Electrolyte, battery and electric device

Abstract

The invention provides an electrolyte, a battery and an electric device. The electrolyte comprises a molten salt electrolyte and an organic solvent. The molten salt electrolyte in the electrolyte is in a solid state at a standard temperature and atmospheric pressure and is in a liquid-phase molten state after the temperature rises to a certain temperature, and the vapor pressure of the molten salt electrolyte is relatively low, so that the working temperature range of the battery can be expanded upwards. The molten salt electrolyte in the electrolyte is not easy to decompose at high temperature and high pressure, and has better stability, so that the cycle performance of the battery can be improved. And due to the existence of the organic solvent, the stability of the electrolyte at high temperature and high pressure can be further improved, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to an electrolyte, a battery, and an electrical device. Background Art

[0002] The electrolyte is a carrier for ion transport in the battery, and it plays a role in conducting ions between the positive and negative electrodes of the battery. The electrolyte generally includes an electrolyte salt, an organic solvent, and an additive. The electrolyte will affect the operating temperature and operating voltage of the battery. Generally, for example, the operating temperature of a lithium-ion battery can be 0 - 40 °C, and the operating voltage of a lithium-ion battery can be 3 - 4 V. At higher operating temperatures and higher operating voltages, the electrolyte is prone to self-decomposition and consumes more active lithium, resulting in a problem of decreased battery cycle performance. Summary of the Invention

[0003] The present application is made in view of the above problems, and its purpose is to provide an electrolyte, a battery, and an electrical device that can improve the cycle performance of the battery under high temperature and high pressure conditions.

[0004] To achieve the above object, the embodiments of the present application provide an electrolyte, a battery, and an electrical device.

[0005] In a first aspect, the embodiments of the present application propose an electrolyte, including a molten salt electrolyte and an organic solvent.

[0006] In the embodiments of the present application, the molten salt electrolyte in the electrolyte is solid at standard temperature and atmospheric pressure and becomes a liquid molten state when the temperature rises to a certain temperature, and the vapor pressure of the molten salt electrolyte is relatively low. Thus, the operating temperature range of the battery can be extended upward. And the molten salt electrolyte in the electrolyte is not easily decomposed under high temperature and high pressure, and has better stability, thereby being able to improve the cycle performance of the battery. The presence of the organic solvent can further enhance the stability of the electrolyte under high temperature and high pressure and improve the cycle performance of the battery.

[0007] In any embodiment, the molten salt electrolyte includes at least two molten salts. The melting point of a single molten salt is usually much higher than room temperature. Using a molten salt electrolyte composed of at least two molten salts can form a molten salt mixture with a lower eutectic point, so that the operating temperature range of the battery is wider.

[0008] In any embodiment, at least one molten salt in the molten salt electrolyte includes a metal cation and a fluorinated organic anion. The fluorinated organic anion in the molten salt electrolyte can react with active lithium during the charge and discharge process of the battery and participate in the formation of an inorganic SEI film. The SEI film contains LiF, which helps to improve the cycle performance of the battery under high temperature and high pressure.

[0009] In any embodiment, the metal cations of at least one molten salt in the molten salt electrolyte include lithium ions. The molten salt electrolyte contains the same metal cations as the battery active material, which can quickly achieve the insertion and extraction of metal cations in the positive and negative electrode materials.

[0010] In any embodiment, the metal cations further include at least one of potassium ions, rubidium ions, cesium ions, francium ions, magnesium ions, calcium ions, strontium ions, and barium ions. Selecting appropriate alkali metal ions or alkaline earth metal ions helps to form a molten salt electrolyte that is solid at standard temperature and atmospheric pressure and becomes liquid and molten when the temperature rises to a certain temperature.

[0011] In any embodiment, the fluorinated organic anions include at least one of bis(fluorosulfonyl)imide ions, bis(trifluoromethanesulfonyl)imide ions, and bis(pentafluoroethylsulfonyl)imide ions. Appropriate fluorinated organic anions are beneficial to form a stable SEI film containing LiF, which helps to improve the cycling performance of the battery at high temperature and high pressure.

[0012] In any embodiment, the molten salt electrolyte includes two molten salts; optionally, at least one of the two molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(pentafluoroethylsulfonyl)imide; optionally, one of the two molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, or rubidium bis(pentafluoroethylsulfonyl)imide. The molten salt electrolyte formed by mixing two molten salts can form a molten salt mixture with a lower eutectic point, so that the operating temperature range of the battery is wider. Selecting appropriate two molten salts can, while forming a lower eutectic point, be beneficial to improving the thermal stability and high-pressure stability of the electrolyte, thereby improving the cycling performance of the battery at high temperature and high pressure.

[0013] In any embodiment, the mass percentage of each molten salt in the two molten salts in the molten salt electrolyte is 40%-60%. Controlling the mass percentage of each molten salt in the two molten salts within a suitable range is beneficial to forming a low eutectic point and improving the thermal stability and high-pressure stability of the electrolyte.

[0014] In any embodiment, the molten salt electrolyte includes three molten salts; optionally, at least one of the three molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(pentafluoroethylsulfonyl)imide; optionally, at least one of the three molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, or rubidium bis(pentafluoroethylsulfonyl)imide. The molten salt electrolyte formed by mixing three molten salts can form a molten salt mixture with a lower eutectic point, so that the operating temperature range of the battery is wider. By selecting appropriate three molten salts, while forming a lower eutectic point, it is beneficial to improve the thermal stability and high-voltage stability of the electrolyte, thereby improving the cycling performance of the battery at high temperature and high pressure.

[0015] In any embodiment, the mass percentage of each molten salt in the three molten salts in the molten salt electrolyte is 10%-80%. Controlling the mass percentage of each molten salt in the three molten salts within a suitable range is beneficial to form a low eutectic point and improve the thermal stability and high-voltage stability of the electrolyte.

[0016] In any embodiment, the organic solvent includes a saturated alkane with a carbon atom number greater than or equal to 20. The saturated alkane with the carbon atom number controlled within a suitable range has appropriate viscosity and melting point, which is beneficial to the movement of carriers in the electrolyte. And the saturated alkane with the carbon atom number controlled within a suitable range has good thermal stability and is not easily decomposed under high pressure, so it is beneficial to improve the thermal stability and high-voltage stability of the electrolyte and the cycling performance of the battery at high temperature and high pressure. Moreover, some saturated alkanes can participate in the formation of an organic SEI film to improve the toughness of the SEI film.

[0017] In any embodiment, the organic solvent includes a compound having the structure shown in Formula I:

[0018]

[0019] Wherein, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, and a substituted or unsubstituted biphenyl group.

[0020] The organic solvent having the structure shown in Formula I has good thermal stability and is not easily decomposed under high pressure, so it is beneficial to improve the thermal stability and high-voltage stability of the electrolyte and the cycling performance of the battery at high temperature and high pressure. Moreover, the organic solvent having the structure shown in Formula I can participate in the formation of an organic SEI film to improve the toughness of the SEI film.

[0021] In any embodiment, the organic solvent includes a saturated alkane having 20 or more carbon atoms and a compound having the structure shown in Formula I:

[0022]

[0023] Wherein, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, and a substituted or unsubstituted biphenyl group.

[0024] The organic solvent containing both a saturated alkane having 20 or more carbon atoms and an organic solvent having the structure shown in Formula I can utilize the advantages of the two solvents, endowing the organic solvent with good thermal stability and being not easily decomposed under high pressure, which is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure. At the same time, the organic solvent can participate in the formation of an organic SEI film and enhance the toughness of the SEI film.

[0025] In any embodiment, the number of carbon atoms of the saturated alkane is n, where 20 ≤ n ≤ 60. Optionally, the saturated alkane includes at least one of eicosane, docosane, hexacosane, tetracontane, and hexacontane. Selecting a suitable saturated alkane is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure.

[0026] In any embodiment, the organic solvent includes at least one of benzene, biphenyl, p-xylene, m-xylene, diphenyl ether, and benzoquinone. Selecting a suitable organic solvent having the structure shown in Formula I is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery.

[0027] In any embodiment, the mass ratio between the saturated alkane having 20 or more carbon atoms and the compound having the structure shown in Formula I is (1 to 3):(1 to 3). Controlling the mass ratio of the two solvents in the organic solvent within a suitable range can give play to the advantages of the two solvents, which is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure.

[0028] In any embodiment, the mass fraction of the molten salt electrolyte in the electrolyte is 80% to 90%, and / or the mass fraction of the organic solvent in the electrolyte is 10% to 20%. Thus, the main component of the electrolyte is the molten salt electrolyte, and the molten salt electrolyte is not easily decomposed at high temperature and high pressure and has better stability, thereby improving the cycling performance of the battery.

[0029] In a second aspect, an embodiment of the present application provides a battery, which includes a positive electrode plate, a negative electrode plate, a separator, and the electrolyte of the first aspect of the present application.

[0030] In any implementation manner, the battery includes a lithium-ion battery or a sodium-ion battery.

[0031] In a third aspect, an embodiment of the present application provides a method for preparing a battery, which includes a liquid injection step. The liquid injection step includes: injecting the electrolyte of the first aspect of the present application under a condition higher than the melting point of the molten salt electrolyte. Thus, the molten salt electrolyte that is solid at standard temperature and atmospheric pressure can be injected in the form of a liquid molten state, making the preparation of the battery more convenient.

[0032] In any implementation manner, the preparation method further includes a formation step. After the liquid injection step, formation treatment is performed under a condition higher than the melting point of the molten salt electrolyte in the electrolyte. The molten salt electrolyte that is solid at standard temperature and atmospheric pressure is subjected to formation treatment in the form of a liquid molten state to activate the battery.

[0033] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes the battery of the second aspect of the present application. Description of the Drawings

[0034] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0035] Figure 2 is Figure 1 an exploded view of the secondary battery according to an embodiment of the present application shown in

[0036] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0037] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0038] Figure 5 is Figure 4 an exploded view of the battery pack according to an embodiment of the present application shown in

[0039] Figure 6 is a schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0040] Description of the Reference Numerals:

[0041] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly Detailed Embodiments

[0042] Hereinafter, embodiments of the electrolyte, battery, and electrical device of the present application will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0043] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0046] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application are open-ended and can also be closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included or contained, or only the components listed can be included or contained.

[0048] Unless otherwise specified, 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, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0049] The electrolyte is the carrier for ion transport in the battery and plays a role in conducting ions between the positive and negative electrodes of the battery. The electrolyte generally includes electrolyte salts, organic solvents, and additives. The electrolyte will affect the operating temperature and operating voltage of the battery. Generally, by way of example, the operating temperature of a lithium-ion battery can be 0 - 40 °C, and the operating voltage of a lithium-ion battery can be 3 - 4 V. At higher operating temperatures and higher operating voltages, the electrolyte is prone to self-decomposition and consumes more active lithium, resulting in a problem of decreased battery cycling performance.

[0050] Based on this, a first aspect of this application provides an electrolyte, comprising a molten salt electrolyte and an organic solvent.

[0051] In the embodiments of this application, the molten salt electrolyte in the electrolyte is solid at standard temperature and atmospheric pressure and becomes a liquid molten state when the temperature rises to a certain temperature, and the vapor pressure of the molten salt electrolyte is relatively low. Thus, the operating temperature range of the battery can be extended upward. Moreover, the molten salt electrolyte in the electrolyte is not easily decomposed at high temperature and high pressure and has better stability, thereby being able to improve the cycling performance of the battery. The presence of the organic solvent can further enhance the stability of the electrolyte at high temperature and high pressure and improve the cycling performance of the battery.

[0052] In this article, the term "molten salt electrolyte" refers to a molten salt that can serve as an electrolyte in the electrolyte. A molten salt refers to a salt that is solid at standard temperature and atmospheric pressure and exists in the liquid phase when the temperature rises to a certain temperature.

[0053] It should be noted that the electrolyte can be applied to batteries, for example, applied to lithium-ion batteries. The organic electrolyte in lithium-ion batteries is very easy to react with active lithium, forming a large amount of organic matter and a highly lithophilic embedded SEI film (solid electrolyte interface), which is conducive to the vertical growth of lithium dendrites on the SEI film. Lithium dendrites not only continuously consume lithium and electrolyte, resulting in a decrease in the cycle performance of the battery, but also pose a safety risk. Therefore, the ideal SEI layer composition is low in organic matter and high in inorganic matter. A promising method to completely remove organic matter from the SEI film is to use molten salt instead of organic solvent in the electrolyte. However, for an electrolyte composed entirely of molten salt, during the charge and discharge process of the battery, the inorganic SEI film formed has poor toughness and is prone to fragmentation.

[0054] Surprisingly, the presence of an organic solvent in the electrolyte of the embodiments of the present application can compensate for the problem of poor toughness of the inorganic SEI film. Based on the inorganic SEI film formed by the molten salt electrolyte, the presence of the organic solvent can form an organic SEI film on the inorganic SEI film, and the formation of the organic SEI film compensates for the problems of poor toughness and easy fragmentation of the inorganic SEI film.

[0055] In any implementation manner, the molten salt electrolyte includes at least two molten salts. The melting point of a single molten salt is usually much higher than room temperature. A molten salt electrolyte formed by mixing at least two molten salts can form a molten salt mixture with a lower eutectic point, so that the operating temperature range of the battery is wider. Herein, the eutectic point refers to the lowest melting point formed by the mixing of two or more substances in the solid state under a certain pressure (for example, under standard atmospheric pressure). At the eutectic point, the melting points of these substances decrease, forming a common melting point. The decrease in the melting point has a positive correlation with the size ratio of at least two molten salts.

[0056] In any implementation manner, at least one molten salt in the molten salt electrolyte includes a metal cation and a fluorinated organic anion. The fluorinated organic anion in the molten salt electrolyte can react with active lithium during the charge and discharge process of the battery and participate in the formation of the inorganic SEI film. The SEI film contains LiF, which helps to improve the cycle performance of the battery under high temperature and high pressure. The molten salt electrolyte of the electrolyte already contains fluorine, and there is no need to additionally add other fluorine-containing additives, which is beneficial to making the electrolyte composition simpler.

[0057] In any embodiment, the metal cations of at least one molten salt in the molten salt electrolyte include lithium ions. The molten salt electrolyte contains the same metal cations as the battery active material, which can quickly achieve the insertion and extraction of metal cations in the positive and negative electrode materials. For example, for a lithium-ion battery, the electrolyte contains lithium ions. During the charging reaction, lithium ions are removed from the positive electrode and obtained by the negative electrode, and vice versa during discharging. Thus, a certain directional movement of ions is maintained through the electrolyte, and the insertion and extraction of lithium ions in the positive and negative electrode materials are quickly achieved.

[0058] In any embodiment, the metal cations further include at least one of potassium ions, rubidium ions, cesium ions, francium ions, magnesium ions, calcium ions, strontium ions, and barium ions. Selecting appropriate alkali metal ions or alkaline earth metal ions helps to form a molten salt electrolyte that is solid at standard temperature and atmospheric pressure and becomes liquid and molten when the temperature rises.

[0059] In any embodiment, the fluorinated organic anions include at least one of bis(fluorosulfonyl)imide ion, bis(trifluoromethanesulfonyl)imide ion, and bis(pentafluoroethylsulfonyl)imide ion. Appropriate fluorinated organic anions are beneficial to form a stable SEI film containing LiF, which helps to improve the cycling performance of the battery at high temperature and high pressure.

[0060] In any embodiment, the molten salt electrolyte includes two molten salts. The molten salt electrolyte formed by mixing two molten salts can form a molten salt mixture with a lower eutectic point, so that the operating temperature range of the battery is wider. Selecting appropriate two molten salts can, while forming a lower eutectic point, be beneficial to improving the thermal stability and high-pressure stability of the electrolyte, thereby improving the cycling performance of the battery at high temperature and high pressure. Specifically, at least one of the two molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(pentafluoroethylsulfonyl)imide. One of the two molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, or rubidium bis(pentafluoroethylsulfonyl)imide. For example, the two molten salts can be any two lithium salts, or the two molten salts can be any one lithium salt and any one non-lithium salt. Exemplarily, the two molten salts can be lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide; the two molten salts can be lithium bis(fluorosulfonyl)imide and sodium bis(fluorosulfonyl)imide.

[0061] In any embodiment, the mass percentage of each of the two molten salts in the molten salt electrolyte is 40%-60%; within this appropriate range, it is beneficial to form a low eutectic point, improving the thermal stability and high-voltage stability of the electrolyte. The mass percentage of each of the two molten salts in the molten salt electrolyte can be 40%, 45%, 50%, 55%, 60%, or within the range composed of any of the above values.

[0062] In any embodiment, the molten salt electrolyte includes three molten salts. The molten salt electrolyte formed by mixing three molten salts can form a molten salt mixture with a lower eutectic point, enabling a wider operating temperature range for the battery. By selecting appropriate three molten salts, while forming a lower eutectic point, it is beneficial to improve the thermal stability and high-voltage stability of the electrolyte, thereby enhancing the cycling performance of the battery at high temperatures and high pressures. Specifically, at least one of the three molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium bis(pentafluoroethylsulfonyl)imide; at least one of the three molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, or rubidium bis(pentafluoroethylsulfonyl)imide. For example, the three molten salts can be lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, and potassium bis(trifluoromethanesulfonyl)imide.

[0063] In any embodiment, the mass percentage of each of the three molten salts in the molten salt electrolyte is 10%-80%; within this appropriate range, it is beneficial to form a low eutectic point, improving the thermal stability and high-voltage stability of the electrolyte. The mass percentage of each of the three molten salts in the molten salt electrolyte can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or within the range composed of any of the above values.

[0064] In any embodiment, the organic solvent includes saturated alkanes with 20 or more carbon atoms. Saturated alkanes with the carbon atom number controlled within an appropriate range have appropriate viscosity and melting point, which are beneficial for the movement of carriers in the electrolyte. Moreover, saturated alkanes with the carbon atom number controlled within an appropriate range have good thermal stability and are not easily decomposed under high pressure, thus being beneficial to improving the thermal stability and high-voltage stability of the electrolyte and enhancing the cycling performance of the battery at high temperatures and high pressures. Additionally, some saturated alkanes can participate in the formation of the organic SEI film, improving the toughness of the SEI film.

[0065] In this article, "saturated alkane" refers to a straight-chain or branched-chain hydrocarbon chain group composed of carbon and hydrogen atoms, in which the carbon atoms in the molecule are all connected by single bonds, and the remaining valence bonds are all combined with hydrogen to form a compound. The general formula is C n H 2n+2 .

[0066] In any embodiment, the organic solvent includes a compound having the structure shown in Formula I:

[0067]

[0068] Wherein, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, and a substituted or unsubstituted biphenyl group.

[0069] In this article, the hydroxyl group refers to -OH.

[0070] In this article, the carboxyl group refers to -COOH.

[0071] In this article, the carbonyl group refers to -C=O.

[0072] In this article, "C1-C12 alkyl" refers to a straight-chain or branched-chain hydrocarbon chain group composed only of carbon and hydrogen atoms, having no unsaturation in the group, having 1 to 12 carbon atoms, and being attached to the rest of the molecule by a single bond. Suitable examples include, but are not limited to: methyl (-CH3), ethyl (-CH2CH3), 1-propyl (-CH2CH2CH3), 2-propyl (-CH(CH3)2), 1-butyl (-CH2CH2CH2CH3), 2-methyl-1-propyl (-CH2CH(CH3)2).

[0073] In this article, "C2-C12 alkenyl" refers to an alkenyl group containing 2-12 carbon atoms, and the alkenyl group refers to a hydrocarbon containing a group with C=C. Suitable examples include, but are not limited to: vinyl (-CH=CH2), allyl (-CH2CH=CH2), 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0074] In this article, "C2-C12 alkynyl" refers to an alkynyl group containing 2-12 carbon atoms, and the alkynyl group refers to a hydrocarbon containing a group with C≡C. Suitable examples include, but are not limited to: ethynyl, propargyl, isopropylacetyl, pentynyl.

[0075] In this article, "C3-C8 cycloalkyl" refers to a cyclic alkyl group having 3-8 carbon atoms. Suitable examples include, but are not limited to: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl.

[0076] In this article, "aryl" refers to an aromatic hydrocarbon group derived by removing one hydrogen atom from an aromatic ring compound. C5-C6 aryl refers to an aryl group containing 5-6 carbon atoms. Suitable examples include, but are not limited to: benzene.

[0077] In this text, "biphenylyl" refers to a group derived by removing one hydrogen atom from biphenyl.

[0078] In this text, "substituted" means that at least one hydrogen atom of the compound or chemical moiety is replaced by another chemical moiety with a substituent, and the substituents are each independently selected from: hydroxyl, mercapto, amino, cyano, nitro, aldehyde, halogen atom, alkenyl, alkynyl, aryl, heteroaryl, C1-6 alkyl, C1-6 alkoxy.

[0079] The organic solvent having the structure shown in Formula I has good thermal stability and is not easily decomposed under high pressure, which is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure. Moreover, the organic solvent having the structure shown in Formula I can participate in the formation of an organic SEI film and enhance the toughness of the SEI film.

[0080] In any embodiment, the organic solvent includes a saturated alkane with a carbon atom number greater than or equal to 20 and a compound having the structure shown in Formula I:

[0081]

[0082]

[0083] Wherein, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, a substituted or unsubstituted biphenylyl group.

[0084] When the organic solvent contains both a saturated alkane with a carbon atom number greater than or equal to 20 and an organic solvent having the structure shown in Formula I, the advantages of the two solvents can be utilized to make the organic solvent have good thermal stability and not be easily decomposed under high pressure, which is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure. At the same time, the organic solvent can participate in the formation of an organic SEI film and enhance the toughness of the SEI film.

[0085] In any embodiment, the carbon atom number of the saturated alkane is n, where 20 ≤ n ≤ 60. The saturated alkane includes at least one of eicosane, docosane, hexacosane, tetracontane, hexacontane. Selecting a suitable saturated alkane is beneficial to improving the thermal stability and high-pressure stability of the electrolyte and enhancing the cycling performance of the battery at high temperature and high pressure.

[0086] In any embodiment, the organic solvent includes at least one of benzene, biphenyl, p-xylene, m-xylene, diphenyl ether, and benzoquinone. Selecting a suitable organic solvent having the structure shown in Formula I is beneficial to improving the thermal stability and high-voltage stability of the electrolyte, and enhancing the cycling performance of the battery at high temperature and high voltage.

[0087] In any embodiment, the mass ratio between the saturated alkane with a carbon atom number greater than or equal to 20 and the compound having the structure shown in Formula I is (1-3):(1-3). Controlling the mass ratio of the two solvents in the organic solvent within a suitable range can bring into play the advantages of the two solvents, which is beneficial to improving the thermal stability and high-voltage stability of the electrolyte, and enhancing the cycling performance of the battery at high temperature and high voltage. The mass ratio between the saturated alkane with a carbon atom number greater than or equal to 20 and the compound having the structure shown in Formula I can be 1:1, 1:2, 1:3, 3:1, 2:1, 1:1.

[0088] In any embodiment, the mass percentage of the molten salt electrolyte in the electrolyte is 80% - 90%, and the mass percentage of the organic solvent in the electrolyte is 10% - 20%. Thus, the main component in the electrolyte is the molten salt electrolyte, and the molten salt electrolyte is not easily decomposed under high temperature and high pressure, having better stability, thereby improving the cycling performance of the battery. The mass percentage of the molten salt electrolyte in the electrolyte can be 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, and the mass percentage of the organic solvent in the electrolyte can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%.

[0089] The second aspect of the present application provides a battery, including: a positive electrode plate, a negative electrode plate, a separator, and the electrolyte of the first aspect of the present application.

[0090] In any embodiment, the battery includes a lithium-ion battery or a sodium-ion battery.

[0091] In the third aspect, an embodiment of the present application provides a method for preparing a battery. The preparation method includes a liquid injection step, and the liquid injection step includes: injecting the electrolyte of the first aspect of the present application under the condition of being higher than the melting point of the molten salt electrolyte. Thus, the molten salt electrolyte, which is in a solid state under standard temperature and atmospheric pressure, can be injected in the form of a liquid molten state, making the preparation of the battery more convenient.

[0092] In any embodiment, the preparation method further includes a formation step. After the liquid injection step, a formation treatment is performed under the condition of being higher than the melting point of the molten salt electrolyte in the electrolyte. The molten salt electrolyte, which is in a solid state under standard temperature and atmospheric pressure, is subjected to a formation treatment in the form of a liquid molten state to activate the battery.

[0093] A fourth aspect of the present application provides an electrical device, which includes the battery of the second aspect of the present application.

[0094] In any implementation, the battery includes a lithium-ion battery or a sodium-ion battery.

[0095] In addition, the secondary battery, battery module, battery pack, and electrical device of the present application will be described below with appropriate reference to the drawings.

[0096] In one implementation of the present application, a secondary battery is provided.

[0097] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0098] 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 includes the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the preparation method of the positive electrode material of the second aspect of the present application.

[0099] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0100] In some implementations, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0101] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material can be the positive electrode active material for lithium-ion batteries well known in the art. As an example, the positive electrode active material can include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides can include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of their modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure can include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0102] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0103] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an 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.

[0104] In some embodiments, the positive electrode plate can be prepared in the following manner: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0105] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0106] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0107] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] In some embodiments, the negative electrode active material can be the negative electrode active material for batteries known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0109] In some embodiments, the negative electrode film layer may optionally further include a binder. The binder can 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).

[0110] In some embodiments, the negative electrode film layer may optionally further include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In some embodiments, the negative electrode film layer may optionally further include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0112] In some embodiments, the negative electrode plate can be prepared in the following manner: Dispersing the components for preparing the negative electrode plate described above, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; Coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0113] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific limitation on the type of electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid.

[0114] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0115] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium difluoro bis(oxalate) phosphate, and lithium tetrafluorooxalate phosphate.

[0116] In some embodiments, the solvent may be selected from 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, methyl ethyl sulfone, and diethyl sulfone.

[0117] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

[0118] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0119] In some embodiments, the material of the separator may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0120] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly by a winding process or a stacking process.

[0121] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0122] In some embodiments, the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic, and examples of the plastic may include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0123] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a secondary battery 5 with a square structure as an example.

[0124] In some embodiments, with reference to Figure 2, the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0125] In some embodiments, the secondary battery can be assembled into a battery module. The number of secondary batteries included in the battery module can 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.

[0126] Figure 3 is a battery module 4 as an example. Refer to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0127] Optionally, the battery module 4 may further include a housing having a receiving space, and a plurality of secondary batteries 5 are received in the receiving space.

[0128] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can 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 pack.

[0129] Figure 4 and Figure 5 is a battery pack 1 as an example. Refer to Figure 4 and Figure 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 and form a closed space for receiving the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0130] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0131] As the electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0132] Figure 6 Take an electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or battery module can be adopted.

[0133] Another example of the device can be a mobile phone, tablet computer, laptop, etc. This device usually requires being thin and light, and a secondary battery can be used as the power source.

[0134] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0135] Embodiment 1

[0136] 1) Preparation of the electrolyte: Lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide are mixed in a mass ratio of 1:1 to obtain an electrolyte molten salt. Biphenyl is added to the electrolyte molten salt and mixed evenly to obtain an electrolyte solution, and the mass ratio of the electrolyte molten salt in the electrolyte solution is 80%, and the mass ratio of biphenyl in the electrolyte solution is 20%.

[0137] 2) Preparation of the positive electrode plate: Nickel cobalt manganese (NCM) material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 96:2:2, and then N-methylpyrrolidone (NMP) is added and stirred evenly to obtain a positive electrode slurry with a solid content of 60%; then the positive electrode slurry is evenly coated on the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode plate is obtained.

[0138] 3) Preparation of the negative electrode sheet: The active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water as the solvent in a weight ratio of 96:2:1:1, and after mixing evenly, a negative electrode slurry is prepared; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil once or multiple times, and after drying, cold pressing, and slitting, the negative electrode sheet is obtained.

[0139] 4) The separator is a polypropylene film.

[0140] 5) Preparation of the battery: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, so that the separator is between the positive and negative electrode sheets to play a role in isolation, and then wound to obtain a bare battery core. The bare battery core is welded with pole ears, and the bare battery core is placed in an aluminum shell, and dried at 110 °C for 6 h to remove water. The electrolyte is heated to 90 °C, and the electrolyte is injected and sealed at 90 °C to obtain a non-charged battery. The non-charged battery is then successively subjected to processes such as standing, hot and cold pressing, formation, shaping, and capacity testing to obtain the battery product. The formation step is carried out at 90 °C.

[0141] Examples 2-28 are basically the same as Example 1, and the differences can be seen in the parameters listed in Table 1.

[0142] Comparative Example 1

[0143] It is basically the same as Example 1, except that the preparation steps of the electrolyte are different. Specifically, the preparation of the electrolyte is carried out in a glove box under an argon atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) are mixed evenly in a volume ratio of 3 / 7, LiPF6 lithium salt is added and dissolved in the organic solvent, and stirred evenly to prepare a 1 M LiPF6 EC / EMC solution to obtain the electrolyte.

[0144] Comparative Example 2

[0145] It is basically the same as Example 1, except that the preparation steps of the electrolyte are different. Specifically, the preparation of the electrolyte is to mix lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide in a mass ratio of 1:1 to obtain an electrolyte molten salt to obtain the electrolyte.

[0146] Characterization and testing:

[0147] The electrode sheets or lithium-ion batteries prepared in the above-mentioned examples and comparative examples are subjected to the following characterization and testing:

[0148] 1. Melting point test of the molten salt electrolyte in the electrolyte

[0149] The test is carried out using a WRR melting point instrument. Specifically:

[0150] Place the samples prepared in the examples or comparative examples in a porcelain mortar, and grind them into fine powders to obtain uniform samples. Take a clean and dry melting point tube, insert its open end into the sample, and load the sample. Take a dry glass tube about 0.8 m long, stand it upright on a glass plate, and drop the melting point tube containing the sample into it at least 20 times to compact the sample in the melting point tube to a height of 3 - 4 mm. If two samples are measured simultaneously for comparison, the heights of the samples should be the same to ensure the consistency of the measurement results. Seal the other end of the melting point tube.

[0151] Turn on the power switch of the melting point instrument. After preheating for 10 min, set the starting temperature to 30 °C and the heating rate to 10 °C / min. Then insert the melting point tube into the sample socket. After maintaining for 3 - 5 min, press the "heating" button to start the measurement, and the melting curve will be displayed on the instrument panel. Read the initial melting temperature and the final melting temperature according to the melting curve.

[0152] 2. Battery cycle performance test

[0153] 90 °C cycle: At 90 °C, charge the lithium-ion batteries prepared in the examples and comparative examples at a constant current of 1 / 3C until the voltage reaches 4.3V, then charge at a constant voltage of 4.3V until the current reaches 0.05C, let it stand for 5 minutes, and then discharge at 1 / 3C until the voltage reaches 2.8V. The obtained capacity is recorded as the initial capacity C0. Then place the battery in a 90 °C high and low temperature chamber, and perform cyclic charge and discharge after thermal equilibrium. The process is the same as the process of measuring the capacity at 90 °C. Until the capacity of the lithium-ion battery decays to 80% of the initial capacity, record the number of cycles.

[0154] Table 1

[0155]

[0156]

[0157] As can be seen from Table 1, through Examples 1 to 28 and Comparative Example 1, compared with the electrolyte prepared by dissolving lithium salts in organic solvents in Comparative Example 1, the melting point of the molten salt electrolyte used in the electrolytes of Examples 1 to 28 of the present application is between 80 - 90 °C. Applying it to the battery can make the working temperature range of the battery wider and can be applicable to environments above the melting point of the molten salt electrolyte. The battery using the molten salt electrolyte and organic solvent as the electrolyte has more cycles when the capacity decays to 80% under the cyclic test conditions of 90 °C and 4.3V, and the cycle performance of the battery is better.

[0158] As can be seen from Examples 1-6, the use of two molten salt electrolytes in the electrolyte can effectively increase the number of cycles when the high capacity decays to 80%, improving the cycle performance of the battery. The mass ratio of each molten salt electrolyte in the two molten salt electrolytes is 40%-60%, which can form a low eutectic point and effectively increase the number of cycles when the capacity decays to 80%, improving the cycle performance of the battery.

[0159] As can be seen from Examples 7-13, the use of three molten salt electrolytes in the electrolyte can effectively increase the number of cycles when the capacity decays to 80%, improving the cycle performance of the battery. The mass ratio of each molten salt electrolyte in the three molten salt electrolytes is 10%-80%, which can form a low eutectic point and effectively increase the number of cycles when the capacity decays to 80%, improving the cycle performance of the battery.

[0160] As can be seen from Examples 1, 14-16, the electrolyte composed of molten salt electrolyte and organic solvent in different ratios applied to the battery has good cycle performance and a large number of cycles when the capacity decays to 80%.

[0161] As can be seen from Examples 1, 17-24, when different single organic solvents are used in the electrolyte, the batteries all have good cycle performance and a large number of cycles when the capacity decays to 80%.

[0162] As can be seen from Examples 25-28, when two different ratios of organic solvents are used in the electrolyte, the batteries all have good cycle performance and a large number of cycles when the capacity decays to 80%.

[0163] As can be seen from Examples 1-28 and Comparative Example 2, compared with the method in Comparative Example 2 where only molten salt electrolyte is used in the electrolyte without adding organic solvent, the presence of organic solvent in the electrolyte of the embodiments of the present application can compensate for the problem of poor toughness of the inorganic SEI film, effectively increase the number of cycles when the capacity decays to 80%, and improve the cycle performance of the battery.

[0164] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same constitution and the same effect as the technical idea within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: Includes molten salt electrolyte and organic solvent.

2. The electrolyte according to claim 1, characterized in that The molten salt electrolyte includes at least two molten salts.

3. The electrolyte according to claim 1, characterized in that At least one molten salt in the molten salt electrolyte includes metal cations and fluorine-containing organic anions.

4. The electrolyte according to claim 3, characterized in that The metal cations of at least one molten salt in the molten salt electrolyte include lithium ions.

5. The electrolyte according to claim 3 or 4, characterized in that The metal cations also include at least one of potassium ions, rubidium ions, cesium ions, francium ions, magnesium ions, calcium ions, strontium ions, and barium ions.

6. The electrolyte according to any one of claims 3 to 5, characterized in that: The fluorine-containing organic anion includes at least one of a bis(fluorosulfonyl)imide ion, a bis(trifluoromethanesulfonyl)imide ion, and a bis(pentafluoroethylsulfonyl)imino ion.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The molten salt electrolyte includes two molten salts; optionally, at least one of the two molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide or lithium bis(pentafluoroethylsulfonyl)imide; optionally, one of the two molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide or rubidium bis(pentafluoroethylsulfonyl)imide.

8. The electrolyte according to claim 7, characterized in that The mass proportion of each of the two molten salts in the molten salt electrolyte is 40%-60%.

9. The electrolyte according to any one of claims 1 to 6, characterized in that: The molten salt electrolyte includes three molten salts; optionally, at least one of the three molten salts includes lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide or lithium bis(pentafluoroethylsulfonyl)imide; optionally, at least one of the three molten salts includes sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, cesium bis(trifluoromethanesulfonyl)imide, rubidium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide or rubidium bis(pentafluoroethylsulfonyl)imide.

10. The electrolyte according to claim 9, characterized in that The mass proportion of each of the three molten salts in the molten salt electrolyte is 10%-80%.

11. The electrolyte according to any one of claims 1 to 10, characterized in that: The organic solvent includes a saturated alkane having 20 or more carbon atoms.

12. The electrolyte according to any one of claims 1 to 10, characterized in that: The organic solvent includes a compound having a structure shown in Formula I: Among them, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, or a substituted or unsubstituted biphenyl group.

13. The electrolyte according to any one of claims 1 to 10, characterized in that: The organic solvent includes a saturated alkane having a carbon number greater than or equal to 20 and a compound having a structure shown in Formula I: Among them, R1-R6 are each independently selected from a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a carbonyl group, a substituted or unsubstituted C1-C12 alkyl group, a substituted or unsubstituted C2-C12 alkenyl group, a substituted or unsubstituted C2-C12 alkynyl group, a substituted or unsubstituted C3-C8 cycloalkyl group, a substituted or unsubstituted C5-C6 aryl group, or a substituted or unsubstituted biphenyl group.

14. The electrolyte according to claim 11 or 13, characterized in that: The number of carbon atoms of the saturated alkane is n, 20≤n≤60; optionally, the saturated alkane with a carbon number greater than or equal to 20 includes at least one of eicosane, docosane, hexacosane, tetracosane and hexacosane.

15. The electrolyte according to claim 12 or 13, characterized in that: The compound having the structure shown in Formula I includes at least one of benzene, biphenyl, p-xylene, m-xylene, diphenyl ether and benzoquinone.

16. The electrolyte according to claim 13, characterized in that The mass ratio between the saturated alkane having carbon atoms greater than or equal to 20 and the compound having the structure shown in formula I is (1-3): (1-3).

17. The electrolyte according to any one of claims 1 to 16, characterized in that: The mass proportion of the molten salt electrolyte in the electrolyte is 80% to 90%, and / or the mass proportion of the organic solvent in the electrolyte is 10% to 20%.

18. A battery, characterized in that: include: A positive electrode sheet, a negative electrode sheet, a separator and an electrolyte as claimed in any one of claims 1 to 17.

19. The battery according to claim 18, characterized in that The battery includes a lithium ion battery or a sodium ion battery.

20. A method for preparing a battery, comprising a liquid injection step, characterized in that: The injection step comprises: injecting the electrolyte according to any one of claims 1 to 17 under a condition where the melting point is higher than that of the molten salt electrolyte.

21. The preparation method according to claim 20, further comprising a chemical formation step, characterized in that: After the injection step, a chemical formation treatment is performed under conditions higher than the melting point of the molten salt electrolyte in the electrolyte.

22. An electrical device, characterized in that: The electrical device comprises the battery as claimed in claim 18 or 19.

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