Applications of polyazine compounds in electrolytes, as well as electrolytes, their preparation methods and applications, lithium-ion batteries and electrical equipment.

Abstract

This invention relates to the field of lithium batteries and discloses the application of a polyazine compound in an electrolyte, wherein the polyazine compound has the structure shown in formula (1), wherein V1 and V2 are each independently selected from C or N; wherein R1, R2, R4 and R5 are each independently selected from H, substituted or unsubstituted C1 to C2. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 A ketone or ester group, or R4 and R5 combined with their respective attached N atoms, forms a six-membered nitrogen heterocycle containing two N atoms; wherein R3 and R6 are each independently selected from H, or R3 and R6 each independently form a carbonyl group with their respective attached C atoms. Applying an electrolyte containing the aforementioned polyazine compound to a lithium battery can reduce battery impedance and improve the cycle stability of the ternary cathode under high voltage.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, specifically to an electrolyte, its preparation method, and its application. Background Technology

[0002] Ternary cathode materials, with their higher theoretical specific capacity, have long been a focus of industry attention. Among them, ternary materials are particularly favored due to their higher charging cut-off voltage (up to 4.5V), which significantly improves battery energy density. However, existing electrolyte systems, based on carbonate solvents and lithium hexafluorophosphate, are prone to oxidative decomposition at the high voltage of 4.5V, generating byproducts, increasing cathode impedance, and accelerating electrolyte consumption. Simultaneously, acidic impurities in the electrolyte can cause metal dissolution from the cathode material and structural collapse, leading to decreased battery energy density and deteriorated cycle performance.

[0003] To address this problem, there are currently three main solutions: First, use organic solvents with higher oxidation potentials to replace or partially replace carbonate solvents, such as sulfones and nitriles; second, use lithium salts with better stability and no byproducts (such as hydrofluoric acid) to replace or partially replace lithium hexafluorophosphate, such as lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); third, use cathode film-forming additives, such as a fluorinated additive disclosed in CN104282939A and a phosphate ester additive disclosed in US20120009485A1P.

[0004] The non-carbonate solvents in Scheme 1 have a low dielectric constant, which is unfavorable for lithium-ion transport and makes them prone to reduction at the negative electrode. The lithium salts in Scheme 2 are prone to corroding the aluminum current collector under high voltage. The challenge of Scheme 3 lies in finding suitable high-voltage additives that can form a stable solid-state interfacial film on the positive electrode surface. Fluorinated additives, for example, are expensive, and due to the presence of fluorine atoms, they easily generate acid in the electrolyte, inducing metal dissolution from the positive electrode; furthermore, fluorinated additives are often not stable enough at high temperatures.

[0005] Therefore, it is necessary to develop an electrolyte that can reduce battery impedance and improve the cycling stability of ternary cathodes under high voltage. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of high battery impedance and poor cycle stability of ternary cathode under high voltage in the prior art, and to provide an electrolyte, its preparation method and application.

[0007] To achieve the above objectives, a first aspect of the present invention provides the application of a polyazine compound in an electrolyte, wherein the polyazine compound has the structure shown in formula (1):

[0008]

[0009] V1 and V2 are each independently selected from C or N;

[0010] Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms;

[0011] R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

[0012] A second aspect of the present invention provides an electrolyte, wherein the electrolyte comprises solvent A, solvent B, lithium salt, polyazine compound, and optional nonazine additive;

[0013] The polyazine compound has the structure shown in formula (1):

[0014]

[0015] V1 and V2 are each independently selected from C or N;

[0016] Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms;

[0017] R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

[0018] A third aspect of the present invention provides a method for preparing an electrolyte, the method comprising:

[0019] Lithium salt, polyazine compound, and optional nonazine additive are added to a solvent to obtain an electrolyte.

[0020] The fourth aspect of the present invention provides an electrolyte prepared by the preparation method described in the third aspect of the present invention.

[0021] The fifth aspect of the present invention provides an application of the electrolyte described in the second and fourth aspects of the present invention in a lithium-ion battery.

[0022] A sixth aspect of the present invention provides a lithium battery comprising the electrolyte described in the second and fourth aspects of the present invention.

[0023] A seventh aspect of the present invention provides an electrical device, including the lithium-ion battery described in the sixth aspect of the present invention; wherein the electrical device includes vehicles and digital products, preferably selected from pure electric vehicles, hybrid electric vehicles, electric bicycles, and laptops.

[0024] Through the above technical solution, the present invention can produce the following beneficial effects:

[0025] 1. The polyazine compounds of this invention have multiple nitrogen atoms in their six-membered rings, forming nitrogen-nitrogen single bonds with low bond energies of approximately 200 kJ / mol, far lower than carbon-carbon single bonds (approximately 346 kJ / mol) and carbon-oxygen single bonds (356 kJ / mol). Therefore, they are more likely to undergo electrochemical reactions and break bonds on the electrode surface of a battery. In other words, the molecular structure of this invention will preferentially undergo electrochemical reactions at the positive and negative electrodes compared to carbonate molecules, especially ethylene carbonate (EC), and the reaction products will form a solid electrolyte interface film.

[0026] 2. Because the polyazine compounds of this invention are rich in nitrogen atoms, they can generate a large amount of Li3N after undergoing an electrochemical reaction on the electrode surface. Li3N has extremely high ionic conductivity (1.3 × 10⁻⁶). -5 The ionic conductivity of Li₂CO₃ generated by the reduction of EC is only 1 × 10⁻⁶ S / cm, while that of the other two is only 1 × 10⁻⁶ S / cm. -8 The S / cm ratio is much lower than that of Li3N. Therefore, the interfacial film formed by the polyazine compounds is more conducive to lithium ion conduction and reduces battery impedance.

[0027] 3. When ternary materials are charged to 4.5V, a large number of tetravalent nickel ions are formed. High-valence metal ions have strong oxidizing properties, which will oxidize carbonate solvents, consume active lithium and electrolyte, and ultimately lead to rapid capacity decay. The polyazine compounds mentioned above have multiple nitrogen atoms, and the lone pairs of electrons on the nitrogen atoms provide complexation sites. The six-membered rings provide space for complexing metal ions. Therefore, they can efficiently capture the tetravalent nickel ions dissolved from the cathode due to high voltage and the acidity of the electrolyte in the electrolyte, forming structurally stable organometallic chelates. This prevents the ions from oxidizing the electrolyte, reduces the generation of by-products in the battery system, and improves the cycle stability of the ternary cathode under high voltage.

[0028] 4. Due to the substitution of alkyl groups on the nitrogen atom, the polyazine compounds have good compatibility with the electrolyte bulk (organic carbonate molecules) and can be used in different electrolyte systems, thus having universality.

[0029] The combined effects listed above enable the polyazine compounds of the present invention to effectively improve the battery performance when added to the electrolyte of ternary high-voltage batteries.

[0030] The polyazine compounds of this invention are targeted at ternary materials, such as LiNi. 0.5 Co 0.2 Mn 0.3 O2 (NCM523 type), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622 type), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811 type), LiNi 0.85 Co 0.075 Mn 0.075 O2; the negative electrode can be artificial graphite, natural graphite, mesophase carbon microspheres (MCMB), silicon-carbon negative electrode, etc.

[0031] The polyazine compounds of the present invention have a much higher Li3N content during negative electrode film formation than during positive electrode film formation, which is more conducive to the conduction and intercalation of lithium ions on the negative electrode side. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] In this invention, the terms used are uniformly interpreted as follows:

[0034] Polyazine compounds refer to six-membered heterocyclic compounds containing 2-4 nitrogen atoms.

[0035] As previously stated, the first aspect of the present invention provides the application of a polyazine compound in an electrolyte, wherein the polyazine compound has the structure shown in formula (1):

[0036]

[0037] V1 and V2 are each independently selected from C or N;

[0038] Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms;

[0039] R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

[0040] Preferably, V1 is C and V2 is N; or both V1 and V2 are N.

[0041] R1, R2, R4 and R5 are each independently selected from H, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C2 to C8 alkenyl, substituted or unsubstituted C2 to C8 alkynyl, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C8 ketone or ester, or R4 and R5 combined with their respective attached N atoms to form a six-membered nitrogen heterocycle containing two N atoms.

[0042] More preferably, the polyazine compound is selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-dimethyl-2,5-bis(phenylmethyl)-1,2,4,5-tetraazine, 1,2,3,4,5,6 - Hexamethyl-1,2,4,5-tetraazine, 2,3-dimethyloctahydropyridazine[1,2-a]-1,2,4,5-tetraazine, 1,5-dimethyl-2,4-bis(phenylmethyl)-1,2,4,5-tetraazine-3,6-dione, 1,2,4,5-tetraazine-3,6-dione, hexahydro-1,2-dimethylpyridazine, or hexahydro-1,2,4-trimethyl-1,2,4-triazine.

[0043] According to a particularly preferred embodiment of the present invention, the polyazine compound is selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, or 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine.

[0044] In the polyazine compounds, the bond energy of the nitrogen-nitrogen single bond is less than 356 kJ / mol, preferably less than 346 kJ / mol, and more preferably 200 kJ / mol.

[0045] A second aspect of the present invention provides an electrolyte, wherein the electrolyte comprises solvent A, solvent B, lithium salt, polyazine compound, and optional nonazine additive;

[0046] The polyazine compound has the structure shown in formula (1):

[0047]

[0048] V1 and V2 are each independently selected from C or N;

[0049] Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms;

[0050] R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

[0051] Preferably, V1 is C and V2 is N; or both V1 and V2 are N.

[0052] R1, R2, R4 and R5 are each independently selected from H, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C2 to C8 alkenyl, substituted or unsubstituted C2 to C8 alkynyl, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C8 ketone or ester, or R4 and R5 combined with their respective attached N atoms to form a six-membered nitrogen heterocycle containing two N atoms.

[0053] More preferably, the polyazine compound is selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-dimethyl-2,5-bis(phenylmethyl)-1,2,4,5-tetraazine, 1,2,3,4,5,6 - Hexamethyl-1,2,4,5-tetraazine, 2,3-dimethyloctahydropyridazine[1,2-a]-1,2,4,5-tetraazine, 1,5-dimethyl-2,4-bis(phenylmethyl)-1,2,4,5-tetraazine-3,6-dione, 1,2,4,5-tetraazine-3,6-dione, hexahydro-1,2-dimethylpyridazine or hexahydro-1,2,4-trimethyl-1,2,4-triazine;

[0054] According to a particularly preferred embodiment of the present invention, the polyazine compound is selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, or 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine.

[0055] The lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, or lithium perchlorate; preferably lithium hexafluorophosphate.

[0056] Preferably, solvent A is selected from cyclic carbonates, more preferably from ethylene carbonate, propylene carbonate, and 1,2-butenyl carbonate; more preferably from ethylene carbonate.

[0057] Preferably, solvent B is selected from linear carbonates, more preferably from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate; more preferably from methyl ethyl carbonate.

[0058] Preferably, the nonazine additive is selected from propylene sulfite, 1,3-propenesulfonyl lactone (PST), vinylene sulfate (DTD), and ethylene methane disulfonate (MMDS); more preferably, it is propylene sulfite.

[0059] Wherein, based on the total amount of the electrolyte, the mass concentration of solvent A is 25-35%; the mass concentration of solvent B is 50-65%; the mass concentration of polyazine compound is 0.1-10%, preferably 0.5-3%; the mass concentration of lithium salt is 6-15%; and the mass concentration of nonazine additive is 0-5%.

[0060] The mass ratio of solvent A to solvent B is 1:(1-3); preferably 1:(2-2.5). An appropriate mass ratio allows the solvent system formed by solvent A and solvent B to achieve both low viscosity and high dielectric constant, resulting in an electrolyte with good conductivity.

[0061] A third aspect of the present invention provides a method for preparing an electrolyte, the method comprising:

[0062] Lithium salt, polyazine compound, and optional nonazine additive are added to a solvent to obtain an electrolyte.

[0063] In some embodiments of the present invention, preferably, the lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, or lithium perchlorate; more preferably, it is lithium hexafluorophosphate.

[0064] In some embodiments of the present invention, preferably, the polyazine compound has the structure shown in formula (1):

[0065]

[0066] V1 and V2 are each independently selected from C or N;

[0067] Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms;

[0068] In this case, R3 and R6 are each independently selected from H, or R3 and R6 each independently form a carbonyl group with their respective C atoms;

[0069] In some embodiments of the present invention, preferably, the nonazine additive is selected from propylene sulfite, 1,3-propenesulfonyl lactone (PST), vinylene sulfate (DTD), and ethylene methane disulfonate (MMDS); more preferably, it is propylene sulfite.

[0070] In some embodiments of the present invention, preferably, the solvent is a mixed solvent made of solvent A and solvent B; preferably, the mass ratio of solvent A to solvent B is 1:(1-3); more preferably, it is 1:(2-2.5).

[0071] In some embodiments of the present invention, preferably, by weight, solvent A is 25-35 parts; solvent B is 50-65 parts; lithium salt is 6-15 parts; polyazine compound is 0.1-10 parts, preferably 0.5-3 parts; and nonazine additive is 0-5 parts.

[0072] The fourth aspect of the present invention provides an electrolyte prepared by the preparation method described in the third aspect of the present invention.

[0073] The fifth aspect of the present invention provides an application of the electrolyte described in the second and fourth aspects of the present invention in a lithium-ion battery.

[0074] A sixth aspect of the present invention provides a lithium battery comprising the electrolyte described in the second and fourth aspects of the present invention.

[0075] The lithium battery includes a positive electrode and a negative electrode.

[0076] The positive electrode contains a ternary material as its active material; a solid electrolyte interphase (SEI) film can be formed on the surface of the negative electrode; and the solid electrolyte interphase (SEI) film is composed of Li3N.

[0077] A seventh aspect of the present invention provides an electrical device, including the lithium-ion battery described in the sixth aspect of the present invention; wherein the electrical device includes vehicles and digital products, preferably selected from pure electric vehicles, hybrid electric vehicles, electric bicycles, and laptops.

[0078] The present invention will be described in detail below through examples. In the following examples, the raw materials ethylene carbonate and methyl ethyl carbonate are commercially available products from Shenzhen Capchem Technology Co., Ltd.; the raw material lithium hexafluorophosphate is a commercially available product from Do-Fluoride Chemicals Co., Ltd.; and the polyazine compound raw material is a commercially available product from Honey Joy Holdings Limited.

[0079] Example 1

[0080] (1) Preparation of electrolyte

[0081] 30g of ethylene carbonate (EC) and 70g of ethyl methyl carbonate (EMC) were mixed to form a mixed solvent. 14.4g of lithium hexafluorophosphate was then added to the mixed solvent. Next, 2.32g (2% by mass) of 1,2,4,5-tetramethyl-1,2,4,5-tetraazine (as shown in Formula 2) was added. The electrolyte is denoted as I1.

[0082]

[0083] (2) Battery manufacturing

[0084] Carbon-coated silicon material, conductive agent super-p, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in a mass ratio of 100:2:2:3. The resulting paste is uniformly coated onto copper foil, which serves as the negative electrode current collector, and dried in a vacuum oven at 60°C for 24 hours to obtain the negative electrode sheet.

[0085] The positive electrode uses LiNi 0.5 Co 0.2 Mn 0.3 O2, i.e. NCM523 type, is made by mixing NCM523, carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) in a mass ratio of 100:2:2. The resulting paste is uniformly coated on aluminum foil, which serves as the positive electrode current collector, and dried in a vacuum oven at 60°C for 24 hours to obtain the positive electrode sheet.

[0086] Pouch cell fabrication: A silicon-based pouch lithium battery with a negative electrode, model SL523450, was prepared by winding. In an argon glove box with water and oxygen contents both less than 5 ppm, 3 g of electrolyte I1 was injected into the pouch cell with an air bladder to prepare battery P1 for cycle testing.

[0087] Formation process: The simulated battery is first charged to 1.5V with a current of 45mA (0.05C) and held at 1.5V for 10 hours to allow the electrolyte to fully wet the battery electrodes. After sufficient aging, the battery is first charged with a smaller current of 9mA (C / 100) for 15 hours to form a stable and complete SEI film, then charged to 4.5V with a current of 45mA (0.05C), and then discharged to 3V.

[0088] Example 2

[0089] The electrolyte was prepared using the same method as in Example 1, except that the additive was 2.32 g (2% by mass) of 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine (as shown in Formula 3), resulting in electrolyte I2. The battery fabrication and formation process were the same as in Example 1, yielding a pouch cell P2.

[0090]

[0091] Example 3

[0092] The electrolyte was prepared using the same method as in Example 1, except that the additive was 2.32 g (2% by mass) of 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine (as shown in Formula 4), resulting in electrolyte I3. The battery fabrication and formation processes were the same as in Example 1, yielding a pouch cell P3.

[0093]

[0094] Example 4

[0095] The electrolyte was prepared using the same method as in Example 1, except that 2.32 g (2% by mass) of 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine (as shown in Formula 5) was added as an additive to obtain electrolyte I4. The battery fabrication and formation process were the same as in Example 1, and a pouch battery P4 was prepared.

[0096]

[0097] Example 5

[0098] The electrolyte was prepared using the same method as in Example 1, except that the additives were 2.32 g (2% by mass) of 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine (as shown in Formula 5) and 1.16 g (1% by mass) of 1,3-propanesulfonyl lactone (PS), resulting in electrolyte I5. The battery fabrication and formation process were the same as in Example 1, yielding a pouch cell P5.

[0099] Example 6

[0100] The electrolyte was prepared using the same method as in Example 1, except that the additive was 2.32 g (2% by mass) of 1,2,4,5-tetraazine-3,6-dione (as shown in Formula 6, with an active hydrogen atom attached to the nitrogen atom in the six-membered ring), resulting in electrolyte I6. The battery fabrication and formation process were the same as in Example 1, yielding battery P6.

[0101]

[0102] Example 7

[0103] The electrolyte was prepared using the same method as in Example 1, except that the additive was 2.32 g (2% by mass) of 1,4-dimethyl-2,5-bis(phenylmethyl)-1,2,4,5-tetraazine (structure shown in Formula 7, with a large group attached to the nitrogen atom in the six-membered ring), resulting in electrolyte I7. The battery fabrication and formation process were the same as in Example 1, yielding battery P7.

[0104]

[0105] Example 8

[0106] The electrolyte was prepared using the same method as in Example 1, except that 2.32 g (2% by mass) of hexahydro-1,2-dimethylpyridazine (as shown in Formula 8, containing two nitrogen atoms in a six-membered ring) was added to obtain electrolyte I8. The battery fabrication and formation process were the same as in Example 1, and battery P8 was prepared.

[0107]

[0108] Example 9

[0109] The electrolyte was prepared using the same method as in Example 1, except that the additive was 2.32 g (2% by mass) of hexahydro-1,2,4-trimethyl-1,2,4-triazine (as shown in Formula 9, containing three nitrogen atoms in a six-membered ring), resulting in electrolyte I9. The battery fabrication and formation process were the same as in Example 1, yielding battery P9.

[0110]

[0111] Comparative Example 1

[0112] The electrolyte was prepared using the same method as in Example 1, except that no additives were used, resulting in electrolyte R1. The battery fabrication and formation process was the same as in Example 1, resulting in battery RP1.

[0113] Comparative Example 2

[0114] The electrolyte was prepared using the same method as in Example 5, except that only 1.16 g (1% by mass) of 1,3-propanesulfonyl lactone (PS) was added to obtain electrolyte R2. The battery fabrication and formation process was the same as in Example 1, resulting in battery RP2.

[0115] Fully charged high-temperature storage test

[0116] The electrolyte compositions in Examples 1-9 and Comparative Examples 1-3 are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] After the batteries P1-P9 and RP1-RP2 were formed, they were charged at 0.5C (450mA) with a cutoff voltage of 4.5V, followed by constant voltage charging at 4.5V with a cutoff current of 45mA. The fully charged batteries were stored in a 60℃ constant temperature oven for 5 days, with 10 batteries under each condition, and the average value was taken. The thickness of the batteries before and after storage was measured using vernier calipers. The battery expansion rate (%) was calculated by subtracting the thickness before storage from the thickness after storage, and then dividing the difference by the thickness before storage to obtain the percentage. The experimental results are shown in Table 2.

[0121] Table 2

[0122] Electrolyte number Volume expansion rate (%) I1 23 I2 35 I3 32 I4 21 I5 17 I6 52 I7 44 I8 58 I9 54 R1 79 R2 66

[0123] (2) Nickel leaching test

[0124] After disassembling the batteries, the positive and negative electrode separators and aluminum-plastic film were repeatedly rinsed with 5 mL of propylene glycol ester. The washing solution was then sent to an inductively coupled plasma optical transilluminator (ICP) for testing. The instrument used was an ICP-based instrument manufactured by Thermo Fisher Scientific, and the testing conditions were familiar to most testers. Ten batteries were tested under each condition, and the average value of the results was taken. The experimental results are shown in Table 3.

[0125] Table 3

[0126]

[0127]

[0128] (3) Battery high-voltage cycle test

[0129] After the formation of each battery (P1-P9 and RP1-RP2) was completed, the air bladders were removed and the batteries were vacuum-sealed. They were then cycled 200 times at 1C (900mA) between 3V and 4.5V (10 batteries under each condition, and the average value was taken). All tests were conducted in a 45℃ constant temperature chamber. The capacity retention rate (%) was calculated by dividing the discharge capacity at the 200th cycle by the initial discharge capacity at the first cycle. The experimental results are shown in Table 4.

[0130] Table 4

[0131] Electrolyte number Capacity retention rate (%) I1 68 I2 60 I3 61 I4 71 I5 78 I6 62 I7 51 I8 44 I9 50 R1 30 R2 35

[0132] As shown in Table 2, the film-forming additive of this invention significantly reduces the expansion rate of high-nickel ternary batteries during full-charge, high-temperature storage. This indicates that it successfully forms a solid electrolyte interface film on the electrode surface, prioritizing EC over EC, thereby protecting the electrolyte, reducing the continuous occurrence of side reactions, and reducing gas generation. Therefore, it reduces the expansion rate during battery storage and improves the battery's high-temperature safety. The cycle performance test results in Table 4 also confirm this point. Furthermore, the results of Example 5 (electrolyte I5) demonstrate that the additive of this invention, when used in combination with PS, has a better effect. The results of Comparative Example 1 (electrolyte R1) show that without the additive, the battery cycle performance of the high-voltage cathode material is extremely poor. This is mainly because the dissolution of cathode metal ions under high voltage cannot be suppressed, which is detrimental to battery life.

[0133] As shown in Table 3, the additives of this invention, due to their excellent metal ion complexing effect, can reduce the dissolution of nickel metal during high-temperature battery storage. In Examples 2 and 3 (electrolytes I2 and I3), the presence of acyl groups on the nitrogen atom reduces the electron cloud density of the six-membered ring in the polyazine compound due to its electron-withdrawing effect, resulting in a slightly weaker complexing effect on metal ions and more nickel metal dissolving from the battery. Example 6 (electrolyte I6) shows better results primarily due to the presence of active hydrogen on the nitrogen atom, which increases the acidity of the electrolyte. However, Example 7 (electrolyte I7) suffers from excessively large substituents on the nitrogen atom, leading to excessive steric hindrance, resulting in a less effective complexing effect on metal ions compared to the other examples. Furthermore, the six-membered rings in Examples 8 and 9 contain only two and three nitrogen atoms respectively, resulting in fewer lone pairs of electrons and a weaker complexing effect on metal ions compared to tetrazine molecules, thus leading to more nickel metal dissolving.

[0134] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a polyazine compound in an electrolyte, wherein, The polyazine compounds have the structure shown in formula (1): V1 and V2 are each independently selected from C or N; Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms; R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

2. The application according to claim 1, wherein, V1 is C, and V2 is N; or both V1 and V2 are N. R1, R2, R4 and R5 are each independently selected from H, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C2 to C8 alkenyl, substituted or unsubstituted C2 to C8 alkynyl, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C8 ketone or ester, or R4 and R5 are combined with their respective attached N atoms to form a six-membered nitrogen heterocycle containing two N atoms.

3. The application according to claim 1 or 2, wherein, The polyazine compounds are selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-dimethyl-2,5-bis(phenylmethyl)-1,2,4,5-tetraazine, and 1,2,3,4,5,6-hexamethylenetetraazine. Hexahydro-1,2,4,5-tetraazine, 2,3-dimethyloctahydropyridazine[1,2-a]-1,2,4,5-tetraazine, 1,5-dimethyl-2,4-bis(phenylmethyl)-1,2,4,5-tetraazine-3,6-dione, 1,2,4,5-tetraazine-3,6-dione, hexahydro-1,2-dimethylpyridazine, or hexahydro-1,2,4-trimethyl-1,2,4-triazine.

4. The application according to claim 1 or 2, wherein, The polyazine compounds are selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, or 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine.

5. An electrolyte, wherein, The electrolyte includes solvent A, solvent B, lithium salt, and polyazine compound; The polyazine compound has the structure shown in formula (1): V1 and V2 are each independently selected from C or N; Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms; R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

6. The electrolyte according to claim 5, wherein, V1 is C, and V2 is N; or both V1 and V2 are N. R1, R2, R4 and R5 are each independently selected from H, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C2 to C8 alkenyl, substituted or unsubstituted C2 to C8 alkynyl, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C8 ketone or ester, or R4 and R5 are combined with their respective attached N atoms to form a six-membered nitrogen heterocycle containing two N atoms.

7. The electrolyte according to claim 5 or 6, wherein, The polyazine compounds are selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-dimethyl-2,5-bis(phenylmethyl)-1,2,4,5-tetraazine, and 1,2,3,4,5,6-hexamethylenetetraazine. Hexahydro-1,2,4,5-tetraazine, 2,3-dimethyloctahydropyridazine[1,2-a]-1,2,4,5-tetraazine, 1,5-dimethyl-2,4-bis(phenylmethyl)-1,2,4,5-tetraazine-3,6-dione, 1,2,4,5-tetraazine-3,6-dione, hexahydro-1,2-dimethylpyridazine, or hexahydro-1,2,4-trimethyl-1,2,4-triazine.

8. The electrolyte according to claim 5 or 6, wherein, The polyazine compounds are selected from 1,2,4,5-tetramethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-dimethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, 1,4-diacetyl-2,5-diethyl-1,2,4,5-tetraazine, or 1,2,3,4,5,6-hexamethyl-1,2,4,5-tetraazine.

9. The electrolyte according to claim 5 or 6, wherein, The lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, or lithium perchlorate.

10. The electrolyte according to claim 9, wherein, The lithium salt is lithium hexafluorophosphate.

11. The electrolyte according to claim 5 or 6, wherein, Solvent A is selected from cyclic carbonates.

12. The electrolyte according to claim 11, wherein, Solvent A is selected from ethylene carbonate, propylene carbonate, and 1,2-butene carbonate.

13. The electrolyte according to claim 11, wherein, Solvent A is ethylene carbonate.

14. The electrolyte according to claim 5 or 6, wherein, The solvent B is selected from linear carbonates.

15. The electrolyte according to claim 14, wherein, The solvent B is selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

16. The electrolyte according to claim 14, wherein, Solvent B is methyl ethyl carbonate.

17. The electrolyte according to claim 5 or 6, wherein, The electrolyte also includes nonazine additives.

18. The electrolyte according to claim 17, wherein, The nonazine additives are selected from propylene sulfite, 1,3-propenesulfonyl lactone, vinylene sulfate, and ethylene disulfonate.

19. The electrolyte according to claim 17, wherein, The nonazine additive is propylene sulfite.

20. The electrolyte according to claim 17, wherein, Based on the total amount of the electrolyte, the mass concentration of solvent A is 25-35%; the mass concentration of solvent B is 50-65%; the mass concentration of polyazine compound is 0.1-10%; the mass concentration of lithium salt is 6-15%; and the mass concentration of nonazine additive is 0-5%.

21. The electrolyte according to claim 20, wherein, Based on the total amount of the electrolyte, the mass concentration of the polyazine compound is 0.5-3%.

22. The electrolyte according to claim 5 or 6, wherein, The mass ratio of solvent A to solvent B is 1:(1-3).

23. The electrolyte according to claim 22, wherein, The mass ratio of solvent A to solvent B is 1:(2-2.5).

24. A method for preparing an electrolyte, the method comprising: A lithium salt and a polyazine compound are added to a solvent to obtain an electrolyte; wherein, The polyazine compounds have the structure shown in formula (1): V1 and V2 are each independently selected from C or N; Among them, R1, R2, R4, and R5 are each independently selected from H, substituted or unsubstituted C1 to C1. 10 Alkyl, substituted or unsubstituted C2 to C 10 Alkenyl, substituted or unsubstituted C2 to C 10 Alkyne, substituted or unsubstituted phenyl, substituted or unsubstituted C2 to C 10 The ketone or ester group, or R4 and R5 combined with their respective attached N atoms, form a six-membered nitrogen heterocycle containing two N atoms; R3 and R6 are each independently selected from H, or R3 and R6 independently form a carbonyl group with their respective C atoms.

25. The method according to claim 24, wherein, The lithium salt is selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, or lithium perchlorate.

26. The method according to claim 24 or 25, wherein, The lithium salt is lithium hexafluorophosphate.

27. The method according to claim 24, wherein, The method also includes adding nonazine additives to the solvent.

28. The method according to claim 27, wherein, The nonazine additives are selected from propylene sulfite, 1,3-propenesulfonyl lactone, vinylene sulfate, and ethylene disulfonate.

29. The method according to claim 27, wherein, The nonazine additive is propylene sulfite.

30. The method according to claim 27, wherein, The solvent is a mixture of solvent A and solvent B.

31. The method according to claim 30, wherein, The mass ratio of solvent A to solvent B is 1:(1-3).

32. The method according to claim 30, wherein, The mass ratio of solvent A to solvent B is 1:(2-2.5).

33. The method according to claim 30, wherein, By weight, solvent A is 25-35 parts; solvent B is 50-65 parts; lithium salt is 6-15 parts; polyazine compound is 0.1-10 parts; and nonazine additive is 0-5 parts.

34. The method according to claim 33, wherein, The polyazine compound is 0.5-3 parts by weight.

35. The electrolyte prepared by the method according to any one of claims 24-34.

36. A lithium-ion battery comprising the electrolyte according to any one of claims 6-23 and 35.

37. An electrical device comprising the lithium-ion battery of claim 36; wherein, Among the electrical equipment mentioned above The electrical equipment includes vehicles and digital products.

38. The electrical equipment according to claim 37, wherein, The electrical equipment is selected from pure electric vehicles, hybrid electric vehicles, electric bicycles, and laptops.

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