Electrolyte and sodium ion secondary battery, battery pack, battery module and power consumption device including the electrolyte

Abstract

The present application provides an electrolyte for a sodium ion secondary battery, in which a first additive, a low-boiling sulfur-containing compound, and a second additive, a salt containing oxalate (a compound of formula (I)) and / or an oxalic acid ester (a compound of formula (II)), are used in combination in the electrolyte to form a stable interfacial passivation film on the positive and negative electrodes, thereby improving the self-discharge rate and cycle performance of the battery while simultaneously achieving good power performance. The present application further relates to a sodium ion secondary battery, a battery module, a battery pack, and a power consumption device including the same. [Formula 1] JPEG2025515804000008.jpg31170

Description

[Technical field]

[0001] The present application relates to the field of secondary battery technology, and in particular to an electrolyte, a sodium ion secondary battery containing the electrolyte, a battery pack, a battery module and a power consuming device. [Background technology]

[0002] Sodium ion secondary batteries are an energy storage battery system with great potential due to the abundant sodium resources and advantages such as low cost, and their structure includes positive and negative electrodes that can sorb and release sodium ions, and an electrolyte that transports sodium ions. Currently, sodium ion secondary batteries generally use carbonate ester as a solvent for the electrolyte, which makes the interface passivation film formed between the negative and positive electrodes unstable, resulting in severe self-discharge phenomenon in sodium ion secondary batteries and poor cycle performance.

[0003] Therefore, the development and design of a sodium-ion secondary battery that improves the self-discharge rate and cycle performance has great practical value. Summary of the Invention

[0004] The present application has been made in view of the above problems, and aims to provide an electrolyte that can effectively improve the self-discharge and cycle performance of a battery, and to provide a sodium ion secondary battery, a battery module, a battery pack, and a power consuming device that each contain the electrolyte of the present application.

[0005] In order to achieve the above object, the present application provides an electrolyte solution, the electrolyte solution comprising an electrolyte sodium salt, an organic solvent, and an additive, wherein the additive comprises: a) a first additive which is at least one selected from sulfur-containing compounds having a boiling point of 70° C. or less; b) a second additive which is at least one selected from an oxalate-containing salt or an oxalic acid ester; Here, the salt containing oxalate is bis(oxalato)borate (C 4 O8 B) n (M n+ ), difluoro(oxalato)borate (C 2 O 4 F 2 B) n (M n+ ), difluorobis(oxalato)phosphate (C 2 O 8 F 2 P) n (M n+ ), tetrafluoro(oxalato)phosphate (C 2 O 4 F 4 P) n (M n+ ), ethyl (oxalato) salt (C 2 O 4 C 2 H 5 ) n (M n+ ), oxalate (C 2 O 4 ) n / 2 (M n+ ), and M n+ is a metal cation and / or an organic cation, optionally an alkali metal ion, an alkaline earth metal ion, an aluminum ion or an ammonium ion NH 4 + and optionally a sodium ion, a lithium ion, a potassium ion, a magnesium ion or an aluminum ion, further optionally a sodium ion, a lithium ion, a potassium ion, and n is 1, 2 or 3, and optionally 1 or 2; The oxalic acid ester is at least one selected from the following compounds of formula (I) and formula (II): [ka] Here, R 1 , R 2 are each independently C 1 -C 10 Alkyl group, C 2 -C 10 Alkenyl group, C 1-C 10 Alkylene phenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 Alkylcarbonyl group, C 2 -C 10 Alkyleneamino group, C 1 -C 10 Alkyleneoxyphenyl group or C 1 -C 10 alkylsulfonyl groups, wherein said C 1 -C 10 Alkyl group, C 2 -C 10 Alkenyl group, C 1 -C 10 Alkylene phenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 Alkylcarbonyl group, C 2 -C 10 Alkyleneamino group, C 1 -C 10 Alkyleneoxyphenyl group or C 1 -C 10 The alkylsulfonyl group is optionally substituted with one or more substituents selected from halogen atoms, sulfonic acid groups, or nitro groups, and optionally R 1 , R 2 are each independently C 1 -C 4 alkyl groups, The halogen atom is one or more selected from F, Cl and Br; R 3 and R 4 Let's go together 1 -C 20 Alkylene group or C 2 -C 10 Forming an alkenylene group, 1 -C 20 Alkylene group, C 2 -C 10 The alkenylene group may optionally include a halogen atom, a nitro group, an amino group, a carboxyl group, a sulfonic acid group, a C 1 -C10 Alkylcarbonyl group, C 1 -C 10 Alkyl sulfonyl group, phenyl group, C 1 -C 10 Alkylene phenyl group, C 1 -C 10 Alkyleneoxyphenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 alkylene sulfonic acid groups, optionally substituted with one or more substituents selected from R 3 and R 4 Together - (CH 2 ) m -, and m is an integer from 2 to 15.

[0006] By using the first additive and the second additive in combination in the electrolyte, a stable interface passivation film composed mainly of an inorganic salt is formed on the positive and negative electrodes, thereby improving the self-discharge and cycle performance of the sodium-ion secondary battery while also achieving good power performance.

[0007] In any embodiment, in the electrolyte of the present application, the oxalate-containing salt in the second additive is selected from lithium bis(oxalato)borate, sodium difluoro(oxalato)borate, lithium oxalate, lithium difluorobis(oxalato)phosphate, sodium tetrafluoro(oxalato)phosphate, or a mixture thereof, the compound of formula (I) is selected from dimethyl oxalate, diethyl oxalate, diphenyl oxalate, dipropenyl oxalate, or a mixture thereof, and the compound of formula (II) is 1,4-dioxane-2,3-dione and / or 1,4-dioxacycloheptadecane-2,3-dione.

[0008] This is advantageous in further optimizing the composition of the electrolyte, forming a stable interfacial passivation film on the positive electrode, preventing sodium alkyl carbonate from reacting on the positive electrode, stabilizing the positive electrode potential, and suppressing the self-discharge phenomenon of the positive electrode.

[0009] In any embodiment, in the electrolyte of the present application, the first additive is selected from sulfur hexafluoride, sulfur tetrafluoride, sulfuryl fluoride, sulfur dioxide, sulfur trioxide, carbon disulfide, dimethyl sulfide, methyl ethyl sulfide, sulfur monofluoride, sulfur difluoride, thionyl fluoride and tetrafluorothionyl or a mixture thereof, and optionally selected from sulfur hexafluoride, sulfur tetrafluoride, sulfuryl fluoride, sulfur dioxide, sulfur trioxide, carbon disulfide or a mixture thereof.

[0010] This is advantageous in further optimizing the components of the electrolyte, forming a stable interfacial passivation film on the negative electrode, preventing the carbonate ester solvent from reacting with the negative electrode active material on the negative electrode, stabilizing the negative electrode potential, and suppressing the self-discharge phenomenon of the negative electrode.

[0011] In any embodiment, the mass fraction W1 of the first additive in the electrolyte of the present application is 0.01% to 5%, optionally 0.1% to 2%, based on the total mass of the electrolyte.

[0012] By defining this range, after the battery is formed, the negative electrode film layer has an appropriate amount of sulfur-containing inorganic components, which is advantageous for the negative electrode interfacial passivation film to be stable, dense and of appropriate thickness, and the self-discharge and cycle performance of the sodium ion secondary battery are further improved.

[0013] In any embodiment, in the electrolyte solution of the present application, the molecular weight of the first additive is 50 g / mol to 200 g / mol.

[0014] By limiting the molecular weight of the low-boiling point sulfur-containing compound, the compound has a strong diffusive ability in the electrolyte and can rapidly diffuse to the negative electrode and react to form a stable interface passivation film.

[0015] In any embodiment, in the electrolyte of the present application, the mass fraction W2 of the second additive in the electrolyte is 0.01% to 5%, and optionally 0.1% to 2%, based on the total weight of the electrolyte.

[0016] By limiting the content of the second additive, it is favorable for the surface of the positive electrode to be covered with an interfacial passivation film after the first charging of the battery, and the interfacial passivation film is sufficient to prevent a small amount of alkyl sodium carbonate present in the electrolyte from undergoing a side reaction on the positive electrode, thereby suppressing the self-discharge phenomenon of the positive electrode, and further improving the self-discharge and cycle performance of the sodium ion secondary battery.

[0017] In any embodiment, in the electrolyte of the present application, the sum of the mass fractions of the first additive and the second additive is 0.5% to 10.5%, optionally 1% to 10%, optionally 1% to 6%, and further optionally 1% to 3%, based on the total mass of the electrolyte, and wherein the ratio of the mass fraction W1 of the first additive in the electrolyte to the mass fraction W2 of the second additive in the electrolyte is 1:(0.01-100), optionally 1:(0.1-10), and further optionally 1:(0.2-5).

[0018] As a result, the electrolyte forms a stable and more conductive positive and negative interfacial passivation film on the surfaces of the positive and negative electrodes, enabling the battery to have not only significantly improved self-discharge rate and cycle performance, but also good power performance.

[0019] In any embodiment, in the electrolyte solution of the present application, the electrolyte sodium salt is NaPF 6 , NaBF 4 , NaN(SO 2 F) 2 , NaClO 4 , NaAsF 6 , NaB(C 2 O 4 ) 2 , NaBF 2 (C 2 O 4 ), NaN(SO 2 R F ) 2 and NaN(SO 2 F)(SO 2 R F), where R F is C b F 2b+1 where b is an integer in the range of 1-10, optionally an integer in the range of 1-3, and further optionally R F -CF 3 , -C 2 F 5 or -CF 2 CF 2 CF 3 It is.

[0020] In any embodiment, in the electrolyte of the present application, the organic solvent comprises a carbonate-based organic solvent, wherein the carbonate-based organic solvent is one or more selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

[0021] In any embodiment, the electrolyte of the present application further comprises a third additive, fluoroethylene carbonate (FEC), whose mass fraction in the electrolyte is 0.01%-10%, preferably 0.1%-5%, to improve the toughness of the positive and negative electrode interface passivation film, and improve the resistance of the interface passivation film to the volume expansion and contraction that occurs during the battery cycle of the positive and negative electrodes, thereby further improving the cycle performance of the battery and maintaining good power performance.

[0022] A second aspect of the present application provides a sodium-ion secondary battery, the sodium-ion secondary battery comprising the electrolyte solution according to the first aspect of the present application.

[0023] A third aspect of the present application provides a battery module, the battery module including the sodium ion secondary battery according to the second aspect of the present application.

[0024] A fourth aspect of the present application provides a battery pack, the battery pack including the battery module according to the third aspect of the present application.

[0025] A fifth aspect of the present application provides a power consumption device, the power consumption device including at least one of a sodium ion secondary battery as described in the second aspect of the present application, a battery module as described in the third aspect of the present application, or a battery pack as described in the fourth aspect of the present application.

[0026] The present application uses a first additive, which is a low boiling point sulfur compound, and a second additive, which is a salt containing oxalate and / or an oxalic acid ester, in an electrolyte to form a stable positive and negative electrode interface passivation film, thereby improving the self-discharge rate and cycle performance of the secondary battery while simultaneously achieving good power performance. Accordingly, the battery pack, battery module, and power consumption device according to the present application have good self-discharge rate, cycle performance, and power performance. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Diagram 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Diagram 3] FIG. 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 4] FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Diagram 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consuming device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, with reference to the drawings, embodiments specifically disclosing the negative plate and its manufacturing method, the positive plate, the secondary battery, the battery module, the battery pack, and the electric device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of the same structure may be omitted. This is to avoid the following description from becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow 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 in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also envisaged. It is noted that if 1 and 2 are listed as the minimum range values, and 3, 4 and 5 are listed as the maximum range values, then 1-3, 1-4, 1-5, 2-3, 2-4 and 2-6 are all envisaged. In this application, unless otherwise specified, a numerical range "a to b" represents a shorthand representation of any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is only a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

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

[0032] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b) to mean that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method may further include step (c) as mentioned above to mean that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0033] Unless otherwise specified, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other ingredients not listed, or may include or include only the listed ingredients.

[0034] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied in the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and A and B are both true (or exist).

[0035] At present, the solvent commonly used for the electrolyte in sodium-ion secondary batteries is carbonate ester, which is used in the negative electrode to 2 The interface passivation film is formed by using alkyl sodium carbonate (Na) and sodium carbonate as the main components. Because alkyl sodium carbonate can be dissolved in carbonate ester solvent and alkyl carbonate ester has strong reducing property, the electrolyte can continue the reduction reaction at the negative electrode and the oxidation reaction at the positive electrode, so that the potential of the negative electrode constantly rises and the potential of the positive electrode constantly falls, and the self-discharge phenomenon of the sodium ion secondary battery is serious.

[0036] Surprisingly, the inventors have found that by adding a low boiling point sulfur-containing additive and an oxalate-containing salt or an oxalate ester additive to the electrolyte together, a stable interfacial passivation film, both of which are mainly composed of inorganic salts, can be rapidly formed at the negative and positive electrodes, thereby improving the self-discharge phenomenon and cycle performance of sodium ion secondary batteries under the premise of maintaining a low interfacial impedance.

[0037] The electrolyte formulation of the present application is particularly applicable to sodium ion secondary batteries having a carbonaceous material as the anode.

[0038] [Electrolyte] A first aspect of the present application provides an electrolyte solution, the electrolyte solution comprising an electrolyte sodium salt, an organic solvent, and an additive, wherein the additive comprises: a) a first additive which is at least one selected from sulfur-containing compounds having a boiling point of 70° C. or less; b) a second additive which is at least one selected from an oxalate-containing salt or an oxalic acid ester; Here, the salt containing oxalate is bis(oxalato)borate (C 4 O 8 B) n (M n+ ), difluoro(oxalato)borate (C 2 O 4 F 2 B) n (Mn+ ), difluorobis(oxalato)phosphate (C 2 O 8 F 2 P) n (M n+ ), tetrafluoro(oxalato)phosphate (C 2 O 4 F 4 P) n (M n+ ), ethyl (oxalato) salt (C 2 O 4 C 2 H 5 ) n (M n+ ), oxalate (C 2 O 4 ) n / 2 (M n+ ), and M n+ is a metal cation and / or an organic cation, optionally an alkali metal, an alkaline earth metal, an aluminum ion or an ammonium ion NH 4 + and optionally a sodium ion, a lithium ion, a potassium ion, a magnesium ion or an aluminum ion, further optionally a sodium ion, a lithium ion, a potassium ion, and n is 1, 2 or 3, and optionally 1 or 2; The oxalic acid ester is at least one selected from the following compounds of formula (I) and formula (II): [ka] Here, R 1 , R 2 are each independently C 1 -C 10 Alkyl group, C 2 -C 10 Alkenyl group, C 1 -C 10 Alkylene phenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 Alkylcarbonyl group, C 2 -C10 Alkylene group, amino group, C 1 -C 10 Alkyleneoxyphenyl group or C 1 -C 10 alkylsulfonyl groups, wherein said C 1 -C 10 Alkyl group, C 2 -C 10 Alkenyl group, C 1 -C 10 Alkylene phenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 Alkylcarbonyl group, C 2 -C 10 Alkylene group, amino group, C 1 -C 10 Alkyleneoxyphenyl group or C 1 -C 10 The alkylsulfonyl group is optionally substituted with one or more substituents selected from halogen atoms, sulfonic acid groups, or nitro groups, and optionally R 1 , R 2 are each independently C 1 -C 4 alkyl groups, The halogen atom is one or more selected from F, Cl and Br; R 3 and R 4 Let's go together 1 -C 20 Alkylene group or C 2 -C 10 Forming an alkenylene group, 1 -C 20 Alkylene group, C 2 -C 10 The alkenylene group may optionally include a halogen atom, a nitro group, an amino group, a carboxyl group, a sulfonic acid group, a C 1 -C 10 Alkylcarbonyl group, C 1 -C 10 Alkyl sulfonyl group, phenyl group, C 1 -C 10 Alkylene phenyl group, C 1 -C10 Alkyleneoxyphenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 alkylene sulfonic acid groups, optionally substituted with one or more substituents selected from R 3 and R 4 Together - (CH 2 ) m -, and m is an integer from 2 to 15.

[0039] Here, the oxalate salt used in this application has the chemical formula (C 2 O 4 ) n / 2 (M n+ For oxalates where n is an odd number, optionally 1 or 3, the molecular formula is (C 2 O 4 ) n (M n+ ) 2 (C 2 O 4 ) n M, where n is an even number, optionally equal to 2, the molecular formula is: (C 2 O 4 )(M n+ ), and (C 2 O 4 )M.

[0040] In this application, the term "C 1 -C 20 An "alkyl group" is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms and which may be linear or branched. 1 -C 20Illustrative examples of alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isoamyl, neopentyl, tert-amyl, 1-methylbutyl, 2-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 5-methylpentyl, 6-methylpentyl, 7-methylpentyl, 8-methylpentyl, 9-methylpentyl, 10-methylpentyl, 11-methylpentyl, 12-methylpentyl, 13-methylpentyl, 14-methylpentyl, 15-methylpentyl, 16-methylpentyl, 17-methylpentyl, 18-methylpentyl, 19-methylpentyl, 20-methylpentyl, 21-methylpentyl, 22-methylpentyl, 23-methylpentyl, 24-methylpentyl, 25-methylpentyl, 26-methylpentyl, 27-methylpentyl, 28-methylpentyl, 29-methylpentyl, 30-methylpentyl, 31-methylpentyl, 32-methylpentyl, 33-methylpentyl, 34-methylpentyl, 35-methylpentyl, 36-methylpentyl, 37-methylpentyl, 38-methylpentyl, 39-methylpentyl, 40-methylpentyl, 41-methylpentyl, 42-methylpentyl, 43-methylpentyl, 44-methylpentyl, 45-methylpentyl, 46-methylpentyl, 47-methylpentyl, 48-methylpentyl, 49-methylpentyl, 49-methylpentyl, 51-methylpentyl, 52-methylpentyl, 45-methylpentyl, These alkyl groups include, but are not limited to, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 1,4-dimethylbutyl, 2,3-dimethylbutyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and undecyl. 1 -C 10 is an alkyl group, and optionally is C 1 -C 6 is an alkyl group, and optionally 1 -C 4 It is an alkyl group. The term "C 1 -C 20 Alkylene group" and "C 1 -C 10 An "alkylene group" is a divalent group. The above definition of the group may be used in combination with other groups, e.g. 1 -C 10 Alkylene phenyl group, C 1 -C 10 Alkylene carboxyl group, C 1 -C 10 Alkylcarbonyl group, C 2 -C 10 Alkyleneamino group, C 1 -C 10 Alkylenesulfonic acid group, C 1 -C 10 This also applies to alkylsulfonyl groups.

[0041] In this application, the term "C 2 -C 20An "alkenyl group" is a straight or branched unsaturated aliphatic group having 2 to 20 carbon atoms and at least one double bond. Examples include, but are not limited to, vinyl, allyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1,3-pentadienyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, and 1,4-hexadienyl. Of these groups, C 2 -C 10 alkenyl group, and optionally C 2 -C 6 alkenyl group, and optionally C 2 -C 4 -alkenyl group. 2 -C 20 Alkenylene group" and "C 2 -C 10 An "alkenylene group" is a divalent group. The above definition of the group also applies to combinations with other groups.

[0042] In this application, the term "C 1 -C 10 Alkyleneoxy group" is "C 1 -C 10 The divalent group of "alkoxy group" is the divalent group of "C 1 -C 10 An "alkoxy group" is a linear or branched saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms and at least one oxygen atom. 1 -C 10 Illustrative examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, t-butoxy, n-pentyloxy, isopentyloxy, neopentyloxy, n-hexyloxy, and isohexyloxy. 1 -C 6 an alkoxy group, and optionally C1 -C 4 It is an alkoxy group. Accordingly, the term "C 1 -C 6 Alkyleneoxy group" and "C 1 -C 4 An "alkyleneoxy group" is a divalent group. The above definition of the group may be used in combination with other groups, e.g., C 1 -C 10 This also applies to alkyleneoxyphenyl groups.

[0043] The use of a low-boiling sulfur-containing compound as a first additive and a salt containing oxalate and / or an oxalic acid ester as a second additive in the electrolyte is advantageous in simultaneously generating a stable interfacial passivation film mainly composed of an inorganic salt on the positive and negative electrodes, thereby suppressing the reaction between the electrolyte and active sodium and stabilizing the potentials of the positive and negative electrodes, thereby significantly improving both the self-discharge and cycle performance of the sodium-ion secondary battery while also achieving good power performance.

[0044] In some embodiments, the second additive in the electrolyte of the present application, the oxalate-containing salt, is selected from lithium bis(oxalato)borate, sodium difluoro(oxalato)borate, lithium oxalate, lithium difluorobis(oxalato)phosphate, sodium tetrafluoro(oxalato)phosphate, or mixtures thereof; the compound of formula (I) is selected from dimethyl oxalate, diethyl oxalate, diphenyl oxalate, dipropenyl oxalate, or mixtures thereof; and the compound of formula (II) is 1,4-dioxane-2,3-dione and / or 1,4-dioxacycloheptadecane-2,3-dione.

[0045] The oxalic acid compound, compared to the organic solvent of the electrolyte, is more likely to undergo oxidative decomposition on the positive electrode and form a stable interface passivation film mainly composed of sodium oxalate. Since sodium oxalate is insoluble in the electrolyte and the interface passivation film is dense, the electrolyte and the positive electrode active material cannot come into direct contact with each other, and a small amount of sodium alkyl carbonate (ROCO 2 Na) cannot undergo oxidative decomposition at the positive electrode, and the positive electrode potential is stabilized, which is advantageous in further reducing the decrease in the positive electrode potential due to the side reaction of sodium alkyl carbonate at the positive electrode.

[0046] In some embodiments, the first additive in the electrolyte of the present application is sulfur hexafluoride (SF 6 ), sulfur tetrafluoride (SF 4 ), sulfuryl fluoride (SO 2 F 2 ), sulfur dioxide (SO 2 ), sulfur trioxide (SO 3 ), carbon disulfide (CS 2 ), dimethyl sulfide (CH 2 SCH 3 ), methyl ethyl sulfide (CH 2 SCH 2 CH 3 ), sulfur monofluoride (S 2 F 2 ), sulfur difluoride (SF 2 ), thionyl fluoride (SOF 2 ) and thionyl tetrafluoroacetate (SOF 4 ) or mixtures thereof, optionally selected from sulfur hexafluoride (SF 6 ), sulfur tetrafluoride (SF 4 ), sulfuryl fluoride (SO 2 F 2 ), sulfur dioxide (SO 2 ), sulfur trioxide (SO 3 ), carbon disulfide (CS 2 ) or a mixture thereof.

[0047] Compared with the solvent carbonate, the low boiling point sulfur-containing compound causes a reduction reaction on the negative electrode, and it becomes easier to form an interface passivation film mainly composed of a sulfur-containing inorganic salt, and since the inorganic salt does not dissolve in the electrolyte, the interface passivation film is stable and the negative electrode potential is stable. In addition, a sulfur-containing compound with a boiling point lower than 70°C has a high diffusion rate in the electrolyte and can quickly form a film on the negative electrode, while at the same time reducing the viscosity of the electrolyte, improving the conductivity of the sodium ion secondary battery, and reducing the internal resistance of the battery.

[0048] In some embodiments, the mass fraction W1 of the first additive in the electrolyte of the present application is 0.01% to 5%, and optionally 0.1% to 2%, based on the total weight of the electrolyte. Thus, the content of the first additive (low boiling point sulfur-containing compound) within the above range is advantageous for forming a stable, dense and moderately thick interfacial passivation film on the negative electrode, and the self-discharge and cycle performance of the sodium ion secondary battery are further improved.

[0049] In the present application, it should be understood that the term "sulfur-containing compounds having a boiling point of 70° C. or less" refers to sulfur-containing compounds having a boiling point of 70° C. or less measured at normal pressure.

[0050] In this application, the boiling point may be measured according to GB / T 616-2006.

[0051] In some embodiments, the sulfur-containing compound is in a gaseous state at ambient pressure and temperature.

[0052] In some embodiments, in the electrolyte of the present application, the molecular weight of the first additive is 50 g / mol to 200 g / mol. A low-boiling point sulfur-containing compound having a molecular weight within this range has a strong diffusion ability and a high diffusion rate in the electrolyte.

[0053] In some embodiments, in the electrolyte of the present application, the mass fraction W2 of the second additive in the electrolyte is 0.01%-5%, optionally 0.1%-2%, based on the total weight of the electrolyte. Thus, by limiting the content of the second additive, the composition of the electrolyte can be further optimized, which is favorable for forming a positive electrode whose surface is covered with a passivation film after the first charge of the battery, thereby avoiding the side reaction of a small amount of alkyl sodium carbonate dissolved in the electrolyte on the positive electrode, stabilizing the positive electrode potential, and thereby further improving the self-discharge and cycle performance of the sodium ion secondary battery. When the content of the second additive in the electrolyte is less than 0.01%, the content is too small, so that the passivation film formed on the electrolyte / positive electrode interface is not enough to prevent the alkyl sodium carbonate in the electrolyte from generating an oxidation reaction on the positive electrode, and the active sodium is incorporated into the positive electrode material, causing a reduction in the positive electrode potential, and the self-discharge of the battery becomes obvious. If the content of the second additive in the electrolyte is too high, that is, greater than 5%, the oxidative decomposition products of the second additive will accumulate on the positive electrode, increasing the membrane resistance at the interface between the positive electrode and the electrolyte, thereby deteriorating the battery performance.

[0054] In some embodiments, in the electrolyte of the present application, the sum of the mass fraction W1 of the first additive in the electrolyte and the mass fraction W2 of the second additive in the electrolyte is 0.5% to 10.5%, optionally 1% to 10%, optionally 1% to 6%, and further optionally 1% to 3%. Here, the ratio of the mass fraction W1 of the first additive in the electrolyte and the mass fraction W2 of the second additive in the electrolyte is 1:(0.01-100), optionally 1:(0.1-10), and further optionally 1:(0.2-5). This further improves the self-discharge rate of the sodium ion secondary battery.

[0055] When W1+W2<0.5%, the negative electrode self-discharge or positive electrode self-discharge is too large, and the battery self-discharge phenomenon is obvious; when W1+W2>10.5%, the interface passivation film between the positive and negative electrodes is too thick, the interface impedance is too large, and the power performance of the battery is poor.

[0056] Optionally, in the electrolyte of the present application, the sum of the first additive W1 and the second additive W2 is 1.1% to 3%, and the ratio of the first additive W1 to the second additive W2 is within the range of 1: (0.5-100), or within the range of 1: (1-10), and also optionally within the range of 1: (0.01-2), and further optionally within the range of 1: (0.1-2), and the sodium ion secondary battery has both low DC internal resistance and self-discharge rate, as shown in Table 1. By further limiting the range, the composition of the electrolyte can be further optimized, and the electrolyte can be promoted to form a stable and more conductive positive and negative electrode interface passivation film on the surface of the positive and negative electrodes, so that the battery can have significantly improved self-discharge rate and cycle performance, as well as good power performance.

[0057] In some embodiments, in the electrolyte solutions of the present application, the electrolyte sodium salt is NaPF 6 , NaBF 4 , NaN(SO 2 F) 2 (abbreviated as NaFSI), NaClO 4 , NaAsF 6 , NaB(C 2 O 4 ) 2 (abbreviated as NaBOB), NaBF 2 (C 2 O 4 ) (abbreviated as NaDFOB), NaN(SO 2 R F ) 2 and NaN(SO 2 F)(SO 2 R F ), where R F is C b F 2b+1 where b is an integer in the range of 1-10, optionally an integer in the range of 1-3, and further optionally R F -CF 3 , -C 2 F 5 or -CF 2 CF2 CF 3 and Optionally, the electrolyte sodium salt is NaPF 6 , NaN(SO 2 F) 2 , NaN(CF 3 SO 2 ) 2 , NaB(C 2 O 4 ) 2 and NaBF 2 (C 2 O 4 ) , Further optionally, the electrolyte sodium salt is NaPF 6 , NaN(SO 2 F) 2 and NaBF 2 (C 2 O 4 ) is one or more selected from.

[0058] In some embodiments, the mass fraction of the electrolyte in the electrolyte solution is 3% to 30%, optionally 5% to 15%.

[0059] In some embodiments, in the electrolyte of the present application, the organic solvent comprises a carbonate-based organic solvent, and optionally, the organic solvent is a carbonate-based organic solvent, which is one or more selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

[0060] In some embodiments, the weight percentage of the organic solvent in the electrolyte is 50% to 97%, optionally 60% to 90%.

[0061] In some embodiments, the organic solvent further comprises one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, 1,3-dioxycyclopentane, tetrahydrofuran, ethylene glycol dimethyl ether, and acetonitrile, and the weight percentage of the organic solvent is 0.5% to 50%, optionally 3% to 30%, optionally 5% to 20%, and further optionally 8% to 15%.

[0062] By further limiting the carbonate organic solvent to the above range, the electrolyte sodium salt can be sufficiently dissociated, the conductivity of the electrolyte can be improved, and the ability to participate in film formation can be reduced to the maximum extent, thereby further improving the self-discharge of the battery.

[0063] In some embodiments, in the electrolyte of the present application, the sum of the mass fractions of the first, second and third additives in the electrolyte is 2% to 12%, optionally 2.1% to 7%.

[0064] In some embodiments, in the electrolyte of the present application, the mass fraction ratio of the first, second and third additives in the electrolyte is 1:(1-10):(0.01-10), optionally 1:(1-10):(0.1-5), and optionally 1:(1-10):(1-2).

[0065] In some embodiments, in the electrolyte of the present application, the sum of the mass fractions of the first, second and third additives in the electrolyte is 2.1% to 4%, and the mass fraction ratio of the first, second and third additives in the electrolyte is 1:(1-10):(0.1-2).Therefore, the sodium ion secondary battery achieves both good DC internal resistance and cycle capacity retention rate.

[0066] In some embodiments, the electrolyte of the present application further contains fluoroethylene carbonate (FEC) as a third additive, and the mass fraction thereof in the electrolyte is 0.01% to 10%, preferably 0.1% to 5%.

[0067] This improves the toughness of the positive and negative electrode interface passivation film, improves the resistance of the interface passivation film to volume expansion and contraction that occurs during battery cycles, and further improves the cycle performance of the battery while maintaining good power performance. This is because, compared with the third additive fluoroethylene carbonate (FEC), the first and second additives of the present application react preferentially on the negative and positive electrodes to form stable positive and negative electrode interface passivation films, and the reaction ability of fluoroethylene carbonate (FEC) at the positive and negative electrodes is small, so that the power performance of the battery is not deteriorated.

[0068] In some specific embodiments, the electrolyte comprises: a) a first additive having a mass fraction of 0.01% to 5%, optionally 0.1% to 2%; b) a second additive having a mass fraction of 0.01% to 5%, optionally 0.1% to 2%; c) an electrolyte sodium salt having a mass fraction of 3% to 30%, optionally 5% to 15%; d) a carbonate-based organic solvent having a mass fraction of 50% to 97%, optionally 60% to 90%, wherein the sum of the mass fractions of components a) and b) is 0.5% to 10.5%, optionally 1% to 10%, optionally 1% to 6%, and further optionally 1% to 3%, and the ratio of the mass fractions of components a) and b) is 1:(0.01-100), optionally 1:(0.1-10), and further optionally 1:(0.2-5); or The sum of the mass fractions of components a) and b) is 1.1% to 3%, and the mass fraction ratio of components a) and b) is 1:(0.5-100), optionally 1:(1-10), and optionally 1:(0.01-2).

[0069] In some specific embodiments, the electrolyte comprises: a) a first additive having a mass fraction of 0.01% to 5%, optionally 0.1% to 2%; b) a second additive having a mass fraction of 0.01% to 5%, optionally 0.1% to 2%; c) an electrolyte sodium salt having a mass fraction of 3% to 30%, optionally 5% to 15%; d) a carbonate-based organic solvent having a mass fraction of 50% to 97%, optionally 60% to 90%; e) a third additive having a mass fraction of 0.01% to 10%, preferably 0.1% to 5%, wherein the sum of the mass fractions of components a), b), and e) is between 2% and 12%, optionally between 2.1% and 7%, and the ratio of the mass fractions of components a), b), and e) is between 1:(1-10):(0.01-10), optionally between 1:(1-10):(0.1-5), and optionally between 1:(1-10):(1-2); or The sum of the mass fractions of components a), b), and e) is 2.1% to 4%, and the mass fraction ratio of components a), b), and e) is 1:(1-10):(0.1-2).

[0070] It should be understood that the electrolyte of the present application can not only be used in sodium ion secondary batteries, but also can be used in any other battery module, battery pack or power consuming device that needs to improve the self-discharge rate, cycle performance of the battery.

[0071] A second aspect of the present application provides a sodium ion secondary battery, the sodium ion secondary battery comprising a positive electrode plate, a separator, a negative electrode plate and the electrolyte solution according to the first aspect of the present application.

[0072] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During charging and discharging of the battery, active ions shuttle between the positive electrode plate and the negative electrode plate, absorbing and releasing them. The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, and mainly serves to prevent short-circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0073] [Positive plate] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0074] For example, the positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0075] In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, an aluminum foil may be employed as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0076] In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery well-known in the art. By way of example, the positive electrode active material may include at least one of a sodium transition metal oxide, a polyanion-type compound, and a Prussian blue-based compound. The present application is not limited to these materials, and other conventionally well-known materials that can be used as the positive electrode active material of a sodium ion battery may also be used. Based on the total weight of the positive electrode film layer, the weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100% by weight.

[0077] In some embodiments, among the sodium transition metal oxides, the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na x M y O 2 where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≦ 1, 0.5 < y ≦ 1.5. In some embodiments, the positive electrode active material may employ Na 0.88 Cu 0.24 Fe 0.29 Mn 0.47 O 2 。

[0078] In some embodiments, the polyanion-type compound may be a kind of compound having sodium ions, transition metal ions, and tetrahedral (YO 4 ) n- anion units. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n represents the valence of (YO 4 ) n- .

[0079] In some embodiments, the polyanion-type compound further includes sodium ions, transition metal ions, tetrahedral (YO 4 ) n- ​The anion unit may be a type of compound having a halogen anion. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n may be any of the following: (YO 4 ) n- and the halogen may be at least one of F, Cl, and Br.

[0080] In some embodiments, the polyanionic compound further comprises sodium ions, tetrahedral (YO 4 ) n- Anionic unit, polyhedral unit (ZO y ) m+ and an optional halogen anion. Y may be at least one of P, S, and Si, and n is (YO 4 ) n- Z represents a transition metal and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents a valence of (ZO y ) m+ and the halogen may be at least one of F, Cl, and Br.

[0081] In some embodiments, the polyanionic compound is, for example, NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , NaM'PO 4 F (M' is one or more of V, Fe, Mn and Ni) and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y At least one of (0≦y≦1).

[0082] In some embodiments, the Prussian blue compound may be a type of compound having a sodium ion, a transition metal ion, and a cyanide ion (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, Na a Me b Me' c (CN) 6 where Me and Me′ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn; <a≦2、0<b<1、0<c<1である。

[0083] In some embodiments, the positive electrode membrane layer optionally further includes an adhesive. For example, the adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin. Based on the total weight of the positive electrode membrane layer, the weight ratio of the adhesive in the positive electrode membrane layer is 0 to 20% by weight.

[0084] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent. For example, the conductive agent may comprise at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the positive electrode membrane layer, the weight ratio of the conductive agent in the positive electrode membrane layer is 0 to 20% by weight.

[0085] In some embodiments, the positive plate may be manufactured by the following method: The above-mentioned components for manufacturing the positive plate, such as the positive active material, the conductive agent, the adhesive and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive slurry, and the positive slurry is dried to a concentration of 0.20-0.35 g (dry weight) / 1540.25 mm 2The positive electrode current collector is uniformly coated with the above amount of paint, and then the positive electrode plate is obtained through processes such as drying and cold pressing.

[0086] [Negative plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0087] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0088] In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, a copper foil may be employed as the metal foil sheet. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0089] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries well known in the art. For example, the negative electrode active material may include at least one of hard carbon, artificial graphite, natural graphite, soft carbon, silicon-based material, tin-based material, and lithium titanate. The silicone-based material may be selected from at least one of silicone alone, silicon oxide, silicone carbon composite, silicone nitrogen composite, and silicone alloy. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery may be used. These negative electrode active materials may be used alone or in combination of two or more. Based on the total weight of the negative electrode film layer, the weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100% by weight.

[0090] In some embodiments, the negative electrode membrane layer optionally further comprises an adhesive. The adhesive 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). Based on the total weight of the negative electrode membrane layer, the weight ratio of the adhesive in the negative electrode membrane layer is 0 to 30% by weight.

[0091] In some embodiments, the negative electrode film layer optionally further comprises 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. Based on the total weight of the negative electrode film layer, the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20% by weight.

[0092] In some embodiments, the negative electrode membrane layer optionally further includes other auxiliary agents, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)). Based on the total weight of the negative electrode membrane layer, the weight ratio of the other auxiliary agents in the negative electrode membrane layer is 0 to 15% by weight.

[0093] In some embodiments, the negative plate may be manufactured by the following method: The above-mentioned components for manufacturing the negative plate, such as the negative active material, the conductive agent, the adhesive and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative slurry, and the negative slurry is adjusted to 0.10-0.20 g (dry weight) / 1540.25 mm 2 The negative electrode current collector is uniformly coated with the above amount of the paste, and after drying, cold pressing, and other processes, the negative electrode plate is obtained.

[0094] [Separator] In some embodiments, the secondary battery further includes a separator. The separator is disposed between the positive and negative plates to provide an insulating effect. The present application does not particularly limit the type of separator, and any well-known separator with a porous structure having good chemical and mechanical stability may be selected.

[0095] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multi-layer composite thin film, and there is no particular limitation. When the separator is a multi-layer composite thin film, the materials of each layer may be the same or different, and there is no particular limitation.

[0096] [Exterior body] In some embodiments, the secondary battery may include an exterior body for packaging the positive electrode plate, the negative electrode plate, and the electrolyte. As an example, the positive electrode plate, the negative electrode plate, and the separator may be stacked or wound to form a stacked structure battery cell or a wound structure battery cell, and the battery cell is packaged in the exterior body, and the electrolyte adopts the electrolyte solution described in the first aspect of the present application, and the electrolyte solution is infiltrated into the battery core. The number of battery cells in the secondary battery may be one or several, and may be adjusted according to demand.

[0097] In one embodiment, the present application provides an electrode assembly. In some embodiments, the positive electrode plate, the negative electrode plate, and the separator may be wound or laminated to produce the electrode assembly. An exterior body may be used to package the electrode assembly and the electrolyte.

[0098] In some embodiments, the exterior body of the secondary battery may be a soft package, for example, a bag-type soft package. The material of the soft package may be plastic, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc. In some embodiments, the exterior body of the secondary battery may be a hard case, for example, a hard plastic case, an aluminum case, a steel case, etc.

[0099] The present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows a secondary battery 5 with a rectangular structure as an example.

[0100] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected on the bottom plate, and the bottom plate and the side plate surround the case 51 to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to actual specific needs.

[0101] Power consumption device, battery module or battery pack In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by one skilled in the art based on the application and capacity of the battery module.

[0102] Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, the secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by fasteners.

[0103] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0104] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by one skilled in the art based on the application and capacity of the battery pack.

[0105] 4 and 5 show an example of a battery pack 1. Referring to FIG. 4 and FIG. 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3 to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any manner.

[0106] The present application further provides a power consuming device, the power consuming device including at least one of the secondary battery, the battery module, or the battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0107] The power consumption device can be selected as a secondary battery, a battery module, or a battery pack depending on the demands of the usage.

[0108] 6 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the power consuming device's demand for high power and high energy density of secondary batteries.

[0109] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are generally required to be lightweight and may employ a secondary battery as a power source.

[0110] Working Example The following describes the examples of the present application. The examples described below are illustrative and are merely for interpreting the present application, and should not be understood as limitations on the present application. If no specific techniques or conditions are specified in the examples, they are performed according to the techniques or conditions described in the literature in the art or in the product instructions. Reagents, compounds, or equipment used that do not specify the manufacturer are all general products that can be purchased commercially. The content of each component in the examples of the present application is based on mass, excluding water of crystallization, unless otherwise specified.

[0111] The following descriptive terms: "electrolyte of Example 1-1" refers to the electrolyte used in the manufacturing process of the sodium ion secondary battery of Example 1-1, "positive electrode plate of Example 1-1" refers to the positive electrode plate used in the manufacturing process of the sodium ion secondary battery of Example 1-1, "negative electrode plate of Example 1-1" refers to the negative electrode plate used in the manufacturing process of the sodium ion secondary battery of Example 1-1, "separator of Example 1-1" refers to the separator used in the manufacturing process of the sodium ion secondary battery of Example 1-1, and "sodium ion secondary battery of Example 1-1" refers to a sodium ion secondary battery manufactured from the positive electrode, separator, negative electrode, and electrolyte of Example 1-1.

[0112] Na used in the examples of this application 0.88 Cu 0.24 Fe 0.29 Mn 0.47 O 2 It was manufactured with reference to patent CN201910026508.1.

[0113] Example 1: Preparation of electrolyte

[0114] Water content (H 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 625.9g of ethylene carbonate (EC) and 60.3g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquor. 98.99g of the mother liquor, 0.01g of sulfur dioxide and 1g of sodium difluoro(oxalato)borate were then taken and thoroughly stirred and dissolved to obtain an electrolyte for this example.

[0115] The active material is Na 0.88 Cu 0.24 Fe 0.29 Mn 0.47 O 2 The conductive agent, acetylene black, and the adhesive, polyvinylidene fluoride (PVDF), were mixed in a weight ratio of 90:5:5 in an N-methylpyrrolidone solvent system by thorough stirring to obtain a positive electrode slurry. The positive electrode slurry was then weighed to obtain 0.28 g (dry weight) / 1540.25 mm. 2 The aluminum foil was dried at room temperature, then transferred to a drying box at 120°C for 1 hour, and cold pressed and slit to obtain a positive electrode plate.

[0116] The active material, hard carbon, conductive agent, acetylene black, adhesive, sodium carboxymethyl cellulose (CMC), thickener, were mixed in a weight ratio of 90:4:4:2 in a deionized water solvent system with sufficient stirring to obtain anode slurry. The anode slurry was measured at 0.14 g (dry weight) / 1540.25 mm. 2 The copper foil of the negative electrode current collector was uniformly coated with the amount of 13 μm, and the copper foil was dried at room temperature, then transferred to a drying box at 120 ° C and dried for 1 hour, and then cold pressed and slit to obtain a negative electrode plate.

[0117] The separator is a polyethylene (PE) porous polymer film with a thickness of 9 μm.

[0118] The positive electrode plate, separator, and negative electrode plate are stacked in this order, so that the separator acts as an insulating layer between the positive and negative electrodes. The resultant is then wound up to obtain a bare cell. The bare cell with a capacity of 3 Ah is placed on an aluminum plastic film exterior, and 10 g of the electrolyte solution prepared above is injected into the dried battery. After vacuum packaging, standing, chemical conversion, shaping, and other processes, a sodium ion secondary battery is obtained.

[0119] Example 2-17 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with an argon concentration of <0.1 ppm, 13.8 g of NaPF6, 25.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added to a beaker and thoroughly stirred and dissolved to obtain a mother liquid. Then, based on the total mass of the electrolyte (100 g) and the mass fractions of the first additive and the second additive shown in Table 1, a certain mass of the first additive and the second additive were weighed, and the weighed mass of the mother liquid was the difference between the total mass of the electrolyte (100 g) and the total mass of the first and second additives. After thoroughly stirring and dissolving the first additive, the second additive and the mother liquid, an electrolyte for each example and comparative example was obtained, and the total mass of the electrolyte was 100 g.

[0120] Examples 18-23 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6Then, 25.9g of ethylene carbonate (EC) and 60.3g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquid. Then, based on the total mass of the electrolyte solution of 100g and the mass fractions of the first additive, the second additive and the third additive shown in Table 1, a certain mass of the first additive, the second additive and the third additive were weighed, and the weighed mass of the mother liquid was the difference between the total mass of the electrolyte solution of 100g and the total mass of the first, second and third additives. After thoroughly stirring and dissolving the first additive, the second additive, the third additive and the mother liquid, an electrolyte solution for each example was obtained, and the total mass of the electrolyte solution was 100g.

[0121] Comparative Example 1 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 25.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added and thoroughly stirred to dissolve, and then an electrolyte solution for this comparative example was obtained. The total mass of the electrolyte solution was 100 g.

[0122] Comparative Example 2 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 Then, 25.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquid. Then, 99.99 g of the mother liquid and 0.01 g of 1,3-propane sultone (PS) were taken and thoroughly stirred and dissolved to obtain an electrolyte solution for Comparative Example 2, and the total mass of the electrolyte solution was 100 g.

[0123] Comparative Example 3 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 25.9g of ethylene carbonate (EC) and 60.3g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquid. 99.99g of the mother liquid and 0.01g of vinyl sulfate (DTD) were then taken and thoroughly stirred and dissolved to obtain an electrolyte for Comparative Example 3. The total mass of the electrolyte was 100g.

[0124] Comparative Example 4 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 25.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added and thoroughly stirred to dissolve, obtaining a mother liquor. 99.99 g of the mother liquor and sulfur dioxide (SO 2 0.01 g of the electrolyte was taken and thoroughly stirred and dissolved to obtain an electrolyte solution for Comparative Example 4. The total mass of the electrolyte solution was 100 g.

[0125] Comparative Example 5 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 625.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquid. 99.99 g of the mother liquid and 0.01 g of lithium bis(oxalato)borate were then taken and thoroughly stirred and dissolved to obtain an electrolyte solution for Comparative Example 5, the total mass of which was 100 g.

[0126] Comparative Example 6 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 Then, 25.9 g of ethylene carbonate (EC) and 60.3 g of ethyl methyl carbonate (EMC) were added and thoroughly stirred and dissolved to obtain a mother liquid. Then, 99.99 g of the mother liquid and 0.01 g of sodium difluoro(oxalato)borate were taken and thoroughly stirred and dissolved to obtain an electrolyte solution for Comparative Example 6, and the total mass of the electrolyte solution was 100 g.

[0127] Comparative Example 7 The manufacturing process of the sodium ion secondary battery generally refers to Example 1, but the difference is that the manufacturing steps of the electrolyte are as follows: 2 O) < 10 ppm, oxygen content (O 2 In an argon atmosphere glove box with a concentration of <0.1 ppm, 13.8 g of NaPF was added to each beaker. 6 Then, 25.9g of ethylene carbonate (EC) and 60.3g of ethyl methyl carbonate (EMC) were added and thoroughly stirred to dissolve, to obtain a mother liquid. Then, 99.99g of the mother liquid and 0.01g of fluoroethylene carbonate (FEC) were taken and thoroughly stirred to dissolve, to obtain an electrolyte for Comparative Example 7, the total mass of which was 100g. Related parameters and battery performance test

[0128] 1. Self-discharge test of sodium-ion secondary batteries At 25°C, the sodium ion secondary batteries obtained in the examples and comparative examples were left for 5 minutes, charged at a constant current of 1C to 4.2V, and then charged at a constant voltage until the current was 0.05C or less. They were then left for 5 minutes, and then discharged at a constant current of 0.1C to 3.7V. After leaving the batteries for 24 hours, the voltage V1 was tested, and after leaving the batteries for 48 hours, the voltage V2 was tested. The self-discharge rate K of the battery core is (V1-V2) / 48.

[0129] The sodium ion secondary batteries of Examples 1-17 and Comparative Examples 1-6 were tested according to the above procedure. See Table 1 for specific values.

[0130] 2. Room temperature cycle performance test of sodium ion secondary batteries At 25°C, the sodium ion secondary batteries produced in the examples and comparative examples were left for 5 minutes, charged at a constant current of 1C to 4.2V, then charged at a constant voltage until the current was 0.05C or less, left for 5 minutes, and discharged at a constant current of 1C to 2.0V, which constitutes one charge-discharge cycle, and the discharge capacity of this cycle was the discharge capacity of the first cycle of the sodium ion secondary battery. The sodium ion secondary batteries were subjected to 800 cycles of charge-discharge testing using the above method, and the discharge capacity of each cycle was recorded.

[0131] Capacity retention rate (%) of a sodium ion secondary battery after 800 cycles at 25°C and 1C / 1C = discharge capacity at 800th cycle / discharge capacity at 1st cycle x 100%.

[0132] According to the above procedure, the sodium ion secondary batteries of Examples 3, 18-23 and Comparative Example 7 were tested, and the specific values ​​are shown in Table 1.

[0133] 3. Direct current internal resistance (DCR) test for sodium ion secondary batteries At 25°C, the sodium ion secondary battery was left for 5 minutes, charged at a constant current of 1C up to 4.2V, and then charged at a constant voltage until the current fell to 0.05C or less, at which point the battery's state of charge (SOC) was 100%. It was then left for 5 minutes, and further discharged at a constant current of 1C, adjusting the state of charge (SOC) of the sodium ion secondary battery to 50%.

[0134] A sodium ion secondary battery at 50% SOC was left for 10 minutes and then discharged at a constant current of 4 C for 30 seconds. The voltage U1 in the last second after leaving the battery, the voltage U2 in the last second after constant current discharge at 4 C, and the current I after constant current discharge at 4 C were recorded.

[0135] The DC internal resistance of a sodium ion secondary battery discharged at a constant current of 4C for 30 seconds at 25°C and 50% SOC is (U2-U1) / I.

[0136] The sodium ion secondary batteries of the examples and comparative examples were tested according to the above process. See Tables 1 and 2 for specific values.

[0137] In Tables 1 and 2, the mass fraction of the first additive in the electrolyte is W1, and the mass fraction of the second additive in the electrolyte is W2, based on the total weight of the electrolyte. Here, the symbol " / " in the tables indicates that the substance is not present in the electrolyte and that the mass fraction is 0.

[0138] [Table 1] JPEG2025515804000005.jpg190170

[0139] As can be seen from Table 1, compared with Comparative Examples 1-6, here, Comparative Examples 2 and 3 used common sulfur-containing compounds 1,3-propane sultone (PS) and vinyl sulfate (DTD), and Comparative Examples 4-6 used a single additive (a low-boiling point sulfur-containing compound (sulfur dioxide), an oxalate-containing salt, and an oxalic acid ester), the sodium ion secondary batteries corresponding to the examples of the present application contained electrolytes of a first additive with a mass fraction of 0.01% to 5% and a second additive with a mass fraction of 0.01% to 5%, all of which had good DC internal resistance and obviously improved self-discharge rates.

[0140] As can be seen by comparing Examples 1-17 of the present invention, the sum of the first additive W1 and the second additive W2 is 1.1%-3%, and the ratio of the first additive W1 to the second additive W2 is within the range of 1:(0.5-100), or within the range of 1:(1-10), and optionally within the range of 1:(0.01-2), and further optionally within the range of 1:(0.1-2), the sodium ion secondary battery has both low DC internal resistance and low self-discharge rate. However, when the content of the first additive or the second additive is small (as shown in Examples 1 and 6), the self-discharge rate is large. When the content of the first additive or the second additive is large (as shown in Example 11), the film formed at the interface between the positive electrode and the negative electrode is too thick, so the DC internal resistance is large.

[0141] [Table 2]

[0142] As can be seen from Table 2, compared with Comparative Example 7 (electrolyte not containing the third additive, fluoroethylene carbonate), when the electrolyte contains the first and second additives, the cycle capacity retention rate of the sodium ion secondary battery is improved (Example 3), and when the electrolyte contains the first, second and third additives (fluoroethylene carbonate), the cycle performance of the sodium ion secondary battery is significantly improved (e.g., Examples 18 to 23), and the cycle capacity retention rate can reach 93%.

[0143] It should be noted that the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is an example, and any embodiment having substantially the same configuration as the technical idea and achieving the same effect within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiment and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application, within the scope of the purpose of the present application. [Explanation of symbols]

[0144] 1, battery pack, 2, upper housing, 3, lower housing, 4, battery module, 5, secondary battery, 51, case, 52, electrode assembly, 53, cover plate.

Claims

1. An electrolytic solution comprising an electrolyte sodium salt, an organic solvent, and an additive, wherein the additive comprises a) a first additive which is at least one selected from sulfur-containing compounds having a boiling point of 70° C. or less; b) a second additive which is at least one selected from an oxalate-containing salt or an oxalic acid ester; Here, the salt containing oxalate is bis(oxalato)borate (C ４ O ８ B) ｎ (M ｎ＋ ), difluoro(oxalato)borate (C ２ O ４ F ２ B) ｎ (M ｎ＋ ), difluorobis(oxalato)phosphate (C ２ O ８ F ２ P) ｎ (M ｎ＋ ), tetrafluoro(oxalato)phosphate (C ２ O ４ F ４ P) ｎ (M ｎ＋ ), ethyl (oxalato) salt (C ２ O ４ C ２ H ５ ) ｎ (M ｎ＋ ), oxalate (C ２ O ４ ) ｎ／２ (M ｎ＋ ), and M ｎ＋ is a metal cation and / or an organic cation, optionally an alkali metal ion, an alkaline earth metal ion, an aluminum ion or an ammonium ion NH ４ ＋ and optionally a sodium ion, a lithium ion, a potassium ion, a magnesium ion or an aluminum ion, further optionally a sodium ion, a lithium ion, a potassium ion; n is 1, 2 or 3, and optionally 1 or 2; The oxalic acid ester is at least one selected from the following compounds of formula (I) and formula (II): 【Chemistry 1】 Here, R １ , R ２ are each independently C １ -C １０ Alkyl group, C ２ -C １０ Alkenyl group, C １ -C １０ Alkylene phenyl group, C １ -C １０ Alkylene carboxyl group, C １ -C １０ Alkylcarbonyl group, C ２ -C １０ Alkyleneamino group, C １ -C １０ Alkyleneoxyphenyl group or C １ -C １０ alkylsulfonyl groups, wherein said C １ -C １０ Alkyl group, C ２ -C １０ Alkenyl group, C １ -C １０ Alkylene phenyl group, C １ -C １０ Alkylene carboxyl group, C １ -C １０ Alkylcarbonyl group, C ２ -C １０ Alkyleneamino group, C １ -C １０ Alkyleneoxyphenyl group or C １ -C １０ The alkylsulfonyl group is optionally substituted with one or more substituents selected from halogen atoms, sulfonic acid groups, or nitro groups, and optionally R １ , R ２ are each independently C １ -C ４ alkyl groups, The halogen atom is one or more selected from F, Cl and Br; R ３ and R ４ Let's go together １ -C ２０ Alkylene group or C ２ -C １０ Forming an alkenylene group, １ -C ２０ Alkylene group, C ２ -C １０ The alkenylene group may optionally include a halogen atom, a nitro group, an amino group, a carboxyl group, a sulfonic acid group, a C １ -C １０ Alkylcarbonyl group, C １ -C １０ Alkyl sulfonyl group, phenyl group, C １ -C １０ Alkylene phenyl group, C １ -C １０ Alkyleneoxyphenyl group, C １ -C １０ Alkylene carboxyl group, C １ -C １０ alkylene sulfonic acid groups, optionally substituted with one or more substituents selected from R ３ and R ４ Let's go together - (CH ２ ) ｍ -, and m is an integer of 2 to 15.

2. The oxalate-containing salt in the second additive is selected from lithium bis(oxalato)borate, sodium difluoro(oxalato)borate, lithium oxalate, lithium difluorobis(oxalato)phosphate, sodium tetrafluoro(oxalato)phosphate, or a mixture thereof; The compound of formula (I) is selected from dimethyl oxalate, diethyl oxalate, diphenyl oxalate, dipropenyl oxalate or mixtures thereof; 2. The electrolyte according to claim 1, wherein the compound of formula (II) is 1,4-dioxane-2,3-dione and / or 1,4-dioxacycloheptadecane-2,3-dione.

3. 3. The electrolyte according to claim 1 or 2, characterized in that the first additive is selected from sulfur hexafluoride, sulfur tetrafluoride, sulfuryl fluoride, sulfur dioxide, sulfur trioxide, carbon disulfide, dimethyl sulfide, methyl ethyl sulfide, sulfur monofluoride, sulfur difluoride, thionyl fluoride and tetrafluorothionyl or mixtures thereof, and optionally selected from sulfur hexafluoride, sulfur tetrafluoride, sulfuryl fluoride, sulfur dioxide, sulfur trioxide, carbon disulfide or mixtures thereof.

4. The mass fraction W1 of the first additive in the electrolyte solution is 0.01% to 5%, and optionally 0.1% to 2%, based on the total mass of the electrolyte solution. The electrolyte solution according to any one of claims 1 to 3.

5. 5. The electrolyte solution according to claim 1, wherein the first additive has a molecular weight of 50 g / mol to 200 g / mol.

6. The mass fraction W2 of the second additive in the electrolyte solution is 0.01% to 5%, and optionally 0.1% to 2%, based on the total mass of the electrolyte solution. The electrolyte solution according to any one of claims 1 to 5.

7. 7. The electrolyte solution according to claim 1, wherein the sum of the mass fractions of the first additive and the second additive is between 0.5% and 10.5%, optionally between 1% and 10%, optionally between 1% and 6%, and further optionally between 1% and 3%, based on the total mass of the electrolyte solution.

8. The electrolyte of claim 7, wherein the ratio of the mass fraction W1 of the first additive in the electrolyte to the mass fraction W2 of the second additive in the electrolyte is 1:(0.01-100), optionally 1:(0.1-10), and optionally 1:(0.2-5).

9. The electrolyte sodium salt is NaPF ６ , NaBF ４ , NaN(SO ２ F) ２ , NaClO ４ , NaAsF ６ , NaB(C ２ O ４ ) ２ , NaBF ２ (C ２ O ４ ), NaN(SO ２ R Ｆ ) ２ and NaN(SO ２ F) (SO ２ R Ｆ ) wherein R Ｆ is C ｂ F ２ｂ＋１ where b is an integer in the range of 1-10, optionally an integer in the range of 1-3, and further optionally R Ｆ is -CF ３ , -C ２ F ５ Or -CF ２ CF ２ CF ３ The electrolyte solution according to any one of claims 1 to 8,

10. 10. The electrolyte solution according to claim 1, wherein the organic solvent comprises a carbonate-based organic solvent, and the carbonate-based organic solvent is one or more selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

11. The electrolyte solution according to any one of claims 1 to 10, further comprising a third additive, fluoroethylene carbonate (FEC), the mass fraction of which in the electrolyte solution is 0.01% to 10%, preferably 0.1% to 5%.

12. A sodium ion secondary battery comprising a positive electrode plate, a separator, a negative electrode plate, and the electrolyte solution according to any one of claims 1 to 11.

13. A battery module comprising the sodium ion secondary battery according to claim 12.

14. A battery pack comprising the battery module according to claim 13.

15. A power consuming device comprising at least one selected from the sodium ion secondary battery according to claim 12, the battery module according to claim 13, or the battery pack according to claim 14.

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