Cyanoethyl amine compound and application thereof

Abstract

The invention relates to a cyanoethyl amine compound and application thereof in an electrolyte and a lithium ion battery. The cyanoethyl amine compound has a structure as shown in a formula (I). The cyanoethyl amine compound can form a stable electrode protection film only by adding a small amount of the cyanoethyl amine compound into an electrolyte of a lithium ion battery, the electrolyte is inhibited from oxygenolysis, and a positive electrode is protected, so that the cycle life, the rate capability and the specific discharge capacity of the battery are effectively improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, relates to an electrolyte additive, and specifically relates to a cyanoethylamine compound and its applications in an electrolyte and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have rapidly gained high attention in the scientific research and industrial communities due to their own advantages (high output voltage, high capacity, and stable embedded material structure), and are widely used in portable electronic devices, electric vehicles, and energy storage fields. Despite many achievements, in order to meet the requirements for higher energy density and longer cycle life, it is necessary to develop cathode materials that can provide higher working voltage and specific capacity.

[0003] LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) has gradually replaced the traditional lithium cobalt oxide cathode due to its advantages such as stable structure, high specific capacity, and low cost, and has a broader research and application prospect. However, there are also many problems in the application of NCM811, such as poor cycle performance, structural instability, and transition metal dissolution. First, high-nickel materials will have a large change in particle shrinkage volume during deep delithiation, and more cracks will be generated during the process. These cracks will lead to a decline in the battery cycle performance and will also produce more negative reactions with the electrolyte. Second, during the charge and discharge process of the battery, the inevitable acidic substances generated by the hydrolysis of LiPF6 in the electrolyte will also accelerate the dissolution of transition metal ions in NCM811, causing the material structure to collapse, an irreversible phase transformation from a layered structure to a spinel structure, and reducing the cycle life. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an electrolyte additive to improve the structural stability of the NCM811 cathode and enhance the performance of the NCM811 lithium-ion battery.

[0005] The technical solutions to achieve the above purpose are as follows.

[0006] In the first aspect of the present invention, a cyanoethylamine compound having the structure shown in formula (I) is provided,

[0007]

[0008] wherein, Z is selected from the following groups:

[0009]

[0010] R1, R2, and R7 are each independently selected from: C1-C4 alkylene;

[0011] R3 and R8 are each independently selected from: methylene, ethylene, or do not exist;

[0012] R4, R5, and R6 are each independently selected from: C1-C4 alkyl.

[0013] In the second aspect of the present invention, an electrolyte is provided, which contains an additive selected from any one or more of the cyanoethylamine compounds of the present invention.

[0014] In the third aspect of the present invention, a lithium-ion battery is provided, and its electrolyte is the electrolyte of the present invention.

[0015] The present invention has the following beneficial effects:

[0016] The cyanoethylamine compound provided by the present invention, as an additive for the electrolyte of lithium-ion batteries, can preferentially oxidize on the electrode surface to form a stable and uniform protective film prior to the lithium salt electrolyte, reduce the side reactions at the interface between the electrolyte and the positive electrode material, protect the integrity of the positive electrode material structure, reduce the interfacial film impedance, and can also effectively inhibit the hydrolysis of the lithium salt in the electrolyte, avoiding the damage to the NCM811 electrode structure caused by the acidic substances generated due to the hydrolysis of the lithium salt. With the cooperation of the above various effects, the cyanoethylamine compound of the present invention only needs to be added in a small amount to the electrolyte of lithium-ion batteries to form a stable electrode protective film, inhibit the oxidation and decomposition of the electrolyte, and protect the positive electrode, thereby effectively improving the cycle life, rate performance, and discharge specific capacity of the battery. Description of the Drawings

[0017] Figure 1 The 1H NMR spectrum of the compound of Example 1 of the present invention is shown.

[0018] Figure 2 The 13C NMR spectrum of the compound of Example 1 of the present invention is shown.

[0019] Figure 3 The 29Si NMR spectrum of the compound of Example 1 of the present invention is shown.

[0020] Figure 4 The 1H NMR spectrum of the compound of Example 2 of the present invention is shown.

[0021] Figure 5 The 13C NMR spectrum of the compound of Example 2 of the present invention is shown.

[0022] Figure 6 The 19F NMR spectrum of the compound of Example 2 of the present invention is shown.

[0023] Figure 7 The 1H NMR spectrum of the compound of Example 3 of the present invention is shown.

[0024] Figure 8The attached is the carbon-13 NMR spectrum of the compound in Example 3 of the present invention.

[0025] Figure 9 The attached is the proton NMR spectrum of the compound in Example 4 of the present invention.

[0026] Figure 10 The attached is the carbon-13 NMR spectrum of the compound in Example 4 of the present invention.

[0027] Figure 11 The attached shows the hydrolysis experiment comparison of different electrolytes: Among them, Example 5 in the legend represents the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0028] Figure 12 The attached shows the linear voltammetry scan curves of different electrolytes: Among them, Example 5 in the legend represents the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0029] Figure 13 The attached shows the cyclic voltammetry scan curves of different electrolytes: Among them, Example 5 in the legend represents the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0030] Figure 14 The attached shows the cycle performance test of different NCM811 / Li batteries: Among them, Example 5 in the legend represents the battery with the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the battery with the LB301 base electrolyte.

[0031] Figure 15 The attached shows the cycle performance test of different graphite / Li batteries: Among them, Example 5 in the legend represents the battery with the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the battery with the LB301 base electrolyte.

[0032] Figure 16 The attached shows the cycle performance test of different NCM811 / graphite batteries: Among them, Example 5 in the legend represents the battery with the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the battery with the LB301 base electrolyte.

[0033] Figure 17 The attached shows the impedance performance test after cycling of different NCM811 / Li batteries: Among them, Example 5 in the legend represents the battery with the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the battery with the LB301 base electrolyte.

[0034] Figure 18The following shows the rate performance test results of different NCM811 / Li batteries: Among them, the legend of Example 5 represents the battery with the compound of Example 1 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0035] Figure 19 The following shows the linear voltammetry scanning curves of different electrolytes: Among them, the legend of Example 6 represents the compound of Example 2 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0036] Figure 20 The following shows the cyclic voltammetry scanning curves of different electrolytes: Among them, the legend of Example 6 represents the battery with the compound of Example 2 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0037] Figure 21 The following shows the impedance performance test after cycling of different NCM811 / Li batteries: Among them, the legend of Example 6 represents the battery with the compound of Example 2 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0038] Figure 22 The following shows the cycling performance test of different NCM811 / Li batteries: Among them, the legend of Example 6 represents the battery with the compound of Example 2 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0039] Figure 23 The following shows the linear voltammetry scanning curves of different electrolytes: Among them, the legend of Example 7 represents the compound of Example 3 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0040] Figure 24 The following shows the cyclic voltammetry scanning curves of different electrolytes: Among them, the legend of Example 7 represents the compound of Example 3 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte.

[0041] Figure 25 The following shows the impedance performance test after cycling of different NCM811 / Li batteries: Among them, the legend of Example 7 represents the battery with the compound of Example 3 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0042] Figure 26 The following shows the cycling performance test of different NCM811 / Li batteries: Among them, the legend of Example 7 represents the battery with the compound of Example 3 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0043] Figure 27Shown are the cycle performance tests of different NCM811 / Li batteries: Among them, Example 8 in the legend represents the battery with the compound of Example 4 + LB301 base electrolyte; Comparative Example 1 represents the LB301 base electrolyte battery.

[0044] Figure 28 Shown are the comparative cycle performances of NCM811 / Li batteries respectively added with TSOAP (Example 5), CNTF (Example 6), CABEA (Example 7), and CABED (Example 8).

[0045] Figure 29 Shown are the comparative cycle performances of NCM811 / Li batteries added with different mass fractions of TSOAP.

[0046] Figure 30 Shown are the comparative test results of the impedance performance after cycling of NCM811 / Li batteries respectively added with TSOAP (Example 5), CNTF (Example 6), CABEA (Example 7), and CABED (Example 8).

[0047] Figure 31 Shown are the cyclic voltammetry scanning curves of different electrolytes respectively added with TSOAP (Example 5), CNTF (Example 6), and CABEA (Example 7). Detailed implementation manners

[0048] For ease of understanding the present invention, the present invention will be described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosed content of the present invention more thorough and comprehensive.

[0049] The experimental methods without specific conditions noted in the following examples are usually in accordance with conventional conditions, such as the fourth edition of "Molecular Cloning: A Laboratory Manual" edited by Green and Sambrook, which was published in 2013, or in accordance with the conditions recommended by the manufacturer. All kinds of common chemical reagents used in the examples are commercially available products.

[0050] The experimental methods without specific conditions noted in the following examples are usually in accordance with conventional conditions or in accordance with the conditions recommended by the manufacturer. All kinds of common chemical reagents used in the examples are commercially available products.

[0051] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention pertains. The terms used in the description of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0052] In addition, as used in the present invention, the term "or" is the inclusive "or" symbol and is equivalent to the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for other factors not described, unless the context clearly dictates otherwise. Further, throughout the specification, the meanings of "a", "an", and "the" include plural referents. The meaning of "in" includes "in" and "on".

[0053] In some embodiments of the present invention, there is involved a cyanoethylamine compound having the structure shown in formula (I),

[0054]

[0055] wherein, Z is selected from the following groups:

[0056]

[0057] R1, R2, R7 are each independently selected from: C1-C4 alkylene;

[0058] R3, R8 are each independently selected from: methylene, ethylene, or absent;

[0059] R4, R5, R6 are each independently selected from: C1-C4 alkyl.

[0060] In some of these embodiments, R1, R2, R7 are each independently selected from: methylene, ethylene, propylene, butylene.

[0061] In some of these embodiments, R4, R5, R6 are each independently selected from: methyl, ethyl, propyl, butyl.

[0062] In some of these embodiments, the cyanoethylamine compound is selected from the following compounds:

[0063]

[0064]

[0065] In some embodiments of the present invention, there is also involved an electrolyte containing an additive, and the additive is selected from any one or more of the cyanoethylamine compounds described in the present invention.

[0066] For the cyanoethylamine compound of the present invention, only a small amount needs to be added to the electrolyte of the lithium-ion battery to form a stable electrode protection film, inhibit the oxidation and decomposition of the electrolyte, and protect the positive electrode, thereby effectively improving the cycle life, rate performance, and discharge specific capacity of the battery. For example, when the mass percentage of the additive in the electrolyte is greater than 0.2%, a good effect of protecting the electrode and improving the battery performance can be obtained. When the mass percentage reaches 1%, an extremely excellent protection effect can be obtained.

[0067] In some preferred embodiments, the mass percentage of the additive in the electrolyte is 0.2%-3%, preferably 0.4%-2%, more preferably 0.5%-1.5%, and even more preferably 0.8%-1.2%. When the amount of the additive is too high, the impedance of the battery will increase, resulting in a decrease in the cycle retention rate. A relatively excellent effect can be maintained within the range of 0.2%-3%.

[0068] The electrolyte of the present invention further contains a lithium salt electrolyte, and the concentration of the lithium salt electrolyte in the electrolyte is preferably 1 mol / L - 1.2 mol / L.

[0069] The present invention does not particularly limit the specific type of the lithium salt electrolyte, and any common lithium salt electrolyte in lithium-ion batteries can be used in the electrolyte of the present invention. For example, it can be any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide, as well as their corresponding metal sodium salts.

[0070] The electrolyte of the present invention further contains a solvent, and the solvent is preferably any one or more of carbonate solvents. For example, it can be selected from any one or more of EC (ethylene carbonate), DEC (diethyl carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), and PC (propylene carbonate).

[0071] In some embodiments, the solvent is a combination of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate with a volume ratio of 1:0.9 - 1.1:0.9 - 1.1.

[0072] Some embodiments of the present invention also relate to a lithium-ion battery, the electrolyte of which is the electrolyte of the present invention added with a cyanoethylamine compound.

[0073] The present invention does not particularly limit other components and materials of the lithium-ion battery, and common positive / negative electrode materials and various components and materials in lithium-ion batteries can be used in the lithium-ion battery of the present invention.

[0074] The present invention will be further described in detail below in conjunction with specific embodiments.

[0075] Example 1: Synthesis of 3-(bis(2-((trimethylsilyl)oxy)ethyl)amino)propanenitrile (TSOAP)

[0076] Under an argon atmosphere and at room temperature, diethanolamine (10.51 g, 0.1 mol) and acrylonitrile (5.31 g, 0.1 mol) were added to a three-necked flask and stirred for 3 h. Hexamethyldisilazane (19.37 g, 0.12 mol) was added dropwise with stirring, and the reaction was carried out at room temperature for 8 h. Pure 3-(bis(2-((trimethylsilyl)oxy)ethyl)amino)propanenitrile (TSOAP) 30.8 g was obtained by vacuum distillation. The yield was 85%, b.p. 108 °C / 0.18 mmHg.

[0077] The chemical structural formula of TSOAP is as follows:

[0078]

[0079] Nuclear magnetic 1 1H-NMR, 13 13C-NMR, 29 29Si-NMR spectra are shown in Figure 1 、 Figure 2 、 Figure 3 。

[0080] 1 1H-NMR (400 MHz, CDCl3) δ 3.61 (t, J = 6.2 Hz, 4H), 2.95 (t, J = 7.1 Hz, 2H), 2.69 (t, J = 6.2 Hz, 4H), 2.45 (t, J = 7.0 Hz, 2H), 0.10 (s, 18H). 13 13C-NMR (101 MHz, CDCl3) δ 119.14, 61.36, 56.78, 51.51, 16.65, -0.51. 29 29Si-NMR (79 MHz, CDCl3) δ 17.98.

[0081] Example 2: Synthesis of ((2-cyanoethyl)aza-diyl)bis(ethane-2,1-diyl) bis(2,2,2-trifluoroacetate) (CNTF)

[0082] Under an argon atmosphere and at room temperature, diethanolamine (10.51 g, 0.1 mol) and acrylonitrile (5.31 g, 0.1 mol) were added to a three-necked flask and stirred for 3 h. 100 ml of anhydrous ether was added as a solvent, and the mixture was stirred under an ice-water bath. Trifluoroacetic anhydride (52.51 g, 0.25 mol) was slowly added dropwise, and the reaction was carried out at room temperature for 8 h. Pure (2-cyanoethyl)azanediyl)bis(ethane-2,1-diyl) bis(2,2,2-trifluoroacetate) (CNTF) 30.47 g was obtained by vacuum distillation. The yield was 87%, b.p. 143 °C / 0.18 mmHg.

[0083] The chemical structure of CNTF is as follows:

[0084]

[0085] Nuclear magnetic 1 1H-NMR and 13 13C-NMR, 19 19F-NMR spectra are shown in Figure 4 , Figure 5 , Figure 6 .

[0086] 1 1H-NMR (400 MHz, CDCl3) δ 4.42 (t, J = 5.5 Hz, 4H), 3.04 - 2.94 (m, 6H), 2.47 (t, J = 6.8 Hz, 2H). 13 13C-NMR (101 MHz, CDCl3) δ 157.32 (q, J = 42.6 Hz), 118.11, 118.69 - 110.18 (m), 65.63, 52.38, 50.64, 17.11. 19 19F-NMR (376 MHz, CDCl3) δ -75.14.

[0087] Example 3: Synthesis of 3-(bis(2-(allyloxy)ethyl)amino)propanenitrile (CABEA)

[0088] Under an argon atmosphere and at room temperature, diethanolamine (10.51 g, 0.1 mol) and acrylonitrile (5.31 g, 0.1 mol) were added to a three-necked flask and stirred for 3 h. 100 ml of tetrahydrofuran was added as a solvent, sodium hydride (4.80 g, 0.2 mol) was added, and the mixture was stirred under an ice-water bath for 4 h. 3-bromopropene (30.25 g, 0.25 mol) was slowly added dropwise, and the reaction was carried out at room temperature for 8 h. Pure 3-(bis(2-(allyloxy)ethyl)amino)propanenitrile (CABED) 19.6 g was obtained by vacuum distillation. The yield was 82.5%, b.p. 124 °C / 0.18 mmHg.

[0089] The chemical structure of CABEA is as follows:

[0090]

[0091] Nuclear magnetic 1 1H-NMR and 13 13C-NMR spectra are shown in Figure 7 、 Figure 8 。

[0092] 1 1H-NMR(400MHz,CDCl3)δ5.99-5.84(m,2H),5.33-5.15(m,4H),3.99(dt,J=5.6,1.5Hz,4H),3.54(t,J=5.7Hz,4H),3.00(t,J=7.0Hz,2H),2.82(t,J=5.6Hz,4H),2.51(t,J=7.0Hz,2H). 13 13C-NMR(101MHz,CDCl3)δ134.68,119.17,116.92,72.10,69.00,54.12,51.11,16.58.

[0093] Example 4: Synthesis of ((2-cyanoethyl)aza-diyl)bis(ethane-2,1-diyl) diacrylate (CABED)

[0094] Under an argon atmosphere and at room temperature, diethanolamine (10.51 g, 0.1 mol) and acrylonitrile (5.31 g, 0.1 mol) were added to a three-necked flask and stirred for 3 h. 100 ml of tetrahydrofuran was added as a solvent, and triethylamine (30.35 g, 0.3 mol) was added and stirred for 30 min under an ice-water bath. Acryloyl chloride (22.63 g, 0.25 mol) was slowly added dropwise, and the reaction was carried out at room temperature for 8 h. Pure ((2-cyanoethyl)aza-diyl)bis(ethane-2,1-diyl) diacrylate (CABED) 21.04 g was obtained by vacuum distillation. The yield was 79%, b.p. 152 °C / 0.18 mmHg. The chemical structure of CABED is as follows:

[0095]

[0096] Nuclear magnetic 1 1H-NMR and 13 13C-NMR spectra are shown in Figure 9 、 Figure 10 。

[0097] 1H-NMR (400 MHz, CDCl3) δ 6.42 (d, J = 17.4 Hz, 2H), 6.20 - 6.05 (m, 2H), 5.86 (d, J = 10.4 Hz, 2H), 4.24 (t, J = 5.6 Hz, 4H), 2.94 (dt, J = 21.4, 6.4 Hz, 6H), 2.48 (t, J = 6.9 Hz, 2H). 13C-NMR (101 MHz, CDCl3) δ 165.96, 131.08, 128.18, 118.57, 62.41, 52.60, 50.70, 17.05.

[0098] Example 5: Preparation of Electrolyte, Electrode Sheet and Button Cell

[0099] 1. Preparation of Electrolyte

[0100] The basic electrolyte is LB301 (1 mol / L LiPF6 in EC / EMC / DMC = 1:1:1), purchased from Shanghai Xiaoyuan Energy Technology Co., Ltd. The cyanoethylamine compound TSOAP prepared in Example 1 was added as an additive to the basic electrolyte at a mass fraction of 1%, stirred evenly and then left standing for 2 h for standby.

[0101] 2. Preparation of Electrode Sheet

[0102] The positive active material (positive electrode material): conductive agent: binder were mixed with a solvent in a mass ratio of 85:9:6 to obtain a positive electrode slurry with a solid content of 25%; the negative active material (negative electrode material): conductive agent: binder were mixed with a solvent in a mass ratio of 90:5:5 to obtain a negative electrode slurry with a solid content of 20%. The positive electrode slurry was coated on an aluminum foil current collector, and the negative electrode slurry was coated on a copper foil current collector. The coated electrode sheets were dried, cut, weighed, and vacuum dried for standby. Among them, the coating thickness of the positive electrode slurry was 130 nm, punched into electrode sheets with a diameter of 14 mm, and the active material content was 4 mg; the coating thickness of the negative electrode slurry was 100 nm, punched into electrode sheets with a diameter of 14 mm, and the active material content was 3 mg.

[0103] The positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 、LiCoO2; the negative electrode material is lithium metal, graphite, or silicon-carbon negative electrode.

[0104] The conductive agent is acetylene black; the binder can be polyvinylidene fluoride (PVDF) or polyvinylidene fluoride / hexafluoropropylene copolymer (PVDF was selected in the performance test of the present invention); the solvent can be N-methylpyrrolidone (NMP), acetone (NMP was selected in the performance test of the present invention).

[0105] The separator is selected from separators with excellent electrolyte wettability, and is a separator made of polyethylene, polypropylene, or a mixture of the two (Celard separator made of polypropylene was selected in the performance tests of the present invention).

[0106] 3. Preparation of Coin Cells

[0107] The CR2025 coin cells were assembled in a glove box under a high-purity argon atmosphere. The cells were assembled in the order of the negative electrode case, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, gasket, and spring piece positive electrode case. They were placed in a sealed plastic bag, and the cells were encapsulated using a manual coin cell sealer. The prepared cells were allowed to stand for 14 h before subsequent tests were carried out.

[0108] Example 6: Preparation of Electrolyte, Electrode Sheets, and Coin Cells

[0109] The additives in the electrolyte were replaced with the cyanoethylamine compound CNTF prepared in Example 2 in equal amounts, and the other steps were the same as those in Example 5.

[0110] Example 7: Preparation of Electrolyte, Electrode Sheets, and Coin Cells

[0111] The additives in the electrolyte were replaced with the cyanoethylamine compound CABEA prepared in Example 3 in equal amounts, and the other steps were the same as those in Example 5.

[0112] Example 8

[0113] The additives in the electrolyte were replaced with the cyanoethylamine compound CABED prepared in Example 4 in equal amounts, and the other steps were the same as those in Example 5.

[0114] Performance Tests

[0115] (1) 1000 ppm of deionized water was added to the basic electrolyte LB301 (legend: Comparative Example 1) and the electrolyte containing 1% TSOAP (legend: Example 5) respectively. After standing for 16 h, NMR tests were carried out. The results are as Figure 11 shown: obvious hydrolysis-generated PO2F - and HF by-product peaks appeared in the basic electrolyte, while no by-product peaks appeared in the electrolyte containing 1% TSOAP. This shows that the cyanoethylamine compounds of the present invention can effectively inhibit the hydrolysis of lithium hexafluorophosphate.

[0116] (2) Figure 12 、 13 Figures 19, 20, 23, and 24 are comparative diagrams of linear sweep voltammograms and cyclic voltammograms of the basic electrolyte LB301 (legend: Comparative Example 1), the electrolyte containing 1% TSOAP (legend: Example 5), the electrolyte containing 1% CNTF (legend: Example 6), and the electrolyte containing 1% CABEA (legend: Example 7); Figure 31It is a comparison chart of the results of each embodiment. As shown in the figure: The electrolyte containing the cyanoethylamine compound additive shows a current change prior to the base electrolyte, indicating that the cyanoethylamine compound is preferentially oxidized and decomposed over the electrolyte, and a protective positive electrode film is formed on the electrode surface.

[0117] (3) Using the LB301 base electrolyte as a comparison, a coin cell (legend: Comparative Example 1) was prepared with reference to Example 5. The compound TSOAP prepared in Example 1 of the present invention was used as an additive, and a coin cell (legend: Example 5) was prepared with reference to Example 5. Their electrochemical performances were compared, and the relevant results are as follows:

[0118] Figure 14 、 Figure 15 、 Figure 16 These are the results of the half-cell and full-cell cycle tests of the electrolytes of Example 5 and Comparative Example 1 of the present invention.

[0119] Figure 14 This is the test of the NCM811 / Li battery charged and discharged in a cycle of 200 circles at a constant current of 1C under the conditions of 3 - 4.5V. The results show that the retention rate of the battery in Example 5 increased from 67.42% to 83.34%. Using TSOAP as an additive can significantly improve the cycle performance of the NCM811 battery.

[0120] Figure 15 This is the test of the graphite / Li battery charged and discharged in a cycle of 200 circles at a constant current of 1C under the conditions of 0.01 - 3V. The results show that their capacity retention rates and charge specific capacities are basically equivalent, but using TSOAP as an additive can reduce the polarization degree of the graphite negative electrode.

[0121] Figure 16 This is the test of the NCM811 / graphite battery charged and discharged in a cycle of 200 circles at a constant current of 1C under the conditions of 2.8 - 4.5V. The results show that the retention rate of the battery in Example 5 increased from 57.37% to 80.39%. Using TSOAP as an additive can significantly improve the cycle performance of the NCM811 battery.

[0122] (4) Using the LB301 base electrolyte as a comparison, a coin cell (legend: Comparative Example 1) was prepared with reference to Example 5. The compound CNTF prepared in Example 2 of the present invention was used as an additive, and a coin cell (legend: Example 6) was prepared with reference to Example 5. Their electrochemical performances were compared.

[0123] Figure 22 This is the test of the NCM811 / Li battery charged and discharged in a cycle of 200 circles at a constant current of 1C under the conditions of 3 - 4.5V. The results show that the retention rate of the battery in Example 6 increased from 67.42% to 81.48%. Using CNTF as an additive can significantly improve the cycle performance of the NCM811 battery.

[0124] (5) Using LB301 basic electrolyte as a comparison, a coin cell (legend: Comparative Example 1) was prepared with reference to Example 5. The compound CABEA prepared in Example 3 of the present invention was used as an additive, and a coin cell (legend: Example 7) was prepared with reference to Example 5. Their electrochemical performances were compared.

[0125] Figure 26 The NCM811 / Li battery was tested by charging and discharging at a constant current of 1C under the condition of 3 - 4.5V for 200 cycles. The results showed that the retention rate of the battery in Example 7 increased from 67.42% to 82.72%. Example 7 can significantly improve the cycle performance of the NCM811 battery.

[0126] (6) Using LB301 basic electrolyte as a comparison, a coin cell (legend: Comparative Example 1) was prepared with reference to Example 5. The compound CABED prepared in Example 4 of the present invention was used as an additive, and a coin cell (legend: Example 8) was prepared with reference to Example 5. Their electrochemical performances were compared.

[0127] Figure 27 The NCM811 / Li battery was tested by charging and discharging at a constant current of 1C under the condition of 3 - 4.5V for 200 cycles. The results showed that the retention rate of the battery in Example 8 increased from 67.42% to 80.73%. Example 8 can significantly improve the cycle performance of the NCM811 battery.

[0128] Figure 28 The NCM811 / Li battery was tested by charging and discharging at a constant current of 1C under the condition of 3 - 4.5V for 200 cycles. For the comparison of the cycle performances of the batteries added with TSOAP (Example 5), CNTF (Example 6), CABEA (Example 7), and CABED (Example 8), the capacity retention rates from low to high were TSOAP > CABEA > CNTF > CABED.

[0129] (7) Using LB301 basic electrolyte as a comparison, a coin cell (legend: Comparative Example 1) was prepared with reference to Example 5. The compound TSOAP prepared in Example 1 of the present invention was used as an additive with different mass fractions (0.5%, 1%, 2% respectively), and coin cells (legends: 0.5% TSOAP, 1% TSOAP, 2% TSOAP respectively) were prepared with reference to Example 5. Their electrochemical performances were compared.

[0130] Figure 29 The NCM811 / Li battery was tested by charging and discharging at a constant current of 1C under the condition of 3 - 4.5V for 200 cycles. The results showed that when the addition amount of TSOAP was 1%, the capacity retention rate was the highest and the cycle performance was the best.

[0131] (8) Figure 17 、 Figure 21 、 Figure 25 are the impedance test results of the NCM811 / Li batteries of Example 5, Example 6, Example 7 and Comparative Example 1 after 200 charge-discharge cycles at a constant current of 1C under the condition of 3 - 4.5V, Figure 30 which is the result comparison of each example. The results show that the impedance of the batteries containing cyanoethylamine additive is less than that of the basic battery after cycling, indicating that the cyanoethylamine additive can effectively reduce the impedance generated during battery cycling. Among them, Example 5 with TSOAP added has the best effect.

[0132] (9) Figure 18 are the rate test results of the NCM811 / Li batteries of Example 5 and Comparative Example 1 after activation at a constant current of 0.1C and then charged and discharged at constant currents of 0.2, 0.5, 1, 2, 5, 10, 0.5C under the condition of 3 - 4.5V. The results show that the batteries containing cyanoethylamine additive have higher discharge specific capacity at larger current densities, indicating that the cyanoethylamine additive can effectively improve the rate performance of the battery and has better performance under the condition of charge and discharge at larger currents.

[0133] Based on the above test results, it shows that using the cyanoethylamine compound of the present invention as an electrolyte additive can preferentially oxidize on the electrode surface to form a stable and uniform CEI film, and can effectively inhibit the hydrolysis of lithium hexafluorophosphate, reduce the generation of acidic substances, inhibit the occurrence of side reactions of the electrolyte, reduce the interfacial film impedance, effectively improve the rate performance of the battery, and improve the discharge specific capacity and cycle life of the battery.

[0134] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A cyanoethylamine compound having a structure represented by formula (I), in, Z is selected from the following groups: R1, R2, and R7 are each independently selected from: C1-C4 alkylene; R3 and R8 are each independently selected from: methylene, ethylene, or absent; R4, R5, and R6 are each independently selected from: C1-C4 alkyl.

2. The cyanoethylamine compound according to claim 1, characterized in that Selected from the following compounds:

3. An electrolyte, characterized in that: It contains additives, and the additives are selected from any one or more of the cyanoethylamine compounds described in claim 1 or 2.

4. The electrolyte according to claim 3, characterized in that The mass percentage of the additive in the electrolyte is 0.2%-3%, preferably 0.4%-2%, more preferably 0.5%-1.5%, more preferably 0.8%-1.2%.

5. The electrolyte according to claim 3 or 4, characterized in that It also contains a lithium salt electrolyte, and the concentration of the lithium salt electrolyte in the electrolyte is preferably 1 mol / L-1.2 mol / L.

6. The electrolyte according to claim 5, characterized in that The lithium salt electrolyte is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonylimide) and lithium bis(fluorosulfonylimide) and their corresponding metal sodium salts.

7. The electrolyte according to claim 3 or 4, characterized in that It also contains a solvent, and the solvent is preferably any one or more selected from carbonate solvents.

8. The electrolyte according to claim 7, characterized in that The solvent is selected from any one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and propylene carbonate, preferably a combination of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 1:0.9-1.1:0.9-1.

1.

9. A lithium ion battery, characterized in that: The electrolyte is the electrolyte described in any one of claims 3 to 8.

10. The lithium ion battery according to claim 9, characterized in that: Its positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O2.

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