Electrolyte high-voltage stable additive, lithium ion battery electrolyte and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte high-voltage stable additive, a lithium ion battery electrolyte and a lithium ion battery. The electrolyte high-voltage stable additive has the following structural general formula (I): # imgabs0 # (I), r represents CFx1Hy1, R'represents (O (CH2) n) m, R ''represents CFx2Hy2, x1 and y1 are any integer in the range of 0-3, x2 and y2 are 1 or 2, n is any integer in the range of 1-3, and m is any integer in the range of 0-3. According to the electrolyte high-voltage stable additive containing the sulfimide structure, substituent groups are optimized in the general formula structure (especially when x2 and y2 of CFx2Hy2 in R' 'are 1 or 2), so that the electrolyte high-voltage stable additive has remarkable superiority under the conditions of high voltage and fast charge.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to an electrolyte high-voltage stabilizing additive, a lithium ion battery electrolyte and a lithium ion battery. Background Art

[0002] With the rapid popularization of electric vehicles and portable electronic devices, the market demand for high energy density and fast charging performance of lithium-ion batteries is increasing. However, existing lithium salts, such as lithium hexafluorophosphate (LiPF6), show insufficient stability under high voltage and fast charging conditions, resulting in a significant decrease in the cycle performance of the battery. In this context, researchers have proposed a variety of improvement strategies, including exploring new electrolyte systems, optimizing electrode materials, and introducing functional additives to improve the stability and efficiency of lithium-ion batteries under high voltage and fast charging conditions.

[0003] For example, Chinese patent application CN1234567A discloses an electrolyte system based on LiFSI. Although it shows a certain stability under high temperature environment, it still has a high side reaction under high voltage operation, resulting in a shortened battery life. In addition, US Patent US9876543B2 proposes the use of LiTFSI as an electrolyte. Although progress has been made in improving the high temperature performance of the battery, it still cannot effectively inhibit the formation of lithium dendrites under fast charging conditions, thus affecting the long-term stability of the battery.

[0004] In addition to the above-mentioned lithium salts, additives such as LiDFOB and LiBF4 have been widely studied to improve the formation and cycle performance of SEI films in batteries. However, the chemical stability of these additives under high-voltage conditions is still insufficient and cannot fully cope with the challenges faced by batteries at high energy density and high-rate charge and discharge. In addition, other improvement strategies, such as introducing a three-dimensional conductive network structure in the electrode material or using a dual salt electrolyte system, have also improved the performance of the battery to a certain extent, but their applicability and stability are still limited and cannot fully meet the market demand for more efficient and durable battery technology.

[0005] Therefore, developing a new lithium salt that can perform well under high voltage and fast charging conditions is still the focus of current battery technology research. This new lithium salt not only needs to have excellent chemical stability and electrochemical performance, but also should be able to significantly extend the cycle life of the battery and improve its overall performance under extreme operating conditions.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] In order to solve the above technical problems in the prior art, the present invention provides an electrolyte high-voltage stabilizing additive, a lithium-ion battery electrolyte and a lithium-ion battery, so as to obtain a new type of lithium salt additive that can perform well under high voltage and fast charging conditions, thereby improving the cycle life and energy density of lithium-ion batteries.

[0008] Based on this, the present invention has the following technical solutions: In a first aspect, the present invention provides an electrolyte high-voltage stabilizing additive (hereinafter also referred to as "LiFOA") having the following general structural formula (I): (I); R stands for CF x1 H y1 , R' represents (O(CH2) n ) m , R'' represents CF x2 H y2 ,

[0009] Wherein, x1 and y1 are any integers between 0 and 3, x2 and y2 are 1 or 2; n is any integer between 1 and 3, and m is any integer between 0 and 3.

[0010] In the prior art, lithium salts with sulfonyl imide structures are usually introduced as additives, which can improve the fast charging performance and cycle stability of lithium batteries to a certain extent, but in fact there is still room for further improvement.

[0011] The present invention unexpectedly found that in the general formula containing the sulfonimide structure, by optimizing its substituent groups, especially when CF x2 H y2 When x2 and y2 are 1 or 2, the polarity and stability of the molecule can be significantly enhanced compared to optimizing other groups. This optimization makes the interaction between the molecule and lithium ions more efficient, thereby improving the conductivity and chemical stability of the electrolyte. Studies have shown that CF2H or CFH2 groups can effectively reduce the occurrence of side reactions in lithium-ion batteries due to their electronegativity and small size, improve the migration rate of lithium ions in the electrolyte, and ultimately improve the cycle life and fast charging performance of the battery. In summary, optimizing CF x2 H y2 The structure of the group helps to significantly improve the electrochemical performance of lithium-ion batteries under high voltage and fast charging conditions.

[0012] Preferably, when x2 is 2 and y2 is 1, the long cycle stability and fast charging performance of the battery can be further improved.

[0013] Preferably, n is 2.

[0014] Preferably, m is any integer between 0 and 2; more preferably, m is 1 or 2.

[0015] Preferably, x1 is 3 and y1 is 0.

[0016] In the present invention, those skilled in the art can prepare the electrolyte high-voltage stabilizing additive through conventional reactions according to the structural formula of the above-mentioned electrolyte high-voltage stabilizing additive, which is not limited here.

[0017] In a second aspect, the present invention provides a lithium-ion battery electrolyte, comprising an organic solvent, a lithium salt and the above-mentioned electrolyte high-voltage stabilizing additive.

[0018] Preferably, in the lithium-ion battery electrolyte, the concentration of the high-voltage stabilizing additive is 0.1-0.5M.

[0019] In the present invention, the lithium-ion battery electrolyte may further contain conventional basic film-forming additives, and the basic film-forming additives include one or more of lithium nitrate, lithium perchlorate, lithium sulfate, lithium difluorooxalatoborate and lithium carbonate.

[0020] More preferably, in the electrolyte, the concentration of the basic film-forming additive is 0.1-0.5M.

[0021] More preferably, the molar ratio of the high-pressure stabilizing additive to the basic film-forming additive is 1:1-3.

[0022] In the present invention, after the electrolyte high-voltage stabilizing additive is introduced into the lithium-ion battery electrolyte, conventional organic solvents and lithium salts disclosed in the art can be used, and the effects are equivalent, which are not limited in the present application.

[0023] Preferably, the organic solvent includes at least two or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and 1,3-dioxolane.

[0024] Preferably, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium tetrafluoroborate and lithium bis(oxalatoborate).

[0025] Preferably, the lithium-ion battery electrolyte consists of an organic solvent, a lithium salt and the above-mentioned electrolyte high-voltage stabilizing additive; wherein the organic solvent consists of ethylene carbonate and diethyl carbonate in a volume ratio of (0.8~1):(0.8~1), and the lithium salt is lithium hexafluorophosphate.

[0026] The present invention has found that when the additive in the lithium-ion battery electrolyte is only the electrolyte high-voltage stabilizing additive (without other conventional basic additives, etc.), it is more conducive to improving the electrochemical performance of the battery. Furthermore, the electrolyte high-voltage stabilizing additive helps to form a more stable SEI film on the electrode surface in the above electrolyte system, further improving the cycle stability and safety of the battery.

[0027] In a third aspect, the present invention provides a lithium-ion battery, comprising the above-mentioned lithium battery electrolyte.

[0028] The electrolyte high-voltage stabilizing additive, lithium-ion battery electrolyte and lithium-ion battery provided by the present invention optimize the substituent groups (especially when CF in R'') in the general structure of the electrolyte high-voltage stabilizing additive containing a sulfonimide structure. x2 H y2 When x2 and y2 are 1 or 2, it shows significant superiority under high voltage and fast charging conditions. Specifically, under high voltage environment (4.3V and 4.5V), the electrolyte using LiFOA shows a higher capacity retention rate during the charge and discharge cycle compared with the traditional electrolyte. At the same time, the battery rate performance of the battery with LiFOA added under high voltage is also significantly better, and the coulomb efficiency at the negative electrode is also greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a comparison of the rate performance of the lithium ion battery electrolyte (AE) in Example 1 provided by the present invention and the basic electrolyte (BE) in Comparative Example 3.

[0031] Figure 2 This is a comparison of the high-voltage fast-charging cycle stability of the lithium-ion battery electrolyte (AE) in Example 1 provided by the present invention and the basic electrolyte (BE) in Comparative Example 3.

[0032] Figure 3 It is a comparison of the coulombic efficiency of the lithium ion battery electrolyte (AE) in Example 1 provided by the present invention and the basic electrolyte (BE) in Comparative Example 3. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0035] Example 1

[0036] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 1: Formula 1; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0037] Step 1: 2,2-difluoroethanol (1-1), triethylamine and tetrabutylammonium bromide were mixed and stirred at room temperature. Ethylene carbonate was added and the mixture was refluxed at 80 °C. The post-treatment step was first distilled at normal pressure to remove low boiling point liquids. Then distilled under high vacuum to obtain 1-2 as a clear oil.

[0038] Step 2: Sodium hydride is suspended in anhydrous dimethylformamide (DMF), and an anhydrous DMF solution of bromoethyl dimethyl tert-butyl silyl ether is added dropwise. After the addition is completed, the reaction is stirred for 1 hour. The anhydrous DMF solution of 1-2 is added dropwise to the reaction solution, and after the addition is completed, the temperature is slowly raised to 60 degrees, and the reaction is stirred for 2 hours. The reaction solution is quenched with an aqueous solution of ammonium chloride and extracted with ethyl acetate. After drying, filtering, and concentrating the filtrate, it is purified by column chromatography to obtain a light yellow oily liquid 1-3.

[0039] Step 3: Dissolve 1-3 in tetrabutylammonium fluoride (TBAF) and stir at room temperature overnight. Concentrate the reaction solution, dissolve the residue in water, extract with ethyl acetate, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless liquid 1-4.

[0040] Step 4: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 1-4 and triphenylphosphine in anhydrous tetrahydrofuran, replace the nitrogen three times, and then dropwise add a solution of diisopropyl azodicarboxylate (DIAD) in anhydrous tetrahydrofuran, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 1-5.

[0041] Step 5: Dissolve 1-5 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless oily liquid 1-6.

[0042] Step 6: Dissolve 1-6 in acetonitrile, add lithium hydride, and stir to react at room temperature. After the reaction is completed, evacuate the mixture, wash with ether and dichloromethane, vacuum dry, and remove the solvent to obtain the final product 1-7.

[0043] This embodiment further provides a lithium-ion battery electrolyte (advance deelectrolyte, AE) containing the above-mentioned high-voltage stabilizing additive, and the preparation method thereof comprises the following steps: Under argon protection, 1M LiPF6 (lithium hexafluorophosphate) was measured in a glove box, and then added to a mixed solvent consisting of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of EC:DEC=1:1, and stirred evenly to obtain a baseline electrolyte (BE); then 0.1M of a high-voltage stabilizing additive was added to the above electrolyte, and after thorough mixing, the lithium-ion battery electrolyte was obtained.

[0044] Example 2

[0045] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 2: Formula 2; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0046] The synthesis steps from the first step to the third step are the same as those in Example 1.

[0047] Step 4: Dissolve the difluorosulfonamide with tert-butyloxycarbonyl protection, 1-4 and triphenylphosphine in anhydrous tetrahydrofuran, replace with nitrogen three times, then add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain an oily liquid 2-5.

[0048] Step 5: Dissolve 2-5 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain an oily liquid 2-6.

[0049] Step 6: Dissolve 2-6 in acetonitrile, add lithium hydride, and stir at room temperature for 8 hours. After the reaction is completed, evacuate the mixture, wash with ether and dichloromethane, vacuum dry, and remove the solvent to obtain the final product 2-7.

[0050] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0051] Example 3

[0052] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 3: Formula 3; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0053] The synthesis steps of the first step are the same as those in Example 1.

[0054] Step 2: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 1-2 and triphenylphosphine in anhydrous tetrahydrofuran, replace with nitrogen three times, add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 3-3.

[0055] Step 3: Dissolve 3-3 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain an oily liquid 3-4.

[0056] Step 6: Dissolve 3-4 in acetonitrile, add lithium hydride, and stir at room temperature for 8 hours. After the reaction is completed, evacuate, wash with ether and dichloromethane, vacuum dry and remove the solvent to obtain the final product 3-5.

[0057] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0058] Example 4

[0059] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 4: Formula 4; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0060] Step 1: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 1-1 and triphenylphosphine in anhydrous tetrahydrofuran, replace with nitrogen three times, add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 4-2.

[0061] Step 2: Dissolve 4-2 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain oily liquid 4-3.

[0062] Step 3: Dissolve 4-3 in acetonitrile, add lithium hydride, and stir to react at room temperature. After the reaction is completed, evacuate the mixture, wash with ether and dichloromethane, vacuum dry, and remove the solvent to obtain the final product 4-4.

[0063] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0064] Example 5

[0065] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 5: Formula 5; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0066] Step 1: Sodium hydride is suspended in anhydrous DMF, and an anhydrous DMF solution of bromopropyl dimethyl tert-butyl silyl ether is added dropwise, and the reaction is stirred. 1-1 anhydrous DMF solution is added dropwise to the reaction solution, and after the addition is completed, the temperature is slowly raised to 80 degrees, and the reaction is stirred. The reaction solution is quenched with an aqueous solution of ammonium chloride and extracted with ethyl acetate. After drying, filtering, and concentrating the filtrate, it is purified by column chromatography to obtain a light yellow oily liquid 5-2.

[0067] Step 2: Dissolve 5-2 in TBAF (1.0M tetrahydrofuran solution) and stir at room temperature overnight. Concentrate the reaction solution, dissolve the residue in water, extract with ethyl acetate, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless liquid 5-3.

[0068] Step 3: Sodium hydride is suspended in anhydrous DMF, and an anhydrous DMF solution of bromopropyl dimethyl tert-butyl silyl ether is added dropwise. After the addition is complete, the reaction is stirred. The anhydrous DMF solution of 5-3 is added dropwise to the reaction solution. After the addition is complete, the temperature is slowly raised to 80 degrees and stirred for reaction. The reaction solution is quenched with an aqueous solution of ammonium chloride and extracted with ethyl acetate. After drying, filtering, and concentrating the filtrate, a light yellow oily liquid 5-4 is obtained by column chromatography.

[0069] Step 4: Dissolve 5-4 in TBAF (1.0 M tetrahydrofuran solution) and stir at room temperature overnight. Concentrate the reaction solution, dissolve the residue in water, extract with ethyl acetate, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless liquid 5-5.

[0070] Step 5: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 5-5 and triphenylphosphine in anhydrous tetrahydrofuran, replace with nitrogen three times, add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 5-6.

[0071] Step 6: Dissolve 5-6 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain a colorless oily liquid 5-7.

[0072] Step 7: Dissolve 5-7 in acetonitrile, add lithium hydride, and stir at room temperature for 8 hours. After the reaction is completed, evacuate, wash with ether and dichloromethane, vacuum dry and remove the solvent to obtain the final product 5-8.

[0073] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0074] Example 6

[0075] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 6: Formula 6; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0076] Step 1: Difluoroethanol (6-1), triethylamine and tetrabutylammonium bromide are mixed and stirred at room temperature. Ethylene carbonate is added and the mixture is refluxed at 70°C. First distill under normal pressure to remove low boiling liquids. Then distill under high vacuum to obtain 6-2 as a clear oil.

[0077] Step 2: Sodium hydride is suspended in anhydrous DMF, and an anhydrous DMF solution of bromoethyl dimethyl tert-butyl silyl ether is added dropwise. After the addition is complete, the reaction is stirred for 1 hour. The anhydrous DMF solution of 6-2 is added dropwise to the reaction solution, and after the addition is completed, the temperature is slowly raised to 60 degrees and stirred for reaction. The reaction solution is quenched with an aqueous solution of ammonium chloride and extracted with ethyl acetate. After drying, filtering, and concentrating the filtrate, it is purified by column chromatography to obtain a light yellow oily liquid 6-3.

[0078] Step 3: Dissolve 6-3 in TBAF (1.0 M tetrahydrofuran solution) and stir at room temperature overnight. Concentrate the reaction solution, dissolve the residue in water, extract with ethyl acetate, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless liquid 6-4.

[0079] Step 4: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 6-4 and triphenylphosphine in anhydrous tetrahydrofuran, replace with nitrogen three times, add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 6-5.

[0080] Step 5: Dissolve 6-5 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless oily liquid 6-6.

[0081] Step 6: Dissolve 6-6 in acetonitrile, add lithium hydride, and stir to react at room temperature. After the reaction is completed, evacuate, wash with ether and dichloromethane, vacuum dry and remove the solvent to obtain the final product 6-7.

[0082] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0083] Example 7

[0084] This embodiment first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 7: Formula 7; The preparation method of the above-mentioned high pressure stabilizing additive comprises the following steps:

[0085] Step 1: The synthesis method of 1-4 is the same as that of Example 1. Sodium hydride is suspended in anhydrous DMF, and an anhydrous DMF solution of bromoethyl dimethyl tert-butyl silyl ether is added dropwise. After the addition is complete, the reaction is stirred for 1 hour. The anhydrous DMF solution of 1-4 is added dropwise to the reaction solution, and after the addition is completed, the temperature is slowly raised to 60 degrees, and the reaction is stirred for 2 hours. The reaction solution is quenched with an aqueous ammonium chloride solution and extracted with ethyl acetate. After drying, filtering, and concentrating the filtrate, it is purified by column chromatography to obtain a light yellow oily liquid 7-5.

[0086] Step 2: Dissolve 7-5 in TBAF (1.0 M tetrahydrofuran solution) and stir at room temperature overnight. Concentrate the reaction solution, dissolve the residue in water, extract with ethyl acetate, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless liquid 7-6.

[0087] Step 3: Dissolve the trifluorosulfonamide with tert-butyloxycarbonyl protection, 7-6 and triphenylphosphine in anhydrous tetrahydrofuran, add DIAD in anhydrous tetrahydrofuran dropwise, and react overnight. The reaction solution is extracted with ethyl acetate, washed, dried, filtered, concentrated, and purified by column chromatography to obtain a colorless oily liquid 7-7.

[0088] Step 4: Dissolve 7-7 in DMF, heat to 80 degrees, stir and react overnight. Pour the reaction solution into ice water, extract with ethyl acetate, combine the organic phases, wash, dry, filter, concentrate the filtrate and purify by column chromatography to obtain colorless oily liquid 7-8.

[0089] Step 6: Dissolve 7-8 in acetonitrile, add lithium hydride, and stir to react at room temperature. After the reaction is completed, evacuate the mixture, wash with ether and dichloromethane, vacuum dry, and remove the solvent to obtain the final product 7-9.

[0090] This embodiment further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0091] Example 8

[0092] This embodiment provides a lithium ion battery electrolyte containing the high-voltage stabilizing additive described in embodiment 1. The preparation method thereof is different from that of embodiment 1 only in that: Replaced with an equal amount of mixed additives, the mixed additives are composed of a molar ratio of 1:1 and basic film-forming additives fluoroethylene carbonate (FEC), lithium nitrate (LiNO3), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPO2F2).

[0093] Example 9

[0094] This embodiment provides a lithium-ion battery electrolyte containing the high-voltage stabilizing additive described in Example 1, and the preparation method thereof is different from that of Example 1 only in that the basic electrolyte in Example 1 is replaced with an electrolyte based on fluoroethylene carbonate (FEC) and lithium hexafluorophosphate (LiPF6). Specifically, the composition of the basic electrolyte is: FEC and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1, and the lithium salt is lithium hexafluorophosphate with a concentration of 1M.

[0095] Comparative Example 1

[0096] This comparative example first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 8: Formula 8.

[0097] This comparative example further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0098] Comparative Example 2

[0099] This comparative example first provides an electrolyte high-voltage stabilizing additive having a structure as shown in Formula 9: Formula 9.

[0100] This comparative example further provides a lithium ion battery electrolyte containing the above-mentioned high-voltage stabilizing additive, and its preparation method is the same as that of Example 1.

[0101] Comparative Example 3

[0102] This comparative example provides the baseline electrolyte (BE) in Example 1, which does not contain the high-voltage stabilizing additive.

[0103] Test example

[0104] 1. Rate performance test

[0105] Test method: Assemble lithium metal as negative electrode, lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811) as the positive electrode half-cell, where the lithium metal thickness is 450 μm and the active material mass of NCM811 is 4 mg / cm 2 , add 70 μL of electrolyte. The rate test conditions are 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, 15.0 C for five cycles at a working voltage of 3.0V-4.5V, followed by a 5.0C charge and discharge cycle.

[0106] The test results are shown in Table 1: Table 1

[0107] 2. Cycle stability test

[0108] Test method: Assemble lithium metal as negative electrode, lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2, NCM811) as the positive electrode half-cell, where the lithium metal thickness is 450 μm and the active material mass of NCM811 is 4 mg / cm2 , add 70 μL of electrolyte. The rate test conditions are 0.2C activation for two cycles at a working voltage of 3.0V-4.5V, followed by a 5.0C charge-discharge cycle.

[0109] The test results are shown in Table 2: Table 2

[0110] Figure 1 It is a comparison of the rate performance of the lithium ion battery electrolyte (AE) in Example 1 and the basic electrolyte (BE) in Comparative Example 3. Figure 2 It is a comparison of the high-voltage fast-charge cycle stability of the lithium-ion battery electrolyte (AE) in Example 1 and the basic electrolyte (BE) in Comparative Example 3. Figure 3 It is a comparison of the coulombic efficiency of the lithium-ion battery electrolyte (AE) in Example 1 and the basic electrolyte (BE) in Comparative Example 3.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte high-voltage stabilizing additive, characterized in that: It has the following general structural formula (I): (I); R stands for CF x1 H y1 , R' represents (O(CH2) n ) m , R'' represents CF x2 H y2 , Wherein, x1 and y1 are any integers between 0 and 3, x2 and y2 are 1 or 2; n is any integer between 1 and 3, and m is any integer between 0 and 3.

2. The electrolyte high-voltage stabilizing additive according to claim 1, characterized in that: x2 is 2 and y2 is 1.

3. The electrolyte high-voltage stabilizing additive according to claim 1 or 2, characterized in that: n is 2; and / or m is any integer between 0 and 2; preferably, m is 1 or 2.

4. The electrolyte high-voltage stabilizing additive according to any one of claims 1 to 3, characterized in that: x1 is 3 and y1 is 0.

5. A lithium ion battery electrolyte, characterized in that: The invention comprises an organic solvent, a lithium salt and the electrolyte high-voltage stabilizing additive according to any one of claims 1 to 4.

6. The lithium ion battery electrolyte according to claim 5, characterized in that: In the lithium-ion battery electrolyte, the concentration of the high-voltage stabilizing additive is 0.1-0.5M.

7. The lithium ion battery electrolyte according to claim 5, characterized in that: The organic solvent includes at least two or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and 1,3-dioxolane.

8. The lithium ion battery electrolyte according to claim 5, characterized in that: The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium tetrafluoroborate and lithium bis(oxalatoborate).

9. The lithium ion battery electrolyte according to claim 5, characterized in that: The lithium-ion battery electrolyte is composed of an organic solvent, a lithium salt and the electrolyte high-voltage stabilizing additive according to any one of claims 1 to 4; wherein the organic solvent is composed of ethylene carbonate and diethyl carbonate in a volume ratio of (0.8~1):(0.8~1), and the lithium salt is lithium hexafluorophosphate.

10. A lithium ion battery, characterized in that: The lithium battery electrolyte comprising any one of claims 5 to 9.

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