improves the battery's cycle performance and rate performance.

[0051] In some embodiments, n is a positive integer from 1 to 5, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, and alkyl groups having 1 to 4 carbon atoms.

[0052] Similarly, in this article, "alkyl group with 1-4 carbon atoms" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, without any unsaturation, having 1 to 4 carbon atoms, and attached to the rest of the molecule by a single bond. Suitable examples include, but are not limited to: methyl (-CH3), ethyl (-CH2CH3), 1-propyl (-CH2CH2CH3), 2-propyl (-CH(CH3)2), and 1-butyl (-CH2CH2CH2CH3).

[0053] n can be 1, 2, 3, 4, or 5.

[0054] When R1, R2, and R3 have branched structures, they can increase the steric hindrance after the cyclic ether additives and sodium ions are combined through coordination, which is more conducive to reducing the sodium ion concentration on the negative electrode surface to prevent the formation of large crystal nuclei and effectively inhibit the growth of sodium dendrites.

[0055] In some embodiments, the cyclic ether additives include at least one of the compounds shown in Formula I-1 to Formula I-22:

[0056]

[0057] When cyclic ether additives include at least one compound shown in Formulas I-1 to I-22, they contain at least three carbon-oxygen bonds, which can strongly coordinate with sodium ions and participate in the formation of the negative electrode SEI film, making the SEI film more dense, uniform, and stable, and suppressing side reactions in the electrolyte and negative electrode. They can also reduce the sodium ion concentration on the negative electrode surface to prevent the formation of large crystal nuclei and effectively suppress the growth of sodium dendrites. This, in turn, improves the battery's cycle performance and rate performance.

[0058] It should be noted that in the embodiments of this application, only one carbon atom is connected between the two oxygen atoms of the cyclic ether additive. Compared with the case where more carbon atoms are connected between the two oxygen atoms, only one carbon atom is connected between the two oxygen atoms, which can form a stronger coordination with sodium ions, which is beneficial to reduce the sodium ion concentration on the negative electrode surface and effectively inhibit the growth of sodium dendrites.

[0059] In some embodiments, the cyclic ether additives constitute 0.1%-10% of the electrolyte by mass. Within this suitable range, the mass percentage of cyclic ether additives is beneficial for improving the stability and density of the SEI film, suppressing side reactions in the electrolyte and negative electrode, effectively inhibiting the growth of sodium dendrites, and improving the cycle performance and rate performance of the battery. The mass percentage of cyclic ether additives in the electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, 3.8%, 4%, 4.2%, 4%. 4%, 4.5%, 4.8%, 5%, 5.2%, 5.4%, 5.5%, 5.8%, 6%, 6.2%, 6.4%, 6.5%, 6.8%, 7%, 7.2%, 7.4%, 7.5%, 7.8%, 8%, 8.2%, 8.4%, 8.5%, 8.8%, 9%, 9.2%, 9.4%, 9.5%, 9.8%, 10%, or any value between these values.

[0060] In some embodiments, the cyclic ether additives constitute 1% to 10% of the electrolyte by mass. Within this suitable range, the cyclic ether additives can better participate in the formation of the negative electrode SEI film, making the SEI film denser, more uniform, and more stable, suppressing side reactions in the electrolyte and negative electrode, and also more effectively suppressing the growth of sodium dendrites, thereby contributing to higher cycle performance and rate performance of the battery.

[0061] In some embodiments, the electrolyte further includes borate ester additives as shown in Formula II.

[0062]

[0063] L1, L2, and L3 each independently include any one of alkyl groups, substituted or unsubstituted phenyl groups having 1 to 4 carbon atoms.

[0064] Here, "alkyl group with 1-4 carbon atoms" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, without any unsaturation, having 1 to 4 carbon atoms, and attached to the rest of the molecule by a single bond. Suitable examples include, but are not limited to: methyl (-CH3), ethyl (-CH2CH3), 1-propyl (-CH2CH2CH3), 2-propyl (-CH(CH3)2), and 1-butyl (-CH2CH2CH2CH3).

[0065] In this article, "substituted" means that at least one hydrogen atom of the compound or chemical part is replaced by a substituent in another chemical part, wherein the substituents may be independently selected from: hydroxyl, mercapto, amino, cyano, nitro, aldehyde, halogen atom, alkenyl, alkynyl, aryl, heteroaryl, C1-6 alkyl, C1-6 alkoxy.

[0066] Adding borate esters to the electrolyte can effectively remove water and alkaline impurities from the positive electrode surface, participate in the formation of the positive electrode CEI (Cathode electrolyte interphase) film, make the CEI film more dense, uniform and stable, suppress side reactions of the electrolyte and positive electrode, and thus further improve the cycle performance and rate performance of the battery.

[0067] In some embodiments, the borate ester additives include at least one of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and triphenyl borate. This effectively removes water from the electrolyte and alkaline impurities from the positive electrode surface, improves the stability and density of the CEI film, suppresses side reactions in the electrolyte and positive electrode, and thus further improves the battery's cycle performance and rate performance.

[0068] In some embodiments, the borate ester additives constitute 0.1%-10% of the electrolyte by mass. Within this suitable range, the mass percentage of borate ester additives is beneficial for improving the stability and density of the CEI film, suppressing side reactions in the electrolyte and negative electrode, and also for removing water from the electrolyte and alkaline impurities from the positive electrode surface, further improving the battery's cycle performance and rate performance. The mass percentage of borate ester additives in the electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, 3.8%, 4%, 4.2%, 4%. 4%, 4.5%, 4.8%, 5%, 5.2%, 5.4%, 5.5%, 5.8%, 6%, 6.2%, 6.4%, 6.5%, 6.8%, 7%, 7.2%, 7.4%, 7.5%, 7.8%, 8%, 8.2%, 8.4%, 8.5%, 8.8%, 9%, 9.2%, 9.4%, 9.5%, 9.8%, 10%, or any value between these values.

[0069] In some embodiments, the borate ester additives constitute 1%-10% of the electrolyte by mass. Within this suitable range, the borate ester additives can better participate in the formation of the positive electrode CEI film, making the CEI film denser, more uniform, and more stable, suppressing side reactions in the electrolyte and the positive electrode, and also facilitating the removal of water from the electrolyte and alkaline impurities on the positive electrode surface, thereby contributing to higher cycle performance and rate performance of the battery.

[0070] In some embodiments, the electrolyte further includes a solvent, which includes at least one selected from diethyl ether, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, and methyltetrahydrofuran. This promotes the dissolution of electrolyte salts, facilitates ion transport, and gives the electrolyte good ionic conductivity.

[0071] In some embodiments, the electrolyte further includes a sodium salt, including at least one of sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, sodium difluorooxalate borate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0072] In some embodiments, the concentration of sodium salt in the electrolyte is 0.1-3 mol / L. Here, when the electrolyte includes solvents and additives, "concentration of sodium salt in the electrolyte" refers to the concentration of sodium salt in the solvent and additives. A sodium salt concentration within this suitable range is beneficial for the transport of sodium ions in the electrolyte. The concentration of sodium salt in the electrolyte can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L, 3 mol / L, or any value between these values.

[0073] Secondly, this application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte according to the first aspect of this application.

[0074] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0075] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0076] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0077] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0078] In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material may further include positive electrode active materials known in the art for use in sodium-ion batteries. For example, the positive electrode active material is selected from one or more of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0079] In layered transition metal oxides, the transition metal can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, Na is a layered transition metal oxide. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0080] Polyanionic compounds can be those containing sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0081] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0082] Polyanionic compounds can also be sodium ion-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0083] In some embodiments, the polyanionic compound is, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' being one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0084] In some embodiments, the Prussian blue analogue may be a compound containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue analogues include, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0085] In some embodiments, the specific positive electrode active material is, for example, NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3O2, Na4Fe3(PO4)2P2O7, NaFePO4, Na3V2(PO4)3, NaMnFe(CN)6, but there are no particular restrictions, so conventional positive electrode active materials used in sodium-ion batteries can be selected.

[0086] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0087] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0089] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0090] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0091] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and sodium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0093] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0097] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0098] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes the electrolyte provided in the first aspect of the present invention. The electrolyte solution includes an electrolyte salt and a solvent.

[0099] In some embodiments, the electrolyte salt may be selected from the sodium salt. The electrolyte is selected from at least one of sodium hexafluorophosphate (NaPF6), sodium difluorooxalate borate (NaDFOB), sodium tetrafluoroborate (NaBF4), sodium dioxalate borate (NaBOB), sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide (NaFSI), sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI).

[0100] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0101] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0102] In some embodiments, the material of the separator base film can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0103] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0104] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0105] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0106] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0107] In some implementations, refer to Figure 2The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0108] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0109] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0110] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0111] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0112] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0113] Thirdly, this application provides an electrical device, including the secondary battery of the second aspect of this application.

[0114] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0115] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0116] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0117] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0118] Example

[0119] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0120] Example 1

[0121] 1. Preparation of the positive electrode sheet:

[0122] Sodium-nickel-iron-copper-manganese oxide cathode active material, polyvinylidene fluoride binder, and carbon black conductive agent were mixed in a weight ratio of 80:10:10, and then added to the solvent N-methylpyrrolidone and stirred until the system was homogeneous, yielding a cathode slurry with a solid content of 45%. The chemical formula of the sodium-nickel-iron-copper-manganese oxide cathode active material is: Na[Cu] 0.1 Fe 0.2 Ni 0.2 Mn 0.5 O2. The positive electrode slurry is evenly coated onto the surface of aluminum foil, and then transferred to a vacuum drying oven for complete drying. The resulting electrode sheet is rolled and then punched to obtain the positive electrode sheet.

[0123] 2. Preparation of the negative electrode sheet:

[0124] Carbon nanotube material and sodium carboxymethyl cellulose polymer binder were added to water at a weight ratio of 4:1.6 and stirred to form a uniform slurry with a solid content of 50%. The slurry was coated on the surface of copper foil and then transferred to a vacuum drying oven for complete drying. After that, it was punched to obtain the negative electrode sheet.

[0125] 3. Preparation of electrolyte:

[0126] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), sodium hexafluorophosphate, 1,3,5-trioxane, triethyl borate, and ethylene glycol diethyl ether were mixed uniformly at 25 °C to obtain an electrolyte, with the following mass percentages: 0.1% for 1,3,5-trioxane, 2.0% for triethyl borate, and 1 mol / L for sodium hexafluorophosphate.

[0127] 4. Separating membrane:

[0128] Polypropylene film is used as the separator.

[0129] 5. Preparation of sodium secondary batteries:

[0130] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The stacking process yields a bare cell. The cell is then packaged in an aluminum-plastic film casing and injected with the electrolyte. The process involves sealing, settling, hot and cold pressing, and formation to produce a stacked battery.

[0131] The parameters of Examples 2 to 27 and Comparative Examples 1 to 3 of this application are as specified in Table 1.

[0132] Performance testing:

[0133] The secondary batteries prepared in Examples 1 to 27 and Comparative Examples 1 to 3 were subjected to the following tests:

[0134] 1.1C discharge capacity retention:

[0135] The sodium secondary battery was charged at 25°C with a constant current of 1C to 3.65V, then charged at a constant voltage of 3.65V until the current dropped to 0.05C, and then discharged with a constant current of 1C to 2.0V. This is the initial discharge capacity (C1). This charging and discharging process was repeated until the nth cycle, and the discharge capacity of the sodium secondary battery after n cycles was obtained, denoted as C. n The capacity retention rate of sodium secondary batteries is calculated according to the following formula:

[0136] Capacity retention rate = discharge capacity after n cycles (C) n First-cycle discharge capacity (C1)

[0137] Capacity retention rate (C) after 200 cycles 200 / C1) is shown in Table 1.

[0138] 2.4C discharge capacity:

[0139] The sodium secondary battery was charged at 25°C with a constant current of 1C to 3.65V, then charged at a constant voltage of 3.65V until the current dropped to 0.05C, and then discharged at a constant current of 1C to 2.0V, yielding the first discharge capacity (C1). This charge-discharge cycle was repeated for 3 cycles. Then, the battery was charged at 25°C with a constant current of 4C to 3.65V, then charged at a constant voltage of 3.65V until the current dropped to 0.05C, and then discharged at a constant current of 4C to 2.0V. This charge-discharge cycle was repeated for 3 cycles, and the average discharge capacity of the 3 cycles was taken as the 4C discharge capacity C. 4D 4C discharge capacity retention (C 4D / C1) is shown in Table 1.

[0140]

[0141]

[0142] In Table 1, TEB refers to triethyl borate, TBB refers to tributyl borate, TPB refers to triphenyl borate, DEE represents ethylene glycol diethyl ether, DME represents ethylene glycol dimethyl ether, THF represents tetrahydrofuran, NaPF6 represents sodium hexafluorophosphate, NaFSI represents sodium difluorosulfonamide, and NaOTf represents sodium trifluoromethanesulfonate.

[0143] As can be seen from the results in Table 1, compared with Comparative Example 1 which did not add cyclic ether additives, Examples 1-27 of this application, which added cyclic ether additives to the electrolyte, can effectively improve the cycle performance and rate performance of the battery.

[0144] As can be seen from Examples 1-6, adjusting the amount of cyclic ether additives can better exert their effects. When the mass percentage of cyclic ether additives in the electrolyte is 1%-10%, it is more conducive to improving the cycle performance and rate performance of the battery.

[0145] As can be seen from Examples 3 and 26, adding cyclic ether additives to the electrolyte followed by borate ester additives can further and effectively improve the cycle performance and rate performance of the battery.

[0146] As can be seen from Examples 7-11, adjusting the amount of borate ester additives can better leverage their effects and further improve the battery's cycle performance and rate performance. Specifically, when the mass percentage of borate ester additives in the electrolyte is 1%-10%, it is even more beneficial to improve the battery's cycle performance and rate performance.

[0147] As can be seen from Examples 12-15 and 23-25, by adjusting the combination of cyclic ether additives and borate ester additives, the cycle performance and rate performance of the battery can be further improved effectively.

[0148] As can be seen from Examples 16-17, using different solvents can improve the cycle performance and rate performance of the battery.

[0149] As can be seen from Examples 18-22, the cycle performance and rate performance of the battery can be improved by adjusting the concentration or type of sodium salt.

[0150] As can be seen from the comparison between Examples 1-25 and Comparative Example 2, the addition of only borate ester additives to the electrolyte of Comparative Example 2 has limited effect on improving the cycle performance and rate performance of the battery. Its effect is not as good as simultaneously adding cyclic ether additives and borate ester additives to the electrolyte.

[0151] As can be seen from the comparison between Example 27 and Comparative Example 3, both additives in Example 27 and Comparative Example 3 contain 3 carbon-oxygen bonds. However, due to the weak coordination effect of the structure connecting two carbon atoms between two oxygen atoms on sodium ions, the 18-crown ether-6 used in Comparative Example 3 has limited effect on improving the cycle performance and rate performance of the battery, and its effect is not as good as that of Example 27.

[0152] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. An electrolyte, characterized in that, Including cyclic ether additives as shown in Formula I; Where n is a positive integer from 1 to 20, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, or alkyl groups having 1 to 6 carbon atoms.

2. The electrolyte according to claim 1, characterized in that, n is a positive integer from 1 to 5, and R1, R2, and R3 each independently include any one of hydrogen, fluorine, nitro, or alkyl groups with 1 to 4 carbon atoms.

3. The electrolyte according to claim 1 or 2, characterized in that, The cyclic ether additives include at least one of the compounds shown in Formula I-1 to Formula I-22:

4. The electrolyte according to any one of claims 1-3, characterized in that, The cyclic ether additives constitute 0.1%-10% of the electrolyte by mass.

5. The electrolyte according to claim 4, characterized in that, The cyclic ether additives constitute 1% to 10% of the mass of the electrolyte.

6. The electrolyte according to any one of claims 1-5, characterized in that, The electrolyte also includes borate ester additives as shown in Formula II. L1, L2, and L3 each independently include any one of alkyl groups, substituted or unsubstituted phenyl groups having 1 to 4 carbon atoms.

7. The electrolyte according to claim 6, characterized in that, The borate ester additives include at least one of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, and triphenyl borate.

8. The electrolyte according to claim 6 or 7, characterized in that, The borate ester additive accounts for 0.1%-10% of the mass of the electrolyte.

9. The electrolyte according to claim 8, characterized in that, The borate ester additive accounts for 1%-10% of the mass of the electrolyte.

10. The electrolyte according to any one of claims 1-9, characterized in that, The electrolyte further includes a solvent, which includes at least one of diethyl ether, dipropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, and methyltetrahydrofuran.

11. The electrolyte according to any one of claims 1-10, characterized in that, The electrolyte also includes a sodium salt, which includes at least one of sodium tetrafluoroborate, sodium hexafluorophosphate, sodium hexafluoroarsenate, sodium perchlorate, sodium difluorooxalate borate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

12. The electrolyte according to claim 11, characterized in that, The concentration of the sodium salt in the electrolyte is 0.1-3 mol / L.

13. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1-12.

14. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 13.

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