Electrolyte, battery, battery pack and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electric equipment, the electrolyte comprises a first additive, and the first additive comprises a compound with a structure as shown in a formula I and / or a compound with a structure as shown in a formula II. The electrolyte provided by the invention can enable the battery to present excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in fields such as consumer electronic products, new energy vehicles and energy storage. With the rapid development of the new energy vehicle industry, consumers have put forward higher requirements for the cruising range and application scenarios, that is, the battery has a higher energy density and can take into account the high and low temperature performance.

[0003] At present, using a high-voltage cathode material is one of the many ways to increase the energy density of the battery. However, at high voltages, the cathode active material has high oxidizing properties, and the side reactions of the electrolyte at the cathode interface are intensified, resulting in the battery bulging, especially under high-temperature conditions. In addition, the transition metal ions in the cathode active material dissolve and migrate to accumulate on the surface of the negative electrode (such as a graphite negative electrode), which will damage the solid electrolyte interface film (SEI) on the surface of the negative electrode, and then lead to a decrease in the battery capacity and an increase in impedance, ultimately deteriorating the high-temperature cycle performance and high-temperature storage performance of the battery. In addition, under low-temperature conditions, the viscosity of the conventional electrolyte increases, the conductivity decreases, the migration rate of lithium ions slows down, and the impedance of the battery interface increases, resulting in an increase in the polarization of the battery and a decrease in the charge and discharge capacity.

[0004] Therefore, it is of great significance to develop an electrolyte that can enable the battery to take into account the high and low temperature performance. Summary of the Invention

[0005] The present invention provides an electrolyte, which can enable the battery to exhibit excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0006] The present invention provides a battery, which has excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0007] The present invention provides a battery pack, which is composed of battery cells, and the battery pack has high high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0008] The present invention also provides an electrical device, which includes a battery or a battery pack, and the electrical device has high high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance, which is beneficial to the application of the electrical device in high-temperature and low-temperature environments.

[0009] The present invention provides an electrolyte, which includes a first additive, and the first additive includes a compound having the structure shown in Formula I and / or a compound having the structure shown in Formula II:

[0010]

[0011] In the formula I, 0 ≤ x ≤ 3; R 1 ~R 8 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6-C10 aryl group;

[0012]

[0013] In the formula II, 0 ≤ y ≤ 3; R 9 ~R 20 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6-C10 aryl group.

[0014] The electrolyte as described above, wherein the compound having the structure shown in formula I includes one or more of the compounds shown in formula I-1 to formula I-5:

[0015]

[0016]

[0017] The electrolyte as described above, wherein the compound having the structure shown in formula II includes the compounds shown in formula II-1 to II-3:

[0018]

[0019] The electrolyte as described above, wherein the mass ratio of the first additive to the electrolyte is 0.1% to 10%.

[0020] The electrolyte as described above, wherein the mass ratio of the first additive to the electrolyte is 0.2% to 5%.

[0021] The electrolyte as described above, wherein the electrolyte includes a lithium salt, and the lithium salt includes one or several of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)difluorophosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0022] The electrolyte as described above, wherein the electrolyte further includes an organic solvent, and the organic solvent includes one or several of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0023] The electrolyte as described above, wherein the electrolyte further comprises a second additive, and the second additive comprises one or more of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfate, allyl-1,3-sulfonic acid lactone, and methylene methanedisulfonate.

[0024] The present invention also provides a battery comprising the electrolyte as described above.

[0025] The battery as described above, wherein the battery is a lithium-ion battery.

[0026] The present invention also provides a battery pack comprising the battery as described above.

[0027] The present invention also provides an electrical device, which comprises the battery as described above or the battery pack as described above.

[0028] The electrolyte, battery, battery pack, and electrical device provided by the present invention. The electrolyte comprises the compound of Formula I and / or the compound of Formula II. The compound of Formula I or the compound of Formula II can participate in the formation of a complete, dense, and homogeneous CEI film, thereby improving the stability of the positive electrode / electrolyte interface, effectively reducing the contact between the electrolyte and the positive electrode active material, inhibiting the dissolution of transition metal ions in the positive electrode active material, and improving the high-temperature cycle life and high-temperature storage performance of the lithium-ion battery. Moreover, the compound of Formula I or the compound of Formula II can also participate in film formation (SEI film) at the negative electrode, effectively reducing the impedance of the SEI film, thereby improving the low-temperature discharge performance of the battery. In addition, the compound of Formula I or the compound of Formula II can play a role of "removing water and inhibiting acid" in the electrolyte, avoiding side reactions between the components in the electrolyte and water, and problems such as the damage of the passivation films (CEI film, SEI film) of the positive and negative electrodes caused by the resulting impurities, thereby improving the high-temperature cycle life and high-temperature storage performance of the battery. Detailed Embodiments

[0029] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below. The following specific embodiments are only used to describe the principles and features of the present invention, and the examples are only used to explain the present invention, not to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] An embodiment of the present invention provides an electrolyte, which comprises a first additive, and the first additive comprises a compound having the structure shown in Formula I and / or a compound having the structure shown in Formula II:

[0031]

[0032] In formula I, 0 ≤ x ≤ 3; R 1 ~R 8 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6-C10 aryl group;

[0033]

[0034] In formula II, 0 ≤ y ≤ 3; R 9 ~R 20 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6-C10 aryl group.

[0035] In the compound of formula I, 0 ≤ x ≤ 3, x is selected from integers from 0 to 3, that is, x is 0, 1, 2 or 3.

[0036] In the compound of formula II, 0 ≤ y ≤ 3, y is selected from integers from 0 to 3, that is, y is 0, 1, 2 or 3.

[0037] In the embodiments of the present invention, the halogen atom refers to halogen atoms such as -F, -Cl, -Br, -I, etc.

[0038] In the embodiments of the present invention, the substituted or unsubstituted C1-C5 alkyl group refers to a linear or branched alkyl group with 1-5 carbon atoms having substituents or no substituents, or a cycloalkyl group with 3-5 carbon atoms having substituents or no substituents; wherein, the linear alkyl group can be a straight-chain alkyl group without branches or an isomeric alkyl group with branches; exemplarily, the number of carbon atoms of the C1-C5 alkyl group can be 1, 2, 3, 4 or 5.

[0039] In the embodiments of the present invention, the substituted or unsubstituted C2-C5 unsaturated hydrocarbon group refers to an unsaturated hydrocarbon group with 2-5 carbon atoms having substituents or no substituents, that is, an alkenyl group with 2-5 carbon atoms having substituents or no substituents, or an alkynyl group with 2-5 carbon atoms having substituents or no substituents; exemplarily, the number of carbon atoms of the C2-C5 unsaturated hydrocarbon group can be 2, 3, 4 or 5.

[0040] In the embodiments of the present invention, the substituted or unsubstituted C6-C10 aryl group refers to an aryl group with 6-10 carbon atoms having substituents or no substituents; wherein, when the aryl group has substituents, the substituents can be alkyl groups (in this case, the aryl group is an alkaryl group). Exemplarily, the number of carbon atoms of the C6-C10 aryl group can be 6, 7, 8, 9 or 10.

[0041] In the embodiments of the present invention, the type and substitution position of the substituents are not limited and can be selected according to actual needs. For example, the substituents include at least one of a halogen atom, an alkoxy group, and a trimethylsilyl group.

[0042] Exemplarily, R 1 ~R 8 、R 9 ~R 20 may each independently be selected from -H, -F, -Cl, -Br, -I, -CH 3 、-CH 2 CH 3 、-CH 2 CH 2 CH 3 、-CF 3 、-CH=CH 2 、-CH=CF 2 、-C≡C-CH 3 、-C≡C-CF 3 、-CH 2 CH 2 OH、-CH 2 CH 2 NH 2 、-C 6 H 5 or -C 6 H 5 -CH 3 and so on.

[0043] According to the above solution provided by the present invention, after applying this electrolyte to a battery, the battery has excellent high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance. The inventor analyzed the principle and believes that the reason may be that, on the one hand, the compound of formula I or the compound of formula II has a higher HOMO energy level and a lower oxidation potential compared to the solvent molecules, and can be preferentially oxidized and decomposed on the surface of the positive electrode to form a complete, dense, and highly homogeneous CEI film, thereby improving the stability of the positive electrode / electrolyte interface. The stable CEI film can effectively reduce the contact between the electrolyte and the positive electrode active material, inhibit the dissolution of transition metal ions in the positive electrode active material, reduce the gas generation of the lithium-ion battery, and improve the high-temperature cycling life and high-temperature storage performance of the lithium-ion battery; on the other hand, the compound of formula I or the compound of formula II can also participate in film formation (SEI) at the negative electrode, decompose during the first cycle of the battery, and regulate and modify the composition and morphology of the negative electrode SEI film, thereby increasing the content of inorganic components in the SEI film and effectively reducing the impedance of the negative electrode interface, thus improving the low-temperature discharge performance of the battery; in addition, the compound of formula I or the compound of formula II can play a role of "removing water and suppressing acid" in the electrolyte, avoiding side reactions between the components in the electrolyte and water, and problems such as the damage of the passivation films (CEI film, SEI film) of the positive and negative electrodes caused by the resulting impurities, thereby improving the high-temperature cycling life and high-temperature storage performance of the battery.

[0044] In the embodiments of the present invention, the preparation method of the first additive is not limited. Exemplarily, the first additive can be prepared by a preparation method including the following steps:

[0045] Perform a first reaction on the first compound with phosphorus trichloride and anhydrous dichloromethane to obtain a second compound. Subsequently, in a nitrogen atmosphere, perform a second reaction on the second compound with antimony trifluoride to obtain the first additive;

[0046] Among them, the first compound includes a compound having the structure shown in formula III or a compound having the structure shown in formula IV:

[0047]

[0048] The second compound includes a compound having the structure shown in formula V or a compound having the structure shown in formula VI:

[0049]

[0050] Exemplarily, the preparation reaction formula of the compound of formula I-1 is as follows:

[0051]

[0052] In a specific embodiment, the compound having the structure shown in formula I includes one or more of the compounds shown in formula I-1 to formula I-5:

[0053]

[0054] When the compound of Formula I is selected from the above compounds, the compound of Formula I can better participate in the construction of the CEI film and the SEI film. Its high energy level and low oxidation potential enable it to be preferentially oxidized and decomposed on the surface of the positive electrode, forming a complete, dense and homogeneous protective film (CEI), making the CEI film more stable, thus better protecting the positive electrode active material and further improving the high-temperature cycle performance and high-temperature storage performance of the battery. In addition, the above compound can also decompose during the first cycle, participate in the formation of the negative electrode film (SEI), regulate and modify the components and morphology of the negative electrode SEI film, increase the content of inorganic components in the SEI film, make the impedance of the SEI film lower, and then make the impedance of the battery lower, thereby improving the low-temperature discharge performance of the battery.

[0055] In a specific embodiment, the compound having the structure shown in Formula II includes the compounds shown in Formulas II-1 to II-3:

[0056]

[0057]

[0058] When the compound of Formula II is selected from the above compounds, the compound of Formula II participates in the construction of the CEI film and the SEI film, generating a CEI film with better stability and an SEI film with lower impedance, suppressing the side reaction between the positive electrode active material and the electrolyte and the dissolution of transition metals in the positive electrode active material, and reducing the impedance of the battery, thereby further improving the high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance of the battery to a greater extent.

[0059] In addition, the compounds of Formula I and Formula II can react with trace water in the electrolyte to avoid the dissolution and damage of the passivation films on the positive and negative electrodes caused by the reaction of LiPF 6 with H 2 O to generate impurities such as HF; at high temperatures, they can combine with the Lewis acid PF 6 produced by the decomposition of LiPF 5 to avoid the decomposition reaction of the catalytic solvent by PF 5 and reduce the impact on the battery stability. The lithium-ion battery prepared with at least one of the above compounds can maintain excellent high and low temperature performance, long-term cycle and storage performance at high voltages.

[0060] In a specific embodiment, the mass ratio of the first additive to the electrolyte is 0.1% to 10%, such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc. When the mass ratio of the first additive to the electrolyte is within the above range, the thicknesses of the CEI film and SEI film constructed by the first additive are appropriate, so that the positive electrode active material can be sufficiently protected, and the increase in the impedance of the battery caused by the excessive thickness of the CEI film and SEI film can be avoided, thereby better improving the high-temperature cycling performance, high-temperature storage performance and low-temperature discharge performance of the battery.

[0061] In a specific embodiment, the mass ratio of the first additive to the electrolyte is 0.2% to 5%, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc. When the mass ratio of the first additive to the electrolyte is within the above range, the thicknesses of the CEI film and SEI film are more suitable, which can not only better protect the positive electrode active material, but also reduce the impedance of the battery, thereby making the high-temperature cycling performance, high-temperature storage performance and low-temperature discharge performance of the battery better.

[0062] In a specific embodiment, the electrolyte includes an electrolyte salt, and the electrolyte salt includes a lithium salt. The lithium salt includes lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)difluorophosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide salts, or several of them. When the lithium salt selects the above compounds, the lithium salt can fully play its role, and an electrolyte with high ionic conductivity and high stability can be prepared, so that the lithium-ion battery can fully exert its electrochemical performance, and the compound of formula I or the compound of formula II can react with trace water in the electrolyte to avoid the impurities generated by the reaction of the electrolyte salt with water from damaging the passivation films on the positive and negative electrodes. For example, it can avoid the dissolution and damage of the passivation films on the positive and negative electrodes caused by impurities such as HF generated by the reaction of LiPF 6 with H 2 O, and at high temperatures, it can also combine with the Lewis acid PF 6 generated by the decomposition of LiPF 5 to avoid PF 5 from catalyzing the decomposition reaction of the solvent, thereby improving the high-temperature cycling life and high-temperature storage performance of the battery.

[0063] In a specific embodiment, the molar amount of the lithium salt to the volume of the electrolyte is 0.5 - 2 mol / L. When the mass ratio of the lithium salt to the electrolyte is within the above range, the lithium salt plays a greater role in the electrolyte, the ionic conductivity of the electrolyte is higher, and the high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance of the battery are better. Preferably, the molar amount of the lithium salt to the volume of the electrolyte is 0.8 - 1.3 mol / L.

[0064] In a specific embodiment, the electrolyte further includes an organic solvent, and the organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate. When the above organic solvents are selected as the organic solvent, the lithium salt and the first additive can be fully dissolved to obtain an electrolyte with high stability and high conductivity, and at the same time, the viscosity of the electrolyte is appropriate, so that the lithium salt and the first additive can better play their roles, making the battery exhibit higher high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance.

[0065] In a specific embodiment, the electrolyte further includes a second additive, and the second additive includes one or more of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfate, allyl-1,3-sultone, and methanedisulfonic acid methyl ester. When the above substances are selected as the second additive, the second additive can cooperate with the first additive to participate in the construction of the SEI film, making the impedance of the SEI film lower, thereby reducing the impedance of the battery, and further improving the high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance of the battery.

[0066] In a specific embodiment, the mass percentage content of the second additive in the electrolyte is 0.1% - 5%. When the mass percentage content of the second additive in the electrolyte is within the above range, the second additive can cooperate better with the first additive, making the impedance of the SEI film lower, further improving the mobility of lithium ions, and thus improving the high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance of the battery to a greater extent. Preferably, the mass percentage content of the second additive in the electrolyte is 0.2% - 2%.

[0067] The embodiment of the present invention does not limit the preparation method of the electrolyte. In a specific embodiment, as long as the lithium salt, the organic solvent, and the first additive are mixed in a specified ratio.

[0068] Furthermore, when the electrolyte further includes a second additive, the lithium salt, the organic solvent, the first additive, and the second additive are mixed in a specified ratio.

[0069] An embodiment of the present invention further provides a battery including the above-mentioned electrolyte. Based on the electrolyte provided by the present invention, the battery exhibits excellent high-temperature cycling performance, high-temperature storage performance, and low-temperature discharge performance.

[0070] In a specific embodiment, the battery is a lithium-ion battery. The lithium-ion battery of the embodiment of the present invention includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. Among them, the positive electrode current collector is generally an aluminum foil. The positive electrode active material includes a transition metal oxide of lithium, such as LiCoO 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、LiFePO 4 、LiNi x Co y Mn 1-x-y O 2 and at least one of them, where 0 < x < 1 and 0 < y < 1. When the positive electrode active material is a transition metal oxide of lithium, the discharge specific capacity of the battery can be improved, and the stability of the battery can be improved.

[0071] The lithium-ion battery of the embodiment of the present invention includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder. Among them, the negative electrode current collector is generally a copper foil, and the negative electrode active material is selected from one or more of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials, and lithium-containing metal composite oxide materials.

[0072] For the selection of the conductive agent and the binder in the positive electrode active material layer and the negative electrode active material layer of the embodiment of the present invention, conventional materials in the art can be used.

[0073] The lithium-ion battery of the embodiment of the present invention further includes a separator, which is a separator well-known in the art that can be used in a battery and is stable for the electrolyte used. It can include one or more of polyolefin, aromatic polyamide, polytetrafluoroethylene, and polyethersulfone, and can be specifically set according to needs.

[0074] An embodiment of the present invention further provides a battery pack including the battery as described above. The battery pack has the advantages corresponding to the above-mentioned electrolyte, which will not be elaborated here.

[0075] Generally, a battery pack includes a plurality of the above-mentioned batteries, which are used as single cells and are connected to form a battery pack. Among them, these batteries can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a hybrid connection including these connection methods at the same time, and no special limitation is imposed on this.

[0076] An embodiment of the present invention further provides an electrical device, including the above-mentioned battery or the above-mentioned battery pack. This electrical device has the corresponding advantages as the above-mentioned electrolyte, which will not be elaborated here.

[0077] The electrical device of the embodiment of the present invention can be a conventional electrical device in the art, such as a power device (such as an electric vehicle, an electric car), an electronic device (such as a mobile phone, a tablet computer, a laptop computer, a digital camera, etc.), a wearable device (such as a watch, a bracelet, a VR glasses, etc.), an energy storage power station, etc., and no special limitation is imposed on this.

[0078] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0079] The present invention will be further described below through specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, conventional materials and conventional instruments, which can be obtained commercially, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0080] Example 1

[0081] The preparation method of the electrolyte in this embodiment includes the following steps:

[0082] Prepare the electrolyte in a glove box filled with argon with a purity of 99.999%, control the moisture in the glove box to ≤0.1 ppm, and control the temperature at room temperature. Mix ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a mass ratio of EC:DMC:DEC = 3:5:2, then add lithium hexafluorophosphate (LiPF 6 ) to a molar concentration of 1.2 mol / L, then add the first additive (4,4'-bis[2-fluoro-1,3,2-dioxaphospholane], that is, the compound shown in Formula I-1), and finally add the second additive (vinylene carbonate VC). After mixing evenly, the electrolyte is obtained;

[0083] Among them, the mass ratio of the first additive I-1 to the electrolyte is 0.2%, and the mass ratio of vinylene carbonate to the electrolyte is 1%.

[0084] Example 2

[0085] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 0.5%.

[0086] Example 3

[0087] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 1%.

[0088] Example 4

[0089] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 2%.

[0090] Example 5

[0091] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 0.05%.

[0092] Example 6

[0093] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 0.1%.

[0094] Example 7

[0095] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 3%.

[0096] Example 8

[0097] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 5%.

[0098] Example 9

[0099] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 7%.

[0100] Example 10

[0101] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 10%.

[0102] Example 11

[0103] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass ratio of the first additive I-1 to the electrolyte is 12%.

[0104] Example 12

[0105] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the first additive is the compound of formula I-2.

[0106] Example 13

[0107] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the first additive is the compound of formula I-3.

[0108] Example 14

[0109] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the first additive is the compound of formula I-4.

[0110] Example 15

[0111] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the first additive is the compound of formula II-1.

[0112] Example 16

[0113] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the first additives are the compound of formula I-1 and the compound of formula II-1, and the mass ratio of the compound of formula I-1 to the compound of formula II-1 is 1:1.

[0114] Example 17

[0115] The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that vinylene carbonate is not added to the electrolyte.

[0116] Example 18

[0117] The preparation method of the electrolyte in this example is substantially the same as that in Example 2, except that vinylene carbonate is not added to the electrolyte.

[0118] Example 19

[0119] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that vinylene carbonate is not added to the electrolyte.

[0120] Example 20

[0121] The preparation method of the electrolyte in this example is substantially the same as that in Example 4, except that vinylene carbonate is not added to the electrolyte.

[0122] Example 21

[0123] The preparation method of the electrolyte in this example is substantially the same as that in Example 8, except that vinylene carbonate is not added to the electrolyte.

[0124] Example 22

[0125] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the mass ratio of vinylene carbonate to the electrolyte is 0.05%.

[0126] Example 23

[0127] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the mass ratio of vinylene carbonate to the electrolyte is 0.1%.

[0128] Example 24

[0129] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the mass ratio of vinylene carbonate to the electrolyte is 5%.

[0130] Example 25

[0131] The preparation method of the electrolyte in this example is substantially the same as that in Example 3, except that the mass ratio of vinylene carbonate to the electrolyte is 6%.

[0132] Comparative Example 1

[0133] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 3, except that the first additive is a compound represented by Formula VII-1:

[0134]

[0135] Comparative Example 2

[0136] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 3, except that the first additive is a compound represented by Formula VIII-1:

[0137]

[0138] Comparative Example 3

[0139] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 3, except that the first additive is not added to the electrolyte.

[0140] Comparative Example 4

[0141] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 19, except that the first additive is a compound represented by Formula VII-1.

[0142] Comparative Example 5

[0143] The preparation method of the electrolyte in this comparative example is substantially the same as that in Example 19, except that the first additive is a compound represented by Formula VIII-1.

[0144] The specific parameters of the electrolyte formulations provided in Examples 1-25 and Comparative Examples 1-5 are shown in Table 1.

[0145] Table 1

[0146]

[0147]

[0148] Among them, " / " indicates that this component is not added.

[0149] Test Example

[0150] The electrolytes of the examples and comparative examples were used to prepare lithium-ion batteries in combination with positive electrode sheets, negative electrode sheets and separators. Specifically: the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), conductive materials CNT, conductive carbon black and binder (polyvinylidene fluoride) PVDF were dispersed in the solvent NMP according to a mass ratio of 94:2:2:2 to obtain the positive electrode active material layer slurry; the positive electrode active material layer slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying, rolling, baking, slitting and spot welding the electrode tabs, a positive electrode sheet was obtained, and the areal density of the positive electrode sheet was 320 g / m 2 .

[0151] The negative electrode active material artificial graphite, conductive agent conductive carbon black, CNT, sodium carboxymethyl cellulose (CMC) and binder SBR were dispersed in deionized water according to a mass ratio of 95:1.25:1.25:1.25:1.25, and stirred evenly to obtain the negative electrode active material layer slurry; the negative electrode active material layer slurry was uniformly coated on the surface of the negative electrode current collector copper foil, and after drying, rolling, baking, slitting and spot welding the electrode tabs, a negative electrode sheet was obtained, and the areal density of the negative electrode sheet was 200 mg / cm 2 .

[0152] The prepared positive electrode sheet, negative electrode sheet and separator were stacked in sequence. The separator was a ceramic-coated separator. The separator was placed between the positive electrode sheet and the negative electrode sheet. After winding, the battery cell was placed in an aluminum-plastic film for encapsulation, dried, injected with electrolyte and sealed. After standing, forming, second sealing, capacity grading and other processes, a lithium-ion battery was obtained.

[0153] The following battery performance tests were carried out on lithium batteries with electrolytes including examples and comparative examples, and the test methods are as follows:

[0154] High-temperature (45°C) cycle performance test: In a 45°C constant-temperature oven, the battery is charged at a constant current of 1C to 4.5V, then switched to constant-voltage charging until the cut-off current is 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.5V, which is recorded as one charge-discharge cycle. Then, 500 cycles are carried out according to the above conditions; the discharge capacity in the first week is recorded as C 0 , and the discharge capacity in the 500th cycle is recorded as C 1 ; High-temperature (45°C) cycle capacity retention rate (%) = (C 1 / C 0 ) × 100%, as shown in Table 2;

[0155] High-temperature (60°C) storage performance test: After the battery is charged at a constant current of 1C to 4.5V at 25°C, it is switched to constant-voltage charging until the cut-off current is 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.5V. This discharge capacity is recorded as the initial capacity C 0 , and the thickness H of the battery before storage is measured 0 . The battery is transferred to a high-temperature test cabinet and stored at 60°C for 28 days; after storage, the test battery is taken out, left standing at room temperature for 10h, and the thickness H of the battery after storage is measured 1 , and then discharged at a constant current of 1C to 2.5V, and the discharge capacity C 1 is recorded. After standing for 2h, it is charged at a constant current of 1C and switched to constant-voltage charging to 4.5V, 0.05C cut-off, left standing for 0.5h and then discharged at a constant current of 1C to 2.5V, and the discharge capacity C 2 is recorded; High-temperature (60°C) storage capacity remaining rate (%) = (C 1 / C 0 ) * 100%; High-temperature (60°C) storage capacity recovery rate (%) = (C 2 / C 0 ) * 100%; Battery thickness growth rate (%) = [(H 1 - H 0 ) / H 0 ) * 100%, as shown in Table 2;

[0156] Low-temperature (-20°C) discharge performance test: After the battery is charged at a constant current of 1C to 4.5V at 25°C, it is switched to constant-voltage charging until the cut-off current is 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.5V. This discharge capacity is recorded as C 0; After charging the battery at a constant current of 1C to 4.5V at 25°C, switch to constant voltage charging until the cut-off current is 0.05C, let it stand for 0.5h, transfer the battery to a -20°C environmental chamber, leave it for 6h, and then discharge it at a constant current of 0.2C to 2.5V. This discharge capacity is denoted as C 1 ; Low-temperature (-20°C) discharge capacity ratio (%) = (C 1 / C 0 ) × 100%, as shown in Table 2

[0157] Table 2

[0158]

[0159]

[0160] As can be seen from the table, in Examples 1-25, by using the first additive provided by the present invention to prepare the electrolyte, compared with Comparative Examples 1-5, the battery has achieved good high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance. In Examples 1-4, 6-10, 12-16, compared with Examples 5 and 11, the high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance of the battery are further improved by controlling the mass ratio of the first additive to the electrolyte. In addition, in Examples 1-4 and 8, after adding the second additive, compared with Examples 18-21, the high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance of the battery are also improved

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention

Claims

1. An electrolyte, characterized in that: The method comprises a first additive, wherein the first additive comprises a compound having a structure shown in Formula I and / or a compound having a structure shown in Formula II: In the formula I, 0≤x≤3; R1 to R8 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C2 to C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6 to C10 aryl group; In the formula II, 0≤y≤3; R9~R 20 Each is independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, or a substituted or unsubstituted C6-C10 aryl group.

2. The electrolyte according to claim 1, characterized in that The compound having the structure shown in Formula I includes one or more compounds shown in Formula I-1 to Formula I-5:

3. The electrolyte according to claim 1, characterized in that The compound having the structure shown in Formula II includes compounds shown in Formula II-1 to II-3:

4. The electrolyte according to claim 1, characterized in that The mass ratio of the first additive to the electrolyte is 0.1% to 10%.

5. The electrolyte according to claim 4, characterized in that The mass ratio of the first additive to the electrolyte is 0.2% to 5%.

6. The electrolyte according to any one of claims 1 to 5, characterized in that: The electrolyte includes a lithium salt, and the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide and lithium bisfluorosulfonylimide.

7. The electrolyte according to any one of claims 1 to 5, characterized in that The electrolyte also includes an organic solvent, which includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

8. The electrolyte according to any one of claims 1 to 5, characterized in that The electrolyte further includes a second additive, which includes one or more of vinylene carbonate, fluoroethylene carbonate, propylene sulfite, vinyl sulfate, propylene-1,3-sultone and methylene methanedisulfonate.

9. A battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 8.

10. The battery according to claim 9, characterized in that The battery is a lithium-ion battery.

11. A battery pack, characterized in that: A battery comprising the battery of claim 9 or 10.

12. An electrical equipment, characterized in that: Comprising the battery according to claim 9 or 10 or the battery pack according to claim 11.

Images