Electrolyte, sodium-ion battery and electric device

Abstract

Provided in the present application are an electrolyte, a sodium-ion battery and an electric device. The electrolyte comprises S-containing anions and B-containing anions, wherein the S-containing anions comprise at least one of N(FSO2)2 - and N(CF3SO2)2 -, and the B-containing anions comprise at least one of B(F2C2O4)- and BF4 -. The molar ratio of S to B in the electrolyte is (2-20) : 1. When the electrolyte is applied to a sodium-ion battery, a solid electrolyte interface film (SEI film) containing S and B is formed on the surface of a negative electrode of the battery; and the SEI film can give consideration to a relatively high sodium-ion transmission rate and relatively good toughness and is beneficial to improving the storage capacity retention rate of the sodium-ion battery.

Description

Electrolyte, sodium ion battery, and electrical device

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2023102895388, filed on March 23, 2023, entitled “Electrolyte, Sodium Ion Battery and Electrical Device,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to an electrolyte, a sodium ion battery, and an electrical device. Background Art

[0004] [Deleted, Rule 91, 13.11.2024]

[0005] As a secondary battery, sodium-ion batteries rely primarily on the movement of sodium ions between the positive and negative electrodes to function. In the field of secondary batteries, sodium-ion batteries offer significant cost advantages, which has broadened their application. However, their storage capacity retention needs to be further improved.

[0006] Summary of the Invention

[0007] The present application provides an electrolyte. The electrolyte includes anions containing S and anions containing B, and the anions containing S include N(FSO2)2 - and N(CF3SO2)2 - At least one of the following, wherein the B-containing anion comprises B(F2C2O4) - and BF4 - At least one of the above, the molar ratio of S element to B element in the electrolyte is (2-20):1.

[0008] The electrolyte of the present application includes corresponding S-containing anions and B-containing anions, as well as S elements and B elements in corresponding molar ratios. When the electrolyte is applied to a sodium ion battery, a solid electrolyte interface film (SEI film) containing S elements and B elements is formed on the negative electrode surface of the battery. The SEI film can take into account both a relatively efficient sodium ion transmission rate and good toughness, which helps to improve the storage capacity retention rate of the sodium ion battery.

[0009] In some embodiments, in the electrolyte, the molar concentration of the S element is 1 mol / L to 4 mol / L, and the molar concentration of the B element is 0.1 mol / L to 1 mol / L.

[0010] In some embodiments, the electrolyte further contains at least one of F element and N element.

[0011] In some embodiments, the electrolyte contains F element and N element, wherein the molar ratio of F element to N element is (2-10):1.

[0012] In some embodiments, in the electrolyte, the molar concentration of the F element is 1.4 mol / L to 6.8 mol / L, and the molar concentration of the N element is 0.5 mol / L to 2 mol / L.

[0013] In some embodiments, the electrolyte includes a S-containing sodium salt and a B-containing sodium salt.

[0014] In some embodiments, the S-containing sodium salt includes at least one of sodium bis(fluoromethylsulfonyl)imide and sodium bis(trifluoromethylsulfonyl)imide.

[0015] In some embodiments, the B-containing sodium salt includes at least one of sodium difluorooxalatoborate and sodium tetrafluoroborate.

[0016] In some embodiments, the electrolyte further includes an additive, wherein the additive includes an alkyl sodium salt.

[0017] In some embodiments, the alkyl sodium salt includes at least one of sodium lauryl sulfate and sodium polydipropylene glycol sulfonate.

[0018] In some embodiments, the molar concentration of the additive is 0.0015 mol / L to 0.015 mol / L.

[0019] In some embodiments, the solvent in the electrolyte includes at least one of ethylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, ethyl propionate, methyl propionate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran and methyltetrahydrofuran.

[0020] The present application also provides a sodium ion battery comprising the above-mentioned electrolyte.

[0021] The present application also provides an electrical device comprising the above-mentioned sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the optional embodiments below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0023] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0024] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0025] FIG3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0026] Description of reference numerals:

[0027] 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Top cover assembly; 2. Electrical device. DETAILED DESCRIPTION

[0028] Below, the embodiments of the battery assembly, battery cell, secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0029] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] [Rule 91, 13.11.2024] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, or may be performed sequentially. For example, a statement that the method comprises steps (a) and (b) indicates that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, a statement that the method may further comprise step (c) indicates that step (c) may be added to the method in any order, for example, the method may comprise steps (a), (b) and (c), or may comprise steps (a), (c) and (b), or may comprise steps (c), (a) and (b), etc.

[0033] [Deleted, Rule 91, 13.11.2024]

[0034] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true or present, and B is false or absent; A is false or absent, and B is true or present; or both A and B are true, or both A and B are present.

[0035] Unless otherwise specified, in this application, the terms "positive electrode sheet" and "positive electrode sheet" have the same meaning and can be used interchangeably. The terms "negative electrode sheet" and "negative electrode sheet" have the same meaning and can be used interchangeably. The terms "diaphragm" and "separator" have the same meaning and can be used interchangeably.

[0036] One embodiment of the present application provides an electrolyte. The electrolyte includes anions containing S and anions containing B, and the anions containing S include N(FSO2)2 - and N(CF3SO2)2 - At least one of the B anions including B(F2C2O4) - and BF4 -At least one of the elements, the molar ratio of the S element to the B element in the electrolyte is (2 to 20): 1. The electrolyte includes corresponding S-containing anions and B-containing anions, as well as S elements and B elements in corresponding molar ratios. When the electrolyte is applied to a sodium ion battery, a solid electrolyte interface film (SEI film) containing S elements and B elements is formed on the negative electrode surface of the battery. The SEI film can take into account both a more efficient sodium ion transmission rate and better toughness, which helps to improve the storage capacity retention rate of the sodium ion battery. When the molar ratio of the S element to the B element is too large, the toughness of the SEI film may be poor, and it may be prone to rupture and damage during the cycle, resulting in poor electrical performance. When the molar ratio of the S element to the B element is too small, the transmission rate of sodium ions in the SEI film may deteriorate, resulting in increased impedance and increased polarization, which in turn leads to a decrease in electrical performance.

[0037] It is understood that the S element and the B element in the electrolyte can be provided by S anions and B anions. Further optionally, the S anions serve as the source of the S element, and the B anions serve as the source of the B element. It is also understood that the electrolyte may contain other substances containing the S element and / or the B element, which can also provide a certain amount of the S element and the B element.

[0038] As some optional examples of the molar ratio of the S element and the B element, the molar ratio of the S element and the B element can be, but is not limited to, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, etc. It will be understood that the molar ratio of the S element and the B element can also be selected within the range of (2 to 20):1. Further, the molar ratio of the S element and the B element can be selected from the molar ratios of the S element and the B element described in the Examples below in this application.

[0039] As examples of molar concentrations of element S and element B in the electrolyte, the molar concentration of element S in the electrolyte is 1 mol / L to 4 mol / L, and the molar concentration of element B is 0.1 mol / L to 1 mol / L. Alternatively, the molar concentration of element S in the electrolyte is 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, 4 mol / L, etc. Alternatively, the molar concentration of element B in the electrolyte is 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, etc. It is understood that in the electrolyte, the molar concentration of the S element can also be selected in the range of 1 mol / L to 4 mol / L. In the electrolyte, the molar concentration of the B element can also be selected in the range of 0.1 mol / L to 1 mol / L. Furthermore, in the electrolyte, the molar concentration of the S element can also be selected from the molar concentrations of the S element described in the examples below in this application. In the electrolyte, the molar concentration of the B element can also be selected from the molar concentrations of the B element described in the examples below in this application.

[0040] It will be understood that the types and molar concentrations of elements in this application can be measured with reference to Inductively Coupled Plasma Atomic Emission Spectrometry (EPA 6010D-2018), Inductively Coupled Plasma Atomic Emission Spectrometry General Rules (JY / T 0567-2020) or Lithium Hexafluorophosphate Product Analysis Method (GBT19282-2014). For example, after the sample is pre-treated, the type and molar concentration of the element are obtained by inductively coupled plasma atomic emission spectrometry. Optionally, the test method includes: (1) accurately measuring 5 mL of fresh electrolyte sample into a digestion tank, and recording the sample weight after the balance number stabilizes; (2) slowly adding 10 mL of concentrated HNO3, flushing the sample on the inner wall into the bottom of the tank, and gently shaking the digestion tank; (3) placing the digestion tank in an acid removal instrument and digesting at 180°C for about 30 minutes; (4) when the solution evaporates to 1-2 mL, remove the digestion tank and cool it to room temperature, rinse the tank with ultrapure water 3 times, pour the rinse solution into a 50 mL plastic volumetric flask to make up the volume, and shake it evenly; (5) using inductively coupled plasma atomic emission spectrometry to test the solution after making up the volume.

[0041] It is understood that the types and molar concentrations of ions in this application can refer to standards JY / T 020-1996 and GB / T36240-2018, and the ion components in the electrolyte are quantitatively analyzed by ion chromatography analysis.

[0042] Furthermore, the electrolyte also contains at least one of the F element and the N element. Optionally, the molar ratio of the F element and the N element is (2-10):1. For example, the molar ratio of the F element and the N element can be, but is not limited to, 2.1:1, 2.2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, etc. It will be understood that the molar ratio of the F element and the N element can also be selected from other options within the range of (2-10):1. Optionally, the molar ratio of the F element and the N element is (2-6.8):1. Further, the molar ratio of the F element and the N element can also be selected from other options within the molar ratio of the F element and the N element described in the embodiments below in this application.

[0043] Specifically, optionally, in the electrolyte, the molar concentration of the F element is 1.4 mol / L to 6.8 mol / L, and the molar concentration of the N element is 0.5 mol / L to 2 mol / L. Alternatively, in the electrolyte, the molar concentration of the F element is 1.4 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 6.8 mol / L, etc. Of course, in the electrolyte, the molar concentration of the F element can also be selected from the molar concentrations of the F element described in the embodiments below in this application. Optionally, in the electrolyte, the molar concentration of the N element is 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, etc. It will be appreciated that in the electrolyte, the molar concentration of the N element may also be selected within the range of 0.5 mol / L to 2 mol / L. Of course, in the electrolyte, the molar concentration of the N element may also be selected within the molar concentrations of the N element described in the embodiments below.

[0044] In some embodiments, the electrolyte includes a sodium salt containing S and a sodium salt containing B. Optionally, the sodium salt containing S includes at least one of sodium bis(fluorosulfonyl)imide (N(FSO2)2Na) and sodium bis(trifluoromethylsulfonyl)imide (N(CF3SO2)2Na), and the sodium salt containing B includes at least one of sodium difluorooxalatoborate (B(F2C2O4)Na) and sodium tetrafluoroborate (BF4Na).

[0045] Alternatively, the molar ratio of the sodium salt containing S and the sodium salt containing B is (1 to 10): 1. Further optionally, the molar ratio of the sodium salt containing S and the sodium salt containing B is 1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.5: 1, 4: 1, 4.5: 1, 5: 1, 5.5: 1, 6: 1, 6.5: 1, 7: 1, 7.5: 1, 8: 1, 8.5: 1, 9: 1, 9.5: 1, 10: 1, etc. It is understood that the molar ratio of the sodium salt containing S and the sodium salt containing B can also be selected in the range of (1 to 10): 1. Of course, the molar ratio of the sodium salt containing S and the sodium salt containing B can also be selected in the molar ratio of the sodium salt containing S and the sodium salt containing B described in the examples below in this application.

[0046] Optionally, the molar concentration of the sodium salt containing S is 0.5mol / L to 2mol / L, and the molar concentration of the sodium salt containing B is 0.1mol / L to 1mol / L. Optionally, the molar concentration of the sodium salt containing S is 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L, 1.6mol / L, 1.7mol / L, 1.8mol / L, 1.9mol / L, 2mol / L, etc. Optionally, the molar concentration of the sodium salt containing B is 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, etc.

[0047] [Rule 91, 13.11.2024] In some embodiments, the electrolyte further includes an additive, comprising an alkyl sodium salt. The alkyl sodium salt additive can promote electrolyte wetting on the negative electrode surface, thereby reducing the internal resistance of the battery and further improving the battery's storage capacity retention. Optionally, the alkyl sodium salt comprises at least one of sodium lauryl sulfate and sodium polydisulfide dipropane sulfonate. Further optionally, the molar concentration of the additive is 0.0015 mol / L to 0.015 mol / L. For example, the molar concentration of the additive can be, but is not limited to, 0.0015 mol / L, 0.0018 mol / L, 0.002 mol / L, 0.0025 mol / L, 0.003 mol / L, 0.0035 mol / L, 0.004 mol / L, 0.0045 mol / L, 0.005 mol / L, 0.0055 mol / L, 0.006 mol / L, 0.0065 mol / L, 0.007 mol / L, 0.0075 mol / L, 0.008 mol / L, 0.0085 mol / L, 0.009 mol / L, 0.0095 mol / L, 0.01 mol / L, 0.012 mol / L, 0.015 mol / L, etc. It will be appreciated that the molar concentration of the additive can also be selected within the range of 0.0015 mol / L to 0.015 mol / L. Of course, the molar concentration of the additive can also be selected from other molar concentrations of the additive described in the examples below in this application.

[0048] In some embodiments, the electrolyte further comprises a solvent, and the solvent comprises at least one of ethylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, ethyl propionate, methyl propionate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, and methyltetrahydrofuran. Alternatively, the solvent comprises propylene carbonate and dimethyl carbonate. Further optionally, the volume ratio of propylene carbonate and dimethyl carbonate is (0.5 to 1.5): 1. For example, the volume ratio of propylene carbonate and dimethyl carbonate can be, but is not limited to, 0.5: 1, 0.6: 1, 0.7: 1, 0.8: 1, 0.9: 1, 1: 1, 1.1: 1, 1.2: 1, 1.3: 1, 1.4: 1, and 1.5: 1. Optionally, the molecular weight of polyethylene glycol dimethyl ether is 250-320.

[0049] Another embodiment of the present application provides a sodium ion battery. The sodium ion battery includes the above-mentioned electrolyte.

[0050] Another embodiment of the present application provides an electrical device comprising the sodium ion battery.

[0051] Hereinafter, the secondary battery will be described with reference to the relevant drawings.

[0052] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0053] [Positive electrode]

[0054] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0055] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0056] In some embodiments, the positive electrode 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 material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. Alternatively, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. Alternatively, the polymer material substrate may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0057] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may adopt the positive electrode active material for lithium-ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Optionally, lithium cobalt oxide includes LiCoO2. Lithium nickel oxide includes LiNiO2. Lithium manganese oxide includes at least one of LiMnO2 and LiMn2O4. Lithium nickel cobalt manganese oxide includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 ) and LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ) at least one of. Lithium nickel cobalt aluminum oxide includes LiNi 0.85 Co 0.15 Al 0.05 Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Optionally, the lithium iron phosphate includes LiFePO4 (LFP). The lithium manganese phosphate includes LiMnPO4.

[0058] In some embodiments, when the secondary battery is a sodium ion battery, the positive electrode active material may adopt the positive electrode active material for sodium ion batteries known in the art. As an example, the positive electrode active material may be used alone or in combination of two or more. Among them, the positive electrode active material may be selected from sodium iron composite oxide, sodium cobalt composite oxide, sodium chromium composite oxide, sodium manganese composite oxide, sodium nickel composite oxide, sodium nickel titanium composite oxide, sodium nickel manganese composite oxide, sodium iron manganese composite oxide, sodium nickel cobalt manganese composite oxide, sodium iron phosphate compound, sodium manganese phosphate compound, sodium cobalt phosphate compound, sodium nickel iron manganese composite oxide, Prussian blue material, polyanion material, etc., but the present application is not limited to these materials, and the present application may also use other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries. Optionally, sodium iron composite oxide includes NaFeO2. Sodium cobalt composite oxide includes NaCoO2. Sodium chromium composite oxide includes NaCrO2. Sodium manganese composite oxide includes NaMnO2. Sodium nickel composite oxide includes NaNiO2. Sodium nickel titanium composite oxide includes NaNi 1 / 2 Ti 1 / 2 O2. Sodium nickel manganese composite oxide includes NaNi 1 / 2 Mn 1 / 2 O2. Sodium iron manganese composite oxide includes Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. Sodium nickel cobalt manganese composite oxides include NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. Sodium iron phosphate includes NaFePO4. Sodium manganese phosphate includes NaMnPO4. Sodium cobalt phosphate includes NaCoPO4. The polyanion material includes at least one of phosphate, fluorophosphate, pyrophosphate and sulfate.

[0059] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0060] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, 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.

[0061] In some embodiments, the positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and performing drying, cold pressing, and other processes to obtain the positive electrode sheet. Optionally, the solvent includes N-methylpyrrolidone.

[0062] [Negative electrode]

[0063] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0064] As an example, the negative electrode current collector has two surfaces opposite to each other in its 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.

[0065] 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 base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material on a polymer base material. Optionally, the metal material includes at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0066] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0067] In some embodiments, the negative electrode film layer may further 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), carboxymethyl chitosan (CMCS), polyamide-imide (PAI), polyethyleneimine (PEI), polyimide (PI), and poly-tert-butyl acrylate-triethoxyvinylsilane (TBATEVS).

[0068] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0069] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener. Optionally, the thickener includes sodium carboxymethyl cellulose (CMC-Na).

[0070] In some embodiments, the negative electrode sheet can be prepared by dispersing the aforementioned components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and performing drying, cold pressing, and other processes to obtain the negative electrode sheet. Optionally, the solvent includes deionized water.

[0071] [Electrolytes]

[0072] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0073] In some embodiments, the electrolyte is an electrolytic solution.

[0074] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0075] [Isolation film]

[0076] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0077] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0078] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0079] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0080] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0081] The present application does not particularly limit the shape of the secondary battery, which can be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 1 having a square structure as an example. It is understood that the secondary battery 1 can be a sodium ion battery.

[0082] [Article 91 of the Detailed Rules, 13.11.2024] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a top cover assembly 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the top cover assembly 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the secondary battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0083] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0084] In addition, the present application also provides an electrical device, which includes the secondary battery provided by the present application. The secondary battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. For example, mobile devices include mobile phones, laptops, etc. Electric vehicles include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0085] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0086] Fig. 3 shows an example of an electric device 2. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0087] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0088] Example

[0089] Example 1

[0090] In this embodiment, the electrolyte includes a sodium salt containing sulfur, a sodium salt containing boron, and a solvent. The sodium salt containing sulfur is sodium bis(fluorosulfonyl)imide (NaFSI), and the sodium salt containing boron is sodium difluorooxalatoborate (NaDFOB). In the electrolyte, the molar concentration of the sodium salt containing sulfur is 0.5 mol / L, the molar concentration of the sodium salt containing boron is 0.2 mol / L, and the molar ratio of the sulfur element to the boron element is 5:1. The solvent is a mixed solvent of propylene carbonate and dimethyl carbonate in a volume ratio of 1:1.

[0091] Examples 2 to 11

[0092] Compared with Example 1, Examples 2 to 4 differ in that one or more of the molar concentration of the sodium salt containing sulfur, the molar concentration of the sodium salt containing boron, and the corresponding molar ratio of the element sulfur to the element boron in the electrolyte are different, as shown in Table 1.

[0093] Examples 12-13

[0094] Compared with Example 2, Examples 12 to 13 differ in that the solvents in the electrolyte are different.

[0095] Example 14

[0096] In this embodiment, the electrolyte includes a sodium salt containing sulfur, a sodium salt containing boron, an additive, and a solvent. The sodium salt containing sulfur is sodium bis(fluorosulfonyl)imide (NaFSI), and the sodium salt containing boron is sodium difluorooxalatoborate (NaDFOB). In the electrolyte, the molar concentration of the sodium salt containing sulfur is 0.5 mol / L, the molar concentration of the sodium salt containing boron is 0.2 mol / L, and the molar ratio of the sulfur element to the boron element is 5:1. The solvent is a mixed solvent of propylene carbonate and dimethyl carbonate in a volume ratio of 1:1. The additive is sodium polydisulfide dipropylene sulfonate, and the molar concentration of the additive in the electrolyte is 0.003 mol / L.

[0097] Examples 15 to 32

[0098] Compared with Example 14, Examples 15 to 32 differ in one or more of the molar concentration of the S-containing sodium salt, the molar concentration of the B-containing sodium salt, the molar ratio of the S element to the B element, the additive and its molar concentration, and the type of solvent, as shown in Table 1.

[0099] Comparative Examples 1-2

[0100] Compared with Example 1, the differences between Comparative Examples 1 and 2 are that the molar concentration of the S-containing sodium salt, the molar concentration of the B-containing sodium salt, and the molar ratio of the S element to the B element are different.

[0101] Comparative Examples 3-4

[0102] Compared with Example 14, the differences between Comparative Examples 3 and 4 are that the molar concentration of the S-containing sodium salt, the molar concentration of the B-containing sodium salt, and the molar ratio of the S element to the B element are different.

[0103] Comparative Example 5

[0104] Compared with Example 1, the difference of Comparative Example 5 is that the sodium salt containing S in the electrolyte is replaced by a sodium salt containing B in an equimolar concentration.

[0105] Comparative Example 6

[0106] Compared with Example 1, the difference of Comparative Example 6 is that the sodium salt containing B in the electrolyte is replaced by a sodium salt containing S in an equimolar concentration.

[0107] Comparative Example 7

[0108] Compared with Example 14, the difference in Comparative Example 7 is that the sodium salt containing S in the electrolyte is replaced by a sodium salt containing B in an equimolar concentration.

[0109] Comparative Example 8

[0110] Compared with Example 14, the difference in Comparative Example 8 is that the sodium salt containing B in the electrolyte is replaced by a sodium salt containing S in an equimolar concentration.

[0111] Comparative Example 9

[0112] Compared with Example 1, the difference of Comparative Example 9 is that the sodium salt containing S and the sodium salt containing B in the electrolyte are replaced by sodium hexafluorophosphate with equimolar concentrations.

[0113] Comparative Example 10

[0114] Compared with Example 11, the difference in Comparative Example 10 is that the S-containing sodium salt and the B-containing sodium salt in the electrolyte are replaced by sodium hexafluorophosphate with equimolar concentrations.

[0115] In Table 1, the unit of molar concentration is mol / L, which represents the molar concentration in the electrolyte.

[0116] Test Case

[0117] (1) Preparation of positive electrode sheets.

[0118] Dissolve 10wt% polyvinylidene fluoride binder in N-methylpyrrolidone, add 10wt% carbon black conductive agent, and 80wt% sodium nickel iron manganese oxide positive electrode active material to create a uniformly dispersed slurry. Apply the slurry evenly to the surface of 60μm aluminum foil and transfer it to a vacuum drying oven for complete drying. The resulting electrode sheet is roll-pressed and then punched to produce the positive electrode sheet.

[0119] (2) Preparation of negative electrode sheets.

[0120] The negative electrode active material hard carbon, conductive agent acetylene black, binder SBR and thickener CMC were dissolved in deionized water in a weight ratio of 94:2:2.8:1.2, stirred evenly to form a negative electrode slurry, and then prepared into a slurry after ultrasonic dispersion. The slurry was then coated on the surface of a 12μm copper foil and then transferred to a vacuum drying oven for complete drying to prepare a negative electrode sheet.

[0121] (3) Preparation of electrolyte.

[0122] In an argon atmosphere glove box with H2O<0.1ppm and O2<0.1ppm, the raw materials for preparing the electrolytes in the examples and comparative examples were mixed and stirred uniformly to prepare an electrolyte.

[0123] (4) Isolation membrane.

[0124] Polypropylene film is used as the isolation film.

[0125] (5) Preparation of sodium ion batteries.

[0126] The positive electrode sheet in (1), the separator in (4), and the negative electrode sheet in (2) are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. The electrolyte in (3) is added to assemble a laminated battery.

[0127] (6) Storage capacity retention test.

[0128] The sodium ion battery prepared in (5) was charged to 4V at a constant current of 0.2C at 25°C, then charged at a constant voltage of 4V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 0.2C to obtain the discharge capacity before storage (Cd1); then the battery was charged to 4V at a constant current of 0.2C again, and then charged at a constant voltage of 4V until the current dropped to 0.05C. The battery was then stored in a 60°C constant temperature box for 30 days. After being taken out, the battery was placed at 25°C and charged to 4V at a constant current of 0.2C, then charged at a constant voltage of 4V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 0.2C to obtain the discharge capacity after storage (Cd2). The capacity retention rate of the sodium ion battery was calculated according to the following formula:

[0129] Storage capacity retention rate = discharge capacity after storage (Cd2) / discharge capacity before storage (Cd1) × 100%. The results are shown in Table 1.

[0130] (7) Cycle capacity retention rate.

[0131] The sodium ion battery prepared in (5) was charged to 3.7 V at a constant current of 0.2 C at 25 ° C, then charged at a constant voltage of 3.7 V until the current dropped to 0.05 C, and then discharged to 2.5 V at a constant current of 0.2 C to obtain the first cycle discharge capacity (Cd3); this charge and discharge was repeated until the nth cycle, and the discharge capacity of the sodium ion battery after n cycles was obtained, which was recorded as Cdn, and the capacity retention rate of the sodium ion battery was calculated according to the following formula:

[0132] Cycle capacity retention rate = discharge capacity after n cycles (Cdn) / first cycle discharge capacity (Cd3). The cycle capacity retention rate after 20 cycles is shown in Table 1.

[0133] Table 1

[0134] It is understandable that, since the additive may contain a certain amount of S element, the content of S element in the electrolyte when the additive is present may be slightly higher than the content of S element in the electrolyte without the additive.

[0135] It can be seen from Examples 1 to 32 and Comparative Examples 5 to 8 in Table 1 that when the electrolyte contains both S and B elements, the corresponding sodium ion battery exhibits better storage capacity retention and cycle capacity retention. It can be seen from Examples 1 to 32 and Comparative Examples 1 to 4 that when the electrolyte contains both S and B elements, and the molar ratio of S and B elements is (2 to 20): 1, the corresponding sodium ion battery exhibits better storage capacity retention and cycle capacity retention. It can be seen from Examples 28 to 30 that when the electrolyte contains additives, the storage capacity retention and cycle capacity retention of the corresponding sodium ion battery are better, and when the molar concentration of the additive is 0.0015 mol / L to 0.015 mol / L, the corresponding sodium ion battery exhibits better storage capacity retention and cycle capacity retention.

[0136] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: including S-containing anions and B-containing anions, wherein the S-containing anions include N(FSO2)2 - and N(CF3SO2)2 - At least one of the following, wherein the B-containing anion comprises B(F2C2O4) - and BF4 - At least one of the above, the molar ratio of S element to B element in the electrolyte is (2-20):

1.

2. The electrolyte according to claim 1, characterized in that In the electrolyte, the molar concentration of the S element is 1 mol / L to 4 mol / L, and the molar concentration of the B element is 0.1 mol / L to 1 mol / L.

3. The electrolyte according to claim 1 or 2, characterized in that The electrolyte further contains at least one of F element and N element.

4. The electrolyte according to claim 3, characterized in that The electrolyte contains F element and N element, wherein the molar ratio of F element to N element is (2-10):

1.

5. The electrolyte according to claim 4, characterized in that In the electrolyte, the molar concentration of the F element is 1.4 mol / L to 6.8 mol / L, and the molar concentration of the N element is 0.5 mol / L to 2 mol / L.

6. The electrolyte according to any one of claims 1 to 5, characterized in that It includes S-containing sodium salt and B-containing sodium salt.

7. The electrolyte according to claim 6, characterized in that The sulfur-containing sodium salt includes at least one of sodium bis(trifluoromethylsulfonyl)imide and sodium bis(trifluoromethylsulfonyl)imide.

8. The electrolyte according to claim 6 or 7, characterized in that The B-containing sodium salt includes at least one of sodium difluorooxalatoborate and sodium tetrafluoroborate.

9. The electrolyte according to any one of claims 6 to 8, characterized in that It also includes an additive, and the additive includes an alkyl sodium salt.

10. The electrolyte according to claim 9, characterized in that The alkyl sodium salt includes at least one of sodium lauryl sulfate and sodium polydipropylene sulfonate.

11. The electrolyte according to claim 9 or 10, characterized in that The molar concentration of the additive is 0.0015 mol / L to 0.015 mol / L.

12. The electrolyte according to any one of claims 1 to 11, characterized in that The solvent in the electrolyte includes at least one of ethylene carbonate, propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, ethyl propionate, methyl propionate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran and methyltetrahydrofuran.

13. A sodium ion battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 12.

14. An electrical device, characterized in that: Including the sodium ion battery as described in claim 13.

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