Electrolyte for sodium ion batteries, sodium ion battery cells and secondary batteries

Abstract

The present application provides an electrolyte for a sodium-ion battery, a sodium-ion battery cell, a secondary battery, and a power consumption device, which belong to the battery technical field. The electrolyte includes a first additive, and the first additive includes a compound represented by general formula (I), where R1, R2, R3, and R4 each independently include at least one of a single bond and an alkylene group having 1 to 4 carbon atoms; R5 includes (II) or (III); R6 includes at least one of (IV), (V), and (VI); and R7 includes at least one of a single bond, an alkylene group having 1 to 3 carbon atoms, and an alkyleneoxy group having 1 to 3 carbon atoms. The technical solutions of the present application can improve the performance of sodium-ion batteries. JPEG2026501873000043.jpg37170

Description

[Technical Field]

[0001] The present application relates to the field of battery technology, and in particular to electrolytes for sodium ion batteries, sodium ion battery cells, secondary batteries, and power consuming devices. [Background technology]

[0002] With the worsening of environmental pollution, the new energy industry is attracting more and more attention, and battery technology is a key element in the development of the new energy industry.

[0003] Due to the abundant reserves and low cost of sodium salt raw materials, the use of sodium ion batteries has gradually attracted attention. As an important component of sodium ion batteries, electrolyte is very important to the performance of sodium ion batteries. Therefore, how to provide electrolyte for sodium ion batteries to improve the performance of sodium ion batteries is a technical problem that needs to be solved as soon as possible. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide an electrolyte for a sodium ion battery that improves the performance of the sodium ion battery.

[0005] To achieve the above object, the present application provides an electrolyte for a sodium ion battery, a sodium ion battery cell, a secondary battery, and a power consuming device.

[0006] A first aspect provides an electrolyte for a sodium ion battery, the electrolyte comprising a first additive, the first additive comprising a compound represented by general formula (I): [ka] Here, R1, R2, R3, and R4 each independently contain at least one of a single bond and an alkylene group having 1 to 4 carbon atoms, and R5 is [ka] or [ka] and R6 is [ka] and R7 includes at least one of a single bond, an alkylene group having 1 to 3 carbon atoms, and an alkyleneoxy group having 1 to 3 carbon atoms.

[0007] The present application provides an electrolyte for a sodium-ion battery. The electrolyte includes a first additive, which includes a compound represented by general formula (I). The compound having the structure of general formula (I) can form a sulfite-rich interfacial passivation film on the surface of the positive electrode of a battery cell, preferentially over the electrolyte solvent. This interfacial passivation film can inhibit direct contact between the electrolyte and the positive electrode surface, thereby reducing the likelihood of electrolyte oxidation. Furthermore, sulfite is easily oxidized, and sulfite is oxidized preferentially over the electrolyte or the electrolyte solvent, thereby reducing the likelihood of electrolyte oxidation. The long carbon chain length of compound (I) can reduce the risk of generating gaseous by-products (e.g., ethylene) after oxidative decomposition of compound (I), thereby reducing the amount of gas generation in sodium-ion batteries. Adding a compound represented by general formula (I) to the electrolyte is advantageous for improving the lifespan of sodium-ion batteries and mitigating gas generation. Therefore, the technical solutions of the present application are advantageous for improving the performance of sodium-ion batteries.

[0008] In one possible implementation, based on the total mass of the electrolyte, the content W1 of the first additive in the electrolyte is 0.01% to 5%, optionally 0.05% to 5%, and further optionally 0.1% to 2%.

[0009] If the content of the first additive is less than 0.01%, the interfacial passivation film formed on the surface of the positive electrode has a relatively small effect of preventing oxidation of the electrolyte, and the effect of improving the performance of the sodium-ion battery cell is weak. If the content of the first additive is more than 5%, a large amount of reaction products due to oxidative decomposition will accumulate near the positive electrode of the sodium-ion battery cell, which may increase the internal resistance of the sodium-ion battery cell, which is disadvantageous to improving the performance of the sodium-ion battery cell. Setting the content W1 of the first additive in the electrolyte to 0.01% to 5% is advantageous in further improving the performance of the sodium-ion battery cell.

[0010] Setting the content W1 of the first additive in the electrolyte to 0.05% to 5% is advantageous in further improving the performance of the sodium ion battery cell, and it is possible to achieve both a long service life and an internal resistance of the sodium ion battery cell. Setting the content W1 of the first additive in the electrolyte to 0.1% to 2% is advantageous in further improving the performance of the sodium ion battery cell, and it is possible to achieve both a long service life and an internal resistance of the sodium ion battery cell.

[0011] In one possible embodiment, the compound (I) is the following compound: [ka] [ka] It includes at least one of the following.

[0012] In the above technical solution, selecting any one of compounds 1 to 22 as compound (I) is advantageous to further improve the performance of the sodium ion battery cell.

[0013] In one possible embodiment, the compound (I) includes at least one of compounds 9 to 22, and optionally, the compound (I) includes at least one of compounds 11, 12, and 13.

[0014] In the electrolyte, the consumption rate of compounds 9 to 22 is slower than that of compounds 1 to 8, which is advantageous for compounds 9 to 22 to participate in reactions and thereby further improve the performance of sodium-ion battery cells. Compounds 11, 12, and 13 have relatively high solubility in the electrolyte solvent, which is advantageous for compounds 11, 12, and 13 to participate in reactions and thereby further improve the performance of sodium-ion battery cells.

[0015] In one possible implementation, the electrolyte solution further includes a second additive, and the second additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, propylene sultone, vinyl sulfate, maleic anhydride, bisfluoro(oxalato)borate, succinic anhydride, and triallyl phosphate.

[0016] In the above solution, the second additive can form an interfacial passivation film on the surface of the negative electrode in preference to the solvent, inhibit the formation of easily soluble substances such as sodium alkyl carbonate, and reduce side reactions occurring between the solvent in the electrolyte and the negative electrode, which is advantageous for further extending the life of the sodium ion battery cell.

[0017] In one possible implementation, based on the total mass of the electrolyte, the content W2 of the second additive in the electrolyte is 0.01% to 10%, preferably 0.1% to 5%.

[0018] If the content of the second additive is less than 0.01%, the interfacial passivation film formed by the reaction of the second additive on the negative electrode surface is small, and the effect of improving the performance of the sodium-ion battery cell is weak. If the content of the second additive is greater than 10%, the interfacial passivation film formed on the negative electrode of the sodium-ion battery cell is thick, increasing the internal resistance of the sodium-ion battery cell and detracting from the improvement of the performance of the sodium-ion battery cell. Setting the content W2 of the second additive in the electrolyte to 0.01% to 10% is advantageous for further improving the performance of the sodium-ion battery cell. Setting the content W2 of the second additive in the electrolyte to 0.1% to 5% can further improve the performance of the sodium-ion battery cell.

[0019] In one possible embodiment, the content W1 of the first additive in the electrolyte and the content W2 of the second additive in the electrolyte are 0.05×10 -4 ≦W1×W2≦10×10 -4 By setting W1 and W2 so that the above relationship is satisfied, it is possible to increase the life of the sodium ion battery while maintaining a relatively low internal resistance of the battery.

[0020] In one possible implementation, the electrolyte solution further includes an electrolyte salt, which includes at least one of NaPF6, NaBF4, NaN(SO2F)2, NaClO4, NaAsF6, NaB(C2O4)2, NaBF2(C2O4), NaN(SO2RF)2, and NaN(SO2F)(SO2RF), where RF is C b F 2b+1 where b is an integer between 1 and 10, and optionally the electrolyte salt comprises at least one of NaPF6, NaN(SO2F)2, and NaBF2(C2O4), and optionally b is an integer between 1 and 3, and optionally RF comprises at least one of CF3, C2F5, and CF2CF2CF3. In this way, the appropriate electrolyte salt can be flexibly selected according to actual needs.

[0021] In one possible implementation, the electrolyte further includes a solvent, and the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, 1,3-dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, and acetonitrile. Optionally, the solvent includes at least one of propylene carbonate, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate. Thus, the solvent can be flexibly selected according to actual needs.

[0022] The second aspect provides a sodium-ion battery cell, and this sodium-ion battery cell includes the electrolyte in the first aspect and any one of its possible implementation manners.

[0023] In one possible implementation, the sodium-ion battery cell further includes a positive electrode plate, and the positive electrode active material in the positive electrode plate includes at least one of a Prussian blue analog, a sodium-containing phosphate, a sodium-containing transition metal oxide, and their respective modified compounds. Optionally, the Prussian blue analog includes a substance of the general formula Na x P[R(CN)6] δ ·zH2O, where P and R each independently include at least one of transition metal elements, 0 < x ≤ 2, 0 < δ ≤ 1, 0 ≤ z ≤ 10. Optionally, the sodium-containing phosphate has the general formula Na e Me c (PO4) dContains the substance of O2X, Me contains at least one of transition metal elements, X contains at least one of halogen elements, 0 < e ≦ 4, 0 < c ≦ 2, 1 ≦ d ≦ 3, and optionally, the sodium-containing transition metal oxide has the general formula Na f M g Fe h Contains the substance of O2, M contains at least one of transition metal elements, 0.67 < f < 1.1, 0.5 < g < 1, 0 < h < 0.5, and optionally, the transition metal element contains at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, Zn, and optionally, the halogen element contains at least one of F, Cl, Br. The electrolyte of the embodiments of the present application can be applied to various different battery cells, and various different battery cells contain different positive electrode active materials. Optionally, the positive electrode active material of the battery cell contains a sodium-containing transition metal oxide, and the electrolyte can be applied to the battery cell containing the above sodium-containing transition metal oxide.

[0024] The third aspect provides a secondary battery, and this secondary battery includes the sodium ion battery cell described in the second aspect.

[0025] The fourth aspect provides a power consumption device, and this power consumption device includes the secondary battery described in the third aspect.

[0026] The present application provides an electrolyte for a sodium-ion battery. The electrolyte includes a first additive, which includes a compound represented by general formula (I). The compound having the structure of general formula (I) can form a sulfite-rich interfacial passivation film on the surface of the positive electrode of a battery cell, preferentially over the electrolyte solvent. This interfacial passivation film can inhibit direct contact between the electrolyte and the positive electrode surface, thereby reducing the likelihood of electrolyte oxidation. Furthermore, sulfite is easily oxidized, and sulfite is oxidized preferentially over the electrolyte or the electrolyte solvent, thereby reducing the likelihood of electrolyte oxidation. The long carbon chain length of compound (I) can reduce the risk of generating gaseous by-products (e.g., ethylene) after oxidative decomposition of compound (I), thereby reducing the amount of gas generation in sodium-ion batteries. Adding a compound represented by general formula (I) to the electrolyte is advantageous for improving the lifespan of sodium-ion batteries and mitigating gas generation. Therefore, the technical solutions of the present application are advantageous for improving the performance of sodium-ion batteries. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram of a sodium-ion battery cell according to one embodiment of the present application. [Figure 2] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 3] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a power consuming device according to one embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the sodium ion battery electrolyte, sodium ion battery cell, secondary battery, and power consumption 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 or redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable 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 any combination is possible; i.e., any lower limit can be combined with any upper limit to form a single 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 possible. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents that the present specification has already listed all real numbers between "0-5," and "0-5" is merely 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 embodiments and optional embodiments of 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 specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

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

[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 when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0035] The sodium-ion battery cell referred to in this application is the smallest unit of a sodium-ion battery or secondary battery. A sodium-ion battery or secondary battery may include multiple sodium-ion battery cells.

[0036] Due to the abundant reserves and low cost of sodium salt raw materials, the use of sodium-ion batteries has gradually attracted attention. However, compared to lithium storage materials, the capacity and structural stability of sodium storage materials are relatively poor, resulting in relatively low energy densities of sodium-ion batteries. Research has shown that improving the operating voltage of sodium-ion batteries is beneficial for obtaining more active sodium, thereby improving the energy density of sodium-ion batteries. This is because when the operating voltage of sodium-ion batteries is improved, anion oxygen participates in electrochemical reactions, such as cooperative redox reactions with transition metals in the positive electrode material, thereby improving the specific capacity of the positive electrode material.

[0037] However, during the process of anion oxygen participating in the electrochemical reaction, anion oxygen has strong oxidizing activity and can rapidly oxidize the electrolyte solvent, which leads to a rapid decline in the life of the sodium ion battery and gas generation, which is unfavorable for improving the performance of the sodium ion battery. Some treatment methods improve the performance of sodium ion batteries by coating the positive electrode material or adding specific additives to the electrolyte. However, these treatment methods do not clearly improve the battery life and gas generation.

[0038] In view of this, the present application provides an example in which an additive is added to the electrolyte of a sodium-ion battery, the additive including a cyclic sulfate ester compound or a cyclic sulfonate ester compound having a specific structure. These compounds form an interfacial passivation film on the surface of the positive electrode, reducing the probability of contact between the electrolyte and the positive electrode surface. Furthermore, the sulfite in the interfacial passivation film is easily oxidized and can be oxidized preferentially over the solvent in the electrolyte, thereby reducing the risk of electrolyte oxidation and further improving the performance of the sodium-ion battery.

[0039] Although the electrolyte of some lithium ion batteries may also contain cyclic sulfate ester compounds or cyclic sulfonate ester compounds, because lithium ion batteries do not have the above problems of sodium ion batteries, cyclic sulfate ester compounds or cyclic sulfonate ester compounds in the electrolyte of lithium ion batteries are not used in sodium ion batteries to solve the technical problems of sodium ion batteries.

[0040] An embodiment of the present application provides an electrolyte for a sodium-ion battery, the electrolyte comprising a first additive, the first additive comprising a compound represented by general formula (I): [ka] Here, R1, R2, R3, and R4 each independently contain at least one of a single bond and an alkylene group having 1 to 4 carbon atoms, and R5 is [ka] or [ka] and R6 is [ka] and R7 includes at least one of a single bond, an alkylene group having 1 to 3 carbon atoms, and an alkyleneoxy group having 1 to 3 carbon atoms.

[0041] R1, R2, R3, and R4 each independently contain at least one of a single bond and an alkylene group having 1 to 4 carbon atoms. In other words, R1, R2, R3, and R4 may be different groups or the same group.

[0042] An alkylene group may refer to a divalent hydrocarbon group having one or more carbon atoms. The alkylene group having 1 to 4 carbon atoms may be a linear or branched alkylene group having 1 to 4 carbon atoms. Examples include a methylene group (-CH-), an ethylene group (-CHCH-), a propylene group (-CHCHCH-), a butylene group (-CHCHCHCHCH-), and an isopropylene group.

[0043] The single bond may refer to the case where the group does not contain a carbon atom. For example, when R1 is a single bond, [ka] teeth, [ka] It may be expressed as:

[0044] When R7 is a single bond, [ka] teeth, [ka] may be expressed as [ka] teeth, [ka] or [ka] It may be expressed as:

[0045] R7 includes an alkylene group having 1 to 3 carbon atoms, and for example, R7 includes a methylene group (-CH2-), an ethylene group (-CH2CH2-), and a propylene group (-CH2CH2CH2-).

[0046] An alkyleneoxy group may refer to a group composed of one alkylene group and one oxygen atom. R7 includes alkyleneoxy groups having 1 to 3 carbon atoms, such as methyleneoxy (-CHO-), ethyleneoxy (-CHO-), and propyleneoxy (-CHO-).

[0047] Compound (I) is a cyclic sulfate ester compound or a cyclic sulfonate ester compound. Compound (I) can form a sulfite-rich interfacial passivation film on the positive electrode surface of a battery cell preferentially over the electrolyte solvent. This sulfite-rich interfacial passivation film can inhibit direct contact between the electrolyte and the positive electrode surface, thereby reducing the probability of the electrolyte being oxidized.

[0048] During the charge and discharge process of a sodium-ion battery cell, some substances with strong oxidizing properties may appear, and these strong oxidizing substances may react with the electrolyte or the solvent in the electrolyte, thereby oxidizing the electrolyte. For example, for a sodium-ion battery cell whose positive electrode material contains a transition metal oxide, anionic oxygen (also called oxygen ions) may be generated during the charge and discharge process of the sodium-ion battery. The interfacial passivation film formed by compound (I) contains a large amount of sulfite, which preferentially binds to anionic oxygen and reduces the oxidative activity of anionic oxygen, thereby reducing the ability of the positive electrode surface to oxidize the electrolyte and reducing the probability of the electrolyte being oxidized.

[0049] Compound (I) has a relatively large molecular structure and weak coordination with sodium ions. Therefore, compound (I) is consumed less on the negative electrode side (e.g., during the chemical formation step, compound (I) is consumed less on the negative electrode side), allowing the first additive to retain more compound (I) and form an interfacial passivation film on the positive electrode surface. Furthermore, the long carbon chain length of compound (I) reduces the risk of generating gaseous by-products (e.g., ethylene) after oxidative decomposition of compound (I), thereby reducing the amount of gas generated in sodium-ion batteries.

[0050] In the examples of the present application, a compound represented by general formula (I) is added to the electrolyte. This can reduce the risk of oxidation of the electrolyte, which is advantageous for improving the lifespan of the sodium ion battery. Meanwhile, the risk of generating gaseous by-products after oxidative decomposition of compound (I) is relatively low, which can reduce the amount of gas generated in the sodium ion battery. Therefore, the technical solutions in the examples of the present application are advantageous for improving the performance of sodium ion battery cells.

[0051] In some embodiments, the content W1 of the first additive in the electrolyte is 0.01% to 5%, optionally 0.05% to 5%, and further optionally 0.1% to 2%, based on the total mass of the electrolyte.

[0052] The content of the first additive in the electrolyte refers to the mass ratio of the first additive to the electrolyte in the sodium ion battery cell.

[0053] The content of the first additive in the electrolyte can be determined by gas chromatography or liquid chromatography, and the structure of the first additive can be determined by gas phase mass spectrometry or liquid phase mass spectrometry.

[0054] When the content of the first additive is less than 0.01%, the effect of preventing the oxidation of the electrolyte by the interfacial passivation film formed on the surface of the positive electrode is relatively small, and the effect of improving the performance of the sodium ion battery cell is weak. When the content of the first additive is more than 5%, a large amount of reaction products due to the oxidative decomposition of compound (I) will accumulate near the positive electrode of the sodium ion battery cell, which will increase the resistance between the positive electrode active material layer and the electrolyte interface and may increase the internal resistance of the sodium ion battery cell, which is detrimental to improving the performance of the sodium ion battery cell.

[0055] In the above example, the content W1 of the first additive in the electrolyte solution is set to 0.01% to 5%, which is advantageous for further improving the performance of the sodium ion battery.

[0056] The content W1 of the first additive in the electrolyte is 0.05% to 5%, which is advantageous for further improving the performance of the sodium ion battery cell, and can achieve both the service life and internal resistance of the sodium ion battery cell.

[0057] The content W1 of the first additive in the electrolyte is 0.1% to 2%, and thus the service life and internal resistance of the sodium ion battery cell can be further improved.

[0058] In some embodiments, Compound (I) is the following compound: [ka] [ka] It includes at least one of the following.

[0059] In the above examples, selecting any one of compounds 1 to 22 as compound (I) is advantageous in extending the service life of the sodium ion battery cell and in controlling the amount of gas generated in the sodium ion battery cell.

[0060] In some embodiments, compound (I) includes at least one of compounds 9-22, and optionally, compound (I) includes at least one of compound 11, compound 12, and compound 13.

[0061] For compound 11, R5 is [ka] where R1, R2, and R4 are single bonds, R3 is a methylene group, and R6 is [ka] is.

[0062] For compound 12, R5 is [ka] where R1 and R2 are single bonds, R3 and R4 are methylene groups, and R6 is [ka] is.

[0063] For compound 13, R5 is [ka] where R1 and R2 are single bonds, R3 and R4 are methylene groups, and R6 is [ka] is.

[0064] Similarly, the specific groups contained in compounds 1 to 10 and 14 to 22 can be determined by reference to the structural formula of compound (I), and will not be described one by one here.

[0065] In the electrolyte, the consumption rate of compounds 9 to 22 is slower than that of compounds 1 to 8, which is advantageous for compounds 9 to 22 to participate in the reaction, thereby further improving the performance of the sodium-ion battery cell.

[0066] The relatively high solubility of compounds 11, 12, and 13 in the solvent of the electrolyte is favorable for compounds 11, 12, and 13 to participate in the reaction, thereby further improving the performance of the sodium-ion battery cell.

[0067] In some embodiments, the electrolyte further comprises a second additive, and the second additive comprises at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propanesultone (PS), propylene sultone (PST), vinyl sulfate (DTD), maleic anhydride, bisfluoro(oxalato)borate, succinic anhydride, and triallyl phosphate.

[0068] In some sodium-ion battery cells, the main components of the interfacial passivation film formed on the surface of the negative electrode include alkyl sodium carbonate, sodium carbonate, etc. Compared with alkyl lithium carbonate, alkyl sodium carbonate has a higher solubility in solvents, which makes the interfacial passivation film formed on the surface of the negative electrode in the sodium-ion battery cell unstable. In such cases, the reaction between the electrolyte and the negative electrode continues, which is detrimental to improving the service life of the sodium-ion battery cell.

[0069] In the embodiment of the present application, since the second additive contains an unsaturated functional group, the second additive can be reduced to the surface of the negative electrode preferentially over the solvent to form an interfacial passivation film, which can suppress the formation of easily soluble substances such as sodium alkyl carbonate and reduce side reactions occurring between the solvent in the electrolyte and the negative electrode, which is advantageous for further extending the life of the sodium ion battery cell.

[0070] In some embodiments, the content W2 of the second additive in the electrolyte is 0.01% to 10%, and optionally 0.1% to 5%, based on the total mass of the electrolyte.

[0071] If the content of the second additive is less than 0.01%, the interfacial passivation film formed by the reaction of the second additive on the negative electrode surface is small, and the effect of improving the performance of the sodium-ion battery cell is weak. If the content of the second additive is more than 10%, the interfacial passivation film formed on the negative electrode of the sodium-ion battery cell is thick, and the resistance between the negative electrode active material layer and the electrolyte increases, increasing the internal resistance of the sodium-ion battery cell and being detrimental to improving the performance of the sodium-ion battery cell. Setting the content W2 of the second additive in the electrolyte to 0.01% to 10% is advantageous to further improve the performance of the sodium-ion battery cell.

[0072] By setting the content W2 of the second additive in the electrolyte solution to 0.1% to 5%, the performance of the sodium ion battery cell can be further improved.

[0073] In some embodiments, the content W1 of the first additive in the electrolyte and the content W2 of the second additive in the electrolyte are 0.05×10 -4 ≦W1×W2≦10×10 -4 Meet the following.

[0074] The addition of the first additive and the second additive to the electrolyte both affect the internal resistance of the sodium-ion battery cell. In the above embodiment, by setting W1 and W2 to satisfy the above relationship, the life of the sodium-ion battery cell is extended while maintaining a relatively low internal resistance of the battery.

[0075] In some embodiments, the electrolyte solution further comprises an electrolyte salt, the electrolyte salt comprising at least one of NaPF, NaBF, NaN(SOF), NaClO, NaAsF, NaB(C0), NaBF(C0), NaN(SORF), NaN(SOF)(SORF), where RF is C b F 2b+1 where b is an integer between 1 and 10, and optionally the electrolyte salt comprises at least one of NaPF6, NaN(SO2F)2, and NaBF2(C2O4), and optionally b is an integer between 1 and 3, and optionally RF comprises at least one of CF3, C2F5, and CF2CF2CF3. In this way, the appropriate electrolyte salt can be flexibly selected according to actual needs.

[0076] In some embodiments, the electrolyte further comprises a solvent, and the solvent is 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, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, methyl methyl carbonate, methyl propyl ... The solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, and the solvent may be at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate. In this way, the solvent can be flexibly selected according to actual needs.

[0077] [Positive electrode plate] The positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0078] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0079] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer 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 polymer substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0080] In some embodiments, the positive electrode active material may be any positive electrode active material known in the art for use in sodium ion batteries.

[0081] 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, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0082] In some embodiments, the positive electrode film layer may further optionally 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.

[0083] In some embodiments, a positive electrode plate can be manufactured in the following manner: Components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then coated onto a positive electrode current collector, dried, cold-pressed, and other processes to obtain a positive electrode plate.

[0084] [Negative electrode 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, and the negative electrode film layer includes a negative electrode active material.

[0085] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, the metal foil sheet may be copper 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. The composite current collector may be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer base (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0087] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon, silicon oxide, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials usable as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination.

[0088] In some embodiments, the negative electrode membrane layer optionally further includes an adhesive. For example, the adhesive may be selected from at least one of styrene butadiene polymer (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0089] In some embodiments, the negative electrode film layer may further optionally include a conductive agent, for example, 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.

[0090] In some embodiments, the negative electrode membrane layer optionally further comprises other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0091] In some embodiments, a negative electrode plate can be manufactured in the following manner: Components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then coated on a negative electrode current collector, and the negative electrode plate is obtained after processes such as drying and cold pressing.

[0092] [Separator] The present application does not particularly limit the type of separator, and any known porous structure separator having good chemical stability and mechanical stability may be selected.

[0093] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0094] [Sodium-ion battery cell] The present application provides a sodium-ion battery cell, which includes the electrolyte solution of any one of the above embodiments.

[0095] The present application is not particularly limited to the shape of the sodium-ion battery cell, which may be cylindrical, rectangular, or any other shape.

[0096] 1 is a schematic diagram of a sodium-ion battery cell according to an embodiment of the present application. As shown in FIG. 1, the sodium-ion battery cell 3 includes a case 31, a cover plate 32, and an electrode assembly 33 installed in the case 31.

[0097] The case 31 and cover plate 32 may package an electrode assembly 33 and an electrolyte.

[0098] In some embodiments, the case 31 and the cover plate 32 may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The case 31 and the cover plate 32 may be a pouch, such as a bag-like pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0099] The electrode assembly 33 includes a positive electrode plate, a negative electrode plate, and a separator, and the electrode assembly 33 may be obtained by fabricating the positive electrode plate, the negative electrode plate, and the separator through a winding process or a stacking process.

[0100] Alternatively, the negative electrode surface in the examples of the present application may refer to the surface corresponding to the position of the negative electrode plate of the electrode assembly 33, more specifically, the surface of the negative electrode plate, or even the surface of the negative electrode film layer of the negative electrode plate. Similarly, the positive electrode surface in the examples of the present application may refer to the surface corresponding to the position of the positive electrode plate of the electrode assembly 33, more specifically, the surface of the positive electrode plate, or even the surface of the positive electrode film layer of the positive electrode plate.

[0101] Alternatively, the sodium-ion battery cell 3 may be a "no-negative electrode" sodium-ion battery cell, or more specifically, a "no-negative electrode" sodium metal battery cell. For a "no-negative electrode" sodium-ion battery cell, no negative electrode active material is disposed on the negative electrode current collector.

[0102] In some embodiments, the sodium-ion battery cells may be assembled into a battery module, and the number of sodium-ion battery cells included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0103] 2 is a schematic diagram of a battery module according to an embodiment of the present application. Referring to FIG. 2, in a battery module 4, a plurality of sodium-ion battery cells 3 may be arranged in a row along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of sodium-ion battery cells 3 may be fixed by fasteners.

[0104] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of sodium ion battery cells 3 are accommodated in the accommodating space.

[0105] In some embodiments, the sodium-ion battery cell further includes a positive electrode plate, and the positive electrode active material in the positive electrode plate includes at least one of a Prussian blue analog, a sodium-containing phosphate, a sodium-containing transition metal oxide, and respective modified compounds. In this embodiment, the sodium-ion battery cell includes the electrolyte and the positive electrode active material described above, and the first additive in the electrolyte can form a passivation film rich in sulfite on the positive electrode surface, thereby reducing the direct contact between the solvent of the electrolyte and the positive electrode surface (or the positive electrode active material), and further reducing the probability that the solvent in the electrolyte is oxidized.

[0106] The modified compound may refer to an improvement for improving specific performance of the positive electrode active material. For example, in order to enhance performance such as the stability of the positive electrode active material, the positive electrode active material can be modified by adopting a surface coating method. Also, for example, the positive electrode active material can be modified by adopting an ion doping method. It should be noted that the embodiments of the present application include, but are not limited to, the above modifications.

[0107] Optionally, the Prussian blue analog includes a substance of the general formula Na x P[R(CN)6] δ ·zH2O, where P and R each independently include at least one of transition metal elements, 0 < x ≦ 2, 0 < δ ≦ 1, and 0 ≦ z ≦ 10. In some embodiments, the Prussian blue analog may be Na2Ni 0.17 Co 0.83 Fe(CN)6.

[0108] Optionally, the sodium-containing phosphate includes a substance of the general formula Na e Me c (PO4) d O2X, where Me includes at least one of transition metal elements, X includes at least one of halogen elements, 0 < e ≦ 4, 0 < c ≦ 2, and 1 ≦ d ≦ 3. In some embodiments, the sodium-containing phosphate may be Na3V2(PO4)2O2F.

[0109] Optionally, the sodium-containing transition metal oxide has the general formula Na f M g Fe h O2, where M contains at least one of the transition metal elements, 0.67 < f < 1.1, 0.5 < g < 1, and 0 < h < 0.5. For example, the sodium-containing transition metal oxide may be Na 0.88 Cu 0.24 Fe 0.29 Mn 0.47 O2.

[0110] Optionally, the transition metal element contains at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, Zn.

[0111] Optionally, the halogen element contains at least one of F, Cl, Br.

[0112] Optionally, the positive electrode active material in the sodium-ion battery cell contains a sodium-containing transition metal oxide. During the charge and discharge process of the sodium-ion battery cell, due to the presence of the sodium-containing transition metal oxide, anionic oxygen may be generated. After adding the first additive to the electrolyte, the interfacial passive film formed on the positive electrode surface contains sulfite. Therefore, sulfite can preferentially bind to anionic oxygen rather than the solvent in the electrolyte, thereby reducing the probability of the electrolyte being oxidized.

[0113] [Secondary battery] This application provides a secondary battery, including the sodium-ion battery cell described in the above embodiments.

[0114] Figure 3 is a schematic diagram of a secondary battery according to an embodiment of this application. As shown in Figure 3, this application provides a secondary battery 5, including the sodium-ion battery cell 3 in any one of the above embodiments.

[0115] The sodium-ion battery cell 3 may directly constitute the secondary battery 5, or may first constitute a battery module, and the secondary battery 5 may be constituted by a plurality of battery modules.

[0116] [Power consumption equipment] The present application provides a power consuming device, which includes the secondary battery described in the above examples.

[0117] 4 is a schematic diagram of a power consumption device according to an embodiment of the present application. As shown in FIG. 4, the present application provides a power consumption device 6, which includes the secondary battery 5 in the above embodiment.

[0118] The following describes examples of the present application. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to the techniques or conditions described in literature in the field or according to the product specifications. If the manufacturer of the reagents or instruments used is not specified, they are all ordinary products available commercially.

[0119] [Example] Example 1 In Example 1, the electrolyte solution contains 1 mol / L of electrolyte salt NaPF6, a solvent, and a first additive. The solvent is propylene carbonate (PC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. The content W1 of the first additive in the electrolyte solution is 3% based on the total mass of the electrolyte solution.

[0120] The first additive is compound 12, which has the structural formula [ka] is.

[0121] Examples 2 to 10 Examples 2 to 10 differ from Example 1 in that the content W1 of the first additive is different.

[0122] In Examples 2 to 10, the contents W1 of the first additive were 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 4%, 5%, and 10%, respectively.

[0123] Examples 11 to 16 The difference between Examples 11 to 16 and the present Example is that the specific compound structure of the first additive is different.

[0124] Example 11: [ka]

[0125] Example 12: [ka]

[0126] Example 13: [ka]

[0127] Example 14: [ka]

[0128] Example 15: [ka]

[0129] Example 16: [ka]

[0130] Example 17 The difference between Example 17 and Example 1 is that the electrolyte solution further contains a second additive, the second additive is fluoroethylene carbonate (FEC), and the content W2 of the second additive is 2% (2% may be expressed as 0.02) based on the total mass of the electrolyte solution, and W1 × W2 is 6 × 10 -4 That is to be.

[0131] Examples 18 to 26 Examples 18 to 26 differ from Example 17 in that the content W2 of the second additive is different.

[0132] In Examples 18 to 26, the content W2 of the second additive was 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 4%, 5%, and 10%, respectively, and W1 × W2 was 0.03 × 10 -4 , 0.15×10 -4 , 0.3×10 -4 , 1.5×10 -4 , 3×10 -4 , 9×10 -4 , 12×10 -4 , 15×10 -4 , 30×10 -4 is.

[0133] Example 27 The difference between Example 27 and Example 17 is that the content W1 of the first additive and the content W2 of the second additive are different. The content W1 of the first additive is 5%, the content W2 of the second additive is 0.01%, and W1 × W2 is 0.05 × 10 -4 is.

[0134] Example 28 The difference between Example 28 and Example 17 is that the content W1 of the first additive and the content W2 of the second additive are different. The content W1 of the first additive is 2%, the content W2 of the second additive is 5%, and W1 × W2 is 10 × 10 -4 is.

[0135] Examples 29-30 Examples 29 to 30 differ from Example 17 in that the second additive was different.

[0136] In Examples 29 and 30, the second additives are vinylene carbonate (VC) and vinyl sulfate (DTD), respectively.

[0137] Comparative Example 1 In Comparative Example 1, the electrolyte solution does not contain the first additive and the second additive used in the examples of the present application. In Comparative Example 1, the electrolyte salt in the electrolyte solution is NaPF6, the solvent is propylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7, and the concentration of the electrolyte salt is 1 mol / L.

[0138] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that the electrolytic solution contains vinyl sulfate, and the content of vinyl sulfate in the electrolytic solution is 1% based on the total mass of the electrolytic solution.

[0139] [Electrolyte solution manufacturing method] First, ethylene carbonate and ethyl methyl carbonate (volume ratio: 3:7) were mixed to obtain a mixed solvent. Then, the mixed solvent, additive, and NaPF6 were mixed and stirred in a weight ratio of (1-w-0.138):w:0.138, where w is the mass percentage of the additive. Once completely dissolved, the required electrolyte was obtained.

[0140] [Manufacturing sodium-ion battery cells] The active material is Na 0.88 Cu 0.24 Fe 0.29 Mn 0.47 O2, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were mixed in a weight ratio of 90:5:5 in an N-methylpyrrolidone solvent system by sufficient stirring to obtain a positive electrode slurry. The positive electrode slurry was then mixed at a density of 0.28 g (dry weight) / 1540.25 mm. 2 The aluminum foil was dried at room temperature and then transferred to a 120°C oven for 1 hour. The foil was then cold pressed and slit to obtain a positive electrode plate.

[0141] The active material, hard carbon, the conductive agent, acetylene black, the adhesive, styrene butadiene rubber, and the thickener, sodium carboxymethyl cellulose, were mixed in a weight ratio of 90:4:4:2 in a deionized water solvent system by sufficient stirring to obtain a negative electrode slurry. The negative electrode slurry was then mixed to obtain a negative electrode slurry of 0.14 g (dry weight) / 1540.25 mm. 2 The amount of the coating was uniformly applied to a 13 μm thick aluminum foil negative electrode current collector, and the copper foil was dried at room temperature and then transferred to an oven at 120°C for 1 hour. The negative electrode plate was then obtained by cold pressing and slitting.

[0142] The separator is a porous polyethylene (PE) polymer film with a thickness of 9 μm.

[0143] A positive electrode plate, a separator, and a negative electrode plate are stacked in this order, with a separator positioned between the positive and negative electrodes to provide isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in a case, and the prepared electrolyte is injected and packaged to obtain a sodium-ion battery cell.

[0144] [Testing of additive type and content] The types of the first additive and the second additive can be determined by a gas phase mass spectrometer (which may also be called a gas chromatography mass spectrometer) or a liquid phase mass spectrometer, and the contents of the first additive and the second additive in the electrolyte can be determined by a gas chromatograph or a liquid chromatograph.

[0145] For example, a sample can be placed in a liquid phase mass spectrometer and the instrument's qualitative analysis can determine the specific type of additive in the sample, followed by the use of a liquid chromatograph to determine the content of the additive in the sample.

[0146] [Cycle performance test] At 25°C, a freshly manufactured sodium-ion battery cell was left for 5 minutes, charged to 4.2V at a constant current of 1C, then charged at a constant voltage until the current fell to 0.05C or less, left for 5 minutes, and then discharged to 1.5V at a constant current of 1C. This constituted one charge-discharge cycle, and the discharge capacity of this cycle was taken as the first-cycle discharge capacity of the sodium-ion battery cell. The sodium-ion battery cell was subjected to 800 charge-discharge cycles according to the above method, and the discharge capacity of each cycle was recorded.

[0147] Capacity retention rate after 400 cycles of a sodium-ion battery cell at 25°C and 1C / 1C = Discharge capacity at the 800th cycle / Discharge capacity at the 1st cycle × 100%.

[0148] [DC Impedance Test] At 25°C, the sodium-ion battery cell was left for 5 minutes, then charged to 4.2V at a constant current of 1C, and then further charged at a constant voltage until the current dropped to 0.05C or less, at which point the battery's state of charge (SOC) was set to 100%. After that, the cell was left for 5 minutes, and then discharged for 30 minutes at a constant current of 1C, adjusting the sodium-ion battery cell's state of charge (SOC) to 50%.

[0149] A sodium-ion battery cell at 50% SOC was left for 10 minutes and then discharged at a constant current of 4C for 30 seconds. The voltage U1 in the last second of the period, the voltage U2 in the last second of the 4C constant current discharge, and the current I during the 4C constant current discharge were recorded. The DC impedance R when the sodium-ion battery cell was discharged at 25°C, 50% SOC, and 4C constant current for 30 seconds was R = (U1 - U2) / (I).

[0150] [Volume expansion rate test] At 25°C, the battery was charged at a constant current of 1C until the voltage reached 4.2V, and then at a constant voltage of 4.2V until the current reached 0.05C. At this time, the volume of the sodium-ion battery cell was measured and designated as V1. The fully charged sodium-ion battery cell was then placed in a thermostatic chamber at 60°C and stored for two months. The volume was then measured using the drainage method and designated as V2.

[0151] The volume expansion rate of a sodium-ion battery after storing it at 60°C for two months is (V2-V1) / V1 x 100%.

[0152] For experimental data of the examples and comparative examples, please refer to Table 1. In Table 1, A represents the capacity retention rate of the sodium ion battery cell, R represents the DC impedance of the sodium ion battery cell, and B represents the volume expansion rate of the sodium ion battery cell. For specific structural formulas of the compounds in Table 1, please refer to the above.

[0153] [Table 1] Experimental data for Examples and Comparative Examples [Table 1] [Table 2] [Table 3]

[0154] The service life of a sodium-ion battery cell is related to its capacity retention rate; the higher the capacity retention rate, the longer the service life. The DC impedance of a sodium-ion battery cell can characterize the internal resistance of the sodium-ion battery cell; the higher the DC impedance, the higher the internal resistance. The amount of gas generated by a sodium-ion battery cell is related to its volume expansion rate; the more gas generated, the higher the volume expansion rate.

[0155] As shown in Examples 1 to 10, by setting the content of the first additive appropriately, the sodium ion battery cell can have a relatively good capacity retention rate. As shown in Examples 1 to 9, by setting the content of the first additive to 0.1 wt% to 5 wt%, the service life of the sodium ion battery can be improved while maintaining a relatively low internal resistance.

[0156] As shown in Examples 11-16 taken together, various compounds conforming to general formula (I) can all be added as a first additive to the electrolyte to improve the service life of sodium-ion batteries.

[0157] As shown in conjunction with Examples 17 to 26, adding a second additive to the electrolyte is advantageous for further improving the service life of sodium ion batteries.

[0158] As shown in Example 17, Examples 19-23, and Examples 27-28, by rationally setting the content of the first additive and the second additive, it is possible to improve the service life of the sodium ion battery while maintaining a relatively low internal resistance.

[0159] As shown in Examples 29-30, adding various different second additives to the electrolyte is beneficial for improving the service life of sodium ion batteries.

[0160] As shown by combining Examples 1 to 30 and Comparative Example 1, the capacity retention rate was relatively high and the volume expansion rate was relatively low in Examples 1 to 30. Adding the first additive to the electrolyte solution is advantageous in improving the service life of the sodium ion battery and improving the gas generation phenomenon.

[0161] As shown by combining Example 6 and Comparative Example 2, Example 6 had a relatively high capacity retention rate and a relatively low volume expansion rate. Compared to the compound represented by general formula (I) in the examples of the present application, this compound has a very strong coordination ability between vinyl sulfate and sodium ions. During the formation process, the negative electrode quickly reaches a low potential, and vinyl sulfate mainly forms a film on the negative electrode, with the small amount of remaining vinyl sulfate acting on the positive electrode. This results in an inconsistent inhibitory effect on the oxidation of the solvent in the electrolyte, making it difficult to extend the service life of the sodium-ion battery cell. Increasing the vinyl sulfate content leads to excessive film formation on the negative electrode, increasing the internal resistance of the sodium-ion battery cell. Meanwhile, the oxidation of vinyl sulfate produces many short-chain gaseous substances, such as ethylene, resulting in the generation of large amounts of gas.

[0162] Combined with the above embodiments, the technical solutions of the embodiments of the present application can improve the service life of sodium ion battery cells and reduce the gas generation phenomenon, which is beneficial to improving the performance of sodium ion battery cells.

[0163] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments without departing from the spirit of the present application, and other methods configured by combining some of the components of the embodiments, are also included within the scope of the present application.

Claims

1. An electrolyte for a sodium ion battery, the electrolyte including a first additive, the first additive including a compound represented by general formula (I), 【Chemistry 1】 Here, R1, R2, R3, and R4 each independently contain at least one of a single bond and an alkylene group having 1 to 4 carbon atoms, and R5 is 【Chemistry 2】 or 【Transformation 3】 and R6 is 【Chemistry 4】 and R7 includes at least one of a single bond, an alkylene group having 1 to 3 carbon atoms, and an alkyleneoxy group having 1 to 3 carbon atoms.

2. The content W of the first additive in the electrolytic solution is determined based on the total mass of the electrolytic solution. １ 2. The electrolyte of claim 1, wherein the content of Zn is 0.01% to 5%, optionally 0.05% to 5%, and further optionally 0.1% to 2%.

3. The compound (I) is the following compound: 【Transformation 5】 【Transformation 6】 3. The electrolyte solution according to claim 1, further comprising at least one of:

4. The compound (I) includes at least one of compounds 9 to 22, and optionally includes at least one of compounds 11, 12, and 13. The electrolyte solution according to claim 3.

5. 5. The electrolytic solution according to claim 1, further comprising a second additive, the second additive comprising at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, propylene sultone, vinyl sulfate, maleic anhydride, bisfluoro(oxalato)borate, succinic anhydride, and triallyl phosphate.

6. The content W of the second additive in the electrolytic solution is based on the total mass of the electrolytic solution. ２ 6. The electrolyte of claim 5, wherein is between 0.01% and 10%, and optionally between 0.1% and 5%.

7. The content W of the first additive in the electrolytic solution １ and the content W of the second additive in the electrolyte solution ２ That is, 0.05 x 10 －４ ≦W １ ×W ２ ≦10×10 －４ 7. The electrolytic solution according to claim 5, wherein the above formula satisfies the above formula.

8. The electrolyte solution further includes an electrolyte salt, and the electrolyte 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 RF) ２ , NaN(SO ２ F) (SO ２ RF), wherein RF is C ｂ F ２ｂ＋１ wherein b is an integer from 1 to 10, and optionally the electrolyte salt is NaPF ６ , NaN(SO ２ F) ２ , NaBF ２ (C ２ O ４ ), optionally b is an integer from 1 to 3, and optionally RF is CF ３ , C ２ F ５ , C.F. ２ CF ２ CF ３ The electrolyte solution according to any one of claims 1 to 7, characterized in that it contains at least one of the following:

9. The electrolyte solution further includes a solvent, and the solvent is 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, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, and ethyl methyl sulfone.

9. The electrolytic solution according to claim 1, wherein the solvent contains at least one of propylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

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

11. The sodium ion battery cell further includes a positive electrode plate, and the positive electrode active material in the positive electrode plate includes at least one of a Prussian blue analog, a sodium-containing phosphate, a sodium-containing transition metal oxide, and a respective modification compound; and optionally, the Prussian blue analog has the general formula Na ｘ P [R (CN) ６ ] δ zH2O, wherein P and R each independently comprise at least one transition metal element, and 0<x≦2, 0<δ≦1, 0≦z≦10; and optionally, the sodium-containing phosphate has the general formula Na ｅ Me ｃ (P.O. ４ ) ｄ O ２ X, wherein Me comprises at least one transition metal element, X comprises at least one halogen element, and 0<e≦4, 0<c≦2, 1≦d≦3; and optionally, the sodium-containing transition metal oxide is represented by the general formula Na ｆ M ｇ Fe ｈ O ２ wherein M comprises at least one of a transition metal element, and 0.67<f<1.1, 0.5<g<1, 0<h<0.5; optionally, the transition metal element comprises at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn; and optionally, the halogen element comprises at least one of F, Cl, and Br.

12. A secondary battery comprising the sodium ion battery cell according to claim 10 or 11.

13. A power consuming device comprising the secondary battery of claim 12.

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