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

Abstract

This application belongs to the field of new energy materials technology, specifically relating to a non-aqueous electrolyte, a lithium-ion battery, and electrical equipment. This application introduces an additive with a specific structure and functional groups into the electrolyte. Through the combined and synergistic effects of the functional groups in this additive, it achieves passivation of the positive and negative electrode surfaces, inhibition of transition metal ion dissolution, and dehydration and acid suppression. This effectively improves the high-temperature / high-pressure performance of high-energy-density lithium batteries, slows capacity decay, and suppresses gas generation and impedance growth.

Description

Technical Field

[0001] This application belongs to the field of new energy materials technology, specifically relating to a non-aqueous electrolyte, a lithium-ion battery, and an electrical device. Background Technology

[0002] With the increasing demand for energy density in the power lithium battery market, lithium batteries urgently need to complete the innovation and upgrading at the material level. High-energy-density lithium batteries have become a current research hotspot and also the general trend of future lithium battery development. The development of high-energy-density lithium batteries at the material level mainly includes two directions: first, broadening the operating voltage range of materials, especially increasing the upper voltage limit, which can effectively improve the specific capacity and voltage platform of cathode materials; second, upgrading cathode and anode materials by optimizing the active components, structure, and morphology of electrode materials to improve their specific capacity. For example, compared with the current mainstream medium-nickel ternary cathode paired with graphite anode system, high-nickel ternary / lithium-rich manganese-based cathode materials paired with silicon-oxygen / silicon-carbon / lithium metal anode systems have a significant advantage in improving specific energy. However, some practical problems of high-energy-density systems limit their actual development. These problems mainly include the accelerated dissolution of transition metal ions in the cathode under high pressure / high temperature (due to the combined effect of the Jan Taylor effect and the hydrolysis of HF generated by commercial LiPF6 electrolyte), which leads to the destruction of the cathode structure; the oxidative decomposition of the electrolyte under high pressure; the deposition of transition metal ions in the anode; and the significant volume change of the anode leading to the continuous destruction and recombination of the SEI. These factors cause the high-energy-density system to accelerate capacity decay under high temperature / high pressure, accompanied by severe gas production and impedance growth. Summary of the Invention

[0003] Therefore, the technical problem to be solved by this application is to overcome the defects in the existing high-energy-density lithium battery system, such as accelerated capacity decay under high temperature / high pressure, accompanied by severe gas production and impedance growth, thereby providing a non-aqueous electrolyte, lithium-ion battery and electrical device.

[0004] To address the existing problems of high-energy-density lithium batteries, this application introduces an additive with a specific structure and functional groups into the electrolyte design. Through the combined and synergistic effects of the functional groups in this additive, the positive and negative electrode surfaces can be passivated, the dissolution of transition metal ions can be suppressed, and water and acid can be removed and inhibited, thereby effectively improving the high-temperature / high-pressure performance of high-energy-density lithium batteries.

[0005] Therefore, this application provides the following technical solution:

[0006] According to one aspect of this application, a non-aqueous electrolyte is provided, comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound with a structure specifically shown in formula (I):

[0007]

[0008] R1-R6 are each independently derived from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one heteroelement of S, N, and O, silyl, siloxane, siloxamine, carbonyl, or any combination thereof, and at least one of R1-R5 includes an alkynyl group.

[0009] In some alternative embodiments, R1-R6 are each independently derived from hydrogen, a C1-C8 alkyl group, a C1-C8 alkynyl group, a C6-C9 substituted or unsubstituted aromatic group, a C3-C7 S-containing heterocycle, a C1-C8 silyl group, a C1-C8 siloxane group, a C1-C8 siloxamine group, and a C1-C8 carbonyl group; wherein the substituents in the substituted aromatic groups include halogens and any combination of C1-C4 alkyl groups.

[0010] In some alternative embodiments, the additive comprises a compound having any of the following structures:

[0011]

[0012]

[0013] In some alternative embodiments, the content of the compound represented by formula (I) is 0.1%-2% based on the total mass of the non-aqueous electrolyte.

[0014] In some optional embodiments, the molar concentration of the lithium salt is 0.7-1.5 mol / L;

[0015] And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

[0016] In some optional embodiments, the non-aqueous electrolyte further includes other functional additives, including positive and negative electrode film-forming additives.

[0017] And / or, based on the total mass of the non-aqueous electrolyte, the amount of the other functional additives added is 0.5%-10%.

[0018] In some optional embodiments, the positive and negative electrode film-forming additives include at least one of additives containing S or double bonds or F or B or P or CN, or lithium salt additives.

[0019] In some alternative embodiments, the organic solvent includes at least one of carbonate solvents or carboxylic acid ester solvents.

[0020] According to another aspect of this application, a lithium-ion battery is provided, comprising the aforementioned non-aqueous electrolyte.

[0021] According to another aspect of this application, an electrical device is provided, including the aforementioned lithium-ion battery.

[0022] The technical solution of this application has the following advantages:

[0023] The non-aqueous electrolyte provided in this application introduces an additive with a specific structure and functional groups into the electrolyte. Through the combined and synergistic effect of the functional groups of the additive, it can achieve the functions of passivating the positive and negative electrode surfaces, inhibiting the dissolution of transition metal ions, and removing water and inhibiting acid. This can effectively improve the high-temperature / high-voltage performance of high-energy-density lithium batteries, slow down capacity decay, and suppress gas production and impedance growth. Specifically, the additive contains unsaturated alkyne groups, which serve to form films at both positive and negative electrodes and remove HF. The electron-withdrawing alkyne groups conjugated with the benzene ring reduce the electron cloud density on the benzene ring, lowering the risk of high-voltage polymerization of the benzene ring and forming high-resistance polymers, thus improving the high-voltage stability of the interfacial film. Simultaneously, the strongly electron-withdrawing alkyne groups and silicon oxides connected to N make it easier for the central N atom to gain electrons and be reduced at the negative electrode, forming a Li3N-rich SEI and enhancing the ion-conducting ability of the SEI. The N atom containing lone pairs of electrons can both complex transition metal ions and donate electrons to adjacent silicon oxides, making it easier for oxygen in the silicon oxide to combine with hydrogen protons or ions in water or HF, further enhancing the water removal and acid suppression capabilities of the silicon oxide. Flexible Si-O and rigid... The benzene ring imparts a combination of rigidity and flexibility to the film, and its excellent mechanical stability effectively matches the volume expansion / contraction of the electrode materials during charging and discharging, mitigating interfacial film damage caused by volume changes. Simultaneously, the polar N / O promotes rapid lithium-ion transport at the interfacial film, resulting in excellent ion-conducting properties. Through the synergistic effect of these functional groups, the additive preferentially decomposes on the positive and negative electrode surfaces to form SEI and CEI interfacial films with excellent ion-conducting properties and high stability. This effectively passivates the positive and negative electrode surfaces and also enhances water removal, acid suppression, and the inhibition of transition metal ion dissolution. The combined effect results in lithium batteries using optimized electrolytes containing the additive exhibiting significantly improved high-temperature / high-pressure performance.

[0024] The non-aqueous electrolyte provided in this application, by further defining the structure of the compound shown in formula (I), can improve the film-forming flexibility and robustness, ion conduction and film-forming properties by increasing the content of polar Si, O, and N groups or introducing benzene rings or heterocyclic groups while retaining the characteristic functional groups.

[0025] The non-aqueous electrolyte provided in this application, by limiting the content of the compound shown in formula (I), can ensure that the compound can fully participate in the formation of a stable SEI and CEI interface film, while avoiding excessively thick or thin films that would restrict lithium-ion transport kinetics or result in insufficient film formation.

[0026] The non-aqueous electrolyte provided in this application, by limiting the lithium salt concentration, can ensure that the electrolyte has appropriate ionic conductivity and lithium ion transference number.

[0027] The non-aqueous electrolyte provided in this application, with its limitations on the types and amounts of other additives, can further optimize the film-forming structure and composition of the positive and negative electrodes, and improve the stability and uniformity of the film formation.

[0028] The non-aqueous electrolyte provided in this application limits the types of organic solvents used, ensuring that the solvents have suitable viscosity and dielectric constant, thereby enabling sufficient dissociation of lithium salts and ensuring high lithium-ion conductivity of the electrolyte.

[0029] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0030] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0031] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0032] To overcome the shortcomings of existing high-energy-density lithium battery systems, such as accelerated capacity decay under high temperature / high pressure, accompanied by severe gas generation and impedance increase, this application provides the following technical solution:

[0033] According to one aspect of this application, a non-aqueous electrolyte is provided, comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound with a structure specifically shown in formula (I):

[0034]

[0035] R1-R6 are each independently derived from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one heteroelement of S, N, and O, silyl, siloxane, siloxamine, carbonyl, or any combination thereof, and at least one of R1-R5 includes an alkynyl group. As an example, the halogen includes at least one of F, Cl, and Br; the C1-C8 alkyl group includes at least one of methyl, ethyl, trimethylalkyl, and triethylalkyl; the C1-C8 alkenyl group includes at least one of vinyl, propenyl, and trimethylalkenyl; the C1-C8 alkynyl group includes at least one of ethynyl, trimethylethynyl, and trimethylsilylethynyl; the substituted or unsubstituted aromatic group includes at least one of phenyl and halogen-substituted phenyl (fluorophenyl); the heterocycle containing at least one heteroelement of S, N, and O includes at least one of thiophene, furanyl, and pyrroleyl; the silyl group can be trimethylsilyl; the silazyl group can be trimethylsiloxane; the siloxane group can be trimethylsiloxane; the carbonyl group can be trimethylethoxycarbonyl, etc.

[0036] This application introduces an additive with a specific structure and functional groups into the electrolyte. Through the combined and synergistic effects of the functional groups in this additive, it can passivate the surfaces of the positive and negative electrodes, inhibit the dissolution of transition metal ions, and remove water and suppress acid, thereby effectively improving the high-temperature / high-voltage performance of high-energy-density lithium batteries, slowing down capacity decay, and suppressing gas generation and impedance growth. Specifically, the additive contains unsaturated alkyne groups, which have the functions of forming films on both positive and negative electrodes and removing HF. The electron-withdrawing alkyne groups are conjugated with the benzene ring, which reduces the electron cloud density on the benzene ring, reducing the risk of high-voltage polymerization of the benzene ring and forming high-resistance polymers, thus improving the high-voltage stability of the interfacial film. At the same time, the strong electron-withdrawing alkyne groups and silicon oxides connected to N make it easier for the central N atom to gain electrons and be reduced at the negative electrode, forming a Li3N-rich SEI and improving the ion-conducting ability of the SEI. The N containing lone pair electrons can both complex transition metal ions and provide electrons to the adjacent silicon oxides, making it easier for the oxygen in the silicon oxides to combine with hydrogen protons or ions in water or HF, further enhancing the water removal and acid suppression capabilities of the silicon oxides. Flexible Si-O and rigid The benzene ring imparts a combination of rigidity and flexibility to the film, and its excellent mechanical stability effectively matches the volume expansion / contraction of the electrode materials during charging and discharging, mitigating interfacial film damage caused by volume changes. Simultaneously, the polar N / O promotes rapid lithium-ion transport at the interfacial film, resulting in excellent ion-conducting properties. Through the synergistic effect of these functional groups, the additive preferentially decomposes on the positive and negative electrode surfaces to form SEI and CEI interfacial films with excellent ion-conducting properties and high stability. This effectively passivates the positive and negative electrode surfaces and also enhances water removal, acid suppression, and the inhibition of transition metal ion dissolution. The combined effect results in lithium batteries using optimized electrolytes containing the additive exhibiting significantly improved high-temperature / high-pressure performance.

[0037] In some alternative embodiments, R1-R6 are each independently derived from hydrogen, a C1-C8 alkyl group, a C1-C8 alkynyl group, a C6-C9 substituted or unsubstituted aromatic group, a C3-C7 S-containing heterocycle, a C1-C8 silyl group, a C1-C8 siloxane group, a C1-C8 siloxamine group, and a C1-C8 carbonyl group; wherein the substituents in the substituted aromatic groups include halogens and any combination of C1-C4 alkyl groups.

[0038] In some alternative embodiments, the additive comprises a compound having any of the following structures:

[0039]

[0040]

[0041] The non-aqueous electrolyte provided in this application, by limiting the structure of the compound shown in formula (I), can further improve the film-forming flexibility and robustness, ion conduction and film-forming properties by increasing the content of polar Si, O, and N groups or introducing benzene ring or heterocyclic groups while retaining the characteristic functional groups.

[0042] In some optional embodiments, the content of the compound shown in formula (I) is 0.1%-2% based on the total mass of the non-aqueous electrolyte. As examples, the content of the compound shown in formula (I) is 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, 1.7%, 1.8%, 2.0%, or within any range of the above values. By limiting the content of the compound shown in formula (I), this application ensures that the compound can fully participate in the formation of a stable SEI and CEI interface film, while preventing the film from being too thick or too thin, thus limiting lithium-ion transport kinetics or resulting in insufficient film formation.

[0043] In some optional embodiments, the molar concentration of the lithium salt is 0.7-1.5 mol / L; as examples, the molar concentration of the lithium salt is 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or within any range of the above values. By limiting the lithium salt concentration, this application ensures that the electrolyte has appropriate ionic conductivity and lithium-ion transference number.

[0044] And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

[0045] In some optional embodiments, the non-aqueous electrolyte further includes other functional additives, including positive and negative electrode film-forming additives.

[0046] And / or, based on the total mass of the non-aqueous electrolyte, the amount of the other functional additives added is 0.5%-10%. As an example, the amount of the other functional additives added is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within any range of the above values.

[0047] The non-aqueous electrolyte provided in this application has limitations on the types and amounts of other additives. The conventional functional additives involved have the function of further optimizing the film structure and composition of the positive and negative electrodes, and improving the stability and uniformity of the film formation.

[0048] In some optional embodiments, the positive and negative electrode film-forming additives include at least one of additives containing S or double bonds or F or B or P or CN, or lithium salt additives.

[0049] In the embodiments of this application, the specific types of S-containing additives are not particularly limited. As an example, the S-containing additives include, but are not limited to, at least one of 1,3-propanesulfonate lactone (PS), propylene-1,3-sulfonate lactone (PST), vinyl sulfate (DTD), and methylene disulfonate (MMDS).

[0050] In the embodiments of this application, the specific types of additives containing double bonds are not particularly limited. As an example, the additives containing double bonds include, but are not limited to, at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and triallyl phosphate (TAP).

[0051] In the embodiments of this application, the specific types of the above-mentioned F-containing additives are not particularly limited. As an example, the F-containing additives include, but are not limited to, at least one of fluoroethylene carbonate (FEC) and tris(2,2,2-trifluoroethyl) phosphite (TTFP).

[0052] In the embodiments of this application, the specific types of additives containing B are not particularly limited. As an example, the additives containing B include, but are not limited to, at least one of lithium dioxalatoborate (LiBOB), lithium difluorooxalatoborate (LiODFB), tris(trimethylsilane)borate (TMSB), and pinacol 4-fluorophenylborate.

[0053] In the embodiments of this application, the specific types of the above-mentioned P-containing additives are not particularly limited. As an example, the P-containing additives include, but are not limited to, at least one of tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), lithium difluorophosphate (LiPO2F2), lithium difluorodioxanol phosphate (LiODFP), tris(2,2,2-trifluoroethyl) phosphate (TFEP), and tris(2,2,2-trifluoroethyl) phosphite (TTFP).

[0054] In the embodiments of this application, the specific types of CN-containing ester additives are not particularly limited. As an example, the CN-containing additives include, but are not limited to, at least one of hexanetrionitrile (HTCN), succinate (SN), adiponitrile (ADN), 1,2-bis(cyanoethoxy)ethane (DENE), and tricyanoethoxypropane (TCP).

[0055] In the embodiments of this application, the specific types of lithium salt additives are not particularly limited. As an example, the lithium salt additives include, but are not limited to, at least one of lithium dioxolane borate (LiBOB), lithium difluorodioxolane borate (LiODFB), lithium difluorophosphate (LiPO2F2), lithium difluorooxolane phosphate (LiODFP), lithium bissulfonylimide (LiFSI), and lithium nitrate (LiNO3).

[0056] In some alternative embodiments, the organic solvent includes at least one of carbonate solvents or carboxylic acid ester solvents. As examples, the carbonate solvents include, but are not limited to, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and at least one of various fluorinated cyclic and linear carbonates; the carboxylic acid ester solvents include, but are not limited to, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and at least one of various fluorinated cyclic and linear carboxylic acid esters.

[0057] According to another aspect of this application, a lithium-ion battery is provided, comprising the aforementioned non-aqueous electrolyte. Due to the use of the aforementioned non-aqueous electrolyte, the lithium-ion battery exhibits significantly improved high-temperature / high-pressure performance.

[0058] In this application, the lithium-ion battery includes not only the aforementioned non-aqueous electrolyte, but also a positive electrode, a negative electrode, and a separator. These components and preparation methods are conventional in the field and are not specifically limited herein.

[0059] According to another aspect of this application, an electrical device is provided, including the aforementioned lithium-ion battery. The advantages of the described electrical device over the prior art are the same as those of the lithium-ion battery described above, and will not be repeated here.

[0060] In this application, the lithium-ion battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0061] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0062] In the following examples and comparative examples, "%" represents the mass percentage content.

[0063] Example 1

[0064] This embodiment provides a non-aqueous electrolyte, which, by mass percentage, comprises: 0.1% of the compound shown in formula (I-1), 2% of DTD, 1% of PS, 1 mol / L of LiPF6, and an organic solvent composed of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 30:50:20.

[0065] Example 2

[0066] This embodiment provides a non-aqueous electrolyte, which differs from Example 1 only in that it includes 1% of the compound shown in formula (I-1).

[0067] Example 3

[0068] This embodiment provides a non-aqueous electrolyte, which differs from Example 1 only in that it includes 2% of the compound shown in formula (I-1).

[0069] Example 4

[0070] This embodiment provides a non-aqueous electrolyte, which differs from Example 1 only in that it includes 0.05% of the compound shown in formula (I-1).

[0071] Example 5

[0072] This embodiment provides a non-aqueous electrolyte, which differs from Example 1 only in that it includes 2.2% of the compound shown in formula (I-1).

[0073] Example 6

[0074] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 1% of the compound shown in formula (I-2).

[0075] Example 7

[0076] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 1% of the compound shown in formula (I-3).

[0077] Example 8

[0078] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 1% of the compound shown in formula (I-4).

[0079] Example 9

[0080] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 1% of the compound shown in formula (I-5).

[0081] Example 10

[0082] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 1% of the compound shown in formula (I-6).

[0083] Example 11

[0084] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 0.5% of the compound shown in formula (I-1) and 0.5% of the compound shown in formula (I-3).

[0085] Example 12

[0086] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it includes 0.5% of the compound shown in formula (I-1) and 0.5% of the compound shown in formula (I-5).

[0087] Example 13

[0088] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that the lithium salt concentration is 1.5 mol / L.

[0089] Example 14

[0090] This embodiment provides a non-aqueous electrolyte, which differs from Embodiment 2 only in that the lithium salt concentration is 0.7 mol / L.

[0091] Example 15

[0092] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that the organic solvent is composed of ethylene carbonate (EC): ethyl methyl carbonate (EMC): ethyl propionate (EP) in a volume ratio of 30:50:20.

[0093] Example 16

[0094] This embodiment provides a non-aqueous electrolyte, which differs from Example 2 only in that it does not contain DTD and PS, and the other additives consist of 2% VC and 1% FEC.

[0095] Comparative Example 1

[0096] This comparative example provides a non-aqueous electrolyte, which differs from Example 1 only in that it does not contain the compound shown in formula (I).

[0097] Comparative Example 2

[0098] This comparative example provides a non-aqueous electrolyte, which differs from Example 1 only in that the compound shown in formula (I-1) does not contain an alkyne group, and the alkyne group is replaced with H.

[0099] Comparative Example 3

[0100] This comparative example provides a non-aqueous electrolyte, which differs from Example 1 only in that an equal amount of phenylacetylene is used instead of the compound shown in formula (I-1).

[0101] Test case

[0102] The non-aqueous electrolytes provided in the various embodiments and comparative examples were used to prepare batteries, and various performance tests were conducted. The battery assembly steps are as follows:

[0103] 1) Preparation of positive electrode sheet

[0104] The positive electrode active material (LiNi) was mixed at a mass ratio of 96.8:2.0:1.2. 0.8 Co 0.1 Mn 0.1 O2), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dispersed in solvent N-methyl-2-pyrrolidone (NMP) and stirred under vacuum to obtain a positive electrode slurry (solid content of 56%). The positive electrode slurry is uniformly coated on both sides of the current collector aluminum foil, dried in an oven at 120℃ for 8 hours, and then cold-pressed. After trimming, cutting, and slitting, positive electrode sheets (double-sided areal density of 400 g / m²) are produced. 2 ).

[0105] 2) Preparation of negative electrode sheet

[0106] The negative electrode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95:1.5:1.5:3 and dispersed in deionized water. A negative electrode slurry (with a solid content of 55%) was obtained under vacuum stirring. The negative electrode slurry was uniformly coated on both sides of the current collector copper foil, and then dried, calendered, and vacuum dried. After cold pressing, edge trimming, cutting, and slitting, negative electrode sheets (with a double-sided areal density of 160 g / m³) were produced. 2 ).

[0107] 3) Preparation of electrolyte

[0108] In a glove box with qualified water and oxygen content, the electrolyte organic solvent is first mixed evenly, and then the relevant additives and lithium salts are added quantitatively according to the electrolyte formula in each embodiment and comparative example, and stirred evenly.

[0109] 4) Separating membrane

[0110] The diaphragm is a PE-coated ceramic diaphragm with a thickness of 20μm, purchased from Xingyuan Material.

[0111] 5) Lithium-ion battery manufacturing

[0112] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. This results in a bare cell. The tabs are then soldered onto the cells, and the bare cell is placed in outer packaging. The prepared electrolyte is injected into the dried cell (design capacity 3.5Ah). After encapsulation, the cells are left to stand at 25℃ / 60℃ for 24 hours / 6 hours to allow for thorough electrolyte wetting. Then, the cells are formed by low-rate charging (0.05C / 0.2C) at 45℃, followed by three cycles of 0.33C charge-discharge for capacity testing. Finally, the cell's performance is tested.

[0113] Perform performance testing as follows:

[0114] (1) High temperature cycling: At 45℃, the battery after capacity division was tested for cycling. It was charged with 1C constant current to 4.25V, and then charged with constant voltage until the current was 0.05C. After resting for half an hour, it was discharged with 1C constant current. The initial capacity of the battery in the first cycle was obtained and recorded as C1. The charging and discharging cycle of the first cycle was repeated in the CCCV / DC manner. The capacity after the 400th cycle was recorded as C400. The capacity retention rate (%) after 400 cycles of high temperature cycling is C400 / C1×100%. The DC internal resistance (DCR) of the cell at 50% SOC was tested and recorded before and after the high temperature cycling by the following current pulse method.

[0115] (2) DCR Test: At 25℃, the cell is charged at a constant current of 0.5C to 4.25V before or after high-temperature cycling, then charged at a constant voltage to a current of 0.05C. After resting for 1 hour, it is discharged at 0.5C for 1 hour (50% SOC), and then rested for another hour. The voltage V1 at the end is recorded. Then, it is discharged at 2C for 10 seconds, and the voltage V2 at the end is recorded. Then, the DCR of the cell before or after cycling is (V1-V2) / (I 1C -I 0.1C ), in mΩ, the DCR growth rate after cycling is (DCR 循环后 -DCR 循环前 ) / DCR 循环前 ×100%.

[0116] (3) Cyclic Gas Generation Test: At 25℃, the battery volume of the cells before or after high-temperature cycling was tested using the water displacement method. The specific operation is as follows: Place a container filled with deionized water on an electronic scale, use a clamp to fix the tabs at the top of the pouch battery, and completely immerse the pouch battery in the liquid. Record the weight change displayed on the electronic scale. By measuring the change in the volume of deionized water after the pouch battery is immersed in deionized water, the volume of the pouch battery can be calculated. The specific calculation formula is: V=(m1-m2) / ρ, where m1 is the weight of the pouch battery after it is completely immersed in deionized water, m2 is the weight of the pouch battery before it is immersed in deionized water, and ρ is the density of deionized water (1g / L). The volume V before cycling was measured respectively. 循环前 and the volume V after the cycle 循环后 The cyclic gas production is calculated using the following formula: (V 循环后 -V 循环前 ) / V 循环前 ×100%.

[0117] (4) High temperature storage: Charge the cells after capacity division to 100% SOC at 0.33C, and record its capacity as C0. Then, store the fully charged battery in a 60℃ oven for 7 days. Test the capacity of the cells after storage and record it as C1. Then, the capacity retention rate (%) after 7 days of storage at 60℃ is (C1-C0) / C0×100%.

[0118] The specific test results are shown in the table below:

[0119] Table 1

[0120]

[0121] As can be seen from the data in the table above, the embodiments can achieve a balance between high-temperature cycling and high-temperature storage performance compared to the comparative examples. This indicates that the compound additive with the structure shown in formula (I) can effectively improve the high-temperature cycling and high-temperature storage performance of lithium-ion batteries, as well as suppress the growth of cycle DCR and cycle gas generation. Its mass percentage is preferably 0.1-2%.

[0122] Compared with Example 1, Comparative Examples 2 and 3 showed worse overall performance. This is attributed to the fact that when the selected additive structure contains only siloxane groups and no alkynyl groups, its reactivity decreases, the film is not sufficiently dense, and the film stability deteriorates. When the selected additive structure contains only alkynyl groups and no siloxane groups, an organic-dominated interface film is formed, resulting in higher film impedance and poorer thermal stability. In other words, only when the defined additive structure contains both alkynyl and siloxane functional groups can a dense, high-ionic-conductivity stable interface film be formed through their synergistic effect, thereby improving the high-temperature stability of lithium batteries.

[0123] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A non-aqueous electrolyte, characterized in that, It includes lithium salts, organic solvents, and additives, wherein the additives include compounds with structures specifically shown in formula (I): R1-R6 are each independently derived from hydrogen, halogen, C1-C8 alkyl, C1-C8 haloalkyl, C1-C8 alkenyl, C1-C8 alkynyl, substituted or unsubstituted aromatic group, heterocycle containing at least one heteroelement of S, N, and O, silyl, siloxane, siloxamine, carbonyl, or any combination thereof, and at least one of R1-R5 includes an alkynyl group.

2. The non-aqueous electrolyte according to claim 1, characterized in that, R1-R6 are each independently derived from hydrogen, C1-C8 alkyl, C1-C8 alkynyl, C6-C9 substituted or unsubstituted aromatic group, C3-C7 S-containing heterocycle, C1-C8 silyl, C1-C8 siloxane, C1-C8 siloxamine, and C1-C8 carbonyl; wherein the substituents in the substituted aromatic group include halogens, and any combination of C1-C4 alkyl groups.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The additive includes compounds having any of the following structures:

4. The non-aqueous electrolyte according to any one of claims 1-3, characterized in that, The content of the compound shown in formula (I) is 0.1%-2% based on the total mass of the non-aqueous electrolyte.

5. The non-aqueous electrolyte according to any one of claims 1-3, characterized in that, The molar concentration of the lithium salt is 0.7-1.5 mol / L; And / or, the lithium salt includes at least one of LiPF6, LiClO4, LiBF4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI, and LiTDI.

6. The non-aqueous electrolyte according to any one of claims 1-3, characterized in that, The non-aqueous electrolyte also includes other functional additives, including positive and negative electrode film-forming additives. And / or, based on the total mass of the non-aqueous electrolyte, the amount of the other functional additives added is 0.5%-10%.

7. The non-aqueous electrolyte according to claim 6, characterized in that, The positive and negative electrode film-forming additives include at least one of the following: additives containing S or double bonds, or F, or B, or P or CN, or lithium salt additives.

8. The non-aqueous electrolyte according to any one of claims 1-3, characterized in that, The organic solvent includes at least one of carbonate solvents or carboxylic acid ester solvents.

9. A lithium-ion battery, characterized in that, Includes the non-aqueous electrolyte as described in any one of claims 1-8.

10. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 9.

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