A lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device

Abstract

The present application provides a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device, belonging to the field of secondary battery manufacturing. The lithium-ion battery electrolyte includes an organic solvent, a lithium salt, and an additive. The additive includes a tributylstannane compound having a structural general formula shown in Formula I and / or Formula II. By means of this lithium-ion battery electrolyte, the problem of poor cycle performance existing in the application of the lithium-ion battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of secondary battery manufacturing, and more particularly, to a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device using the same. Background Art

[0002] In the prior art, as the applied voltage gradually increases (especially under application conditions where the voltage is higher than 4V), current lithium-ion batteries generally have poor cycling performance, which limits the application of lithium-ion batteries. Summary of the Invention

[0003] An object of the present application is to provide a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device using the same, which can improve the poor cycling performance of lithium-ion batteries during application.

[0004] The embodiments of the present application are implemented as follows:

[0005] In a first aspect, an embodiment of the present application provides a lithium-ion battery electrolyte, which includes an organic solvent, a lithium salt, and an additive. The additive includes a tributylstannane compound having a structural general formula shown in Formula I and / or Formula II:

[0006]

[0007]

[0008] Wherein, R1 is independently selected from any one of a fluorine-substituted or unsubstituted C2-C6 alkenyl group, a fluorine-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group; R2 is independently selected from any one of a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a fluorine-substituted or unsubstituted C2-C6 alkenyl group, a fluorine-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group.

[0009] In the above technical solution, by adding a film-forming additive of tributylstannane compound to the electrolyte, on the one hand, the unsaturated bonds therein can form a dense protective film on the positive and negative electrodes. Among them, a dense metal oxide coating layer is formed by oxidation on the surface of the positive electrode, and a dense organotin polymer coating layer is formed by reduction on the negative electrode. Through the combined action of the two dense coating layers, the risk of the positive and negative electrode materials contacting the electrolyte and undergoing side reactions can be effectively reduced, especially at high voltages (side reactions are usually more intense at high voltages), thereby playing a role in protecting the positive and negative electrodes of the battery, and further improving the cycle performance of the lithium-ion battery; on the other hand, since the metal element tin is introduced into the film-forming additive of tributylstannane compound, it can increase the electrochemical stability of the battery during application, thereby achieving the purpose of assisting in improving the cycle performance of the battery. Compared with the existing positive and negative electrode protection methods (usually forming a coating layer on the surface of the positive and negative electrodes by physical mixing, and the formed dot-like coating layer is difficult to effectively protect the positive and negative electrodes, resulting in poor cycle performance of the battery), the film-forming additive of tributylstannane compound provided in the embodiment of the present application can form a dense protective film on the surface of the positive and negative electrodes, and moreover, the introduced metal element tin can also assist in improving the electrochemical stability of the battery, thereby being able to improve the problem of poor cycle performance existing in the lithium-ion battery during application.

[0010] In some alternative embodiments, the additive includes at least one of the following compound structures:

[0011]

[0012] Using the tributylstannane compound with the above specific structure as the additive, compared with using compounds with other structures as additives, due to having an appropriate carbon chain length and being able to better match the components in the electrolyte, it can better improve the cycle performance of the battery.

[0013] In some alternative embodiments, the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.1-5%;

[0014] Optionally, the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.3-3%.

[0015] In the above technical solution, limiting the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte within a specific range is because: on the one hand, there is a sufficient amount of tributylstannane compound, which is beneficial to generating a protective film with an appropriate thickness and relatively dense; on the other hand, the upper limit is below a certain standard. Compared with the case where the protective film is too thick (excessive tributylstannane compound will cause the generated protective film to be too thick), it can reduce the influence of the protective film on the proton transport efficiency, thereby being beneficial to maintaining better electrical performance. At the same time, it can also make the additive have a higher utilization rate.

[0016] Furthermore, limiting the mass percentage of tributylstannane compounds in the lithium-ion battery electrolyte within a more preferable range can better balance the lower economic cost while effectively improving the battery cycle performance.

[0017] In some alternative embodiments, the additive further includes an auxiliary additive, and the auxiliary additive includes at least one of 1,3-propane sultone, 1,4-butane sultone, allyl 1,3-sulfonic acid lactone, vinylene sulfate, methylene methanedisulfonate, vinylene carbonate, fluoroethylene carbonate, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium difluorophosphate, lithium tetrafluoro(oxalato)phosphate, difluoropyridine, hexamethylene diisocyanate, and triallyl isocyanurate;

[0018] Optionally, the mass percentage of the additive in the lithium-ion battery electrolyte is 2-10%.

[0019] In the above technical solution, adding an auxiliary additive to the additive can endow the electrolyte with more abundant functions, so as to more comprehensively improve the comprehensive electrical performance of the battery. At the same time, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various auxiliary additive systems, and can provide more feasible implementation solutions, thus facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0020] Furthermore, limiting the mass percentage of the additive in the lithium-ion battery electrolyte within a specific range can balance the lower economic cost while effectively improving the comprehensive electrical performance of the battery.

[0021] In some alternative embodiments, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, fluoroethyl methyl carbonate, and ethyl difluoroacetate.

[0022] The technical solution provided by the embodiments of the present application is applicable to the above-mentioned various organic solvent systems, and can provide more feasible implementation solutions, thus facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0023] In some alternative embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide;

[0024] Optionally, the mass percentage of the lithium salt in the lithium-ion battery electrolyte is 12-18%.

[0025] The technical solution provided by the embodiments of the present application is applicable to the above-mentioned various lithium salt systems, and can provide more feasible implementation solutions, thus facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0026] Furthermore, limiting the mass percentage of the lithium salt in the lithium-ion battery electrolyte within a specific range can enable the lithium salt to have an appropriate mass proportion, so that the corresponding battery has better charge and discharge performance.

[0027] In a second aspect, an embodiment of the present application provides a lithium-ion battery, including a housing, an electrode assembly, and a lithium-ion battery electrolyte provided in the embodiment of the first aspect. The electrode assembly is accommodated in the housing; the lithium-ion battery electrolyte is accommodated in the housing.

[0028] In the above technical solution, the lithium-ion battery includes the lithium-ion battery electrolyte provided in the embodiment of the first aspect. Since the film-forming additive of tributylstannane compounds in the electrolyte can form a dense protective film on the surfaces of both the positive and negative electrodes simultaneously, and the introduced metal element tin can also assist in improving the electrochemical stability of the battery, the problem of poor cycling performance in the application process of the lithium-ion battery can be improved.

[0029] In some alternative embodiments, in the battery positive electrode of the electrode assembly, the positive electrode active material includes at least one of transition metal phosphates, lithium salts of transition metal oxides, lithium titanate, and transition metal sulfides;

[0030] Optionally, the positive electrode active material includes at least one of lithium nickel manganate, lithium nickel cobalt manganate, and lithium cobaltate.

[0031] The technical solution provided by the embodiment of the present application is applicable to the above-mentioned various positive electrode active material systems, can provide more feasible implementation solutions, and thus facilitates the popularization and application of the technical solution provided by the embodiment of the present application.

[0032] Furthermore, limiting the types of the positive electrode active material within a more preferred range is because the positive electrode active materials of the above system are more suitable for high-voltage application conditions, and can enable the corresponding battery to have better comprehensive electrical properties compared with using other types of positive electrode active material systems.

[0033] In some alternative embodiments, in the battery negative electrode of the electrode assembly, the negative electrode active material includes at least one of metallic lithium, graphite, soft carbon, hard carbon, silicon, silicon oxide compounds, and silicon-carbon composites.

[0034] In the above technical solution, the technical solution provided by the embodiment of the present application is applicable to the above-mentioned various negative electrode active material systems, can provide more feasible implementation solutions, and thus facilitates the popularization and application of the technical solution provided by the embodiment of the present application.

[0035] In a third aspect, an embodiment of the present application provides an electrical device, and the electrical device includes the lithium-ion battery provided in the embodiment of the second aspect. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0037] It should be noted that the "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases where it can be "feature 1" alone, "feature 2" alone, or "feature 1" plus "feature 2".

[0038] In addition, in the description of this application, unless otherwise specified, the meaning of "multiple" in "one or more" refers to two or more; the range of "numerical value a to numerical value b" includes the two end values "a" and "b", and the "measurement unit" in "numerical value a to numerical value b + measurement unit" represents the "measurement unit" of both "numerical value a" and "numerical value b".

[0039] In the prior art, as the demand for the energy density of batteries increases, the applied voltage of the battery also increases accordingly. The increase in the applied voltage will then lead to an intensification of the side reaction between the positive electrode of the battery and the electrolyte, thereby affecting the cycle performance of the battery. Currently, the commonly adopted solution is to form a coating layer on the surfaces of the positive and negative electrodes by means of physical mixing. However, the coating layer formed in this way is a dot-shaped coating layer, which is difficult to effectively protect the positive and negative electrodes of the battery and still results in poor cycle performance of the battery.

[0040] Based on this, the inventors have studied and found that based on the existing electrolyte composition system, by adding a tributylstannane compound film-forming additive to the electrolyte, it can simultaneously form a dense protective film on the surfaces of the positive and negative electrodes, and moreover, the introduced metal element tin can also assist in improving the electrochemical stability of the battery, thereby being able to solve the problem of poor cycle performance existing in the application process of lithium-ion batteries.

[0041] The following specifically describes a lithium-ion battery electrolyte, a lithium-ion battery, and an electrical device according to the embodiments of this application.

[0042] In a first aspect, the embodiments of this application provide a lithium-ion battery electrolyte, including an organic solvent, a lithium salt, and an additive, and the additive includes a tributylstannane compound having a structural general formula shown in Formula I and / or Formula II:

[0043]

[0044] Among them, R1 is independently selected from any one of a fluoro-substituted or unsubstituted C2-C6 alkenyl group, a fluoro-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group, and R2 is independently selected from any one of a fluoro-substituted or unsubstituted C1-C6 linear alkyl group, a fluoro-substituted or unsubstituted C2-C6 alkenyl group, a fluoro-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group.

[0045] In this application, by adding a tributylstannane compound film-forming additive to the electrolyte, on the one hand, the unsaturated bonds therein can form a dense protective film on the positive and negative electrodes. Among them, a dense metal oxide coating layer is formed by oxidation on the surface of the positive electrode, and a dense organotin polymer coating layer is formed by reduction on the negative electrode. Through the combined action of the two dense coating layers, the risk of the positive and negative electrode materials coming into contact with the electrolyte and undergoing side reactions can be effectively reduced, especially at high voltages (where side reactions are usually more intense), thereby playing a role in protecting the positive and negative electrodes of the battery and further improving the cycle performance of the lithium-ion battery; on the other hand, since the metal element tin is introduced into the tributylstannane compound film-forming additive, it can increase the electrochemical stability of the battery during application, thereby achieving the purpose of assisting in improving the cycle performance of the battery. Compared with the existing positive and negative electrode protection methods (usually forming a coating layer on the surface of the positive and negative electrodes by physical mixing, and the formed dot-like coating layer is difficult to effectively protect the positive and negative electrodes, resulting in poor cycle performance of the battery), the tributylstannane compound film-forming additive provided in the embodiments of this application can form a dense protective film on the surface of the positive and negative electrodes, and moreover, the introduced metal element tin can also assist in improving the electrochemical stability of the battery, thereby being able to solve the problem of poor cycle performance existing in the lithium-ion battery during application.

[0046] As an example, the additive includes at least one of the following compound structures:

[0047]

[0048] In this embodiment, using the tributylstannane compound with the above specific structure as the additive, compared with using compounds with other structures as additives, due to having an appropriate carbon chain length and being able to better match the components in the electrolyte, it can better improve the cycle performance of the battery.

[0049] It should be noted that the mass ratio of the tributylstannane compound in the electrolyte is not limited and can be adjusted according to actual needs.

[0050] As an example, the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.1-5%, such as but not limited to any one of the point values of 0.1%, 0.5%, 1%, 2%, 3%, 4%, and 5% or the range values between any two of them.

[0051] Optionally, the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.3-3%, such as but not limited to any one of the point values of 0.3%, 0.4%, 0.5%, 1%, 2% and 3 or the range values between any two of them.

[0052] In this embodiment, limiting the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte within a specific range is due to: on the one hand, having a sufficient amount of the tributylstannane compound is beneficial to forming a protective film with a suitable thickness and relatively dense structure; on the other hand, with the upper limit below a certain standard, compared with the case of an overly thick protective film (excessive tributylstannane compound will cause the formed protective film to be overly thick), it can reduce the influence of the protective film on the proton transport efficiency, thereby being beneficial to maintaining better electrical properties. At the same time, it can also make the additive have a higher utilization rate.

[0053] Furthermore, limiting the mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte within a more preferred range can better balance the lower economic cost while effectively improving the battery cycle performance.

[0054] As an example, the additive further includes an auxiliary additive, and the auxiliary additive includes at least one of 1,3-propane sultone, 1,4-butane sultone, allyl 1,3-sulfonic acid lactone, vinylene sulfate, methylene methanedisulfonate, vinylene carbonate, fluoroethylene carbonate, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium difluorophosphate, lithium tetrafluoro(oxalato)phosphate, difluoropyridine, hexamethylene diisocyanate and triallyl isocyanurate.

[0055] Optionally, the mass percentage of the additive in the lithium-ion battery electrolyte is 2-10%, such as but not limited to any one of the point values of 2%, 4%, 6%, 8% and 10% or the range values between any two of them.

[0056] In this embodiment, adding the auxiliary additive to the additive can endow the electrolyte with more abundant functions, so as to more comprehensively improve the comprehensive electrical properties of the battery. At the same time, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various auxiliary additive systems, and can provide more implementation schemes, thereby facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0057] Furthermore, limiting the mass percentage of the additive in the lithium-ion battery electrolyte within a specific range can balance the lower economic cost while effectively improving the comprehensive electrical properties of the battery.

[0058] It should be noted that the types of organic solvents are not limited and can be set according to the conventional selection in the art.

[0059] As an example, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, fluoroethyl methyl carbonate, and ethyl difluoroacetate.

[0060] In this embodiment, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various organic solvent systems, and can provide more feasible implementation solutions, thereby facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0061] It should be noted that the types of lithium salts are not limited and can be set according to the conventional selection in the art.

[0062] As an example, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0063] Optionally, the mass percentage of the lithium salt in the lithium ion battery electrolyte is 12-18%, for example but not limited to any one of the point values of 12%, 13%, 14%, 15%, 16%, 17%, and 18% or the range values between any two of them.

[0064] In this embodiment, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various lithium salt systems, and can provide more feasible implementation solutions, thereby facilitating the popularization and application of the technical solution provided by the embodiments of the present application.

[0065] Furthermore, limiting the mass percentage of the lithium salt in the lithium ion battery electrolyte within a specific range can make the lithium salt have an appropriate mass ratio, so that the corresponding battery has good charge and discharge performance.

[0066] It should be noted that for the components in the electrolyte that are not specifically described and their mass percentages in the electrolyte are not limited, and can be set according to the conventional selection in the art.

[0067] In a second aspect, the embodiments of the present application provide a lithium ion battery, including a housing, an electrode assembly, and a lithium ion battery electrolyte as provided in the embodiments of the first aspect. The electrode assembly is accommodated in the housing; the lithium ion battery electrolyte is accommodated in the housing.

[0068] In this embodiment, the lithium-ion battery includes the lithium-ion battery electrolyte provided in the embodiments of the first aspect. Since the film-forming additive of tributylstannane compound in the electrolyte can form a dense protective film on the surfaces of both the positive and negative electrodes simultaneously, and the introduced metal element tin can also assist in improving the electrochemical stability of the battery, the problem of poor cycling performance in the application of the lithium-ion battery can be improved.

[0069] It should be noted that the type of the positive electrode active material in the battery positive electrode is not limited and can be set according to the conventional selection in the art.

[0070] As an example, in the battery positive electrode of the electrode assembly, the positive electrode active material includes at least one of transition metal phosphates, lithium salts of transition metal oxides, lithium titanate, and transition metal sulfides.

[0071] Optionally, the positive electrode active material includes at least one of lithium nickel manganate, lithium nickel cobalt manganate, and lithium cobaltate.

[0072] In this embodiment, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various positive electrode active material systems, can provide more implementable solutions, and thus facilitates the popularization and application of the technical solution provided by the embodiments of the present application.

[0073] Furthermore, limiting the type of the positive electrode active material within a more preferable range is because the positive electrode active materials of the above-mentioned systems are more suitable for high-voltage application conditions, and can enable the corresponding battery to have better comprehensive electrical properties compared with using other types of positive electrode active material systems.

[0074] It should be noted that the type of the negative electrode active material in the battery negative electrode is not limited and can be set according to the conventional selection in the art.

[0075] As an example, in the battery negative electrode of the electrode assembly, the negative electrode active material includes at least one of metallic lithium, graphite, soft carbon, hard carbon, silicon, silicon oxide compound, and silicon-carbon composite.

[0076] In this embodiment, the technical solution provided by the embodiments of the present application is applicable to the above-mentioned various negative electrode active material systems, can provide more implementable solutions, and thus facilitates the popularization and application of the technical solution provided by the embodiments of the present application.

[0077] It should be noted that for the structural or functional units in the lithium-ion battery that are not specifically described, there are no limitations and they can be set according to the conventional selection in the art.

[0078] In the third aspect, the embodiments of the present application provide an electrical device, and the electrical device includes the lithium-ion battery provided in the embodiments of the second aspect.

[0079] It should be noted that the type of the electrical equipment is not limited, such as mobile phones, portable devices, laptop computers, battery cars, electric vehicles, ships, spacecrafts, electric toys, energy storage devices, electric tools, etc.

[0080] The features and performance of the present application will be further described in detail below in conjunction with embodiments.

[0081] Embodiment 1

[0082] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, including the following steps:

[0083] Mix ethylene carbonate (EC) and ethyl methyl fluorocarbonate (FEMC) according to a mass ratio of 2:8 to obtain an organic solvent; then, add Compound 1 and LiPF6 to the organic solvent, wherein the mass percentages of the organic solvent, Compound 1 and LiPF6 are 84:1:15 in sequence.

[0084] Embodiment 2

[0085] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that 1% of Compound 1 is replaced by 1% of Compound 2.

[0086] Embodiment 3

[0087] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that 1% of Compound 1 is replaced by 1% of Compound 3.

[0088] Embodiment 4

[0089] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that 1% of Compound 1 is replaced by 1% of Compound 4.

[0090] Embodiment 5

[0091] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that 1% of Compound 1 is replaced by 1% of Compound 5.

[0092] Embodiment 6

[0093] The embodiment of the present application provides a preparation method of a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that 1% of Compound 1 is replaced by 1% of Compound 6.

[0094] Embodiment 7

[0095] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 0.5% of Compound 1 and 0.5% of Compound 2.

[0096] Example 8

[0097] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 0.25% of Compound 1, 0.25% of Compound 2, 0.25% of Compound 3, and 0.25% of Compound 4.

[0098] Example 9

[0099] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 1% of Compound 7.

[0100]

[0101] Example 10

[0102] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 1% of Compound 8.

[0103]

[0104] Example 11

[0105] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 0.1% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0106] Example 12

[0107] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 5% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0108] Example 13

[0109] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced with 0.3% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0110] Example 14

[0111] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced by 3% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0112] Example 15

[0113] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced by 0.05% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0114] Example 16

[0115] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced by 8% of Compound 1, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0116] Example 17

[0117] An embodiment of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: 1% of Compound 1 is replaced by 1% of Compound 1 and 1% of 1,3-propane sultone (PS), and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0118] Comparative Example 1

[0119] A comparative example of the present application provides a method for preparing a lithium-ion battery electrolyte, which is only different from Embodiment 1 in that: Compound 1 is not added, and the change in dosage is correspondingly adjusted by the amount of the mixed organic solvent.

[0120] For ease of understanding the technical solution, the electrolyte components of Examples 1 to 17 and Comparative Example 1 are described in the following table.

[0121] It should be noted that the mass percentage of the mixed organic solvent is equal to the remaining value obtained by subtracting the mass percentages of the additive and the lithium salt from 100.

[0122] Table 1 Component Table

[0123]

[0124] Test Example 1

[0125] Battery Performance Test

[0126] Test Method:

[0127] The lithium-ion battery electrolytes prepared in Examples 1 to 17 and Comparative Example 1 were assembled into batteries and numbered correspondingly. Then, the capacity retention rates of the batteries after 300 cycles at 25°C and 45°C, as well as the capacity retention rate, capacity recovery rate, and thickness expansion rate after storage at 60°C for 7 days were tested respectively.

[0128] Among them,

[0129] The battery was assembled according to the following method:

[0130] S1 Mix LiNi 0.5 Mn 1.5 O4 (cathode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (binder) in a mass ratio of 96.5:2.0:1.5 and disperse them in N-methyl-2-pyrrolidone to obtain a cathode slurry; then, coat the cathode slurry evenly on both sides of the aluminum foil; then, successively go through drying, calendaring, and vacuum drying, and weld the aluminum lead wire with an ultrasonic welder to obtain a cathode plate with a thickness of 115 μm.

[0131] S2 Mix graphite (anode active material), conductive carbon black (conductive agent), styrene-butadiene rubber, and carboxymethyl cellulose (binder) in a mass ratio of 96:2:2:2, disperse them in deionized water to obtain an anode slurry; then, coat the anode slurry on both sides of the copper foil; then, successively go through drying, calendaring, and vacuum drying, and weld the nickel lead wire with an ultrasonic welder to obtain an anode plate with a thickness of 165 μm.

[0132] S3 Wind the prepared cathode plate, anode plate, and ion separator (a 16-μm-thick PE ceramic separator) to prepare a bare battery cell, and then assemble the bare battery cell, the housing, and the lithium-ion battery electrolytes prepared in Examples 1 to 17 and Comparative Example 1 into a battery.

[0133] The tests of the corresponding electrical parameters of the battery and the corresponding calculation formulas are as follows:

[0134] Test of the capacity retention rate of the battery after 300 cycles at 25°C: Place the lithium-ion battery at room temperature, and then perform 300 charge-discharge cycles on the lithium-ion battery at a current of 0.33C. The test voltage window is 3.0 to 4.9V, and record the discharge retention capacity of the 300th cycle.

[0135] Test of the capacity retention rate of the battery after 300 cycles at 45°C: Place the lithium-ion battery in a 45°C constant temperature oven and let it stand for 4 h, and then perform 300 charge-discharge cycles on the lithium-ion battery at a current of 0.33C. The test voltage window is 3.0 to 4.9V, and record the discharge retention capacity of the 300th cycle.

[0136] Battery thickness expansion rate, capacity retention, and capacity recovery tests at 60°C for 7 days: Test and record the initial thickness and initial 0.33C discharge capacity of the lithium-ion battery; then charge the battery at a constant current and constant voltage of 0.33C to 4.9V, place it in an explosion-proof oven at 60°C, test the thermal measurement thickness of the battery in the oven after 7 days of storage, then take out the battery and cool it to room temperature, and test its discharge retention capacity and recovery capacity when discharging at 0.33C to 3.0V.

[0137] The calculation formulas are as follows:

[0138] Capacity retention rate after 300 cycles (%) = (Discharge retention capacity at the 300th cycle / Discharge capacity at the first cycle) × 100%;

[0139] Storage capacity retention rate (%) = Retention capacity / Initial capacity × 100%;

[0140] Capacity recovery rate (%) = Recovery capacity / Initial capacity × 100%;

[0141] Thickness expansion rate (%) = (Thermal measurement thickness - Initial thickness) / Initial thickness × 100%.

[0142] Table 2 Test results of electrical properties

[0143]

[0144]

[0145] Referring to Table 2, from the test results of Examples 1 to 8 and Comparative Example 1, it can be seen that when the electrolyte contains one or more tributylstannane compounds provided in the examples of the present application, compared with the case where no tributylstannane compound is added, the cycle performance of the corresponding battery can be improved.

[0146] From the test results of Example 1 and Examples 9 to 10, it can be seen that when using tributylstannane compounds with a more preferred structure, compared with not using tributylstannane compounds with a more preferred structure, the corresponding battery of the former has better cycle performance.

[0147] From the test results of Examples 11 to 12 and Examples 15 and 16, it can be seen that when the mass ratio of the tributylstannane compound is within the preferred range, compared with not being within the preferred range, the corresponding battery of the former has better cycle performance.

[0148] From the test results of Examples 11 to 12 and Examples 13 and 14, it can be seen that when the mass ratio of the tributylstannane compound is within a more preferred specific range, compared with not being within the more preferred range, the corresponding battery of the former has better cycle performance.

[0149] As can be seen from the test results of Example 1 and Example 17, when an auxiliary additive is additionally added to the additive, compared with the case where no auxiliary additive is added, the battery corresponding to the former has better cycling performance.

[0150] The embodiments described above are some, but not all, of the embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

Claims

1. A lithium-ion battery electrolyte, characterized in that, It includes an organic solvent, a lithium salt and an additive. The additive includes a tributylstannane compound having a general structural formula shown in Formula I and / or Formula II: Formula I Formula II Wherein, R1 is independently selected from any one of a fluorine-substituted or unsubstituted C2-C6 alkenyl group, a fluorine-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group; R2 is independently selected from any one of a fluorine-substituted or unsubstituted C1-C6 linear alkyl group, a fluorine-substituted or unsubstituted C2-C6 alkenyl group, a fluorine-substituted or unsubstituted C2-C6 alkynyl group, a cyano group, and a C1-C5 nitrile group; The mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.1-5%.

2. The electrolyte for a lithium-ion battery according to claim 1, wherein, The additive includes at least one of the following compound structures: Compound 1 Compound 2 Compound 3 Compound 4 Compound 5 Compound 6.

3. The electrolyte for a lithium-ion battery according to claim 1, wherein The mass percentage of the tributylstannane compound in the lithium-ion battery electrolyte is 0.3-3%.

4. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, The additive further includes an auxiliary additive. The auxiliary additive includes at least one of 1,3-propane sultone, 1,4-butane sultone, allyl-1,3-sulfonic acid lactone, ethylene sulfate, methylene methane disulfonate, vinylene carbonate, fluoroethylene carbonate, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium difluorophosphate, lithium tetrafluoro(oxalato)phosphate, difluoropyridine, hexamethylene diisocyanate, and triallyl isocyanurate.

5. The lithium-ion battery electrolyte according to claim 4, wherein The mass percentage of the additive in the lithium-ion battery electrolyte is 2-10%.

6. The electrolyte for a lithium-ion battery according to any one of claims 1 to 3, characterized in that, The organic solvent includes at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, fluoromethyl ethyl carbonate, and ethyl difluoroacetate.

7. The electrolyte for a lithium-ion battery according to any one of claims 1 to 3, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

8. The electrolyte for a lithium-ion battery according to claim 7, characterized in that, The mass percentage of the lithium salt in the lithium-ion battery electrolyte is 12-18%.

9. A lithium-ion battery, characterized in that, It includes: A housing; An electrode assembly, which is accommodated in the housing; And The lithium-ion battery electrolyte according to any one of claims 1-8, and the lithium-ion battery electrolyte is accommodated in the housing.

10. The lithium-ion battery according to claim 9, characterized in that, In the battery positive electrode of the electrode assembly, the positive electrode active material includes at least one of transition metal phosphates, transition metal oxide lithium salts, lithium titanate, and transition metal sulfides.

11. The lithium ion battery according to claim 10, wherein, The positive electrode active material includes at least one of lithium nickel manganate, lithium nickel cobalt manganate, and lithium cobaltate.

12. The lithium ion battery according to any one of claims 9 to 11, characterized in that, In the battery negative electrode of the electrode assembly, the negative electrode active material includes at least one of metallic lithium, graphite, soft carbon, hard carbon, silicon, silicon oxide, and silicon-carbon composite.

13. An electrical device, characterized in that, The electrical device includes the lithium-ion battery according to any one of claims 9-12.

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