High-voltage additive for lithium battery electrolyte, electrolyte and lithium ion battery

Abstract

The invention relates to a high-voltage additive for a lithium battery electrolyte, the electrolyte and a lithium ion battery, and belongs to the technical field of lithium batteries. The invention discloses a high-voltage additive for a lithium battery electrolyte. The addition amount of the high-voltage additive in the lithium battery electrolyte is 0.1-15 wt%; the high-voltage additive is a pyridine compound, and the pyridine compound structurally comprises a nitro group, a hydroxyl group and an R1 group; r1 comprises any one of a halogen group, an alkane group, an alkoxy group, a fluoroalkane group, a halogenated hydrocarbon group, an alkylene group, an alkyne group, a cyano group (-CN), an amino group (-NH2), a halogenated alkylene group, a halogenated alkyne group, an aryl group and a heterocyclic aryl group. The invention further discloses a high-voltage-resistant lithium battery electrolyte containing the high-voltage additive and a high-voltage-resistant lithium ion battery. The high-voltage additive can remarkably improve 4.6 V circulation and rate capability of the lithium ion battery.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium batteries and relates to a high-voltage additive for lithium battery electrolyte and the electrolyte and a lithium ion battery. Background Art

[0002] Lithium-ion batteries are widely used in electric vehicles, consumer electronic devices, and energy storage due to their high energy density, high working efficiency, environmental friendliness, long cycle life, and no memory effect. With the expansion of the application scope of lithium-ion batteries, higher requirements are put forward for the energy density of lithium-ion batteries, such as lighter and longer working time wearable medical devices, smarter and more portable 3C electronic products, which requires the energy density and performance of lithium-ion batteries to be continuously improved.

[0003] The electrolyte is an important component of the battery, and it is responsible for transferring ions between the positive and negative electrodes through the battery. It has an important impact on the battery's capacity, operating voltage range, cycle performance, and safety performance. In order to implement high energy density of lithium-ion batteries, improving existing cathode materials is the mainstream technical solution, and developing electrolytes that are compatible with high-voltage cathodes is the key to achieving increased energy density of lithium-ion batteries.

[0004] The most widely used electrolyte system is LiPF 6 The lithium salt is dissolved in a carbonate organic solvent. It is severely oxidatively decomposed under high pressure and cannot be adapted to high-voltage positive electrode materials. When the voltage is >4.3V (vs.Li+ / Li), components such as EC and PF6- in the electrolyte are very prone to oxidative decomposition. Continuous reaction will cause the continuous deposition of decomposition products, making the electrode electrolyte interface thicker and uneven, resulting in increased interface impedance and affecting the lithium ion kinetics. In addition, high voltage will promote the reaction of PF6- with trace amounts of water in the electrolyte to generate highly corrosive hydrogen fluoride, which will destroy the positive electrode electrolyte interface (CEI), accelerate transition metal dissolution and oxygen release, and thus lead to poor electrochemical performance of nickel-rich materials under high pressure. Therefore, it is urgent to develop a high-voltage resistant lithium-ion battery electrolyte. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to propose a high voltage additive that can be applied to lithium battery electrolyte. The battery assembled from the lithium battery electrolyte containing the high voltage additive has good electrochemical performance.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A high voltage additive for lithium battery electrolyte, wherein the amount of the high voltage additive added to the lithium battery electrolyte is 0.1 to 15 wt%;

[0008] The high voltage additive is a pyridine compound, the structure of which includes nitro, hydroxyl, R 1 base;

[0009] The R 1 Including halogen, alkane, alkoxy, fluoroalkane, halogenated alkyl, alkene, alkyne, cyano (-CN), amino (-NH 2 ), any one of a halogenated alkene group, a halogenated alkynyl group, an aromatic group, and a heterocyclic aromatic group.

[0010] The high voltage additive of the present invention is a pyridine compound containing a carbonyl group, a nitro group and an R group. Both the carbonyl group and the nitro group are strong electron-withdrawing groups that can enhance the interaction with lithium ions and solvents. According to the relative position of the oxygen atoms in the carbonyl group and the nitro group on the pyridine six-membered ring, the Li + Coordination ability, change electrolyte conductivity, viscosity, Li + The chemical environment, carbonyl and nitro groups can complex more free solvents and ions to form a high-pressure stable solvation structure, thereby improving the oxidative stability of the electrolyte and expanding the electrochemical window of carbonate solvents.

[0011] Preferably, the high voltage additive has a general structural formula shown in formula (1) or formula (2):

[0012]

[0013] Among them, R 1 Including halogen, alkane, alkoxy, fluoroalkane, halogenated alkyl, alkene, alkyne, cyano (-CN), amino (-NH 2 ), any one of a halogenated alkene group, a halogenated alkynyl group, and an aromatic group.

[0014] In formula (1), R 1 , carbonyl (O=C) and nitro (-NO 2 ) The positions of the three substituents can be changed arbitrarily.

[0015] Preferably, the halogen group includes any one of -F, -Cl, and -Br;

[0016] The alkane group includes -CH 3 , -C 2 H 5 , -C 3 H 7 Any of the following;

[0017] The alkoxy group includes methoxy (-OCH 3 ), ethoxy (-OC 2 H 5), propoxy (-OC 3 H) any one;

[0018] The fluoroalkane group is -C n F 2n+1 , including -CF 3 , -C 2 F 5 Any of the following;

[0019] The olefin group includes -CH=CH 2 、-CH=CH-CH 3 Any of the following;

[0020] The alkynyl group includes -C 2 H, -C 3 H 3 Any of the following;

[0021] The halogenated olefin group includes -CH=CF 2 , -CF=CF 2 Any of the following;

[0022] The halogenated alkynyl groups include -C≡CF, -CH 2 -C≡CF;

[0023] The aromatic group includes -C 6 H 5 CH 2 , -C 6 H 5 , -C 6 H 4 CH 2 Any one of Cl;

[0024] In one embodiment, when R 1When it is methyl, the high voltage additive is 2-hydroxy-3-methyl-4-nitropyridine, 2-hydroxy-3-methyl-5-nitropyridine, 2-hydroxy-3-methyl-6-nitropyridine, 2-hydroxy-4-methyl-3-nitropyridine, 2-hydroxy-4-methyl-5-nitropyridine, 2-hydroxy-4-methyl-6-nitropyridine, 2-hydroxy-5-methyl-3-nitropyridine, 2-hydroxy-5-methyl-4-nitropyridine, 2-hydroxy-5-methyl-6-nitropyridine, 2-hydroxy-6-methyl-3-nitropyridine, 2-hydroxy-6-methyl-4-nitropyridine, 2-hydroxy-6-methyl-35-nitropyridine, 3-hydroxy-2-methyl-4-nitropyridine, 3-hydroxy-2-methyl-5-nitropyridine, 3-hydroxy-2-methyl-6-nitropyridine pyridine, 3-hydroxy-4-methyl-2-nitropyridine, 3-hydroxy-4-methyl-5-nitropyridine, 3-hydroxy-4-methyl-6-nitropyridine, 3-hydroxy-5-methyl-2-nitropyridine, 3-hydroxy-5-methyl-4-nitropyridine, 3-hydroxy-5-methyl-6-nitropyridine, 3-hydroxy-6-methyl-2-nitropyridine, 3-hydroxy-6-methyl-4-nitropyridine, 3-hydroxy-6-methyl-5-nitropyridine, 4-hydroxy-2-methyl-3-nitropyridine, 4-hydroxy-2-methyl-5-nitropyridine, 4-hydroxy-2-methyl-6-nitropyridine, 4-hydroxy-3-methyl-2-nitropyridine, 4-hydroxy-3-methyl-5-nitropyridine, 4-hydroxy-3-methyl-6-nitropyridine.

[0025] In one embodiment, when R 1When trifluoromethyl is used, the high voltage additive is 2-hydroxy-3-nitro-4-trifluoromethylpyridine, 2-hydroxy-3-nitro-5-trifluoromethylpyridine, 2-hydroxy-3-nitro-6-trifluoromethylpyridine, 2-hydroxy-4-nitro-3-trifluoromethylpyridine, 2-hydroxy-4-nitro-5-trifluoromethylpyridine, 2-hydroxy-4-nitro-6-trifluoromethylpyridine, 2-hydroxy-5-nitro-3-trifluoromethylpyridine , 2-hydroxy-5-nitro-4-trifluoromethylpyridine, 2-hydroxy-5-nitro-6-trifluoromethylpyridine, 2-hydroxy-6-nitro-3-trifluoromethylpyridine, 2-hydroxy-6-nitro-4-trifluoromethylpyridine, 2-hydroxy-6-nitro-35-trifluoromethylpyridine, 3-hydroxy-2-nitro-4-trifluoromethylpyridine, 3-hydroxy-2-nitro-5-trifluoromethylpyridine, 3-hydroxy-2-nitro-6-trifluoromethylpyridine Methylpyridine, 3-hydroxy-4-nitro-2-trifluoromethylpyridine, 3-hydroxy-4-nitro-5-trifluoromethylpyridine, 3-hydroxy-4-nitro-6-trifluoromethylpyridine, 3-hydroxy-5-nitro-2-trifluoromethylpyridine, 3-hydroxy-5-nitro-4-trifluoromethylpyridine, 3-hydroxy-5-nitro-6-trifluoromethylpyridine, 3-hydroxy-6-nitro-2-trifluoromethylpyridine, 3-hydroxy-6-nitro- One or more of 4-trifluoromethylpyridine, 3-hydroxy-6-nitro-5-trifluoromethylpyridine, 4-hydroxy-2-nitro-3-trifluoromethylpyridine, 4-hydroxy-2-nitro-5-trifluoromethylpyridine, 4-hydroxy-2-nitro-6-trifluoromethylpyridine, 4-hydroxy-3-nitro-2-trifluoromethylpyridine, 4-hydroxy-3-nitro-5-trifluoromethylpyridine, and 4-hydroxy-3-nitro-6-trifluoromethylpyridine.

[0026] Preferably, the high voltage additive is 2-hydroxy-5-methyl-3-nitropyridine, and its structural formula is shown in formula (3):

[0027]

[0028] A high-voltage-resistant lithium battery electrolyte comprises 0.1 to 15 wt % of a high-voltage additive for lithium battery electrolyte.

[0029] Preferably, the high voltage resistant lithium battery electrolyte comprises 1 to 3 wt % of a high voltage additive for lithium battery electrolyte.

[0030] Preferably, the high-voltage resistant lithium battery electrolyte comprises a lithium salt, an organic solvent, and a high-voltage additive for a lithium battery electrolyte;

[0031] The lithium salts include bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium difluorooxalatoborate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiFSI), lithium dioxalatoborate (LiBOB), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiDFOP) or more;

[0032] The organic solvent is a carbonate ester, including cyclic carbonate ester, chain carbonate ester, halogenated compound of cyclic carbonate ester, and halogenated compound of chain carbonate ester.

[0033] Further preferably, the cyclic carbonate includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylethylene carbonate;

[0034] The chain carbonate includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and ethyl methyl fluorocarbonate.

[0035] More preferably, the organic solvent is a mixture of a cyclic carbonate compound and a linear carbonate.

[0036] Cyclic carbonates have high dielectric constants and high ionic conductivity, and can form a stable SEI film on the negative electrode surface, but their viscosity is relatively high; chain carbonates have lower viscosity than cyclic carbonates, better electrochemical stability, and can improve the low-temperature performance of the electrolyte. The combination of the two forms a good solvent system.

[0037] Preferably, the preparation method of the high-voltage resistant lithium battery electrolyte comprises: adding a lithium salt to an organic solvent under an anhydrous inert atmosphere, stirring at 20 to 40° C. for 10 to 200 minutes and then standing for 5 to 24 hours, and then adding a high-voltage additive for lithium battery electrolyte and mixing to obtain a high-voltage resistant lithium battery electrolyte.

[0038] A high-voltage-resistant lithium-ion battery comprises a high-voltage-resistant lithium battery electrolyte.

[0039] Preferably, the positive electrode of the high-voltage-resistant lithium-ion battery is a lithium cobalt oxide electrode, and the negative electrode is a graphite electrode.

[0040] Preferably, the method for preparing the lithium cobalt oxide electrode comprises: 2 The binder polyvinylidene fluoride and the conductive agent Super- were mixed in a weight ratio of 8:1:1, N-methylpyrrolidone was added, and the mixture was stirred evenly to form a positive electrode slurry; the positive electrode slurry was evenly coated on an aluminum foil; the aluminum foil was dried at room temperature and then transferred to an oven for drying, and then rolled and cut to obtain LiCoO 2 Positive electrode.

[0041] Preferably, the preparation method of the graphite pole piece comprises: mixing the negative electrode active material graphite, the thickener sodium carboxymethyl cellulose (CMC), the binder styrene butadiene rubber (SBR), and the conductive agent Super-P in a weight ratio of 90:3:3:4, adding deionized water, and stirring evenly to form a negative electrode slurry; coating the negative electrode slurry evenly on the copper foil; drying the copper foil at room temperature and then transferring it to an oven for drying, and then rolling and cutting to obtain a graphite negative electrode sheet.

[0042] Preferably, the assembly method of the high-voltage resistant lithium-ion battery comprises: stacking the positive electrode shell, the lithium cobalt oxide pole piece, the isolation membrane, the graphite pole piece, and the negative electrode shell in order, injecting the high-voltage resistant lithium battery electrolyte, and then packaging it at a pressure of 10 to 100 MPa, and then keeping it at a constant temperature of 15 to 45 ° C for 5 to 48 hours to obtain a high-voltage resistant LiCoO 2 Button lithium-ion battery.

[0043] Preferably, the assembly method of the high-voltage-resistant lithium-ion battery includes: using a soft-pack slicer to cut the positive and negative electrode sheets, and welding aluminum tabs on the positive electrode and nickel tabs on the negative electrode; using Celgard M825 type diaphragm to 2 The positive electrode was wrapped with a diaphragm and aligned with the negative graphite electrode, then wrapped with aluminum foil and sealed with a heat sealer. Finally, 3 mL of electrolyte was added and allowed to stand for 12 hours before testing.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The high voltage additive of the present invention is a compound containing carbonyl, nitro and R 1 In pyridine compounds, carbonyl and nitro groups are strong electron-withdrawing groups that can enhance the interaction with lithium ions and solvents. The relative positions of the oxygen atoms in the carbonyl and nitro groups on the pyridine six-membered ring can be used to control the Li + Coordination ability, change electrolyte conductivity, viscosity, Li + The carbonyl and nitro groups can complex more free solvents and ions to form a high-pressure stable solvation structure, thereby improving the oxidative stability of the electrolyte and expanding the electrochemical window of carbonate solvents.

[0046] 2. The high-voltage lithium battery electrolyte of the present invention contains a high-voltage additive, and the organic solvent is a mixture of a cyclic carbonate compound and a linear carbonate. The cyclic carbonate has a higher dielectric constant and can provide high lithium ion conductivity. The linear carbonate has a low viscosity and good electrochemical stability. The two carbonate solvents are mixed to make the electrolyte have low viscosity and high conductivity, which is beneficial to improve the cycle performance and rate performance of high cut-off voltage.

[0047] 3. In the battery, the -NO 2 Functional groups such as N-pyridine rings can be preferentially oxidized or reduced on the positive and negative electrode sides of the battery to form Li-rich 3 N、LiN x O y The electrode electrolyte interface contains inorganic components such as lithium ion battery and lithium ion battery. This dense and strong electrode electrolyte interface has good electronic insulation, which can effectively inhibit the oxidative decomposition of the electrolyte solvent and enhance the stability of the positive and negative electrode interfaces. It can protect the degradation of the positive and negative electrode active materials caused by interface deterioration and significantly improve the cycle and rate performance of lithium-ion batteries at 4.6V. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a diagram of the charge and discharge specific capacity of the button-type lithium-ion battery in Example 1 of the present invention.

[0049] Figure 2 This is a cycle performance diagram of button-type lithium-ion batteries of Comparative Example 1 and Examples 1 to 4 of the present invention at 3 to 4.6V.

[0050] Figure 3 The graph is a cycle performance diagram of the single-layer soft-pack lithium-ion battery of Comparative Example 2, Examples 5 and 6 of the present invention at 3 to 4.6V.

[0051] Figure 4 This is a charge and discharge capacity diagram of the button-type lithium-ion battery in Comparative Example 1 of the present invention.

[0052] Figure 5 The graph is a cycle performance graph of the single-layer soft-pack lithium-ion battery at 3 to 4.6V of Comparative Examples 3 and 4 of the present invention. The graph is a cycle performance graph of the single-layer soft-pack lithium-ion battery at 3 to 4.6V. DETAILED DESCRIPTION

[0053] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0054] Unless otherwise specified, the materials used in the present invention are conventional commercial products, and the methods used are conventional technical means.

[0055] Example 1

[0056] The high voltage additive used in this embodiment is 2-hydroxy-5-methyl-3-nitropyridine (named as P-MNP), and its structural formula is as shown in formula (3):

[0057]

[0058] The preparation method of the high-voltage lithium battery electrolyte comprises: under anhydrous inert atmosphere (argon), the organic solvent is a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7, and the lithium salt is lithium hexafluorophosphate; firstly, ethylene carbonate and dimethyl carbonate are mixed, and then lithium hexafluorophosphate is added to make the concentration of lithium hexafluorophosphate in the solution be 1 mol / L, stirring and shaking at a temperature of 25° C. for 1 hour to fully dissolve it, and then adding 1wt% of 2-hydroxy-5-methyl-3-nitropyridine high-voltage additive to obtain a high-voltage lithium ion battery electrolyte.

[0059] Lithium cobalt oxide (LiCoO 2 ) Preparation of lithium-ion batteries:

[0060] The positive electrode active material LiCoO 2 The binder polyvinylidene fluoride and the conductive agent Super- were mixed in a weight ratio of 8:1:1, and N-methylpyrrolidone was added and stirred evenly to form a positive electrode slurry; the positive electrode slurry was evenly coated on an aluminum foil with a thickness of 13 μm; the aluminum foil was dried at room temperature and then transferred to a 100°C oven for drying for 10 hours, and then rolled and cut to obtain LiCoO 2 Positive electrode;

[0061] The negative electrode active material graphite, the thickener sodium carboxymethyl cellulose, the binder styrene-butadiene rubber, and the conductive agent Super-P are mixed in a weight ratio of 90:3:3:4, deionized water is added, and the mixture is stirred evenly to form a negative electrode slurry; the negative electrode slurry is evenly coated on a copper foil with a thickness of 8 μm; the copper foil is dried at room temperature and then transferred to a 110°C oven for drying for 10 hours, and then rolled and cut into pieces to obtain a graphite negative electrode sheet;

[0062] The positive electrode shell, the pole piece, the separator, the lithium sheet, and the negative electrode shell are stacked in order, the prepared electrolyte is injected, and then the package is sealed at a pressure of 50 MPa, and then the temperature is kept at 25°C for more than 12 hours to obtain LiCoO 2 Button lithium-ion battery.

[0063] Figure 1 is a charge and discharge specific capacity diagram of a button-type lithium-ion battery in this embodiment; Figure 2 This is a cycle performance diagram of a button-type lithium-ion battery at 3 to 4.6V in this embodiment.

[0064] The performance data of button lithium-ion batteries are shown in Table 1.

[0065] Example 2

[0066] Compared with Example 1, the difference is that the high voltage additive used in this embodiment is 2-hydroxy-3-methyl-5-nitropyridine (named as O-MNP), and its structural formula is as shown in Formula (4):

[0067]

[0068] Figure 2 This is a cycle performance diagram of the button-type lithium-ion battery at 3 to 4.6V in this embodiment; the performance data of the button-type lithium-ion battery is shown in Table 1.

[0069] Example 3

[0070] Compared with Example 1, the difference is that the high voltage additive used in this embodiment is 2-hydroxy-3-nitro-5-trifluoromethylpyridine (named as P-tFNP), and its structural formula is as shown in Formula (5):

[0071]

[0072] Figure 2 This is a cycle performance diagram of the button-type lithium-ion battery at 3 to 4.6V in this embodiment; the performance data of the button-type lithium-ion battery is shown in Table 1.

[0073] Example 4

[0074] Compared with Example 1, the difference is that the high voltage additive used in this embodiment is 2-hydroxy-5-nitro-3-trifluoromethylpyridine (named O-tFNP), and its structural formula is as shown in Formula (6):

[0075]

[0076] Figure 2 This is a cycle performance diagram of the button-type lithium-ion battery at 3 to 4.6V in this embodiment; the performance data of the button-type lithium-ion battery is shown in Table 1.

[0077] Example 5

[0078] Compared with Example 1, the difference is that the high-voltage lithium-ion battery electrolyte in Example 1 is made into a single-layer soft-pack lithium-ion battery.

[0079] The preparation method of a single-layer soft-pack lithium-ion battery comprises:

[0080] Prepare positive and negative electrodes according to the method described in Example 1;

[0081] The positive and negative electrodes are cut by a soft pack slicer, and the aluminum tabs are welded to the positive electrode and the nickel tabs are welded to the negative electrode. Celgard M825 diaphragm is used to separate LiCoO 2 The positive electrode was wrapped with a diaphragm and aligned with the negative graphite electrode, then wrapped with aluminum foil and sealed with a heat sealer. Finally, 3 mL of electrolyte was added and allowed to stand for 12 hours before testing.

[0082] Single-layer soft package LiCoO 2 The pole piece size is 44mm*80mm, and the Gr pole piece size is 46mm*82mm.

[0083] Figure 3 This is a cycle performance diagram of a single-layer soft-pack lithium-ion battery at 3 to 4.6 V in this embodiment; the performance data of the single-layer soft-pack battery is shown in Table 1.

[0084] Example 6

[0085] Compared with Example 5, the difference is that the added amount of the high voltage additive is 3 wt %.

[0086] Figure 3 This is a cycle performance diagram of a single-layer soft-pack lithium-ion battery at 3 to 4.6 V in this embodiment; the performance data of the single-layer soft-pack battery is shown in Table 1.

[0087] Example 7

[0088] Compared with Example 1, the difference is that the added amount of the high voltage additive is 0.5 wt %.

[0089] The performance data of lithium-ion batteries are shown in Table 1.

[0090] Example 8

[0091] Compared with Example 1, the difference is that the added amount of the high voltage additive is 10 wt %.

[0092] The performance data of lithium-ion batteries are shown in Table 1.

[0093] Comparative Example 1

[0094] Compared with Example 1, the difference is that no high voltage additive is added to the electrolyte (named as Baseline 1).

[0095] Figure 4 : is the charge and discharge capacity diagram of the button-type lithium-ion battery in this comparative example, Figure 2 : is a cycle performance diagram of the button-type lithium-ion battery in this comparative example; the performance data of the button-type lithium-ion battery is shown in Table 1.

[0096] Comparative Example 2

[0097] Compared with Example 5, the difference is that no high voltage additive (named as Baseline 2) is added to the electrolyte.

[0098] Figure 3 1 is a cycle performance diagram of the single-layer soft-pack lithium-ion battery in this comparative example; the performance data of the single-layer soft-pack battery is shown in Table 1.

[0099] Comparative Example 3

[0100] Compared with Example 1, the difference is that the high voltage additive is 2-hydroxy-5-methylpyridine (named as HMP), and its structure is shown in formula (7).

[0101]

[0102] Figure 5 : is the cycle performance diagram of the single-layer soft-pack lithium-ion battery in this comparative example; the performance data of the single-layer soft-pack lithium-ion battery is shown in Table 1.

[0103] Comparative Example 4

[0104] Compared with Example 1, the difference is that the high voltage additive is 2-hydroxy-5-trifluoromethylpyridine (named as TFMP), and its structure is shown in formula (8).

[0105]

[0106] Figure 5 : is the cycle performance diagram of the single-layer soft-pack lithium-ion battery in this comparative example; the performance data of the single-layer soft-pack lithium-ion battery is shown in Table 1.

[0107] Table 1. Performance data of button type / single-layer soft-pack lithium-ion batteries

[0108]

[0109] It can be seen from the above table that button-type / single-layer soft-pack lithium-ion batteries assembled with the high-voltage-resistant lithium battery electrolyte containing the high-voltage additive of the present invention all show good electrochemical performance.

[0110] Compared with Example 1, the capacity retention rate of the NCM811 lithium-ion batteries of Examples 2 to 4 containing pyridine high-voltage additives at a cut-off voltage of 4.6V is significantly reduced, but all are higher than the capacity retention rate of Comparative Example 1 without additives. This indicates that the type and position distribution of the functional groups in the high-voltage additives will affect the effect of the high-voltage additives.

[0111] Compared with Comparative Example 2, the electrochemical performance of the single-layer soft-pack lithium-ion battery with the high-voltage additive added in Examples 5 and 6 is significantly improved; and as the amount of high-voltage additive added to the high-voltage lithium battery electrolyte increases, the performance of the single-layer soft-pack lithium-ion battery decreases slightly;

[0112] Similarly, compared with Comparative Example 1, the electrochemical performance of the lithium-ion batteries added with the high-voltage additives in Examples 1, 7, and 8 is significantly improved; and as the amount of high-voltage additives added to the high-voltage lithium battery electrolyte increases, the electrochemical performance of the button lithium-ion batteries first increases and then decreases.

[0113] In summary, the high voltage additive of the present invention is a pyridine compound containing a carbonyl group, a nitro group and an R group. Both the carbonyl group and the nitro group are strong electron-withdrawing groups, which can enhance the interaction with lithium ions and solvents. According to the relative position of the oxygen atoms in the carbonyl group and the nitro group on the pyridine six-membered ring, the Li+ Coordination ability, change electrolyte conductivity, viscosity, Li + The carbonyl and nitro groups can complex more free solvents and ions to form a high-voltage stable solvation structure, thereby improving the oxidative stability of the electrolyte and expanding the electrochemical window of the carbonate solvent. 2 Functional groups such as N-pyridine rings can be preferentially oxidized or reduced on the positive and negative electrode sides of the battery to form Li-rich 3 N、LiN x O y The electrode electrolyte interface contains inorganic components such as lithium ion battery and lithium ion battery. This dense and strong electrode electrolyte interface has good electronic insulation, which can effectively inhibit the oxidative decomposition of the electrolyte solvent and enhance the stability of the positive and negative electrode interfaces. It can protect the degradation of the positive and negative electrode active materials caused by interface deterioration and significantly improve the cycle and rate performance of lithium-ion batteries at 4.6V.

[0114] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A high voltage additive for lithium battery electrolyte, characterized in that: The high voltage additive is added to the lithium battery electrolyte in an amount of 0.1 to 15 wt %; the high voltage additive is a pyridine compound, and the structure of the pyridine compound includes a nitro group, a hydroxyl group, and an R1 group; The R1 includes any one of a halogen group, an alkane group, an alkoxy group, a fluoroalkyl group, a halogenated alkyl group, an alkene group, an alkynyl group, a cyano group (-CN), an amino group (-NH2), a halogenated alkene group, a halogenated alkynyl group, an aromatic group, and a heterocyclic aromatic group.

2. The high voltage additive for lithium battery electrolyte according to claim 1, characterized in that: The high voltage additive has a general structural formula as shown in formula (1) or formula (2): Among them, R1 includes any one of a halogen group, an alkane group, an alkoxy group, a fluoroalkyl group, a halogenated alkyl group, an alkene group, an alkynyl group, a cyano group (-CN), an amino group (-NH2), a halogenated alkene group, a halogenated alkynyl group, and an aromatic group.

3. The high voltage additive for lithium battery electrolyte according to claim 1, characterized in that: The alkane group includes any one of -CH3, -C2H5, and -C3H7; the fluoroalkane group is -C n F 2n+1 , including any one of -CF3, -C2F5.

4. The high voltage additive for lithium battery electrolyte according to claim 1, characterized in that: The high voltage additive is 2-hydroxy-5-methyl-3-nitropyridine, and its structural formula is shown in formula (3):

5. An application of a high voltage additive for lithium battery electrolyte, characterized in that: The application process comprises: adding the high voltage additive for lithium battery electrolyte described in claim 1 into the lithium battery electrolyte.

6. A high voltage resistant lithium battery electrolyte, characterized in that: The invention comprises 0.1-15 wt % of the high voltage additive for lithium battery electrolyte as claimed in claim 1.

7. The high voltage resistant lithium battery electrolyte according to claim 6, characterized in that: The high-voltage-resistant lithium battery electrolyte comprises lithium salt, organic solvent, and high-voltage additives for lithium battery electrolyte.

8. The high voltage resistant lithium battery electrolyte according to claim 6, characterized in that: The preparation method of the high-voltage resistant lithium battery electrolyte comprises: adding lithium salt to an organic solvent under anhydrous inert atmosphere, stirring at 20-40° C. for 10-200 min and then standing for 5-24 h, and then adding a high-voltage additive for lithium battery electrolyte and mixing to obtain the high-voltage resistant lithium battery electrolyte.

9. A high voltage resistant lithium ion battery, characterized in that: It includes the high-voltage lithium battery electrolyte described in claim 6.

10. The high voltage resistant lithium ion battery according to claim 9, characterized in that: The positive electrode of the high-voltage-resistant lithium-ion battery is a lithium cobalt oxide electrode, and the negative electrode is a graphite electrode.

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